| 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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