Effects of encapsulation of Cr-ZnO and Cu-ZnO-A1₂O₃ catalysts with silicoaluminophosphates on dimethyl ether synthesis from syngas

Abstract

In this thesis, the experimental is divided into three parts, the catalyst mixture of Cr-ZnO catalyst and various types of zeolite, the main study of capsule catalyst, and the experimental design. The capsule catalyst was prepared by the new method named physical coating. The new coating catalysts are Cr-ZnO encapsulated by SAPO-46, and Cu-ZnO-A1₂O₃ encapsulated by SAPO-11. The capsule catalyst is simple and can be prepared without using any extra equipment. All catalysts have been characterized by SEM, EDS and XRD. All characterization techniques confirm the new capsule catalyst is compact. The total catalytic activities of capsule catalyst are higher than the conventional mixed catalyst. The reaction results show remarkably higher DME selectivity due to the spatial core-shell-like structure of capsule catalyst. The physical CuZnAl/SAPO11-PhyC catalyst showed extremely high DME selectivity at 90% and DME yield at 83%. Moreover, the study on the mixture catalyst of Cr-ZnO and SAPO-11 presented the best catalytic performance among those four types of molecular sieve (AlPO4-5, AlPO4-11, SAPO-11 and SAPO-46). The acidity properties and framework structure of zeolites were considered as the important factors. The optimum mathematical model was obtained from 2k factorial design among three variables, W/F ratio, reaction temperature and weight ratio of SAPO11: Cr-ZnO.