Epoxidation Of Methyl Oleate Research Articles

Rational Design of Isolated Tetrahedrally Coordinated Ti(IV) Sites in Zeolite Frameworks for Methyl Oleate Epoxidation.

The rational design of isolated metals containing zeolites is crucial for the catalytic conversion of biomass-derived compounds. Herein, we explored the insertion behavior of the isomorphic substitution of Ti(IV) in different zeolite frameworks, including ZSM-35 (FER), ZSM-5, and BEA. The different aluminium topological densities of each zeolite framework lead to the creation of different degrees of vacant sites for hosting the tetrahedrally coordinated Ti(IV) active sites. These observations show the precise control of the degree of four-coordinated Ti(IV) sites in a zeolite framework, especially in BEA topology, by tuning the degree of unoccupied sites in the host zeolite structure via dealumination. Interestingly, the more vacancies in the host zeolite structure, the more isolated tetrahedrally coordinated Ti(IV) can be increased, eventually enhancing the catalytic performance in methyl oleate (MO) epoxidation for producing methyl-9,10-epoxystearate (EP). The engineered Ti-β exhibits outstanding performances in bulky MO epoxidation with the amount of produced EP per number of Ti sites up to 17.1±1.8 mol mol-1. This observation discloses an alternative strategy for optimizing catalyst efficiency in the rational design of the Ti-embedding zeolite catalyst, endeavoring to reach highly efficient catalytic performance.

Front Cover: Rational Design of Isolated Tetrahedrally Coordinated Ti(IV) Sites in Zeolite Frameworks for Methyl Oleate Epoxidation (Chem. Asian J. 20/2024)

Front Cover: Rational Design of Isolated Tetrahedrally Coordinated Ti(IV) Sites in Zeolite Frameworks for Methyl Oleate Epoxidation (Chem. Asian J. 20/2024)

A computer vision sensor for the parallelization of actively regulated capillary slug flow microreactors

In this work, a computer vision sensor for the extraction of slug length, slug velocity and phase ratio from capillary liquid–liquid slug flows from video feeds in real-time, including the necessary post-processing algorithms, is developed. The developed sensor is shown to be capable of simultaneously monitoring multiple capillaries and provides reasonable accuracy at less than 3.5% mean relative error. Subsequently, the sensor is used for the control of a parallelized and actively regulated dual-channel slug flow capillary microreactor setup. As a model reaction, the solvent-free epoxidation of methyl oleate with hydrogen peroxide and a phase-transfer catalyst based on tungstophosphoric acid and a quaternary ammonium salt to yield the product 9,10-epoxystearic acid methyl ester is conducted. A space–time yield of 0.679 kg L−1 h−1 is achieved.

Constructing 2D channel catalysts with accessible open transport channels for boosting epoxidation of methyl oleate

For the epoxidation of methyl oleate (MO), slow chemical reaction rate resulted from poor mass transfer remains a tough problem. Herein, we demonstrate a series of efficient 2D channel catalysts with accessible open transport channels, which provides an idea strategy for boosting epoxidation of MO and shortening its reaction time. 2D channel catalysts (2D-CSx-NH2-HPA) are fabricated by immobilizing heteropoly acid (HPA) on aminopropyl-functionalized 2D channel silica (2D-CSx-NH2), in which HPA is highly dispersed. These catalysts are applied to the epoxidation of MO, and the results show that the epoxidation performance of 2D channel catalysts for MO is related to its particle size and HPA types. As expected, the 2D-CS3.5-NH2-HPW with a length of 300 nm and an equatorial diameter of 150 nm exhibits outstanding catalytic activity (XMO = 91.68%) and epoxide selectivity (SEMO = 90.03%) with only 4 hours, which is much faster than that of majority of epoxidation catalysts reported so far. The excellent catalytic activity of 2D channel catalyst benefits from the appropriate pore width and particle size, which play an important role in exchanging substrates and dispersing active components. This study uses 2D channel catalyst to effectively shorten the reaction time of MO epoxidation, which paves a new avenue to develop other 2D channel materials for novel catalytic applications.

Effect of oxidant on the epoxidation of methyl oleate over transition metal-based Al2O3 catalysts

Various transition metal-based Al2O3 catalysts are employed for the epoxidation of methyl oleate (MO) as a representative compound of fatty acid methyl ester (FAME). Two different oxidants, H2O2 and O2, are used for the oxidative epoxidation reaction and resulted in significantly different activities according to the catalytic properties of the Al2O3 catalysts. The reactivity for H2O2-based epoxidation of methyl oleate is proportional to the acidity of the catalysts. On the other hand, in O2-based epoxidation, the reactivity is strongly dependent on the redox properties of the catalysts and O2 behavior on the catalyst surface. Mo and Cu-based catalysts show outstanding catalytic performance with H2O2 and O2 via different reaction pathways. These results provide valuable information on the promising combination between catalysts and oxidants, which will be a useful guide for designing catalyst reaction processes according to the kind of oxidizing agent.

Epoxidation of methyl oleate over various amorphous Ti–SiO2 catalysts

The epoxidation reaction of the vegetable oil derivative methyl oleate with tert-butyl hydroperoxide in the presence of amorphous Ti–SiO2 catalysts prepared by different methods using various silica sources was carried out. The reaction conditions were optimized. The relation between the properties of the catalysts such as specific surface area as well as titanium dispersion and the catalytic performance was in focus of the investigation. Based on the catalytic results in small batch reactors, the reaction was scaled up in a larger 4 L batch-reactor. Thereby similar conversions and selectivities were obtained in comparison with the small scale experiments.

Kinetic study of methyl oleate epoxidation under phase transfer catalysis by heat flow measurement

Kinetic study of methyl oleate epoxidation under phase transfer catalysis by heat flow measurement

1H NMR-based analytical method: A valid and rapid tool for the epoxidation processes

The present work aims to propose a 1H NMR-based method for a rapid determination of conversion, yield, and selectivity in the epoxidation of organic substrates. Several experiments were carried out on different substrates and analyzed with both the proposed 1H NMR method and the volumetric traditional ones for a useful comparison. The results obtained with the traditional methods were deeply studied to find a mathematical correlation between the absolute analytical error and the double bond or oxirane ring concentration. The same was done for the conversion and yield derived from the analytical determinations. Finally, the results obtained with the proposed 1H NMR-based method on the epoxidation of methyl-oleate, as a model molecule, were compared with the results obtained by the traditional methods. A good agreement was obtained between the two classes of methods validating the proposed 1H NMR method.

Catalytic Synthesis of Methyl 9,10‐dihydroxystearate from Technical Feedstocks in Continuous Flow via Epoxidation and Hydrolysis

AbstractThe sequence of the homogeneously Ru‐catalyzed epoxidation of methyl oleate and acid‐catalyzed hydrolysis of the corresponding epoxide methyl 9,10‐epoxy stearate is successfully transferred from batch into flow mode, allowing for the continuous production of methyl 9,10‐dihydroxystearate. Thereby, methyl oleate is first converted up to 97% within 14 min at excellent selectivity in the epoxidation using aqueous hydrogen peroxide as the sole oxidant. In the subsequent hydrolysis, a residence time of 10 min is sufficient for quantitative conversion of the epoxide. The desired, pure vicinal diol is isolated upon crystallization from the crude reaction mixture in an integrated process starting from technical grade (91.5%) substrate. The isolated yield is increased upon the addition of water as a green antisolvent from 75% up to 97%. Finally, the concept is transferred to methyl oleate of even lower purity (76%), still obtaining an isolated yield of 66% of the vicinal diol. Thus, the integration of sequential epoxidation and hydrolysis into continuous flow and subsequent crystallization allows for high conversion and selectivities within a total residence time of 27 min, corresponding to a space–time yield of 190 g h−1 L−1 in the epoxidation and 164 g h−1 L−1 in the hydrolysis, respectively.Practical applications: The modular flow setup enables the targeted functionalization toward the epoxide intermediate or the vicinal diol. Both offer versatile applications for the production of polymers, surfactants, or toward further conversion as in oxidative cleavage starting from methyl oleate. The application of flow chemistry offers advantages for the safe handling of hydrogen peroxide even at high temperatures. With fats and oils being natural substances, oleochemicals such as fatty acid methyl esters are typically available in technical purity so that efficient strategies for the isolation of pure products are of need. Crystallization of the product is promising, as additional organic solvents are not required. Thus, using the difference in melting point and solubility behavior of the desired product compared to other compounds is a promising method for the applicability of renewable resource‐based substrate mixtures.

A key role of soft and refractory coke in the deactivation of γ–Al2O3 catalysts during low-temperature methyl oleate epoxidation: An experiment and DFT study

This work studies the deactivation of the γ-Al2O3 catalyst in a low-temperature methyl oleate epoxidation reaction. The performance at each cycle of spent catalyst correlated to the formation of soft and refractory coke on the catalyst was probed by the temperature-programmed oxidation analysis and FT-IR. As a result, soft coke contributed as the major coke species, including an ester functional group. Furthermore, the coke adsorption on the surface and the electron transfer was analyzed by density functional theory-based calculation. It was found that the strongly adsorbed refractory coke on the catalyst is prone to adsorb on the main Al active site blocking the formation of the Al–OOH site. This phenomenon is responsible for the main reaction in contrast to the soft coke that prefers the other Al sites. Thus, controlling the refractory coke formation is crucial to control the overall catalyst performance, although present in a small amount.

Efficient and clean epoxidation of methyl oleate to epoxidized methyl oleate catalyzed by external surface of TS-1 supported molybdenum catalysts

Methyl oleate (MO) macromolecules are unable to access the microporous channel of conventional titanium silicalite-1 (TS-1) zeolite, which leads to the low catalytic activity of epoxidation of MO. Herein, the small-size TS-1 (TS-1-s) zeolite with a large surface area was synthesized successfully through steam-assisted crystallization, and then a novel blocked TS-1-s supported molybdenum (Mo/TS-1-bs) catalysts were prepared for efficient epoxidation of MO with clean H 2 O 2 to produce epoxidized methyl oleate (EMO). Various characterization results show the introduced Mo species are highly dispersed on the outer surface of TS-1-s without destroying the structure of the MFI type zeolite and the tetrahedral framework titanium (Ti 4+ ). Interestingly, a large number of Mo 6+ species exhibit certain epoxidation activity attributing to the generating of electrophilic molybdenum hydroperoxide (Mo–OOH) species via Mo species combined with H 2 O 2 , which could adsorb and react easily with MO molecules. Furthermore, the Mo species are also coordinated with Ti 4+ species through the O atom resulting in the facile attack of the Ti–O bonds by H 2 O 2 and easy to form an active intermediate. Therefore, compared with the conventional TS-1, the Mo/TS-1-bs shows higher catalytic activity in the epoxidation reaction. However, the acidity of Mo/TS-1-bs catalysts increases with increasing the Mo-loading owing to the formation of Lewis acid, which leads to the side reactions and the decrease of EMO selectivity. As a consequence, the efficient, non-corrosive and green catalytic system for epoxidation of MO was developed, and the activity improvement of Mo species and the influence of acid were also demonstrated. • The clean small-size TS-1 and Mo/TS-1-bs catalysts were prepared successfully for epoxidation of methyl oleate (MO). • Mo species can promote the MO epoxidation through generating of molybdenum hydroperoxide and coordination with Ti 4+ . • The acidity of Mo/TS-1-bs catalysts can decrease the selectivity of epoxidized methyl oleate.

Enhanced stability of Ti-containing silica catalysts for biodiesel epoxidation with hydrogen peroxide: Presence of strong metal–support interactions for alleviating permanent deactivation

The deactivation of titanium catalysts supported by well-ordered silica (SBA-15) and amorphous fumed silica synthesized by incipient wetness impregnation (IWI) and wet impregnation (WI) was comparatively investigated during epoxidation of methyl oleate with H2O2 at 50 °C. The formation of oxygen vacancies during epoxidation resulted in the loss of active species, leading to permanent catalyst deactivation. The WI-based catalysts exhibited superior stability to that of the IWI-based equivalents. Moreover, the use of SBA-15 as a support enabled higher stability than that of SiO2. The permanent deactivation rates for the 4Ti/SiO2-IWI, 4Ti/SBA-15-IWI, 4Ti/SiO2-WI, and 4Ti/SBA-15-WI catalysts were approximately 44.0%, 32.6%, 8.1%, and 0%, respectively. Various catalyst characterization data revealed that the configuration featuring stable surface Ti was present in the 4Ti/SBA-15-WI catalyst with strong metal–support interactions. This was attributed to the strong Ti4+ tetrahedral coordination achieved through Si–O–Ti bonds, the low degree of reducibility of the Ti catalyst, and the high dispersion and small particle size of Ti. Consequently, this modified surface can mitigate permanent catalyst deactivation caused by the surface oxygen vacancies.

Slug flow as tool for selectivity control in the homogeneously catalysed solvent-free epoxidation of methyl oleate

Catalytic oxidation of sustainable raw materials like unsaturated fats and oils, or fatty acids and their esters, lead to biobased, high-value products. Starting from technical grade methyl oleate, hydrogen peroxide as a green oxidant produces only water as by-product. A commercially available, cheap water-soluble tungsten catalyst is combined with Aliquat® 336 as a phase-transfer agent in solvent-free reaction conditions. In this study, we first report the transfer of this well-known batch system into continuous mode. The space–time yield is improved from 0.08 kg/L.h in batch to 1.29 kg/L.h in flow mode. The improved mass transfer and reduced back mixing of the biphasic liquid–liquid slug flow allows for selectivity control depending on physical parameters of slug flow namely volumetric phase ratio, volumetric flow rate, and slug length. Even though the product, methyl 9,10-epoxystearate is obtained at a maximum selectivity of only 58% in flow mode, higher space time yield combined with possible reactant recycling in flow mode offers a promising avenue of research. This work analyses the use of slug flow parameters as tools for controlling selectivity towards oxidation products of methyl oleate.

Highly efficient Co single-atom catalyst for epoxidation of plant oils.

Epoxidation of bio-derived plant oils is a sustainable route to manufacturing plasticizers, additives in lubricants, and other chemicals. The traditional synthetic approaches suffer from the employment of corrosive mineral acid or expensive peroxides (e.g., H2O2). In this work, we report the epoxidation of plant oils using O2 as the terminal oxidant catalyzed by Co-N-C/SiO2 single-atom catalyst. The single-atom dispersion of cobalt is confirmed by high-angle annular dark field-STEM and x-ray absorption fine structure techniques. In the epoxidation of methyl oleate under mild reaction conditions (35 °C, 0.1 MPa O2), 99% selectivity to the desired product is achieved at full conversion. Even for crude oils, Co-N-C/SiO2 is also effective and good yields of the corresponding epoxides are obtained. In addition, the catalyst is easily recovered and can be reused five times without obvious decay in catalytic activity/selectivity. A superoxide radical involved reaction mechanism is proposed on the basis of kinetic study and EPR experiment.

A Key Role of Soft and Refractory Coke in the Deactivation of γ--Al <sub>2</sub>O <sub>3</sub> Catalysts During Low-Temperature Methyl Oleate Epoxidation

A Key Role of Soft and Refractory Coke in the Deactivation of γ--Al <sub>2</sub>O <sub>3</sub> Catalysts During Low-Temperature Methyl Oleate Epoxidation

Performance controlled via surface oxygen-vacancy in Ti-based oxide catalyst during methyl oleate epoxidation

The catalytic performance with high conversion and high selectivity of Ti-based oxide catalysts have been widely investigated. Besides, stability, which is an essential parameter in the industrial process, lacked fundamental understanding. In this work, we combined computational and experimental techniques to provide insight into the deactivation of P25 and TS-1 Ti-based oxide catalysts during the methyl oleate (MO) epoxidation. The considered deactivation mechanisms are fouling and surface oxygen vacancy (OV). The fouling causes temporary catalyst deactivation through active site blockage but can be removed via calcination in air at high temperature. However, in this work, the OV formation plays an important role in the overall performance of the spent catalyst as the deactivated catalyst after regeneration, cannot be restored to the initial activity. Also, the effects of OV in spent catalysts caused (i) the formation of more Ti3+ species on the surface as evident by XPS and Bader charge analysis, (ii) the activity modification of the active region on the catalyst surface as the reduction in energy gap (Eg) occurred from the formation of the interstates observed in the density of states profiles of spent catalyst modeled by the O-vacant P25 and TS-1 models. This reduction in Eg affects directly the strength of Ti–OOH active site and MO bonding, in which high binding energy contributes to a low conversion because the MO needed an O atom from Ti–OOH site to form the methyl-9,10-epoxy stearate. Hence, the deactivation of the Ti-based oxide catalysts is caused not only by the insoluble by-products blocking the active region but also mainly from the OV. Note that the design of reactive and stable Ti-based oxide catalysts for MO epoxidation needed strategies to prevent OV formation that permanently deactivated the active region. Thus, the interrelation and magnitude between fouling and OV formation on catalyst deactivation will be investigated in future works.

Integrated fast-mass transfer and high Ti-sites utilization into hybrid amphiphilic TS@PMO catalyst towards efficient solvent-free methyl oleate epoxidation

For solvent-free catalytic oxidations, low efficiency resulted from poor mass transfer and insufficient utilization of active centers remains a tough problem. Herein, we demonstrate a novel hybrid core-shell catalyst (TS@PMO) with an amphiphilic shell and a Ti-surface-enriched mesoporous TiO2-SiO2 (TS) core to address this challenge. Such TS@PMO realizes its amphiphilicity via an ex situ formed periodic mesoporous organosilica (PMO) shell. Simultaneously, by a unique etching effect induced by organic precursor growth on [SiO4] tetrahedra in TS core, active Ti sites are facilely enriched in near-surface layer of core and extra mesoporous cavities are introduced for substrate reservation. When applied for solvent-free epoxidation of methyl oleate (MO) with H2O2, TS@PMO exhibits remarkably boosted catalytic activity (X = 90.2%) and epoxide selectivity (S = 70.2%), overwhelming the unmodified titanosilicate (X = 63.7%, S = 49.2%) and Ti-containing organosilica (X = 39.8%, S = 25.0%). Such result benefits from an evidently enhanced interphase mass transfer and sufficiently accessible active Ti sites in TS@PMO. On the one hand, amphiphilic PMO shell can efficiently collect hydrophobic substrate and H2O2, while abundant mesopores in the shell offer open-path for them to access active sites in the core; on the other hand, an increased framework Ti (IV) density and their surface-enrichment in TS core greatly improve the utilization of active Ti sites. This study effectively makes up for the deficiencies of slow mass transfer and insufficient utilization of conventional titanosilicates in biphasic reactions, which paves a new avenue to exploit other hybrid catalysts for high-efficiency solvent-free catalysis.

Organic groups-regulated high-efficiency catalysis of hybrid Ti-Containing mesoporous silicates for Bi-Phase interfacial epoxidation

The sluggish interfacial mass transfer usually hinders the achievement of high-efficiency catalytic transformation of biomass, especially for solvent-free immiscible reagent systems. Herein, amphiphilic hybrid Ti-containing catalysts in situ incorporated with organic groups (Cn-Ti-HMS) were developed for boosting biphasic solvent-free epoxidation of methyl oleate (MO) with H2O2. Benefiting from the mutual effect between organic/inorganic precursors, the resulting low-defect catalysts exhibit well-mediated surface hydrophilic/hydrophobic balance and porosity by incorporating alkyl groups. Such mediation effect exhibits two superiorities: i) accelerated adsorption of reactants by amphiphilicity; ii) boosted substrate or product diffusion by porosity property. As such, remarkably promoted catalytic properties were achieved when compared with conventional Ti-HMS. Typically, methyl-functionalized C1–Ti-HMS-50 displays the optimal catalytic performance with a 95% conversion of MO. Further mechanism study recognizes the dominant role of surface wettability and Si–OH defects content in influencing MO conversion and epoxidized MO selectivity.

Contribution of mesopores of hierarchically structured titanium silicalite-1 to the catalytic activity towards the methyl oleate epoxidation

Contribution of mesopores of hierarchically structured titanium silicalite-1 to the catalytic activity towards the methyl oleate epoxidation

Lyophilized extracts from vegetable flours as valuable alternatives to purified oxygenases for the synthesis of oxylipins

In this work, the whole aqueous extracts of soybean flour and oat flour have been used as valuable alternatives to purified oxygenase enzymes for the preparation of oxylipins derived from (5Z,8Z,11Z,14Z,17Z)-eicosapentaenoic acid (EPA). The lipoxygenase activity in the aqueous extracts of soybean (Glycine max. L.) flour was monitored with linoleic acid as substrate and compared with the commercially available purified enzyme (LOX-1). Oat flour extracts (Avena sativa L.) were evaluated for their peroxygenase activity by comparing different enzyme preparations in the epoxidation of methyl oleate. It was found that lyophilization of the aqueous extracts from these vegetable flours offers advantages in terms of enzyme stability, reproducibility and applicability to preparative organic synthesis. The lyophilized enzyme preparations were tested for the oxyfunctionalization of EPA and the formed products were isolated in satisfactory yields. In the presence of lyophilized extract from soybean, EPA gave 15S-hydroxy-(5Z,8Z,11Z,13E,17Z)-eicosapentaenoic acid in enantiopure form as exclusive product. Peroxygenase from oat flour was less selective and catalyzed the formation of different epoxides of EPA. However, the biocatalyzed epoxidation of EPA under controlled conditions allowed to obtain optically active (17R,18S)-epoxy-(5Z,8Z,11Z,14Z)-eicosatetraenoic acid (65% ee) as the main monoepoxide, among the five possible ones.