chemical conversion

chemical conversion

Chemical conversion

A chemical manufacturing process in which chemical transformation takes place, that is, the product differs chemically from the starting materials. Most chemical manufacturing processes consist of a sequence of steps, each of which involves making some sort of change in either chemical makeup, concentration, phase state, energy level, or a combination of these, in the materials passing through the particular step. If the changes are of a strictly physical nature (for example, mixing, distillation, drying, filtration, adsorption, condensation), the step is referred to as a unit operation. If the changes are of a chemical nature, where conversion from one chemical species to another takes place (for example, combustion, polymerization, chlorination, fermentation, reduction, hydrolysis), the step is called a unit process. Some steps involve both, for example, gas absorption with an accompanying chemical reaction in the liquid phase. The term chemical conversion is used not only in describing overall processes involving chemical transformation, but in certain contexts as a synonym for the term unit process. The chemical process industry as a whole has tended to favor the former usage, while the petroleum industry has favored the latter. See Chemical process industry, Unit processes

Another usage of the term chemical conversion is to define the percentage of reactants converted to products inside a chemical reactor or unit process. This quantitative usage is expressed as percent conversion per pass, in the case of reactors where unconverted reactants are recovered from the product stream and recycled to the reactor inlet. See Chemical engineering