A surface-inactivated catalyst composition comprising acidic porous crystalline material, e.g., ZSM-23, having active internal Bronsted acid sites and containing coke-inactivated external acid sites is prepared by contacting the catalyst under high pressure coking conditions, e.g. 800 psig. The catalyst may be used for organic compound conversion, e.g., oligomerization of lower olefins to produce distillate boiling range materials having reduced methyl branching and increased cetane number.