Microfibrous Entrapped Catalyst Structure for Highly Exothermic Reaction: Fischer-Tropsch Synthesis

An Abstract Submission to 2017 AICHE Meeting

Session: Alternative Fuels

Topical Area: Catalysis and Reaction Engineering Division

Microfibrous Entrapped Catalyst Structure for Highly Exothermic Reaction: Fischer-Tropsch Synthesis

Xinquan Cheng and Bruce J. Tatarchuk*

Center for Microfibrous Materials Manufacturing, Department of Chemical Engineering, 212 Ross Hall, Auburn University, AL 36849

*Corresponding author. Tel.: +1 334 844 2023; fax: +1 334 844 2065; E-mail address: Tatarbj@auburn.edu

 

Abstract

Fischer-Tropsch synthesis (FTS) is a well-known technique for converting gas to liquid fuels. However, FTS is a highly exothermic reaction, which producing extremely amount of heat during the reaction process. More important, the product distribution of FTS is strongly dependent on the reaction temperature. High temperatures favor the formation of undesirable light products like methane. Therefore, a reactor system with an excellent heat transfer property is necessary for highly exothermic reaction like FTS. Our group developed a novel catalyst structure called Microfibrous Entrapped Catalyst (MFEC) structure. MFEC is a catalyst network supported by micron-sized metal fibers with high thermal conductivity. Previous efforts on this unique catalyst structure have shown significant enhancement in intra-bed heat transfer and maintains a stable reaction temperature.

In this investigation, both iron-based and cobalt-based FTS catalysts have been tested for FTS reactions in a large tubular reactor (34.0 mm I.D.) packed with Cu MFEC. Typically, the MFEC reactor can be prepared in two steps: 1) the prepared catalyst particles were entrapped into a sintered copper microfiber media to form a Cu MFEC structure; 2) circular disks with a diameter of 36.0 mm were punched out from the Cu MFEC structure to pack into the tubular reactor. The disk size (36.0 mm) were designed 6 % larger than the inside diameter of the tubular reactor (34.0 mm) in order to increase the contact points between the copper fiber media and the reactor wall. By doing this, the inside wall heat transfer coefficient increased greatly when compared with the traditional packed bed. A four-point thermocouple was sticked in from the side when the reactor was loaded half way, and then loading the other half. In that way, the radial temperature distribution profiles can be measured precisely. Take iron-based catalyst as an example, the reaction demonstrated a radial temperature gradient around 5 ºC. While with the same test conditions, the comparative packed bed reached a radial temperature gradient around 139 ºC. It was also found that the Cu MFEC based FTS reaction required negligible amount of time to reach its steady state compared with the traditional packed bed. Considering these attributes and advantages, Cu MFEC structure is a promising reactor system for highly exothermic reactions such as the FTS reaction.