| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Kirilin, Alexey V., et al.
(författare)
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Aqueous-phase reforming of xylitol over Pt/C and Pt/TiC-CDC catalysts : catalyst characterization and catalytic performance
- 2014
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Ingår i: Catalysis Science & Technology. - : RSC Publishing. - 2044-4753. ; 4:2, s. 387-401
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous phase reforming (APR) of xylitol was studied over five Pt/C catalysts. The correlation between physico-chemical properties of the catalysts and catalytic performance was established. The Pt/C catalysts have different textural properties as well as different mean Pt cluster sizes and surface acidity. The average Pt cluster size was investigated by means of CO chemisorption as well as by TEM. The reaction was found to be structure sensitive and TOF linearly increases with increasing average Pt cluster size in the studied domain. The catalysts which possess higher surface acidity favoured higher rates of hydrocarbon production. On the contrary the Pt/C materials with lower acidities generated hydrogen with high selectivity and TOF.
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| 3. |
- Arve, Kalle, et al.
(författare)
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Did Chemisorption Become an Obsolete Method With Advent of Tem? Comparison of Mean Particle Size and Distribution of Silver on Alumina
- 2011
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Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 141:5, s. 665-669
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Tidskriftsartikel (refereegranskat)abstract
- Silver particle size and dispersion on a Ag/Al2O3 for HC-SCR were examined by means of chemisorption and TEM. Experimental results showed that determination of the accurate mean particle size (mps) is challenging and that the both applied methods have specific characteristics increasing the inaccuracy in the results which has to be taken into account in evaluation of catalytic activity. The results from TEM imaging were found to depend highly on the mode in which the surface was scanned (bright field versus dark field). Generally the point resolution was higher in dark field but the obtained mps did not increased along with the increasing silver loading. The main limitation with the O-2-chemisorption was related to the choice of the stoichiometric factor between the adsorbent and silver atoms. However, together these techniques support each other and help to give a more realistic picture of the mean silver particle size, distribution and indications of the oxidation states on the alumina support.
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| 4. |
- Behravesh, Erfan, et al.
(författare)
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Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol : Influence of solution pH, Au nanoparticle size, support structure and acidity
- 2017
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 353, s. 223-238
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Tidskriftsartikel (refereegranskat)abstract
- Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.
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| 5. |
- Bernas, Andreas, et al.
(författare)
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Catalytic transformation of abietic acid to hydrocarbons
- 2012
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Ingår i: Topics in catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 55:7-10, s. 673-679
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic and thermal conversion of abietic acid was investigated in a laboratory scale high-pressure autoclave. Fractionation of crude tall oil produces rosin acids of which abietic acid is the main compound. Tall oil rosin acid, a forest product industry residue, is an abundant, inexpensive and chemically desirable feedstock for production of lighter hydrocarbons that can be used as diesel fuel additives. The carboxylic acid functionality of the main reactant, abietic acid, must first be removed, followed by double bond hydrogenation of the remaining aromatic rings. In this study, a number of catalytic and non-catalytic reaction steps in the conversion of abietic acid were investigated. The aim was to study hydrogenation and decarboxylation reactions of abietic acid in order to produce lighter hydrocarbons. The experiments were performed by using toluene as a solvent as well as with neat abietic acid, in the absence of any solvent. Hydrogenation of abietic acid to tetrahydroabietic acid in toluene was successfully performed over palladium on carbon catalyst at the temperature range of 100-200 A degrees C and at 30 bar hydrogen pressure. Thermal non-catalytic decarboxylation of abietic acid in toluene takes place at 200-300 A degrees C resulting in one main product. The hydrocarbon products were further hydrogenated under hydrogen pressure. Catalytic decarboxylation of abietic acid in toluene was achieved over 5 wt% Ru/C, giving a wider product distribution than thermal decarboxylation.
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| 6. |
- Birgersson, Henrik, et al.
(författare)
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An investigation of a new regeneration method of commercial aged three-way catalysts
- 2006
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 65, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- The ability to modify aged three-way catalysts (TWC) by regaining part of the fresh catalyst surface structure has been verified by both bulk and surface-sensitive characterisation techniques. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM/EDX) techniques were applied to fully evaluate the efficiency of a regeneration procedure of commercial three-way catalysts targeting the washcoat surface. The regeneration comprised combined thermal and liquid chlorine treatments. Structural changes of the washcoat were further investigated with nitrogen adsorption-desorption (BET) and Laser Ablation methods. The investigation showed that the regeneration treatments resulted in an enrichment of the washcoat surface with palladium, thereby increasing the number of catalytically active surface sites. Furthermore, the observed removal of phosphorous and sulphur contaminants resulted in an increase of the relative amount of small pores between 1 and 10 nm and washcoat surface area. An increased catalytic activity regarding CO, NOx, and HC emissions was observed after regeneration. providing proof of the proposed concept.
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| 7. |
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| 8. |
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| 9. |
- Eta, Valerie, et al.
(författare)
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Synthesis of dimethyl carbonate from methanol and carbon dioxide : Circumventing thermodynamic limitations
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9609-17
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dimethyl carbonate from methanol and CO2 catalyzed by ZrO2 doped with KCl was investigated using chemical traps for water to circumvent thermodynamic limitations. The reaction, promoted by magnesium, occurred via the formation of carbonated magnesium methoxide (CMM) which adsorbed on the surface of ZrO2. The surface migration of the oxygen atom of ZrO2 to the surface methoxy groups of CMM resulted in the formation of dimethyl carbonate. The resulting MgO then reacted with methanol forming water and regenerating magnesium methoxide. The water formed reacted with the dehydrating agent, thus shifting the equilibrium toward a higher yield of DMC. The yield of 7.2 mol % DMC and 13.6 mol % conversion of methanol was obtained when methanol reacted with CO2 at 150 °C and 9.5 MPa for 8 h. The plausible reaction pathway is described.
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| 10. |
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| 11. |
- Eta, Valerie, et al.
(författare)
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The Effect of Alkoxide Ionic Liquids on the Synthesis of Dimethyl Carbonate from CO2 and Methanol over ZrO2-MgO
- 2011
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Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1011-372X .- 1572-879X. ; 141:9, s. 1254-1261
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Tidskriftsartikel (refereegranskat)abstract
- The use of carbon dioxide in the synthesis of chemicals, such as dimethyl carbonate (DMC), constitutes an environmentally attractive alternative to hazardous and toxic reagents. However, the direct synthesis of DMC from methanol and CO2 is characterized by low yields due to the reaction equilibrium and the thermodynamic limitations (Delta G(298K)(0) = + 26.3 kj/mol). Alkoxide ionic liquids possessing alkylimidazolium and benzalkonium cations were prepared, characterised and tested together with ZrO2-MgO catalyst for the synthesis of DMC from methanol and CO2. By using the novel ionic liquid as additives, ca. 12% conversion of methanol, and 90% selectivity to DMC was obtained at 120 A degrees C and 7.5 MPa. The water abstracting potential of the ionic liquids influenced the conversion of methanol and the selectivity to DMC. The alkoxide ionic liquids were recovered and reused in DMC synthesis without loss in activity and selectivity.
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| 12. |
- Grénman, Henrik, et al.
(författare)
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Modeling the influence of wood anisotropy and internal diffusion on delignification kinetics
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9703-11
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Tidskriftsartikel (refereegranskat)abstract
- A general mathematical model for the chemical pulping of wood including coupled chemical reactions and diffusion limitations in anisotropic wood chips was developed. The model, which consists of coupled parabolic partial differential equations (PDEs) and ordinary differential equations (ODEs), describes the time-dependent behavior of wood chips as they are exposed to chemicals in the liquid phase. In addition to the reaction−diffusion phenomena, the model describes the change of the wood chip porosity during the process. A numerical algorithm that combines spatial discretization by finite differences with a stiff ODE solver based on the backward difference method was used as an efficient strategy to solve the mass balances of wood chips in batch reactors. Numerical simulations with the software can be used to predict the progress of industrial delignification, that is, production of primarily cellulose through chemical pulping. The effect of the reaction parameters, such as the temperature and the concentrations of the alkaline delignification chemicals, as well as the sizes of the wood chips, can be evaluated with the model, the final goal being the intensification of the chemical pulping process. The model can be used to describe both the current kraft pulping (sulfate pulping) technique, as well as other processes, such as sulfite pulping and pulping in nonaqueous solvents.
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| 13. |
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| 14. |
- Hajek, Jan, et al.
(författare)
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Interconversion of Lactose to Lactulose in Alkaline Environment : Comparison of Different Catalysis Concepts
- 2013
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Ingår i: Topics in catalysis. - : Springer/Plenum Publishers. - 1022-5528 .- 1572-9028. ; 56:9-10, s. 839-845
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Tidskriftsartikel (refereegranskat)abstract
- Interconversion of lactulose to lactulose with the aim to determine and optimize the yield of ketose was carried out. Various homogenous and heterogeneous alkaline catalysts were applied (NaOH, MgO, hydrotalcite etc.). The selectivity and activity of the catalysts were compared. The results gave insight to the performance differences among the screened catalysts under the various reaction conditions. From the activity performance point of view, the conversion was limited by the formation of acidic end-products. In general, the selectivity decreased with conversion and the conversion-selectivity pattern was independent of the catalyst.
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| 15. |
- Hajek, J., et al.
(författare)
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Processing of gluconic acid derivatives to value added monosaccharides via oxidative degradation
- 2012
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Konferensbidrag (refereegranskat)abstract
- One of the components that can be efficiently obtained, e.g., via fermentation of polysaccharide containing waste or biomass, is glucose and some of its derivatives. Degradation of C6 carbohydrates yields corresponding C5 sugars. In case of gluconic acid, the product is arabinose. The reaction, illustrating a valuable synthetic route, e.g., for the abatement of waste streams containing gluconic acid is shown. In spite of high yields, the reaction is characterized by complex analytics due to the presence of organic as well as inorganic by-products. Under optimized conditions, yields between 70-80% could be achieved. 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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| 16. |
- Hara, Piia, et al.
(författare)
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Supported ionic liquids in Burkholderia cepacia lipase-catalyzed asymmetric acylation
- 2010
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier. - 1381-1177 .- 1873-3158. ; 67:1-2, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- Lipase PS from Burkholderia cepacia was successfully immobilized on Kynol™ ACC 507-15 active carbon cloth with and without ionic liquids as SILE catalysts. Activity, enantioselectivity and reuse of the catalysts were evaluated in the acylation of 1-phenylethanol with vinyl acetate in toluene and in hexane over the temperature range 25 - 60 °C. The presence of [EMIM][NTf2] clearly stabilized the enzyme against inactivation and preserved enantioselectivity in reuse in a process which is affected by the nature of the IL, solvent and substrate structure.
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| 17. |
- Hernandez Carucci, José R, et al.
(författare)
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Preparation and characterization of coated microchannels for the selective catalytic reduction of NOx
- 2012
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Ingår i: Focus on Catalysis Research. - New York : Nova Science Publishers. - 9781621004776 ; , s. 209-236
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Bokkapitel (refereegranskat)abstract
- Shallow microchannels (Ø= 460 m) were successfully coated with different catalytically active phases, e.g., Cu-ZSM-5, Cu/(ZSM-5+Al2O3), Au/Al2O3, Ag/(Al2O3+Ionic liquid) and Ag/Al2O3, and tested on the hydrocarbon-assisted selective catalytic reduction of NOx (HC-SCR) with different model bio-derived fuels, i.e., methyl- and ethyl laurate produced by transesterification and hexadecane, a paraffinic component that can be produced by decarboxylation and/or decarbonylation of natural oils and fats. Characterization of the washcoats was done by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDXA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), showing a dependence of the metal loading with the impregnation time and the precursor concentration. The Ag/Al2O3 catalysts exhibited, in general, the highest activities towards the NOx reduction. Optima in impregnation time and concentration of AgNO3 solution displaying the highest activity in HC-SCR among the prepared Ag/Al2O3 washcoats were established. A combination of Cu-ZSM-5 or Cu/(ZSM-5+Al2O3) and the optimum Ag/Al2O3 catalyst were tested in order to improve the low temperature reduction in SCR with hexadecane as a reducing agent. The enhancement of the activity at low temperatures (< 350 °C) was up to seven-fold compared to the case when only Ag/alumina was used. The effect of the hydrocarbon concentration (hexadecane) and the presence of water in the feed were also investigated.
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| 18. |
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| 19. |
- Hyvärinen, Sari, et al.
(författare)
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Ionic liquid fractionation of woody biomass for fermentable monosaccharides
- 2011
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Ingår i: Cellulose Chemistry and Technology. - : Cellulose Chemistry and Technology. - 0576-9787. ; 45:7-8, s. 483-486
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the present study, devoted to wood fractionation, was to obtain monosaccharides, hexoses and pentoses by means of an ionic liquid (IL) based pre-treatment procedure. Softwood sawdust (maximum particle size of 2 mm) of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were exposed to ionic liquids – 1-ethyl-3-methylimidazolium acetate (C2mimAce) and 1-ethyl-3-methylimidazolium chloride (C2mimCl) – and thermal treatment (80-150 °C), for various time intervals (0-72 h). Furthermore, cellulose of various origins (plants, wood pulps) was dissolved in C2mimAce and 1-butyl-3-methylimidazolium chloride (C4 mimCl) for the study of the dissolved fractions, stress being laid on monosaccharides and possible by-products, 5-hydroxymethylfurfural and furfural. Knowing the challenges in analysis techniques when ILs and sugars are involved, the present work focuses on the development of suitable analysis methods. To this end, a Hewlett Packard 1100 series HPLC equipped with a refractive index (RI), detector model HP1047 A and a diode array UV detector (DAD) fitted with a carbohydrate column HPX-87K was utilized. Challenges and improvements are discussed.
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| 20. |
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| 21. |
- Hyvärinena, S., et al.
(författare)
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Sugars and sugar derivatives in ionic liquid media obtained from lignocellulosic biomass : comparison of capillary electrophoresis and chromatographic analysis
- 2014
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 223, s. 18-24
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Tidskriftsartikel (refereegranskat)abstract
- Processing of woody lignocellulosic biomass, under heating in combination with ionic liquids (ILs) was studied in order to obtain simple (fermentable) sugars. Due to the new environmental challenges, finding greener ways to produce platform chemicals and/or bio-fuels has become a popular research area. Various industrial, pilot or laboratory scale technologies for the depolymerization or fractionation of lignocellulosic polysaccharides to monomers are known. One of the new, interesting, methods is to utilize ILs in biomass pre-treatment procedures with an aim to bypass other pre-treatment methods. Furthermore, in order even to initiate studies whether ILs can contribute to catalytic depolymerization, there has to be a robust way to analyze the IL-treated lignocellulosics. This is a major issue since woody samples that contain any salts such as ILs can indeed be quite challenging from the analytic point of view. The applied capillary electrophoresis was found to be an excellent analytical method providing substantial improvements compared to the earlier used chromatographic methods.In this work it was demonstrated that application of ILs, at elevated temperatures, contributes to hydrolysis and depolymerization of lignocellulose. The effect is time and temperature dependent: in harsh conditions sugars degrade but too low processing temperatures or short treatment times result in no meaningful effect. The formation of the degradation products of the monosaccharides is a good indicator of the harshness of the applied chemical conditions. Evidently, furfural and 5-(hydroxymethyl)furfural formed in rather short treatment times.
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| 22. |
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| 23. |
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| 24. |
- Kannisto, Hannes, 1979, et al.
(författare)
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On the performance of Ag/Al2O3 as a HC-SCR catalyst – influence of silver loading, morphology and nature of the reductant
- 2013
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Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 3:3, s. 644-653
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the performance of Ag/Al2O3 catalysts for hydrocarbon selective catalytic reduction (HC-SCR) of NOx under lean conditions, using complex hydrocarbons as reductants. The aim is to elucidate the correlation towards the silver loading and morphology, with respect to the nature of the reductant. Ag/Al2O3 samples with either 2 or 6 wt% silver loading were prepared, using a sol–gel method including freeze-drying. The catalytic performance of the samples was evaluated by flow reactor experiments, with paraffins, olefins and aromatics of different nature as reductants. The physiochemical properties of the samples were characterized by scanning electron microscopy/energy dispersive X-ray spectroscopy, scanning transmission electron microscopy/high angle annular dark field imaging, X-ray photoelectron spectroscopy and N2-physisorption. The 2 wt% Ag/Al2O3 sample was found to be the most active catalyst in terms of NOx reduction. However, the results from the activity studies revealed that the decisive factorfor high activity at low temperatures is not only connected to the silver loading per se. There is also a strong correlation between the silver loading and morphology (i.e. the ratio between low- and high- coordinated silver atoms) and the nature of the hydrocarbon, on the activity for NOx reduction. Calculated reaction rates over the low-coordinated step and high- coordinated terrace sites showed that the morphology of silver has a significant role in the HC-SCR reaction.For applications which include complex hydrocarbons as reductants (e.g. diesel), these issues need to be considered when designing highly active catalysts.
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| 25. |
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| 26. |
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| 27. |
- Kirilin, A, et al.
(författare)
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Chemo-Bio Catalyzed Synthesis of R-1-Phenylethyl Acetate over Bimetallic PdZn Catalysts, Lipase, and Ru/Al2O3 : part II
- 2011
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Ingår i: Kinetics and catalysis. - : Maik Nauka/Interperiodica. - 0023-1584 .- 1608-3210. ; 52:1, s. 77-81
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Tidskriftsartikel (refereegranskat)abstract
- One-pot synthesis of R-1-phenyethylacetate at 70 degrees C was investigated using three different catalysts simultaneously, namely a bimetallic PdZn/Al2O3 as a hydrogenation catalyst, an immobilized lipase as an acylation catalyst and Ru/Al2O3 as a racemization catalyst. The most active bimetallic catalyst was PdZn/Al2O3 calcined at 300 degrees C and reduced at 400 degrees C, whereas the most selective although less active catalyst was the one being calcined and reduced at 500 degrees C. The highest selectivity to R-1-phenylethyl acetate over this catalyst was 32 at 48% conversion. Ru/Al2O3 was confirmed to have a positive effect on the formation of the desired product, although it was not very active in the racemization during one-pot synthesis.
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| 28. |
- Kirilin, A, et al.
(författare)
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Chemo-bio catalyzed synthesis of R-1-phenylethyl acetateover bimetallic PdZn catalysts, lipase and Ru/Al2o3. Part I
- 2011
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Ingår i: Kinetics and catalysis. - Moskva : Nauka. - 0023-1584 .- 1608-3210. ; 52:1, s. 78-82
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Tidskriftsartikel (refereegranskat)abstract
- The effect of calcination and reduction temperature on the physical properties of PdZn/Al2O3 catalysts, prepared by coprecipitation deposition technique and characterized by XPS, XRD and TEM methods are reported. The temperatures were varied in a range of 300–500°C. The catalyst calcined at 300°C and reducedat 400°C exhibited the metal particle size of 2–6 nm and contained the highest surface concentrations of Pd and Zn according to XPS measurements. The size and the fraction of large particles (above 10 nm) increased with increasing the calcinations and reduction temperatures.
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| 29. |
- Kirilin, A, et al.
(författare)
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Mechanistic investigations of the reaction network in chemobiocatalyzed synthesis of R1Phenylethyl Acetate
- 2010
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Ingår i: Kinetics and catalysis. - : Springer. - 0023-1584 .- 1608-3210. ; 51:6, s. 809-815
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics and reaction network of the onepot synthesis of R1phenylethyl acetate was investigated at 70°C in toluene over a combination of three different catalysts: PdZn/Al2O3 as a catalyst for acetophenone hydrogenation, lipase as an enzymatic catalyst for R1phenylethanol acylation with ethyl acetate and Ru/Al2O3 as a racemization catalyst for S1phenylethanol. In addition to the desired reactions, other reactions, namely hydrogenolysis and dehydration of (R, S)1phenylethanol and debenzylation of (R, S)1phenylethyl acetate also occurred. The kinetic results revealed that ethylbenzene formation was enhancedwith higher amounts of PdZn/Al2O3, whereas lipase did not catalyze ethylbenzene formation. Furthermore, ethylbenzene was formed in the hydrogenolysis of (R, S)phenylethanol and in the debenzylation of (R, S)1phenylethylacetate over Pd/Al2O3 catalyst. The presence of Ru/Al2O3 catalyst, in which Ru was in the oxidation state of 3+, enhanced the formation of R1phenylethyl acetate, although no clear racemization of S1phenylethanol during the onepot synthesis of R1phenylethyl acetate was observed. Dynamic kinetic resolution of (R, S)1phenylethanol in toluene, was, however, demonstrated over Ru/Al2O3 and lipase.
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| 30. |
- Kirilin, Alexey V, et al.
(författare)
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Aqueous phase reforming of xylitol and sorbitol : comparison and influence of substrate structure
- 2012
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 435-436, s. 172-180
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of abundant polyol stemming from hemicelluloses, xylitol, was investigated in the aqueous phase reforming (APR) over supported Pt/Al2O3. The data obtained in the case of xylitol was compared to aqueous phase reforming of sorbitol under the same operating conditions. The effect of weight hour space velocity on the performance of a catalytic system as well as on selectivity towards hydrogen and alkanes was studied. The catalyst showed stable performance with insignificant deactivation over 160 hours time-on-stream. The selectivity towards H2 diminished from 86 to 70% within 120 hours. The regeneration of the catalytic system in a H2 flow allowed to recover the catalyst activity and to improve selectivity towards H2 to 75%. It was found that both polyols demonstrated similar behavior in the APR in the whole range of space velocities studied. The selectivity towards H2 went through a maximum in the case of xylitol and sorbitol when changing a space velocity. This behavior was attributed to a number of side reactions which involved hydrogen thus leading to its consumption. Additionally, the yields of target APR product, hydrogen, were higher in the case of xylitol compared to sorbitol due to the longer carbon chain in the latter substrate. The plausible reaction network based on the hypothesis that APR process proceeds through the terminal position of polyol was proposed to explain similarity in the gas and liquid product composition in the APR of xylitol and sorbitol. The reaction scheme describing formation of the main gas and liquid products via various pathways was proposed and discussed. The results obtained and explanations provided are in perfect coincidence with the results obtained for different substrates in the literature.
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| 31. |
- Kirilin, Alexey V., et al.
(författare)
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Aqueous phase reforming of xylitol over Pt-Re bimetallic catalyst : Effect of the Re addition
- 2014
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 223, s. 97-107
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous phase reforming (APR) of xylitol was studied in a continuous fixed bed reactor over three catalysts: Pt/Al2O3, Pt/TiO2 and Pt-Re/TiO2. The data obtained in the case of the monometallic Pt catalysts was compared to the bimetallic Pt-Re sample. The effect of Re addition on the catalyst stability, activity, product formation and selectivity toward hydrogen and alkanes was studied. The bimetallic catalyst demonstrated a higher selectivity to alkanes compared to the monometallic samples. The monometallic catalyst was more selective toward hydrogen formation. A plausible reaction scheme explaining differences in selectivity toward hydrogen and alkanes was proposed and discussed.
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| 32. |
- Kirilin, Alexey V, et al.
(författare)
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Reaction products and transformations of intermediates in the aqueous-phase reforming of sorbitol
- 2010
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Ingår i: ChemSusChem. - Weinheim : WILEY-VCH Verlag GmbH & Co. KGaA. - 1864-564X .- 1864-5631. ; 3:6, s. 708-718
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous phase reforming of sorbitol over Pt supported on an alumina catalyst is investigated, in order to identify the intermediates involved in the transformation of the initial feed. Parameters such as the sorbitol feed rate and temperature are studied. To identify the intermediates, an approach based on analysis of the gas and liquid phases as well as the total carbon content was developed. According to analysis by gas chromatography combined with mass spectrometry of volatile substances collected with solid-phase microextraction, over 260 compounds are involved in the transformation of sorbitol. Of these, 50 of the major products are identified with high reliability. It is shown that a great variety of compounds, bearing different functionalities, form part of the reaction network. The formation of the majority of identified compounds is explained and a reaction network for the formation of sorbitol and intermediate molecules transformation is proposed.
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| 33. |
- Kontturi, V, et al.
(författare)
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Simultaneous detection of absorption spectrum and refractive index ratio with a spectrophotometer : monitoring contaminants in bioethanol
- 2011
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 22:5, s. 6-
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Tidskriftsartikel (refereegranskat)abstract
- The optical properties of a biofuel resulting from the fungi-treated lignocellulosic biomass in an ethanol matrix were studied. The matrix simulates the case that the bioethanol is contaminated by sugars, water and colour pigments that reduce the quality of the biofuel and compromise the combustion process. It is suggested that by applying a spectrophotometer only, it is possible to obtain valid information, i.e. the spectral features of the contaminants as well as the refractive index ratio of bioethanol. This allows for simultaneous purity and density detection of biomass-derived liquids or liquid biofuels, in comparison to a reference representing an ideal bioethanol (pure ethyl alcohol, ethanol of 99.5% purity (v/v)).
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| 34. |
- Kumar, Narendra, et al.
(författare)
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Synthesis and characterization of solid base mesoporous and microporous catalysts: Influence of the support, structure and type of base metal
- 2012
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 152, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of solid base Ce–H-MCM-41, Ce–Si-MCM-41, Cs-MCM-41, K-MCM-41 mesoporous materials and Na-ZSM-12, Cs-ZSM-12 microporous zeolites were carried out by means of evaporation impregnation and ion-exchange methods. The solid basecatalysts were characterized using X-ray powder diffraction, scanning electron microscope, nitrogen adsorption, FTIR of pyridine and temperature programmed desorption of CO2. The H-ZSM-12, Cs-ZSM-12 zeolite, H-MCM-41, Ce–H-MCM-41 and Ce–Si-MCM-41 mesoporous catalysts were studied for the synthesis of diethyl carbonate starting from ethanol and carbon dioxide, using butylene oxide as the dehydrating agent. Catalyst testing for the synthesis of diethyl carbonate was carried out at 170 °C and 4.5 MPa of initial CO2 pressure. 16 wt.% Ce–H-MCM-41 mesoporous material exhibited higher amount of weak, medium and strong basic sites than that of 32 wt.% Ce–Si-MCM-41. The presence of weak and strong basic sites was observed in the microporous 2 wt.% Cs-ZSM-12 catalyst. Diethyl carbonate formation was observed over Ce–H-MCM-41 and Ce–Si-MCM-41 mesoporous materials. Amount of basic sites and its strength influenced the synthesis of diethyl carbonate over the mesoporous materials.
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| 35. |
- Kusema, Bright T, et al.
(författare)
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Kinetics of L-arabinose oxidation over supported gold catalysts with in situ catalyst electrical potential measurements
- 2012
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753. ; 2, s. 423-431
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of L-arabinose selective oxidation over Au/Al2O3 catalysts was studied with simultaneous in situ catalyst electrical potential measurements. An oxidative dehydrogenation mechanism was proposed and a kinetic model taking into account the catalyst potential changes was developed. The kinetic model was implemented into the three-phase system and validated with the experimental observations. The agreement of the kinetic model to the experimental data, in line with the suggested reaction mechanism, was satisfactory.
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| 36. |
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| 37. |
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| 38. |
- Leino, Ewelina, et al.
(författare)
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Enhanced yields of diethyl carbonate via one-pot synthesis from ethanol, carbon dioxide and butylene oxide over cerium (IV) oxide
- 2011
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 176-177, s. 124-133
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Tidskriftsartikel (refereegranskat)abstract
- There is a considerable industrial interest towards short-chain dialkylcarbonate production technologies due to their attractive properties and apparent commercial applications. Over the years, dimethyl carbonate (DMC), in contrast to diethyl carbonate (DEC), was mainly explored in seeking novel synthesis ideas in academic investigations. Therefore, this work has been devoted to the synthesis of diethyl carbonate. The preliminary results showed that the formation of DEC via direct route starting from ethanol and carbon dioxide (CO2) is limited by the reaction equilibrium and therefore thermodynamics of the reaction has been estimated. Consecutively, butylene oxide was introduced to the reaction system as a dehydrating agent in order to overcome thermodynamic constrains and shift the equilibrium towards diethyl carbonate production. The underlying reason for choosing a longer chain epoxide (i.e. butyl instead of e.g. propyl) was the acute toxicity of short-chain epoxides. A 9-fold enhancement in DEC yield compared to the method without any water removal was achieved over cerium (IV) oxide (CeO2) in the presence of butylene oxide at 180 °C and 9 MPa of total final pressure unequivocally indicating that butylene oxide is an efficient chemical water trap. The highest obtained yield of diethyl carbonate was 2.5 mmol, corresponding to ethanol conversion of 15.6% and selectivity to DEC 10% on ethanol basis. Moreover, kinetic studies were conducted facilitating understanding of the reaction pathway and influence of various parameters on the reaction.
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| 39. |
- Leino, Ewelina, et al.
(författare)
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Influence of the synthesis parameters on the physico-chemical and catalytic properties of cerium oxide for application in the synthesis of diethyl carbonate
- 2013
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Ingår i: Materials Chemistry and Physics. - : Elsevier. - 0254-0584 .- 1879-3312. ; 143:1, s. 65-75
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of cerium (IV) oxide by means of room temperature precipitation method was carried out. The effect of preparation variables such as synthesis time, calcination temperature and pH of the solution on resulting CeO2 properties was discussed. Moreover, the comparison of CeO2 samples prepared in a static and rotation mode of synthesis is presented. The solid catalysts were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, nitrogen physisorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy using pyridine as a probe molecule and temperature programmed desorption of CO2. Significant variations in physicochemical properties of CeO2 by varying the preparation conditions were observed. Furthermore, the catalytic performances of CeO2 catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CeO2 using butylene oxide as a dehydrating agent. The dependence of CeO2 properties on its catalytic activity is evaluated in detail. (C) 2013 Elsevier B.V. All rights reserved.
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| 40. |
- 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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| 41. |
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| 42. |
- Martínez-Klimov, Mark E., et al.
(författare)
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Hydrodeoxygenation of Isoeugenol over Carbon-Supported Pt and Pt-Re Catalysts for Production of Renewable Jet Fuel
- 2021
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 35:21, s. 17755-17768
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Tidskriftsartikel (refereegranskat)abstract
- A series of monometallic platinum and bimetallic platinum–rhenium catalysts supported on mesoporous carbon Sibunit, which is a type of mesoporous, microcrystalline carbon, were investigated for hydrodeoxygenation (HDO) of isoeugenol (IE) at 200–300 °C and 30 bar of H2, using dodecane as a solvent. Catalytic activity was tested in a batch reactor to screen the catalysts and, for comparison, also in the continuous mode. For batch experiments, complete conversion, and a high yield of the desired product, propylcyclohexane (PCH), were obtained for all bimetallic PtRe/Sibunit in 240 min, with the highest yield of PCH when Pt:Re ratio was 1:1 or 1:3. The results for Pt–Re (1:1) were reproducible, in terms of catalytic activity and reusability of catalysts, which showed no deactivation. Monometallic Pt catalysts displayed low activity. Continuous experiments were performed with PtRe(1:1)/Sibunit at 30 bar H2, 0.5 mL/min of the liquid flow, and temperatures between 75 °C and 200 °C. The distribution of products showed deoxygenation at higher temperatures, while at lower temperatures, mainly oxygenated products were formed. XPS results confirmed the presence of ReOx species, where an increase in the platinum loading resulted in a decrease in the fraction of ReOx species and subsequently lower PCH yield.
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| 43. |
- Murzin, D. Yu., et al.
(författare)
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Arabinogalactan hydrolysis and hydrolytic hydrogenation usingfunctionalized carbon materials
- 2015
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 257, s. 169-176
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Tidskriftsartikel (refereegranskat)abstract
- Hydrolysis of the hemicellulose arabinogalactan was studied in this work over several functionalized carbon materials, which were specifically treated to increase their acidities. Hydrolytic hydrogenation of arabinogalactan was investigated using the same materials in a mechanical mixture with ruthenium supported on active carbon. Application of these mixtures resulted in formation of polyols, suppressing simultaneously the generation of side products hydroxymethylfurfural (HMF) and furfural. Formation of high molecular weight compounds (aggregates of sugars and humins) was still quite substantial with a mechanical mixture of Ru/C and a carbon material prepared from sucrose by activation with zinc chloride to increase porosity. Post-treatment of this carbonaceous material with sulphuric acid significantly influenced kinetics of high molecular weight products formation resulting also in elevation of sugar alcohols yields.
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| 44. |
- Murzin, Dmitry Yu., et al.
(författare)
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Hemicellulose arabinogalactan hydrolytic hydrogenation over Ru-modified H-USY zeolites
- 2015
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 330, s. 93-105
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Tidskriftsartikel (refereegranskat)abstract
- The hydrolytic hydrogenation of hemicellulose arabinogalactan was investigated in the presence of protonic and Ru (1-5 wt.%)-modified USY zeolites (Si/Al ratio = 15 and 30). The use of the purely acidic materials was effective in depolymerizing the macromolecule into free sugars. While the latter partly dehydrated into 5-hydroxymethylfurfural and furfural, the generation of high molecular-weight compounds (aggregates of sugars and humins) was not favored, in contrast to previous evidences over beta zeolites. Application of the bifunctional Ru/USY catalyst, comprising well-dispersed metallic nanopartides on the aluminosilicate support, resulted in the formation of galactitol and arabitol, in the suppression of dehydration side products, and further inhibition of polymerization reactions, which only yielded low molecular-weight oligomers. Detailed analysis of the reaction pathways as well as kinetic modeling of hydrolytic hydrogenation was performed with an advanced reaction mechanism.
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| 45. |
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| 46. |
- Nuri, Ayat, et al.
(författare)
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Pd Nanoparticles Stabilized on the Cross-Linked Melamine-Based SBA-15 as a Catalyst for the Mizoroki–Heck Reaction
- 2022
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Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 152, s. 991-1002
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous SBA-15 silicate with a high surface area was prepared by a hydrothermal method, successively modified by organic melamine ligands and then used for deposition of Pd nanoparticles onto it. The synthesized materials were characterized with infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen physisorption, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP-OES). The catalyst was effectively used in the Mizoroki–Heck coupling reaction of various reactants in the presence of an organic base giving the desired products in a short reaction time and with small catalysts loadings. The reaction parameters such as the base type, amounts of catalyst, solvents, and the temperature were optimized. The catalyst was easily recovered and reused at least seven times without significant activity losses. Graphic Abstract: [Figure not available: see fulltext.]
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| 47. |
- Nuri, Ayat, et al.
(författare)
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Pd Supported IRMOF-3 : Heterogeneous, Efficient and Reusable Catalyst for Heck Reaction
- 2019
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Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 149:7, s. 1941-1951
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Tidskriftsartikel (refereegranskat)abstract
- IRMOF-3 with a high surface area prepared by a hydrothermal method was used for deposition of Pd(OAc)(2) on IRMOF-3 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry, scanning electron microscopy, transmission electron microscopy combined with energy dispersive X-ray analysis, wide angle X-ray diffraction spectroscopy and X-ray photoelectron spectroscopy. The prepared porous catalyst was effectively used in the Heck coupling reaction in the presence of an organic base. The reaction parameters such as the type of base, amounts of catalyst and solvents, temperature were optimized. The catalyst was then easily separated, washed, and reused 4 times without significant losses of catalytic activity. [GRAPHICS] .
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| 48. |
- Nuri, Ayat, et al.
(författare)
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Synthesis and Characterization of Palladium Supported Amino Functionalized Magnetic-MOF-MIL-101 as an Efficient and Recoverable Catalyst for Mizoroki–Heck Cross-Coupling
- 2020
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Ingår i: Catalysis Letters. - : Springer. - 1011-372X .- 1572-879X. ; 150:9, s. 2617-2629
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic particles were prepared by a hydrothermal method and then successively covered by Metal–Organic-Frameworks MIL-101-NH2 with a high surface area. This was followed by deposition of Pd(OAc)2 on Fe3O4–NH2@MIL-101-NH2 particles. The final catalyst was characterized with FT-IR, nitrogen physisorption, thermogravimetry (TGA), scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), wide-angle X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared magnetic catalyst was effectively used in the Heck coupling reaction in the presence of an inorganic base. The reaction parameters such as the base type, amounts of catalyst and solvents, temperature, and substrates ratios were optimized. The catalyst was then magnetically separated, washed, and reused 7 times without losing significantly catalytic activity.
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| 49. |
- Patil, Narendra G, et al.
(författare)
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Effect of the load size on the efficiency of microwave heating under stop flow and continuous flow conditions
- 2012
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Ingår i: The Journal of microwave power and electromagnetic energy. - : A Publication of the International Microwave Power Institute IMPI. - 0832-7823. ; 46:2, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4–29 mm onthe heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However,microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load length decreasing the heating efficiency as compared to stop-flow conditions.
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| 50. |
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