Modification of Zeolite Framework to Introduce Mesoporosity for Catalytic Upgrading of Heavy Petrochemicals

Abstract

The world’s demand for light fuels such as gasoline, kerosene and gas oil has increased due to massive growth in world population, industry and economy. Fluid catalytic cracking (FCC) using Y zeolites is one of the most important conversion processes in petroleum refining industry. The FCC process is used to convert bulky hydrocarbons in heavy oil into more valuable products, especially gasoline range organics. Accordingly, research into the development and optimisation and improvement the FCC processes is of paramount important to sustain the continuous support for the global demand. Y zeolites are a class of aluminosilicate porous catalysts of great importance in the FCC processes due to their unique properties such as strong acidity, high surface area, uniform micropore sizes (and hence good shape selectivity) and high (hydro)thermal stability. Nevertheless, their potential is exploited partially due to accessibility and diffusion limitations imposed by their microporous structures. This PhD project focuses on the development of mesoporous Y zeolites by novel, cost-effective and sustainable strategies. The merits of utilisation of mesoporous Y zeolites in practical applications are generally the reduction in the mass transfer resistance of the bulky molecules to and within the framework, and thus alleviating the deactivation issues. Over the course of this PhD research, the fundamental aspects of Y zeolites, different modification strategies for creating mesoporous Y zeolites as well as their catalytic applications have been investigated. For example, the synthesis of mesoporous Y zeolite via the hard templating route using sustainable template of nanocrystalline cellulose was established to deliver the Y zeolites of high mesoporosity (external surface area >300 m2 g−1). The catalytic reaction (cracking of 1,3,5 triisopropyl benzene, TiPBz) over the mesoporous Y zeolite was carried out, and the results showed the improvement in the catalytic conversion and product selectivities compared with the parent Y zeolite. A new post-synthesis treatment method intensified by the microwave irradiation was also invented for preparing mesoporous Y zeolites. By using the developed microwave method, mesoporous Y zeolites could be produced in a temperature range of 50–100 °C with a short treatment time of minutes. The produced mesoporous Y zeolites presented a high mesopore area (external surface area) in a range of 306–571 square meter per gram with the micropore area of 415–804 square meter per gram. The well-developed mesoporosity was translated into excellent catalytic performance in the cracking of TiPBz (TiPBz conversion of ~98%) and aldol condensation reaction (1-heptanal conversion of 80%) for producing bulky molecules. Additionally, an experimental comparative study between inter-crystal and intra-crystalline mesoporous structure including preparations, full characterisation, catalytic assessments and economic analysis was made. Finally, a new kind of pure mesoporous aluminosilicate materials was prepared using the microwave-assisted post-synthesis modification method developed. Interesting results were obtained from the comparative characterisation, catalysis and economic analysis, showing that these materials can be considered as another class of pure mesoporous catalysts with the potential interest for further exploitation.

Date of Award	18 Sept 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Arthur Garforth (Supervisor) & Xiaolei Fan (Supervisor)