Insights into the development of greener mild zeolite dealumination routes applied to the hydrocracking of waste plastics

Abstract

This study highlights novel, energy-efficient, environmentally friendly and less time-consuming methods to dealuminate zeolites, by forced convective steaming and use of molecular CO2. Zeolites with comparable (or superior) physicochemical properties than those of traditional dealumination techniques were produced. All dealuminated zeolites were tested for the hydrocracking of high-density polyethylene, showing considerably high activity and selectivity for lighter oils, particularly gasoline. The forced convective steamed zeolite revealed to be the best, given its high number of silanol groups, acidity and porosity, and lower environmental impact. Furthermore, bi-functional Ni-loaded dealuminated zeolites showed good stability and ability to be regenerated. Therefore, it is possible to generate hierarchical zeolites by dealumination with physicochemical and catalytic properties comparable to their rival technologies, following green chemistry metrics. Given the relevance of hierarchical zeolites in sustainable routes to produce chemicals and fuels, the potential of application of these newly developed catalysts is highly promising and vast.