para-Selective t-butylation of phenol over mesoporous H-AlMCM-41

Structural characterization and catalytic properties of gallium-modified folded sheet mesoporous materials prepared using microwave-hydrothermal process

“…The selectivity of 2-TBP increases with increasing WHSV whereas the selectivity of 2,4-DTBP and 4-TBP decrease. The increase of the 2-TBP selectivity with increasing space velocity has been ascribed to the elimination of interparticle diffusional resistances at higher space velocities [29], but might as well indicate that this product is formed initially and later converted to the secondary products such as 2,4-DTBP and 4-TBP.…”

“…2,4-DTBP is largely used to produce substituted triaryl phosphates [23,24]. This reaction is a typical Friedel-Crafts alkylation reaction, and can be catalyzed by a variety of acid catalysts like homogeneous Lewis acids [25] and Brønsted acids [26], heterogeneous ion-exchange resins [27], zeolites [28] and mesoporous materials [29]. Use of homogeneous acid catalysts is generally avoided due to their unrecycled and corrosive nature, and ion-exchange resin cannot be used at high reaction temperature.…”

“…Their catalytic tests in the tertbutylation of phenol have also been extensively investigated [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Selvam and co-workers have reported that mesoporous MeMCM-48 and MeMCM-41 (Me = Ga, Fe, Al) solid catalysts possessed moderate acidity and were appropriate for the selective synthesis of 4-TBP [29,35,[39][40][41]. Hartmann and co-workers observed that Al-SBA-15 catalysts displayed higher conversion of phenol and selectivity to 4-TBP than FeAlMCM-41, Al-MCM-41 and Fe-MCM-41 catalysts [51].…”

Liquid phase alkylation of anisole and phenol catalyzed by niobium phosphate

“…Homogenous acid catalysts such as HF, H 2 SO 4 , AlCl 3 , or BF 3 are commonly used in Friedel-Crafts reaction, 6 but the toxic aqueous waste resulting from catalyst remains problematic. On the other hand, utilization of the ecofriendly heterogenous catalysts such as macroporous cation-exchanged resins (Amberlyst-15), 7 zeolites, 8,9 SAPO-11, 10 mesoporous materials 11 have advanced in recent years.…”

“…Alkylation of phenol has an additional complication because of the possibility of the alkyl attacking to the phenolic oxygen (O-alkylation) that leads to an ether formation beside desirable alkylations at the aromatic ring (C-alkylation). [11][12][13] Information about the use of niobium compounds for the alkylation of phenol with allylic alcohol is almost unexistent in the available literature.…”