Improved Catalyst Boosts Petrochemical Production Yields

Advanced Catalyst Could Translate to Petrochemical Production Gains Aromatics are the building blocks of all polymers or plastics, from PET bottles to wrinkle-resistant breathable polyester clothing. These petrochemicals constitute a specialized, value-added sector of the energy industry. The process of refining crude petroleum into useful aromatic streams for derivative use typically involves the use of a catalyst to facilitate chemical reactions. Among various catalyst types are zeolites—porous aluminosilicates—such as ZSM-5, a unique synthetic zeolite used efficiently in elevating chemicals in alkylation and isomerization reactions. Petrochemical producers continually attempt to minimize overall expenses to counteract fluctuations in commodity markets and present a competitive end product to the average consumer. Jeffrey Rimer, Abraham E. Dukler Professor of Chemical Engineering at the Cullen College of Engineering at the University of Houston, and Javier Garcia-Martinez, professor of inorganic chemistry at the University of Alicante, have developed a seeding method that simplifies the synthesis process and results in the spontaneous assembly of zeolites. The study was published in Advanced Materials. The process results in a unique crystal structure that facilitates chemical reactions with higher aluminum concentration in the zeolite and less carbon accumulation. "This new technique has the advantage of producing thicker and better-shaped layers; this is important for producing extremely stable materials, a significant characteristic in most industrially relevant applications," said Martinez. According to Rimer, "These hierarchical catalysts demonstrate unprecedented advances in catalyst performance, with deactivation rates four times lower, a five-fold increase in activity, and approximately two-fold increase in selectivity." In the industry, petrochemical producers typically must undergo maintenance to replace or completely change the catalyst every two years. In the United States, typically many refineries enter a maintenance period of two weeks to two months for this purpose between the end of the first quarter and the beginning of the second quarter. During this period, production and profit losses occur, and although these improved hierarchical zeolite catalysts will not completely eliminate maintenance periods, their smaller but stable 30-60 nanometer dimensions provide aluminum active sites for catalysis comparable to commercial ZSM-5. However, their small size simultaneously increases selectivity and reduces carbon accumulation. This signals longer periods between costly turnarounds and increased yields. The results of this study extend to a better understanding of zeolite nucleation (the first observation of a crystal) and point to a new process for creating pillared zeolites without costly organic structure-directing agents (OSDA). Zeolites with hierarchical (pillared) structures were previously prepared only with OSDAs that served as templates to create these unique structures. "Until now, it was believed that OSDAs were critical for the synthesis of pillared zeolites and served as templates to facilitate the formation of thin interlayer nanosheets," said Rimer. "However, as we observed in this seeding process, these 30-60 nanometer nanosheets emerged from amorphous material and formed pillars without any template." "Previous attempts to produce these catalysts required expensive organic compounds and typically achieved low yields, which greatly limited their commercial applications," said Martinez. The seeding has proven effective in synthesizing pillared zeolites that improve catalytic performance in Friedel-Craft alkylation and methanol-to-hydrocarbon reactions. This synthesis approach bypasses the typical energy-intensive process of using OSDAs. Organic compounds previously thought necessary for the creation of commercially usable zeolites are now no longer required. Next steps for this project include scaling up the process to demonstrate whether the performance of this improved zeolite catalyst can be replicated at industrial scale. This research also serves as a springboard to further investigate the effects of seeding in producing other zeolites with unique structures and exceptional performance in commercial applications.   Source More information: Rishabh Jain et al, Spontaneous Pillaring of Pentasil Zeolites, Advanced Materials (2021). DOI: 10.1002/ adma.202100897 / Journal information: Advanced Materials / Provided by University of Houston