Low-Temperature Catalytic Cracking of Heavy Feedstock Optimized by Response Surface Method

Upgrading of cracked PFO (Pyrolysis fuel oil) for the production of liquid fuels, such as gasoline and light gasoil, was carried out in a semi-batch reactor. Two different kinds of mesoporous and microporous catalysts, MCM-41 and ZSM-5, were used. Modification methods, such as ion exchange and impregnation with Fe and Ti, were done for tuning the acidity of the catalyst. XRD, FT-IR, and XRF analyzes were used to identify the structure and composition of the catalysts. Among the catalysts used in low-temperature catalytic cracking of cracked PFO at a moderate temperature (380 °C), 3%Ti/H-MCM-41 showed the best catalytic performance. After choosing the best catalyst, an experimental design was carried out using a response surface method with a five-level central composite design model. The effect of 3 main parameters, i.e. reaction temperature (360-400 °C), catalyst to feed ratio (0.04-0.1), and loading of Ti (0-5%) was investigated on liquid productivity and light olefin production. Design Expert software was used to maximize the sum of liquid yield and olefins in the gas. In optimum condition (380 °C) with the ratio of 0.1 g/g catalyst to feed over 2.5%Ti/H-MCM-41, the wt. % of liquid, gas, and solid products are 80 wt. %, 10 wt. %, and 10 wt. %, respectively. At this condition, 26 wt. % of liquid product was in the range of gasoline (C5-C10) and the rest (i.e. C11+) was considered in the range of light gas oil. Light olefins of the obtained gas products were about 2.74 wt. %.