Liquid Phase Oxidation of p-Cresol over Cobalt Saponite

Abstract

Liquid phase oxidation of p-cresol was carried out over a Co-saponite catalyst in a temperature and pressure range of 333-393 K and 20-827 kPa, respectively in n-propanol. Co-saponites with varying cobalt content (5-30%) were prepared and screened among which 13% Co-saponite gave the highest conversion of 92% of p-cresol with 92% selectivity to p-hydroxybenzaldehyde without formation of any non-oxidation products.

Highly selective liquid-phase aerobic oxidation of vanillyl alcohol to vanillin on cobalt oxide (Co3O4) nanoparticles

“…Although homogeneously catalyzed liquid-phase air oxidations are commonly practiced in industry using organometallic complexes as catalysts, the major drawbacks of such oxidations are: (i) poor selectivity to the desired product, a variety of oxygenated products are formed because of the formation of free radical intermediates; (ii) fast deactivation of homogeneous catalysts due to formation of m-oxo dimers; (iii) contamination of the product due to trace metal impurities during catalyst separation protocol. [6][7][8][9] These problems can be overcome by designing a suitable heterogeneous catalyst because they offer many advantages over their homogenous counterparts such as easy handling, separation and reusability. Therefore, development of functionalized heterogeneous catalysts is highly desirable from an environmental point of view.…”

Selectivity Tailoring in Liquid Phase Oxidation Over MWNT-Mn3O4 Nanocomposite Catalysts

“…Catalytic liquid phase oxidation of alkyl groups in substituted phenols is a core technology in fine chemicals and pharmaceutical industries. − Therefore developing new materials by modifying their intrinsic properties has been a continuing effort for the last two decades. − The major challenges in developing new catalysts are (i) stability of the metal function without leaching under oxidation conditions, (ii) maintaining activity in the presence of antioxidizing substrates like cresols, (iii) tailoring selectivity to the desired oxidation products, particularly to the first step oxidation product, and (iv) minimizing reaction time as well as the catalyst concentration. p -Cresol oxidation is an example of industrial oxidation process which involves stepwise oxidation to give a mixture of p -hydroxy benzyl alcohol, p -hydroxy benzaldehyde, and p -hydroxy benzoic acid depending upon the catalyst used and reaction conditions. − ,, Among these, both alcohol and aldehyde derivatives are important intermediates for the manufacture of vanillin (a widely used flavoring agent), trimethoxy benzaldehyde, various agrochemicals, and pharmaceuticals such as semisynthetic penicillin, amoxicillin, and the antiemetic drug trimethobenzamide. ,, Efficient catalysts for oxidation reactions mainly involve oxides of transition metals having capability to form redox couples. In particular, Co-based catalysts systems and metals such as Cu, Mn supported on molecular sieves, carbon, or resins have been extensively studied for this oxidation reaction. − Apart from this, γ-Fe 2 O 3 has also been used as efficient catalyst, but it has been used for the oxidation of first step oxidation product of p -cresol, that is, p -hydroxy benzyl alcohol .…”

Heterogeneous Cobalt−Saponite Catalyst for Liquid Phase Air Oxidation of p-Cresol

“…These problems can be overcome by designing a suitable heterogeneous catalyst system which can possibly operate via Mars−van Krevelen mechanism in the liquid phase . Hydroxy benzaldehydes produced by the oxidation of corresponding phenol derivatives are important starting materials widely used in the manufacture of fragrances, soaps, preservatives, pharmaceuticals, etc. − One such example is p- cresol oxidation which gives p- hydroxy benzyl alcohol (PHBALc), benzaldehyde (PHB), and acid (PHBAcid) depending on the choice of catalysts and reaction conditions. − PHBALc and PHB are important intermediates for the manufacture of flavoring agents such as vanillin, various agrochemicals and pharmaceuticals, for example, amoxicillin, semisynthetic penicillin, and the antiemetic drug trimethobenzamide, and liquid crystals. − Recently, we have reported the activity of synthetic saponite containing Co 2+ in the octahedral layer for a liquid phase oxidation of p- cresol . Saponite clay is an example of trioctahedral smectite in which the charge imbalance due to isomorphic substitutions in the structure layers is compensated for by cations placed in the interlamellar position .…”

“…[13][14][15] Recently, we have reported the activity of synthetic saponite containing Co 2+ in the octahedral layer for a liquid phase oxidation of p-cresol. 16 Saponite clay is an example of trioctahedral smectite in which the charge imbalance due to isomorphic substitutions in the structure layers is compensated for by cations placed in the interlamellar position. 17 Therefore, the Co-saponite obtained can be viewed as a nanocomposite (100 nm) of Co phases over aluminosilicate support as a catalyst for oxidation reactions.…”