Direct Conversion of Syngas into Light Olefins with Low CO2 Emission,ACS Catalysis

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Direct Conversion of Syngas into Light Olefins with Low CO2 Emission
ACS Catalysis ( IF 11.3 ) Pub Date : 2020-01-21 , DOI: 10.1021/acscatal.9b04629
Sen Wang ₁ , Pengfei Wang ₁ , Dezhi Shi _{1,

2} , Shipei He _{1,

2} , Li Zhang _{1,

2} , Wenjun Yan ₁ , Zhangfeng Qin ₁ , Junfen Li ₁ , Mei Dong ₁ , Jianguo Wang _{1,

2} , Unni Olsbye ₃ , Weibin Fan ₁

Affiliation

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 (Zn_xCe_2–yZr_yO₄) 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 CH₄ selectivity and CO₂ emission lower than 5 and 6%, respectively. A combination of experimental, in situ spectroscopy, and theoretical calculation results reveals that doping Ce in Zn_xZr_2.0O₄ greatly 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.

中文翻译：

将合成气直接转化为低CO ₂排放的轻烯烃

通过双功能催化剂将合成气直接转化为轻质烯烃已取得重大进展。C ₂⁼ –C ₄⁼在烃中的选择性达到> 80％。但是，相对苛刻的反应条件（> 380°C，1.0 MPa）导致产生大量的CO ₂（> 40％），并且由于以下原因导致了较低的烯烃/石蜡（O / P）比（<10）。大大促进了水煤气变换（WGS）反应和烯烃的过度氢化。在这种情况下，这里尝试开发高活性的低温复合催化剂。发现锌-铈-锆固溶体（Zn _x Ce _{2- y} Zr _y O ₄）和SAPO-34混合物在300°C和1个大气压下分别显示出CO转化率，在烃中的轻烯烃选择性以及O / P比分别约为7％，83％和23。更有趣的是，该催化剂的CH ₄选择性和CO ₂排放分别低于5和6％。实验，原位光谱和理论计算结果的结合表明，Zn _x Zr _2.0 O ₄中掺杂铈通过增加羧酸盐中间体物种的形成能垒极大地抑制了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，通过提高温度提高了在温和条件下转化合成气的催化活性CO与催化剂的相互作用，延长了HCO *物种的C–O键。

更新日期：2020-01-22

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