Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity

Abstract

Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.

A research into the thermodynamics of methanol to hydrocarbon (MTH): conflictions between simulated product distribution and experimental results

“…Like other researches, in our experiments methanol conversion mainly yield large portion of gas alkanes, gas olefins, as well as aromatics [4,5,11]. This is owing to the continuous flow of methanol feedstock and the non-stop transportation of previous formed products to the outside of the system (before the catalyst deactivates); in other words, the reaction happens in an opening system, which greatly reduces the chances of coke formation.…”

“…The selected 25 reactions have covered all the directions from methanol to the major MTH products (C 1 -C 9 ) with essential product intra-conversions, and are supposed to happen in a real MTH system proceeding in timeon-stream [11,12]. Particularly, we have further separated the isomers of xylene and tri-methylbenzene, for a more comprehensive study than the previous works, and a consideration that para-xylene might be the most favourable product in the methanol to aromatics process via H-ZSM-5 zeolite [4,8,9]. The intra-conversions between different xylenes and the reactions of toluene to benzene and xylenes are specially considered, highlighting the importance of BTX products (benzene, toluene and xylenes) in the total aromatics.…”

“…Methyl groups are added onto the hydrocarbon pool molecules in alkylation steps and light olefins are subsequently formed by the corresponding de-alkylation steps. The initial olefins can be converted into alkanes by occupying H 2 , whereas continuous loss of H 2 , followed by the cyclization steps forms more aromatics [3][4][5]. In a mature MTH system, series of the above reactions proceed in a parallel way and, therefore, bring in a complexity to the products and orders of their formation; however, thermodynamics always say coke (extremely dehydrogenated products, or solid carbons) is the dominating product in MTH and most other hydrocarbon transformations [6].…”

Local silico-aluminophosphate interfaces within phosphated H-ZSM-5 zeolites

“…[6][7][8][9][10][11][12] Even though there is still some debate on the effect of acid site strength on the MTO product distribution, the promoting effect of phosphorus on the hydrothermal stability of H-ZSM-5 is undisputed. 4,9,[13][14][15][16][17][18][19][20][21][22][23][24][25] Zeolite H-ZSM-5 catalysts that contain phosphorus are more stable under hydrothermal conditions i.e. they retain more framework aluminium species and strong acid sites than their non-phosphated counterparts.…”

Methanol-to-olefin conversion over H-MCM-22 catalyst

“…Furthermore, in view of the depletion of world oil reserves, it is urgent to develop new routes to produce light olefins using non-oil feedstocks [1]. During the past decades, methanol-to-olefin (MTO) conversion, as an alternative route for the production of light olefins, has attracted much attention, because methanol can be conveniently manufactured from any carbon-containing resources such as coal, natural gas and biomass [2][3][4][5]. In the process of MTO, the dual-cycle mechanism was widely accepted, the initial step is the formation of dimethyl ether (DME) through dehydration of methanol, and then reacts to produce light olefins.…”