Revisiting the Enzymatic Epoxidation of Vegetable Oils by Perfatty Acid: Perbutyric Acid Effect on the Oil with Low Acid Value

Study on the epoxidation of chain olefins using biquaternary ammonium phosphotungstic acid phase transfer catalysts under no-solvent condition

In this study, we have developed a novel catalyst synthesized by phosphotungstic acid and a gemini quaternary ammonium cation salt. This quaternary ammonium salt not only reduces the interfacial tension between olefins and hydrogen peroxide but also forms a notably stable structure with phosphotungstic acid. Dodecene was successfully epoxidized to epoxy dodecane with a selectivity of 82.9 %. The impact of initial conditions was systematically investigated such as molar ratio, temperature, reaction time, and catalyst dosage on the catalytic performance. Characterization of the catalyst morphology was performed by SEM, TEM and SAXS. Raman spectra, FT-IR and XPS spectra were employed to perform the catalyst transformation during the epoxidation reaction. This catalytic mechanism study could provide the industrial application in the epoxidation of long-chain olefins.

Enzymatic and Synthetic Routes of Castor Oil Epoxidation

Epoxidation of castor oil in synthetic and enzymatic routes was carried out in order to promote a system with less environmental impact. The epoxidation reactions of castor oil compounds upon addition of lipase enzyme with and without acrylic immobilization and with reaction times of 24 and 6 h, as well as the synthetic compounds upon addition of Amberlite resin and formic acid, were investigated using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance in hydrogen molecules (¹H-NMR). The analysis indicated that the enzymatic reactions (6 h) and synthetic reactions provided a conversion from 50 to 96% and epoxidation from 25 to 48%, resulting from peak stretching and signal disintegration in the hydroxyl region due to the appearance of H₂O in the interaction of peracid with catalyst. In systems without toluene, a dehydration event with a peak absorbance of 0.02 AU, indicating a possible vinyl group at 2355 cm^-1 in enzymatic reactions without acrylic immobilization, was observed and resulted in a selectivity of 2%. In the absence of a solid catalyst, an unsaturation conversion of castor oil above 90% was achieved; however, this catalyst is necessary for the epoxidation to take place, whereas the lipase enzyme becomes able of epoxidizing and dehydrating the castor oil upon changing the time or reaction system. The conversation from 28 to 48% of solid catalysts (Amberlite and lipase enzyme) displays their importance to the instauration conversion of castor oil into oxirane rings.

Computational Studies Suggest Promiscuous Candida antarctica Lipase B as an Environmentally Friendly Alternative for the Production of Epoxides

Environmentally friendly processes are nowadays a trending topic to get highly desired chemical compounds and, in this sense, the use of enzyme-catalyzed routes is becoming a promising alternative to traditional synthetic methods. In the present paper, a hybrid quantum mechanics/molecular mechanics (QM/MM) computational study on the epoxidation of alkenes catalyzed by the Ser105Ala variant of the promiscuous Candida antarctica lipase B (CALB) is presented in an attempt to search for alternative paths to get useful intermediates in industries. The catalyzed reaction, described at the atomistic level with a model of the full solvated in a box of water molecules, is compared with the alternative epoxidation of alkenes by peroxy acids in chloroform. Free-energy profiles obtained at the density functional theory (DFT)/MM level show how Ser105Ala CALB is capable of epoxide short alkenes in a two-step process with free-energy barriers, in agreement with available experimental data, that are significantly lower than those of the single-step reaction in solution. The possible (R)-enantioselectivity dictated by the binding step, explored by means of alchemical QM/MM free-energy perturbation (FEP) methods, and the preference for the (S)-enantiomer derived from the free-energy landscape of the chemical steps would cancel out, thus predicting the lack of enantioselectivity experimentally observed. In general, our results provide general information on the molecular mechanism employed by a highly promiscuous enzyme, with potential applications in biotechnology.

The Lord of the Chemical Rings: Catalytic Synthesis of Important Industrial Epoxide Compounds

The epoxidized group, also known as the oxirane group, can be considered as one of the most crucial rings in chemistry. Due to the high ring strain and the polarization of the C–O bond in this three-membered ring, several reactions can be carried out. One can see such a functional group as a crucial intermediate in fuels, polymers, materials, fine chemistry, etc. Literature covering the topic of epoxidation, including the catalytic aspect, is vast. No review articles have been written on the catalytic synthesis of short size, intermediate and macro-molecules to the best of our knowledge. To fill this gap, this manuscript reviews the main catalytic findings for the production of ethylene and propylene oxides, epichlorohydrin and epoxidized vegetable oil. We have selected these three epoxidized molecules because they are the most studied and produced. The following catalytic systems will be considered: homogeneous, heterogeneous and enzymatic catalysis.

Preparation of cross-linked enzyme aggregates of lipase from Aspergillus niger: process optimization, characterization, stability, and application for epoxidation of lemongrass oil

Cross-linked enzyme aggregates (CLEAs) of lipase were prepared after fractional precipitation with 40-50% ammonium sulfate and then cross-linking with glutaraldehyde. The process variables for the preparation of lipase-CLEAs such as glutaraldehyde concentration, cross-linking period, and initial pH of medium were optimized. The optimized conditions for the preparation of lipase-CLEAs were 25 mM/80 min/pH 7.0, and 31.62 mM/90 min/pH 6.0 with one factor at a time approach and numerical optimization with central composite design, respectively. Lipase-CLEAs were characterized by particle size analysis, SEM, and FTIR. Cross-linking not only shifted the optimal pH and temperature from 7.0 to 7.5 and 40-45 to 45-50 °C, but also altered the secondary structure. Lipase-CLEAs showed an increase in K_m by 7.70%, and a decrease in V_max by 16.63%. Lipase-CLEAs presented better thermostability than free lipase as evident from thermal inactivation constants (t_1/2, D and E_d value), and thermodynamic parameters (E_d, ΔH°, ΔG°, and ΔS°) in the range of 50-70 °C. Lipase-CLEAs retained more than 65% activity up to four cycles and showed good storage stability for 12 days when stored at 4 ± 2 °C. They were successfully utilized for the epoxidation of lemongrass oil which was confirmed by changes in iodine value, epoxide value, and FTIR spectra.

Catalytic developments in the epoxidation of vegetable oils and the analysis methods of epoxidized products

Functionalization of vegetable oils (VOs) including edible, non-edible, and waste cooking oil (WCOs) to epoxides (EVOs) is receiving great attention by many researchers from academia and industry because they are renewable, versatile, sustainable, non-toxic, and eco-friendly, and they can partially or totally replace harmful phthalate plasticizers. The epoxidation of VOs on an industrial scale has already been developed by the homogeneous catalytic system using peracids. Due to the drawbacks of this method, other systems including acidic ion exchange resins, polyoxometalates, and enzymes are becoming alternative catalysts for the epoxidation reaction. We have reviewed all these catalytic systems including their benefits and drawbacks, reaction mechanisms, intensification of each system in different ways as well as the physicochemical properties of VOs and EVOs and new findings in recent years. Finally, the current methods including titrimetric methods as well as ATR-FTIR and 1H NMR for determination of conversion, epoxidation, and selectivity of epoxidized vegetable oils (EVOs) are also briefly described.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

Lipase-catalyzed transesterification of epoxidized soybean oil to prepare epoxy methyl esters

Epoxidized soybean oil methyl esters could be efficiently prepared with the transesterification of epoxidized soybean oil (ESBO) with a lower dosage of methanol using lipase Novozym 435 as catalyst. The optimum parameters were as follows: the molar ratio of 5:1 (methanol to ESBO), 5% Novozym 435 as catalyst, at 45 °C for 14 h, with a stirring speed of 600rpm, under which the epoxidized soybean oil methyl esters (ESBOME) could be obtained at a 95.7% yield. During the enzymatic transesterification process, the oxirane oxygen values were kept unchangeable, which indicated that excellent functional group tolerance could be achieved under such mild reaction conditions. In addition, the recyclability of the immobilized enzyme Novozym 435 in this transesterification process was examined and the results showed that the biocatalyst could be reused ten times without losing any reaction activity or selectivity. And the final products of ESBOME were also identified by IR and NMR analysis. The kinetic data obtained followed the Ping-Pong Bi mechanism model (Vmax = 6.132 mol·L-1min-1, Km,S = 0,0001 mol·L-1, Km, A = 796.148 mol·L-1, Ki, A = 0,0004 mol·L-1) with competitive inhibition by methanol.