Liquid-phase Oxidation Reactions Research Articles

Effect of Ag Addition to Au Catalysts for the Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid

AbstractThe addition of Ag to Au nanocatalysts is known to improve several catalytic reduction and oxidation reactions. Until now, bimetallic AuAg catalysts have not been studied in detail in liquid phase oxidation reactions. We investigated the activity, selectivity, and stability of silica supported Au, Ag and AuAg catalysts in the oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐furandicarboxylic acid (FDCA), an important reaction to produce bio‐based polymers. We demonstrate that addition of an optimum amount of inactive Ag to the active Au catalyst substantially increases the overall selectivity and yield of the desired FDCA. Interestingly, Ag addition decreased the conversion rate of the reactant HMF to the intermediate HMFCA, but improved (up to 10–20 % Ag addition) much the conversion of the intermediate product to the desired final product. This is probably due to tuning the electronic properties of the nanoparticles to achieve an optimum adsorption strength of the intermediate on the surface of AuAg catalysts. Moreover, particle growth was suppressed by the bimetallic AuAg catalyst, ultimately leading to superior stability compared to its monometallic counterparts.

Pollution characteristics and transformation mechanisms of secondary inorganic components during winter heavy pollution in Handan city in 2018–2020

The mechanism of secondary transformation of nitrate and sulfate under different relative humidity (RH), and different atmospheric oxidizing conditions is still controversial. This study focuses on the winter heavy pollution process in Handan city from 2018 to 2020, and the following results were obtained: The average concentration of PM2.5 showed a decreasing trend from year to year, but the SNA (SO42−, NO3− and NH4+) showed an increasing trend from year to year, and the concentration of nitrate exceeded that of sulfate. During the haze formation period from 2018 to 2020, a significant disparity was observed in NO2 and SO2 emissions, with NO2 emissions surpassing those of SO2. Mobile sources were found to contribute more emissions than fixed sources, particularly during the haze persistence period (HP). However, sulfate conversion outweighed nitrate conversion. HighRH and photochemical reactions induced by ozone favored the formation of nitrate and sulfate, which formated heavy haze. When 40% ≤ RH ≤ 70%, atmospheric oxidants (Ox = O3 + NO2) concentration was the highest, nitrogen oxidation ratio (NOR) and sulfur oxidation ratio (SOR) increased rapidly, and nitrate was mainly generated by photochemical reactions during daytime. When RH > 70% and the concentration of Ox was low, RH will weaken the photochemical intensity. Therefore, the liquid-phase oxidation reaction of N2O5 contributed significantly to atmospheric nitrate at night, and the liquid-phase oxidation reaction of sulfate was faster than the gas-phase one. Local emissions contributed significantly to particulate matter pollution during heavy pollution in 2018–2020, and the main sources were secondary conversion, coal combustion, biomass burning, and road dust.

Preparation of cobalt catalyst supported on perovskite-type oxide and application in liquid-phase selective oxidation reaction

Abstract Cobalt catalyst supported on the perovskite-type oxide sodium tantalate, NaTaO3 (NTO) was prepared by using the hydrothermal method and used in liquid-phase p-xylene oxidation, which led to p-methyl benzyl alcohol, p-tolualdehyde, and p-toluic acid. Investigation showed that the formation of alcohol and aldehyde was a competitive reaction. Further oxidation of the alcohol did not occur. On the other hand, the oxidation of p-tolualdehyde led to the formation of acid. Co-NTO catalyst showed higher selectivity toward the route of p-tolualdehyde than the p-methylbenzyl alcohol compared with the bulk Co3O4.

Catalysts Based on Iron Oxides for Wastewater Purification from Phenolic Compounds: Synthesis, Physicochemical Analysis, Determination of Catalytic Activity

In this work, the synthesis of magnetite nanoparticles and catalysts based on it stabilized with silicon and aluminum oxides was carried out. It is revealed that the stabilization of the magnetite surface by using aluminum and silicon oxides leads to a decrease in the size of magnetite nanocrystals in nanocomposites (particle diameter less than ~10 nm). The catalytic activity of the obtained catalysts was evaluated during the oxidation reaction of phenol, pyrocatechin and cresol with oxygen. It is well known that phenolic compounds are among the most dangerous water pollutants. The effect of phenol concentration and the effect of temperature (303–333 K) on the rate of oxidation of phenol to Fe3O4/SiO2 has been studied. It has been determined that the dependence of the oxidation rate of phenol on the initial concentration of phenol in solution is described by a first-order equation. At temperatures of 303–313 K, incomplete absorption of the calculated amount of oxygen is observed, and the analysis data indicate the non-selective oxidation of phenol. Intermediate products, such as catechin, hydroquinone, formic acid, oxidation products, were found. The results of UV and IR spectroscopy showed that catalysts based on magnetite Fe3O4 are effective in the oxidation of phenol with oxygen. In the UV spectrum of the product in the wavelength range 190–1100 nm, there is an absorption band at a wavelength of 240–245 nm and a weak band at 430 nm, which is characteristic of benzoquinone. In the IR spectrum of the product, absorption bands were detected in the region of 1644 cm−1, which is characteristic of the oscillations of the C=O bonds of the carbonyl group of benzoquinone. The peaks also found at 1353 cm−1 and 1229 cm−1 may be due to vibrations of the C-H and C-C bonds of the quinone ring. It was found that among the synthesized catalysts, the Fe3O4/SiO2 catalyst demonstrated the greatest activity in the reaction of liquid-phase oxidation of phenol.

[Characteristics and Generation Mechanism of Secondary Inorganic Ions in PM2.5 in Changsha-Zhuzhou-Xiangtan City Group].

Secondary inorganic ions, the main components of atmospheric PM2.5, are a dominant contributor to haze formation. The detailed characteristics and main generation mechanism of secondary inorganic ions in PM2.5 are still unclear in the Changsha-Zhuzhou-Xiangtan City Group, which is suffering from severe haze pollution, particularly in the autumn and winter seasons. For our study, we collected PM2.5 samples in November 2020 and January 2021 from four urban sites in the Changsha-Zhuzhou-Xiangtan City Group. Secondary inorganic components such as SO42-, NO3-, and NH4+ in PM2.5 were quantified. The average values(μg·m-3) of ρ(SO42-), ρ(NO3-), and ρ(NH4+) in autumn and winter were(5.2±2.5) and(7.9±4.8),(4.1±2.2) and(7.2±4.2), and(17.1±10.5) and(7.8±5.2), respectively. During the heavy haze pollution events in winter, the sum of ρ(SO42-), ρ(NO3-), and ρ(NH4+)(SNA) contributed 72.7% to the growth of PM2.5 mass concentration, and ρ(NO3-) accounted for 41.2%. This result suggested that the generation of NO3- was the key factor leading to the formation of winter haze pollution. In the polluted stage, high aerosol water content(AWC) promoted the rapid secondary generation of SNA, whereas adverse meteorological conditions also led to the accumulation of pollutants. The values of sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) were still high in the dissipation stage. It indicated that the PM2.5 concentration fell due to the reduction in primary emissions and favorable weather conditions in dissipation, instead of the weakening of secondary generation of SNA. Compared to that in autumn, the higher AWC concentration, pH value, and lower temperature in winter were the main factors for the higher ρ(NO3-)/ρ(PM2.5) and NOR values in the Changsha-Zhuzhou-Xiangtan City Group. At the same time, the heterogeneous reaction was the main generation pathway of NO3-, when the AWC concentration was high in winter. Affected by aerosol pH value and generation rate, the liquid-phase oxidation reactions of H2O2 and SO2 were the main generation pathways of SO42- in autumn and winter in the Changsha-Zhuzhou-Xiangtan City Group. Compared to that in autumn, the higher AWC was more conducive to forming SO42-, which led to higher SOR in winter.

Diluted oxygen realizes high productivity of 2,5-Furandicarboxylic acid under ambient temperature

The oxidation of biomass-derived 5-hydroxymethyl furfural (HMF) into 2,5-Furandicarboxylic acid (FDCA) is a favorable reaction since FDCA is an ideal alternative to petroleum-based monomer terephthalic acid in bio-based polyester industry. However, producing FDCA with high yield under mild conditions is still challenging, especially at energy-saving near-ambient temperatures. Here, we present a Pd nanoparticles catalyst supported on Vulcan XC-72 carbon (Pd/VC) that can completely convert HMF and achieve an encouraging FDCA yield (92.4%) at 30 ℃. The most important observations include yield declines at pure oxygen bubbling, and the transformation of intermediates becomes stagnant; instead, switching to the diluted oxygen is effectively driving the tandem oxidation as the over-oxidation, and thus, rapid deactivation of the Pd surface could be alleviated. The negative effect of high oxygen concentration also occurs in the dehydrogenation and oxygenation of an extended substrate. Since the decisive influence of oxygen content has often been neglected in past investigations of oxidative transformation over Pd-based catalysts, the current study may offer a critical reminder for other liquid-phase oxidation reactions.

5,8-Di-tert-butyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione—A New Lipophilic N-oxyl Radical Precursor

N-hydroxyimides are widely known as organocatalysts for aerobic oxidation and oxidative coupling reactions, in which corresponding imide-N-oxyl radicals play the role of catalytically active hydrogen atom abstracting species. The drawbacks of many N-hydroxyimides are poor solubility in low polarity solvents and limited activity in the cleavage of unactivated C–H bonds. To overcome these shortcomings, we have synthesized a new lipophilic N-hydroxyimide, 5,8-di-tert-butyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione, with high solubility in low-polarity solvents such as DCM. According to the EPR study, the stability of the corresponding imide-N-oxyl radical is comparable to that of the non-tert-butylated analogue, naphthalimide-N-oxyl radical. DFT calculations showed that the NO–H bond dissociation enthalpy (BDE) in the synthesized tert-butylated-N-hydroxynaphthalimide is one of the highest in N-hydroxyimide series, which corresponds to high hydrogen atom abstracting reactivity and may be useful in catalysis of strong C–H bond oxidative cleavage. The synthesized compound can be considered as catalyst for liquid-phase free-radical oxidation and oxidative coupling reactions in non-polar media where solubility was previously the limiting factor.

Near Infrared Light-to-Heat Conversion for Liquid-Phase Oxidation Reactions by Antimony-Doped Tin Oxide Nanocrystals.

Effective utilization of the sunlight for chemical reactions is pivotal for dealing with the growing energy and environmental issues. So far, much effort has been focused on the development of semiconductor photocatalysts responsive to UV and visible light. However, the near infrared and infrared (NIR-IR) light occupying ∼50 % of the solar energy has usually been wasted because of the low photon energy insufficient for the band gap excitation. Antimony doping into SnO2 (ATO) induces strong absorption due to the conduction band electrons in the NIR region. The absorbed light energy is eventually converted to heat via the interaction between hot electrons and phonons. This Concept highlights the photothermal effect of ATO nanocrystals (NCs) on liquid-phase oxidation reactions through the NIR light-to-heat conversion. Under NIR illumination even at an intensity of ∼0.5 sun, the reaction field temperature on the catalyst surface is raised 20-30 K above the bulk solution temperature, while the latter is maintained near the ambient temperature. In some reactions, this photothermal local heating engenders the enhancement of not only the catalytic activity and selectivity but also the regeneration of catalytically active sites. Further, the photocatalytic activity of semiconductors can be promoted. Finally, the conclusions and possible subjects in the future are summarized.

Zeolite encapsulated organometallic complexes as model catalysts.

Heterogeneities in the structure of active centers in metal-containing porous materials are unavoidable and complicate the description of chemical events occurring along reaction coordinates at the atomic level. Metal containing zeolites include sites of varied local coordination and secondary confining environments, requiring careful titration protocols to quantify the predominant active sites. Hybrid organometallic-zeolite catalysts are useful well-defined platform materials for spectroscopic, kinetic, and computational studies of heterogeneous catalysis that avoid the complications of conventional metal-containing porous materials. Such materials have been synthesized and studied previously, but catalytic applications were mostly limited to liquid-phase oxidation and electrochemical reactions. The hydrothermal stability, time-on-stream stability, and utility of these materials in gas-phase oxidation reactions are under-studied. The potential applications for single-site heterogeneous catalysts in fundamental research are abundant and motivate future synthetic, spectroscopic, kinetic, and computational studies.

Chemical characteristics of three-stage fog water in an agricultural city in China

To investigate the relationships among the chemical compositions of fog droplets, atmospheric pollutants, and the fog microphysical characteristics, four fog cases were sampled in a comprehensive field experiment conducted at the Donghai site in an agricultural city, China, in the winter of 2020. The pH, electrical conductivity (EC), total ion concentration (TIC), and chemical compositions of the fog water were all size-dependent. High concentrations of non-sea-salt calcium (nssCa2+) and NH4+ led to the alkaline pH of 6.13–7.32. The TIC of fog water was relatively high, especially in small droplets of diameter within 4–16 μm (463527.9 μeq/L). The relatively high NO2− concentration was also found in the fog water, dominated by the non-homogeneous chemical reaction between NO2 and fog droplets. An interesting finding is that the TIC of fog water measured on December 12 was much higher than that measured on December 11. Compared to the first fog, the stronger thermal inversion and local emissions led to the higher concentration of atmospheric particles in the second fog. Generally, the relatively high concentration of atmospheric particles resulted in a large number of small-sized droplets, which had fast liquid-phase oxidation reaction rates and high gas-liquid conversion efficiencies, leading to a higher TIC in the fog water during the second fog.

Kinetics and mechanism of antioxidant action of triterpenoids in the liquid-phase oxidation reaction of 1,4-dioxane

Kinetics and mechanism of antioxidant action of triterpenoids in the liquid-phase oxidation reaction of 1,4-dioxane

Versatility of Supported Gold Nanoparticles on Hydrotalcites used for Oxidation and Reduction Reactions

Regardless of their size, supported gold nanoparticles are largely used for liquid-phase oxidation reactions. Small gold nanoparticles exhibit good performance during the reduction of organic compounds. The direct reduction of carboxylic acid to aldehyde is a famous and familiar reaction in the field of organic chemistry and is considered as one of the fundamental chemical transformations. Herein, we present Au/hydrotalcite, Au/MgO, and Au/Al2O3 systems as heterogeneous versatile catalysts to realize the oxidation of furfural (FF) to furoic acid (FA) and realize the reduction of FA to FF. Experiments showed that in standard aqueous conditions under air, FF can be easily oxidized to FA. When DMSO was used as a solvent to conduct the experiments under an atmosphere of CO2, FA was reduced to FF. The Au/HT series of catalysts was found to be active in both transformations, pointing out the versatility of the gold-based catalysts. The activity significantly depends on the acid-base properties of the catalyst.

On the role of bismuth as modifier in AuPdBi catalysts: Effects on liquid-phase oxidation and hydrogenation reactions

There is much about the action of bismuth within heterogeneous catalysis that still require a deeper understanding. We observed that, when Bi was added to AuPd bimetallic nanoparticles (NPs) supported on activated carbon, Bi affected the activity and significantly alters the selectivity in two model liquid phase reactions, namely the oxidation of cinnamyl alcohol and the hydrogenation of cinnamaldehyde. A combination of transmission electron microscopy and X-ray absorption spectroscopy provided a detailed characterization of trimetallic AuPdBi systems. We propose that the introduction of bismuth on AuPd NPs results in a partial blockage of most active sites, limiting the occurrence of consecutive reactions.

Extra-Large Pore Titanosilicate Synthesized via Reversible 3D–2D–3D Structural Transformation as Highly Active Catalyst for Cycloalkene Epoxidation

Titanosilicates with extra-large pores or cages are expected to effectively release the diffusion constraints suffered by the bulky substrates in the hydrogen peroxide-involved liquid-phase selective oxidation reactions. A reversible 3D–2D–3D structural transformation was developed to fabricate a highly active IWV-type titanosilicate (Ti-IWV) with a two-dimensional intersecting 12-membered ring (MR) channel system and extra-large 14-MR supercages. The IWV germanosilicate was readily disassembled into a layered 2D material (Hydro-IWV) in HNO3 aqueous solution, which was reconstructed to Ti-IWV with various Ti contents (Si/Ti ratio of 40–∞) through the (NH4)2TiF6-assisted isomorphous substitution of Ti and structure repair. The fluoride anions were critical to recover the interlayer double-four-ring (d4r) units, which were destroyed in the hydrolysis process. Ti-IWV was extremely active in the liquid-phase epoxidation reaction of cycloalkenes, especially showing a much higher conversion (99%) for cyclooctene than conventional titanosilicates. Rather than diffusion rate, the high capacity for the adsorption of bulky alkene molecules of extra-large 14-MR cages contributed to the outstanding activity of Ti-IWV.

Liquid-phase oxidation of 2-chlorotoluene with ozone to 2-chlorobenzoic acid – an intermediate for diclofenac sodium production

2-Chlorobenzoic acid is used as an intermediate for diclofenac sodium production. In industry, it is obtained by oxidation of 2-chlorotoluene with potassium permanganate in an aqueous acidic medium. Due to the deficiency and cost of the oxidant as well as the formation of large amounts of toxic wastewater, the known method has no future. Therefore, an urgent task is to develop a new, low-waste synthesis of 2-chlorobenzoic acid using the available and ballastless oxidant – ozone. The kinetics and mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone are studied. It was found that the oxidation of the substrate with ozone occurs mainly in the aromatic ring with the formation of aliphatic peroxide compounds. Increasing the temperature to 90 °C and introducing the catalyst – cobalt (II) acetate – into the system contributes to an increase of oxidation selectivity by the methyl group from 18.0% to 92.5 %. Among the aromatic products, 2-chlorobenzoic acid (88.0 %) and 2-chlorobenzaldehyde (4.2 %) are formed.The aim of the work is to study the kinetics, the mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone and to develop a new method of 2-chlorobenzoic acid synthesis basing on the research performed.Materials and methods. Glacial acetic acid manufactured by Sigma, “Ch. P.” qualified; 2-chlorotoluene, 2-chlorobenzaldehyde, 2-chlorobenzoic acid manufactured by company Acros organics company, “Ch. P.” qualified; cobalt (II) acetate, “Ch. P. qualified” were used in the experiments. Studies of the reaction mass quantitative composition were performed by gas-liquid chromatography. 2-chlorobenzoic acid was determined with potentiometric titration. Ozone concentration at the reactor inlet and outlet was determined by the absorption spectrophotometric method in the range of 254–290 nm on a SF-46 spectrophotometer designed to measure the transmission coefficients of liquid and solid transparent substances in the spectral range from 190 nm to 1100 nm.Results. The kinetics and mechanism of the liquid-phase oxidation reaction of 2-chlorotoluene with ozone have been studied. It was found that raising the temperature to 90°C and introducing a catalyst – cobalt (II) acetate – into the system results in an increase in the selectivity of oxidation by the methyl group from 18.0 % to 92.5 %. Among the aromatic products, 2-chlorobenzoic acid (88.0 %) and 2-chlorobenzaldehyde (4.2 %) are formed.Conclusions. During the oxidation of 2-chlorotoluene with ozone in acetic acid, mainly aliphatic peroxide compounds are formed, and 2-chlorobenzoic acid is formed only with a yield of 16.5 %. Increasing the temperature to 90 °С and introducing cobalt (II) acetate into the catalyst system makes it possible to direct the process mainly to the methyl group with the formation of 88.0 % 2-chlorobenzoic acid.

Investigation of Synergistic Effects between Co and Fe in Co3-xFexO4 Spinel Catalysts for the Liquid-Phase Oxidation of Aromatic Alcohols and Styrene

Transition metal oxides are attractive catalyst alternatives in liquid-phase oxidation reactions due to their lower cost and higher abundance compared with conventional noble metal catalysts. We investigated the catalytic properties of a systematic series of Co3-xFexO4 spinel catalysts synthesized by a hard-templating method, which were applied in the liquid-phase oxidation of styrene, benzyl alcohol and cinnamyl alcohol. O2 and tert-butyl hydroperoxide (TBHP) were used as the oxidants in a comparative manner. For alcohol oxidation, TBHP leads to similar or slightly higher selectivity to the corresponding aldehydes compared with O2. For the activation of C=C bonds, TBHP favors the oxidative cleavage pathway, while O2 favors the epoxidation pathway. The comparison of the catalytic performance revealed that the activity of Co3O4 does not benefit from Fe doping using O2 as the oxidant, while the substitution of Fe ≤ 10 % in the spinel structure is beneficial when TBHP is used. This is attributed to the different activation mechanisms of the oxidizing agents, being spin transfer in case of O2 and partial decomposition in case of TBHP. Heterogeneity tests and reusability studies demonstrated the stability of the spinel catalysts.

Catalytic performance of V-MCM-41 nanocomposites in liquid phase limonene oxidation: Vanadium leaching mitigation

Chemical stability and catalytic performance of MCM-41 materials functionalized with vanadium by template-ion exchange (TIE) were studied. Solids with different vanadium loadings were synthesized and characterized by a multi-technique approach. Their textural and chemical properties were analyzed by low and high angle XRD, N 2 adsorption-desorption, SEM, UV–vis DR, XPS, FTIR-Py and ICP-OES. All solids exhibited a highly ordered mesoporous structure, characteristic of MCM-41 materials. Their specific areas, pore diameters and pore volumes were found to be suitable for application as catalysts in liquid phase oxidation reactions. From different tests of limonene oxidation with H 2 O 2 , it was found that isolated cations (V δ+ ) are more likely to be the active sites for this reaction. Additionally, results show that high vanadium content actually lowers catalytic performance and favors sub-product formation by secondary reactions. Recycling tests were performed using the lowest vanadium content sample, finding that considerable leaching of active species took place after two reactions cycles. Wet impregnation with titanium was tested as a strategy for vanadium leaching mitigation. Solids with different titanium loadings were synthesized and evaluated. One of the bimetallic materials was selected according to its enhanced catalytic activity which accounts for an interesting synergistic effect between vanadium and titanium. This solid also displayed a superior chemical stability, since the absence of leaching was successfully proven in successive reaction cycles. • V-MCM-41 solids were successfully synthesized by TIE and extensively characterized. • Solids with different V loading were tested in limonene oxidation with H 2 O 2 . • The lowest V content solid exhibited the best catalytic performance. • Significant leaching of V species was detected after successive reaction cycles. • Ti impregnation is featured as an attractive strategy for V leaching mitigation.

Influence of the Method of Preparation of the Pd-Bi/Al2O3 Catalyst on Catalytic Properties in the Reaction of Liquid-Phase Oxidation of Glucose into Gluconic Acid

Gluconic acid and its derivatives are extensively used in pharmaceutical, food, textile, and pulp and paper branches of industry during production of food additives, cleansers, medicinal drugs, stabilizers, etc. To obtain gluconic acid, the method of conversion of glucose into gluconic acid by molecular oxygen in the presence of solid catalysts is promising. The process of obtaining Pd and bimetallic nanoparticles Pd-Bi, coated on Al2O3, has been considered in the work. Samples were prepared by combined and successive impregnation of the Al2O3 support using metalloorganic precursors Pd(acac)2, Bi(ac)3, and dissolved in an organic solvent (acetic acid), followed by the removal of excess solvent. To achieve the formation of Pd and bimetallic nanoparticles Pd-Bi on the substrate surface, the synthesized samples were subjected to thermal decomposition sequentially in the atmosphere of Ar, O2, and H2. The surface of the obtained catalysts was studied by a combination of physicochemical methods of analysis. The catalysts were analyzed in the reaction of liquid phase oxidation of glucose. The best results are achieved in the presence of the catalyst obtained by combined impregnation.

Evaluation on the Activity of Surfactant Immobilized and Metal Cation Exchanged Impregnated Montmorillonite Nanoclays on Oxidation of Benzyl Alcohol

Nanoclay minerals received considerable importance in the field of material applications and organic synthesis because of natural occurrence, greater surface area, good selectivity, ion exchange properties, economical, functional simplicity, easy modification, and environmental acceptability. The eco-friendly liquid-phase oxidation reaction of benzyl alcohol over modified nanoclays such as metal cation exchanged impregnated nanoclays and surfactant immobilized with oxyanions of Cr(VI) and Mn(VII) yields benzaldehyde. Surfactant immobilized (HDTMA-Cr(VI)/Mn(VII)-MMT-nanoclays) and impregnated Mn+-MMT-Cr(VI)/Mn(VII)-nanoclays were prepared and the activity of modified nanoclays were studied. The oxidation reactions were carried out by varying the molar mass of the modified nanoclays with active species, reaction period and amount of catalyst on the yield of benzaldehyde. Surfactant immobilized nanoclays were found to be more active than impregnated nanoclays. The percentage yield of the product was calculated using 2,4-dinitrophenylhydrazine derivative. The materials used for this analysis were examined under different characterization techniques like XRD, SEM and TGA. From the XRD spectra was observed that the interlamellar spacing of montmorillonite nanoclay, Al3+-MMT-nanoclay, HDTMA-Cr(VI)-MMT-nanoclay and HDTMA-Mn(VII)-MMT-nanoclay were 9.81A, 9.931 A, 27.6 A and 28.0 A respectively. The superficial area of montmorillonite nanoclay has higher than modified nanoclay which was confirmed by SEM images. The TGA analysis stated that the used nanomaterial is thermally stable. The product obtained, benzaldehyde was indicated by TLC and confirmed by spectral studies like FTIR, 1H NMR and GC–MS. The activity of regenerated modified nanoclays was studied under standard experimental conditions up to the fourth generation. The result of different solvents on the yield of aldehyde was determined. The materials used are naturally occurring, safe to handle, environmentally friendly and reusable.

Aerobic Liquid-Phase Oxidation of Para-tert-Butylcumene to Hydroperoxide

The reaction of aerobic liquid-phase oxidation of para-tert-butylcumene (PTBC) in the presence of N-hydroxyphthalimide has been studied. It has been found that the selectivity for the tertiary hydroperoxide of PTBC is over 95–98% up to a hydrocarbon conversion of 35–50%. The reasonability of the use of this reaction in the process of joint production of PTBC and acetone is shown. The mechanism of the process is discussed.