Adsorption enhanced steam reforming of methanol for hydrogen generation in conjunction with fuel cell: Process design and reactor dynamics

Local Green Power Supply Plants Based on Alcohol Regenerative Gas Turbines: Economic and Environmental Aspects

Growing economies need green and renewable energy. Their financial development can reduce energy consumption (through energy-efficient technologies) and replace fossil fuels with renewable ones. Gas turbine engines are widely used in transport and industry. To improve their economic attractiveness and to reduce harmful emissions, including greenhouse gases, alternative fuels and waste heat recovery technologies can be used. A promising direction is the use of alcohol and thermo-chemical recuperation. The purpose of this study is to estimate the economic efficiency and carbon dioxide emissions of an alcohol-fueled regenerative gas turbine engine with thermo-chemical recuperation. The carbon dioxide emissions have been determined using engine efficiency, fuel properties, as well as life cycle analysis. The engine efficiency was maximized by varying the water/alcohol ratio. To evaluate steam fuel reforming for a certain engine, a conversion performance factor has been suggested. At the optimal water/methanol ratio of 3.075 this technology can increase efficiency by 4% and reduce tank-to-wake emission by 80%. In the last 6 months of 2019, methanol prices were promising for power and cogeneration plants in remote locations. The policy recommendation is that local authorities should pay attention to alcohol fuel and advanced turbines to curb the adverse effects of burning petroleum fuel on economic growth and the environment.

Comparative Study of Methanol Activation by Different Small Mixed Silicon Clusters Si2M with M = H, Li, Na, Cu, and Ag

High-accuracy quantum chemical calculations were carried out to study the mechanisms and catalytic abilities of various mixed silicon species Si₂M with M = H, Li, Na, Cu, and Ag toward the first step of methanol activation reaction. Standard heats of formation of these small triatomic Si clusters were determined. Potential-energy profiles were constructed using the coupled-cluster theory with extrapolation to complete basis set CCSD(T)/CBS, and CCSD(T)/aug-cc-pVTZ-PP for Si₂Cu and Si₂Ag. The most stable complexes generated by the interaction of methanol with the mixed clusters Si₂M possess low-spin states and mainly stem from an M-O connection in preference to Si-O interaction, except for the Si₂H case. In two competitive pathways including O-H and C-H bond breakings, the cleavage of the O-H bond in the presence of all clusters studied becomes predominant. Of the mixed clusters Si₂M considered, the dissociation pathways of both O-H and C-H bonds with Si₂Li turns out to have the lowest energy barriers. The most remarkable finding is the absence of the overall energy barrier for the O-H cleavage with the assistance of Si₂Li. The breaking of O-H and C-H bonds with the assistance of Si₂H, Si₂Li, and Si₂Na is kinetically preferred with respect to the Si₂Cu and Si₂Ag cases, apart from the case of Si₂Na for O-H cleavage. In comparison with other transition-metal clusters with the same size, such as Cu₃, Pt₃, and PtAu₂, the energy barriers for the O-H bond activation in the presence of small Si species, especially Si₂H and Si₂Li, are found to be lower. Consequently, these small mixed silicon clusters can be regarded as promising alternatives for the expensive metal-based catalysts currently used for methanol activation particularly and other dehydrogenation processes of organic compounds. The present study also suggests a further extensive search for other doped silicon clusters as efficient and more realistic gas-phase catalysts for important dehydrogenation processes in such a way that they can be experimentally prepared and implemented.

Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope-Labeled Reactants

The low-temperature ethanol steam reforming (ESR) reaction mechanism over a supported Rh/Pt catalyst has been investigated using isotope-labeled EtOH and H2 O. Through strategic isotope labeling, all nonhydrogen atoms were distinct from one another, and allowed an unprecedented level of understanding of the dominant reaction pathways. All combinations of isotope- and non-isotope-labeled atoms were detected in the products, thus there are multiple pathways involved in H2 , CO, CO2 , CH4 , C2 H4 , and C2 H6 product formation. Both the recombination of C species on the surface of the catalyst and preservation of the C-C bond within ethanol are responsible for C2 product formation. Ethylene is not detected until conversion drops below 100 % at t=1.25 h. Also, quantitatively, 57 % of the observed ethylene is formed directly through ethanol dehydration. Finally there is clear evidence to show that oxygen in the SiO2 -ZrO2 support constitutes 10 % of the CO formed during the reaction.

Catalytic Reforming of Oxygenates: State of the Art and Future Prospects

This Review describes recent advances in the design, synthesis, reactivity, selectivity, structural, and electronic properties of the catalysts for reforming of a variety of oxygenates (e.g., from simple monoalcohols to higher polyols, then to sugars, phenols, and finally complicated mixtures like bio-oil). A comprehensive exploration of the structure-activity relationship in catalytic reforming of oxygenates is carried out, assisted by state-of-the-art characterization techniques and computational tools. Critical emphasis has been given on the mechanisms of these heterogeneous-catalyzed reactions and especially on the nature of the active catalytic sites and reaction pathways. Similarities and differences (reaction mechanisms, design and synthesis of catalysts, as well as catalytic systems) in the reforming process of these oxygenates will also be discussed. A critical overview is then provided regarding the challenges and opportunities for research in this area with a focus on the roles that systems of heterogeneous catalysis, reaction engineering, and materials science can play in the near future. This Review aims to present insights into the intrinsic mechanism involved in catalytic reforming and provides guidance to the development of novel catalysts and processes for the efficient utilization of oxygenates for energy and environmental purposes.