Solar-assisted two-stage catalytic membrane reactor for coupling CO_(2) splitting with methane oxidation reaction

A two-stage catalytic membrane reactor(CMR)that couples CO_(2) splitting with methane oxidation reactions was constructed based on an oxygen-permeable perovskite asymmetric membrane.The asymmetric membrane comprises a dense SrFe_(0.9)Ta_(0.1)O_(3-σ)(SFT)separation layer and a porous Sr_(0.9)(Fe_(0.9)Ta_(0.1))_(0.9)Cu_(0.1)O_(3-σ)(SFTC)catalytic layer.In thefirst stage reactor,a CO_(2) splitting reaction(CDS:2CO_(2)→2CO+O_(2))occurs at the SFTC catalytic layer.Subsequently,the O_(2) product is selectively extracted through the SFT separation layer to the permeated side for the methane combustion reaction(MCR),which provides an extremely low oxygen partial pressure to enhance the oxygen extraction.In the second stage,a Sr_(0.9)(Fe_(0.9)Ta_(0.1))_(0.9)Ni_(0.1)O_(3-σ)(SFTN)catalyst is employed to reform the products derived from MCR.The two-stage CMR design results in a remarkable 35.4%CO_(2) conversion for CDS at 900℃.The two-stage CMR was extended to a hollowfiber configuration combining with solar irradiation.The solar-assisted two-stage CMR can operate stably for over 50 h with a high hydrogen yield of 18.1 mL min^(-1) cm^(-2).These results provide a novel strategy for reducing CO_(2) emissions,suggesting potential avenues for the design of the high-performance CMRs and catalysts based on perovskite oxides in the future.

Design and Fabrication of Ceramic Catalytic Membrane Reactors for Green Chemical Engineering Applications

Catalytic membrane reactors(CMRs),which synergistically carry out separations and reactions,are expected to become a green and sustainable technology in chemical engineering.The use of ceramic membranes in CMRs is being widely considered because it permits reactions and separations to be carried out under harsh conditions in terms of both temperature and the chemical environment.This article presents the two most important types of CMRs:those based on dense mixed-conducting membranes for gas separation,and those based on porous ceramic membranes for heterogeneous catalytic processes.New developments in and innovative uses of both types of CMRs over the last decade are presented,along with an overview of our recent work in this field.Membrane reactor design,fabrication,and applications related to energy and environmental areas are highlighted.First,the configuration of membranes and membrane reactors are introduced for each of type of membrane reactor.Next,taking typical catalytic reactions as model systems,the design and optimization of CMRs are illustrated.Finally,challenges and difficulties in the process of industrializing the two types of CMRs are addressed,and a view of the future is outlined.

祁连山南麓高寒草甸2002~2016年生长季CO_(2)通量对气温日较差的响应

全球气候变化背景下气温日较差(amplitude of diurnal temperature,ADT)的减小将会对高寒生态系统的碳收支产生重要影响.基于涡度相关系统观测资料,研究祁连山南麓高寒草甸2002~2016年生长季(6~9月)ADT在日、月、年尺度上对CO2通量影响,为预测高寒草甸生态系统碳平衡对未来气候变化的响应具有重要参考价值.结果表明,2002~2016年的生长季中,最高气温(maximal air temperature,MaxTa)和最低气温(minimal air temperature,MinTa)呈先升高后降低的单峰变化趋势,ADT没有呈现明显的变化趋势.总初级生产力(gross primary production,GPP)和生态系统呼吸(ecosystem respiration,Re)呈先增加后降低的单峰趋势,净生态系统CO_(2)交换(net ecosystem exchange,NEE)呈先下降后上升的“V”型变化趋势.高寒草甸整个生长季总NEE、GPP和Re平均值分别为–230.4±17.3、668.8±25.5、438.3±27.5 g C m^(-2),表现为较强的碳汇.在月尺度和年尺度上,高寒草甸生长季ADT对NEE没有显著影响(P>0.05).在日尺度上,整个生长季的逐日NEE与ADT呈显著的二次曲线关系(P<0.001),阈值为19.8℃;但是,线性回归分析表明,在6~9月的日NEE与日ADT呈极显著负相关(P<0.001).整体上,仍能说明高寒草甸ADT的增大有利于生态系统的碳固持,暗示在未来气候变化背景下ADT的减小将会削弱高寒草甸生态系统的碳汇能力.