Study and Comparison of Performance of Zeolite and Zeotype Molecular Sieves in Conversion of Methanol to Olefin

Conversion of methanol to olefins (MTO) process is one of the most interesting processes for converting natural gas to chemical products. Molecular sieves are the conventional catalysts for this process. In this paper, the selectivity of three groups of molecular sieves, including small, medium and large pore opening, relative to light olefins has been studied for the purpose of improvement of the light olefin products in MTO reaction. Small pore opening molecular sieves in comparison with large and medium pore opening molecular sieves showed higher selectivity to light olefin, although formation of branched isomers and aromatics in its pores caused fast deactivation of the catalyst. Evaluation of these groups of molecular sieves for conversion of methanol to light olefins showed that small pore size molecular sieves, particularly SAPO-34, exhibited the best performance based on the selectivity to C2–C4 olefins and minimum production of paraffinic and aromatic byproducts. Because of its appropriate size and acidity, SAPO-34 molecular sieve reveals a very high selectivity to light olefins. However formation of aromatic compounds inside the small pores of this catalyst may lead to its faster deactivation.