Primary Study On Catalytic Pyrolysis Of Different Feedstocks

As the demand for propylene growed strongly and the quality of crude oil became heavier and poorer, the technology producing light olifens from catalytic pyrolysis of heavy oil has been developing rapidly. There are many factors which can affect the catalytic pyrolysis reaction, including catalyst, operating conditions and technology, but the composition and property of feedstock are the most important factors which decide its product distribution and quality.In this study, the catalytic pyrolysis performances of different vacuum gas oils, different resids and deasphalted oil were investigated on ZDT-1 pilot scale FCC unit, the operating conditions were as follows: reaction temperature is 520℃, C/O is 10, and residence time is 1.4s. The feasibility of processing shale oil by catalytic pyrolysis technology was also investigated.H/C atomic ratio, which shows the hydrogen saturation and structure of average molecule, has an important influence on the catalytic pyrolysis of gas oil. As the H/C atomic ratio of gas oils increasing from 1.66 to 1.93, its conversion and products yields change linearly, the conversion increases by 18 percents, and propylene yield increases by 5.5 percents. Generalized empirical correlations were proposed for predicting catalytic pyrolysis products (LPG, gasoline, diesel, HCO, ethylene, propylene, butene) yields and conversion as functions of H/C atomic ratio of gas oils.SARA (Saturate, Aromatics, Resin and Asphaltene) composition also affects the catalytic pyrolysis of gas oil significantly. Gas oils with more saturates favor the production of dry gas and LPG, while gas oils with more resins favor the production of diesel and HCO. Generalized empirical correlations were proposed for predicting catalytic pyrolysis products yields and gasoline composition as functions of SARA composition of gas oils, and the contribution of saturate, aromatics and resin to products yields and gasoline composition were also calculated respectively.Different types of resids show different catalytic pyrolysis performance. Paraffin-base resid produce 2.3 percents lower propylene yield and 4.5 percents lower conversion than intermediate-base resid. Deasphalted oil shows good performance as feedsock of catalytic pyrolysis, which conversion approaches 88wt% and proprylene yield approaches 18.12wt%, but coke yield is too high, which approaches 14.66wt%.Primary study is investigated on catalytic pyrolysis of shale oil. Conversion is only 57.72wt% and propylene yield is only 11.69wt% by one-stage riser catalytic pyrolysis technology, while conversion increases by 20.23 percents, propylene, LPG, gasoline and diesel yield increase by 3.61,6.98,6.89 and 3.76 percents respectively by two-stage riser catalytic pyrolysis technology.