Effects of Acid Treatment of SAPO-34 on the Catalytic Lifetime and Light Olefin Selectivity during DTO Reaction

Abstract

Effects of the post-acid treatment of SAPO-34 sample by hydrochloric acid were investigated to enhance the catalytic performance in DTO reaction. Uniformly sized SAPO-34 samples with cubic-like morphology were prepared by hydrothermal method using TEAOH and DEA as the structure directing agents. It was modified in terms of the HCl concentration and treating time. As a result, the total surface area and micropore volume for the well modified samples increased and the total acid site was somewhat decreased along with the erosion of the external surface. Especially, the catalytic lifetime and light olefins selectivity for acid treated SAPO-0.2 M (3 h) samples were considerably enhanced compared with those of untreated SAPO-34 samples. It indicates that the deactivation by coke formation proceeds mainly at the pore entrance on the external surface. Therefore, the acid treatment was confirmed to be a simple method which can significantly improve the catalytic performance by modifying the external surface of SAPO-34 catalyst.

Effect of Thermal, Acid, and Alkaline Treatments over SAPO-34 and Its Agglomerated Catalysts: Property Modification and Methanol-to-Olefin Reaction Performance

“…Despite the complexity of this task, there are several strategies available to circumvent the very rapid coke formation in the MTO reaction. These strategies include water cofeeding, ,, the design of deactivation-resistant catalysts, or catalyst modification through either incorporation of other metals or via thermal, acid, or basic treatments. − These last groups of modifications are of special interest because they are easy to perform and modify some of the most relevant characteristics of the materials (thermal stability, acid site distribution and strength, and elemental composition).…”