The process was further developed by two MIT engineers, Warren K. Lewis and Edwin R. Gilliland, under contract to Standard Oil of New Jersey, now ExxonMobil. They developed the process into fluid catalytic cracking, which solved the problem of having to shut down the process to burn the coke off the catalyst by using a continuously circulating fluidized catalyst made of a fine zeolite powder. This process is still in widespread use, especially in the US where gasoline is in high demand compared to other refined products.