Deactivation study of the Pt and/or Ni-based γ-Al2O 3 catalysts used in the aqueous phase reforming of glycerol for H2 production (original) (raw)
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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.
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- South African Institute of Mining and Metallurgy
Gold has been demonstrated as a possible catalyst for oxidation reactions. Some evidence for a possible promotion effect of platinum has also been recorded. The influence of platinum as promoter for Au/γ-Al2O3 prepared via anionic ion-exchange for the oxidation of glycerol was investigated in a batch reactor at 60°C. It is inferred that the addition of platinum reduces the catalytic activity and the rate of deactivation, resulting in an overall higher final conversion of glycerol with increasing platinum loading. The addition of platinum to the catalyst favours the formation of the desired product, glyceric acid.
International Journal of Hydrogen Energy, 2017
The hydrothermal stability of Ni and NiPt-containing g-Al 2 O 3 catalysts in aqueous phase reforming (APR) of glycerol/water mixture (C 3 H 8 O 3 /H 2 O, 10% w/w) was investigated putting in evidence the influence of the preparation method; solegel in basic medium (SGB) and impregnation on an in-house prepared solegel g-Al 2 O 3 support (SGI). All developed catalysts were characterized by ICP-AES, TPR-H 2 , in-situ heating XRD-O 2 , DSC/TG-N 2 /O 2 and exsitu reduction of XRD-H 2, N 2 physisoption and TEM techniques. The results indicate that SGI method and calcination treatment at 750 C were crucial in extending the catalytic useful life of NiPt-containing g-Al 2 O 3 catalysts, resulting in an adequate distribution of Nie Pt metallic particles and good stability of g-Al 2 O 3 support against the severe hydrothermal conditions of APR process. The SGI method led to form stable NiPt catalysts with relatively big Ni particles and stable hydrothermal properties of g-Al 2 O 3 support, while the SGB catalysts exhibited well-dispersed Ni particles but unstable catalytic behavior. These last catalysts presented high glycerol conversions during the first hours of APR glycerol/water reaction, however, an important decrease in terms of glycerol conversion was observed after 24 h time-on-stream. The experimental results suggested that the most suitable stable and active catalyst was the NiPt/ASGI7 (better than >NiPt/ASGI6 > NiPt/ ASGI5 >>> NiPt/ASGB7). This catalyst showed best catalytic activity and good catalytic stability along 56 h of time-on-stream, reaching, at steady state, highest total glycerol conversion (z79%) and glycerol into gaseous products (z57%) in APR reaction of glycerol/ water mixture for hydrogen generation.
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.
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.
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.