Applicability of a recycle reactor scheme to the conversion of methane to aromatics
Abstract
We have proved in this study that a two-bed recycle reactor scheme can overcome the yield barrier for oxidative coupling of methane (OCM) by converting the C2 products to aromatics. Such a design places new demands on the catalysts, however, since the OCM catalyst must operate in the presence of aromatics, and the aromatization catalyst must tolerate the unreacted methane. This work focuses on the design of such catalyst materials and improvement of the system performance through adjusting the operating parameters. The catalysts were prepared by incipient wetness impregnation. Experimental studies were conducted in a quartz fixed bed flow reactor at atmospheric pressure, and the analysis was carried out by an online gas chromatograph (Agilent 6890). The set of operating conditions that demonstrated product yield improvement in the recycle configuration are 800°C, 0.002gmin/ml and a 10wt%LiCl/15wt%MnO2/SiO2 catalyst loading for the OCM and 550°C, 0.04gmin/ml and a loading of 1wt%Pt-5wt%Ga/ZSM-5 for the aromatization reactions. We showed that our system produces 40% aromatics, mainly benzene and a small amount of toluene (B/T product ratio is 20/1), at a recycle ratio of 11 under relatively high methane/oxygen feed flow conditions. Although there is still room for improvement of several issues, one being implementing a means of catalyst regeneration, our system brings both capital and operating cost advantages since it is a simple two-reactor recycle configuration with no intermediate separations. The aromatics yield we obtained from our scheme is double the value that can be obtained from the operation of the best available OCM and aromatization reactors in series. Finally, we have also developed in this research a strategy for experimental analysis of the patterned reactors viability that can be applied to other types of reactions networks.
Degree
Ph.D.
Advisors
Delgass, Purdue University.
Subject Area
Chemical engineering
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