In situ ATR-IR studies in aqueous phase reforming of hydroxyacetone on Pt/ZrO2and Pt/AlO(OH) catalysts: The role of aldol condensation

In situ Attenuated Total Reflection Infrared (ATR-IR) spectroscopy was used to study Aqueous Phase Reforming of hydroxyacetone on Pt/AlO(OH) and Pt/ZrO2catalysts at 230 °C/ 30 bar. Formation of strongly adsorbed aldol condensation products was observed on the surface of Pt/ZrO2and ZrO2in contrast to Pt/AlO(OH) and AlO(OH). Peak assignments were supported by DFT calculations of the IR spectra of the condensation products in vacuum and in the presence of water. Aldol condensation of hydroxyacetone leading to compounds with high molecular weight with unsaturated bonds was suggested as a first step in coke formation. Carbonaceous deposits on the surface of the ZrO2support are oxygen-rich and highly reactive, according elemental analysis and TPO. Surprisingly, no adsorbed CO on Pt was observed in the spectra obtained under reaction conditions, suggesting that adsorbed CO is not involved in the rate-determining step in APR of hydroxyacetone

Aqueous-phase reforming of hydroxyacetone solution to bio-based H2 over supported Pt catalysts

Aqueous-phase reforming (APR) is an attractive process to produce bio-based hydrogen from waste biomass streams, during which the catalyst stability is often challenged due to the harsh reaction conditions. In this work, three Pt-based catalysts supported on C, AlO(OH), and ZrO2 were investigated for the APR of hydroxyacetone solution in a fixed bed reactor at 225 °C and 35 bar. Among them, the Pt/C catalyst showed the highest turnover frequency for H2 production (TOF of 8.9 molH2 molPt−1 min−1) and the longest catalyst stability. Over the AlO(OH) and ZrO2 supported Pt catalysts, the side reactions consuming H2, formation of coke, and Pt sintering result in a low H2 production and the fast catalyst deactivation. The proposed reaction pathways suggest that a promising APR catalyst should reform all oxygenates in the aqueous phase, minimize the hydrogenation of the oxygenates, maximize the WGS reaction, and inhibit the condensation and coking reactions for maximizing the hydrogen yield and a stable catalytic performance

An in situ ATR-IR spectroscopy study of aluminas under aqueous phase reforming conditions

High temperature/pressure in situ Attenuated Total Reflection Infrared (ATR-IR) spectroscopy was used to investigate the phase transformation of support γ-Al2O3 into boehmite (AlO(OH)) under the hydrothermal conditions of aqueous phase reforming (APR). Activation energy barriers of boehmite formation in hot compressed water at temperatures between 150 and 180 °C were calculated to be 15.9 ± 4.8 kJ mol−1 for γ-Al2O3 and 43.2 ± 4.3 kJ mol−1 for Pt/γ-Al2O3. The influence of Pt particles is suggested to slow down the phase transformation by selective blockage of the surface nucleation sites. The presence of ethylene glycol has also an inhibiting effect on the transformation due to the carbon deposits formed on the oxide surface. Post-mortem analysis using Raman spectroscopy, 1H and 27Al MAS NMR confirms the formation of boehmite