(A) study on the effect of binder on the catalytic performance of HZSM-5 catalyst for methanol-to-propylene (MTP) process

Abstract

Propylene is one of the key building block petrochemicals used as feedstock for a variety of polymers and intermediates. With the growing demand in propylene, the methanol-to-propylene (MTP) process has attracted a lot of attention as a promising alternative way for the production of propylene. HZSM-5 catalyst has been used for the MTP process. Since HZSM-5 catalysts are utilized in the bound form, a question should be asked whether the binder has any effects on the physical and chemical properties of HZSM-5 catalysts such as surface area, acidity, and further on their catalytic properties of the HZSM-5. Silica, alumina, and aluminum phosphate solution (APS) were used as binders for the HZSM-5 catalysts. The prepared catalysts were bound with various amounts of binders, and their catalytic performances were evaluated in the single and binary binders system. Physicochemical properties of the prepared samples were investigated and characterized with XRD, $N_2$ adsorption/desorption, $NH_3$-TPD, and compression test. Discussions were made on the effect of the binder on the physicochemical properties of HZSM-5 catalysts and their catalytic performance in MTP process. Silica and APS led to higher propylene selectivity when proper amount of APS and silica was introduced, compared with alumina and unbound HZSM-5. The increased propylene selectivity was attributed to the decrease in the acidic sites density as well as the weakening of acidic strength. The binary binders system was proposed to overcome insufficient mechanical strength of catalyst which was bound with small amount of binder but showed high propylene selectivity. It was found that the binary binders system was an effective way to improve mechanical strength while maintaining the high propylene selectivity. The proposed binder system should be a promising method for preparation of catalyst used in industrial process.