Support effects in the aqueous phase reforming of glycerol over supported platinum catalysts (original) (raw)
Related papers
2014
A detailed and in-depth study of the deactivation of Pt and/or Ni-based ␥-Al 2 O 3 catalysts prepared by impregnation and acid and basic sol-gel methods, previously tested in glycerol aqueous phase reforming (APR) for H 2 production, has been made. The aim has been to get a further and advanced understanding of the factors behind this deactivation. Accordingly, all the used catalysts were systematically characterized by appropriate techniques, such as ICP-AES, XRD, XPS and TG/DGT-O 2 . Some used samples were also examined by BET, TPD-NH 3 , TPR-H 2 and TEM. The characterization results corroborate the following: (i) a significant part of ␥-Al 2 O 3 in sol-gel catalysts was structurally transformed into ␥-AlOOH, changing their textural properties, such as surface area and porosity, surface acidity and metal dispersion, and (ii) the Ni metallic particles in the impregnated catalysts underwent major agglomeration, while the Ni particles in the sol-gel counterparts were more affected by re-oxidation phenomena. Data obtained by ICP-AES and thermal analysis indicate, respectively, that Pt and Ni phase leaching and the formation of highly graphitized coke were negligible. However, some adsorption of carbonaceous molecular species has been detected on some catalysts. All these observations clearly confirm that the metallic and acid active sites of Pt and/or Ni-based ␥-Al 2 O 3 catalysts experimented quantitative and qualitative modifications during the glycerol APR process that compromised their catalytic performances.
Optimised hydrogen production by aqueous phase reforming of glycerol on Pt/Al2O3
International Journal of Hydrogen Energy, 2016
Aqueous phase reforming of glycerol was studied over a series of γ-Al2O3 supported metal nanoparticle catalysts for hydrogen production in a batch reactor. Of the metals studied, Pt/Al2O3 was found to be the most active catalyst under the conditions tested. A further systematic study on the impact of reaction parameters, including stirring speed, pressure, temperature, and substrate/metal molar ratio, was conducted and the optimum conditions for hydrogen production (and kinetic regime) were determined as 240 °C, 42 bar, 1000 rpm, and substrate/metal molar ratio ≥ 4100 for a 10 wt% glycerol feed. The glycerol conversion and hydrogen yield achieved at these conditions were 18% and 17%, respectively, with negligible CO and CH4 formation. Analysis of the spent catalyst using FTIR provides an indication that the reaction pathway includes glycerol dehydrogenation and dehydration steps in the liquid phase in addition to typical reforming and water gas shift reactions in the gas phase.
Applied Catalysis B: Environmental, 2010
Pt supported on amorphous silico alumina (Pt/ASA) was studied as a catalyst for glycerol hydrogenolysis (dehydration + hydrogenation) to 1,2-propanediol under mild operation conditions (493 K and 45 bar H 2 pressure). Glycerol hydrogenolysis also took place in experiments performed under N 2 pressure due to hydrogen available from glycerol aqueous phase reforming. As both acid and metallic sites are involved in this process a study including activity tests and different characterization techniques (TPR and FTIR of adsorbed pyridine, NH 3-TPD, XPS and TGA) were applied to this catalytic system (ASA support and Pt/ASA catalyst) in order to get a deeper understanding about their interactions.
Journal of Molecular Catalysis A: Chemical, 2013
A series of platinum catalysts supported over various supports (Al 2 O 3 , Al 2 O 3-SiO 2 and TiO 2) were prepared and characterized by X-ray diffraction, N 2 sorption, H 2 chemisorption, temperature programmed reduction, FTIR of adsorbed pyridine, 3,3-dimethyl-1-butene isomerization and cyclohexane dehydrogenation. These catalysts were evaluated for aqueous-phase process (APP) of glycerol at 210 • C, under N 2 or H 2 atmosphere (60 bar as total pressure). Among the tested catalysts, Pt/TiO 2 was the most active and the most selective toward C 3 products (propanediols, propanol) which can be further valorized into chemicals. TiO 2 was identified as the support leading to the most stable Pt metallic phase, catalytic phase on which the hydrogenation/dehydrogenation reactions take place. The presence of acidic sites brought by the oxide support is necessary for the dehydration reactions (i.e. for C O cleavages), but a too high quantity of these sites can promote the C C bond cleavages via an acidic cracking mechanism. Among the various supported Pt-based catalysts studied in this work, Pt/TiO 2 sample appears to be the most promising system for the transformation of polyol in aqueous phase.
Aqueous phase reforming of glycerol for hydrogen production over Pt–Re supported on carbon
Applied Catalysis B: Environmental, 2010
Hydrogen production from the aqueous phase reforming of glycerol over 3%Pt-Re/C (1 and 3% Re) has been studied in the absence and presence of base, and the results compared with a Re-free 3%Pt/C catalyst. Although the Pt/C catalyst is very selective toward the production of hydrogen, catalytic activity is low. Addition of Re significantly increases the conversion of glycerol, at some loss of hydrogen selectivity to light hydrocarbons and water-soluble oxygenates. Addition of 1%KOH to the feedstock results in a small increase in glycerol conversion with 3%Pt-3%Re/C, an increase in the gas phase product selectivity in terms of H 2 /CO 2 ratio, and an increase in production of aqueous phase oxygenates. A modest increase in hydrogen gas phase selectivity with base addition with 3%Pt-3%Re/C arises primarily from reducing the selectivity toward C 2 + alkanes, products that consume H 2. In comparison, KOH addition to the glycerol feed with the Re-free 3%Pt/C catalyst provides an increase in glycerol conversion but results in a decline in both H 2 and alkane selectivity relative to aqueous phase oxygenates. The highest hydrogen productivity among the catalysts tested is achieved with a 3%Pt-3%Re/C catalyst with added KOH base. The observed product distributions can be understood in terms of the different reaction pathways that become emphasized depending on catalyst composition and pH.
Renewable Energy, 2011
Aqueous-phase reforming of oxygenated hydrocarbons for hydrogen production presents several advantages as feed molecules can be easily found in a wide range of biomass, there is no need for its vaporization and the process allows thorough exploitation of the environmental benefits of using hydrogen as an energy carrier. The use of glycerol in particular is motivated due to its availability as a consequence of increasing biodiesel production worldwide. In this contribution, the performance of Ptbased catalysts supported on different oxides (Al 2 O 3 , ZrO 2 , MgO and CeO 2 ) is studied on glycerol reforming. All catalysts led to a hydrogen-rich gas phase. However, a good potential activity with high production of hydrogen and low concentration of undesired hydrocarbons was accomplished over the catalysts supported on MgO and ZrO 2 . The high electron donating character of such oxides indicates the influence of the nature of the support in catalytic performance for glycerol reforming.
Production of hydrogen by aqueous-phase reforming of glycerol
International Journal of Hydrogen Energy, 2008
The activities and stabilities of Pt, Ni, Co, and Cu catalysts for H 2 production by aqueousphase reforming of glycerol, as well as the effect of support on activity and stability, were studied using a fixed-bed flow reactor. Both of the fresh and spent catalysts were characterized by XRD, N 2 adsorption/desorption, TPO, H 2 -TPR, and H 2 chemisorption. It was found that the activity of the metal catalysts increased in the order of Co, Ni, Cu and Pt.