General types of renewable carbon sources have been considered to be suitable for production of drop-in biofuels with minimum oxygen content, fully compatible with conventional fuels. The...

The fast catalytic pyrolysis of polystyrene in the hydrocarbon medium (light and heavy cycle oil) over zeolite catalysts at 450–550 °C was investigated. The influence of reaction conditions (medium, temperature, vapor residence time, polystyrene concentration) on polymer conversion and product distribution was studied. It was found that the polymer conversion is close to 100%, while ethylbenzene, benzene, and toluene are the main products of its transformation. The maximum yield of ethylbenzene (80%) was achieved at 550 °C, vapor residence time 1–2 s, polystyrene concentration 10%, and heavy cycle oil as the medium. The influence of zeolite topology on product distribution was explored. The possible mechanism of polystyrene pyrolysis was proposed.

Methods for preparing zeolites with the particle size of 50–200 nm using mechanical milling on bead mills (top-down approach) are analyzed. The milling can be described by a first-order rate equation, but mathematical models allowing prediction of the particle size and degree of crystallinity of zeolite after milling, based on the process parameters, are still lacking. The milling is accompanied by degradation of the zeolite lattice, leading to a decrease in the zeolite crystallinity and activity in catalytic reactions. Recrystallization and dealumination may be promising ways to restore the zeolite structure after milling; in this case, the choice of the conditions for such posttreatment is of crucial importance. Evolution of textural and acid properties of zeolites in the course of milling is considered, and the effect of milling conditions on the catalytic activity of zeolites in various reactions is discussed. The main outcome from a decrease in the size of zeolite catalysts is an increase in their activity and a decrease in the deactivation rate.

The relevance of cracking diesel fractions into light olefins is determined by the strategic need to transition from a fuel-based refinery model to a petrochemical-based refinery model, growing global demand for polymers, and environmental sustainability requirements. The aim of this work is to explore the possibility of the selective production of light olefins from diesel fraction hydrocarbons. The pathways of high-temperature catalytic cracking of individual hydrocarbons that simulate the composition of diesel fractions over catalysts containing zeolites of various types (Y, ZSM-5, and β) have been studied. Maximum selectivity for light olefins in the cracking of aliphatic and alkylaromatic hydrocarbons was achieved using catalysts with the lowest activity in hydrogen transfer reactions. Based on the cracking of tetraline, it was shown that at temperatures above 625 °C, the kinetic control of the reactions under deep cracking conditions is predominant, whereas at lower temperatures, the selectivity is controlled by thermodynamics. Light olefin selectivity in the case of substituted aromatic and naphthenic hydrocarbons strongly depends on the porous structure of the catalyst. Conversion pathways for different classes of hydrocarbons under deep catalytic cracking conditions are proposed.