Conversion of dimethyl ether to liquid hydrocarbons over the nano-Pd-ZnHZSM-5 catalyst obtained by laser electrodispersion of the metal

BACKGROUND Palladium particles with a size of 2 nm were obtained by laser electrodispersion (LED) and used to prepare the Pd-ZnHZSM-5(LED) catalyst (Pd = 0.0005 wt%). The deposition of the LED palladium particles on the surface of ZnHZSM-5 provided a high dimethyl ether (DME) conversion into liquid hydrocarbons; the percentage of the unreacted intermediate (methanol) decreased by an order of magnitude and the selectivity for i-alkanes increased (more than 80 wt%). The Pd-ZnHZSM-5(LED) catalyst showed higher activity and selectivity than the traditional Pd-ZnHZSM-5 catalyst (impregnation). RESULTS The features of the catalytic action of Pd-ZnHZSM-5(LED) are associated with the high density of nanosized Pd-0 and Pd2+ phases on the ZnHZSM-5 surface. The LED particles are immersed in the surface of the zeolite to a maximum depth of 0.5 nm and do not penetrate deep into the pores of the zeolite. In Pd-ZnHZSM-5(LED), the zinc sites and palladium sites are separate. On Bronsted acid sites and zinc sites in the micropores of the zeolite occure target reactions. Part of arenes and unreacted alkenes exit the pores of zeolite are hydrogenated on the palladium. The product obtained on Pd-ZnHZSM-5(LED) is characterized by a high content of i-alkanes (more than 80 wt%) and a low content of arenes (no more than 5 wt%). CONCLUSION The results demonstrate the high promise of the LED method for the preparation of high-performance catalysts with ultra-low content of noble metal for conversion of oxygenates to synthetic liquid hydrocarbons with a high yield of i-alkanes and low yield of arenes. (c) 2022 Society of Chemical Industry (SCI).