SAPO-34 and Zn/ZSM-5 synergistic catalysis of methanol to aromatics from light olefins

Abstract

The traditional one-step reaction of methanol to aromatics on ZSM-5 is a potential route for the synthesis of non-petroleum aromatics. Zn/ZSM-5 is widely used as the most common catalyst for the methanol to aromatics reaction. However, due to the generation of by-products such as alkanes, carbon atoms are consumed, and it is still difficult to obtain high aromatic selectivity. In this work, in order to improve the aromatic selectivity, the traditional one-step reaction is divided into two steps: methanol to light olefins and aromatization of light olefins. SAPO-34 and Zn/ZSM-5 are designed as catalysts for the above two-step reaction respectively. Through a study of the loading methods and loading ratios of the above two catalysts, it is found that the top-down loading mode of SAPO-34 and Zn/ZSM-5 can obtain higher aromatic selectivity than the one-step reaction. The reason for the improvement of aromatic selectivity is that the light olefins generated by SAPO-34, as the intermediate of methanol aromatization, promote the generation of aromatics on the Zn/ZSM-5 catalyst. The acidity and reaction temperature of the two catalysts are further optimized to improve the reaction performance. Under the conditions of 673 K and a loading ratio of SAPO-34 to Zn/ZSM-5 of 1 : 9, the selectivity of aromatics and BTX in the two-step reaction can reach 80.0% and 56.7% respectively. It is much higher than 64.9% and 32.0% in the one-step reaction by filling Zn/ZSM-5 only. This reaction method provides a new way for the production of aromatics and BTX and shows great development potential.