Effects of catalyst-to-oil ratio on distribution of catalytic pyrolysis gas products of Daqing atmospheric residue

The effects of catalyst-to-oil ratio on the distribution of catalytic pyrolysis gas products with two kinds of catalysts A and B were investigated in a confined fluidized bed reactor, taking Daqing atmospheric residue as the feedstock. The composition of catalytic pyrolysis gas was analyzed by using the HF6890 gas chromatogram. The results showed that the effects of catalyst-to-oil ratio on the yields of light olefins, hydrogen and methane yield varied with the types of catalysts. For the catalyst A, under the optimized operation conditions of reaction temperature at 700°C, water- to-oil ratio of 0.63 and residence time of 1.8 seconds, the total yield of light olefins is over 50 percent. With the increase of catalyst-oil weight ratio, the total yield of light olefins increased linearly. For the catalyst B, under the conditions of reaction temperature at 650°C, water-to-oil ratio of 0.75 and residence time of 1.7 seconds, the total yield of light olefins showed a maximum value of 44 percent with increasing catalyst-to-oil ratio. Experiment data were analyzed by the least square method, and the experiential formulas for expressing variations of the yields of ethylene, propylene, butylene and the total olefins with catalyst-to-oil ratio were obtained. Both the yields of cracking pyrolysis products and the reaction mechanism varied greatly with the types of catalysts.