HYDROCARBON CONVERSION TO PROPYLENE WITH HIGH SILICA MEDIUM PORE ZEOLITE CATALYSTS

摘要

The invention provides a method for converting a hydrocarbon feedstock to propylene comprising: contacting an olefinic hydrocarbon feedstock boiling in the naphtha range with a catalyst comprising a zeolitic catalyst selected from the group consisting of medium pore zeolites having a ratio of silica to alumina above 200 and pore diameter less than 0.7 nm under cracking conditions to selectively produce propylene. The preferred catalyst comprises a zeolite having an 8, 10, or 12 membered ring pore structure. The preferred catalysts are selected from the group consisting of zeolites from the families: MFI, MEL, MTW, TON, MTT, FER, MFS, and the zeolites ZSM-21, ZSM-38 and ZSM-48. Preferably the method is carried out to produce propylene with greater than 50 % specificity, more preferably, the propylene to butylene ratio is at least 2:1 or a propylene to ethylene ratio of at least 4:1. The olefinic hydrocarbon feedstock consists essentially of hydrocarbons boiling within the range of 18~ to 220 ~C (65 ~F to 430 ~F). The olefinic hydrocarbon feedstock comprises from about 10 wt.% to about 70 wt.% olefins. Preferably the olefinic hydrocarbon feedstock comprises from about 5 wt.% to about 35 wt.% paraffins. The catalyst is contacted in the range in the range of 400 ~C to 700 ~C, a weight hourly space velocity ("WHSV") of 1 to 1,000 hr-1 and a pressure of 0.1 to 30 atm. absolute.