Liquid Phase Oxidation Of Toluene Research Articles

Water-soluble arylhydrazone complexes based on Mn(II) and Cu(II) as catalysts for liquid-phase toluene oxidation

Novel hydrosoluble coordination compounds based on arylhydrazones of β-diketones and bearing first row transition metals, namely [Mn(μ-1κO1,2κO2-HL1)2(H2O)2]n (1) and [Cu(κO1O2N-L2)(DEA)] (2; DEA = diethanolamine), were synthesised and characterized. Their structural features were investigated using single crystal X-ray diffraction. The catalytic performance of the complexes was explored for liquid phase oxidation of toluene in homogeneous medium using aqueous tert‑butyl hydroperoxide (TBHP) and hydrogen peroxide (H2O2) as oxidants. Both catalysts demonstrated activity, producing a mixture of benzaldehyde, benzyl alcohol and benzoic acid. Under optimized conditions, in the presence of catalysts 1 and using an aqueous TBHP solution as oxidant, the oxidation of toluene yielded an overall 42.6 % of oxygenated products. Contrary to what has been regularly reported regarding selectivity for benzaldehyde, benzoic acid was the predominant product in this study (71 %).

Streamlined synthesis of iron and cobalt loaded MCM-48: High-performance heterogeneous catalysts for selective liquid-phase oxidation of toluene to benzaldehyde

Hydrothermal synthesis of MCM-48 molecular sieves featuring the incorporation of both iron and cobalt with Si/M ratios of 20, 40 and 80 (where M represents either iron or cobalt) was performed using tetraethyl orthosilicate as the silica source and cetyltrimethylammonium bromide as a template. To gain a comprehensive understanding of the synthesized materials, these were thoroughly characterized using various techniques, including XRD, XPS, UV–Vis (DRS), FT-IR, N2 adsorption-desorption analysis, SEM with EDX, TEM, TGA and NH3-TPD analysis. XRD analysis revealed the presence of well-ordered MCM-48 structure in the metal-incorporated materials, while XPS and UV–Vis DRS confirmed the successful partial incorporation of metal ions precisely in their desired tetrahedral coordination within the framework. To assess their catalytic performance, we studied the activity and selectivity of these catalysts in liquid phase oxidation of toluene using tert-butyl hydroperoxide as the oxidant. Under optimized conditions, employing a 6% (w/w) Fe-MCM-48 (40) catalyst and maintaining a toluene to oxidant molar ratio of 1:3 at 353 K in a solvent-free environment for 8 h, the oxidation reaction resulted in the formation of benzaldehyde (88.1%) as the major product and benzyl alcohol (11.9%) as the minor product.

REACTOR SİMULATİON DURİNG ANİLİNE SYNTHESİS

Study of reactor modeling in the process of aniline synthesis. Every year the demand for aniline is growing all over the world, and, accordingly, the capacity of its production. The areas of consumption of this product are different: the production of isocyanates used in the industry of building materials (foams, decorative parts, pipe insulation, etc.), in the shoe industry, additives to motor fuels; production of pharmaceutical preparations; organic dyes and pigments; herbicides.The object of study of this work is an industrial reactor related to shell-and-tube vertical apparatuses.The purpose of this work is to improve the process of synthesis of aniline using a mathematical model.The parameters of the equations describing the rate of the aniline synthesis process are determined; a mathematical model of an industrial reactor was developed taking into account the strong exothermicity of the aniline formation reaction.A computer model of the aniline synthesis reactor was developed, the adequacy of which was confirmed experimentally, allowing to determine the values of output characteristics in a wide range of changes in technological and design parameters; the influence of technological and design parameters on the process of aniline synthesis was studied. Based on the results of scientific research, 2 abstracts of conferences were published. Beginning in the early 1970s, American Cyanamide (USA) developed an original technology to produce aniline through the ammonolysis of benzoic acid. Benzoic acid was reacted with aqueous ammonia solution in the presence of cupric oxide at 215-220 °C and 3.5-4.2 MPa. Benzoic acid is produced according to known technology through the liquid phase oxidation of toluene with the help of cobalt salts at a temperature of 130-140 ° C and 0.21-0.22 MPa under strong heat removal conditions. Keywords: aniline synthesis. aniline production parameters, mathematical model of the reactor.

Facile synthesis, characterization, and catalytic activity of Cr(III) Schiff base complex immobilized on layered double hydroxide

In the chemical industry, designing high-performance catalysts for the oxidation of aromatic hydrocarbon into value-added products such as benzaldehyde and benzoic acid is critical. In this study, the catalytic activity of chromium Schiff base complex supported on layered double hydroxide for the liquid phase oxidation of toluene was examined. The chromium Schiff base complex supported catalyst was synthesized by the intercalation method and abbreviated as LDH-[NAPABA-Cr(III)]. The obtained material was characterized by various physical techniques such as ICP-AES, XRD, FTIR, SEM, EDX, TEM, TGA, and EPR. The catalytic activity of the heterogenized Cr(III) Schiff base complex was tested for the oxidation of toluene using tert-butyl hydroperoxide as an oxygen source. Furthermore, the hot filtration experiment revealed that the LDH-[NAPABA-Cr(III)] was a heterogeneous catalyst that could be reused at least seven times without significant loss of catalytic activity.

Toward the Accurate Prediction of Liquid Phase Oxidation of Aromatics: A Detailed Kinetic Mechanism for Toluene Autoxidation

Toluene is an important compound in the chemical industry as well as an often chosen simple surrogate compound for aromatic components in transport fuels. As a result, an improved understanding of the liquid phase oxidation of toluene is of interest to both the chemical industry and the transportation sector. In this work, a detailed autoxidation mechanism for the liquid phase oxidation of toluene is developed using an automated mechanism generation tool. The resultant mechanism is significantly improved using quantum chemistry calculations to update the thermodynamic parameters of key species in solution. Comparisons are made between the predicted and experimentally measured induction period and the obtained mechanism. The agreement between both is found to be within 1 order of magnitude. Rate of production analysis and sensitivity analysis are carried out to explain and understand the reactions paths present in the mechanism. The behavior of the mechanism is commented upon qualitatively; however, no qua...

Superfine Fe-V-O Catalyst for Liquid-Phase Oxidation of Toluene to Benzaldehyde

Superfine Fe-V-O Catalyst for Liquid-Phase Oxidation of Toluene to Benzaldehyde

A study on the liquid-phase oxidation of toluene in ionic liquids

The effect and mechanism of the hydrophilic ionic liquids (ILs) with cobalt naphthenate as catalyst on the liquid-phase oxidation of toluene were studied systematically. Five ILs with different hydrophilicities were employed as reaction media. The results showed that toluene conversion increased with increasing hydrophilicity of ILs. The toluene conversion and the corresponding selectivity of benzaldehyde reached 19.6% and 19.5%, respectively, in 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim]BF4). The solubilities of toluene, benzaldehyde, benzyl alcohol and benzoic acid in [Emim]BF4 were further measured at temperatures from 299.2K to 343.2K. The correlations between solubility and temperature were developed based on the critical point of phase separation or ideal solution model. The low solubility of toluene in [Emim]BF4 indicated a heterogeneous oxidation mechanism for toluene. The improvement of toluene conversion and product selectivity in [Emim]BF4 was attributed to the interactions between reaction and extraction separation. The sensitivity study demonstrated that the increase in oxygen pressure was beneficial to the reaction. A much lower reaction temperature of 130°C was achieved in [Emim]BF4 instead of a typical 160–170°C for current commercial plants. The high conversion, low reaction temperature and high product selectivity for the liquid-phase oxidation of toluene in [Emim]BF4 makes it a green and efficient hydrocarbon oxidation process.

Synergetic effect of FeVO4 and α-Fe2O3 in Fe–V–O catalysts for liquid phase oxidation of toluene to benzaldehyde

Synergistic effect of FeVO4 with α-Fe2O3 was found in Fe–V–O catalyst, which was responsible for the high apparent formation rate (A.F.R.) of benzaldehyde in liquid phase oxidation of toluene by hydrogen peroxide. The synergistic effect might create VOx species as active sites; moreover, it improved the reducibility and the reactivity of Fe–V–O catalyst. In order to gain the high A.F.R. of benzaldehyde, the catalyst should have the moderate reducibility.

Mesoporous alumina prepared from waste aluminum cans and used as catalytic support for toluene oxidation

Mesoporous aluminas with high specific surface area were synthesized successfully via a template-free sol–gel method from aluminum isopropoxide (AIP) and aluminum hydroxide produced from waste aluminum cans. After calcinations at 500°C, the synthesized mesoporous aluminas were in gamma phase. The BET surface areas of the mesoporous aluminas obtained from synthesized AIP (427–556m2·g−1) were higher than that prepared from aluminum hydroxide (421m2·g−1). The synthesized alumina products have worm-like pores without long-range ordered framework. Liquid phase oxidation of toluene catalyzed by NiO supported on these mesoporous alumina has been carried out at room temperature.

KINETIC MODELS FOR LIQUID-PHASE CATALYTIC OXIDATION OF TOLUENE TO BENZOIC ACID WITH PURE OXYGEN

The liquid phase oxidation of toluene to benzoic acid by pure oxygen has been performed in a bubble reactor by using cobalt acetate tetrahydrate as catalyst. The influence of the oxygen partial pressures on the reaction kinetics were first investigated, and the results showed that the influence was neglectable in the high oxygen pressure range (>0.5 MPa) under 155°C. Thereby, the reaction rates in the oxidation using pure oxygen are independent of the oxygen partial pressure and expressed as the first order to liquid reactants. Based on a kinetic scheme that involves both benzyl alcohol and benzaldehyde, the kinetic models can well describe the reaction process. Furthermore, the results indicated that the production of benzyl alcohol is much slower than its consumption to form benzaldehyde and the scheme can be further simplified to a kinetic equation, which involves only benzaldehyde as intermediate. The simplified reaction scheme also well describes the reaction, and, thus, the derived kinetic models agree well with the experimental data. The reaction constants follow the Arrhenius law. The estimated activation energies are in the range from 92.63 kJ·mol−1 to 67.81 kJ·mol−1.

Influences of the [Co 2+]/[Co 3+] Ratio on the Process of Liquid-phase Oxidation of Toluene by Air

Liquid phase oxidation of toluene is an environmental benign route for the production of benzoic acid. In a ϕ48 mm bubble column reactor, the commercial process of toluene liquid phase oxidation was conducted with Co(CH 3COO) 2·4H 2O as catalyst. The Co 2+ concentration [Co 2+] was determined by extraction spectrophotometry and hereby the Co 3+ concentration [Co 3+] was obtained by mass balance. The results showed that [Co 3+] reached the maximum at about 25-30 min. [Co 3+] increased with increasing Co catalyst amount at total Co concentration <150 mg·L −1 of toluene. The conversion of toluene, yield and selectivity of benzoic acid increased with the increasing [Co 3+/Co 2+] max. A high [Co 3+] and a high [Co 3+]/[Co 2+] ratio are beneficial to the reaction.

Hydrogen peroxide oxidation of toluene over V/Al systems

A series of γ-alumina supported vanadia catalysts have been prepared by adopting the wet impregnation method. Structural characterization of the catalysts was done by energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) studies, BET surface area analysis, Fourier Transform-infrared spectroscopy (FT-IR) and UV-Vis Diffuse Reflectance spectroscopy (UVDRS). Liquid phase oxidation of toluene has been examined to investigate the catalytic activity. Spectroscopic investigation revealed the presence of highly dispersed tetrahedral vanadyl species at lower loadings and crystalline V2O5 at higher loadings. Incorporation of vanadia leads to greater activity and partial oxidation activity towards the liquid phase oxidation of toluene.

Catalytic Liquid Phase Oxidation of Toluene to Benzoic Acid

AbstractThe production of benzoic acid from toluene in the liquid phase with pure oxygen was studied. Investigations have been carried out with a view to determining the most suitable reaction conditions with respect to operating variables including oxygen flow rate, reaction temperature, batch time and catalyst loading. In a series of batch experiments carried out at 4 atm, the optimum values of mole ratio of oxygen to toluene, temperature, reaction time, and catalyst loading were found to be 2, 157 °C, 2 h and 0.57 g/L, respectively. In addition, a kinetic study was carried out by taking into consideration the optimum reaction conditions. The model dependent on the formation of benzyl radical was found to be feasible for describing the catalytic oxidation of toluene to benzoic acid in the liquid phase. The activation energy was determined as 40 kJ/mol.

Simulation and Optimization in the Process of Toluene Liquid-phase Catalytic Oxidation

Liquid-phase oxidation of toluene with air has become the main technology for producing benzoic acid in a reactor at present. Based on the kinetic model of the toluene oxidation process obtained from laboratory and mass balance of key component, a novel model is established to simulate the industrial toluene oxidation process, in which the effects of benzaldehyde and benzyl alcohol are considered and the kinetic parameters are revised by industrial data. The simulation results show that the error of benzoic acid yield is within 3.5%. Based on the simulation model, to maximize the benzoic acid yield, an optimization model is proposed to optimize the operating parameters, including toluene feed-in mass flux and temperature. The optimization result indicates that on the allowable operating conditions, the maximum benzoic acid yield obtained with the reaction temperature at 167.2°C and the mass flux at 104.1 t·h −1 is greater than the current one, which can be used to guide industrial reactor's operation.

Liquid-phase oxidation of toluene by molecular oxygen over copper manganese oxides

Liquid-phase oxidation of toluene by molecular oxygen over copper manganese oxides

Liquid-phase oxidation of toluene by molecular oxygen over copper manganese oxides

Copper manganese oxides (Cu–Mn oxides) were prepared by coprecipitation method and characterized by several techniques, such as X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and Temperature-programmed reduction (TPR). Catalytic activities of the Cu–Mn oxides were tested by the oxidation of toluene with molecular oxygen in liquid phase and solvent-free conditions. The molar ratio of Cu:Mn in catalyst was optimized to be 1:1 and thus the corresponding crystalline material was designated as Cu1.5Mn1.5O4.

Liquid Phase Oxidation of Toluene to Benzaldehyde with Molecular Oxygen over Copper‐Based Heterogeneous Catalysts

AbstractWe conducted the liquid phase oxidation of toluene with molecular oxygen over heterogeneous catalysts of copper‐based binary metal oxides. Among the copper‐based binary metal oxides, iron‐copper binary oxide (Fe/Cu=0.3 atomic ratio) was found to be the best catalyst. In the presence of pyridine, overoxidation of benzaldehyde to benzoic acid was partially prevented. As a result, highly selective formation of benzaldehyde (86% selectivity) was observed after 2 h of reaction (7% conversion of toluene) at 463 K and 1.0 MPa of oxygen atmosphere in the presence of pyridine. These catalytic performances were similar or better than those in the gas phase oxidation of toluene at reaction temperatures higher than 473 K and under 0.5–2.5 MPa. It was suggested from competitive adsorption measurements that pyridine could reduce the adsorption of benzaldehyde. At a long reaction time of 4 h, the conversion increased to 25% and benzoic acid became the predominant reaction product (72% selectivity) in the absence of pyridine. The yield of benzoic acid was higher than that in the Snia‐Viscosa process, which requires corrosive halogen ions and acidic solvents in the homogeneous reaction media. The catalyst was easily recycled by simple filtration and reusable after washing and drying.

Selective liquid phase oxidation of toluene with air

Catalysis of simple cobalt tetraphenylporphyrin for selective liquid phase oxidation of toluene with air is first reported. By the catalysis of simple cobalt tetraphenylporphyrin, the selective oxidation of toluene with air in the absence of any solvents or promoters will produce benzaldehyde and benzyl alcohol. Compared with the present synthetic method of benzaldehyde and benzyl alcohol by the chlorination of toluene followed by hydrolysis, which has been used in the world industry, the new method has the advantage of friendly environmental effects. The researchers found that the reaction time, temperature, air pressure, the amount of catalyst and the flow rates of air influenced the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol. By the use of 3.2 × 10 −5 M cobalt tetraphenylporphyrin as catalyst, toluene oxidation with air under the optimum conditions of 160 °C and 0.8 MPa and 0.04 m 3/h airflow produced benzaldehyde and benzyl alcohol at 60% selectivity and 8.9% conversion of toluene. The mole turnover numbers of the catalyst was about 25,000. A possible mechanism is also suggested.

Oxidation of aromatic hydrocarbons with hydrogen peroxide over Zn,Cu,Al-layered double hydroxides

Layered double hydroxides (LDHs) with general formula [(Zn 1− y Cu y ) 1− x Al x (OH) 2](NO 3) x · nH 2O ( x≅0.33, 0.6 ≤ y≤1.0, n≅0.5) have been synthesized and characterized by XRD, chemical analysis, and ESR. According to ESR, copper ions exist both as isolated species and as clusters, their relative contribution depending on the overall Cu content. The tendency to form clusters is observed even at a very low absolute Cu concentration. The materials are active in the low temperature liquid phase oxidation of toluene, o-, m-, and p-xylene with hydrogen peroxide. The catalytic reaction involves both the side chain oxidation and the hydroxylation/oxidation of the aromatic ring. The catalytically active centres are formed by isolated copper species. The clustered copper ions are inactive in the oxidation reaction but accelerate the non-productive decomposition of hydrogen peroxide. The catalytic performance is discussed in terms of competition between the process of H 2O 2 decomposition and its consumption in the oxidation reaction.

Effect of manganese substitution on the physicochemical properties and catalytic toluene oxidation activities of Mg–Al layered double hydroxides

A series of Mg–Mn–Al ternary hydrotalcite-like layered double hydroxides (LDHs) with (Mg+Mn)/Al atomic ratios of ∼3 and Mg:Mn atomic ratios ranging from 3:0 to 0:3 were synthesized by a co-precipitation method. The incorporation of Mn in the MgAl-LDH was investigated by employing various techniques, such as powder X-ray diffraction, Fourier transform infrared spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, UV–visible diffuse-reflectance spectroscopy (UV–Vis DRS) and thermogravimetry. A single phase corresponding to LDH was obtained up to the composition Mg:Mn:Al=2.2:0.8:1. A further increase in the Mn content resulted in the formation of a mixture of LDH, Mn(OH) 2 and MnCO 3 phases. Partial oxidation of Mn 2+ to Mn 3+ took place during synthesis, as evidenced by UV–Vis DRS. According to the EPR and UV–Vis DRS results, the Mn 2+/Mn 3+ ions were present in a (distorted) octahedral environment. Calcination at 723 K resulted in the formation of a poorly crystalline MgO-like solid solution. Mn retained its +2 oxidation state (EPR active) even upon calcination at very high temperature (1473 K) in air. At a higher Mn content, in addition to the MgO-like phase, spinel phases such as Mn 3O 4 and MnAl 2O 4 were also obtained at 723 K. The catalytic activity of the as-synthesized samples was tested in the liquid-phase oxidation of toluene using tert-butyl hydroperoxide as the oxidant. Benzaldehyde and benzoic acid were the major products with minor amounts of benzyl alcohol. The compound without an LDH phase was found to be less active for the oxidation of toluene under similar reaction conditions. Solvents were found to have a profound influence on the catalytic activity and the product selectivity.