Effect of Steam Treatment on the Catalytic Performance of ZSM-5 in the Co-conversion of Methanol and n-Hexane to Aromatics

Steam pretreatment is a widely used method for modifying the acidity and structure of zeolites,thereby enhancing their catalytic properties.This study systematically investigated the effects of steam treatment on ZSM-5 zeolites at varying treatment temperatures and durations.The structural evolution of the catalysts was monitored using N2 adsorptiondesorption,X-ray diffraction,inductively coupled plasma optical emission spectroscopy,scanning electron microscopy,NH3 temperature-programmed desorption,in situ pyridine infrared spectroscopy,and thermogravimetric analysis.The characterization results revealed that mesopores were introduced into the ZSM-5 zeolite catalysts through dealumination induced using steam treatment at moderate temperatures(400 and 500℃).Moreover,compared with the parent catalyst,the steam-treated catalysts exhibited a lower amount of acid sites and relative crystallinity,while the n(Si)/n(Al)ratio increased.In the co-conversion of methanol and n-hexane in a fixed bed reactor at 400℃and 0.5 MPa(N2 atmosphere),with a weight hourly space velocity of 1 h−1 and a stoichiometric ratio of 1:1(CH3OH to n-hexane),the steam-treated catalysts displayed a prolonged catalyst lifetime.Particularly,the parent zeolite had a lifetime of 96 h,while the catalyst treated at 500℃for 12 h had a lifetime of up to 240 h.Additionally,the steam-treated catalysts maintained stable n-hexane conversion and improved aromatic selectivity.Notably,these treated catalysts exhibited a lower deactivation rate than the parent catalyst,and would be conducive to industrial scale-up production.

High‑Temperature Electrochemical Devices Based on Dense Ceramic Membranes for CO_(2) Conversion and Utilization

The adverse effects of global warming and climate change have driven the exploration of feasible routes for CO_(2) capture,storage,conversion and utilization.The processes related to CO_(2) conversion in high-temperature electrochemical devices(HTEDs)using dense ceramic membranes are particularly appealing due to the simultaneous realization of highly efficient CO_(2) conversion and value-added chemical production as well as the generation of electricity and storage of renewable energy in some cases.Currently,most studies are focused on the two processes,CO_(2) electrolysis and H2O/CO_(2) co-electrolysis in oxygen-conducting solid oxide electrolysis cell(O-SOEC)reactors.Less attention has been paid to other meaningful CO_(2)-conversion-related processes in HTEDs and systematic summary and analysis are currently not available.This review will fill the gap and classify the CO_(2)-conversion-related processes in HTEDs reported in recent years into four types accord-ing to the related reactions,including assisted CO_(2) reduction to CO,H2O and CO_(2) co-conversion,dry reforming of methane and CO_(2) hydrogenation.Firstly,an overview of the fundamentals of HTED processes is presented,and then the related mechanism and research progress of each type of reactions in different HTEDs are elucidated and concluded accordingly.The remaining major technical issues are also briefly introduced.Lastly,the main challenges and feasible solutions as well as the future prospects of HTEDs for CO_(2)-conversion-related processes are also discussed in this review.

Investigation on Co-Combustion Kinetics of Anthracite and Waste Plastics by Thermogravimetric Analysis

In order to effectively recycle resource for the benefit of the global environment, the utilization of waste plastics as auxiliary injectant for blast furnaces is becoming increasingly important. Combustion kinetics of plastics-coal blends with 0, 10%, 20% and 40% waste plastics (WP) are investigated separately by thermogravimetric analysis (TGA) from ambient temperature to 900 ℃ in air atmosphere. These blends are combusted at the heating rates of 5, 10 and 20 ℃/min. The results indicate that, with the increase of waste plastics content, the combustion processes of blends could be divided into one stage, two stages and three stages. The waste plastics content and heating rates have important effects on the main combustion processes of blends. With the increase of waste plastics content, the ignition temperature and the final combustion temperature of blends tend to decrease, while the combustion reaction becomes fiercer. With the increase of the heating rate, the ignition temperature, the mass loss rate of the peaks and the final combustion temperature of blends combustion tend to increase. The Flynn-Wall-Ozawa (FWO) iso-conversional method is used for the kinetic analysis of the main combustion process. The results indicate that, when the waste plastics content varied from 0 to 40%, the values of activation energy increase from 126.05 to 184.12 kJ /mol.