| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
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| 15. |
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| 16. |
- 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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| 17. |
- 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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| 18. |
- 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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| 19. |
- 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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| 20. |
- 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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| 21. |
- 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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| 22. |
- 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
-
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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| 23. |
- 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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| 24. |
- 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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| 25. |
- 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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| 26. |
- 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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| 27. |
- 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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| 28. |
- 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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| 29. |
- Pham, Ngoc Tung, 1977-
(författare)
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Three-dimensional structured carbon foam : synthesis and applications
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recently, due to the unique properties and structures such as large geometric surface area, electrical conductivity and light weight, 3D structured carbon materials have been attracting extensive attention from scientists. Moreover, the materials, which can provide well-defined pathways for reactants to easily access active sites, are extremely useful for energy conversion as well as environmental and catalysis applications. To date, many precursors have been used for fabrication of 3D structured carbon materials including pitch, carbon nanotubes, graphene, and polymer foams.This thesis, as shown in the thesis title, focus on two main aspects: the study of the characteristics of melamine based carbon foam synthesized at different conditions and their applications. In paper I, it was revealed that through a simple, one-step pyrolysis process, flexible carbon foam synthesized from melamine foam (BasotectÒ, BASF) was obtained. Additionally, through a pyrolysis-activation process, activated carbon foam which possesses hydrophilic nature and high surface area was successfully synthesized. The characteristics of carbon foam such as the hydrophobic/hydrophilic nature, electrical conductivity, mechanical properties and surface chemistry were studied. It was shown that carbon foam could be successfully used as an absorbent in environmental applications e.g. removing of spill oil from water (paper I) or as support for heterogeneous catalysts, which in turn was used not only in gas phase reactions (paper I and IV) but also in an aqueous phase reaction (paper II). Importantly, when combined with a SpinChem® rotating bed reactor (SRBR) (paper II), the monolithic carbon foam/SRBR system brought more advantages than using the foam alone. Additionally, the work in paper III showed the potential of carbon foam in an energy conversion application as anode electrode substrate in alkaline water electrolysis. In summary, the versatility of the carbon foam has been proven through abovementioned lab scale studies and due to the simple, scalable and cost effective pyrolysis and activation processes used for the production, it has potential to be used in large-scale applications.
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| 30. |
- Privalova, Elena I, et al.
(författare)
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Amine Solutions for Biogas Upgrading : Ideal versus Non-Ideal Absorption Isotherms
- 2013
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Ingår i: Chemical Engineering & Technology. - : Wiley-VCH Verlagsgesellschaft. - 0930-7516 .- 1521-4125. ; 36:5, s. 740-748
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Tidskriftsartikel (refereegranskat)abstract
- Amine solutions were applied in carbon dioxide removal from a model mixture of biogas, carried out in a loop reactor system. In addition, the effect of CO2 absorptio acceleration in the presence of piperazine was confirmed and quantified, relating the obtained CO2 loading with the piperazine concentration. Further, the interactions of CO2 and water in aqueous amine solutions were discussed. The obtained acid gas loadings were accurately described taking into account the effect of the dissolved CO2 on the equilibrium constant. A logarithmic absorption isotherm that follows from such considerations and a saturation-type isotherm were compared. In describing the experimental data, advantages and disadvantages of both approaches are discussed.
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| 31. |
- Privalova, Elena I., et al.
(författare)
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Imidazolium-Based Poly(ionic liquid)s as New Alternatives for CO2 Capture
- 2013
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Ingår i: ChemSusChem. - : Wiley-VCH Verlagsgesellschaft. - 1864-5631 .- 1864-564X. ; 6:8, s. 1500-1509
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Tidskriftsartikel (refereegranskat)abstract
- Solid imidazolium-based poly(ionic liquid)s with variable molecular weights that contain the poly[2-(1-butylimidazolium-3-yl)ethyl methacrylate] (BIEMA) cation and different counter anions were evaluated in terms of CO2 capture and compared with classical ionic liquids with similar counter anions. In addition to poly(ionic liquid)s with often-applied ions such as BF4-, PF6-, NTf2-, trifluoromethanesulfonate (OTf-) and Br-, for the first time [BIEMA][acetate] was synthesised, which revealed a remarkably high CO2 sorption performance that exceeded the poly(ionic liquid)s studied previously on average by a factor of four (12.46mgg(PIL)(-1)). This study provides an understanding of the factors that affect CO2 sorption and a comparison of the CO2 capture efficiency with the frequently used sorbents. Moreover, all the studied sorbents were reusable if regenerated under carefully selected conditions and can be considered as suitable candidates for CO2 sorption.
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| 32. |
- Rozmyslowicz, Bartosz, et al.
(författare)
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Selective hydrogenation of fatty acids to alcohols over highly dispersed ReOx/TiO2 catalyst
- 2015
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 328, s. 197-207
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Tidskriftsartikel (refereegranskat)abstract
- Production of fatty alcohols through selective hydrogenation of fatty acids was studied over a 4% ReOx/TiO2 catalyst. Stearic acid was hydrogenated to octadecanol at temperatures and pressures between 180-200 degrees C and 2-4 MPa, with selectivity reaching 93%. A high yield of octadecanol was attributed to a strong adsorption of the acid compared to alcohol on the catalyst, which inhibits further alcohol transformation to alkanes. Low amounts (<7%) of alkanes (mainly octadecane) were formed during the conversion of stearic acid. However, it was found that the catalyst could be tuned for the production of alkanes. The reaction intermediates were octadecanal and stearyl stearate. Based on the reaction products analysis and catalyst characterization, a reaction mechanism and possible pathways were proposed.
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| 33. |
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| 34. |
- Salmi, Tapio, et al.
(författare)
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Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts
- 2014
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Ingår i: AIChE Journal. - : John Wiley & Sons. - 0001-1541 .- 1547-5905. ; 60:3, s. 1066-1077
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic models were developed for the hydrolysis of O-acetyl-galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H2SO4, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation-exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose.© 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014
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| 35. |
- Schmidt, Sabrina A., et al.
(författare)
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Preparation and characterization of neat and ZnCl2 modified zeolites and alumina for methyl chloride synthesis
- 2013
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 468, s. 120-134
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Tidskriftsartikel (refereegranskat)abstract
- A range of zeolite and alumina based catalysts, neat and impregnated with ZnCl2, were screened for gas-phase methyl chloride synthesis from methanol and HCl. The catalysts were characterized with FTIR, TEM, XPS, N-2-physisorption, XRD and EDX to identify the relationship between the catalyst characteristics and their activity and selectivity in methyl chloride synthesis. The work was focused on catalyst performance and stability, acid properties of catalysts and the influence of zinc impregnation. Upon modification with ZnCl2, the number of strong and medium Bronsted acid sites (BAS) decreased, while the number of Lewis acid sites (LAS) increased. The zinc species detected on the catalyst surface is possibly similar to ZnOCl. The presence of ZnCl2 as surface species is not probable, as chlorine is partially removed from the catalyst during calcination at 400 degrees C. However, the binding energy determined by XPS suggests a Zn2+ surface species. Zn2+ containing particles were observed on zeolites by TEM, which show a dependence of the particle size on the support acidity. The activities of the catalysts increased with the number of medium and strong LAS, whereas the methyl chloride selectivity slightly decreased giving dimethyl ether as a by-product. As the increase of acid sites upon modification with the same amounts of ZnCl2 was most pronounced for zeolite catalysts, they exhibited the highest activity. However, the zeolite catalysts showed deactivation with time on stream. Zn/H-ZSM 5 zeolite catalysts exhibited a higher stability in the synthesis of methyl chloride than ZnCl2 modified H-Beta and could be regenerated by burning the coke in air at 400 degrees C. Neat alumina and ZnCl2 modified alumina catalysts were active and selective at 300 degrees C and higher temperatures, but zeolite catalysts might be suitable for methyl chloride synthesis at lower temperatures, i.e. 200 degrees C.
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| 36. |
- Sifontes Herrera, Víctor A, et al.
(författare)
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Sugar hydrogenation over a Ru/C catalyst
- 2011
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Ingår i: Journal of chemical technology and biotechnology (1986). - : Society of Chemical Industry. - 0268-2575 .- 1097-4660. ; 86:5, s. 658-668
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: In recent years, exploitation of renewable resources has gained considerable attention. In this respect, polyols derived from the hydrogenation of sugar molecules are versatile molecules with a variety of uses, such as low-caloric sweeteners. The hydrogenation of D-maltose, D-galactose, L-rhamnose and L-arabinose was carried out on a finely dispersed Ru/activated carbon catalyst with the objective of studying the kinetics of the production of the corresponding polyols. The reactions were carried out in a stirred tank reactor at temperatures ranging from 90 to 130 °C and hydrogen pressures from 40 to 60 bar. RESULTS: Sugar conversions up to 100% were achieved. Some by-product formation affecting the quality of the selectivity was also observed at elevated operating conditions. The catalyst was characterized by scanning electron microcopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES) and nitrogen physisorption. Kinetic models based on the Langmuir Hinshelwood assumptions were proposed for the reactions and a nonlinear regression was performed to obtain the numerical values of the kinetic parameters. CONCLUSIONS: The kinetic models predicted well the sugar hydrogenation process and the kinetic parameters were established. The model can be used to predict the behaviour of batchwise operating slurry reactors. Copyright © 2011 Society of Chemical Industry
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| 37. |
- Simakova, Olga A, et al.
(författare)
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Linoleic acid isomerization over mesoporous carbon supported gold catalysts
- 2010
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Ingår i: Catalysis Today. - : Elsevier B.V.. - 0920-5861 .- 1873-4308. ; 150:1-2, s. 32-6
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Tidskriftsartikel (refereegranskat)abstract
- Gold catalyst supported on mesoporous carbon and silica were synthesized, characterized by TEM, XRD, XPS and tested in linoleic acid isomerization. Nature of the support affects the selectivity towards isomerization in relation to unwanted hydrogenation. In particular carbon support allowed much higher selectivity in double bond migration compared to silica. Effect of carbon surface oxidative pre-treatment on selectivity of catalyst was investigated.
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| 38. |
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