Hydrogenation of CO2 to light olefins on CuZnZr@(Zn-)SAPO-34 catalysts: Strategy for product distribution

Composite catalysts containing CuZnZr(CZZ) and SAPO-34 were prepared and applied to the hydrogenation of CO2 to light olefins via the tandem reactions of methanol synthesis and methanol to olefins. The product selectivity was significantly affected by the composite methods, mass ratio of CZZ and SAPO-34 and the acid density of SAPO-34. Compared with physically mixed CZZ/SAPO-34, assembled core-shell CZZ@SAPO-34 increased the selectivity of olefins and inhibited CH4 formation, due to reduced contact interface and hydrogenation ability on the metal sites. Furthermore, reducing the acidity of SAPO-34 by Zn addition greatly restrained secondary reactions of the primary olefins. A high olefin selectivity of 72% was achieved over CZZ@Zn-SAPO-34 (4/1) at H-2 /CO2 of 3, 6000 h(-1), 400 degrees C and 2 MPa. Because the concentration of intermediate methanol remained low level during the reaction and small amount of CZZ was doped into Zn-SAPO-34, a large amount of C-3 and C4 hydrocarbons were formed owing to the hydrogenation and hydrogen transfer reactions of primary C-2 -C-4 olefins.