Hybrid Nanocarbon-Zeolite Catalysts for Hydrocracking Applications

Abstract

Hydrocracking, a process by which heavy chemicals are converted into lighter and value-added products, is an important reaction in the petrochemical industry. Hydrocracking is typically carried out in the presence of a bi-functional catalyst consisting of an acidic support, to provide the cracking function, and dispersed metal nanoparticles, to provide both the hydrogenation and dehydrogenation functions. Moreover, carbon-zeolite composites seem to be potentially efficient catalysts for hydrocracking; where the CNTs and Graphene provide extra thermal stability and conductivity to the traditional catalyst, as well as, large specific surface area. To further enhance the performance of existing hydrocracking catalysts, this work aims to develop a novel approach for the synthesis of hybrid catalysts composed of zeolite Y, metal nanoparticles (Ni, W) and nano-carbon material (carbon nanotubes CNTs, graphene nanoplatelets GNPs). The catalysts are characterized using various material and chemical characterization tools, and assessed for their performance in hydrocracking of heptane at two temperatures, 350oC and 400oC. Initially, monometallic (Ni) and bimetallic (Ni, W) catalysts are prepared, in which metal nanoparticles are deposited on zeolite Y support with a range of different Si/Al ratios. After catalytic testing, the best performing catalyst compositions, in terms of metal loading and support, are further examined for incorporating CNTs and GNPs on them. Novel transient kinetic rate and isothermal titration with oxygen experiments, as well as, in-situ acidity measurements under reaction conditions were shown to be useful tools in revealing valuable information about the catalyst's activity and resistance against deactivation. The results showed enhanced performance for nano-carbon containing catalysts with higher conversion and stability with time-on-stream, as well as lower amount of carbonaceous species formation upon hydrocracking. Finally, catalyst regeneration studies through oxidation at 450oC were performed on selected compositions in order to assess the reusability of the catalysts over 3 cycles. The study showed that the CNTs and GNPs were stable during the regeneration process, and can be reused for at least 3 hydrocracking cycles with minor reduction in catalytic activity.

Date of Award	Dec 2021
Original language	American English