PERFORMANCE OF ZSM-5 CATALYST IN THE DIMETHYL ETHER TO OLEFINS PROCESS

Abstract

ABSTRACT The conversion of dimethyl ether (DME) to hydrocarbons is the latter step in the conversion of syngas to hydrocarbons via DME. The shape-selective ZSM-5 zeolite catalyst plays an instrumental part in this reaction in limiting the higher end of the product spectrum. This process, being of an exothermic nature, results in a temperature rise across the catalyst bed causing some hydrocarbons to be deposited on the catalyst as coke. The presence of water as a byproduct in the catalyst environment also enhances the catalyst deactivation. Deactivation of the ZSM-5 catalyst is studied in detail in terms of catalyst performance and life over a period of time. The conversion of DME and the hydrocarbon product distribution are studied as a function of time-on-stream The SiO2/Al2O3molar ratio of the ZSM-5 catalyst is regarded to be important in determining the degree of coke formation as well as the product distribution of the final hydrocarbon product. Catalysts used in aging experiments were studied as to determine the quantity and structure of the deposited coke. Extracted coke from the catalyst was analyzed using gas chromatography/mass spectrometry methods. The coked catalyst was also analyzed using infra-red as welt as x-ray diffraction techniques.