Study on active site accessibility of heavy oil cracking

For heavy oil cracking, the pore structure of catalyst matrix should be accessible for primary cracking of the large hydrocarbon molecule so that the forming smaller molecules can transfer into zeolite channels and further convert to value added products over zeolite sites. However, the relationship between pore parameters, such as pore volume and distribution, and catalyst accessibility is not clear. A method for testing the active site accessibility of heavy oil cracking catalyst was developed through modification of widely used MAT equipment. The effects of pore distribution of catalyst matrix on the active site accessibility of several catalysts were tentatively in terms of bottoms conversion and strippable coke yield. The evaluation result showed that the yields of heavy cycle oil and strippable coke increased with the increase of the small pore matrix, and reduced over highly accessible matrix. The test results were well correlated with the commercial results.