Study of Gas Phase m-Cresol Alkylation with Methanol on Solid Acid Catalysts

Abstract

The gas-phase alkylation of m-cresol with methanol was studied at 523 K on Al-MCM-41 and zeolites ZnY, HBEA, HZSM5 and HMCM22. The acidity was determined by ammonia TPD and FTIR of adsorbed pyridine. On acid sites of moderate strength (Al-MCM-41), initially the O-alkylation rate was higher than the C-alkylation rate. In contrast, formation of dimethylphenols by C-alkylation was highly favored on ZnY and HMCM22 which have both strong acidity although different nature; Lewis (ZnY) and Brønsted and Lewis (HMCM22). High selectivity of 2,5-DMP was observed on HZSM5, probably due to diffusional constraint. All catalysts, except Al-MCM-41, showed deactivation by coke formation.

Thermodynamic Insights into Valorization of Biomass-Derived Oxygenates and Reconciliation with Experimental Study

“…This further confirmed that the isomerization of m- cresol becomes a major reaction beyond 270 °C which lowered its availability in the feed and hence, conversion decreased . Moreover, the decrease in conversion after this temperature can be attributed to the formation of coke due to side/parallel reactions and pore blocking on the catalyst …”

“…37 Moreover, the decrease in conversion after this temperature can be attributed to the formation of coke due to side/parallel reactions and pore blocking on the catalyst. 46 The selectivity to the alkylated products on iso-propylation of m-cresol as a function of temperature is included in Figure 8 (Tables S12−S15 in Supporting Information). The Oalkylation results in the formation of ether product, IPMCE, whereas, the C-alkylation leads to the formation of isopropylated m-cresols, (2-isopropyl-5-methylphenol (thymol), 4-isopropyl-3-methyphenol (4I-3MP), and 3-isopropyl-5-methylphenol (3I-5MP)) and di-iso-propylated products, (2,4-di-isopropyl-5-methylphenol (2,4DI-5MP) and 2,6-di-iso-propyl-3methylphenol (2,6DI-3MP)).…”

“…Earlier literature reports suggested that parallel reactions which involve alkylating agents cause coke formation. 46,50 Iso-propanol undergoes dehydration followed by condensation to form DIIPE on the solid acid catalysts (either Bronsted or Lewis sites) which was observed to be a thermodynamically highly feasible reaction under the operating reaction conditions. This results in the formation of coke precursors such as light hydrocarbons and aromatics due to self-oligomerization.…”

Role of Cu–Mg–Al Mixed Oxide Catalysts in Lignin Depolymerization in Supercritical Ethanol

“…We relate this to different rates of the alkylation reactions of the aromatic products, which also contribute to suppressing repolymerization reactions. , It is reasonable to postulate that the lower alkylation activity is associated with the absence of Al. It is well-known that alkylation reactions (e.g., phenol alkylation with alcohols) are catalyzed by inorganic Lewis and/or Brønsted acids such as H 2 SO 4 , AlCl 3 , and BF 3 , as well as solid acids such as zeolites …”

“…It is well known that alkylation reactions (e.g., phenol alkylation with alcohols) are catalyzed by inorganic Lewis and/or Brønsted acids such as H2SO4, AlCl3, BF3, 57 as well as solid acids such as zeolites. 58 In order to establish whether differences in the alkylation activity can explain the better performance of the hydrotalcites derived catalysts, we carried out model reactions using phenol as reactant in supercritical ethanol (340 °C, 4 h, 1 g phenol, 40 ml ethanol). The reaction mixtures were analyzed by GC-MS and quantified by GC-FID.…”