Active site accessibility of resid cracking catalysts

It is well understood that pore structure is important in designing FCC cat alysts. For residue cracking, the pore structure of catalyst matrix should be accessible for precracking the large hydrocarbon molecules so that the r esulting smaller molecules can transfer into the zeolite channels and can b e converted to value-added products over the zeolite sites. However, pore p arameters such as pore volume and pore size distribution are insufficient f or selecting an appropriate matrix. A method for testing the active site ac cessibility of resid cracking catalysts has been developed on currently wid ely used MAT equipped with the unstripped hydrocarbon burned off in place, with an online measurement of the CO2 and H2O that are produced, The effect of pore distribution of the FCC catalyst matrix on the active site accessi bility of several catalysts has been tested tentatively in terms of bottoms conversion and strippable coke yield. The results showed that the yields o f HCO and strippable coke increase when the matrix small pores increase, an d decrease when the catalyst matrixes are highly accessible. These test obs ervations are in agreement with commercial results.