Insights into the Reaction Mechanism of Ethanol Conversion into Hydrocarbons on H‐ZSM‐5

Abstract

Ethanol dehydration to ethene is mechanistically decoupled from the production of higher hydrocarbons due to complete surface coverage by adsorbed ethanol and diethyl ether (DEE). The production of C3+ hydrocarbons was found to be unaffected by water present in the reaction mixture. Three routes for the production of C3+ hydrocarbons are identified: the dimerization of ethene to butene and two routes involving two different types of surface species categorized as aliphatic and aromatic. Evidence for the different types of species involved in the production of higher hydrocarbons is obtained via isotopic labeling, continuous flow and transient experiments complemented by UV/Vis characterization of the catalyst and ab initio microkinetic modeling.

Unraveling the Homologation Reaction Sequence of the Zeolite‐Catalyzed Ethanol‐to‐Hydrocarbons Process

“…[1,3] Fori nstance,e thylene is also currently manufactured from bioethanol-derived sugary and starchy feedstocks. [3][4][5][6] In fact, the ethanol-to-hydrocarbons (ETH) process carried out by catalytic upgrading over solid-acid catalysts has recently captured al ot of attention in academia [4][5][6][7][8][9][10][11] and industry. [3,6,[12][13][14] TheE TH reaction was first commercialized by Elektrochemische Werke GmbH in Germany in 1913.…”

“…Only the first step of the ETH reaction (that is, dehydration) is relatively better understood in the literature. [8,[22][23][24][25] Unfortunately,t he rest of the reaction sequences (that is,homologation, cyclization, aromatization, and cracking) have yet to be unraveled. In particular,t he exact mechanistic routes to the origin of > C 2 even-numbered (that is,homologated products such as C 4 -butylene) and > C 2 odd-numbered (that is,n on-homologated products such as C 3 -propylene) carbon-containing hydrocarbon pool (HCP) species from C 2 -ethanol are still under scrutiny within the ETH process.T he importance of the mechanistic understanding of this industrial reaction should not be underestimated;assuch, information is crucial to maximizing yields and developing new and/or improved heterogeneous catalysts.…”

“…[19][20][21]28] Concurrently,C 2 -C 4 alkanes (5a-5c; Figure S9) are formed as ar esult of the "concomitantly operating" hydrogen-transfer reactions from the corresponding olefins. [28] In conclusion, our combined spectroscopic approach validates the hypothesis that the homologation-reactionmediated CÀCb ond coupling is indeed responsible for the formation of olefins and its higher homologues during the zeolite-catalyzed ETH process.T he "mechanistically decoupled" formation of ethylene from ethanol, [8] and its subsequent involvement in the formation of C 3+ -HCP species (aromatics/alkanes) as ar esult of homologation reaction, govern both autocatalytic and deactivation segments of the reaction. Although the homologation-reaction-dominated HCP mechanism is found to be influential, [18] characteristically it is quite different from the MTH process because of the deficiencyofits olefin cycle owing to its higher reactivity.The HCP species in the ETH process typically constitute multiple (m)ethylated aromatics (Table S3).…”

The influence of pore structure on reaction mechanism of propylene dimerization in zeolite: A theoretical viewpoint

“…A combined Our own N-layered Integrated molecular Orbital and Molecular mechanics (ONIOM) method was applied here. The 8 T ((SiO) 3 Si OH Al (SiO) 3 ) in the Brønsted center and all reactant molecules participating in the reaction are defined as high-level, using the ωB97XD/6-31G(d,p) method to perform structural optimization calculations. The ωB97XD is a recently developed long-range-corrected hybrid functional, which implicitly accounts for empirical dispersion and can describe long-range dispersion interactions better compared to the traditional DFT methods.…”

“…[1] Moreover, this reaction also involves the processes of proton migration, C C bond formation, and deprotonation, which are the key steps in olefin cyclization, aromatization, and other reactions, such as methanol to olefin. [2,3] Thus, in-depth study of alkene dimerization has been done by both experimental and theoretical methods. [4][5][6][7][8] Alkene dimerization generally proceeds with the help of catalysts.…”