Liquid-phase Catalytic Oxidation Research Articles

Multi-objective optimization of p -xylene oxidation process using an improved self-adaptive differential evolution algorithm

Abstract The rise in the use of global polyester fiber contributed to strong demand of the Terephthalic acid (TPA). The liquid-phase catalytic oxidation of p -xylene (PX) to TPA is regarded as a critical and efficient chemical process in industry [1] . PX oxidation reaction involves many complex side reactions, among which acetic acid combustion and PX combustion are the most important. As the target product of this oxidation process, the quality and yield of TPA are of great concern. However, the improvement of the qualified product yield can bring about the high energy consumption, which means that the economic objectives of this process cannot be achieved simultaneously because the two objectives are in conflict with each other. In this paper, an improved self-adaptive multi-objective differential evolution algorithm was proposed to handle the multi-objective optimization problems. The immune concept is introduced to the self-adaptive multi-objective differential evolution algorithm (SADE) to strengthen the local search ability and optimization accuracy. The proposed algorithm is successfully tested on several benchmark test problems, and the performance measures such as convergence and divergence metrics are calculated. Subsequently, the multi-objective optimization of an industrial PX oxidation process is carried out using the proposed immune self-adaptive multi-objective differential evolution algorithm (ISADE). Optimization results indicate that application of ISADE can greatly improve the yield of TPA with low combustion loss without degenerating TA quality.

Production of Flat Ceramic Membrane Contactors with a Catalytically Active Layer Based on Co3O4

Flat membrane contactors comprising ceramic disk microfiltration membranes with a deposited layer of Co3O4 are obtained. The characteristics, such as the thickness of the layer and the pore-size distribution, are determined and the specific surface of the substrate and the deposited layer of Co3O4 are determined. It is shown that the membrane contactors obtained are suitable for liquid-phase catalytic oxidation of phenols under soft conditions, including in waste waters.

Role of alkali in catalytic oxidation of p-cresols

The investigation of alkali acting as the key component during the liquid-phase catalytic oxidation of p-cresols to p-hydroxyl aromatic aldehydes is far from satisfied, thus a detailed exploration is presented. It was observed that the p-cresols were activated by alkali to form phenolate salt to ensure mild reaction conditions demonstrated by comparing the oxidation of p-cresol and its phenolate sodium. It was also found that excess alkali improved the selectivity of aldehyde by inhibiting the formation of dimeric side products in view of an analysis of the side products distribution. The alkaline alcoholic anion facilitates the 1,6-addition reaction between p-benzoquinone methide and solvent. Thus, more alkali was needed in solvents with high pKa values and high water content. The detection of trace acid during the oxidation of p-cresols suggested the phenoxy radical mechanism rather than the classic benzyl radical mechanism proposed for interpreting the oxidation of non-hydroxyl aromatic hydrocarbons. These conclusions contribute significantly to both the understanding of role of alkali during the reaction process and the mechanism study for the catalytic oxidation of cresols and non-hydroxyl aromatic hydrocarbons.

The effect of surface oxygenated groups of carbon nanotubes on liquid phase catalytic oxidation of cumene

Surface oxygenated groups, instead of surface defects, play a negative role in the liquid phase radical oxidation reaction catalyzed by carbons.

Solvent inhibition in the liquid-phase catalytic oxidation of 1,4-butanediol: understanding the catalyst behaviour from NMR relaxation time measurements

Solvent inhibition over surfaces affects behaviour and performances of heterogeneous catalysts.

Catalytic liquid-phase oxidation of acetaldehyde to acetic acid over a Pt/CeO2–ZrO2–SnO2/γ-alumina catalyst

Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2–ZrO2–SnO2 were successfully dispersed on the γ-Al2O3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4wt.%)/Ce0.68Zr0.17Sn0.15O2.0(16wt.%)/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4hr and longer.

Catalytic liquid phase oxidation of 1,4-dioxane over a Pt/CeO2-ZrO2-Bi2O3/SBA-16 catalyst

A Pt/CeO2-ZrO2-Bi2O3/SBA-16 (Santa Barbara Amorphous No. 16) catalyst was prepared by hydrothermal and wet impregnation methods for catalytic purification of 1,4-dioxane in water. SBA-16 has a number of mesopores and the average size of the pores is 9.4 nm. In the present catalyst, platinum and CeO2-ZrO2-Bi2O3 were successfully dispersed in the pores of the SBA-16 support, and the temperature dependence of the liquid phase oxidation of 1,4-dioxane was examined. The oxidation reaction proceeded effectively in the air atmosphere in the temperature range of 40–80 °C.

Performance of cobalt titanate towards H2O2 based catalytic oxidation of lignin model compound

Mixed metal cobalt titanium oxide (CoTiO3) prepared by solution phase method has been evaluated for the liquid phase catalytic oxidation of vanillyl alcohol to vanillin using H2O2 as an oxygen source.

Liquid-Phase Catalytic Oxidation of Styrene by a Fiber-Supported Copper(II) Complex with High Catalytic Performance

A new type of polymer-supported catalyst, [PS-(PBIM)2Cu (II)], was synthesized by loading 2-(2’-pyridyl) benzimidazole on chloromethylated propylene-styrene graft copolymer fiber and subsequent treatment with Cu (OAc)2 in methanol. The prepared catalyst was used in the oxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant. The important reaction conditions, such as the reaction temperature, the ratio of oxidant/styrene, and the recycle times were examined. The experimental results show that the catalyst reveals relatively high catalytic performance with 84% conversion for styrene. The suitable conditions are as follows: n (styrene):n (TBHP)=1:3, the reaction temperature of 80 °C and the reaction time of 8 h. In addition, the catalyst used repeatedly for 3 times can still possess high catalytic activity.

The Basic Investigation on Catalytic Oxidation of Mine Gas to Methanol in Liquid Phase

A set of experimental system was self-designed and made for liquid phase catalytic oxidation of gas to methanol. It was used to investigate the impacts of catalyst and reaction conditions on catalytic oxidation of gas to methanol in acetic acid solution, and to analyze its reaction mechanism. It has been showed that the yield of the methanol is 1840 μmol under the catalysis of 0.5 g of 0.5% Pd-CuPc/Y and the following conditions: CH3COOH:H2O = 4:1 (v/v), 1000 μmol of p-benzoquinone; reaction time, 3 h; reaction temperature, 150°C; gas composition, 2.5MPa CH4+0.4MPaO2 +0.4MPa N2; in acetic acid solution, catalytic oxidation of mine gas to methanol follows mechanisms of electrophilic substitution and oxidation of reactive oxygen species (ROS).

Dynamics of liquid-phase catalytic oxidation of hydrogen sulfide removal in rural biogas

Hydrogen sulfide in rural biogas was removed with liquid-phase catalytic oxidation. By using rare earth as catalyst, and sulfosalicylic acid as stabilizer, H2S purification efficiency could increase as high as 96%, and sulfur capacity of the composite solution was about 3 g/L. The results show that purification efficiency was affected by catalyst addition, pH, experimental temperature, and sulfur capacity. The parameters effects on catalytic oxidation were studied, and the optimized conditions were that Fe3+ concentration 0.08 mg/L, reaction temperature 70°C, pH 9.0, with a absorption solution volume of 50 mL, a gas flow rate 200 mL/min, and H2S mass concentration of 1.58–2.02 mg/m3.

Selective oxidization of 2- and 3-aminotoluene by ozone in the glacial acetic acid to the corresponding aminobenzoic acids

The kinetic regularities and mechanisms of oxidation reactions of 2- and 3-aminotoluene and its acylation derivatives by the gases that contain ozone in the glacial acetic acid have been studied. It has been established that ozone attacks mainly the lone pair of electrons of the nitrogen atom with formation, mainly, of polymers of azo compounds. The products oxidation on methyl group are not formed in these conditions. The direction of the ozone’s attack can be altered and directed on the methyl group, as well as by an aromatic ring, by acylation of the amino group. The total yield of the products of oxidation of the methyl group of 2- and 3-acetamidotoluene is 5,1 and 12,4 % respectively. The process of liquid-phase catalytic oxidation of 2- and 3-acetamidotoluene by the ozone in the presence of transition metal salts and their mixtures with potassium bromide to the corresponding acetamidobenzoic acids has been investigated as well. At the presence of acetate Co (II) the output of 2- and 3-acetamidobenzoic acid 25,0 and 31,2% respectively. We found out that the use of our catalytic system (ozone – acetamidotoluene - Co (III) – glacial acetic acid - potassium bromide) significantly increases the reaction rate and the selectivity of sub­strate oxidation of methyl groups. The main product of oxidation of 2- and 3-acetamidotoluene becomes 2- and 3-acetamidobenzoic acid (55,0 and 71,2 % respectively). Replacing ozone-air mixture with the ozone-oxygen mixture leads to higher yield of 2-acetamidobenzoic acid 70,0 % and 3- acetamidobenzoic acid 86,0 %.

Effects of Oxygen Transfer Limitation and Kinetic Control on Biomimetic Catalytic Oxidation of Toluene

Under oxygen transfer limitation and kinetic control, liquid-phase catalytic oxidation of toluene over metalloporphyrin was studied. An improved technique of measuring dissolved oxygen levels for gas-liquid reaction at the elevated temperature and pressure was used to take the sequential data in the oxidation of toluene catalyzed by metalloporphyrin. By this technique the corresponding control step of toluene oxidation could be obtained by varying reaction conditions. When the partial pressure of oxygen in the feed is lower than or equal to 0.070 MPa at 463 K, the oxidation of toluene would be controlled by oxygen transfer, otherwise the reaction would be controlled by kinetics. The effects of both oxygen transfer and kinetic control on the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol in biomimetic catalytic oxidation of toluene were systematically investigated. Three conclusions have been made from the experimental results. Firstly, under the oxygen transfer limitation the toluene conversion is lower than that under kinetic control at the same oxidation conditions. Secondly, under the oxygen transfer limitation the total selectivity of benzaldehyde and benzyl alcohol is lower than that under kinetic control with the same conversion of toluene. Finally, under the kinetics control the oxidation rate of toluene is zero-order with respect to oxygen. The experimental results are identical with the biomimetic catalytic mechanism of toluene oxidation over metalloporphyrins.

Influencing factors for catalytic oxidation of mine gas to methanol in liquid phase

The influencing factors for liquid phase catalytic oxidation of mine gas to methanol (in form of CH3COOCH3) are studied using the self-established experimental apparatus. The results show that CH3COOCH3 (target product) is obtained by using CH3COOH as reaction solvent, and the yield of target product increases with the increasing of reaction temperature, gas pressure and reaction time. In the mine gas-Pd(OAc)2-CH3COOH system, the yield of CH3COOCH3 increases with the increasing of addition of Pd(OAc)2 which is redox catalyst for mine gas conversion. The yield of CH3COOCH3 will be greatly improved by composite additional oxidant which is obtained by equimolar mix of p-benzoquinone with NO2.

Preparation, Characterization and Catalytic Activity of Highly Dispersed Gold Catalyst

Highly dispersed supported gold catalysts have been prepared by solution reduction method using L-lysine as protection agents, and their catalytic activity was evaluated by the liquid phase catalytic oxidation reaction of glucose to gluconic acid. The results suggested that the Au/ZrO2 catalyst, exhibited high activity for the selective oxidation of glucose. At the reaction temperature of 323K, reaction time of 1h, with the NaCO3-NaHCO3 as buffer solution, the yield of gluconic acid was 100%.

Preparation of Benzaldehyde by Liquid-Phase Catalytic Oxidation of Methyl Benzene

Preparation of Benzaldehyde by Liquid-Phase Catalytic Oxidation of Methyl Benzene

Continuous gas–liquid aerobic oxidation of toluene catalyzed by [T(p-Cl)PPFe]2O in a series of three stirred tank reactors

The liquid-phase catalytic aerobic oxidation of toluene by [T(p-Cl)PPFe]2O was studied in a series of three stirred tank reactors. The effects of operation mode (including semi-batch and continuous operation), reaction temperature, catalyst concentration, average residence time, and air flow rate on the oxidation process were examined. The experimental results showed that continuous oxidation had no advantage over the total yield and selectivity of benzaldehyde and benzyl alcohol in comparison with semi-batch oxidation. And the reaction temperature was the most significant factor influencing on continuous oxidation of toluene. It is also found that adopting sequentially decreased temperature in the three series reactors could improve the yield and selectivity of benzaldehyde and benzyl alcohol in this process. Under which at the higher conversion of toluene, the total yield to benzaldehyde and benzyl alcohol increased 17.05% or 43.62% respectively in comparison with adopting sequentially increased or same temperature in the three series reactors.

Liquid-phase catalytic oxidation of p-chlorotoluene to p-chlorobenzaldehyde over manganese oxide octahedral molecular sieves

Manganese oxide octahedral molecular sieves (OMS-2) show much higher catalytic activities in the liquid-phase catalytic oxidation of p-chlorotoluene than MnO2, Mn3O4, Mn(OAc)2 as well as than some other transition metal oxides such as Co2O3, V2O5 and Fe2O3. Based on temperature-programmed desorption and thermogravimetric results, it is deduced that the catalytic activity of OMS-2 can be ascribed to the abundance and mobility of lattice oxygen. We investigated the effects of reaction temperature, reaction time, catalyst amount, and initial water amount on the reaction. Under optimal reaction conditions, p-chlorotoluene conversion and p-chlorobenzaldehyde selectivity are respectively 86.0% and 68.7%. The catalysts can be easily recovered by centrifugation, and reused. According to the results of X-ray diffraction and N2 adsorption/desorption analyses, there is no significant change in major characteristics of the catalyst after 4 cycles of reaction.

Liquid-phase catalytic oxidation of p-acyl-substituted toluenes with oxygen

A method based on the liquid-phase oxidation of p-acyl-substituted toluenes has been developed for the synthesis of p-acyl-substituted benzoic acids. It is possible s to recycle the unreacted substrate in this process and to isolate terephthalic acid, which is the second reaction product. A formal kinetic scheme is suggested for the process, which indicates that the reaction products form successively.

Liquid-phase catalytic oxidation of organic substrates by a recyclable polymer-supported copper(II) complex

Chloromethylated polystyrene beads cross-linked with 6.5 % divinylbenzene were functionalized with 2-(2′-pyridyl) benzimidazole (PBIMH) and on subsequent treatment with Cu(OAc)2 in methanol gave a polymer-supported diacetatobis(2-pyridylbenzimidazole)copper(II) complex [PS-(PBIM)2Cu(II)], which was characterized by physicochemical techniques. The supported complex showed excellent catalytic activity toward the oxidation of industrially important organic compounds such as phenol, benzyl alcohol, cyclohexanol, styrene, and ethylbenzene. An effective catalytic protocol was developed by varying reaction parameters such as the catalyst and substrate concentrations, reaction time, temperature, and substrate-to-oxidant ratio to obtain maximum selectivity with high yields of products. Possible reaction mechanisms were worked out. The catalyst could be recycled five times without any metal leaching or much loss in activity. This catalyst is truly heterogeneous and allows for easy work up, as well as recyclability and excellent product yields under mild conditions.