Methyl Toluene Research Articles

Determining the Exposure Routes and Risk Assessment of Isocyanates in Indoor Environments.

Isocyanates are used as raw materials for polyurethane foams, paints, and building materials. The isocyanates can cause acute adverse health effects such as irritation of the respiratory tract, skin, and eyes, and induce asthma and sick house syndrome. However, investigations into the potential sources and risk assessments of indoor isocyanates are limited. Thus, this study aimed to determine the sources and exposure routes of isocyanates and to assess their risk in indoor environments. The results showed that household products, such as infant chairs, mattresses, and polyurethane foam spray, used in indoor environments are potential sources of atmospheric isocyanic acids (ICA). Toluene diisocyanate and methyl isocyanate pose relatively high risks to indoor environments. Total concentrations of isocyanates ranged from 38.2 to 1570ngg-1 in infant chairs, mattresses, and spray polyurethane foams. The indoor products can be indoor sources of ICA because emission rates of ICA from household products were observed in all products (0.0536-1.37ngg-1 d-1). Field observations showed that isocyanate concentrations in house-dust samples ranged from 0.194±0.126 (ethyl isocyanate) to 70.1±67.8 (ICA)ngg-1. Atmospheric isocyanate concentrations ranged from 0.0030±0.020 (propyl isocyanate) to 26.0±14.3 (ICA)ng m-3. An estimation of human exposure demonstrated that air inhalation was the major route of isocyanate exposure. The minimum margin of exposure values of methyl isocyanate and toluene diisocyanate were 523 and 655, respectively, for children, indicating that they may pose a relatively high risk.

Pemanfaatan Eceng Gondok dan Crude Palm Oil sebagai Bioaditif Bahan Bakar Kendaraan Bermotor

Eceng gondok contains chlorophyll which is an oxygenate type additive which can increase the combustion reaction in fuel and reduce exhaust emissions. Therefore, eceng gondok has the potential to be used as a bioadditive in fuel by adding carotene from crude palm oil which functions as an antioxidant through electron transfer, thereby protecting chlorophyll from autooxidation. The two chlorophyll and carotene extracts at a ratio of 0:1, 2:3, 3:1, 4:1, 3:2, and 1:0 respectively were mixed with toluene and Fatty Acid Methyl Ester as a bioadditive formula. in gasoline fuel. The research results show that there is an increase in octane value of 0.1-0.5% according to ASTM D 2699 and GC-FID and results in a reduction in CO and CO2 exhaust emissions of 52.38% and 37% respectively. .00% on the use of chlorophyll : carotene (2:3) bioadditives in gasoline. This shows that eceng gondok and crude palm oil can be used as bioadditives in gasoline motor vehicles.

Engineering of Halide Methyltransferase BxHMT through Dynamic Cross-Correlation Network Analysis.

Halide methyltransferases (HMTs) provide an effective way to regenerate S-adenosyl methionine (SAM) from S-adenosyl homocysteine and reactive electrophiles, such as methyl iodide (MeI) and methyl toluene sulfonate (MeOTs). As compared with MeI, the cost-effective unnatural substrate MeOTs can be accessed directly from cheap and abundant alcohols, but shows only limited reactivity in SAM production. In this study, we developed a dynamic cross-correlation network analysis (DCCNA) strategy for quickly identifying hot spots influencing the catalytic efficiency of the enzyme, and applied it to the evolution of HMT from Paraburkholderia xenovorans. Finally, the optimal mutant, M4 (V55T/C125S/L127T/L129P), exhibited remarkable improvement, with a specific activity of 4.08 U/mg towards MeOTs, representing an 82-fold increase as compared to the wild-type (WT) enzyme. Notably, M4 also demonstrated a positive impact on the catalytic ability with other methyl donors. The structural mechanism behind the enhanced enzyme activity was uncovered by molecular dynamics simulations. Our work not only contributes a promising biocatalyst for the regeneration of SAM, but also offers a strategy for efficient enzyme engineering.

Engineering of Halide Methyltransferase BxHMT through Dynamic Cross‐Correlation Network Analysis

AbstractHalide methyltransferases (HMTs) provide an effective way to regenerate S‐adenosyl methionine (SAM) from S‐adenosyl homocysteine and reactive electrophiles, such as methyl iodide (MeI) and methyl toluene sulfonate (MeOTs). As compared with MeI, the cost‐effective unnatural substrate MeOTs can be accessed directly from cheap and abundant alcohols, but shows only limited reactivity in SAM production. In this study, we developed a dynamic cross‐correlation network analysis (DCCNA) strategy for quickly identifying hot spots influencing the catalytic efficiency of the enzyme, and applied it to the evolution of HMT from Paraburkholderia xenovorans. Finally, the optimal mutant, M4 (V55T/C125S/L127T/L129P), exhibited remarkable improvement, with a specific activity of 4.08 U/mg towards MeOTs, representing an 82‐fold increase as compared to the wild‐type (WT) enzyme. Notably, M4 also demonstrated a positive impact on the catalytic ability with other methyl donors. The structural mechanism behind the enhanced enzyme activity was uncovered by molecular dynamics simulations. Our work not only contributes a promising biocatalyst for the regeneration of SAM, but also offers a strategy for efficient enzyme engineering.

Enhancement of catalytic activity of PAl-NaX catalyst for side-chain alkylation of toluene with methanol: Effects of dehydrogenation component Cu

Activation and desorption of the hydrogen atom in the toluene methyl is a restrictive step for side-chain alkylation of toluene with methanol (SATM). In this work, two dehydrogenation strategies were used to improve the catalytic performance, dehydrogenation component Cu was introduced in PAl-NaX catalyst as well as the acid-base property was adjusted by changing NaOH loading amount. The relationship among the percentage of acid-base sites, low valence Cu species and the catalytic performances was investigated combined with the multiple characterizations, like X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption (TPD) of NH3 and CO2, etc. together with ternary regression analysis. It is found that the dehydrogenation component Cu, especially low valence Cu species, promotes the selectivity of side-chain alkylation products to a certain degree, but base sites play an even more critical role in enhancing it.

Thermophysical properties of binary mixtures of diethyl ether as oxygenate with cyclohexane and aromatic hydrocarbons

Density (ρ), speed of sound (u), and refractive index (nD) were measured for the binary mixture of diethyl ether (1) + cyclohexane, benzene, and toluene (2) systems at T= (288.15 K to 298.15 K) and 0.1 MPa. The measured data were utilized to calculate excess molar volume (VmE), deviation in ultrasonic speed (Δu), and deviation in refractive index (ΔnD). Our results illustrate that the positive value of VmE and negative value of Δu for diethyl ether + cyclohexane indicate the absence of specific interaction owing to the inert nature of cyclohexane and disruption of the dipole–dipole interactions in diethyl ether during mixing. Conversely, in diethyl ether + benzene or toluene system, the negative values of VmE and positive values of Δu suggest the presence of electron donor–acceptor interactions between the oxygen atom of diethyl ether and the π- electrons of benzene and toluene. These findings were further corroborated by the behavior of the molecular association parameter (MA), which showed that toluene exhibited the greatest value of MA and lower value of VmE compared to benzene, indicating a stronger degree of molecular association due increase in π-electron density because of the presence of electron-donating methyl group in toluene. On the other hand, cyclohexane showed the lowest value of MA, suggesting the disruption of dipole–dipole interaction in diethyl ether. Schaff’s collision factor theory demonstrated high predictive power for ultrasonic speed compared to other models. These experimental data significantly impact advancing theoretical models, process design, material development in chemical industries, and our understanding of the basic behavior of mixtures across various scientific and technical domains.

Adsorption and decomposition steps on Cu(111) of liquid aromatic hydrocarbon precursors for low-temperature CVD of graphene: A DFT study

Low-temperature chemical vapor deposition (LT-CVD) of graphene using liquid aromatic hydrocarbons holds technological advantages over conventional growth from methane. However, the nature of decomposition mechanisms of such precursors and their effectiveness in a LT-CVD process is still debated. We investigate by means of density functional theory adsorption energies and decomposition first steps on Cu(111) of single-ring aromatic hydrocarbons, such as benzene and toluene. Our results confirm the stronger stability with respect to methane of aromatic adsorbates, due to exchange of London dispersion forces with Cu surface; however, toluene exhibits improved bindings with respect to benzene. The adsorption energy slightly improves if additional methyl groups are substituted in benzene, as in o-xylene and 1,2,3-trimethylbenzene. Among decomposition reactions, dehydrogenation of the methyl group in toluene is energetically more favored (1.20 eV) than that of methane (1.52 eV) or aromatic C-rings (1.67 eV and 1.72 eV for benzene and toluene), while demethylation of toluene remains negligible due to the prohibitive energy barrier (2.49 eV). Methyl dehydrogenation in toluene leads to the abundant formation of adsorbed benzyl radicals onto Cu in an almost parallel-to-surface configuration, as active species for graphene nucleation. Toluene (and to a lesser extent o-xylene and 1,2,3-trimethylbenzene) should be thus preferred to benzene in LT-CVD of graphene.

Solubility analysis of 18 active pharmaceutical ingredients and intermediates in the non-polar solvents dioxane, toluene and cyclopentyl methyl ether

The temperature dependent solubility of 18 organic compounds, of which some are active pharmaceutical ingredients, was measured in 1,4-dioxane, toluene and cyclopentyl methyl ether over a temperature range between 0 and 70 °C using a turbidity method. The solubility of the studied compounds in the three solvents increases with temperature in all binary solute-solvent systems, and all compounds exhibit a higher solubility in 1,4-dioxane than in toluene and cyclopentyl methyl ether. The non-ideal behaviour of the binary systems was evaluated in terms of the activity coefficient. All the compounds in toluene presented a positive deviation from ideal solution, while both positive and negative deviations were observed for the model compounds in the other two apolar solvents. From the solubility and the activity coefficient, a number of thermodynamic models including van’t Hoff, Apelblat, λh, Margules, van Laar, Wilson, and the Non-Randomness Two Liquids (NRTL) were used for the correlation of the experimental data. The NRTL and the van’t Hoff equations present closer overall correlations, while the Margules and the λh models show deviations >5 % for several compounds in the three solvent systems. The mixing thermodynamic properties of the several solute-solvent systems were further analyzed by the van ‘t Hoff and Wilson equations for a better understanding of the solution behaviour. The analysis revealed systems with apparent ideal behaviour where counteracting non-ideality effects cancel each other’s.

Synthetic Reagents for Enzyme‐Catalyzed Methylation

AbstractLate‐stage methylation is a key technology in the development of pharmaceutical compounds. Methyltransferase biocatalysis may provide powerful options to insert methyl groups into complex molecules with high regio‐ and chemoselectivity. The challenge of a large‐scale application of methyltransferases is their dependence on S‐adenosylmethionine (SAM) as a stoichiometric, and thus exceedingly expensive co‐substrate. As a solution to this problem, we and others have explored the use of methyl halides as reagents for the in situ regeneration of SAM. However, the need to handle volatile electrophiles, such as methyl iodide (MeI), may also hamper applications at scale. As a more practical solution, we have now developed an enzyme‐catalyzed process for the regeneration of SAM with methyl toluene sulfonate. Herein, we describe enzymes from the thiopurine methyltransferase family that accept sulfate‐ and sulfonate‐based methyl donors to convert S‐adenosylhomocysteine into SAM with efficiencies that rival MeI‐based reactions.

Synthetic Reagents for Enzyme‐Catalyzed Methylation

Late-stage methylation is a key technology in the development of pharmaceutical compounds. Methyltransferase biocatalysis may provide powerful options to insert methyl groups into complex molecules with high regio- and chemoselectivity. The challenge of a large-scale application of methyltransferases is their dependence on S-adenosylmethionine (SAM) as a stoichiometric, and thus exceedingly expensive co-substrate. As a solution to this problem, we and others have explored the use of methyl halides as reagents for the in situ regeneration of SAM. However, the need to handle volatile electrophiles, such as methyl iodide (MeI), may also hamper applications at scale. As a more practical solution, we have now developed an enzyme-catalyzed process for the regeneration of SAM with methyl toluene sulfonate. Herein, we describe enzymes from the thiopurine methyltransferase family that accept sulfate- and sulfonate-based methyl donors to convert S-adenosylhomocysteine into SAM with efficiencies that rival MeI-based reactions.

Separation of ethyltoluene isomers by nonporous adaptive crystals of perethylated and perbromoethylated pillararenes

The separation of p-ethyltoluene (PET) and m-ethyltoluene (MET) is one of the most challenging steps to isolate PET from C9 aromatic compounds due to their very close boiling points. Many kinds of separation methods have been developed, but they involve low efficiency and great energy consumption. Herein, we investigate the adsorptive properties of perethylated pillar[5]arene (EtP5), perethylated pillar[6]arene (EtP6), perbromoethylated pillar[5]arene (BrP5) and perbromoethylated pillar[6]arene (BrP6) for ethyltoluene isomers. Results show that EtP6 and BrP5 crystals separate PET from a PET/MET equimolar mixture with purities of 95.4% and 92.0%, respectively. Both of them show no decrease in selectivity upon cycling for 5 times. Relatively, EtP5 and BrP6 crystals fail in this separation due to poor PET capture ability and low selectivity, respectively.

Comparison of surface passivation modification of two mordenite zeolites and their application on the isomerisation of o-ethyltoluene.

During the isomerisation of o-ethyltoluene (O-ET) to produce m-ethyltoluene (M-ET) and p-ethyltoluene (P-ET), it is crucial to improve the isomerisation selectivity and reduce side reactions, such as disproportionation, alkyl transfer, and splitting. In this study, in order to improve the selectivities toward M-ET and P-ET during O-ET isomerisation, both the commercial micropore mordenite (HM) and the prepared micro-mesoporous mordenite (HM-M) were treated through chemical liquid deposition using tetraethyl orthosilicate (TEOS) and 3,5-dimethylphenylmagnesium bromide (DPB), respectively. Thereafter, their structure, porosity, and acidity were characterized via X-ray diffraction, transmission electron microscopy, inductively coupled plasma, N2 sorption, temperature-programmed desorption of ammonia, Fourier-transform infrared spectroscopy of pyridine and 2,6-di-tert-butylpyridine, and thermal analysis. The deposition mechanism of DPB was also discussed. The results showed that TEOS could shrink and block the micropores of mordenite. By contrast, DPB passivated the external surface acidity and did not affect the micropore structure. Moreover, HM modified using DPB significantly shortened the self-coking process, improved the product selectivities for M-PT and P-ET as well as their stability, and prolonged the catalytic life. When the amount of magnesium oxide (MgO) deposited on the HM zeolite was 4%, the product selectivities toward M-ET and P-ET increased from 67.27% to 77.54%, and the yields of M-ET and P-ET increased from 47.57% to 52.98%. However, the performance of the catalyst was not significantly enhanced on the HM-M, owing to the passivation of acidic sites in the mesopores by the TEOS and DPB.

Enhancing the Catalytic Properties of Mordenites via an Alkali-Acid Treatment and by Loading Nickel-Cerium during o-Ethyltoluene Isomerization.

The catalytic performance of the selective isomerization of o-ethyltoluene (O-ET) is crucial to increasing the m-ethyltoluene (M-ET) and p-ethyltoluene (P-ET) yields. During the isomerization of O-ET, traditional (commercial) mordenites (HM) are generally limited by a high reaction temperature (235 °C), as well as a low yield of the isomerization product (49.0%). In this study, micro-mesoporous mordenites were obtained by treating commercial mordenites with NaOH, NaOH–HNO3, and NaOH–mixed acid (HNO3–oxalic). Thereafter, their structure, porosity, and acidity were investigated via X-ray diffraction, transmission electron microscopy, inductively coupled plasma, N2 sorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy of pyridine, temperature-programmed desorption of ammonia, and nuclear magnetic resonance. Among the various treated samples, the accessibility of the acidic sites and the B/L value of the alkali–mixed HNO3–oxalic one were enhanced, achieving the highest yield (53.6%) and lowest reaction temperature (165 °C), thus significantly reducing the energy consumption of the reaction process. Furthermore, Ni and Ce were successfully loaded via the incipient wetness impregnation of the micro-mesoporous mordenite to significantly prolong the catalytic life. This study affords a new strategy for obtaining high M-ET and P-ET yields from the isomerization of O-ET in mixed C9 aromatics on an industrial scale.

Michel Boudart, Catalytica and catalytic combustion—A scientific odyssey

Catalytic steam reforming of propylene, benzene and toluene was investigated over Mn-Cr-O spinel oxides with different stoichiometry. The catalysts were structurally stable during reforming conditions except for Mn3O4, which reduced in situ to MnO. The Cr2O3 catalyst showed the highest initial rate for propylene reforming, whereas the Mn-rich Mn1.5Cr1.5O4 spinel was the most active and stable catalyst for aromatic reforming. Reforming rates of olefins and aromatics were comparable under 0.05 bar hydrocarbon and 0.40 bar steam at 873 K. The reforming rate of olefins and aromatics was first order in hydrocarbon and slightly inhibited by H2O, which is consistent with a Mars-van Krevelen type mechanism. Of the hydrocarbons investigated, only the rate of toluene reforming was negative first order in excess H2. Results from diffuse reflectance infrared Fourier transform spectroscopy of adsorbed toluene on a spinel catalyst suggest that H2 inhibits the rapid oxidation of the methyl group of toluene.

Steam reforming kinetics of olefins and aromatics over Mn-Cr-O spinel oxides

Catalytic steam reforming of propylene, benzene and toluene was investigated over Mn-Cr-O spinel oxides with different stoichiometry. The catalysts were structurally stable during reforming conditions except for Mn3O4, which reduced in situ to MnO. The Cr2O3 catalyst showed the highest initial rate for propylene reforming, whereas the Mn-rich Mn1.5Cr1.5O4 spinel was the most active and stable catalyst for aromatic reforming. Reforming rates of olefins and aromatics were comparable under 0.05 bar hydrocarbon and 0.40 bar steam at 873 K. The reforming rate of olefins and aromatics was first order in hydrocarbon and slightly inhibited by H2O, which is consistent with a Mars-van Krevelen type mechanism. Of the hydrocarbons investigated, only the rate of toluene reforming was negative first order in excess H2. Results from diffuse reflectance infrared Fourier transform spectroscopy of adsorbed toluene on a spinel catalyst suggest that H2 inhibits the rapid oxidation of the methyl group of toluene.

Toluene-Sensing Properties of Mixed-Potential Type YSZ-Based Gas Sensors Attached with Au-Based Electrodes Prepared By a Spin-Coating Method

Introduction Exhaled breath of patients contains a higher concentration of specific gases than that of healthy people. For example, the patients suffering from lung cancer, diabetes and periodontitis release a high concentration of toluene, acetone and hydrogen sulfide and/or methyl mercaptan, respectively [1, 2]. Among various kinds of gas sensors, solid-electrolyte gas sensors have shown enhanced sensing properties to volatile organic compounds (VOCs) by optimizing the composition and/or microstructure of the sensing electrode (SE) [3]. We also reported that sensors attached with thin-film CeO2-added Au SEs (thickness: 30‒100 nm) fabricated by a spin-coating method showed large response to toluene at 500°C. In addition, the toluene response of the sensors attached with a 24 wt% CeO2-added Au SE increased with an increase in the SE thickness, and the sensor attached with the thickest SE showed the largest response [4]. In this study, effects of the change in the additive amount of CeO2 to Au SE, operating temperature, and toluene concentration on the sensing properties of the sensors were evaluated, and their sensing mechanisms were discussed. Experimental CeO2-added Au SEs were fabricated by a spin-coating method. The coating solution was prepared by the addition of Ce(NO3)3ˑ6H2O and polyvinyl alcohol into a 0.1 M HAuCl4 aqueous solution. The solution was dropped on the YSZ substrate, and it was spun at 3000 rpm for 30 s, followed by the heat treatment at 300°C. This process was repeated multiple times to increase the film thickness. Then, they were annealed at 700°C for 2 h in air. The obtained SEs were denoted as nCeO2/Au(x) SEs (n: an additive amount of CeO2, 8‒24 (wt%), x: the number of spin-coating cycle, 5–15). A Pt paste was screen-printed on the backside of the YSZ as the counter electrode (CE), and it was annealed at 700°C for 2 h in air. Sensing properties of the fabricated sensors (nCeO2/Au(x) sensors) to 50 ppm toluene in dry air were measured in a flow apparatus (gas-flow rate: 100 cm3 min−1) at 450‒550°C. The SE was exposed to a sample gas, while the CE was always exposed to dry synthetic air during gas response measurements. The open-circuit voltage between the two electrodes (E, mV) of the sensors as a sensing signal was measured with a digital electrometer, and the response (ΔE) was defined as the difference in E between in dry air and in toluene balanced with dry air. The microstructure of the sensors was observed by scanning electron microscopy (SEM; JEOL Ltd., JSM-7500F). Results and Discussion The thickness of the SEs increased with the number of spin-coating cycles, and the thickness was not affected by the additive amounts of CeO2 in the examined number of spin-coating cycles (x). Therefore, the SE thickness was controlled from 30 to 100 nm only by changing the x value [4]. Figure 1 shows response transients of the nCeO2/Au(x) sensors (n: 8, 24, x: 5, 10, 15) to 50 ppm toluene at 450 and 550°C in dry air. The E values of all the sensors negatively shifted upon exposure to toluene, but ΔE was largely affected by the SE thickness and the additive amount of CeO2 at both temperatures. ΔE of the 8CeO2/Au(x) sensors largely decreased with an increase in the thickness of SE, and the values observed at 550°C was much smaller than that at 450°C. Generally, the VOC-sensing mechanism of solid-electrolyte gas sensors can be explained on the basis of the mixed potential theory [3]. Based on the theory, the electrochemical oxidation of toluene and electrochemical reduction of oxygen simultaneously proceed at triple phase boundaries (TPBs) at the interface between SE and YSZ, when toluene diffuses in SE and reaches TPBs [5]. In addition, a certain amount of toluene is catalytically oxidized during the diffusion in SE. Therefore, the actual concentration of toluene at TPBs decreased with an increase in both the SE thickness and the operating temperature, which resulted in the largest toluene response of the 8CeO2/Au(5) sensor at 450°C among the 8CeO2/Au(x) sensors. However, ΔE of the 24CeO2/Au(x) sensors increased with an increase in the thickness of SEs at both temperatures. In addition, ΔE of the 24CeO2/Au(5) sensor at 550°C was larger than that at 450°C, while ΔE of the 24CeO2/Au(x) sensors (x: 10, 15) at 550°C was smaller than that at 450°C. This behavior probably arises from the increase in the number of active sites for electrochemical toluene oxidation in the CeO2-added Au SE. The details of the response properties and gas-sensing mechanism of these sensors will be discussed in the presentation.

The mechanism of toluene absorption by phosphonium ionic liquids with multiple sites

It is important to understand the mechanism of toluene absorption by phosphonium ionic liquids (PILs) for volatile organic compound removal with ionic liquids. In this work, the molecular structures of trimethyl(butyl)phosphonium tetrafluoroborate ([P1114][BF4]), trimethyl(butyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P1114][Tf2N]), tributyl(propyl)phosphonium tetrafluoroborate ([P4443][BF4]) and tributyl(propyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P4443][Tf2N]) were optimized by quantum chemical calculations at the GGA/PW91 level with the DNP basis set of density functional theory (DFT). The most stable configurations for toluene absorption by these PILs with multiple sites were also obtained by calculation under the same conditions. The main parameters for the most stable structure, data for the Mulliken charge and frontier molecular orbitals were further determined and discussed. It was found that the interactions of PILs with toluene are mainly composed of hydrogen bonds, C-H···π bond interactions and electrostatic attraction, and most of the calculated frontier molecular orbitals are concentrated on the toluene molecule. Additionally, analysis showed that [BF4]− is inclined to form hydrogen bonds with cations and the methyl groups of toluene, and [Tf2N]− tends to attract toluene via electrostatic attraction. Investigation of the absorption energy with multiple sites indicated that PILs have great performance for toluene absorption. Analysis of the ionic size and geometric structure of the PILs demonstrated that the space available for accommodating toluene is an important condition for toluene absorption and is mainly provided by cations. In particular, PILs with cations having suitable long alkyl side chains show excellent capacity for toluene absorption. Moreover, NBO and AIM analyses confirmed the existence of weak closed-shell interactions (hydrogen bonds and C-H···π bonds) between toluene and PILs. The experimental results obtained for the static toluene absorption by the PILs provide a great supplement and confirmation of the calculations

Surface In Situ Doping Modification over Mn2O3 for Toluene and Propene Catalytic Oxidation: The Effect of Isolated Cuδ+ Insertion into the Mezzanine of Surface MnO2 Cladding.

Heterocation insertion and substitution in tunnels and mezzanines of MnO2 present significant influences on the microchemical environment at the surfaces and interfaces. An innovative surface in situ doping modification method via Cu2+-H+/KMnO4 treatment was applied onto the Mn2O3 surface to provide Mn2O3@MnO2 nanospheres. Cu was stabilized into resulting MnO2 cladding substituting original K+ during a mild comproportionation reaction between Mn(VII) and Mn(III). The Cu25 (Cu(II): Mn(VII)atomic = 25%) catalyst shows significant promotion of the catalytic performance compared with bare Mn2O3 and Cu0 (without Cu involving). Isolated Cuδ+ was predominantly inserted into the mezzanine of the [MnO6]δ- layers in MnO2 instead of K+, leading to slight electron transfer from Cuδ+ to outermost Mn(4-ε)+ and a decrease of interlayer spacing as well as crystallinity. Such a configuration facilitates the formation of additional oxygen vacancies, promoting the redox ability and oxygen mobility at relatively low temperatures. The mechanistic study reveals that Cuδ+ in MnO2 cladding boosts the activation of toluene (methyl) to form benzoates and propene (methyl and double bonds) to form carboxylates, enhancing the chemical adsorption of reactants. Moreover, it also inhibits the unfavored accumulation of incomplete oxidized intermediates on the surface at high temperatures.

Direct conversion of toluene into styrene with high selectivity over a composite catalyst

Although side-chain methylation of toluene with methanol to produce styrene has been investigated in the past decades, commercial application of this process is still a great challenge due to the lack of efficient catalysts. Here we present a bifunctional catalyst composed of dehydrated sodium borate (Na2B4O7) and zeolite (CsX) that yields a high selectivity to styrene (89.6%) with a relative high toluene conversion (9.57%). Na2B4O7 not only contributes to the formation of the reaction intermediate formaldehyde but also constructs the frustrated Lewis pairs (FLPs) with basic sites on the zeolites, which could activate C–H bond in the methyl group of toluene more efficiently. Thus, the crucial role of boron species is revisited. The nature of cesium in CsX is found to be important for the reactivity of the bifunctional catalyst. Good reaction performance on composite catalyst Na2B4O7-CsX also depends on the spatial proximity and mass ratio of the two components.

Dihydrolevoglucosenone (Cyrene), a Biobased Solvent for Liquid–Liquid Extraction Applications

Dihydrolevoglycosenone, commercially known as Cyrene, is a versatile biobased solvent reported for various applications including being a medium of chemical reactions and membrane manufacture. In this work, application of Cyrene in liquid–liquid extractions has been investigated. Four ternary systems have been assessed at 298.15 K, 323.15 K, and 348.15 K, keeping Cyrene and methylcyclohexane constant and changing the third compound to toluene, cyclohexanol, cyclohexanone, and cyclopentyl methyl ether. Studying these selected ternary systems yielded an indication of applicability of Cyrene in related industrial separation processes such as aromatic/aliphatic separations and in separations of oxygenates in the cyclohexane oxidation process. Key factors are biphasic system formation, distribution coefficients, and selectivity. All ternary systems showed type I liquid–liquid phase behavior with a selective extraction of ternary components from methylcyclohexane by Cyrene. The highest selectivity at 298.15 K was found for cyclohexanol with 61.4 ± 4.33, followed by cyclohexanone with 44.1 ± 8.63, while toluene and cyclopentyl methyl ether had a selectivity of, respectively, 12.0 ± 0.89 and 6.4 ± 0.08. Although Cyrene is applicable in all four ternary systems, the miscibility gap is narrow for the oxygenated species, indicating a limited operation window for liquid–liquid extraction which will be more severe at higher temperatures. Overall, the studies showed that there are certainly application windows for Cyrene. In the case of oxygenate extraction, a process with Cyrene appears energy-saving because the energy duty appears to be lower than when using water, the best alternative solvent, which is a low boiling solvent for this purpose.