What process involves using heat and catalysts to break large gas oil molecules into smaller ones?

The process involving the use of heat and catalysts to break large gas oil molecules into smaller ones is best defined as fluid catalytic cracking, which significantly enhances the efficiency of gasoline production from heavier crude oil fractions. This method utilizes a catalyst and high temperatures to crack large hydrocarbon molecules into smaller, more valuable products. The result is an increased yield of lighter, more useful hydrocarbons such as gasoline and diesel.

While hydrocracking also involves the use of heat and catalysts to break down heavier oils, it specifically incorporates hydrogen and focuses on producing fewer olefins, resulting in a different end product profile. Hydrotreating primarily aims to remove impurities like sulfur and nitrogen from the hydrocarbons rather than breaking them down into smaller molecules. Isomerization changes the structure of hydrocarbons to improve their octane rating but does not reduce their size by breaking bonds.

Thus, fluid catalytic cracking is accurately identified as the process that directly meets the criteria of using heat and catalysts to reduce larger gas oil molecules into smaller forms.