KINETICALLY BASED NMR METHOD OF MEASURING BLENDING OCTANE NUMBER OF OLEFINS

Olefins are highly nonlinear octane blenders so that standard GC analy ses are poor predictors of blend quality. Engine rating is the only wa y of measuring olefin octane number nonlinearity. It is thus not possi ble to rapidly assess the quality of the product obtained from an olef in-producing process-stream. An analysis of the kinetics of olefin com bustion in terms of mechanisms for depleting active radicals identitie s hydrogen abstraction from an allylic carbon as a factor that increas es resistance to knock. We can use NMR to find the allylic hydrogen fr action in a sample, and we show that this correlates with mixtures of olefins obtained during processing of the typical gaseous products of a cat-cracked stream. This simple application of NMR has the advantage s of quantitatively probing octane number on a sound chemical criterio n, as well as the fact that it is fast and requires only small amounts of sample so that process optimization for olefin quality on a small- scale microflow reactor can easily be carried out.