Structure sensitivity and hydration effects in Pt/TiO2 and Pt/TiO2?SiO2 catalysts for NO and propane oxidation

The NO and propane oxidation activities of a series of 1%Pt/TiO2–SiO2 catalysts show different underlying trends as the support composition changes. Surface characterisation of the catalysts indicates that the trend for NO conversion is consistent with the oxidation rate being dependent on the degree of metallic character of the Pt nanoparticles, rather than their morphology. Although a similar correlation is expected for the total oxidation of propane, it is masked by the effects of adventitious ions originating during manufacture of the support materials. When residual chloride is present in the support, most of the exposed Pt is stabilised in its low-activity ionic form; while support materials containing W or oxidised-S ions give rise to catalysts with much higher activity than expected from their measured Pt0 content. When a Cl-containing, but SiO2-free, TiO2 support material is pre-treated hydrothermally, the propane-oxidation activity of the resultant Pt/TiO2 catalyst is substantially improved, so that it matches the performance of highly-metallic Pt supported on TiO2 containing 16 wt% SiO2. The hydrothermal pre-treatment removes residual chloride from the support material, but it also leaves the catalyst in a hydrated state. We show that, by controlling the metallic content of Pt nanoparticles, understanding the promoting and inhibiting effects of adventitious ions, and optimising the degree of catalyst hydration, the activity of 1%Pt/TiO2–SiO2 catalysts can be made to exceed that of a benchmark 2%Pt/γ-Al2O3 formulation for both NO and propane oxidation

Biomass pyrolysis oils for hydrogen production using chemical looping reforming

This study considers the feasibility of using highly oxygenated and volatile pyrolysis oils from biomass wastes as sustainable liquid fuels for conversion to a hydrogen-rich syngas using the chemical looping reforming process in a packed bed. Pine oil and palm empty fruit bunches oil- 'EFB'- were investigated with a Ni/Al 2O 3 catalyst doubling as oxygen transfer material (OTM). The effect of molar steam to carbon ratio (S/C) and weight hourly space velocity were investigated at 600 °C and atmospheric pressure on the fuel and steam conversion, the H 2 yield and the H- and C-products distribution. With a downward fuel feed configuration and using a H 2-reduced catalyst, maximum averaged fuel conversions of ∼97% for pine oil and 89% for EFB oil were achieved at S/C ratios of 2.3 and 2.6 respectively (on a water-free oil basis). This produced H 2 with a yield efficiency of approximately 60% for pine oil and 80% for EFB oil notwithstanding equilibrium limitations, and with little CH 4 by-product. Both oils exhibited very similar outputs with varying S/C. Upon a short number of cycles, i.e. starting from an oil-reduced catalyst, the fuel conversion dropped slightly but the steam conversion was constant, resulting in a slow decrease in H 2 yield. Despite their high level of oxygen content, the pyrolysis oils were shown to maintain close to 90% reduction of the oxidised catalyst upon repeated cycles, but the rate of reduction decreased with cycling

Data associated with 'The kinetics of acetic acid steam reforming on Ni/Ca-Al2O3 catalyst'

Data associated with figures of paper "The kinetics of acetic acid steam reforming on Ni/Ca-Al2O3 catalyst

Autothermal Reforming of Acetic Acid to Hydrogen and Syngas on Ni and Rh Catalysts

The autothermal reforming (ATR) of acetic acid (HAc) as a model bio-oil compound is examined via bench scale experiments and equilibrium modelling to produce hydrogen and syngas. This study compares the performance of nickel (Ni-Al, Ni-CaAl) vs. rhodium (Rh-Al) for particulate packed bed (PPB), and of Rh-Al in PPB vs. Rh with and without Ceria for honeycomb monolith (‘M’) catalysts (R-M and RC-M). All PPB and M catalysts used Al2O3 as main support or washcoat, and when not pre-reduced, exhibited good performance with more than 90% of the HAc converted to C1-gases. The maximum H2 yield (6.5 wt.% of feed HAc) was obtained with both the Rh-Al and Ni-CaAl catalysts used in PPB, compared to the equilibrium limit of 7.2 wt.%, although carbon deposition from Ni-CaAl at 13.9 mg gcat−1 h−1 was significantly larger than Rh-Al’s (5.5 mg gcat−1 h−1); close to maximum H2 yields of 6.2 and 6.3 wt.% were obtained for R-M and RC-M respectively. The overall better performance of the Ni-CaAl catalyst over that of the Ni-Al was attributed to the added CaO reducing the acidity of the Al2O3 support, which provided a superior resistance to persistent coke formation. Unlike Rh-Al, the R-M and RC-M exhibited low steam conversions to H2 and CH4, evidencing little activity in water gas shift and methanation. However, the monolith catalysts showed no significant loss of activity, unlike Ni-Al. Both catalytic PPB (small reactor volumes) and monolith structures (ease of flow, strength, and stability) offer different advantages, thus Rh and Ni catalysts with new supports and structures combining these advantages for their suitability to the scale of local biomass resources could help the future sustainable use of biomasses and their bio-oils as storage friendly and energy dense sources of green hydrogen

Dry reforming of methane over a Ni/Al2O3 catalyst in a coaxial dielectric barrier discharge reactor

International audienceA coaxial double dielectric barrier discharge (DBD) reactor has been developed for plasmacatalytic conversion of CH 4 and CO 2 into syngas and other valuable products. A supported metal catalyst (Ni/Al 2 O 3) reduced in a methane discharge is fully packed into the discharge region. The influence of the Ni/Al 2 O 3 catalyst packed into the gas gap on the electrical characteristics of the discharge has been investigated. The introduction of the catalyst pellets leads to a transition in discharge behaviour from a typical filamentary microdischarge to a combination of spatially-limited microdischarges and a predominant surface discharge on the catalyst surface. It is also found that the breakdown voltage of the CH 4 /CO 2 discharge significantly decreases when the reduced catalyst is fully packed in the discharge area. Conductive Ni active sites dispersed on the catalyst surface contribute to the expansion of the discharge and enhancement of charge transfer. In addition, plasma-catalytic dry reforming of CH 4 has been carried out with the reduced Ni/Al 2 O 3 catalyst using a mixing ratio of CH 4 /CO 2 = 1 and a total flow rate of 50 ml min -1. An increase in H 2 selectivity is observed compared to dry CH 4 reforming with no catalyst, while the H 2 /CO molar ratio greatly increases from 0.84 to 2.53 when the catalyst is present