Nitration Of Toluene Research Articles

Heterogeneous toluene nitration with mixed acid in microreactors: Reaction regime, characteristics and kinetic models

It is critical for reactor design and process safety to determine the reaction kinetics for toluene nitration. Herein, a continuous-flow platform based on capillary microreactors was established. First, reaction regimes for toluene nitration and its consecutive side reaction (MNT (mononitrotoluene) nitration) were identified. On this basis, the influence of process parameters on conversion of toluene, selectivity of MNT and DNT (dinitrotoluene) and their isomer distribution were meticulously examined, including molar ratio of reactants, sulfuric acid strength, reaction temperature, and residence time. Subsequently, reaction kinetic models coupled with mass transfer were developed, allowing the simultaneous kinetic determination for toluene nitration and MNT nitration. It was found that the logarithm of the observed kinetic constant is proportional to the sulfuric acid strength. The kinetic parameters under 72.7 to 80.1 wt% sulfuric acid strengths were obtained. The outcomes provide a basis for process intensification and optimization of toluene nitration as well as other similar aromatics.

Process optimization and scale-up of toluene nitration in a microchannel reactor using HNO3-AC2O as nitrating agent

Aromatic nitro compounds are an important class of basic chemical raw materials, while traditional nitration methods may cause safety accidents and environmental pollution due to strong exothermicity and presence of sulfuric acid. In this work, aiming to alleviate these issues, the nitration of toluene was conducted in a microchannel reactor with nitric acid and acetic anhydride. The effect of temperature, molar ratio of nitric acid to toluene, mass fraction of acetic anhydride, and residence time on the conversion and selectivity of reaction were systematically investigated, and response surface methodology was used to optimize the process. A mononitrotoluene yield of 99.21 % can be achieved under optimum condition. Meanwhile, in order to better understand the exothermic behavior, toluene nitration by HNO3-AC2O was investigated in the semi-batch calorimeter. Finally, the optimized process was scaled up and effect of volumetric flow rate was investigated. At the selected maximum volumetric flow rate, the overtemperature of the system was 10.9 °C with a 98.3 % yield of mononitrotoluene. Continuous flow mode had a space-time yield nearly two orders of magnitude greater than semi-batch mode. This work can provide guidance for safe, efficient and green synthesis of mononitrotoluene.

Preparation of Solid Superacid SO42-/ZrO2 and SO42-/ZrO2-MxOy (M=Ce, Co, Mn, and Zn) and Its Application in Toluene Nitration.

The nitration reaction of aromatic compounds is one of the extensively studied chemical reactions that result in the manufacturing of various industrial products applied in pharmaceuticals, dyes, perfumes, and explosives. A series of modified sulfated zirconia (SZ) catalysts SO42-/ZrO2-MxOy (M=Ce, Co, Mn, Zn, and M/SZ) doped with different metal elements by a coprecipitation method were investigated in the toluene nitration reaction. Various characterization techniques (X-ray diffraction, Brunauer-Emmett-Teller, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature-programmed desorption of ammonia) indicated that doping metal elements in SZ led to excellent catalytic properties, increasing the specific surface area of the catalyst and facilitating the formation of a stable tetragonal zirconia phase. Doping zinc and cobalt in SZ enhanced the acidity of the catalyst and formed stronger acidic sites, promoting the generation of nitronium ions and providing more active sites for the toluene nitration reaction. Additionally, it reduced the loss of sulfate ions in the catalytic system that helped in improving the stability of the catalyst. Under the same conditions, the catalytic activity of toluene nitration reaction demonstrated the following order: Zn/SZ > Ce/SZ > Co/SZ > Mn/SZ > SZ, with the zinc-doped SZ catalyst exhibiting the best catalytic performance, achieving a toluene conversion rate of 78.58% and a para/ortho nitrotoluene ratio of 0.67.

Efficient and high para-selective conversion of toluene with NO2 to para-nitrotoluene in an O2–Ac2O–HβD4 composite catalytic system

In this work, we have developed a green method for the preparation of para-nitrotoluene through the catalytic nitration of toluene with nitrogen dioxide (NO2) under the promotion of dioxygen (O2).

Effect of Nickel Promoted Niobium Catalyst on Toluene Nitration Reaction

Effect of Nickel Promoted Niobium Catalyst on Toluene Nitration Reaction

Trimetallic spinel CuMnCoO4 as an efficient catalyst for solvent-free nitration of toluene to dinitrotoluene without sulfuric acid

The development of the direct nitration for toluene toward dinitrotoluene (DNT) under solvent-free and without sulfuric acid conditions over a heterogeneous catalyst is critical challenging undertakings for developing the green and efficient synthesis of DNT. Herein, trimetallic spinel CuMnCoO4 was prepared and investigated its catalytic performance for solvent-free toluene nitration with nitric acid as nitration agent in the absence of sulfuric acid. The selectivity of 2,4-dinitrotoluene (2,4-DNT) of the spinel-catalyzed-toluene-nitration-system was 1.6 times higher than that of the system without spinel. Kinetic studies revealed that the reaction step of MNT to DNT is the rate-limiting step and moderately increasing the nitric acid/toluene ratio and reaction temperature could enhance the toluene dinitration process. Characterization measurements showed that trimetallic spinel CuMnCoO4 led to an appropriate vacancy-lattice oxygen pair. The reaction mechanism to elucidate the synergetic effect of vacancy-lattice oxygen pair on promoting the activity of toluene and nitrating agent was proposed.

Effect of Nickel Promoted Niobium Catalyst on Toluene Nitration Reaction

A series of Ni–Nb2O5/SiO2 catalysts with varying Ni loadings (5–25 wt. %) were prepared. The catalytic activity of the materials was evaluated by nitration of toluene. Ni–Nb2O5/SiO2 catalyst showed good catalytic activity, selectivity, and reusability for the nitration of toluene. Under the optimal conditions, conversion of toluene by 88% to mononitrotoluene was achieved with 100% selectivity. Experiments were designed by the Minitab software, and the effect of reaction conditions was investigated. The optimal reaction condition was also achieved for the high amount of total products and the lowest amount of meta-isomer using this software. The reusability of catalyst also was studied in this work at the same operating conditions, and the catalyst was stable for four runs without losing catalytic activity.

Review of the Methods for Selective Nitration of Toluene

Review of the Methods for Selective Nitration of Toluene

A comparative study of the catalytic nitration of toluene over bimetallic Ce‐Mn modified Hβ zeolite

AbstractBimetallic cerium‐manganese modified Hβ zeolite sample (Ce/Mn‐Hβ) was prepared by ultrasonic assisted impregnation method and applied in nitration of toluene. The characterization results show that the active components (Ce and Mn) are successfully introduced into the framework of Hβ zeolite. The catalyst shows excellent catalytic activity and reusability for the nitration of toluene, giving high para selectivity. Under optimized conditions, it gives 68.7% selectivity to para‐nitrotoluene at 88.6% conversion over Ce/Mn‐Hβ in the presence of acetic anhydride (Ac2O). The theoretical calculations indicate that the Ce/Mn bimetallic active sites in modified Hβ zeolite can easily activate the nitrification reagent (AcONO2), and the enhancement of para selectivity is owing to the steric hindrance of catalyst. Furthermore, the reaction mechanism was proposed by the combination of experimental results and theoretical calculations.

Accurate determination of the kinetics of toluene nitration in a liquid–liquid microflow system

Accurate determination of the kinetics of toluene nitration in a liquid–liquid microflow system

CH3COOH.TiO2: An excellent catalyst for the green nitration of toluene by N2O4

The solvent-free nitration of toluene with N2O4 gas over solid acid catalysts is a green reaction for preparing the mono-nitrotoluene (NT) isomers. The acid-modified catalysts are more efficient than common catalysts for this type of reaction. For this purpose, a titanium dioxide (TiO2) catalyst is synthesized with a sol-gel method and modified by acetic acid to increase catalytic properties. The acid-modified TiO2 (CH3COOH·TiO2) is characterized by different analyses. To optimization of toluene nitration conditions, reaction temperature (X1) (30 < X1 < 60 °C), N2O4/toluene molar ratio (X2) (0.5 < X2 < 2), and the amount of catalyst (X3) (0.05 < X3 < 0.3 g) factors were investigated by Minitab software with the CCD-RSM. Three responses including the selectivity of meta-NT isomer (Sm), the ratio of para-NT to ortho-NT selectivity (Sp/o), and the selectivity of by-products (Sbp) were considered for the optimization. Statistical parameters were applied to evaluate the goodness of fitting for the models. Optimum values for X1, X2, and X3 parameters are 57.9 °C, 1.91, and 0.25 g, respectively. The conversion of toluene under these conditions is 93.2%. The comparison of Sm, Sp/o, and Sbp in CH3COOH.TiO2 (1.51%, 0.8, and 5.48%, respectively) with Fe2O3 (8.5%, 0.43, and 20.57%, respectively), SiO2 (8.43%, 0.48, and 16.24%, respectively), TiO2 (5.9%, 0.57, and 13.87%, respectively), TiO2–Fe2O3 (4.72%, 0.64, and 9.18%, respectively), and TiO2–SiO2 (4.42%, 0.67, and 5.73%, respectively) catalysts show that this catalyst has a low Sm and Sbp as well as a higher Sp/o than other mentioned catalysts. The mechanism of the mentioned reaction is reviewed in the presence of CH3COOH·TiO2 catalyst. The high stability of the CH3COOH·TiO2 is proved by the reusability test, and it is found that its stability against inactivation is more than the TiO2 catalyst.

Is a thin mechanism appropriate for aromatic nitration?

The mechanism of toluene nitration by NO2BF4 in dichloromethane solution is investigated by performing advanced ab initio MD simulations of the reaction trajectories, including at full quantum mechanical level the effects of both the solvent and of the counterion. The time evolution of the encounter complex, as well as that of the associated electronic structure, for different trajectories reveals that a single electron transfer step fastly occurs after reactants are accommodated in a common solvation shell, always preceding the formation of the σ-complex. The present results strongly suggest that the regioselectivity of the reaction is spin-density driven and that a thin mechanism, one based on reaction intermediates and transition states, can be appropriate to describe aromatic nitration.

Selective Nitration of Toluene using Nitrogen(V) Oxide in Dichloromethane and Catalysts

Selective Nitration of Toluene using Nitrogen(V) Oxide in Dichloromethane and Catalysts

Highly Efficient Microwave‐Assisted Fenton Degradation of Toluene Nitration Wastewater over Microwave‐Responsive Catalyst of Fe3O4−BiOCl

AbstractMicrowave‐assisted Fenton process over a high microwave‐responsive catalyst (Fe3O4−BiOCl) was developed. The morphology, composition and magnetic recovery of the prepared catalyst were analyzed. Correspondingly, the optimal reaction conditions were obtained and the catalyst had a good recovery performance. A good degradation result (COD removal efficiency=82.57 %, TOC removal efficiency=85.15 %, TN removal efficiency=80.86 %) was obtained with low energy consumption and chemical inputs, which proved that the system has a certain industrialization prospect. Furthermore, take p‐nitrophenol (PNP) as an example, The reaction mechanism of this process had been investigated. The reaction was divided into three stages: 1. Activation 2. Oxidation 3. Mineralization. In the Oxidation phase, the reaction followed zero‐order reaction kinetics model and the rate constant was 0.0642 mM s−1. To investigate the kinetics, a heterogeneous Fenton‐photocatalysis synergistic degradation mechanism based on experimental data was proposed.

Regioselective nitration of toluene to para‐nitrotoluene with NO2 over dealumination Hβ zeolite: Comparison of organic and inorganic acids

AbstractThis work presents a novel heterogeneous catalytic system for the preparation of para‐nitrotoluene (p‐NT) with nitrogen dioxide (NO2) as a nitrating agent in the presence of oxygen (O2). By applying dealuminated Hβ zeolite treated with oxalic acid (Hβ‐Ox) as a catalyst, p‐NT can be obtained with high conversion (90.5%) and selectivity (72.6%). In addition, it can be recycled at least five times without a significant decrease in catalytic activity. This result demonstrates that the catalyst has high efficiency, good stability, and regenerability. Meanwhile, the characteristics of pristine Hβ and different dealuminated Hβ zeolites modified with organic and inorganic acids were systematic contrastive studied using X‐ray diffraction (XRD), nitrogen (N2) adsorption‐desorption, Fourier‐transform infrared (FT‐IR), scanning electron microscope (SEM), temperature‐programed desorption of ammonia (NH3‐TPD), pyridine adsorption infrared (Py‐FT‐IR), and solid state 27Al nuclear magnetic resonance (27Al MAS‐NMR). Finally, the higher conversion and para‐selectivity over Hβ‐Ox also give a reasonable explanation in this paper.

Scale-up and safety of toluene nitration in a meso-scale flow reactor

In this study, toluene nitration was scaled up in a meso-scale flow reactor and safety was considered. The exothermic characteristic was demonstrated in a batch calorimeter. Parallel flow was observed in the flow channel and numerical simulation was carried out to show the hydrodynamics. Mass transfer coefficient of the reactor mixer was determined. The effects of flow rates, temperatures and molar ratios on toluene nitration in the flow reactor were analyzed. The conversion of toluene increased from 26% to 86% with the increase of flow rates while the impacts of temperatures and molar ratios were comparatively small. A productivity of 2572 kg/a could be achieved by this meso-scale flow reactor but the highest overtemperature inside the channel was more than 21.3 ∘C. A comparison between performances of the batch calorimeter and the flow reactor was also presented. The finding of this study can serve as a reference to design inherently safer meso-scale flow reactors for kinetically fast and highly-exothermic reactions.

Evolution of aerosol chemistry in Beijing under strong influence of anthropogenic pollutants: Composition, sources, and secondary formation of fine particulate nitrated aromatic compounds

Nitrated aromatic compounds (NACs) constitute a key segment of brown carbon (BrC), thereby contributing to the light-absorbing characteristics of aerosols in the atmosphere. However, until recently, there is a scarcity of research on their generation in the urban environment. The current study is based upon an extensive field study of NACs from fine particle samples obtained at an urban location in Beijing in the spring and summer of 2017, which was characterized by both high anthropogenic volatile organic compounds (VOCs) and high-NOx dominated conditions. The mean total concentration of the nine NACs was 8.58 ng m−3 in spring and 8.54 ng m−3 in summer. In the spring, the most abundant NACs were 4-nitrophenol (33.7%) and 4-nitrocatechol (19.3%), while in the summer, the most abundant NACs were 4-nitroguaiacol (34.9%) and 2, 4-dinitrophenol (23%). Atmospheric NACs were primarily produced from coal combustion (52%) and biomass burning (32%) in spring, and originated from the secondary formation (37%) and traffic (35%) in summer. NO2 could promote the formation of NACs with a significant effect on their compositions, especially for nitrophenols and nitrocatechols. It can also affect the formation of nitrated aerosols and their existing form. Inorganic nitrates were increased to conversion in the daytime when NO2 concentrations were higher than 30 ppb, but the corresponding oxidation products shifted to primarily organic ones at night. The transition was VOC-sensitive regimes for NAC formation, and nitration of toluene was a more important pathway during the campaign in Beijing.

Effect of metal nitrate on mechanochemical nitration of toluene

Mechanochemical nitration of toluene was explored using MoO3 as catalyst and different metal nitrates as sources of nitronium ion.

Mechanochemical nitration of toluene with metal oxide catalysts

Results of an experimental study of the mechanochemical nitration of toluene are presented. The focus is on the effect of acidity of metal oxide catalysts on the yield of mononitrotoluene. No solvents were used during the reaction. Sodium nitrate served as a source of nitronium. Gas chromatography-mass spectrometry of the products showed that the nitration rate scaled with the catalyst’s acidity and specific surface area. Homogenizing NaNO3 with the catalyst by additional milling prior to reaction with toluene led to a rapid, nearly complete nitration. Distribution of nitrate over the surface of catalyst is likely rate limiting when toluene is mechanochemically nitrated without the preliminary milling step. The observed for varied reactant ratios trends in yield and isomer ratios suggest that nitronium participates in the nitration while localized on the active sites of the catalyst. Excess of toluene blocks acid sites, inhibiting the formation of nitronium and impeding the nitration.

Badania reakcji nitrowania toluenu za pomocą mieszaniny kwas azotowy(V)/dichlorometan

This work has studied the effects on the nitration of toluene by 100% nitric(V) acid and a nitric(V) acid/dichloromethane mixture. The results show that the amount of meta-nitrotoluene decreases with decreases in reaction temperature. From 25 °C to –10 °C the amount of metanitrotoluene was less than for nitrating toluene by a nitric(V)acid/dichloromethane mixture than for nitration by 100% nitric(V) acid. Furthermore, from –20 °C to –30 °C results were similar with 2.6% of meta-nitrotoluene in the reaction products. An excess of nitric(V) acid in the nitration of toluene by the nitric(V) acid/dichloromethane mixture than in nitration by 100% nitric(V) acid. Nitration by the nitric(V) acid/dichloromethane mixture is less exothermic and easier to control than nitration by 100% nitric(V) acid.