A method for preparing low-carbon olefins by catalytic synthesis gas conversion

Abstract

The invention discloses a method for preparing low-carbon olefins by catalyzing the conversion of synthesis gas. The method adopts a fixed-bed reactor, and the catalyst is loaded in the upper and lower stages. The upper stage is filled with FeZnNa catalyst, and the lower stage is filled with Naβ molecular sieve catalyst; Hydrogen reduces the FeZnNa catalyst, and then feeds synthesis gas for reaction. The preparation method of the catalyst used in the method of the present invention is simple, cheap, green and pollution-free. Compared with the traditional F-T synthesis, the catalyst is used to obviously improve the selectivity of low-carbon olefins, and at the same time in CH 4 In the case of no obvious increase in activity, C 5 + The product is cleaved. When tested under typical Fischer-Tropsch synthesis industrial conditions, the CO conversion rate is as high as 90%, and the low-carbon olefins (C 2 ＝ ~C 4 ＝ ) selectivity reaches about 50%, and has good industrial application prospect.

Description

technical field [0001] The invention belongs to the technical field of catalysis, in particular to a catalytic synthesis gas (CO+H 2 ) conversion method for preparing light olefins. Background technique [0002] At present, scholars have conducted extensive research on Fischer-Tropsch synthesis, but there are still many key technologies in product selectivity regulation that have not been broken through. How to break through the traditional ASF distribution restrictions and prepare products with a specific range of C atoms with high selectivity become a current research hotspot. [0003] Zhao et al. (Chem 2017,3,2,334-347) combined Na-Zn-Fe 5 C 2 Mixed with mesoporous HZSM-5 molecular sieve to catalyze the conversion of synthesis gas, but found that the products were biased towards aromatics rather than low-carbon olefins; Hadadzadeh et al. (Petrol Chem, 2010, 50(1):78-86) used alumina, molecular sieves and other carriers FeMn catalyst and H 2 After S post-treatment, it...

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Problems solved by technology

[0002] At present, scholars have conducted extensive research on Fischer-Tropsch synthesis, but there are still many key technologies in product selectivity regulation that have not been broken through. How to break through the traditional ASF distribution restrictions and prepare products with a specific range of C atoms with high selectivity become a current research hotspot

[0003] Zhao et al. (Chem 2017,3,2,334-347) combined Na-Zn-Fe 5 C 2 Mixed with mesoporous HZSM-5 molecular sieve to catalyze the conversion of synthesis gas, but found that the products were biased towards aromatics rather than low-carbon olefins; Hadadzadeh et al. (Petrol Chem, 2010, 50(1):78-86) used alumina, molecular sieves and other carriers FeMn catalyst and H 2 After S post-treatment, it was found that the S additive reduced the CH 4 Selectivity improves selectivity for lower olefins, but the process involves H 2 S treatment, the steps are relatively cumbersome; some scholars also prepare low-carbon olefins through a non-Fischer-Tropsch route, that is, coupling the traditional alcohol catalyst CuZnAl with mesoporous SAPO-34 molecular sieves to obtain low-carbon olefins (J Chem Technol Biotechnol.2015, 90 (3):415-422), but the reaction temperature does not match between the two, resulting in harsh reaction conditions