Direct synthesis of liquid hydrocarbons from CO 2 over CuZnAl/Zn-HZSM-5 combined catalyst in a single reactor

For the direct CO 2 conversion to liquid hydrocarbons, a combination of the CuZnAl/Al 2 O 3 and Zn-HZSM-5 catalysts was used, which made it possible to combine the oxygenates (methanol and dimethyl ether) synthesis and the subsequent formation of liquid hydrocarbons from them. With this purpose, the performance of CuZnAl/Al 2 O 3 metallic oxides was compared by using them in tandem with a Zn-HZSM-5. The catalysts were analysed by means of N 2 adsorption-desorption, XRD, XRF, H 2 -TPR and NH 3 -TPD. The CO 2 conversion was demonstrated to be controlled by controlling the mass ratio of CuZnAl:Al 2 O 3 in the Ox-component, the mass ratio of Ox:Zeo-components, the loading scheme of the Ox- and Zeo-components in the reactor, and the GHSV in reaction zone. The best results were achieved when this process was carried out in the tail-gas recirculation mode on a CuZnAl-Al 2 O 3 /Zn-HZSM-5 combined catalyst in a physical mixture form of oxide and zeolite components in a 1:1 wt ratio. At H 2 /CO 2 =3 molar ratio, 10 MPa, and 340 °C, the CO 2 conversion and selectivity for C 5+ –hydrocarbons were 20% and 47 wt% (78 wt% based on total hydrocarbons), respectively, for more than 60 h of operation. The selectivity for methane did not exceed 2 wt%. The liquid hydrocarbon mixture was characterized by a high content of isoalkanes (66 wt%), the durene content did not exceed 1 wt%.