RELATIVE REACTIVITIES OF ALKANES IN CATALYTIC CRACKING REACTIONS

A microtechnique was developed for measuring relative reactivities of various alkanes in their catalytic cracking reactions over heterogeneous catalysts under mild conditions, 200-400°C. With the technique, a small quantity of a catalyst, 0.01-0.05 g, is placed in the evaporator of a gas chromatograph. Injection of a small quantity of a liquid hydrocarbon, 0.05-0.2 μl, in the evaporator brings about the cracking reaction. The reaction products and the unreacted feed enter the chromatographic column and are analyzed. The proposed method allows repetitive cracking of various feeds over the same load of a catalyst. The kinetic treatment of the experimental data accounts for a gradual catalyst deterioration with time. The technique was used to measure relative reactivities (with respect to the reactivity of 2-methylnonane) of various alkanes in the C8C17 range. The comparison provided the data for the analysis of alkane reactivities as a function of their carbon atom number and the number and types of substituents, as well as the temperature and catalyst composition effects. © 1990.