Phenomenology of oxidation of a cumene feed containing hydroperoxide: I. Two paths of cumene hydroperoxide formation reaction

This article presents direct evidence of the occurrence of cumene oxidation resulting from the presence of gaseous oxygen (O₂^gas) at the gas-liquid interface, demonstrating a markedly higher magnitude of process selectivity, as compared to oxidation that is promoted by dissolved oxygen (₂^liquid). The significant contribution of O₂^gas to the formation of cumene hydroperoxide under bubble-type process conditions is also discussed, emphasizing that the hydroperoxide formation rate is composed of two components: W _total = W ₁^gas + W ₁^liquid, where the first component, W ₁^gas, is a function of k ₁^gas, [O₂^gas], and of the liquid-gas interface area, while the second component, W ₁^liquid, is subject to equation: W = k[R·][O₂^liquid].     

Aerobic oxidation of cumene to cumene hydroperoxide catalyzed by metalloporphyrins

A protocol for the aerobic oxidation of cumene to cumene hydroperoxide (CHP) catalyzed by metalloporphyrins is reported herein. Typically, the reaction was performed in an intermittent mode under an atmospheric pressure of air and below 130°C. Several important reaction parameters, such as the structure and concentration of metalloporphyrin, the air flow rate, and the temperature, were carefully studied. Analysis of the data obtained showed that the reaction was remarkably improved by the addition of metalloporphyrins, in terms of both the yield and formation rate of CHP while high selectivity was maintained. It was discovered that 4 or 5 h was the optimal reaction time when the reaction was catalyzed by monomanganese-porphyrin ((p-Cl)TPPMnCl) (7.20 × 10^?5 mol/l) at 120°C with the air flow rate being 600 ml/min. From the results, we also found that higher concentration of (p-Cl)TPPMnCl, longer reaction time and higher reaction temperature were all detrimental to the production of CHP from cumene. Studies of the reaction kinetics revealed that the activation energy of the reaction (E) is around 38.9 × 10⁴ kJ mol^?1. The low apparent activation energy of the reaction could explain why the rate of cumene oxidation to CHP in the presence of metalloporphyrins was much faster than that of the non-catalyzed oxidation.     

Activation of molecular oxygen in trifluoroacetic acid

The possibility of the formation of the H₂O₂^+· cation-radical was determined according to the data from nonempirical calculations for liquid trifluoroacetic acid, which forms a hydroperoxide radical after deprotonation. A catalytic cycle was obtained in which CF₃COOH serves as a catalyst in the oxidation of a substrate by dissolved molecular oxygen.     

Liquid-phase oxidation of isopropyl-meta-xylene to tertiary hydroperoxide

Fundamental aspects and the mechanism of the reaction of liquid-phase oxidation of isopropyl-meta-xylene to a tertiary hydroperoxide by atmospheric oxygen, initiated by isopropylbenzene hydroperoxide or catalyzed by N-hydroxyphthalimide were studied. It was found that using N-hydroxyphthalimide in the course of oxidation of isopropyl-meta-xylene makes it possible to raise, compared with the initiator (isopropylbenzene hydroperoxide), the oxidation rate and the conversion of the hydrocarbon by a factor of 2–2.5 at a 90–95% formation selectivity of a tertiary hydroperoxide of isopropyl-meta-xylene up to a conversion of 20–25%.     

Polymer supported catalyst for the effective autoxidation of cumene to cumene hydroperoxide

The autoxidation of cumene to cumene hydroperoxide (CHP) in the presence of catalyst which was prepared by adsorbing copper(II) acetate onto polymer support, was investigated. When a styrene-divinylbenzene copolymer with sulfonic acid functional groups was used as a support, the resulting catalyst had no catalytic activity. When a macroreticular acrylic polymer containing carboxylic acid exchange groups was used as a support, an effective catalyst was obtained. In the presence of this catalyst (0.2 g Cu(OAc)₂-BR-0.6 per 10 mL of cumene) at 353 K, the steady autoxidation rate is 84% faster than that initiated with CHP; the selectivity is 99% at 6.8% conversion. The catalyst is stable at 383 K. Furthermore, the catalyzed cumene autoxidation rate increases linearly with copper acetate loading as well as the amount of catalyst. But when the steady autoxidation rate increases, the selectivity to cumene hydroperoxide reduces, but is still satisfactory. Hence, it is possible to speed up the cumene autoxidation rate by raising the reaction temperature, using catalysts with high metal loading and using more catalyst.     

Thermal runaway reaction evaluation of two by-products mixed with cumene hydroperoxide in the oxidation tower

Oxygen (O₂) or air is widely used to produce cumene hydroperoxide (CHP) in the cumene oxidation tower. The aim of this study was applied to analyze thermal hazard of two by-products including alpha-methylstyrene (AMS) and acetophenone (AP) in a CHP oxidation tower. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were operated to evaluate thermal runaway reaction of CHP mixed with AMS and AP. Exothermic onset temperature (T ₀), maximum temperature (T _max), activation energy (E _a), etc., that were employed to prevent and protect thermal runaway reaction and explosion in the manufacturing process and storage area. In view of proactive loss prevention, the inherently safer handling procedure and storage situation should be maintained in the chemical industries. The T ₀ of 30 mass% CHP was determined to be 105 °C by DSC. Therefore, the T ₀ of 30 mass% CHP mixed with AMS was determined to be 60–70 °C by DSC. The exothermic reaction of CHP/AP and CHP/AMS by DSC under N₂ reaction gas is thermal decomposition of oxygen–oxygen bond (–O–O–) because of the anaerobic reaction.     

Reaction of zirconium alkoxides with tert-butyl hydroperoxide. Oxidative ability of the Zr(OBu-t)4-t-BuOOH system

Oxidation of the isopropoxy group in the Zr(i-PrO)₄·i-PrOH complex involves both direct reaction with tert-butyl hydroperoxide and intermediate formation of zirconium peroxy compound. Zirconium tetra-tert-butoxide reacts with tert-bytyl hydroperoxide to form metal-containing peroxide and trioxide. Decomposition of the latter leads to oxygen evolution and is accompanied by radical formation. The alkoxyl and peroxyl radicals formed were identified by ESR spectroscopy. The nature of the oxidant (oxygen, zirconium-containing peroxide and-trioxide) in the Zr(OBu-t)₄-t-BuOOH system is determined by the structure of the substrate molecule.     

Kinetics of catalyst-free thermal and photo-oxidation of cumene

Kinetics of thermal and photo-oxidation of cumene in the absence of catalyst was studied using high-pressure differential scanning calorimetry and low-pressure photocalorimetry. Kinetics of oxidation was followed by cumene hydroperoxide (CHP), acetophenone, and phenol formation. The amount of CHP formed was deduced from the total heat of reaction of thermal degradation of CHP at 453 K and using a new gas chromatographic method. CHP solution in cumene oxidized at 453 K and 680 psi of oxygen reproducibly with the heat of reaction linearly dependent on peroxide concentration in cumene. It was confirmed that cumene thermal oxidation was slow at <453 K, but at ≥453 K could occur explosively. Autocatalysis by CHP during thermo-oxidation was confirmed. Apparent activation energy of the photo-oxidation of cumene was found to be E _a = 22.3 kJ mol^?1. The value corresponds to radical chain process of the cumene autoxidation. Under assumption of pseudo-first order reaction, the rate constant of CHP formation was found to change from k _CHP ≈ 0.76 s^?1 during the first 4 h of photo-oxidation to k _CHP ≈ 0.2 s^?1 at the later stages at 2.0 W cm^?2 of UV exposure dose. It was established that the initial presence of the CHP in cumene does not change the photo-oxidation kinetics, but shifts the kinetic curve to earlier time. Finite difference method was employed to numerically model kinetics of cumene oxidation. The result indicated higher than expected thermal and photo-stability of both, cumene and CHP.     

Reactivity of fullerene C60 towards peroxy radicals generated by liquid-phase oxidation of cumene and ethylbenzene with oxygen

The inhibiting action of fullerene C₆₀ on the liquid-phase initiated oxidation of cumene and ethylbenzene was studied. The apparent rate constants of inhibition by fullerene C₆₀ of cumene and ethylbenzene oxidation were determined by measuring the amount of absorbed oxygen: (1.3±0.2)·10³ and (2.0±0.3)·10³ L mol^?1 s^?1, respectively.     

The initiation properties of 2-cyano-2-propyl hydroperoxide in oxidation processes

The initiating ability of 2-cyano-2-propyl hydroperoxide in the oxidation reaction of cumene by molecular oxygen has been investigated and compared with the initiating ability of cumene hydroperoxide.

---

Die Initiierungseigenschaften von 2-Cyano-2-propyl-hydroperoxid bei Oxydations-prozessen

Zusammenfassung Es wurde die Initiierungsfähigkeit des 2-Cyan-2-hydroperoxypropans in der Oxidation von Cumol mit molekularem Sauerstoff untersucht und mit der Initiierungsfähigkeit des Cumolhydroperoxids verglichen.

     

Liquid-phase oxidation of benzothiophene and dibenzothiophene by cumyl hydroperoxide in the presence of catalysts based on supported metal oxides

The liquid-phase oxidation of benzothiophene and dibenzothiophene by cumyl hydroperoxide in the presence of supported metal oxide catalysts was carried out in octane in an N₂ atmosphere at 50–80°C. The cumyl hydroperoxide, benzothiophene, and dibenzothiophene conversions and the yield of sulfones were determined for catalysts of various natures. In the presence of MoO₃/SiO₂, the most efficient and most readily regenerable catalyst, the benzothiophene conversion was ～60% and the dibenzothiophene conversion was as high as 100% upon almost complete consumption of cumyl hydroperoxide. The influence of unsaturated and aromatic compounds (oct-1-ene, toluene) on the catalytic effect was studied. The kinetics of substrate oxidation and cumyl hydroperoxide decomposition and an analysis of the cumyl hydroperoxide conversion products suggested a benzothiophene and dibenzothiophene oxidation mechanism including the formation of an intermediate complex of the hydroperoxide with the catalyst and the substrate and its transformation via heterolytic and homolytic routes.     

Decomposition of cumene hydroperoxide in the systems of normal and reverse micelles formed by cationic surfactants

Decomposition of cumene hydroperoxide into free radicals in aqueous and organic media in the presence of cationic surfactants at 37°C is studied by the method of inhibitors using quercetin as an acceptor of radicals. It is found that cationic surfactants catalyze the decomposition of cumene hydroperoxide into radicals, the catalytic effect in an organic medium being higher than that in an aqueous solution. Catalytic action of surfactants greatly depends on the counterion nature. Cetyltrimethylammonium chloride has the highest catalytic activity. Characteristics of surface activity of some cationic surfactants and hydroperoxides are obtained.     

WO3/MO2 (M = Zr, Sn, Ti) heterogeneous acid catalysts: Synthesis, study, and use in cumene hydroperoxide decomposition

Thirty (5–40)% WO₃/MO₂ (M = Zr, Ti, Sn), heterogeneous acidic catalysts have been synthesized by two methods, specifically, via homogeneous acid solutions and from solutions brought to pH 9 with ammonia, both followed by calcination at 600–900°C. The catalysts have been characterized by IR spectroscopy and scanning electron microscopy, and their aqueous washings have been analyzed. Their acidity has been determined by the thermal analysis of samples containing adsorbed pyridine, and in terms of the proton affinity scale. Catalytic activities have been compared for cumene hydroperoxide (CHP) decomposition at 40°C in cumene and acetone. For all M, the catalysts are one type and contain W in strongly and weakly bound states, the latter being a polyoxometalate that can be washed off. Both tungstate phases are active in acid catalysis. Brønsted acid sites with a broad strength distribution have been found. The strongest of them are heteropolyacid protons. The catalysts 30% WO₃/SnO₂ and 20% WO₃/ZrO₂ (in acetone) and 10–20% WO₃/TiO₂ (in cumene) are the most active in CHP decomposition, and their activity is not related to their total acidity. Phases containing W⁶⁺ that form during the high-temperature synthesis are responsible for the high acidity, and additional protons that may appear owing to W⁶⁺ reduction can play only a minor role.     

Molecular structure, barriers to internal rotation, and the enthalpy of formation of cumene hydroperoxide PhCMe2OOH: a DFT study

Conformational analysis of cumene hydroperoxide PhCMe₂OOH (1) has been carried out using the density functional methods B3LYP/6-31G(d,p) and B3LYP/6-311+G(3df,2p). Ignoring rotation of methyl groups, molecule 1 has seven conformers differing in orientation of the — CMe₂OOH fragment relative to the benzene ring and in mutual position of atoms in this fragment. The molecular structures, relative energies, and statistical distribution of the conformers were determined, and intramolecular rotational barriers were estimated. The enthalpies of formation of all conformers of molecule 1 were calculated using two approximations with inclusion of zero-point vibrational energy and temperature correction. Calculations using the isodesmic reaction (IDR) scheme made it possible to reduce the systematic error of the determination of the enthalpy of reactions. The total enthalpy of formation of compound 1 calculated with inclusion of statistical distribution of rotamers equals −19.7±3.6 kcal mol⁻¹. The combination of the B3LYP/6-31G(d,p) approximation and the IDR scheme gives fairly accurate results (relative error is ±0.4 kcal mol⁻¹) as compared to those obtained with the extended basis set 6-311+G(3df,2p). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1157–1164, June, 2008.     

Kinetics of the reactions of 2,4,6-tri-t-butylphenoxyl with cumene hydroperoxide,cumylperoxyl radicals,and molecular oxygen

Reactions of 2,4,6-tri-t-butylphenoxyl (TBP) with cumene hydroperoxide (ROOH), cumylperoxyl radicals (RO₂), and molecular oxygen in benzene solution have been investigated kinetically by the ESR method. The rate constant of the reaction TBP + ROOH has been estimated in the temperature range 27°-75°C: log₁₀(k_?7/M^?1sec^?1) = (7.1 ± 0.4) - (10.9 ± 0.6 kcal mole^?1)/θ The ratio of the rate constants of reactions TBPH + RO₂ products has been determined from the experimental dependence of the rate constant of reaction TBP with ROOH on [TBPH]₀/[TBP]₀. Putting k₇ = 4.0 × 10³M^?1sec^?1, we obtain k₈ = (2.0 ± 0.2) × 10⁸M^?1sec^?1 at 30°C. The reaction of TBP with O₂ obeys the kinetic law ?d[TBP]/dt = k′[O₂][TBP]². This is in accordance with scheme TBP + O₂ ← TBP ?O₂ [I]; TBP ?O₂ + TBP · products, log₁₀ (k′/M^?2sec^?1) = (?14.5 ± 0.9) + (27.2 ± 1.4)/θ at 66°?78°C, where ° = 2.303RT.     

Catalytic conversion of benzene to phenol

Phenol is very useful intermediate in the manufacture of petrochemicals, drugs, agrochemicals, and plastics. Commercially, phenol is produced by a three-step, high-energy consumption process known as the cumene process. The conversion of a chemical to a value-added product is always economically desirable. More than 90% of phenol consumption in the world is manufactured by the multistep cumene process, in which acetone is coproduced in 1: 1 molar ratio with respect to phenol. However, the drawbacks of the three-step cumene process have spurred the development of more economical routes to decrease energy consumption, avoid the formation of explosive cumene hydroperoxide, and increase the yield. The objective of this article is to highlight benzene-to-phenol conversion technologies with emphasis on direct conversion methods. Gas phase and liquid phase reactions are the two main routes for direct oxidation of benzene to phenol. Indirect methods, such as the cumene process, and direct methods of benzene-to-phenol conversion are discussed in detail. Also discussed is the single-step reaction of benzene to phenol using oxidants such as O₂, N₂O, and H₂O₂. Catalytic conversion of benzene to value-added phenol using a chemically converted graphene-based catalyst, a cost-effective carbon material, is discussed.     

Preparation and catalysis of chloromethylated polystyrene‐supported macrocyclic Schiff base metal complexes for the oxidation of cumene

Chloromethylated polystyrene‐supported macrocyclic Schiff base metal complexes (PS‐L‐M, M = Cu²⁺, Co²⁺, Ni²⁺, and Mn²⁺) were synthesized and characterized by the methods of IR, ICP, and small area X‐ray photoelectron spectroscopy (XPS). The oxidation of cumene by molecular oxygen in the absence of solvent with the synthesized complexes employed as catalyst was carried out. In comparison with their catalytic activities, PS‐L‐Cu is a more effective catalyst for the oxidation of cumene. The main products are 2‐phenyl‐2‐propanol (PP) and cumene hydroperoxide, which were measured by GC/MS. The influences of reaction temperature, the amount of catalyst, as well as the reaction time on the oxidation of cumene were investigated. Copyright © 2008 John Wiley & Sons, Ltd.     

Photostabilizing activity of sterically hindered piperidines—II: Radical trapping ability

The abilities of both 2,2,6,6-tetramethylpiperidine (I) and its nitroxyl (II) to trap radicals involved in hydrocarbon photo-oxidations have been studied in cumene and 1,3,5-trimethylcyclohexane at 27° using AIBN, hydroperoxide and dialkylperoxide as initiators: the light was either the band 300–400 nm or 366 nm. Under conditions of photolysis of ROOH (degenerate branching), I is oxidized to II. II is capable of trapping R' radicals, the rate constant being ～50 times lower than that for RO^.₂ formation. RO^.₂ radicals react with neither I nor II. Under the condition of degenerate branching, II is capable of intercepting the radical fragments from decomposing hydroperoxide. The rate constant of this process is ～500 times higher than that for hydrogen abstraction by these fragments. A reaction mechanism is suggested: hydrogen bonded associates formed between an N-containing stabilizer and ROOH play a dominant role. The principal intermediates in this mechanism are represented by >NO^., >NOH and >NOR species.     

The antioxidant activity of phosphorus compounds—Part I: Decomposition of hydroperoxides by pentaerythritol diphosphites

A series of pentaerythritol diphosphites (PEDP) was used to study the effect of structure on the decomposition of 1-methyl-1-phenylethyl hydroperoxide (cumene hydroperoxide, CHP) in chlorobenzene under nitrogen at 75°C. Whilst pentaerythritol diphosphites with bonds:

react in a strictly stoichiometric reaction with cumene hydroperoxide, forming phosphates, we propose that pentaerythritol diphosphites and thiophosphates with bonds:

react with cumene hydroperoxide by a different mechanism. The active heteroatom is sulphur which, through the formation of a catalytically active species, causes rapid decomposition of the hydroperoxide which is studied by measuring infra-red spectra using FTIR techniques.     

Mechanism and kinetics of the production of hydroxymethyl hydroperoxide in ethene/ozone/water gas-phase system

The mechanism and kinetics of the production of hydroxymethyl hydroperoxide (HMHP) in ethene/ ozone/water gas-phase system were investigated at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The reactants were monitored in situ by long path FTIR spectroscopy. Peroxides were measured by an HPLC post-column fluorescence technique after sampling with a cold trap. The rate constants (k3) of reaction CH2O2 H2O→HMHP (R3) determined by fitting model calculations to ex-perimental data range from (1.6―6.0)×10?17 cm3·molecule?1·s?1. Moreover, a theoretical study of reac-tion (R3) was performed using density functional theory at QCISD(T)/6-311 (2d,2p)//B3LYP/6-311 G(2d, 2p) level of theory. Based on the calculation of the reaction potential energy surface and intrinsic reac-tion coordinates, the classic transitional state theory (TST) derived k3 (kTST), canonical variational tran-sition state theory (CVT) derived k3 (kCVT), and the corrected kCVT with small-curvature tunneling (kCVT/SCT) were calculated using Polyrate Version 8.02 program to be 2.47×10-17, 2.47×10-17 and 5.22×10-17 cm3·molecule-1·s-1, respectively, generally in agreement with those fitted by the model.