Platinum on carbonaceous supports for glycerol hydrogenolysis: Support effect (original) (raw)
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Chemoselective Hydrogenolysis of Glycerol Catalyzed by Platinum on Carbonaceous Supports
Highly dispersed Pt-nanoparticles supported onto carbonaceous materials, which are characterized by their surface area, were employed to catalyze the hydrogenolysis of glycerol in water. The surface area of the support proved to steer the aggregation process of the nanoparticles with time, consequently influencing the catalyst performance in terms of glycerol conversion, reforming activity and chemoselctivity versus 1,2-propandiol, which was the main liquid product. The support with the highest surface area showed the best control on the nanoparticles' aggregation.
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.
Catalysis Letters, 2014
Platinum catalysts with 2 % (w/w) Pt supported on ZrO 2 , Sulfated ZrO 2 , c-Al 2 O 3 , AlPO 4 , activated carbon and Y-Zeolite have been investigated for the selective vapour phase hydrogenolysis of biomass derived glycerol to 1,3-propanediol at moderate reaction temperature and atmospheric pressure. All the catalysts were synthesized by the wet impregnation method using chloroplatinic acid precursor. The physico-chemical properties of the catalysts were investigated by XRD, FTIR, SEM, CO-chemisorption, TPR, TEM, NH 3 -TPD and Pyridine adsorbed FTIR spectroscopy. The catalytic experimental results combined with the characterization studies showed that the glycerol conversion and the yield of 1,3-propanediol greatly depend on the nature of the support. The results also suggest that a correlation exists between catalytic activity and acidity. A key parameter to assess the best catalyst performance is the dispersion of Pt on the support and the metal-support interaction. Among various supported Pt catalysts screened for vapour phase glycerol hydrogenolysis, the Pt/AlPO 4 catalyst exhibited the best activity towards glycerol conversion (100 %) and 1,3-propanediol selectivity (35.4 %).
Journal of Catalysis, 2008
Reaction kinetics measurements were carried out to study the conversion of aqueous solutions of glycerol (30 and 80 wt%) over carbon-supported Pt and Pt-Re catalysts at temperatures from 483 to 523 K. The results of these studies show that the turnover frequencies for production of H 2 , CO, CO 2 , and light alkanes (primarily methane) all increase upon the addition of Re to Pt/C catalysts. The molar ratio of H 2 /CO increases, while the CO/CO 2 ratio decreases with Re addition, indicating increased rate of watergas shift. For glycerol conversion over a Pt-Re/C catalyst with an atomic Pt:Re ratio of 1:1, increasing pressure or decreasing temperature leads to an increase in the production of alkanes and light oxygenated hydrocarbons (ethanol, methanol, propanediols, and acetone) at the expense of CO and CO 2. Temperatureprogrammed desorption studies and microcalorimetric measurements indicate that addition of Re to Pt modifies the interaction of CO with surface sites. X-ray absorption spectroscopy and transmission electron microscopy studies provide evidence indicating that Pt-Re/C catalysts consist primarily of bimetallic nanoparticles with sizes below 2 nm, and Re inhibits the sintering of these nanoparticles during reaction conditions for glycerol conversion. The results of these reaction kinetic studies and characterization studies indicate that the performance of Pt-Re/C catalysts for glycerol conversion is related to the formation of Pt-Re nanoparticles, for which Re promotes the overall rate of glycerol reforming by reducing the binding energy of CO to Pt, thereby leading to less extensive blocking of surface sites by reaction intermediates and/or products. In addition, the presence of Re facilitates water-gas shift and CO bond cleavage reactions.
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.
Catalysis Letters, 2017
A series of 1%wt. AuPt (6:4) catalysts were prepared by sol immobilization using acidic (TiO 2 , H-Mordenite, SiO 2 , MCM-41, Sulphated ZrO 2 (S-ZrO 2)) and one basic (MgO) oxide supports. EDX analysis showed that only alloyed AuPt nanoparticles are present on all catalysts but the final size of AuPt particles is significantly affected by the support. Indeed, on TiO 2 the mean AuPt nanoparticles diameter is 3.7 nm whereas for all the remaining support larger AuPt nanoparticles with diameter of 6-7.5 nm were obtained. AuPt catalysts result very active in catalyzing the liquid phase hydrogenolysis of glycerol to 1,2-propandiol with ethylene glycol, 1-propanol and 2-propanol as main by-products The role of the support has been highlighted in terms of acidic properties, the medium strength of Lewis acid sites of TiO 2 leading to the best performance in terms of activity, selectivity and stability of the catalytic system.
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.
Support effects in the aqueous phase reforming of glycerol over supported platinum catalysts
Applied Catalysis A: General, 2012
Aqueous phase glycerol reforming was studied for a set of Pt catalysts supported on ␥-Al 2 O 3 , SiO 2 and amorphous silica-alumina (ASA) with varying alumina concentrations. The main products at 225 • C under 29 bar N 2 pressure for a feed of 20 wt.% glycerol are H 2 , CO 2 and C 1-C 3 alkanes, 1,2-propanediol, hydroxyacetone and C 1-C 3 monoalcohols are the products in the liquid phase. Boehmite formation is observed for the ␥-Al 2 O 3 and ASA supported catalysts. The higher the Al concentration of ASA, the higher the amount of boehmite. Especially at low Al concentrations, the presence of boehmite is limited and silica leaches from the ASA support under reaction conditions. The increased surface acidity as a result of the presence of boehmite leads to increased hydroxyacetone formation (glycerol dehydration) and 1,2-propanediol (hydroxyacetone hydrogenation) formation. The activity of boehmite supported Pt for hydrodeoxygenation and reforming reactions is higher than that of ␥-Al 2 O 3 and SiO 2 supported Pt.
Glycerol hydrogenolysis to n -propanol over Zr-Al composite oxide-supported Pt catalysts
Chinese Journal of Catalysis, 2018
Zr-Al mixed oxide supported Pt catalysts with different Zr/Al mole ratios (2.5%Pt/ZrxAl1-xOy) were synthesized by an impregnation method and used for the selective hydrogenolysis of glycerol to n-propanol in an autoclave reactor. The catalysts were fully characterized by X-ray powder diffraction, Brunauer-Emmett-Teller surface area analysis, CO chemisorption, H2 temperature-programmed reduction, pyridine-infrared spectroscopy, and NH3-temperature-programmed desorption. The results revealed that the Zr/Al ratio on the support significantly affected the size of the platinum particles and the properties of the acid sites on the catalysts. The catalytic performance was well correlated with the acidic properties of the catalyst; specifically, more acid sites contributed to the conversion and strong acid sites with a specific intensity contributed to the deep dehydration of glycerol to form n-propanol. Among the tested catalysts, 2.5 wt% Pt/Zr0.7Al0.3Oy exhibited excellent selectivity for n-propanol with 81.2% glycerol conversion at 240 °C and 6.0 MPa H2 pressure when 10% aqueous glycerol solution was used as the substrate. In addition, the effect of various reaction parameters, such as H2 content, reaction temperature, reaction time, and number of experimental cycles were studied to determine the optimized reaction conditions and to evaluate the stability of the catalyst.
RSC Advances, 2014
ABSTRACT Although Pt is the most appropriate catalyst for aqueous phase reforming (APR) of glycerol to generate H 2 , it is expensive. We studied its possible minimisation to levels where acceptable H 2 yields are still maintained. When an additional catalytic metal, Ni, was introduced to our Pt/CeO 2 –Al 2 O 3 catalyst, the Pt content could be reduced from 3 to 1 wt%, with a slight increase in H 2 production. In this study, Pt and Ni in various ratios were supported on alumina doped with 3 wt% ceria, and the resulting materials were characterised and tested as catalysts for the APR of glycerol. Amongst the catalysts tested, bimetallic 1Pt–6Ni/3CeAl (containing 1 wt% Pt and 6 wt% Ni) gave the highest H 2 yield (86%) and gas-phase C yield (94%). Thus, although 1Pt–6Ni/3CeAl and our reported 3Pt/3CeAl catalyst produced almost same amount of H 2 (1.8 and 1.9 mmol, respectively) per gram of catalyst per hour, the latter produced three times as much H 2 per gram of Pt per hour (195 mmol); this measure is crucial to the competitiveness of a catalyst in large-scale H 2 production. X-ray diffraction (XRD) patterns and thermogravimetric analyses of the spent catalysts showed no serious catalyst deactivation by carbon deposition after 30 h on stream, except in the case of Pt-free 6Ni/3CeAl, which ceased to produce H 2 after 15 h on stream. XRD and X-ray photoelectron spectroscopic analyses demonstrated that adding Ni impacted both the crystallite and electronic structure of Pt. These effects likely conspired to produce the high glycerol conversion and gas phase C yield and, ultimately, the high H 2 yield observed over 1Pt–6Ni/3CeAl.