Extractor-type catalytic membrane reactor with nanocomposite MFI-alumina membrane tube as separation unit: Prospect for ultra-pure para-Xylene production from m-Xylene isomerization over Pt-HZSM-5 catalyst
Résumé
This paper is a follow-up on our recent study on the applications of extractor-type zeolite catalytic membrane reactor (herewith referred to as e-ZCMR) for m-Xylene isomerization. In this paper, results of a preliminary investigation on the possibility of producing ultra-pure p-Xylene (PX) (purity > 99%) via m-Xylene (MX) isomerization over Pt-HZSM-5 catalyst in an e-ZCMR with a "defect-free" nanocomposite MFI-alumina membrane tube as the separation unit is presented. Unlike "film-like" architectures, in nanocomposite architectures zeolite crystals are embedded within the pores of the supports. During m-Xylene isomerization conducted at a temperature range 473-573 K, liquid meta-Xylene (99% purity) saturated in N-2 gas was fed into the reactor and N-2 gas was swept over the outer surface of the membrane on the shell side of the reactor. Analysis of results was based on permeate-only mode (products in permeate stream only) and combined mode (products in both permeate and retentate) operations. At 473 K, e-ZCMR gave a maximum p-Xylene yield of 2.7% at permeate-only mode and 19.0% at combined mode. Throughout the temperatures investigated, the purity of PX approached 100% in the permeate and the membrane displayed 100% PX selectivity. These results indicate that there is a possibility of cutting down operational costs through a reduction in energy consumption (luring ultra-pure PX production and that this becomes feasible with the application of e-ZCMR having nanocomposite MFI-alumina membrane as separation unit. However, high flux defect-free nanocomposite MFI-alumina membranes are necessary to make this technology attractive and competitive with those currently in use. (C) 2010 Elsevier B.V. All rights reserved.