High value utilization of inferior diesel for BTX production: Mechanisms, catalysts, conditions and challenges

Abstract

With the peak in diesel consumption and the impact of new energy in the coming years, research will be focused on the treatment of excess diesel. In addition, low carbon aromatics such as benzene, toluene, and xylene (BTX) are important chemical raw materials that will be in high demand in the next few years but are still in short supply. Thus, many researchers have proposed the use of excess diesel, especially the inferior diesel-like light cycle oil (LCO) to produce BTX. The hydrocracking process is typically used to convert LCO to BTX. To provide some guidance on this topic, this review summarizes the typical group compositions in LCO from different refineries, hydrocracking reaction mechanisms of aromatics and cycloalkanes in LCO, hydrocracking catalysts, improved hydrocracking conditions, related hydrocracking technologies, and future developments in the production of BTX. The amount of aromatics with different ring numbers in LCO has been clearly analyzed, and their part types have also been studied. However, some complex types of aromatics in LCO remain unknown. In addition, the hydrocracking mechanisms and pathways of aromatics in LCO to produce BTX have garnered great attention since the 1990s. Based on this, hydrocracking catalysts and related technologies have been developed by many institutions and corporations to convert aromatics to BTX; however, there are still some problems including an insufficient selectivity of BTX, low yield of liquid products, and excessive energy consumption. In the future, more advanced technologies can be applied to analyze all types of aromatics in LCO, which, along with the aid and application of computational chemistry tools, could help deepen the understanding of the reaction pathways of aromatics and develop more efficient catalysts by balancing the properties of the active phase and supporting the surmounting of current shortcomings. Owing to this high value utilization of inferior diesel, the upcoming problem of diesel surplus can be solved effectively, and the utilization of LCO to produce BTX is one possible path.