Liquid Phase Oxidation Of Α-pinene Research Articles

Optimization of liquid-phase α-pinene oxidation with oxygen in presence of cobalt (II) stearate

Optimization of the liquid-phase oxidation of α-pinene was carried out using the Box plan. It was found that an increase in the temperature of the oxidation process in the interval 55–85 °C leads to an increase in the amount of polymers from 45 to 55 %, and a decrease in the air flow rate from 1000 to 600 ml/min – to a 10 % decrease in terpenic oxygencontaining compounds (verbenol, verbenon, epoxy α-pinene). Increasing the duration of oxidation from 5 to 15 h leads to a reduction in the content of α-pinene from 70 to 48 %, which indicates its high conversion. The results of the experimental plan have been processed, the optimum process conditions found, which ensure the maximum yield terpenic oxygencontaining compounds and a high conversion α-pinene with the minimum content of polymers in the oxidation products, have been calculated and confirmed in practice. It was established that at a temperature of 70–75 °C, an air flow rate of 1000 ml/min and an oxidation time of 5 h, the quantitative content of the main products was: terpenic oxygen-containing compounds – 27.04 %, monomers – 69.70 %, polymers – 30.30 %.

Enhanced catalytic oxidation of monoterpenes by zeolite-Y entrapped iron complex: spectral studies and mechanistic vision

[Fe(L)2(H2O)2]–Y complex (where, L = (Z)-2-((4-hydroxybenzylidene)-amino)benzoic acid) has been synthesized by Flexible Ligand (FL) method and characterized by chemical analysis (CHN, ICP-OES, TGA, AAS), diffraction method (XRD), absorption spectroscopy (FTIR, UV–Vis), BET and SEM techniques. To investigate the catalytic performance (activity, stability, and reusability), [Fe(L)2(H2O)2]–Y was employed as heterogeneous catalyst in the liquid phase oxidation of α-pinene and limonene with H2O2 oxidant. [Fe(L)2(H2O)2]–Y catalyzed the oxidation of α-pinene via free radical formation as confirmed by in-situ IR and DR UV–Vis spectroscopy. [Fe(L)2(H2O)2]–Y showed conversion of α-pinene (67%) and limonene (79%) with better TONs, which is far better performance than neat iron complex.

Biomass toward fine chemical products: Oxidation of α-pinene over sieves nanostructured modified with vanadium

Vanadium-containing molecular sieves (V-M(x)) were synthetized and applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with hydrogen peroxide at 70°C. It has been found that the vanadium content in V-M(x) materials affected the conversion of α-pinene and product distribution. The turnover numbers increased strongly with the decreasing of V content probably caused by a high V dispersion. The major products were verbenone, trans-sobrerol and campholenic aldehyde. The acid–base properties of V-M(x) affected the distribution of products formed via the isomerization of α-pinene oxide over Lewis acid sites to campholenic aldehyde while Brønsted acid sites brought about the formation of 1,2 pinanediol and trans-sobrerol by hydrolysis and by the opening of oxirane ring. The increase in V content in V-M(x) led to the increase in campholenic aldehyde, 1,2 pinanediol, trans- sobrerol and over oxidation products. Moreover, the effect of several solvents on the reaction oxidation was studied. The results showed that the highest α-pinene conversions are obtained in the following order: acetonitrile>ethanol>isoamyl alcohol>methyl ethyl ketone. Thus, using aprotic solvents, the catalytic activity was increased and the formation of alkyl glycol ethers as by-product was not observed.

Vanadium-containing nickel phosphate molecular sieves as catalysts for α-pinene oxidation with molecular oxygen: A study of the effect of vanadium content on activity and selectivity

Vanadium-containing nickel phosphate molecular sieves (V-VSB-5) were applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with molecular oxygen at 60°C. It has been found that the vanadium content in V-VSB-5 materials affects the conversion of α-pinene and product distribution. The conversion of α-pinene increases with increasing of V content. The major products were α-pinene oxide, verbenol and verbenone. Acid–base properties of V-VSB-5 affect the distribution of by-products formed via the isomerization of α-pinene oxide over Lewis acid sites and Brönsted acid sites to campholenic aldehyde and trans-carveol. The increase in V content in V-VSB-5 leads to the increase in isomerization of α-pinene oxide to trans-carveol and decrease in that to campholenic aldehyde.

Highly efficient and clean synthesis of verbenone over well ordered two-dimensional mesoporous chromium silicate catalysts

Two-dimensional mesoporous SBA-15 catalysts synthesized by different hydrothermal methods have been used, for the first time, in the liquid-phase oxidation of α-pinene with t-butyl hydrogen peroxide (TBHP) for the synthesis of verbenone (V O). The recyclable CrSBA-15 catalysts have also been reused in this reaction to find their catalytic activities. To investigate the leaching of chromium species on the silica surface, CrSBA-15(8) has been treated with ammonium acetate solution, and it has been also treated with boiling water for the investigation of hydrothermal stability. The treated CrSBA-15(8) catalyst has been used in the catalytic reaction for finding the effects of catalytic stability. The influences of various reaction parameters such as temperature, time, ratios of reactant (α-pinene-to-TBHP) have been extensively investigated for the synthesis of V O. In addition, the liquid-phase oxidation of α-pinene has been conducted with different solvents to find the best solvent with a good catalytic activity. On the basis of all investigations with a hypothetical reaction pathway of α-pinene oxidation, the CrSBA-15(8) catalyst is found to be a highly active, recyclable and promising heterogeneous catalyst in the liquid-phase oxidation of α-pinene for highly selective synthesis of V O. Furthermore, CrSBA-15(8) catalyst has higher selectivity of V O (88.2%) than other CrSBA-15 and CrMCM-41.

Ti-MCM-41 as catalyst for α-pinene oxidation: Study of the effect of Ti content and H 2O 2 addition on activity and selectivity

Ti containing mesoporous materials with a MCM-41 structure were applied as heterogeneous catalysts for the liquid phase oxidation of α-pinene with hydrogen peroxide at 343 K. The catalysts were characterized by N 2 adsorption, XRD and DRUV-Vis. The results obtained by varying the Ti content showed slight changes in the α-pinene conversion. The major products were verbenol, verbenone and campholenic aldehyde with a conversion about 12–16%. The yield of the reaction products was duplicated when an additional amount of H 2O 2 was added after 1 h of reaction. A high selectivity was obtained for the products of the allylic oxidation. A reaction mechanism was proposed in order to explain the obtained results.

Liquid-phase oxidation of α-pinene with oxygen catalyzed by carbon-supported platinum metals

The liquid-phase oxidation of α-pinene with oxygen at 70–90°C is studied in the presence of Pd, Pt, Ru, Rh, and Ir supported on carbon. The conversion of α-pinene and the selectivity of formation of the main reaction products, namely, verbenol (1), verbenone (2), and α-pinene oxide (3), depends on the nature of the metal, on its oxidation state and extent of dispersion, and on the admixtures introduced into the system. In the presence of the Pt catalysts and promoting admixtures of tetrahexylammonium chloride (Hex4NCl), the selectivity of formation of the most valuable oxidation products (1 + 2) reaches 50% at an α-pinene conversion of 20–30%. The fraction of resinlike oxidation products decreases in the presence of the catalysts. The results obtained are discussed in the framework of the radical mechanism of α-pinene oxidation.

Liquid phase oxidation of α-pinene initiated by ozone. 2: Formation of verbenol, verbenone and acid products

The formation of verbenol, verbenone and acids during liquid phase ozone-initiated oxidation of α-pinene has been investigated; temperature, ozone partial pressure and ozone initiation time were the variables studied. While increasing temperature promotes the formation of secondary products, the other two variables affect mainly the selectivity. Thus, an ozone partial pressure and ozone initiation time of 1014 Pa and 10 min, respectively, lead to the highest selectivities. Kinetic expressions for the formation of verbenol and verbenone, which are consistent with experimental data, have also been developed from a free radical mechanism.