Catalytic oxy-cracking of petroleum coke on copper silicate for production of humic acids

Abstract

Oxy-cracking has been developed recently as an effective technology for converting residual feedstocks, like petroleum coke (petcoke), into valuable commodity products. This offers a new pathway for creating valuable products from solid waste hydrocarbon via oxygen incorporation onto the aromatic edges, where the oxy-cracked petcoke becomes soluble in water as oxygenated hydrocarbons. This fact enhances the tendency of petcoke to disaggregate, crack and convert into humic acid analogs, making them a valuable product at low temperatures. For practical purposes, and to favor high conversion and selectivity towards valuable product, energy consumption and capital investment should be minimized. In addition, low selectivity to CO2 emission is required to meet the global environmental regulations. Hence, introducing suitable heterogeneous catalysts to the oxy-cracking process could enhance the process conversion and selectivity. Therefore, in this study, a copper-silicate (CaCuSi4O10) material with nanocrystalline domains was introduced to enhance the selectivity and conversion of the oxy-cracking reaction of petroleum coke. The copper-silicate was synthesized in-house and characterized using BET, SEM, FTIR and XRD analyses. The catalytic activity of the prepared material was investigated by cracking the residual feedstock in an alkaline medium. The results showed that the catalyst enables the reaction to occur at a lower temperature with higher conversion as compared with the non-catalyzed reaction. An insignificant amount of CO2 was formed in the gas and liquid phases at high temperature as confirmed by GC and TOC analyses, respectively. The triangular lump kinetic model was implemented to describe the reaction pathways. The oxy-cracked products were found to be in the form of humic acid analogs with different contribution of the functionality groups such as carboxylic, carbonyl, and sulfonic acids as confirmed by FTIR analysis.