Catalytic Dehydrogenation of Ethane: A Mini Review of Recent Advances and Perspective of Chemical Looping Technology

Self-Assembly Dual Active Site Nanocomposite Anode Ce0.6Mn0.3Fe0.1O2-δ/NiFe/MnOx for Electrooxidative Dehydrogenation of Ethane to Ethylene

As the demand for ethylene grows continuously in industry, conversion of ethane to ethylene has become more and more important; however, it still faces fundamental challenges of low ethane conversion, low ethylene selectivity, overoxidation, and instability of catalysts. Electrooxidative dehydrogenation of ethane (EODHE) in a solid oxide electrolysis cell (SOEC) is an alternative process. Here, a multiphase oxide Ce0.6Mn0.3Fe0.1O2-δ-NiFe-MnOx has been fabricated by a self-assembly process and utilized as the SOEC anode material for EODHE. The highest ethane conversions reached 52.23% with 94.11% ethylene selectivity at the anode side and CO with 10.9 mL min-1 cm-2 at the cathode side, at 1.8 V at 700 °C. The remarkable electrooxidative performance of CMF-NiFe-MnOx is ascribed to the NiFe alloy and MnOx nanoparticles and improvement of the concentration of oxygen vacancies within the fluorite substrate, generating dual active sites for C2H6 adsorption, dehydrogenation, and selective transformation of hydrogen without overoxidizing the ethylene generated. Such a tailored strategy achieves no significant degradation observed after 120 h of operation and constitutes a promising basis for EODHE.

Ion-Conducting Ceramic Membrane Reactors for the Conversion of Chemicals

Ion-conducting ceramic membranes, such as mixed oxygen ionic and electronic conducting (MIEC) membranes and mixed proton-electron conducting (MPEC) membranes, have the potential for absolute selectivity for specific gases at high temperatures. By utilizing these membranes in membrane reactors, it is possible to combine reaction and separation processes into one unit, leading to a reduction in by-product formation and enabling the use of thermal effects to achieve efficient and sustainable chemical production. As a result, membrane reactors show great promise in the production of various chemicals and fuels. This paper provides an overview of recent developments in dense ceramic catalytic membrane reactors and their potential for chemical production. This review covers different types of membrane reactors and their principles, advantages, disadvantages, and key issues. The paper also discusses the configuration and design of catalytic membrane reactors. Finally, the paper offers insights into the challenges of scaling up membrane reactors from experimental stages to practical applications.

Utilization of CO2-Available Organocatalysts for Reactions with Industrially Important Epoxides

Recent knowledge in chemistry has enabled the material utilization of greenhouse gas (CO2) for the production of organic carbonates using mild reaction conditions. Organic carbonates, especially cyclic carbonates, are applicable as green solvents, electrolytes in batteries, feedstock for fine chemicals and monomers for polycarbonate production. This review summarizes new developments in the ring opening of epoxides with subsequent CO2-based formation of cyclic carbonates. The review highlights recent and major developments for sustainable CO2 conversion from 2000 to the end of 2021 abstracted by Web of Science. The syntheses of epoxides, especially from bio-based raw materials, will be summarized, such as the types of raw material (vegetable oils or their esters) and the reaction conditions. The aim of this review is also to summarize and to compare the types of homogeneous non-metallic catalysts. The three reaction mechanisms for cyclic carbonate formation are presented, namely activation of the epoxide ring, CO2 activation and dual activation. Usually most effective catalysts described in the literature consist of powerful sources of nucleophile such as onium salt, of hydrogen bond donors and of tertiary amines used to combine epoxide activation for facile epoxide ring opening and CO2 activation for the subsequent smooth addition reaction and ring closure. The most active catalytic systems are capable of activating even internal epoxides such as epoxidized unsaturated fatty acid derivatives for the cycloaddition of CO2 under relatively mild conditions. In case of terminal epoxides such as epichlorohydrin, the effective utilization of diluted sources of CO2 such as flue gas is possible using the most active organocatalysts even at ambient pressure.

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H₂/CO₂, H₂/C₂H₆, and H₂/C₃H₈, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies.