$9.\_\_\_\_\_\_\_\_\_\_$ reforming uses a catalyst to rearrange molecular structures and enhance fuel quality.

$10.$ The alkylation process in petroleum refining involves combining olefins and isobutanes to produce $\_\_\_\_\_\_\_\_\_\_.$

$11.\_\_\_\_\_\_\_\_\_\_$ is a refining process where smaller molecules are combined to form larger ones to create synthetic rubber and other polymers.

$12.$ During isomerization, the structure of hydrocarbons is rearranged to improve the $\_\_\_\_\_\_\_\_\_\_$ of gasoline.