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Highly stable and active CeO2-ZrO2 metal oxide catalyst was synthesized via the combustion method and was further functionalized with sulphate (SO42-) groups. The morphology, surface functionalities, and composition of the metal oxide catalyst were determined by scanning electron microscopy, N2 adsorption and desorption measurement, X-ray diffraction, and Fourier transform infrared spectroscopy. The synthesized catalyst was used for esterification of glycerol with acetic acid. Effects of the process parameters including acetic acid to glycerol molar ratios (3-20), catalyst loadings (1-9 wt.%) and reaction temperatures (70–110°C) on the glycerol conversion and glycerol acetates selectivity were studied. Excellent catalytic activity was observed by using the sulphated metal oxide catalyst resulting in a glycerol conversion as high as 99.12%. The selectivity towards the di and triacetin (fuel additive) formed stood at 57.28% and 21.26% respectively. The reaction rate constants and activation energies were also estimated using a Quasi-Newton algorithm, namely Broyden’s method and Arrhenius equations at 80-110℃. The calculated values were in accordance with the experimental values which confirmed the model. Finally, the developed catalyst could be reused for three consecutive cycle without major loss of its activity. Overall, the findings presented here could be instrumental to drive future research and commercialization efforts directed toward biodiesel glycerol valorisation into fuel additives.

The performance of oxygen carriers contributes significantly to the efficiency of chemical looping combustion (CLC), an emerging carbon capture technology. Despite their low cost, Fe2O3-based oxygen carriers suffer from sintering-induced deactivation and low oxygen-carrying capacity (OCC) during CLC operations. Here, we report the development of a sintering-resistant MgO-doped Fe2O3oxygen carrier with an optimal composition of 5MgO·MgFe2O4, which exhibits superior cyclic stability and an OCC of 0.45 mol O/mol Fe (2.25 mmol O/gsolid), exceeding the widely accepted OCC limit of 0.167 mol O/mol Fe (2.08 mmol O/gsolid) of unmodified commercial Fe2O3. This result distinguishes this report from all past studies, in which efforts to enhance the cyclic stability of Fe-based oxygen carriers would always result in dilution of the OCC. The capacity enhancement by MgO is attributed to the unique mixtures of MgxFe1-xO (halite) and Mg1-yFe2+yO4(spinel) solid solutions, which effectively reduce the exergonicity for the reduction from Fe3+to Fe2+, while preventing any irreversible structural transformations during the redox process. This hypothesis-driven oxygen carrier design approach provides a new avenue for tailoring the lattice oxygen activities of oxygen carriers for chemical looping applications. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version The authors acknowledge financial support by the Ministry of Education Singapore’s Academic Research Fund Tier 1 (RT03/19 and RG112/18) and the National Research Foundation (NRF), Prime Minister’s Office, Singapore, under its Campus for Research Excellence and Technological Enterprise (CREATE) programme. Y.D. is grateful for financial support from the National Natural Science Foundation of China (21802070).

The catalytic hydrogenation of CO2 to methanol depends significantly on the structures of metal-oxide interfaces. We show that doping a high-valency metal, viz. tungsten, to CeO2 could render improved catalytic activity for the hydrogenation of CO2 on a Cu/CeW0.25Ox catalyst, whilst making it more selective towards methanol than the undoped Cu/CeO2. We experimentally investigated and elucidated the structural-functional relationship of the Cu/CeO2 interface for CO2 hydrogenation. The promotional effects are attributed to the irreversible reduction of Ce4+ to Ce3+ by W-doping, the suppression of the formation of redox-active oxygen vacancies on CeO2, and the activation of the formate pathway for CO2 hydrogenation. This catalyst design strategy differs fundamentally from those commonly used for CeO2-supported catalysts, in which oxygen vacancies with high redox activity are considered desirable. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This research is funded by the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme and Ministry of Education, Singapore under its AcRF Tier 1 (RT03/19).

The catalytic hydrogenation of CO2 to methanol depends significantly on the structures of metal-oxide interfaces. We show that doping a high-valency metal, viz. tungsten, to CeO2 could render improved catalytic activity for the hydrogenation of CO2 on a Cu/CeW0.25Ox catalyst, whilst making it more selective towards methanol than the undoped Cu/CeO2. We experimentally investigated and elucidated the structural-functional relationship of the Cu/CeO2 interface for CO2 hydrogenation. The promotional effects are attributed to the irreversible reduction of Ce4+ to Ce3+ by W-doping, the suppression of the formation of redox-active oxygen vacancies on CeO2, and the activation of the formate pathway for CO2 hydrogenation. This catalyst design strategy differs fundamentally from those commonly used for CeO2-supported catalysts, in which oxygen vacancies with high redox activity are considered desirable., Applied Catalysis B: Environmental, 306, ISSN:1873-3883, ISSN:0926-3373

Chemical looping combustion is a cost-competitive solution for producing low carbon electricity. In this paper, we investigate by means of a process modelling study, the coupling of chemical looping combustion of solid fuels with advanced steam-based power cycles, viz. supercritical, ultra-supercritical and advanced ultra-supercritical Rankine cycles. The energy and exergy efficiencies of the various chemical looping combustion power plant configurations are compared against the reference plants without carbon capture. Our models incorporate practical considerations for reactor design. With an upper operating temperature limit of 950 °C, the maximum efficiencies achievable by integrated gasification combined cycle chemical looping combustion (IGCC–CLC) and in situ gasification chemical looping combustion power plants (iG-CLC) are 41.3% and 41.5%, respectively. Overall, iG-CLC emerges as the most efficient CLC configuration. Comparing to an integrated gasification combined cycle without carbon capture, the energy efficiency penalties for capturing CO2 from iG-CLC coupled with subcritical, supercritical, ultra-supercritical or advanced ultra-supercritical steam cycles are 5.1%, 5.0%, 5.2% or 13.0%, respectively. The biomass-fired chemical looping combustion power plants also show low energy efficiency penalties (

For supported metal catalysts, the architectures of the supports are as important as the chemical compositions of the catalysts and the morphologies of the supported metal particles. In this work, we report a simple and versatile method for preparing Ni nanoparticle catalysts supported on Mg-Al mixed oxides for the dry reforming of methane. The catalysts were prepared by freeze drying of Ni-Mg-Al layered double hydroxide precursors, followed by calcination and H2 reduction. Compared to Ni/Mg-Al-O catalysts prepared by oven drying, the freeze-dried catalysts retain a unique, loosely packed platelet structure with high macroporosity, which gives rise to high dispersion, high DRM activity and high resistance against deactivation. At 800 °C, the catalyst consistently achieves equilibrium CH4 conversion of 95% over 100 h time on stream with a of 40 L-CH4 h−1 g-cat−1. The DRM activity seen in the present study supersedes other Ni-based catalysts reported in the literature. National Research Foundation (NRF) Accepted version This work is funded by the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.

Chemical looping combustion is a cost-competitive solution for producing low carbon electricity. In this paper, we investigate by means of a process modelling study, the coupling of chemical looping combustion of solid fuels with advanced steam-based power cycles, viz. supercritical, ultra-supercritical and advanced ultra-supercritical Rankine cycles. The energy and exergy efficiencies of the various chemical looping combustion power plant configurations are compared against the reference plants without carbon capture. Our models incorporate practical considerations for reactor design. With an upper operating temperature limit of 950 °C, the maximum efficiencies achievable by integrated gasification combined cycle chemical looping combustion (IGCC–CLC) and in situ gasification chemical looping combustion power plants (iG-CLC) are 41.3% and 41.5%, respectively. Overall, iG-CLC emerges as the most efficient CLC configuration. Comparing to an integrated gasification combined cycle without carbon capture, the energy efficiency penalties for capturing CO2 from iG-CLC coupled with subcritical, supercritical, ultra-supercritical or advanced ultra-supercritical steam cycles are 5.1%, 5.0%, 5.2% or 13.0%, respectively. The biomass-fired chemical looping combustion power plants also show low energy efficiency penalties (