The mechanism of phenol methylation on acid and basic zeolite catalysts

Structure and Reaction Mechanism of Alkylation of Phenol with Methanol over H-FAU Zeolite: An ONIOM Study

“…Although anisole is a kinetically favorable product of phenol methylation, under some circumstances, at higher temperatures and with a longer reaction time, it can be transformed to cresol directly. ,,, Previous experimental studies have shown that o -cresol is the most populated product of phenol methylation. ,, This suggests that o -cresol is a more thermodynamically stable product of the reaction, consistent with our finding that the formation energy of o -cresol (−15.3 kcal/mol) is more exothermic than that of anisole (−1.6 kcal/mol).…”

“…Faujasite zeolite, in particular, is considered to be one of the major catalysts used in petrochemical industries. Its protonic form has been found to be a significant active constituent for the catalytic cracking of hydrocarbons. − In addition, its supercage with a diameter of approximately 13 Å enables it to operate in the same manner as a nanoreactor for the reactions of bulky molecules, including the alkylation of phenol and its family members. − The latter process is currently being pursued by environmentally concerned chemical industries. The obtained products are used as important raw intermediates for the synthesis of drugs, resins, pharmaceuticals, and dyestuffs.…”

“…If it takes place through the concerted route, it will process via one step by the coadsorption of phenol with methanol and conversion to the product directly. However, many references in literature have reported the alkoxide intermediate formation during alkylating processes. − ,− Furthermore, theoretical calculations have confirmed that alkoxide intermediates are stable on the zeolitic framework and are found to be reactive intermediates. −

1 178T nanocluster of faujasite zeolite subdivided into two layers of calculation methods according to the two-layer ONIOM (ONIOM2) scheme: the 14T cluster (balls) was computed with the B3LYP/6-31G(d,p) level of theory, and the remainder (lines) was computed with the universal force field (UFF).

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“…9 Nevertheless, the real mechanism of the alkylation of phenol with methanol over solid acid catalysts has never been elucidated, even though it is still comprehensively discussed in various literatures. 5,7,[9][10][11][12][13][15][16][17][18][19][20][21][22] Until the present time, it has been understood that the reaction occurs through the concerted route or via the step-by-step route. If it takes place through the concerted route, it will process via one step by the coadsorption of phenol with methanol and conversion to the product directly.…”

Impact of in situ MAS NMR techniques to the understanding of the mechanisms of zeolite catalyzed reactions

“…Among other topics of considerable interest are the reactions of aromatic compounds, 40,48,53,63,74,103,129,[166][167][168][169][170] oximes, 171 carbonyl compounds, 40,56,80,105,117,124,172-177 halogen 58,73,100,175,178 and nitrogen [54][55][56]68,116,[123][124][125]150,171,174,[179][180][181] containing compounds (Table 1). The central questions here were related to the nature of adsorption complexes, surface species and intermediates.…”