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

摘要

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 N2 gas was fed into the reactor and N2 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 during 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.