Synthesis of Eugenyl Acetate in Solvent-Free Acetylation: Process Optimization and Kinetic Evaluation

Abstract

In this work, the synthesis of eugenyl acetate was evaluated in the presence of heterogeneous catalysts aiming developing an economical and environmentally friendly process. The catalysts used were molecular sieve 4Å and Amberlite XAD-16, and highest conversions were obtained in the investigated conditions by experimental design for both catalysts. In the kinetic study the effects of temperature, catalyst concentration and eugenol to acetic anhydride molar ratio in the conversion process were evaluated. The kinetics using molecular sieves 4Å were performed until 6 h of reaction, reaching conversions above 90% in 2 h and the activation energy was 2.40 kcal.mol -1 . With Amberlite XAD-16 up to 2 h reactions were conducted and in just 3 min high reaction conversions (97.8%) were achieved with lower activation energy (1.73 kcal mol -1 ) than the molecular sieve, demonstrating that both catalysts are effective for producing the eugenyl acetate. Heterogeneous catalysts allowed reaching high conversions using less amounts of substrates, in a solvent-free system, and also making possible regeneration and reuse.

Acetylation of Eugenol over 12-Molybdophosphoric Acid Anchored in Mesoporous Silicate Support Synthesized from Flint Kaolin

“…The ester derivative of eugenol was obtained by starting from the synthetic route using acetic anhydride (carboxylic acid) in reactions catalyzed by acidic solids as described in the literature [11,12]. Both eugenol and acetic anhydride are adsorbed at the active sites of the catalysts and the reaction proceeds through the formation of carbocations and the release of acetic acid (Scheme 4).…”

“…However, in high concentrations, it has an adverse effect of provoking inflammatory and allergic reactions, possibly due to its low instability, which favors the formation of phenoxyl radicals via its pro-oxidant activity [2,9]. Despite the fact that its structure is polyfunctional and readily accessible, eugenol is considered as a useful starting material for producing valuable derivatives through chemical synthesis [2,10,11,12,13,14,15] or biochemistry [1,4,9,16,17,18].…”

“…Thus, the use of heterogeneous catalysts is particularly advantageous because they are versatile, possess high operational efficiency under moderate reaction conditions, and additionally they provide a more ecological and economical route for esterification reactions [25,26,27,28,29,30,31]. In recent years, some acidic solids have been used as catalysts for the esterification or acetylation of eugenol, for example modified acid zirconia (UDCaT-5) [2] and ionic resins [10,11,12], which not only can be easily recovered and reused, but also favored the development of continuous production processes for a series of industrially important productions.…”

Synthesis of Solid Acid Catalyst from Fly Ash for Eugenol Esterification

“…High conversion at around 90% was achieved when temperature was increased up to 110 ºC for 240 minutes reaction. Using Amberlite XAD-16 reaction between eugenol and acetic anhydride to form eugenyl acetate achieved 85.0% and 98.6% conversion for reaction time 180 and 360 minutes, respectively and molar ratio 1:3 [17]. Other result [21] inform us that eugenyl acetate by enzymatic esterification of Novozym 435 as catalyst which come from the catalyst and the conversion of eugenyl acetate of 99.87%.…”

“…On-going efforts involve the use of solid acid catalyst: Amberlyst-15 [15], Alalginat [14], and zirconia UDCaT-5 [16], allowing for efficient catalyst separation and recovery and minimizing corrosion effects. Esterification of eugenol to eugenyl ester have been carried out using zirconia UDCaT-5 [16], molecular sieve 4Å and Amberlite XAD-16 [17], and anion exchange Amberlyst A-21 [18]. High conversion (90%) has been achieved for two hours reaction by using Amberlite XAD-16.…”