Aromatics are the main building blocks of polymers, or plastics, that are used to make everything from PET bottles to carry water to breathable, wrinkle-proof polyester clothing. These petrochemicals make up a particular, value-added sector of the energy business.
The technique for refining crude oil into beneficial aromatic streams for derivative use generally involves using a catalyst to enable chemical reactions. Of the different types of catalysts, most of them are zeolites—porous aluminosilicates—such as ZSM-5, an exclusive synthetic zeolite copiously used in the advancement of chemicals in isomerization and alkylation.
Makers of petrochemicals are continually seeking to reduce overhead costs to handle the volatility in commodity markets and deliver a competitive final product to the average person.
Jeffrey Rimer, Abraham E. Dukler Professor at the University of Houston Cullen College of Engineering and Javier Garcia-Martinez, professor of inorganic chemistry at the University of Alicante, have discovered a seeding process that streamlines the synthesis technique and leads to instantaneous pillaring of zeolites.
The research has been published in Advanced Materials. The technique leads to more aluminum concentrate in the zeolite and a novel crystal structure to enable chemical reactions with minimized carbon accumulation.
This novel technique has the advantage of producing thicker well-formed sheets, which is important to produce highly stable material—an important feature in most industrially relevant applications.
Javier Garcia-Martinez, Professor of Inorganic Chemistry, University of Alicante
These hierarchical catalysts show unprecedented improvement in catalyst performance with 4-fold lower rates of deactivation, five-fold increases in activity and nearly two-fold increases in selectivity.
Jeffrey Rimer, Abraham E. Dukler Professor, Cullen College of Engineering, University of Houston
In industry, makers of petrochemicals often have to take turnarounds once in two years or so to regenerate a catalyst or substitute it altogether.
In the United States, late first quarter to early second quarter typically witnesses a number of refiners take a two-week to two-month maintenance period to facilitate this. During that period, there is no production and profit, and although these enhanced hierarchical zeolite catalysts will not prevent turnarounds completely, their smaller but consistent 30–60 nm size offers aluminum—active sites for catalysis—similar to commercial ZSM-5.
But their small size increases selectivity and decreases carbon accumulation at the same time. This hints at lengthier timeframes between costly turnarounds and improved yield.
“Until now, OSDAs were believed to be critical to synthesis of pillared zeolites, acting as templates to facilitate the formation of thin interconnecting nanosheets,” Rimer noted. “But 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 costly organic agents and low yields were typically obtained, which greatly limited their commercial application,” Martinez added.
Seeding turned out to be crucial in synthesizing pillared zeolites with enhanced catalytic performance in methanol-to-hydrocarbon reactions and Friedel-Craft alkylation. This synthesis method avoids the characteristic energy-intensive process of using OSDAs. Organics formerly considered vital for developing zeolites that can be used commercially are no longer required.
Subsequent steps for this study include the optimization of the process to show whether this enhanced zeolite catalyst can repeat its performance on industry scale. This study also serves as a facilitator for more explorations on the consequences of seeding to create other zeolites with exclusive structures and excellent performance in commercial applications.
Jain, R., et al. (2021) Spontaneous Pillaring of Pentasil Zeolites. Advanced Materials. doi.org/10.1002/adma.202100897.