| 1. |
- Samikannu, Rakesh, et al.
(författare)
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Lutidinium-Based Ionic Liquids for Efficient Dissolution of Cellulose
- 2019
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Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry. - 1144-0546 .- 1369-9261. ; 43:5, s. 2299-2306
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we have studied the potential of lutidinium-based ILs (1-allyl-3,5-dimethylpyridinium chloride [3,5-ADMPy]Cl and 1-allyl-3,4-dimethylpyridinium chloride [3,4-ADMPy]Cl) in the dissolution of cellulose, and their structures were confirmed by 1H and 13C NMR spectra, respectively. [3,5-ADMPy]Cl exhibited the highest capacity in cellulose dissolution. In fact, it dissolved 20 wt% of cellulose within 12 min and 26 wt% of cellulose in 35 min at 118 °C. The crystallinity and morphology of native and regenerated cellulose were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and CP/MAS 13C NMR spectroscopy. These techniques clearly suggest that the crystallinity of cellulose is reduced upon treatment in lutidinium-based ILs. The thermogravimetric analysis (TGA) showed that regenerated cellulose had thermal stability close to that of native cellulose.
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| 2. |
- Adeniyi, Omotayo, et al.
(författare)
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Engineering of layered iron vanadate nanostructure for electrocatalysis : simultaneous detection of methotrexate and folinic acid in blood serum
- 2023
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Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859.
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Tidskriftsartikel (refereegranskat)abstract
- In this study, nanostructure kazakhstanite-like iron vanadate (FexV3xOy.H2O) was synthesized and calcined at different temperatures (100-800 °C) in a nitrogen atmosphere. The material was used to modify screen-printed carbon electrodes to achieve an electrocatalytic effect on the surface. The relationship between calcination conditions and the catalytic performance of the electrode towards the oxidation of chemotherapeutic drugs, including methotrexate (MTX) and folinic acid (FA), was studied. Various spectroscopic, microscopic, and electrochemical methods were used to characterize the synthesized materials. The results show that calcination induces changes in the electronic structure, nanostructure morphology, electroactive surface area, and electrocatalytic performance of the material. Screen-printed carbon electrode modified with FexV3xOy calcinated at 450 °C (SPC/FexV3xOy-450) was used to develop a voltammetric sensor for the determination of MTX and FA in blood serum. The response of the SPC/FexV3xOy-450 towards the electrooxidation of MTX and FA was the highest in comparison to the bare SPC and SPC/FexV3xOy calcined at other temperatures. The SPC/FexV3xOy-450 exhibited a linear relationship over a wide concentration range: 0.005-200 µM for MTX and 0.05-200 µM for FA. The detection limit was 2.85 nM for MTX and 7.79 nM for FA. Compared to conventional methods, the SPC/FexV3xOy-450 sensor had a short response time (5 min) for simultaneous detection of MTX and FA without signal interferences from coexisting electroactive compounds. The accurate and precise determination of MTX in the presence of FA confirmed the potential clinical applications of SPC/FexV3xOy-450 for therapeutic drug monitoring during chemotherapy.
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| 3. |
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| 4. |
- Ahlkvist, Johan, et al.
(författare)
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One-pot catalytic conversion of Nordic pulp media into green platform chemicals
- 2013
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 454, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, both sulphite and sulphate (Kraft) cellulose from Nordic pulp mills were used as raw materials in the catalytic one-pot synthesis of green platform chemicals, levulinic and formic acids, respectively. The catalyst of choice was a macro-porous, cationic ion-exchange resin, Amberlyst 70. The optimal reaction conditions were determined and the influence of various gas atmospheres was investigated. The maximum yields of 53% formic acid and 57% of levulinic acid were separately obtained in a straight-forward conversion system only containing cellulose, water and the heterogeneous catalyst. The concept introduces a one-pot procedure providing a feasible route to green platform chemicals obtained via conversion of coniferous soft wood pulp to levulinic and formic acids, respectively.
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| 5. |
- Ahlkvist, Johan, et al.
(författare)
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Reaction Network upon One-pot Catalytic Conversion of Pulp
- 2013
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Konferensbidrag (refereegranskat)abstract
- Nordic sulphite and sulphate (Kraft) cellulose originating from Nordic pulp mills were used as raw materials in the catalytic synthesis of green platform chemicals, levulinic and formic acids, respectively. The catalyst of choice used in this study was a macro-porous, cationic ion-exchange resin Amberlyst 70 for which the optimal reaction conditions leading to best yields were determined. For this system, maximum yields of 53 mol-% and 57 mol-% were obtained for formic and levulinic acid, respectively. The reaction network of the various chemical species involved was investigated and a simple mechanistic approach involving first order reaction kinetics was developed. The prototype model was able to describe the behaviour of the system in a satisfactory manner.
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| 6. |
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| 7. |
- Ajaikumar, Samikannu, et al.
(författare)
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Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by DPU method
- 2011
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Ingår i: Applied Catalysis A. - Amsterdam : Elsevier. - 0926-860X .- 1873-3875. ; 392:1-2, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.
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| 8. |
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| 9. |
- Ajaikumar, Samikannu, et al.
(författare)
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Transesterification of diethyl malonate with n-butanol over HPWA/MCM-41 molecular sieves
- 2013
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Ingår i: Journal of porous materials. - Dordrecht : Springer. - 1380-2224 .- 1573-4854. ; 20:4, s. 951-959
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous Si-MCM-41 and Al-MCM-41 (Si/Al = 100) materials were synthesized via a hydrothermal method. Three different ratios (10, 20 and 30 wt%) of heteropoly tungstic acid (HPWA) was loaded on Si-MCM-41 by wet impregnation techniques. The characteristic structural features of the prepared materials were studied by various physico-chemical techniques such as X-ray diffraction (XRD), Nitrogen physisorption (BET), temperature programmed desorption of ammonia (TPD) and transmission electron microscopy (TEM). Transesterification of diethyl malonate (DEM) with n-butanol under autogeneous conditions in a temperature range from 50 to 125 °C was selected as the test reaction for the as synthesized materials. The reactants were fed with various mole ratios in order to determine the optimal feed composition leading to maximum yields of transesterified products. The results indicated that the conversion of diethylmalonate depends on the HPWA concentration on the support, temperature, reaction time and mole ratio of the reactants. Further, the catalytic efficiency of HPWA/MCM-41 was compared with that of Al-MCM-41. The solid acid HPWA/MCM-41 catalysts have several advantages in comparison to conventional mineral acid catalysts which are heterogeneous, eco-friendly, highly active and selective in the formation of transesters.
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| 10. |
- Bui, Thai Q., et al.
(författare)
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Mesoporous Melamine-Formaldehyde Resins as Efficient Heterogeneous Catalyst for Continuous Synthesis of Cyclic Carbonates from Epoxides and gaseous CO2
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:34, s. 12852-12869
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report the application of inexpensive mesoporous melamine-formaldehyde resins (MMFR and MMFR250) obtained by a novel template-free and organosolvent-free hydrothermal method as efficient heterogeneous catalysts for direct synthesis of cyclic carbonates from CO2 and epoxides (epichlorohydrin, butylene oxide and styrene oxide). The catalytic activity of the melamine resins was attributed to the abundant Lewis basic N-sites capable of activating CO2 molecules. Based on CO2-Temperature programmed desorption, the concentration of surface basic sites for MMFR and MMFR250 were estimated to be 172 and 56 µmol/g, while the activation energy of CO2 desorption (strength of basic sites) were calculated to be 92.1 and 64.5 kJ/mol. We also observed considerable differences in the catalytic activity and stability of polymeric catalysts in batch and in continuous-flow mode; due to the existence of a synergism between adsorption of CO2 and cyclic carbonates (poison). Our experiments also revealed important role of catalyst surface chemistry and CO2 partial pressure upon catalyst poisoning. Nevertheless, owing to their unique properties (large specific surface area, large mesoporous and CO2 basicity) melamine resins presented excellent activity (turnover frequency 207-2147 h-1), selectivity (>99%) for carbonation of epoxides with CO2 (20 bar initial CO2 or CO2:epoxide mole ratio ~1.5) under solvent-free and co-catalyst-free conditions at 100-120 oC. Most importantly, these low-cost polymeric catalysts were reusable and demonstrated exceptional stability in a flow reactor (tested upto 13 days time on stream, weight hourly space velocity 0.26-1.91 h-1) for continuous cyclic carbonate production from gaseous CO2 with different epoxides (conversion 76-100% and selectivity >99%) under industrially relevant conditions (120 oC, 13 bar, solvent-free/co-catalyst-free) confirming their superiority over the previously reported catalytic materials.
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| 11. |
- Bukhanko, Natalia, et al.
(författare)
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Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route
- 2013
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 1:8, s. 883-893
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of 1-ethyl chloride in the gas-phase mixture of ethanol and hydrochloric acid over ZnCl2/Al2O3 catalysts was studied in a continuous reactor using both commercial and tailor-made supports. The catalytic materials were characterized by the means of structural (XPS, TEM, XRD, and BET) and catalytic activity (selectivity and conversion) measurements. The reaction parameters such as temperature, pressure, and feedstock flow rates were optimized for the conversion of ethanol to ethyl chloride. The new tailor-made highly porous Al2O3-based catalyst outperformed its commercial counterpart by exhibiting high conversion and selectivity (98%) at the temperature of 325 °C. Long-term stability tests (240 h) confirmed the excellent durability of the tailor-made alumina catalysts. The process demonstrated here poses an efficient and economic “green” large-scale on-site synthesis of this industrially important reactant in industry, where bioethanol is produced and 1-ethyl chloride is necessary, e.g., for ethylation of cellulose and synthetic polymer products. On-site in situ production of ethyl chloride avoids the problems associated with the transportation and storage of toxic and flammable 1-ethyl chloride.
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| 12. |
- Bukhanko, Natalia, et al.
(författare)
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Gas phase synthesis of 'green' ethyl chloride
- 2012
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Konferensbidrag (refereegranskat)abstract
- Various xZnCl2/Al2O3 (x = 0-2 wt %) catalysts, and the effect of the type of alumina in the gas phase synthesis of ethyl chloride from ethyl alcohol and HCl were studied. The influence of temperature, pressure, and feed composition was investigated. The nature of catalytic material significantly influenced the performance of the system. The tailor-made high-porous Al2O3 was the optimal catalyst that showed high conversion and selectivity. At 325°C, the conversion obtained was 94-96% and selectivity remained at a constant level of 98% throughout the experiment. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference PRES (Prague, Czech Republic 8/25-29/2012).
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| 13. |
- Bukhanko, Natalia, et al.
(författare)
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Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina and flexible 3-D carbon foam supported catalysts
- 2017
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 542:25, s. 212-225
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Tidskriftsartikel (refereegranskat)abstract
- Isopropyl chloride synthesis from isopropanol and HCl in gas phase over ZnCl2 catalysts supported on Al2O3 as well as flexible carbon foam was studied in a continuous reactor. A series of catalytic materials were synthesised and characterised by BET, XPS, SEM, TEM, XRD and NH3-TPD methods. Catalytic activity tests (product selectivity and conversion of reactants) were performed for all materials and optimal reaction conditions (temperature and feedstock flow rates) were found. The results indicate that the highest yield of isopropyl chloride was obtained over 5 wt.% ZnCl2 on commercial Al2O3 (No. II) (95.3%). Determination of product mixture compositions and by-product identification were done using a GC-MS method. Carbon foam variant catalyst, 5 wt.% ZnCl2/C, was found to perform best out of the carbon-supported materials, achieving ∼75% yield of isopropyl chloride. The kinetic model describing the process in a continuous packed bed reactor was proposed and kinetic parameters were calculated. The activation energy for the formation of isopropyl chloride reaction directly from isopropanol and HCl was found to be ∼58 kJ/mol.
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| 14. |
- Bukhanko, Natalia, et al.
(författare)
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Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina catalysts
- 2014
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Ingår i: 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, PRES 2014. - : Czech Society of Chemical Engineering. - 9781510828131 ; , s. 72-73
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Konferensbidrag (refereegranskat)
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| 15. |
- Bukhanko, Natalia, et al.
(författare)
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Kinetic modeling of gas phase synthesis of ethyl chloride from ethanol and HCl in fixed bed reactor
- 2016
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 142, s. 310-317
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic modeling of gas-phase synthesis of ethyl chloride from ethanol and hydrochloric acid over high porous Al2O3 and 2 wt% ZnCl2/Al2O3 catalysts was studied in a continuous plug flow reactor in the temperature range of 200–325 °C. Two rival kinetic models were proposed that both describe the kinetics well. The kinetic parameters of the reaction were determined and activation energy values for ethyl chloride formation from ethyl alcohol and diethyl ether reactions were calculated.
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| 16. |
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Dehydroisomerization of α-pinene over metal supported Si-SBA-15 mesoporous molecular sieves
- 2013
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Proceedings (redaktörskap) (refereegranskat)abstract
- The effective dispersion of active metal species on mesoporous Si-SBA-15 is acquired by means of deposition-precipitation method. In order to achieve this, the surface of Si-SBA-15 was first modified with TiO2 via grafting method, followed by deposition-precipitation method (DP) to obtain a fine dispersion of metallic nanoparticles over TiO2 modified Si-SBA-15. The structural features of the synthesized materials were characterized by means of X-ray diffraction (XRD), nitrogen sorption (BET), XPS and HR-TEM. A valuable platform chemical, p-cymene, was produced over the prepared catalyst by dehydroisomerization of α-pinene under vapour-phase conditions. A stable catalyst for one-spot synthesis of renewable p-cymene from α-pinene was developed.
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| 17. |
- Durgadevi, Ganesan, et al.
(författare)
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Synthesis and characterization of CdS nanoparticle anchored Silica-Titania mixed Oxide mesoporous particles : Efficient photocatalyst for discoloration of textile effluent
- 2019
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Ingår i: International Journal of Nano Dimension. - : the Tonekabon branch of the Islamic Azad University. - 2008-8868 .- 2228-5059. ; 10:3, s. 272-280
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Tidskriftsartikel (refereegranskat)abstract
- An efficient photocatalyst consisting of CdS nanoparticle dispersed mesoporous silica-titania was prepared using amphiphilic triblock copolymer P123 as template and silica-titania sol-gel precursors. The CdS nanoparticle was incorporated into silica-titania mesoporous nanosturctures by post impregnation method. The synthesized catalyst has been characterized by FTIR, TEM, SEM, and EDAX analysis. The CdS nanoparticles incorporated silica-titania mesoporous particles exhibited an enhanced light harvesting, large surface area and excellent photocatalytic activity. Photocatalytic degradation experiments on methyleneblue solution at different pH of the medium revealed that, the catalyst ST0.5CdS0.2 is more effective in basic medium with a degradation efficiency of 98%. In addition, the catalyst is also tested for dye degradation against a raw textile dye effluent containing multiple dye molecules, and their results indicated that the raw effluent can be decolorized within 90min using ST0.5CdS0.2 catalyst.
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| 18. |
- Gemo, Nicola, et al.
(författare)
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Reactivity aspects of SBA15-based doped supported catalysts : H2O2 direct synthesis and disproportionation reactions
- 2013
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Ingår i: Topics in catalysis. - New York : Springer. - 1022-5528 .- 1572-9028. ; 56:9-10, s. 540-549
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Tidskriftsartikel (refereegranskat)abstract
- Pd and PdAu catalysts supported on SBA15 and SiO2 were prepared and investigated for H2O2 direct synthesis in a batch autoclave (10 °C and 17.5 bar) and in the absence of halides and acids. The SiO2 supported catalysts exhibited inferior performances compared to the mesoporous ordered SBA15. A good control of both the catalysts dispersion and nanoparticle stability was achieved using SBA15. Catalysts were doped with bromine, a promoter in the H2O2 direct synthesis. Productivity and selectivity decreased when bromine was incorporated in the catalysts, thus indicating a possible poisoning due to the grafting process. A synergetic effect between Pd and Au was observed both in presence and absence of bromopropylsilane grafting on the catalyst surface. Three modifiers of the SBA15 support (Al, CeO2 and Ti) were chosen to elucidate the influence of the surface properties on metal dispersion and catalytic performance. Higher productivity and selectivity were achieved incorporating Al into the SBA15 framework, whereas neither Ti nor CeO2 improved H2O2 yields. The enhanced performance observed for the Prau/Al–SBA15 catalysts was attributed to the increased number of Brønsted acid sites. A modification of this catalyst with bromine was confirmed to impair both productivity and selectivity, possibly due to the broader particle size distribution and the poor stability of the metal nanoparticles, as demonstrate by transmission electron microscopy (TEM) images. H2O2 disproportionation was also investigated. A much slower reaction rate was observed compared to the H2O2 production, suggesting that the major contributor in the process of H2O2 destruction must be connected to the hydrogenation reaction.
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| 19. |
- Gemo, Nicola, et al.
(författare)
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TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis : the influence of N and Au doping
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 6:105, s. 103311-103319
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Tidskriftsartikel (refereegranskat)abstract
- The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product.
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| 20. |
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| 21. |
- Golets, Mikhail, 1987-, et al.
(författare)
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A kinetic study of the liquid phase acetoxylation of α-pinene
- 2012
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Ingår i: Topics in catalysis. - : Springer. - 1022-5528 .- 1572-9028. ; 55:7-10, s. 649-656
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Tidskriftsartikel (refereegranskat)abstract
- The present study introduces kinetic modeling of liquid phase α-pinene acetoxylation with acetic acid over an ion-exchange resin catalyst. The reaction was carried out in a laboratory scale high-pressure autoclave. α-terpinyl (35 wt%) and bornyl (40 wt%) acetates were the primary products. The predominant reaction pathways were identified and evaluated.
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| 22. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Continuous production of the renewable ρ-cymene from α-pinene
- 2013
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 307, s. 305-315
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to demonstrate the feasibility to produce ρ-cymene, an important commodity chemical, in a continuous, one-pot reaction system from abundant α-pinene, available e.g. as a by-product of pulping industry. The isomerization reactions of α-pinene over bimetallic heterogeneous catalysts, 3 and 5 wt% Pd–Zn (1:1, 1:4, 4:1, 1:0, and 0:1), supported on Al-SBA15 were studied. The principal reaction products were identified as ρ- and m-cymenes, limonene, camphene, and ρ-menthene, respectively. The highest concentration of ρ-cymene reached 77 wt% under the optimized reaction conditions: 300 °C and α-pinene feed of 0.03 mL/min. Two main reaction pathways toward ρ- and m-cymenes were described, and a mechanistic kinetic model, based on a plausible reaction network in line with Langmuir–Hinshelwood approach, was developed. The catalyst characterization revealed the reduction in Pd(II) sites, catalyst coking, and decline of surface area over the course of time. The catalyst recovery and reuse was addressed.
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| 23. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Heterogeneously-catalyzed oxidation of p-cymene
- 2014
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Ingår i: 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, PRES 2014. - : Czech Society of Chemical Engineering. - 9781510828131 ; , s. 84-84
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Konferensbidrag (refereegranskat)
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| 24. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Liquid phase acetoxylation of α-pinene
- 2012
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Ingår i: NWBC 2012. - : VTT. - 9789513878801 - 9789513878818 ; , s. 339-341
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Konferensbidrag (refereegranskat)abstract
- Chemical pulping and bio-refining results in many fractions such as. tall oil and turpentine that contain substantial amounts of α-pinene and other terpenes. Today these fractions are usually burned in the recovery boilers. However, the northern forest industry, primarily utilizing the boreal forests, faces serious challenges from developing markets (South America, Asia), because of lower cost of raw material resources and labor. At the same time, there is a growing concern about emissions of greenhouse gases and security of supply connected to the use of fossil oil for transportation and as a feedstock for the chemical industry. The mentioned fact renders the substitution of petrochemical-related raw materials an important field of research.The flavor and fragrance industry is one of the main users of terpene esters. From those esters, α-terpinyl and bornyl acetates are produced from α-pinene and commonly used for bath products and perfumes. Due to the imperfection of conventional two-stage production method of the mentioned esters, which lays in the equipment corrosion, environmental pollution, large load and nonrecyclability of a catalyst, the novel one-stage catalytic process is always of high priority.The possibility of α-pinene liquid phase catalytic acetoxylation is introduced in the present study. The complex product distribution and reaction network analysis, influent reaction and catalytic factors optimization, combined with the reaction kinetic modeling were the main aims of research. The ion-exchange resin catalyst Amberlyst 70 was characterized as the catalyst used in the studied reaction and compared with the solvent-catalyzed mode. Valuable combinations of acetates were obtained for both studied modes. A wide range of process factors were studied in the batch (Parr) reactor used. The mentioned type of reactor is suitable for the consequent industrial operations scale-up calculations.
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| 25. |
- Golets, Mikhail, 1987-, et al.
(författare)
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Liquid phase acetoxylation of α-pinene over Amberlyst-70 ion-exchange resin
- 2012
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Ingår i: Applied Catalysis A: General. - : Elsevier BV. - 0926-860X .- 1873-3875. ; 435-436, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- Heterogeneously-catalyzed and solvent-catalyzed liquid phase acetoxylation of α-pinene with acetic acid acting as both a solvent and a reagent was studied. Both solvent-catalyzed and catalytic experiments were carried out and various reaction conditions were studied. The influence of temperature, pressure, solvent and gas milieu were taken into account. Bornyl, fenchyl, verbenyl as well as α-terpinyl acetates, limonene, camphene and γ-terpinene were found among reaction products. The addition of the catalyst allowed for maximization of the yield of bornyl acetate. The predominant products obtained were α-terpinyl, verbenyl and bornyl acetates. The reaction pathways were identified and evaluated. The aim of this work was to study the feasibility of batch acetoxylation of α-pinene. The analysis of the complex product distribution is not trivial and, consequently, resolving the reaction network was important. The optimized reaction conditions were searched for aiming at an efficient conversion of α-pinene to a mixture of valuable products.
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| 26. |
- Horáček, Jan, et al.
(författare)
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Studies on sodium lignosulfonate depolymerization over Al2O3 supported catalysts loaded with metals and metal oxides in a continuous flow reactor
- 2013
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Ingår i: Topics in catalysis. - New York : Springer. - 1022-5528 .- 1572-9028. ; 56:9-10, s. 794-799
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the how various heterogeneous catalysts perform upon lignosulfonate decomposition reactions. The main target of the study was to obtain extractable phenolic compounds as potential renewable chemicals for the production of fuel components and chemicals. The nature of the heterogeneous catalyst was found to have a great impact on the obtained product yields and the composition of the product mixture. Initially, a nickel–tungsten on alumina (NiW/Al2O3) reference catalyst was applied upon screening the influence of catalyst particle size and various reaction parameters. Significantly increasing product yields with decreasing catalyst particle size indicated that the lignosulfonate transformation takes place on the external catalyst surface due to large macromolecular structure of the feedstock. The contact time (space time velocity) and catalyst particle size were the most important factors influencing the selectivity profiles towards various products as well as the yields observed. The highest conversion to phenolics was obtained over in-house-prepared NiO/Al2O3 and NiMo/Al2O3 catalysts with various NiO and MoO3 loadings.
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| 27. |
- Jogi, Ramakrishna, et al.
(författare)
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Liquefaction of Lignocellulosic Biomass into Phenolic Monomers and Dimers Over Multifunctional Pd/Nbopo4 Catalyst
- 2022
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Ingår i: SSRN Electronic Journal. - : Elsevier BV. - 1556-5068.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- For the first time, a tandem catalytic material namely 5 wt. % Pd/NbOPO 4 was utilized in the depolymerization of wood in supercritical-ethanol under low initial-hydrogen pressure. The experiments were conducted under various experimental conditions, wood fractionation was executed with fresh, and acetone extracted birch. A comprehensive analysis was performed to elucidate the dissolution efficiency and achieved product distribution. The results indicated fresh birch, 34 wt. % of lignin monomer yield with 84 wt. % delignification efficiency were obtained while extracted wood, 35 wt. % of lignin monomer yield with 78 wt. % delignification efficiency was achieved. The total lignin monomer content extracted from the fresh birch is composed of 76.9 wt. % of dimethoxyphenols and 16.5 wt. % of monomers with the guaiacol structure. Among the dimethoxyphenols, major homosyringaldehyde (61.9 wt. %). Where extracted wood, 93.2 wt. % of dimethoxyphenols (63.6 wt. % homosyringaldehyde) and guaiacol-monomers (6.8 wt. %). It was concluded that the depolymerization occurred via breaking of the ether bonds in lignin, including ether hydrolysis by Lewis acid sites over the solid acid catalyst and with subsequent deoxygenation of monophenols over Pd. In addition, an extraction process was proposed to extract the aromatic fraction from the obtained biocrude.
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| 28. |
- Jogi, Ramakrishna, et al.
(författare)
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Liquefaction of lignocellulosic biomass into phenolic monomers and dimers over multifunctional Pd/NbOPO4 catalyst
- 2024
-
Ingår i: Renewable energy. - : Elsevier. - 0960-1481 .- 1879-0682.
-
Tidskriftsartikel (refereegranskat)abstract
- For the first time, a tandem catalytic material, 5 wt. % Pd/NbOPO4, was utilized in the depolymerization of wood in supercritical ethanol under hydrogen atmosphere. The experiments were conducted under various conditions, with fresh, and acetone extracted birch. A comprehensive analysis was performed to elucidate the dissolution efficiency and achieved product distribution. The results indicated that with fresh birch, 34 wt. % of lignin monomer yield with 84 wt. % delignification efficiency were obtained while with extracted wood, 35 wt. % of lignin monomer yield with 78 wt. % delignification efficiency were achieved. The total lignin monomer content extracted from the fresh birch is composed of 76.9 wt. % of dimethoxyphenols and 16.5 wt. % with the guaiacol structure. Major lignin monomer product was homosyringaldehyde (61.9 wt. %). With extracted wood, 93.2 wt. % of dimethoxyphenols (63.6 wt. % homosyringaldehyde) and 6.8 wt. % of guaiacol-monomers were achieved. It was concluded that the depolymerization occurred via breaking of the ether bonds in lignin, including ether hydrolysis by Lewis acid sites over the solid acid catalyst and with subsequent deoxygenation of monophenols over Pd. In addition, an extraction process was proposed to extract the aromatic fraction from the obtained biocrude.
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| 29. |
- Jogi, Ramakrishna, et al.
(författare)
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Understanding the formation of phenolic monomers during fractionation of birch wood under supercritical ethanol over iron based catalysts
- 2020
-
Ingår i: Journal of the Energy Institute. - : Elsevier. - 1743-9671 .- 1746-0220. ; 93:5, s. 2055-2062
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Tidskriftsartikel (refereegranskat)abstract
- The liquefaction of biomass in ethanol, at the critical point, has high potential due to low temperature and pressure (243 °C, 63 bar) when compared with water (374 °C, 220 bar). The current study deals with the fractionation of birch wood powder which was liquefied under supercritical ethanol over acidic or non-acidic catalysts, 5 wt % Fe-Beta-H-150 and 5 wt % Fe–SiO2, respectively. Based on the results, the reaction mechanism for the formation of lignin degradation products was proposed. The main phenolic product was isoeugenol over 5 wt % Fe-Beta-H-150 while intermediate products, i.e. such as coniferyl, and sinapyl alcohol, 4-propenyl syringol, syringaresinol, as well as syringyldehyde reacted rapidly further. The thermodynamic analysis was performed by Joback approach and using Gibbs-Helmholtz equation supporting the obtained results.
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| 30. |
- Kocík, Jaroslav, et al.
(författare)
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Screening of active solid catalysts for esterification of tall oil fatty acids with methanol
- 2017
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 155:1, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- The paper is focused on the description of the activity/selectivity of mesoporous silica based materials loaded with various types of active species in the esterification of tall oil free fatty acids. The metals such as aluminium, molybdenum, gallium and zinc, including their combinations were impregnated on the mesoporous silica, which was tested in esterification reaction. All these catalysts preserved its tall oil free fatty conversion in the first and the second catalytic cycles. However, while only insignificant amount of gallium or molybdenum was lost from the solid catalyst into the liquid phases, zinc leached from every studied solid catalyst. In contrast to impregnated gallium on mesoporous silica, which exhibited higher acidity and higher tall oil free fatty acids conversion in the first catalytic cycle, but its value was not preserved in the second catalytic test.
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| 31. |
- Konwar, Lakhya Jyoti, et al.
(författare)
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Efficient C-C coupling of bio-based furanics and carbonyl compounds to liquid hydrocarbon precursors over lignosulfonate derived acidic carbocatalysts
- 2018
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761. ; 8:9, s. 2449-2459
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates the catalytic potential of novel Na-lignosulfonate (LS) derived meso/macroporous solid protonic acids upon C–C coupling of bio-based furanics and carbonyl compounds. The materials demonstrated catalytic activity for solventless hydroxyalkylation/alkylation (HAA) of 2-methylfuran with furfural, acetone, butanal, cyclohexanone, levulinic acid and α-angelica lactone under mild reaction conditions (50–60 °C) producing branched-chain C12–C16 hydrocarbon precursors in yields approaching 96%. Moreover, the carbon materials exhibiting high total acidity (6–6.4 mmol g−1) outperformed sulfonic acid resins (Amberlyst®70, Amberlite®IR120 and LS resin), zeolites and liquid acids (p-toluenesulfonic acid, acetic acid and phenol). In fact, the most active carbocatalyst (60LS40PS350H+) exhibited the same turnover frequency as p-toluenesulfonic acid (186 h−1) upon furfural conversion but with an improved HAA product yield (up to 88%) and reusability, maintaining 98% of its original activity up to seven reaction cycles. The observed catalytic activity and operational stability of the LS derived acidic carbocatalysts were attributed to the strongly Brønsted acidic –SO3H groups covalently incorporated into their structural carbon framework and the promotional effects of hydrophilic surface functional groups (–COOH and –OH) favoring adsorption of oxygenated reactant molecules.
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| 32. |
- Konwar, Lakhya Jyoti, 1987-, et al.
(författare)
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Efficient hydrothermal deoxygenation of tall oil fatty acids into n-paraffinic hydrocarbons and alcohols in the presence of aqueous formic acid
- 2022
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Ingår i: Biomass Conversion and Biorefinery. - : Springer. - 2190-6815 .- 2190-6823. ; 12:1, s. 51-62
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal deoxygenation of tall oil fatty acids (TOFA) was investigated in the presence of aqueous formic acid (0.5–7.5 wt%) as a H2 donor in the presence of subcritical H2O pressure (569–599 K). Pd and Ru nanoparticles supported on carbon (5% Pd/CSigma, 5% Ru/CSigma, 10% Pd/CO850_DP, and 5% Ru/COPcomm_DP) were found to be efficient catalysts for deoxygenation of TOFA. The reaction pathway was mainly influenced by the concentration of formic acid and the catalyst. In case of Pd catalysts, in the presence of 0–2.5 wt% formic acid, decarboxylation was the dominant pathway producing n-paraffinic hydrocarbons with one less carbon atom (heptadecane yield up to 94 wt%), while with 5–7.5% formic acid, a hydrodeoxygenation/hydrogenation mechanism was favored producing C18 deoxygenation products octadecanol and octadecane as the main products (yields up to 70 wt%). In contrast, Ru catalysts produced a mixture of C5-C20 (n-and iso-paraffinic) hydrocarbons via decarboxylation, cracking and isomerization (up to 58 wt% C17 yield and total hydrocarbon yield up to 95 wt%) irrespective of formic acid concentration. Kinetic studies showed that the rates of deoxygenation displayed Arrhenius type behavior with apparent activation energies of 134.44 ± 31.36 kJ/mol and 148.92 ± 3.66 kJ/mol, for the 5% Pd/CSigma and 5% Ru/CSigma catalyst, respectively. Furthermore, the experiments with glycerol tristearate, rapeseed oil, sunflower oil, rapeseed biodiesel, and hydrolyzed rapeseed oil produced identical products confirming the versatility of the aforementioned catalytic systems for deoxygenation of C18 feedstocks.
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| 33. |
- Konwar, Lakhya Jyoti, et al.
(författare)
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Lignosulfonate-based macro/mesoporous solid protonic acids for acetalization of glycerol to bio-additives
- 2018
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Ingår i: Applied Catalysis B. - Amsterdam : Elsevier. - 0926-3373 .- 1873-3883. ; 220, s. 314-323
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Tidskriftsartikel (refereegranskat)abstract
- The enclosed paper introduces a novel, scalable and environmentally benign process for making strongly acidic solid meso/macroporous carbon catalysts from Na-lignosulfonate (LS), a byproduct from sulfite pulping. Ice-templated LS was converted to strongly acidic macro/mesoporous solid protonic acids via mild pyrolysis (350–450 °C) and ion/H+ exchanging technique. The synthesized materials were extensively characterized by FT-IR, Raman, XRD, XPS, TGA, FE-SEM, TEM and N2-physisorption methods. These LS derived materials exhibited a macro/mesoporous and highly functionalized heteroatom doped (O, S) carbon structure with large amounts of surface OH, COOH and SO3H groups similar to the sulfonated carbon materials. Further, these carbon materials showed excellent potential as solid acid catalysts upon acetalization of glycerol with various bio-based aldehydes and ketones (acetone, methyl levulinate and furfural), easily outperforming the commercial acid exchange resins (Amberlite® IR120 and Amberlyst® 70). Most importantly, the optimum LS catalyst exhibiting a large specific surface area demonstrated exceptional potential for continuous solketal production (liquid phase atmospheric pressure operation) maintaining its activity (glycerol conversion ≥ 91%) and structural features even after 90 h time on stream.
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| 34. |
- Leino, Ewelina, et al.
(författare)
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The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, ethanol and butylene oxide
- 2013
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 210, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were compared. The test reaction was synthesis of diethyl carbonate starting from carbon dioxide and ethanol using butylene oxide as the dehydrating agent.
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| 35. |
- Lin, Jhih-Fong, et al.
(författare)
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Trifluoroacetylazobenzene for optical and electrochemical detection of amines
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:8, s. 4687-4694
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we demonstrate the solution processing of optical and electrochemical dye sensors based on 4-(dioctylamino)-4'-(trifluoroacetyl) azobenzene and its application in sensing different amine compounds. Distinct optical response of the sensors exposed to ammonia, tetramethylammonium hydroxide, ethylamine, cadaverine and putrescine (typical compounds upon the decomposition of proteins) is observed. Incorporation of inkjet deposited thin films of the dye as sensors in food packages of ground meat and salmon is found as a feasible route to detect the appearance of biogenic amines produced by the degrading food products. Furthermore, we demonstrate an electrochemical amine sensor based on (trifluoroacetyl) azobenzene dye added in carbon nanotube-Nafion (R) composites. The electrochemical sensor exploits the reaction between the dye and amines to detect amines in electrolytes, while the carbon nanotubes provide large surface for adsorption and also provide a percolating electrical network for allowing efficient charge transfer at the electrode electrolyte interface.
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| 36. |
- Mani, Mariappan, et al.
(författare)
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Continuous hydrocyclization of aqueous levulinic acid to γ-valerolactone over bi-functional Ru/NbOPO4/SBA-15 catalyst under mild conditions
- 2022
-
Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 643
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we demonstrate that surface acid-base properties have marked effect upon the performance (activity, selectivity and stability) of supported Ru catalysts upon tandem hydrocyclization (hydrogenation-dehydration) of aqueous levulinic acid. A mesoporous bi-functional Ru/NbOPO4/SBA-15 catalyst incorporating highly dispersed Ru sites and well balanced strong Brønsted acidic sites (optimum B/L and M+S/W ratio) was identified, which outperformed the benchmark monofuncational (Ru/SBA-15, Ru/MCM-41) and physically blended bi-functional catalysts (Ru catalysts mixed with acid co-catalysts e.g. NbOPO4/Amberlyst-15). Further, the catalyst also demonstrated remarkable stability in a fixed-bed reactor, maintaining steady activity and γ-valerolactone selectivity (72-86%) during ca. 300 h time on stream (10 bar, 90-100 oC), corroborating its industrial potential. The exceptional performance and durability of the bi-functional catalyst was attributed to the presence of well dispersed hydrothermally and chemically stable acid (NbOPO4) and redox (Ru) sites.
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| 37. |
- Mariyaselvakumar, Mariyamuthu, et al.
(författare)
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Halogenated melamine formaldehyde polymers: Efficient, robust and cost-effective bifunctional catalysts for continuous production of cyclic carbonates via. CO2-epoxide cycloaddition
- 2024
-
Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 675
-
Tidskriftsartikel (refereegranskat)abstract
- Halogenated porous melamine polymers were demonstrated as an efficient catalyst for CO2-epoxide cycloaddition, selectively (>99%) producing C3-C12 cyclic carbonates in excellent yields (upto 99%) under solvent and co-catalyst free conditions. The halogenated polymers outperformed benchmark catalysts incorporating only basic (N-doped carbon, ZIF-8, N-rich melamine polymer) or nucleophilic (TBAB, KI) sites. The superior catalytic performance of these inexpensive polymers was attributed to their unique surface chemistry incorporating abundant, stable basic N sites (amine N and protonated N) and nucleophilic (Cl-, Br- or I-) that enabled simultaneous activation of both epoxide and CO2 molecule (supported by kinetic and DFT studies). Further, among halogenated polymers a Br- containing material (PMFBr) presented highest activity owing to its balanced CO2-philicity and strong nucleophilicity. Most importantly, PMFBr was robust, reusable and maintained stable performance for continuous production of C3-C4 cyclic carbonate (120 oC, 0.3-0.83 h-1 WHSVepoxide and 15 bar) in a fixed-bed reactor during 60-190 h TOS.
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| 38. |
- Mikkola, Jyri-Pekka, et al.
(författare)
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Conversion of alcohols to hydrocarbons using a dual catalyst system comprising basic oxide on mixed oxide or mesoporous carrier and etched metal loaded zeolite catalyst
- 2018
-
Patent (populärvet., debatt m.m.)abstract
- A method for converting an alcohol to hydrocarbons comprises two serially placed catalysts. The fraction of aromatics is reduced to desired levels. The method comprises: a) contacting the alcohol with a first catalyst on a carrier, said carrier is selected from a mixed oxide and a mesoporous carrier, said first catalyst comprises at least one basic oxide and optionally at least one selected from the group consisting of metals and metal oxides, then b) contacting the resulting mixture from step a) with a second catalyst wherein said second catalyst is an etched metal loaded zeolite catalyst wherein the etched metal loaded zeolite catalyst is manufactured with a method comprising etching with subsequent loading of metal onto the catalyst, wherein the metal is in the form of nanoparticles, and wherein at least two different metals are loaded onto the etched zeolite catalyst. The hydrocarbons are recovered and used for instance for fuel including gasoline, kerosene, diesel, and jet propellant, and jet fuel. Naturally, other uses of hydrocarbons should not be excluded.
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| 39. |
- Mikkola, Jyri-Pekka, et al.
(författare)
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Hydrothermal method for producing renewable paraffinichydrocarbons
- 2020
-
Patent (populärvet., debatt m.m.)abstract
- The present invention provides a method for producing hydrocarbons having 6 to 20 carbon atoms, comprising the steps of: a) providing a feedstock comprising saturated fatty acids, and/or derivatives thereof; b) deoxygenating the feedstock in the presence of a metal free hydrogenation and decarboxylation catalyst under low-pressure hydrothermal conditions, wherein the temperature is in the range 350-400 °C and the pressure is in the range 10-30 bar; and wherein the catalyst is a heteroatom-doped carbon material. Furthermore, there is provided a system for preforming the method in a single reactor (R) system comprises a bed of a carbon catalyst facilitating simultaneous hydrogenation and decarboxylation.
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| 40. |
- Mukesh, Chandrakant, et al.
(författare)
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Pore size-excluded low viscous porous liquids for CO2 sorption at room temperature and thermodynamic modeling study
- 2022
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Ingår i: Journal of Molecular Liquids. - : Elsevier. - 0167-7322 .- 1873-3166. ; 356
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we report porous ionic liquids (type-III) designed to utilize microporous ZIF-8 moieties with functional ionic liquids such as 8-(2-methoxyethyl)-1,8-Diazabicyclo[5.4.0]undec-7-en-8-ium, Bis(trifluoromethane)sulfonamide ([MEDBU][TFSI] and Trioctylammonium 4-para-tert-butylbenzoiate [TOAH][PTBBA]). The prepared materials were thoroughly characterized by means of XRD, FT-IR, SEM, TEM, BET, TGA, DSC and viscometry techniques. The idea of combining the intrinsic properties of ionic liquids with microporous architecture to prepare porous ionic liquids yields promising fluidic materials that have received attention in industrial applications such as gas sorption and separation etc. The prepared porous ionic liquids possess unique physico-chemical properties such as low viscosity, high thermal stability, low vapor pressure, reusability and their fluidic nature renders the materials suitable for CO2 capture. Herein introduced porous ionic liquids (ILs) showed enhanced CO2 uptake (0.92 mmol/g in [TOAH][PTBBA]-Z100 and 1.16 mmol/g in [MEDBU][TFSI]-Z200), or in other words, 15–47% higher sorption capacity compared to neat ionic liquids. This concept overcomes the drawbacks of highly viscous ILs and their limited CO2 sorption capacity. Thermodynamic modeling further demonstrated that the enthalpy of sorption is only −9.99 kJ mol−1, indicating that significantly less energy is required for regeneration. This is promising for the potential use of these fluidic materials in continuous separation processes on an industrial scale, as a better alternative to the existing hazardous amine scrubbing.
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| 41. |
- Ngoc Pham, Tung, et al.
(författare)
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Catalytic Hydrogenation of d-Xylose Over Ru Decorated Carbon Foam Catalyst in a SpinChem® Rotating Bed Reactor
- 2016
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Ingår i: Topics in catalysis. - New York : Springer. - 1022-5528 .- 1572-9028. ; 59:13-14, s. 1165-1177
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Tidskriftsartikel (refereegranskat)abstract
- In this work the activity of ruthenium decorated carbon foam (Ru/CF) catalyst was studied in three phase hydrogenation reaction of d-xylose to d-xylitol. The developed catalyst was characterized by using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectrometry and nitrogen adsorption–desorption measurement. Kinetic measurements were carried out in a laboratory scale pressurized reactor (Parr®) assisted by SpinChem® rotating bed reactor (SRBR), at pre-defined conditions (40–60 bar H2 and 100–120 °C). The study on the influence of reaction conditions showed that the conversion rate and selectivity of hydrogenation reaction of d-xylose was significantly affected by temperature. These results have been proved by a competitive kinetics model which was found to describe the behavior of the novel system (Ru/CF catalyst used together with the SRBR) very well. Besides, it was revealed that the catalytic activity as well as the stability of our Ru/CF-SRBR is comparable with the commercial ruthenium decorated carbon catalyst (Ru/AC) under identical reaction conditions. Moreover, all steps from catalyst preparation and catalyst recycling as well as catalytic testing can be performed in an easy, fast and elegant manner without any loss of materials. Briefly, the developed Ru/CF catalyst used together with the SRBR could be used an excellent alternative for the conventional Raney nickel catalyst in a slurry batch reactor and offers an attractive concept with obvious industrial applicability.
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| 42. |
- Ngoc Pham, Tung, et al.
(författare)
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Core–shell carbon nanofibers‐NiFe structure on 3D porous carbon foam : facilitating a promising trajectory toward decarbonizing energy production
- 2022
-
Ingår i: Advanced sustainable systems. - : Wiley-VCH Verlagsgesellschaft. - 2366-7486. ; 6:12
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a low-cost, light-weight, highly efficient, and durable electrode in which NiFe-layered double hydroxide is electrodeposited on a carbon nanofiber (CNF) core supported on a carbon foam (CF) is introduced. The resulting 3D NiFe-CNFs-CF electrode shows excellent oxygen evolution reaction and hydrogen evolution reaction performance in alkaline media. When used as an anode and a cathode in the same cell, a current density of 10 mA cm−2 is achieved, at a cell voltage of 1.65 V. Moreover, good stability over a long testing time (50 h) is demonstrated. The ternary hybrid electrode gives rise to an excellent performance-to-weight ratio owing to its very low bulk density (≈34 mg cm−3) inherited from super lightweight components composed of CF and CNFs. The developed electrode can potentially be used in large-scale alkaline water electrolysis, in facilities such as offshore hydrogen production platforms, which can complement the variable renewable energy production of wind farms through hydrogen storage and fuel cells.
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| 43. |
- Ngoc Pham, Tung, et al.
(författare)
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Industrially benign super-compressible piezoresistive carbon foams with predefined wetting properties : from environmental to electrical applications
- 2014
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 4
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work electrically conductive, flexible, lightweight carbon sponge materials derived from open-pore structure melamine foams are studied and explored. Hydrophobic and hydrophilic surface properties - depending on the chosen treatment conditions - allow the separation and storage of liquid chemical compounds. Activation of the carbonaceous structures substantially increases the specific surface area from ,4 m2 g21 to ,345 m2 g21 , while retaining the original three-dimensional, open-pore structure suitable for hosting, for example, Ni catalyst nanoparticles. In turn the structure is rendered suitable for hydrogenating acetone to 2-propanol and methyl isobutyl ketone as well for growing hierarchical carbon nanotube structures used as electric double-layer capacitor electrodes with specific capacitance of ,40 F/g. Mechanical stress-strain analysis indicates the materials are super-compressible (.70% volume reduction) and viscoelastic with excellent damping behavior (loss of 0.69 6 0.07), while piezoresistive measurements show very high gauge factors (from ,20 to 50) over a large range of deformations. The cost-effective, robust and scalable synthesis - in conjunction with their fascinating multifunctional utility - makes the demonstrated carbon foams remarkable competitors with other three-dimensional carbon materials typically based on pyrolyzed biopolymers or on covalently bonded graphene and carbon nanotube frameworks.
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| 44. |
- Ngoc Pham, Tung, et al.
(författare)
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NiCo Nanoneedles on 3D Carbon Nanotubes/Carbon Foam Electrode as an Efficient Bi-Functional Catalyst for Electro-Oxidation of Water and Methanol
- 2021
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Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we report a 3D structured carbon foam electrode assembled from a bi-functional NiCo catalyst, carbon nanotubes (CNT), and a monolith 3D structured carbon foam (CF) as a highly active and stable electrode for oxygen evolution reaction (OER) and methanol oxidation reaction (MOR). When the NiCo@CNTs/CF electrode was used as an anode in OER, after the anodization step, the electrode required a small overpotential of 320 mV to reach the current density of 10 mA cm−2 and demonstrated excellent stability over a long testing time (total 30 h) in 1 M KOH. The as-prepared NiCo@CNTs/CF electrode also exhibited a good performance towards methanol oxidation reaction (MOR) with high current density, 100 mA cm−2 at 0.6 V vs. Ag/AgCl, and good stability in 1 M KOH plus 0.5 M CH3OH electrolyte. The NiCo@CNTs/CF catalyst/electrode provides a potential for application as an anode in water electrolysis and direct methanol fuel cells.
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| 45. |
- Rautio, Anne-Riikka, et al.
(författare)
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Electric double-layer capacitors based on multiwalled carbon nanotubes : can nanostructuring of the nanotubes enhance performance?
- 2015
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 119:7, s. 3538-3544
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Tidskriftsartikel (refereegranskat)abstract
- Supercapacitors prepared from chemically modified and vacuum filtered buckypapers were studied. The aim was to evaluate how its pore structure impacts the specific capacitance, energy, and power density in different electrolytes. The specific capacitance varies in a linear fashion with the specific surface area for nanotubes modified by the means of catalytic, low-temperature partial catalytic oxidation using cobalt oxide nanoparticles decorating the nanotubes. In contrast, electrodes composed of nanotubes preactivated in CO2 demonstrated only a minor increase in their specific capacitance, despite the observed significant increase in specific surface area. The radically improved surface area was a result of emergence and deposition of soot on the nanotubes during the activation process, as revealed by transmission electron microscopy. Among six different types of electrode materials, the CoOx decorated materials proved to have the highest specific capacitance (similar to 25 F/g in aqueous KOH and similar to 15 F/g in triethylsulfonium bis(trifluoromethylsulfonyl)imide ionic liquid). Thus, highly structured carbon nanotubes giving rise to energy and power storage densities comparable with commercial and other multiwalled carbon nanotube based electric double-layer capacitor devices were obtained.
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| 46. |
- Samikannu, Ajaikumar, et al.
(författare)
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Effective dispersion of Au and Au-M (M = Co, Ni, Cu and Zn) bimetallic nanoparticles over TiO2 grafted SBA-15 : their catalytic activity on dehydroisomerization of α-pinene
- 2013
-
Ingår i: Microporous and Mesoporous Materials. - Amsterdam : Elsevier. - 1387-1811 .- 1873-3093. ; 173, s. 99-111
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Tidskriftsartikel (refereegranskat)abstract
- Mesostructured siliceous SBA-15 was synthesized via direct hydrothermal crystallization from acidic solution of poly-(ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol)-copolymer and tetraethyl orthosilicate. The amorphous surface of the calcined Si-SBA-15 was modified with 20wt.% of TiO2 by chemical grafting method using titanium isopropoxide as the titanium source in ethanol solution. Various metal nanoparticles Au, Au-M (M = Co, Ni, Cu and Zn) were supported on TiO2/SBA-15 by deposition-precipitation method (DP) using urea as the precipitating agent. The structural features of the synthesized materials were characterized by various physico-chemical techniques such as X-ray diffraction, nitrogen sorption, XPS and HR-TEM. BET results of Si-SBA-15 revealed the formation of mesoporous structure with an average pore size of 5.9nm, pore volume of 1.12 cm3/g and the specific surface area of 846 m2/g. HR-TEM results demonstrated that metal nanoparticles were highly dispersed over TiO2/SBA-15 and long range ordering of hexagonal mesopores of Si-SBA-15 was well retained after loading of 20 wt.% TiO2 and 3 wt.% of bimetallic nanoparticles. The catalytic performances of the prepared catalysts were studied on dehydroisomerization of α-pinene under gas phase conditions using hydrogen atmosphere. The stability and catalytic activity of Au-M-TiO2/SBA-15 (DP) catalysts upon conversion of α-pinene in to p-cymene was explored in comparison with the catalysts prepared by conventional method. AuNi-TiO2/SBA-15 catalysts prepared via DP method were found to be stable upon longer reaction time as well as superior in terms of conversion and selective towards the formation of p-cymene.
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| 47. |
- Samikannu, Ajaikumar, et al.
(författare)
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Highly dispersed NbOPO4/SBA-15 as a versatile acid catalyst upon production of renewable jet-fuel from bio-based furanics via hydroxyalkylation-alkylation (HAA) and hydrodeoxygenation (HDO) reactions
- 2020
-
Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 272
-
Tidskriftsartikel (refereegranskat)abstract
- Herein, we report the synthesis of a highly active and mesoporous Brønsted acidic NbOPO4/SBA-15 catalyst. The prepared catalysts were thoroughly characterized by means of analytical techniques such as XRD, FT-IR, XPS, NH3-TPD, SEM-EDS, TEM, TGA, 31P-MAS-NMR and N2-physisorption. The H3PO4 free deposition method was found to be effective for preserving the structure of Silica based carrier. In terms of catalytic performance, these materials demonstrated high activity upon C-C coupling of 2-methyl furan with carbonyl compounds and outperforming bulk NbOPO4, Nb2O5/SBA-15 and traditional solid acid catalysts (Al-MCM-41, Si/Al and H-ZSM-5). The NbOPO4/SBA-15 catalysts were stable and maintained high activity upon reuse and continuous operation (∼65 h). Furthermore, the Pd loaded counterparts (Pd/NbOPO4/SBA-15 and Pd/Nb2O5/SBA-15) also functioned as bifunctional catalysts and exhibited excellent activity upon subsequent hydrodeoxygenation of C-C coupling products. Most importantly, in terms of jet-fuel range hydrocarbons selectivity, these catalysts outperformed monofunctional Pd/carbon and aluminosilicate based bifunctional catalysts.
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| 48. |
- Samikannu, Ajaikumar, et al.
(författare)
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Renewable N-doped active carbons as efficient catalysts for direct synthesis of cyclic carbonates from epoxides and CO2
- 2019
-
Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 241, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- In the spirit of green chemistry and greenhouse gas mitigation, we explore herein the chemical utilization of CO2 upon synthesis of cyclic carbonates over N-doped activated carbons. The N-doped carbocatalysts were obtained from inexpensive N-rich bio-waste precursors and characterized by standard techniques (N2 physisorption, chemisorption, XPS, SEM, TEM, XRD, FT-IR and Micro-Raman spectroscopy). The materials exhibited excellent catalytic activity for direct carbonation of epoxides with CO2 to cyclic carbonates (yields upto 99%) under solvent free, moderate temperature (100–150 °C) and low CO2 pressure (5–50 bar) conditions. The observed catalytic activity of the N-doped carbocatalysts was attributed to the Lewis basic sites originating from pyridinic, pyridonic, and quaternary N-sites capable of activating the CO2 molecule. While control experiments with multiwalled carbon nanotubes (MWCNT) or commercial activated carbon, failed to produce cyclic carbonates due to lack of active (basic) sites. In terms of the catalytic performance, the N-doped carbocatalysts presenting a high porosity (634–1316 m2/g) and high levels of pyridinic (33%) and quaternary N-doping (30%), (i.e. CA500 and MA500), exhibited the highest activity and selectivity (TOF, conversion and cyclic carbonate yields upto 99% in 5–15 h). Most importantly, these materials demonstrated good operational stability and reusability.
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| 49. |
- Samikannu, Ajaikumar, et al.
(författare)
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The activation of C–O bonds in lignin Miscanthus over acidic heterogeneous catalysts: towards lignin depolymerisation to monomer units
- 2024
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Ingår i: Biomass Conversion and Biorefinery. - : Springer. - 2190-6815 .- 2190-6823. ; 14:8, s. 9723-9737
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Tidskriftsartikel (refereegranskat)abstract
- One-pot depolymerisation of lignin, extracted from Miscanthus plants under acidic (formic acid lignin, FAL) or basic (ammonia lignin, AL) conditions, over Ni- and/or Nb-doped SBA-15, was the subject of this study. The aforementioned acid catalysts prepared by sol–gel method were characterized by SEM–EDX, ATR-FTIR, Raman, XRD, N2 adsorption/desorption isotherms, CO2-TPD and NH3-TPD techniques. The increase in acidity due to the insertion of Nb into the SBA-15 structure promoted the selective cleavage of β–O–4 from ammonia lignin, leading to aromatic monomer yields up to 22 wt% in 6 h at 180 °C under 50 atm H2. The catalytic performances of Ni-Nb-SBA-15 as well as its stability were influenced by the chemical composition of the lignin sample as results of its extraction from the Miscanthus plant.
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| 50. |
- Verziu, Marian, et al.
(författare)
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Hydrogenolysis of lignin over Ru-based catalysts : the role of the ruthenium in a lignin fragmentation process
- 2018
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Ingår i: Molecular Catalysis. - : Elsevier. - 2468-8231. ; 450, s. 65-76
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic performances of two different classes of catalysts containing nickel or/and ruthenium as the active sites were studied in the depolymerisation of lignin isolated from Miscanthus × giganteus. The catalysts were prepared either by coprecipitation (ie, (RuNiMgAlO)x, (RuNiAlO)x, (NiAlO)x, (NiMgAlO)x) or by wet impregnation (ie, Ru/Al2O3) and characterized by nitrogen physisorption (BET), XRD, XPS, NH3-TPD, Raman and H2-TPR techniques. The experimental results indicate that the presence of ruthenium led to dimers as dominant products.
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