Hydrogenation of Co2 to Light Olefins on Zz/Mnsapo-34@Si-2: Effect of Silicalite-2 Seeds on the Acidity and Catalytic Activity

Abstract

Light olefin is a primary building block for synthesis of various chemical intermediates and products. CZZ@ MnSAPO-34 and ZZ@MnSAPO-34 core-shell catalysts were synthesized for hydrogenation of CO 2 via Silicalite-2 seed-assisted in-situ hydrothermal synthesis method. The evaluation results showed that CZZ@MnSAPO-34 favors the generation of light alkanes, while ZZ@MnSAPO-34 benefits the production of light olefins. Further, the core-shell catalysts coating with Silicalite-2 shell denoted as ZZ@Si-2, CZZ@Si-2, and MnSAPO-34@Si-2, were synthesized by the in-situ hydrothermal synthesis technique. The microstructure, acidity and element distribution of above core-shell catalysts were investigated by XRD, NH 3 -TPD, and SEM-EDS analysis. The physically mixed ZZ/MnSAPO34@Si-2 exhibited the highest selectivity for light olefins up to 70.0 %, with CO 2 conversion of 17.3 % at 380 o C, 2.0 MPa, GHSV = 4800 h −1 . The weak acidity of the MnSAPO34@Si-2 zeolite favored the formation of light olefins via promoting C-C coupling of methanol intermediates, and inhibited the secondary hydrogenation. Meanwhile, the strong hydrogenation capacity of the CZZ elevated the selectivity to C 2 0 -C 4 0 (82.1%) on CZZ/MnSAPO-34@Si-2 catalyst.

Keywords: CO2 hydrogenation, light olefins, core-shell catalyst, SAPO-34, Silicalite-2