Heterogeneous acid-catalysed isomerization of carvone to carvacrol (original) (raw)
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Selective production of carvacrol from carvone over supported Pd catalysts
Catalysis Communications, 2017
The selective conversion of biomass-derived carvone in H2 was studied over (Al2O3, C and CeO2) supported Pd (mean size 2.8-3.0 nm), taking bulk Pd as benchmark. 100% carvacrol yield was achieved over Pd/Al2O3, Pd/C and bulk Pd at an inlet H2/Carvone = 1/6, with appreciably higher rates for the supported catalysts. Carveol formation over Pd/CeO2 was attributed to-C=O activation at surface oxygen vacancies (confirmed by O2 titration) generated during TPR. Carvotanacetone and carvomenthone formation were observed at H2/Carvone > 1/6.
Role of acidity for the production of carvacrol from carvone over sulfated zircona
Indian Journal of Chemical Technology
A simple and eco-friendly process for the isomerization of carvone to carvacrol in the presence of SO42-/ZrO2 catalyst has been described. The reaction is conducted without solvent at moderate temperature with reaction times of 1 to 2 h. In most instances, nearly quantitative yield of carvacrol is obtained without any by-products. The total acidity, different acid concentration, zircona phases and crystallites size were co-related with the catalytic activity. Activation energy is found to be 11.317 kJ/mol using 8% SO42- ions modified zircona. The bulk and surface properties of the prepared catalysts are examined by X-ray powder diffraction, BET surface area and ammonia-TPD.
Synthesis of Biologically Active Carvacrol Compounds using Different Solvents and Supports
Synthetic Communications, 2007
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Liquid-Phase Oxidation of Carvacrol Using Zeolite-Encapsulated Metal Complexes
Industrial & Engineering Chemistry Research, 2006
We report here the use of zeolite-encapsulated metal (salpn) complexes as catalysts in the oxidation reaction of the natural compound carvacrol in acetonitrile with hydrogen peroxide as the oxidant. No previous studies on the oxidation of carvacrol in the presence of metal salpn complexes have been reported. By using a general flexible ligand method, Cr(III), Fe(III), Bi(III), Ni(II), and Zn(II) complexes of N,N′-bis(salicylidene)propane-1,3-diamine (H 2 salpn) encapsulated in NaY zeolite were prepared. All catalysts were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses to confirm the complex encapsulation. The activities of all prepared catalysts for the oxidation of carvacrol and hydrogen peroxide were tested. The performances of all catalysts were compared on the basis of the leaching test results and carvacrol conversions. Thymohydroquinone and benzoquinones were observed as byproducts at high conversions of carvacrol. No product was formed in the absence of a catalyst. Fe(salpn)-NaY catalyst exhibited the highest carvacrol conversion of 27.6% with a yield of 22.0%, followed by Cr(salpn)-NaY catalyst with 23.5% carvacrol conversion and a yield of 17.6%. Other catalysts have shown relatively lower performances in terms of carvacrol conversion and leaching. The Cr(salpn)-NaY catalyst was found to be a more efficient catalyst than others on the basis of leaching and activity tests. With the selected catalyst Cr (salpn)-NaY, the effects of temperature and carvacrol/hydrogen peroxide molar ratio on carvacrol oxidation reactions were investigated. Increasing the temperature from 40 to 60°C caused an increase in the thymoquinone yield from 6.2% to 16.0%. An increase in carvacrol/hydrogen peroxide molar ratio from 1 to 3 resulted in a decrease in the thymoquinone yield.
Journal of the Brazilian Chemical Society, 2013
Uma nova rota catalítica, de potencial interesse prático para a produção sustentável de acetinas a partir do glicerol, é descrita. Acetato de etila foi transesterificado com glicerol, numa razão glicerol:EtOAc 1:10, a 25 ou 90 o C, usando 0,1 equivalente de H 2 SO 4 ou TsOH como catalisadores homogêneos. H 2 SO 4 levou ao consumo total de glicerol, a 90 o C, em 2 h. No equilíbrio, atingido em 9 h, 100% de uma mistura diacetina:triacetina (55:45) foi formada. Usando-se Amberlyst TM 15 seca e Amberlyst TM 16 úmida numa razão glicerol:EtOAc 1:30 sob refluxo a 90 ºC, obteve-se o consumo total do glicerol em 2 e 10 h, respectivamente. A menor reatividade da resina Amberlyst-16 úmida foi explicada pela desativação dos sítios ácidos e pela diminuição da difusão do glicerol para o interior dos poros, causada pela água adsorvida. A cinética da transformação do glicerol e a distribuição de produtos no equilíbrio para a reação catalisada por H 2 SO 4 , Amberlyst TM 15 seca e Amberlyst TM 16 úmida foram medidas e racionalizadas. A new catalytic route with potential practical interest to sustainable production of bioadditives from glycerol is described. Ethyl acetate was transesterified with glycerol, in the ratio glycerol:EtOAc 1:10, at 25 or 90 o C using 0.1 equiv. of H 2 SO 4 or TsOH, as homogeneous catalysts. H 2 SO 4 led to the total glycerol consumption in 2 h. In the equilibrium, attained in 9 h, 100% yield of a diacetin:triacetin (55:45) mixture was formed. Using Amberlyst TM 15 dry and Amberlyst TM 16 wet in 1:30 glycerol:EtOAc ratio and reflux at 90 ºC the total glycerol consumption was achieved in 2 and 10h, respectively. The lower reactivity of Amberlyst-16 wet was explained in terms of deactivation of acid sites and decrease in glycerol diffusion to the inner resin pores, both factors caused by adsorbed water. The kinetics of glycerol transformation and product distribution in the equilibrium in relation to the H 2 SO 4 , Amberlyst-15 (dry) and Amberlyst-16 (wet) catalyzed reactions were measured.
Biotechnology and Bioengineering, 2008
The microbial biotransformation of (À)-transcarveol to the flavor and fragrance compound (R)-(À)carvone by Rhodococcus erythropolis DCL14 was carried out in a 3 L two phase partitioning bioreactor with an immiscible liquid second phase in an effort to improve upon the reactor performance achieved in a single aqueous phase system. The purpose of employing the liquid second phase is to minimize biotransformation rate inhibition due to the accumulation of the toxic substrate (cis-carveol) and product (carvone) in the aqueous phase. 1-Dodecene was chosen as the solvent for this application because it is biocompatible, non-biodegradable and has a superior affinity for the target product (carvone) relative to the other solvents tested. However, when 1-dodecene was used in the biotransformation, the extremely hydrophobic R. erythropolis DCL14 created an emulsion with the organic solvent with significant sequestering of the cells into the organic phase and negligible substrate conversion. To overcome these operational difficulties, silicone oil, which is considered a liquid polymer, was used with the aim of preventing emulsification and sequestration of cells in the non-aqueous phase. Although some emulsification of the water-silicone oil was again created by the cells, operability was improved and, in fed-batch mode, the system was able to convert approximately 2½ times more carveol than a benchmark single aqueous phase system before substrate/ product toxicity caused the biotransformation to stop. This study has demonstrated enhancement of a microbial biotransformation for the production of a high value nutraceutical compound via the use of a second partitioning phase, along with operational challenges arising from the use of a highly hydrophobic organism in such systems.
Reaction Kinetics, Mechanisms and Catalysis
This work describes the isomerization of S-carvone using a natural zeolite-clinoptilolite as the catalyst. The isomerization of S-carvone was carried out at the catalyst content in the reaction mixture from 5 to 15 wt%, in a temperature range of 190-210 °C and for the reaction time from 60 to 300 min. The main product of the isomerization of S-carvone was aromatic alcohol with many practical applicationscarvacrol. The use of the most favorable reaction conditions (the reaction time of 3 h, the temperature of 210 °C and the catalyst content 15 wt%) allowed to obtain this compound with high yield amounted to about 90 mol%. The S-carvone isomerization is an example of environmentally friendly process because it does not use any solvents, S-carvone can be separated from cheap cumin waste (renewable biomass) and a cheap zeolite of natural origin-clinoptilolite can be is used as the catalyst.
Amberlyst-15 in organic synthesis
Arkivoc, 2012
Commercially available Amberlyst-15 has played an important role in organic synthesis. This review summarizes the versatile synthetic applications of Amberlyst-15 in different chemical transformations. Reactions include esterification, transesterification, Michael addition, aza-Michael addition, Prins cyclization, Friedel-Crafts alkylation, acylation, metal free hydroarylation, hydroalkylation, halogenation, protection of carbonyls, amines, deprotection of acetals, acetates, Boc-protected amines, cleavage of epoxides, crossed-aldol condensation, synthesis of quinolines, pyrazolines, indolinones, acridines, calix[4]pyrroles, xanthenes, coumarins, benzopyrans theaspirane, furans, and substituted phosphonates. Applications of this catalyst allow mild and highly selective transformations and synthesis in a facile and environmentally friendly manner. The catalysts can be regenerated and recycled.