Direct Conversion of Syngas into Light Olefins with Low CO2 Emission
Direct Conversion of Syngas into Light Olefins with Low CO2 Emission
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合成气直接转化为轻质烯烃，二氧化碳排放量低
DOI：
10.1021/acscatal.9b04629
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发表时间：
2020
期刊：
影响因子：
12.9
通讯作者：
Fan Weibin
中科院分区：
文献类型：
--
作者：
Wang Sen;Wang Pengfei;Shi Dezhi;He Shipei;Zhang Li;Yan Wenjun;Qin Zhangfeng;Li Junfen;Dong Mei;Wang Jianguo;Olsbye Unni;Fan Weibin
双功能催化剂上合成气直接转化制低碳烯烃的研究取得了重大进展，烃类中C2=-C4=选择性达到80%以上。然而，相对苛刻的反应条件（>380 °C，1.0MPa）导致产生大量的CO2（>40%），并且由于显著促进水煤气变换（WGS）反应和烯烃的过度氢化而得到低的烯烃/链烷烃（O/P）比（<10）。在此背景下，本文尝试开发高活性低温复合催化剂。发现锌-铈-锆固溶体（ZnxCe 2-yZryO 4）和SAPO-34混合物在300 ℃和1atm下分别显示出约7%、83%和23的CO转化率、烃中的轻质烯烃选择性和O/P比。更有趣的是，该催化剂表现出CH 4选择性和CO2排放低于5%和6%，分别。实验、原位光谱和理论计算结果的结合表明，在ZnxZr2.0O4中掺杂Ce通过增加羧酸盐中间物种的形成能垒而极大地抑制了WGS反应，但通过形成固溶体而增加了复合材料的表面氧空位浓度，因此，- 通过增强CO与催化剂的相互作用（这延长了HCO* 物质的C-O键）来改善在温和条件下转化合成气的催化活性。
Direct conversion of syngas into light olefins over bifunctional catalysts has made significant progress; the C2=–C4=selectivity in hydrocarbons reaches >80%. Nevertheless, a relatively harsh reaction condition (>380 °C, 1.0 MPa) led to producing large amounts of CO2(>40%) and gave a low olefin/paraffin (O/P) ratio (<10) as a result of significant promotion of water–gas shift (WGS) reaction and overhydrogenation of olefins. In this context, attempts are made here to develop a highly active low-temperature composite catalyst. It was found that a zinc–cerium–zirconium solid solution (ZnxCe2–yZryO4) and a SAPO-34 mixture showed CO conversion, light olefin selectivity in hydrocarbons, and O/P ratios of about 7%, 83%, and 23, respectively, at 300 °C and 1 atm. More interestingly, this catalyst showed CH4selectivity and CO2emission lower than 5 and 6%, respectively. A combination of experimental, in situ spectroscopy, and theoretical calculation results reveals that doping Ce in ZnxZr2.0O4greatly inhibits the WGS reaction by increasing the formation energy barrier of carboxylate intermediate species, but increases surface oxygen vacancy concentration of the composite through formation of a solid solution, and as a consequence, improving the catalytic activity for conversion of syngas at mild conditions by enhancing the interaction of CO with the catalyst, which elongates the C–O bond of the HCO* species.