Liquid-Phase Oxidation of Carvacrol Using Zeolite-Encapsulated Metal Complexes

Abstract

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.

From Zeolite to Host-Guest Nanocomposite Materials

“…Various high reactive zeolite encapsulated complex catalysts used for the oxidation of cyclohexene were illustrated in Table 7. Besides the type of catalyst, temperature and amount of catalyst effect on the catalytic activity and product selectivity [193][194][195]. Nanoscale microreactor containing (5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-4,11-diene)nickel(II) were entrapped in the supercage of zeolite Y and cyclohexene was catalytically oxidized in the presence of molecular oxygen and [Ni(Me 6 [14]aneN 4 )] 2+ -NaY.…”

The polymerization of carvacrol catalyzed by Mn-porphyrins: obtaining the desired product guided by the choice of solvent, oxidant, and catalyst

“…Carvacrol is a monoterpene extracted from the oregano ( Origanum vulgare L.) essential oil and it is one of the main precursors of benzoquinones, which can be obtained upon carvacrol's oxidation. 1–4 Thymoquinone (Scheme 1), a representative of this class and the main product from carvacrol oxidation, shows interesting properties such as antitumor, hepatoprotective and anticonvulsant properties, making it a sought-after substance. 1,5–7 Therefore, some studies on carvacrol's oxidation aiming to produce thymoquinone and other products (Scheme 1) were attempted.…”

“…1,5–7 Therefore, some studies on carvacrol's oxidation aiming to produce thymoquinone and other products (Scheme 1) were attempted. 4,8,9…”

Oxidation of Monoterpenes Catalysed by a Water‐Soluble MnIII PEG‐Porphyrin in a Biphasic Medium

“…[17] The oxidation of carvacrol and thymoli nt he presence of Keggin-type heteropolyanions and hydrogen peroxide, in acetonitrile at reflux, was also less selective, affording am ixture of benzoquinonesa sp roducts, in moderate conversion. [17] The oxidation of carvacrol and thymoli nt he presence of Keggin-type heteropolyanions and hydrogen peroxide, in acetonitrile at reflux, was also less selective, affording am ixture of benzoquinonesa sp roducts, in moderate conversion.…”

“…[M(salpn)-NaY;M= Cr,F e, Zn, Ni, Bi]a sc atalysts and hydrogen peroxide as oxidant, in acetonitrile. [17] The oxidation of carvacrol and thymoli nt he presence of Keggin-type heteropolyanions and hydrogen peroxide, in acetonitrile at reflux, was also less selective, affording am ixture of benzoquinonesa sp roducts, in moderate conversion. [18] Recently,t he oxidation of thymola nd carvacrol wass tudied by using potassium peroxymonosulfate( KHSO 5 )a so xidant in the presence of Fe III phthalocyanine tetrasulfonate( FePcTS) and am ixture of methanol:water (8:1) as solvent.…”