(180c) Radio Frequency Driven Catalytic Reactors for Portable Green Chemistry

Heterogeneous catalytic reactors account for roughly 80% of all chemical manufacturing processes,¹ and are often driven by external heating of the catalyst via fuel-fired furnaces or utility steam. Traditional methods relying on combustion of fuel often lead to greenhouse emissions, limit distributed chemical production due to economy of scale, require additional infrastructure and large reactor size to accommodate combustion zones and insulation around the reactor. They also have thermal gradients in reactors which often compromises performance, utilization, lifetime, and selectivity of the catalyst.

The volumetric electric heating methods and modular reactors for power-to-chemicals route can pave a path towards distributed manufacturing and reduced greenhouse gas emissions when electricity is harnessed from renewable energy sources. Uniform volumetric heating of catalyst can also improve catalyst utilization, avoid homogeneous side reactions, and improve reactor portability.² Since the first published report of microwave organic synthesis, ^3-4 microwave heating has been studied for various endothermic catalytic reactions.⁵ However, high power microwaves (> 2.45 GHz frequency) are limited due to temperature hotspots, runaway reactions, penetration depth, reflection losses, and stringent safety exposure limits.

This study employs a multidisciplinary approach to make portable reactors by using novel materials like carbon nanotubes (CNTs) and silicon carbide (SiC) fibers as additives in catalyst. We utilize interaction of these materials with radio frequency fields (1 MHz-300 MHz) to selectively heat catalytic reactors and drive a reaction. A proof-of-concept is demonstrated for methanol steam reforming reaction using platinum as a catalyst. The RF heating response of CNT/platinum /alumina and SiC fiber/platinum were investigated for varying power using different kinds of noncontact RF applicators. The conversion of methanol for different reaction temperatures was compared to conventional ovens. This power to chemical method has application in modular reactors for on-site and on-demand production of chemicals using electric power.

(1) Fechete, I.; Wang, Y.; Védrine, J. C. The past, present and future of heterogeneous catalysis. Catalysis Today 2012, 189 (1), 2-27, DOI: https://doi.org/10.1016/j.cattod.2012.04.003.

(2) Wismann, S. T.; Engbæk, J. S.; Vendelbo, S. B.; Bendixen, F. B.; Eriksen, W. L.; Aasberg-Petersen, K.; Frandsen, C.; Chorkendorff, I.; Mortensen, P. M. Electrified methane reforming: A compact approach to greener industrial hydrogen production. Science 2019, 364 (6442), 756-759, DOI: 10.1126/science.aaw8775.

(3) Gedye, R.; Smith, F.; Westaway, K.; Ali, H.; Baldisera, L.; Laberge, L.; Rousell, J. The use of microwave ovens for rapid organic synthesis. Tetrahedron letters 1986, 27 (3), 279-282.

(4) Tse, M. Y.; Depew, M. C.; Wan, J. K. S. Applications of high power micro wave catalysis in chemistry. Research on Chemical Intermediates 1990, 13 (3), 221-236, DOI: 10.1163/156856790x00102.

(5) Ramirez, A.; Hueso, J. L.; Abian, M.; Alzueta, M. U.; Mallada, R.; Santamaria, J. Escaping undesired gas-phase chemistry: Microwave-driven selectivity enhancement in heterogeneous catalytic reactors. Science Advances 2019, 5 (3), eaau9000, DOI: 10.1126/sciadv.aau9000.