Recent Progress in Methanol‐to‐Olefins (MTO) Catalysts

Abstract

Among the 8-MR molecular sieves, silicoaluminophosphate SAPO-34 with 3D channels and moderate acid strength represents the most interesting one, the light olefins selectivity of which could reach up to 90% or even higher. [7] The excellent MTO performance of SAPO-34 was first reported by Dalian Institute of Chemical Physics (DICP) in 1990. [8] The researchers also demonstrated the good regeneration stability and high-temperature steam stability of Inspired by these pioneering discoveries, extensive research efforts have been devoted to SAPO-34 focusing on the elucidation of its crystallization mechanism, synthesis optimization, and the relevant catalytic studies, which greatly promote the technological development of the MTO process. Although SAPO-34 exhibits high catalytic activity and high selectivity toward light olefins, it suffers a rapid deactivation due to the coke deposition. Moreover, the MTO reaction on SAPO-34 catalyst is highly exothermal. These features determine that the industrial MTO process based on SAPO-34 catalyst has to adopt fluidized bed reactor, which allows efficient heat transfer and enables the continuous regeneration of the catalyst. In 2010, the world's first commercial MTO unit was successfully commissioned in Baotou, China by DICP (named DMTO technology). [5,10] The production capacity of ethylene and propylene is 0.6 Mt a −1 . To supply commercial catalysts for the DMTO unit, a 2000 t a −1 catalyst manufacturing plant was started up in Dalian in 2008. Afterward, DICP developed the DMTO-II technology, in which the byproducts of C 4 + are separated and introduced into a fluidized-bed cracking reactor to improve the yields of ethylene and propylene. Both the cracking unit and the MTO unit share one regenerator and use the same catalyst. By the end of 2018, thirteen DMTO units have been put into operation with a total production capacity of 7.16 Mt a −1 . Moreover, DICP launched the new generation of DMTO catalyst and completed the pilot test of the DMTO-III technology in 2018, both of which aim to further improve the olefins yield of DMTO units. The catalyst and technology development of the DMTO process are summarized in Figure 1.Based on SAPO-34 catalyst, UOP and Norsk Hydro also developed an MTO process with a low-pressure fast fluidizedbed reactor. [11] In 2013, a commercialized MTO plant (0.3 Mt a −1 olefins) was commissioned in Nanjing, China, which combines the UOP/Hydro MTO process and the total/UOP olefin cracking process to enhance the yield of ethylene and propylene. In addition, Shanghai Research Institute of Petrochemical Technology Methanol conversion to olefins, as an important reaction in C1 chemistry, provides an alternative platform for producing basic chemicals from nonpetroleum resources such as natural gas and coal. Methanol-to-olefin (MTO) catalysis is one of the critical constraints for the process development, determining the reactor design, and the profitability of the process. After the construction and commissioning of the world's first MTO plant by Dalian I...

Directed transforming of coke to active intermediates in methanol-to-olefins catalyst to boost light olefins selectivity

“…By use of mimics of the HCPs as organic structure-directing agents (OSDAs) to synthesize CHA and RTH-related zeolites, it is possible to maximize the host–guest interaction between framework and polymethyl aromatic intermediates to promote the propylene/ethylene ratio 8 , 11 . However, precise design and synthesis of targeted zeolites with specific OSDAs are extremely challenging 23 , especially the HCPs slightly different in structures may significantly change the product selectivity 8 . Co-feeding of methanol with organic intermediates, e.g., alkenes 24 , aromatics 25 or formaldehyde 26 , has also been applied to adjust ethylene/propylene ratio via altering the HCPs dominating either olefinic or aromatic cycle 2 , 6 according to dual-cycle mechanism.…”

Modulation of SAPO-34 Property with Activated Seeds and Its Enhanced Lifetime in Methanol to Olefins Reaction

“…For the SP34-RS and SP34-AS X samples, both high-and low-temperature peaks were less intense than those of SP34, which suggested the decreasing trend of acid site density in these samples. It is well known that SAPO-34 catalysts with mild acid strength and relatively low acid site density are more appropriate for the MTO reaction [5] . The catalytic activities of the six samples in the MTO reaction were evaluated in a fixed bed reactor at 400 ℃ with a methanol WHSV of 2.0 h -1 , and the results were plotted in Fig.…”

“…Zeolites with uniform micropores, tunable acidities, and high thermal/hydrothermal stability are important heterogeneous acidic catalysts in the petrochemical and fine chemical industries [1][2][3] . In recent years, as a successful alternative route of producing light olefins via a nonpetrochemical approach from the abundant resources of coal, natural gas, and even biomass, the zeolitecatalyzed methanol-to-olefins (MTO) reaction has gained considerable attention from academic and industrial communities [4][5][6][7][8] . After extensive experimentation using various molecular sieves, it was demonstrated that smallpore 8-membered ring (8-MR) molecular sieves served as excellent catalysts in the MTO reaction (100% methanol conversion) [9] .…”

The Different Effects of Organic Amines on Synthetic Metal Phosphites/Phosphates

“…Inorganic open-framework metal phosphates have been widely studied due to their channel structure and potential applications in industrial catalysis, gas separations, and so forth [1][2][3][4]. For example, SAPO-34 catalysts provide an alternative platform for methanol conversion to olefins (MTO), which produces basic chemicals from nonparallel resources, such as natural gas and coal [5]. Since the aluminophosphate zeolite was first reported in 1982 [6], various metal phosphate materials have been found in related literature [7][8][9].…”