HYDROGEN FORMATION, CHAIN-REACTIONS, AND INHIBITION DURING CRACKING REACTIONS OF HYDROCARBONS

Relationships between formation of hydrogen and molecular structure of the feed hydrocarbon have been studied for cracking processes on aluminosilicate catalysts. Saturated hydrocarbons with a hydrogen atom bonded to a tertiary carbon are generally more susceptible to yielding molecular hydrogen as an initial product, through interaction with a Brønsted site. However, exceptions to this trend can arise when steric interactions become important, as in some branched molecules. Good correlations were obtained for relative ease of hydrogen formation by comparing experimental data with results from simulations using molecular orbital calculations. Further correlations exist between production of molecular hydrogen and the observation of either inhibition or acceleration of the cracking reaction following initiation, which can be explained by considering hydride ion abstraction from the feed molecule as the common mechanistic feature. © 1990.