Identification of the coke deposited on 13X industrial zeolite molecular sieves during mercaptan removal process

Abstract

Industrial Z10-13X zeolite was deactivated by coking during the sequenced pressure and temperature swing mercaptan removal unit at the conditions of 40°C and 68 bar in adsorption mode and 300°C and 8 bar in regeneration mode. In this study, detailed coke features inside industrial molecular sieves, in terms of molecular structure and also some other brief properties, have been obtained for the first time by combining numerous techniques including gas chromatography coupled with mass spectrometry, thermogravimetric analysis, Brunauer-Emmett-Teller analysis, energy-dispersive X-ray spectroscopy, X-Ray diffraction pattern, and also CO 2 and N 2 adsorption/desorption isotherms of fresh and coked molecular sieves. The coke species were identified and classified into more than 40 different components following their alkylation and cyclization mechanisms. The coke includes polyaromatic hydrocarbons, and it was much alkylated especially with methyl and ethyl fragments. It is mainly compounded of derivatives of benzene located within the zeolite pore, which could grow into polyaromatic compounds constituted up to four aromatic rings with different guest polar elements.