Thermodynamic appraisal of naphtha to light olefins based on different reaction pathways and independent chemical reactions

Abstract

Catalytic pyrolysis of naphtha involves a series of complex acid-catalyzed reaction pathways, that significantly affect the distribution of pyrolysis products. To determine the optimal catalyst characteristics for enhancing light olefins, n-pentane and cyclopentane were used as model compounds to analyze cracking pathways, including the protolytic, dehydrogenation, and hydrogen transfer cracking pathways based on thermodynamic methods. The effects of temperature and pressure on cracking pathways are also discussed. The results indicate that the optimum cracking pathways for enhancing light olefins were the dehydrogenation cracking pathway of n-paraffins and the protolytic cracking pathway of cycloparaffin. Therefore, the design and development of catalysts with dehydrogenation and acidic active sites have become particularly important for the efficient conversion of n/cyclo-paraffins. Furthermore, a thermodynamic equilibrium model based on one set of independent reactions in the catalytic pyrolysis process was established to analyze the effects of the operating conditions on the equilibrium yields. Under these operating conditions, as determined by applying the thermodynamic equilibrium model, the production of light olefins can be tailored.