Evolution of confined species and their effects on catalyst deactivation and olefin selectivity in SAPO-34 catalyzed MTO process

Abstract

A “three sections, three periods” mechanism is proposed to discuss the formation and transformation of confined species and its effects on catalyst deactivation and product selectivity.

Methanol‐to‐Olefins in a Membrane Reactor with in situ Steam Removal – The Decisive Role of Coking

“…Haw and Marcus proposed in 2005 a “cigar burn” mechanism to describe the development of the product selectivity of the MTO reaction in a SAPO‐34 catalyst bed, which is comparable to our approach of a membrane reactor with a packed catalyst bed . The reaction primarily takes place at the point where the methanol hits the catalyst first due to the high conversion rate of SAPO‐34 . Consequently, the catalytically working zone (with methylated benzenes and naphthalenes) moves through the catalyst bed and leaves the deactivated catalyst (CHA cages completely occupied by pyrenes) behind.…”

“…The DTA profile of Section 2 of the SAPO‐34 catalyst with the LTA membrane indicates a large presence of these types of hydrocarbons. Higher condensated and bulkier polyaromatics, combust at temperatures higher than 500 °C, peaking above 550 °C . All types of catalyst (without and with LTA membrane Sections 1 and 2) have local maxima in the DTA curves at 600 °C (see dotted line, Figure ) suggesting the existence of polyaromatics an all cases.…”

“…The different methanol reactions at the acidic sites will not only form light olefins but also a variety of high molecular weight hydrocarbon species in the pore system. Their formation and influence inside the pores of different acidic catalysts and their participation in the MTO reaction is a widely researched topic …”

“…As mentioned above, coking of the catalyst is a severe problem of the MTO process since it leads to pore blocking of the catalyst and severe diffusion problems . Literature reports that the presence of steam in the feed should reduce catalyst coking, thus extending its lifetime …”

“…As mentioned above, coking of the catalyst is a severe problem of the MTO process since it leads to pore blocking of the catalyst and severe diffusion problems. [22][23][24][25][26][27] Literature reports that the presence of steam in the feed should reduce catalyst coking, thus extending its lifetime. [28][29][30][31] The industrial application of the MTO reaction, a fluidized bed reactor, suffers heavily from attrition and requires the permanent exchange of the catalyst.…”