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The deployment of fossil resources such as petroleum, coal and natural gas to produce fuels and chemicals has resulted in excessive carbon dioxide (CO2) emissions and serious environmental issues. The implementation of CO2 utilization as a raw material for synthesis of fuels and chemicals has potential to reduce CO2 emissions and close the carbon cycle. Cyclic carbonates, materials used as building blocks for polymers or green solvents in batteries, can be synthesized from CO2 and alkylene oxides. Although a variety of catalysts have been synthesized to activate CO2 and alkylene oxides for transformation into cyclic carbonates, either the catalytic efficiency is low or the catalyst cost is high. In the present work, we report a hierarchical porous metallized poly-melamine-formaldehyde (PMF) polymer catalyst that has a 100-fold monomer cost reduction and six- to several hundred-fold activity enhancement compared to the state-of-the-art catalysts for propylene carbonate synthesis from epoxide and CO2 under the same reaction conditions. The hierarchically interconnected macro-, meso- and micro-pore structures in PMF that are formed via one-step high internal phase emulsion polymerization facilitate mass transport and accessibility to active sites. The high density of aminal groups and triazine rings in PMF provides multiple sites for CO2 adsorption and the subsequent reaction with epoxide. The unprecedented low-cost and high-efficiency of metallized PMF as well as the simplicity in its synthesis exhibit great potential in the synthesis of cyclic carbonates for the chemical and plastics industries. [ABSTRACT FROM AUTHOR]

Direct non-oxidative methane coupling (NMC) is one of the promising pathways for methane upgrading into value-added olefin and aromatic hydrocarbons. The silica-supported iron (i.e., Fe/SiO 2) catalyst has been reported effective for NMC, but the effects of silica support on the catalyst property and NMC performance have rarely been explored. In this work, we prepared a vitreous silica-supported iron (Fe/SiO 2 -V) catalyst by flame fusion of a mixture of quartz silica and fayalite. The physicochemical properties and NMC performance of the as-prepared catalysts were measured. Compared to crystalline cristobalite support in Fe/SiO 2 catalyst that has been studied previously, vitreous silica support has disordered Si-O bonds and structural defects, enabling better iron dispersion and more vital metal-support interaction. The as-prepared Fe/SiO 2 -V catalyst had a shorter induction period in methane activation and lower coke yield in NMC. The increase in iron concentration in Fe/SiO 2 -V catalysts elongated the catalyst induction period and promoted aromatics and coke formation. The coke type of the spent Fe/SiO 2 -V catalyst is more uniform than the cristobalite-supported iron catalyst. [Display omitted] • Vitreous silica-supported iron catalysts were prepared by an oxyhydrogen flame fusion method. • The amorphous vitreous silica support contains disordered and defective Si-O bonds. • Iron has higher dispersion and more uniform bonding in the vitreous silica support. • Vitreous silica-supported iron enabled fast methane activation and low coking in NMC. • Increase in iron loading in vitreous silica support promoted aromatics formation. [ABSTRACT FROM AUTHOR]

Direct non-oxidative methane conversion (DNMC) has been recognized as a single-step technology that directly converts methane into olefins and higher hydrocarbons. High reaction temperature and low catalyst durability, resulting from the endothermic reaction and coke deposition, are two main challenges. We show that a millisecond catalytic wall reactor enables stable methane conversion, C 2+ selectivity, coke yield, and long-term durability. These effects originate from initiation of the DNMC on a reactor wall and maintenance of the reaction by gas-phase chemistry within the reactor compartment. The results obtained under various temperatures and gas flow rates form a basis for optimizing the process towards lighter C 2 or heavier aromatic products. A process simulation was done by Aspen Plus to understand the practical implications of this reactor in DNMC. High carbon and thermal efficiencies and low cost of the reactor materials are realized, indicating the technoeconomic viability of this DNMC technology., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)