Selective Liquid Phase Oxidation Research Articles

Selective conversion of stearic acid into high-added value octadecanedioic acid using air and transition metal acetate bromide catalyst: Kinetics, pathway and process optimization

Liquid phase selective homogeneous catalytic oxidation of stearic acid (SA) was carried out to obtain industrially important carbon neutral high-added value octadecanedioic acid (ODDA). The oxidation was carried using air, cobalt(II)-acetate, manganese(II)-acetate and HBr catalyst in acetic acid (AcOH) solvent at an elevated temperature and pressure. SA oxidation products were analyzed by gas chromatography–mass spectrometry (GC–MS), gas chromatography (GC) and CO2 analyzer, and SA was oxidized selectively to ODDA without producing CO2 and intermediates like alcohols, aldehydes and ketones. The effect of SA loading (5–20%), pressure (2.8–5.8 barg) and temperature (353–383 K) on ODDA yield was studied by varying one variable at a time. Central composite design assisted response surface methodology was employed to find (i) the optimal design of experiments involving several combination of cobalt(II)-acetate (Co: 0–700 ppm), manganese(II)-acetate (Mn: 0–700 ppm) and HBr (Br–: 0–1144 ppm) and (ii) the most influencing variable and interaction among the variables. The synergistic effect of cobalt(II)-acetate in presence of HBr was observed and suggested that SA oxidation proceeds via bromine-bromide cycle. The elevated temperature and pressure along with reduced SA loading enhanced the yield of ODDA. The maximum ODDA yield was found to be 90.5% and corresponding optimum cobalt (II), manganese (II) and bromide concentration were 600.4, 452.2 and 1016.6 ppm, respectively, at fixed SA:AcOH-10:90, pressure-2.8 barg and temperature-383 K. Finally, SA oxidation kinetic analysis was determined based on the pseudo-first order homogeneous catalysis and found to be kinetically controlled with an average activation energy 34.55 kJ mol−1. The proposed kinetic model fitted well with the time-variant experimental SA and ODDA concentration under varying operating condition with percent average absolute deviation less than 5.0%.

Controlled synthesis of CuxMn3.66−xMo3O12 with the citrate sol–gel method for the selective liquid-phase toluene oxidation to benzaldehyde by air

A systematic study on the synthesis of the CuxMn3.66−xMo3O12 using citrate sol–gel technique is presented. The influence of the copper substitution, citric acid concentration and pH of the precursor solution on the exclusive formation of Cu–Mn–Mo polymetallic oxide are studied. The physicochemical properties of as-prepared oxides are characterized by XRD, ICP-MS, SEM, TEM, XPS, FT-IR, BET, and H2-TPR, and their dependence on the conditions of synthesis is explored. It is found that these three synthesis factors remarkably alter the crystal phases and surface structures. The catalytic behaviors of synthesized catalysts for liquid-phase toluene oxidation are evaluated with toluene-catalyst mixture under uniformly distributed conditions. The evaluation reveals that the ratios of Mn3+/Mn2+ as well as Oads/Olat on catalysts play a crucial role in the activity and selectivity. Factors effecting reaction parameters, such as reaction temperature, residence time, catalyst weight, promoter weight, airflow rate and the volume ratio of substrate to solvent, are investigated in detail. The reusability of the catalyst is examined through conducting repeat runs with the same catalyst, exhibiting no significant decline in its activity even after 8 runs. A toluene conversion of 60% with 57.4% selectivity toward benzaldehyde is observed after 4 h over the high-crystalline CuxMn3.66−xMo3O12 nanoparticles.

Comparison of titanosilicates with different topologies as liquid-phase oxidation catalysts

• Four titanosilicates were investigated in the liquid phase oxidation reactions. • Ti-MCM-68 and Ti-MWW were more active in the epoxidation of alkenes reactions. • Ti-MCM-68 was inferior to other three titanosilicates in the ammoximation reactions. • Ti-MCM-68 could reach high cyclohexanone conversion and oxime under suitable condition. Titanosilicates, with isolate and tetrahedrally coordinated Ti 4+ ions in zeolite framework, have shown their great potentials in the liquid-phase selective oxidation reactions. The usage of H 2 O 2 as the oxidant helped to build up environment-friendly chemical processes by giving H 2 O as the sole co-product. Four titanosilicates of Ti-MCM-68, Ti-MOR, Ti-MWW and TS-1, with distinct crystalline topologies, were included in present study, whose catalytic performances were compared in the epoxidation of alkenes and the ammoximation of ketones. Ti-MCM-68, as a recently discovered titanosilicate, showed attractive advantages in the epoxidation reactions, while its catalytic performance in the ammoximation reactions was inferior to the other three titanosilicates. However, the cyclohexanone conversion and oxime selectivity could reach ∼99% over Ti-MCM-68 titanosilicate under optimized reaction conditions, indicating that it could also be taken as a promising catalyst for ammoximation reaction.

Selective liquid phase oxidation of cyclohexene over magnetic Fe3O4/graphene oxide nanocomposite

Magnetic graphene based nanocomposite catalysts were used for the first time in cyclohexene oxidation reaction. Fe3O4 was found to be the active phase of Fe in the catalysts as evident from the XRD analysis of the samples. Presence of graphene as graphene oxide in the nanocomposites is confirmed from FTIR spectral analysis. The distribution of more or less spherical particles of Fe3O4 over the graphene sheets was evident from the TEM photographs. The activity of bare Fe3O4 increased drastically upon graphene incorporation. Maximum conversion of 92% was attained using tert-butyl hydroperoxide as the oxidant over the best nanocomposite catalyst in which Fe3O4 was supported over 2 wt% graphene oxide. Using H2O2, double bond oxidation was the major reaction (78.27% conversion) and 1,2-cyclohexane diol was the major product (87.89% selectivity) under the selected reaction conditions of 0.05 g of catalyst with 5 mL of acetonitrile solvent at 70 °C in the 6 h reaction between 2 mmol of cyclohexene and 10 mmol of oxidant. Catalysts recovery from the reaction mixture was very easy by the use of a magnet that in turn facilitated the effective reusability of the Fe3O4 /graphene nanocomposite. The reused catalyst was characterized using TEM and FTIR spectral analyses and it is found that the partial loss in activity can be a resultant of the oxidation of graphenic C=C and the formation of epoxy linkage and –OH groups in the sheets, which hinders the efficient electron migration during catalysis.

CATALYSTS OF OXIDATION REACTION OF BUTENE-1 TO METHYLETHYLKETONE

The available and simple metal complex systems of catalytic oxidation of unsaturated hydrocarbons were developed. It is shown that these systems catalyze the selective liquid-phase oxidation of butene-1 to methyl ethyl ketone by molecular oxygen at low temperature. The best results were revealed using Cu(I)Cl monovalent chloride. The catalyst for the production of methylethylketone is a binary system containing complexes of copper and palladium chloride at a molar ratio of 2:1. Hexamethylphosphoramide is used as the ligand and palladium chloride complex as an additional complex contains benzonitrile. A combined catalyst has been offered. It allows to carry out the oxidation reaction of butene to methyl ethyl ketone under mild conditions (low temperature, atmospheric pressure) with high selectivity and yield of the desired product. The proposed binary system is able to coordinate molecular oxygen and butene-1, and thus it becomes possible to conduct the oxidation reaction not directly between butene-1 and O2, and using a specific complex catalyst system allowing them to react with each other in an activated coordinated state. Absorption properties of catalysts synthesized on the bases of transition metals have been studied and activation of molecular oxygen and butane-1 has been determined. As a result of interaction of coordinated oxygen and butane-1 it is possible to carry out oxidation reaction to methylethylketone in mild condition. The specific feature of the offered binary catalyst is irreversible absorption of molecular oxygen. Mild conditions of the reaction proceeding decreases considerably amount of by-products and simplify obtaining and separation of the main product-methylethylketone. Due to the fact that the absorption of O2 is irreversible and it is possible to easily remove the excess amount of O2 after the formation of the oxygen complex. The developed method has the advantage from the point of view of safety.Forcitation:Agaguseynova M.M., Amanullayeva G.I., Bayramova Z.E. Catalysts of oxidation reaction of butene-1 to methylethylketone. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 53-57

Liquid Phase Selective Catalytic Oxidation of Oleic Acid to Azelaic Acid Using Air and Transition Metal Acetate Bromide Complex

AbstractIndustrially important di‐carboxylic acids are synthesized from mono‐carboxylic unsaturated and unsaturated fatty acids. In this study, the aim is to perform the simultaneous catalytic oxidative C=C cleavage of oleic acid (OA) to azelaic acid and pelargonic acid, and oxidation of the terminal methyl group in pelargonic acid to azelaic acid using cobalt‐ and manganese‐acetate as catalyst, hydrogen bromide as co‐catalyst and air in acetic acid at elevated pressure (2.8–5.8 barg) and temperature (353–383 K). Oxygen solubility is determined under varying pressure, temperature and OA loading. The effect of OA loading, pressure and temperature on OA conversion and azelaic acid selectivity is studied by varying one variable at a time; however, the presence of the synergistic effect of the catalyst and co‐catalyst is investigated by central composite design assisted response surface methodology. Oxidation of terminal methyl group in saturated fatty acid is also confirmed by the oxidation of stearic acid to octadecanedioic acid using identical oxidation conditions of OA. Oxidation products of fatty acids are quantified by gas chromatographic analysis. The innovation of the work is thus the ability of the catalytic system to perform a total oxidation of a terminal methyl group of the hydrocarbon chain. OA oxidation kinetics relating to catalyst and co‐catalyst concentration along with oxygen solubility at elevated temperature and pressure is established. The frequency factor and activation energy for OA oxidation is determined using the Arrhenius equation.

Coupling Molecular and Nanoparticle Catalysts on Single Metal–Organic Framework Microcrystals for the Tandem Reaction of H2O2 Generation and Selective Alkene Oxidation

A molecular catalyst, (sal)MoVI, and a heterogeneous catalyst, either Pd or Au nanoparticles (NPs), were integrated into one UiO-66 MOF microcrystal. The resulting dually functionalized catalysts, Pd@UiO-66-(sal)Mo and Au/UiO-66-(sal)Mo, have been utilized for a one-pot tandem reaction of H2O2 generation and selective liquid-phase alkene oxidation. The NPs serve as catalysts for the production of H2O2 from H2 and O2 gases, while the (sal)Mo moieties function as the oxidation catalyst. When the metal NPs are fully encapsulated within the MOF microcrystals, the alkene hydrogenation side reaction is largely suppressed, with a 6-fold decrease in the hydrogenation/oxidation product ratio for 5-bromo-1-cyclooctene favoring the epoxide as the major product. For Au/UiO-66-(sal)Mo, where the two catalysts are in close proximity on the MOF microcrystal, the enhancement in oxidation productivity is increased by 10 times in comparison to the [Au/UiO-66-NH2 + UiO-66-sal(Mo)] physical mixture of the two singly function...

Pt catalysts supported on ion exchange resins for selective glycerol oxidation. Effect of Au incorporation

In this paper, bimetallic Pt-Au catalysts were studied for the selective liquid phase oxidation of glycerol. The support used was a macroporous weak anion exchange resin. Two different preparation methods were employed: simultaneous exchange of both metals, and a sequential exchange using the controlled surface reaction technique. PtAu catalysts with a total metal content of 0.4wt% were prepared, with different Pt:Au molar ratios: 1:1; 2:1 and 1:2. The monometallic Au catalyst resulted inactive for the reaction. Nevertheless, it was found that the addition of Au improved the monometallic Pt catalyst activity. XPS results suggest the formation of a Pt-Au alloy, which could be related with conversion improvement. Not only the presence of Pt-Au alloyed particles, but also the Pt/Au ratio on the catalyst surface influences the activity. When the Au particles reduced on top of Pt (controlled surface reaction method), the Pt amount exposed at the catalyst surface was considerably reduced. For this reason, this Pt-Au sample did not show a significant improvement of conversion with respect to the monometallic platinum.

Carbon Quantum Dots-TiO2 Nanocomposites with Enhanced Catalytic Activities for Selective Liquid Phase Oxidation of Alcohols

Carbon quantum dots-titanium dioxide composite (CQDs-TiO2) has been synthesized by a simple hydrothermal process. It was used as a heterogeneous catalyst for oxidation of alcohols using water as a solvent. The morphologies and composition of the resulting catalysts were characterized to show that the CQDs were uniformly dispersed on the surface of the TiO2 with well combination with each other. The obtained catalyst showed enhanced catalytic activities compared to the pure CQDs catalyst. The enhanced catalytic activities were mainly attributed to the highly dispersive CQDs with more active centers which caused by the TiO2 support. The CQDs-TiO2 catalyst can also be reused without any significant loss in their catalytic activities after five times.

Selective liquid phase oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over γ-Al2O3 supported copper and gold nanoparticles

Benzyl alcohol oxidation to benzaldehyde was performed by tert-butyl hydroperoxide (TBHP) in the absence of any solvent using γ-Al2O3 supported copper and gold nanoparticles. Li2O and ionic liquids were used as additive and stabilizers for the synthesis of the catalysts. The physico-chemical properties of the catalysts were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction spectroscopy (XRD), N2 absorption/desorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and temperature programmed reduction (TPR), whereas, the oxidation reaction was followed by gas chromatography with a flame ionization detector (GC-FID). The as prepared catalysts exhibited good catalytic performance in terms of conversion and selectivity towards benzaldehyde. The performance of the Au-based catalysts is significantly higher than that of the Cu-based catalysts. For both Cu and Au catalysts, the conversion of benzyl alcohol increased as the reaction proceeds, while the selectivity for benzaldehyde decreased. Moreover, the catalysts can be easily recycled and reused with neither significant loss of activity nor selectivity. A kinetic study for the Cu and Au-catalyzed oxidation of benzyl alcohol to benzyldehyde is reported. The rate at which the oxidation of benzyl alcohol is occurring as a function of catalyst and oxidant amounts was investigated, with the apparent rate constant, kapp being proportional to the amount of nano catalyst and oxygen present in the system.

ChemInform Abstract: Alkyl‐1,4‐Benzoquinones ‐ From Synthesis to Application

AbstractReview: [122 refs.

ChemInform Abstract: Liquid‐phase Selective Oxidation Catalysis with Metal‐organic Frameworks

AbstractReview: 72 refs.

Catalytic evaluation on liquid phase oxidation of vanillyl alcohol using air and H2O2 over mesoporous Cu-Ti composite oxide

A mesoporous, highly crystalline Cu-Ti composite oxide catalyst was prepared via facile, simple and modified solution method varying Cu and Ti ratio for selective liquid phase oxidation of vanillyl alcohol. Various spectroscopic procedures were employed to systematically characterize the catalyst structural and physicochemical properties. The defect chemistry of the catalyst was confirmed from the presence of surface defects revealed through HRTEM imagery between the TiO2 (101) and Cu3TiO4 (012) planes, complemented by the XRD profiling. Further, presence of oxygen vacancy evidenced by O 1s XPS spectra were observed on the catalyst surface. Moreover, the stoichiometry of Cu and Ti in the catalyst synthesis protocol was notably found to be the vital determinant to alter the redox properties of Cu-Ti composite oxide catalyst supported by H2-TPR. O2-TPD analysis. Moreover, a rational investigation was done using different oxidants such as air and H2O2 with variables reaction conditions. The catalyst was active for liquid phase oxidation of vanillyl alcohol to vanillin with performance of 66% conversion and 71% selectivity using H2O2 in base free condition. And also, catalytic activity was significantly improved by 94% conversion with 86% selectivity to vanillin in liquid phase aerobic oxidation at the optimum reaction conditions. To expand the superiority of the catalyst, three times reusability study was also examined with appreciable catalytic activity.

New Hybrid Iron Phosphonate Material as an Efficient Catalyst for the Synthesis of Adipic Acid in Air and Water

A new organic–inorganic hybrid iron phosphonate material (FePO-1-2) has been synthesized hydrothermally using etidronic acid (1-hydroxyethylidene-1,1-diphosphonic acid) as an organophosphorus precursor. Under optimized reaction conditions the synthesis has been carried out hydrothermally for 3 days at 180 °C temperature at near neutral pH. The material has been characterized thoroughly by various techniques and its crystal structure has been indexed to a new orthorhombic phase with unit cell parameters of a = 10.995 A, b = 10.395 A, c = 11.793 A, and α = β = γ = 90°. The considerably good Brunauer–Emmett–Teller (BET) surface area of 236 m2 g–1, pore volume of 0.229 cm3 g–1, and robust nature of FePO-1-2 have motivated us to explore its catalytic activity in liquid phase partial oxidation reactions under green conditions. FePO-1-2 exhibits excellent catalytic activity (96% product selectivity, 72% conversion) for selective liquid phase oxidation of cyclohexanone to adipic acid in the presence of molecular ...

Liquid-phase selective oxidation catalysis with metal-organic frameworks

This short review paper summarizes our recent developments in liquid-phase selective oxidation catalysis with redox active Cr- and Fe-based metal-organic frameworks (MOFs), MIL-101 and MIL-100, using environmentally benign oxidants—molecular oxygen, tert-butyl hydroperoxide and hydrogen peroxide. The impact of the transition metal nature on the reaction selectivity and the most interesting features of the oxidation catalysis by the MOFs are addressed. Insertion of catalytically active metal-oxygen polyanionic clusters into the cages of MIL-101 to induce new catalytic properties is also discussed. An attempt is made to establish relationships between adsorption properties of the MOFs and peculiarities of their catalytic performances. Special attention is paid to the nature of the catalysis and catalysts stability and reusability. A comparison of the selected MOFs with conventional single-site heterogeneous catalysts (transition-metal-substituted zeolites, aluminophosphates and mesoporous silicates) is provided, and the scope and limitations of the MOF catalysts are discussed.

Interface structural effect of ruthenium-cerium oxide nanocomposite on its catalytic activity for selective oxidation of bioterpenes-derived p-cymene

An efficient catalyzed liquid-phase selective oxidation of p-cymene to tertiary cymene hydroperoxide (TCHP) and its derivative p-methylacetophenone (PMAP) was achieved over a nanostructured ruthenium-cerium oxide (Ru/CeO2) composite catalyst with remarkable activity using a green molecular oxygen oxidant. Both of the composite catalysts were prepared from CeO2 oxide with different particles sizes [i.e., bulk CeO2 (Ru/b-CeO2) and nanosized CeO2 (Ru/n-CeO2)]. The n-Ru/CeO2 exhibited high catalytic activity for the free-radical driven oxyfunctionalization reaction of the inert CH bond in p-cymene to afford up to 55% conversion within 5h at 65% TCHP and 26% PMAP selectivity. The combined ratio of the TCHP/PMAP selectivity was dependent on the reaction time and the amount of p-cymene conversion. An increase in the reaction time resulted in converted large amount of TCHP to PMAP. The better catalytic performance of the Ru/n-CeO2 catalyst compared to Ru/b-CeO2 was partially due to the catalyst redox and oxygen vacancies effect. Both the reduced and oxidized forms of Ru/n-CeO2 were investigated to gain insight into the active form of the catalyst. The reduced Ru/n-CeO2 catalyst exhibited poor performance compared to the high catalytic performance of the oxidized form. This result demonstrated the significant concomitant effect of the balanced Ru4+/Ru3+ and Ce4+/Ce3+ redox combination to facilitate the free-radical driven mechanism via the excitation of O2 to activate the substrate inert CH. The Ru/n-CeO2 catalyst was highly recyclable with consistent activity after its sequential re-use. The catalytic performance of Ru/n-CeO2 was correlated to its structural characteristics based on the results from complimentary techniques, such as powder XRD, Raman spectroscopy, HRTEM, BET SA nitrogen physisorption, FESEM, H2-TPR and EDX. According to the characterization results, the enhanced catalytic performance of the Ru NPs loaded on CeO2 with nanosized particles was due to intrinsic metal-metal oxide interactions, enhanced redox cycles and high oxygen mobility resulting from structural defects of n-CeO2 that form oxygen vacancies compared to dispersed on the bulk CeO2 with large particles. The catalytic activity exhibited by Ru/CeO2 provides encouraging results to add to the class of active and stable catalysts for the activation of typical alkyl aromatic hydrocarbons, such as the p-cymene inert CH bond, for the selective introduction of an oxygen atom.

Transition Metal-Free Carbon Quantum Dots for Selective Liquid Phase Oxidation of Alcohols Using Water as an Only Solvent

Transition metal-free oxidation of alcohols catalyzed by carbon quantum dots (CQDs) with NaClO oxidant using water as an only solvent was developed. High quality CQDs were synthesized via a simple one-pot electrochemistry method using cheap graphite rod as substrate materials, without the assistance of any chemicals but only pure water. The morphologies and composition of the resulting catalyst were characterized in detail. The results indicated that the CQDs catalyst showed higher activity and selectivity comparing to other carbon based transition metal-free catalyst (such as carbon nanotubes, graphene et al.) in the selective oxidation of alcohols to aldehydes. The high performance of the CQDs can be mainly attributed to its small particle size and large amounts of surface oxygen containing groups. The CQDs catalyst can be reused five times without any significant loss in their catalytic activities.

Synthesis and characterization of RuO2@ZrO2 core–shell nano particles as heterogeneous catalyst for oxidation of benzylic alcohols in different conditions

In this study, new RuO2@ZrO2 core–shell nanoparticles have been produced using simple procedure and characterized by the spectroscopic methods (XRD and HR-TEM techniques). Catalytic activity of the synthesized nano powders has been investigated in the liquid-phase selective oxidation of benzyl alcohols. Also, the effect of some parameters such as optimum weight ratio for Ru doping, catalyst, oxidant type and various solvents was studied in room temperature, reflux, ultrasound, microwave conditions and UV–vis irradiation. The catalyst exhibits excellent activity and high conversion under mild conditions. Furthermore, this reagent was recycled and reused three times in the model reaction.

Hierarchical flower-like Co–Cu mixed metal oxide microspheres as highly efficient catalysts for selective oxidation of ethylbenzene

The selective oxidation of alkanes and alkylaromatics to corresponding alcohols, ketones or carboxylic acids is of great importance for the production of high added-value raw materials in the fine chemical industry. The design and synthesis of cost-effective and recyclable heterogeneous oxidation catalysts has become one of the most active research areas. In this work, a series of novel Al2O3@Co–Cu–Al mixed metal oxide (Al2O3@CoCuAl-MMO) catalysts with hierarchical flower-like microstructure were successfully prepared via a Co–Cu–Al layered double hydroxide precursor route, and their catalytic performance was investigated in the liquid-phase selective oxidation of ethylbenzene using tert-butyl hydroperoxide as oxidant without the addition of any organic solvents. The characterization results revealed that the incorporation of copper into the MMO could induce the formation of the interactions between the Co–Cu species, and thus catalytic performance of as-formed Al2O3@CoCuAl-MMO catalysts was significantly promoted. In the selective oxidation of ethylbenzene, a high conversion of 92.8% with an acetophenone selectivity of 89.4% was achieved over the Al2O3@CoCuAl-MMO catalyst with a Cu/(Cu+Co) molar ratio of 0.25. The high catalytic efficiency was attributed mainly to the synergistic effect between highly dispersed active Co and Cu species. More importantly, the obtained catalysts having good recyclability and stability displayed good catalytic performance in the oxidation of other alkanes and alkylaromatics including 1,2,3,4-tetrahydronaphthalene, toluene, cumene, and methylcyclohexane.

Mild ultrasound-assisted synthesis of TiO2 supported on magnetic nanocomposites for selective photo-oxidation of benzyl alcohol

A simple and effective ultrasound-assisted wet impregnation method was developed for the preparation of magnetically separable TiO2/maghemite-silica photo-active nanocomposites. The resulting nanomaterials were characterized by several techniques and subsequently tested for their photocatalytic activities in the liquid phase selective oxidation of benzyl alcohol. An unprecedented selectivity in organic media (90% in acetonitrile) towards benzaldehyde was achieved at a benzyl alcohol conversion of ca. 50%, being remarkably superior in terms of activity to any other supported transition metal catalysts reported to date as well as commercial titania Evonik P-25 photocatalyst.