Conversion Of Aniline Research Articles

Methyl N-phenyl carbamate synthesis over Zn/Al/Ce mixed oxide derived from hydrotalcite-like precursors.

Methyl N-phenyl carbamate (MPC) is an important intermediate for the green synthesis of methylene diphenyl diisocyanate (MDI) as well as many other important products. In the present work, Zn/Al/Ce mixed oxides derived from hydrotalcite-like precursors were employed as effective and recoverable heterogeneous catalyst for MPC synthesis via DMC aminolysis. Zn/Al/Ce hydrotalcite-like precursors prepared via coprecipitation method and the resulting catalysts were characterized by means of XRD, BET, SEM and XPS. Strong interactions within the Zn/Al/Ce mixed oxides were observed via the addition of appropriate amount of cerium. The mixed oxides containing 2.5% cerium showed high DMC aminolysis activity giving aniline conversion of 95.8%, MPC selectivity of 81.6% and MPC yield of 78.2%. Moreover, as a heterogeneous catalyst, it also exhibited superiorities of easy recovery and recyclable stability for MPC synthesis.

Synthesis of pyrroles catalyzed by MIL-53(Al) via Paal-Knorr reaction under mild condition

Metal-organic framework MIL-53(Al) was synthesized by a solvothermal method using aluminium nitrate as the aluminium source and 1,4- benzenedicarboxylic acid (H2BDC) as the organic ligand. The structure of MIL-53(Al) was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The catalytic activity and recyclability of MIL-53(Al) catalyst were evaluated based on the Paal-Knorr reaction between aniline and acetonylacetone. The reaction conditions were optimized and the results showed that the MIL-53(Al) catalyst exhibited good catalytic activity and recyclability based on the PaalKnorr reaction. With the molar ratio of MIL-53(Al) catalyst of 10 mol %, the molar ratio of aniline and acetonylacetone of 1:1.2, and without solvents, the conversion of aniline could reach 100 % and the selectivity of 2,5-dimethyl-1-phenyl-1H-pyrrole has high yield (95-100 %) after 2 hours by ultrasound activation. The MIL-53(Al) catalyst can be reused five times without significant degradation in the catalytic activity.

Room temperature selective conversion of aniline to azoxybenzene over an amorphous niobium oxyhydroxide supported on δ-FeOOH

Abstract In this work, catalysts for the oxidation of aniline into azoxybenzene were prepared by combining δ-FeOOH nanoparticles with 0, 2.5, 5, and 10 wt.% niobium oxyhydroxides by a simple co-precipitation method. The niobium oxyhydroxide actively changed the chemical and textural properties of δ-FeOOH, as verified by XRD, Mossbauer spectroscopy, N2 adsorption-desorption measurements, and TEM images. Therefore, the catalytic performance of δ-FeOOH to convert aniline into azoxybenzene in the presence of hydrogen peroxide was significantly improved. The catalytic activity and selectivity changed with the Nb content in the composite. The effect of different reaction parameters like solvent type, H2O2 volume, and reaction time has been studied in detail. The catalyst with 10 wt.% Nb was the most efficient among the evaluated catalysts, showing 100% conversion of aniline with 80.2% selectivity to azoxybenzene when propanol was used as solvent at 25 °C. Moreover, the catalyst 10 wt.% Nb exhibited good stability and could be reused for various cycles without significant loss of catalytic activity.

Tube-in-tube hollow fiber catalytic membrane microreactor for the hydrogenation of nitrobenzene

The miniaturization of membrane reactors aims to improve the mass transfer efficiency. A tube-in-tube hollow fiber catalytic membrane microreactor that contains dual characteristics of a catalytic membrane reactor and a microreactor was developed in this study. For a gas-liquid-solid (G-L-S) reactor, the immobilization of solid catalysts on a hollow fiber membrane (HFM) via layer-by-layer (LBL) self-assembly enables the model reaction of nitrobenzene hydrogenation to occur. The unique structure of the novel catalytic membrane microreactor separates the gas and liquid reactants and shortens the transfer distance. The experimental results showed that the nitrobenzene conversion was high during 30 h of continuous operation. The effects of the flow rates and inlet nitrobenzene concentration were also investigated. At a given gas flow rate, the nitrobenzene conversion and concentration of the product aniline decreased with increasing the liquid flow rate. Meanwhile, at a given liquid flow rate, an increase in the gas flow rate led to an increase in the pressure of the gas phase. Sufficient hydrogen promoted the reaction, increasing the nitrobenzene conversion and aniline concentration. In addition, the inlet nitrobenzene concentration affected the conversion. Higher concentration not only enhanced the reaction rate but also caused catalyst poisoning. Based on these results, the newly designed catalytic membrane microreactor is feasible to improve the performance towards multiphase reaction.

Metal modified fluorapatite (metal = Co, Ni, Cu, Zn): a new type of efficient catalyst for methyl N-phenyl carbamate direct synthesis from urea, methanol and aniline

The application of metal modified fluorapatite (metal-FAP, MCa9(PO4)6F2, M = Ca, Co, Ni, Cu, Zn) as highly efficient catalysts for the synthesis of an important intermediate methyl N-phenyl carbamate (MPC) for non-phosgene isocyanate production, from urea, methanol and aniline is reported firstly. The catalysts metal-FAP powders were synthesized by co-precipitation method and their properties were identified by ICP-AES, XRD, BET, TEM, EDS and NH3-TPD. Zn modified fluorapatite (ZnCa9(PO4)6F2, ZnFAP) with the strongest acidity among the metal-FAP (metal = Ca, Co, Ni, Cu, Zn) catalysts exhibited the highest catalytic activity to MPC formation. The effects of reaction temperature, time, molar ratio of raw materials, dosage of catalyst and reusability of the catalyst on the process were investigated. The optimal reaction parameters were determined as follows: aniline 20 mmol, the molar ratio urea/aniline 5:1, the molar ratio of methanol to aniline 20:1, ZnFAP 8.0 mmol, 6 h, 180 °C, with 94.4% aniline conversion and 75.8% selectivity to methyl N-phenyl carbamate. ZnFAP catalyst showed little catalytic activity loss after five times repeated use. The reaction mechanism is proposed and discussed.

Aluminosilicates with different pores structure in the synthesis of 2,2,4-trimethyl-1,2-dihydroquinoline and N-phenyl-2-propanimine

Physicochemical characteristics of microporous zeolites of various structural type (FAU, BEA, MTW), micro-meso-macroporous zeolite (H-Ymmm), and mesoporous aluminosilicate (ASM) were studied. Their catalytic activity in the reaction of aniline with acetone was examined. It was found that 2,2,4-trimethyl-1,2-dihydroquinoline was the main reaction product on the catalysts H-Ymmm and ASM (selectivity up to 68% at 100% conversion of aniline), while the reaction on zeolites with microporous structure mainly gave N-phenyl-2-propanimine (selectivity up to 91%).

Low temperature liquid phase catalytic oxidation of aniline promoted by niobium pentoxide micro and nanoparticles

A microwave-assisted hydrothermal method was employed to synthesis Nb2O5 (niobium pentoxide) nanoparticles and the effects of synthesis conditions on the physical-chemical properties were evaluated. The catalytic activity of the prepared samples in the liquid phase oxidation of aniline with aqueous hydrogen peroxide as oxidizing agent was also studied. The nanoparticles showed hexagonal structure and rounded shape covered by nanoneedles. The results evidenced high catalytic activity with total conversion of aniline at ambient condition. Aniline conversion and product selectivities depended on the experimental parameters, particularly the oxidizing agent concentration, the nature of the solvent, type of the catalyst and reaction time.

Preparation and characterization of H4SiW12O40@MIL-100(Fe) and its catalytic performance for synthesis of 4,4′-MDA

Abstract The catalytic performance of commonly used heteropolyacids (H 3 PW 12 O 40 , H 4 SiW 12 O 40 and H 3 PMo 12 O 40 ) for the synthesis of 4,4′-methylenedianiline (4,4′-MDA) from aniline and formaldehyde was evaluated and the result showed that H 4 SiW 12 O 40 with moderate acid strength exhibited the best catalytic performance. Then H 4 SiW 12 O 40 @MIL-100(Fe) was prepared by encapsulating H 4 SiW 12 O 40 within the pores of MIL-100(Fe) to facilitate its recovery and reuse. The prepared H 4 SiW 12 O 40 @MIL-100(Fe) was characterized by means of FT-IR, N 2 adsorption–desorption, XRD, TG and then the catalytic performance was evaluated. The result showed that H 4 SiW 12 O 40 was highly dispersed in the pores of MIL-100(Fe), and both the Keggin structure of H 4 SiW 12 O 40 and the crystal skeleton structure of MIL-100(Fe) could be effectively preserved. Furthermore, H 4 SiW 12 O 40 @MIL-100(Fe) showed excellent catalytic performance under the following reaction conditions: a molar ratio of aniline to formaldehyde = 5, a mass ratio of catalyst to formaldehyde = 1.2, a reaction temperature of 120 °C and a reaction time of 6 h. Under the above reaction conditions, the conversion of aniline was 41.1%, and the yield and selectivity of 4,4′-MDA were 81.6% and 79.2%, respectively. Unfortunately, an appreciable loss in the catalytic activity of the recovered H 4 SiW 12 O 40 @MIL-100(Fe) was observed because of the blocking of the pores and the change of the acidity resulted from the adsorption of alkaline organics such as aniline and 4,4′-MDA. The adsorbed alkaline organics could be cleaned up when the recovered catalyst was washed by methanol and DMF. Then the catalyst was effectively reused up to three cycles without much loss in its activity.

Copper promoted desulfurization towards the synthesis of isothiocyanates

The cheap, readily available and air stable catalyst was used as the desulfurization agent for the conversion of aniline to isothiocyanates in one pot two step reaction under mild reaction conditions.

An efficient methodology for the synthesis of thioureas from amine mediated by a cobalt source

The cheap, readily available and air stable cobalt catalyst was used as the desulfurization agent for the conversion of aniline to thioureas in one pot three step reaction under mild reaction conditions. The reactions are rapid and facile and accomplished at room temperature.

Pd nanoparticles supported on Fe3O4@C: An effective heterogeneous catalyst for the transfer hydrogenation of nitro compounds into amines

Catalytic reduction of nitro compounds to the amines is of high importance in modern synthetic chemistry. In this study, an efficient method was developed for the transfer hydrogenation of nitro compounds over a magnetic Pd catalyst by the use of NaBH4 as the hydrogen donor. Full nitrobenzene conversion and high selectivity (>99%) of aniline were produced after 1 h at 60 °C in ethanol. The reductions are successfully carried out in presence of a wide variety of other reducible functional groups in the molecule, except halogen and vinyl substitute nitrobenzene. Kinetic studies indicated the active energy for the transfer hydrogenation of nitrobenzene was 20.93 KJ mol−1. The transfer hydrogenation of nitrobenzene was confirmed to proceed via azobenzene as the intermediate. More importantly, the catalyst was very stable without the loss of its catalytic activity.

Polymerization amplified SPR−DNA assay on noncovalently functionalized graphene

A highly efficient surface plasmon resonance (SPR)-based DNA assay was developed, by employing noncovalently functionalized graphene nanosheets as a substrate, and enzymatic catalysis-induced polymerization as mass relay. The objective of this strategy was manifold: first of all, to sensitize the overall SPR output by in situ optimized electrogeneration of graphene thin-film, which was characterized by atomic force microscopic topography; secondly, to regulate the self-assembly and orientation of biotinylated capture probes on nickel-chelated nitrilotriacetic acid (NTA) scaffolds, that anchored onto graphene-supported pyrenyl derivatives; and lastly, to synergize the signal amplification via real-time conversion of the additive aniline into polyaniline precipitation by horseradish peroxidase-tagged reporters. With this setup, a precise and replicable DNA sensing platform for specific targets was achieved with a detection limit down to femtomolar, thus demonstrating a beneficial exploration and exploitation of two-dimensional nanomaterials as unique SPR infrastructure. The possibility of such ″bottom-up″ architecture mounted with ″top-down″ weight reactor would be most likely extensible and adaptable to protein determinations.

Reaction mechanisms of carbon dioxide, ethylene oxide and amines catalyzed by ionic liquids BmimBr and BmimOAc: a DFT study

The mechanisms of the one-pot conversion of carbon dioxide, ethylene oxide, and aniline to 3-phenyl-2-oxazolidionone catalyzed by the binary ionic liquids of BmimBr and BmimOAc were explored using the DFT methods. The complex reaction above comprises of two parallel reactions and a subsequent cascade reaction. DFT calculations on reaction pathways and energy profiles reveal that the electrostatic and hydrogen-bond effects of BmimBr play a crucial role in the parallel reactions for the generation of ethylene carbonate and 2-phenylamino-ethanol. Further, the subsequent cascade reaction to generate 3-phenyl-2-oxazolidinone catalyzed by BmimOAc follows a stepwise mechanism, which is more favorable than the concerted mechanism governed by BmimBr. In addition, BmimBr can accelerate the side reaction of aniline and ethylene oxide to yield a mixture of oligomers, which accords with the experimental observation. This theoretical work provides a deep insight into the catalytic roles of binary ionic liquids and also inspires us to design high efficient catalysts for the conversion of carbon dioxide further.

Dimeric assemblies of lanthanide-stabilised dilacunary Keggin tungstogermanates: A new class of catalysts for the selective oxidation of aniline

In this work we demonstrate the efficiency of some dimeric [Ln4(H2O)6(β-GeW10O38)2]12− anions composed of lanthanide-stabilised dilacunary Keggin tungstogermanate fragments (ββ-Ln4, Ln=Dy, Ho, Er, Tm) as heterogeneous catalysts for the organic phase oxidation of aniline with hydrogen peroxide. The results obtained evidence total conversion of aniline at room temperature, as well as full selectivity towards nitrosobenzene, and the catalysts are able to retain both their activity and selectivity after several runs. Peroxopolyoxometalate intermediaries have been identified as the catalytically active species during the aniline-to-nitrosobenzene oxidation process.

Catalytic wet peroxide oxidation of aniline in wastewater using copper modified SBA-15 as catalyst

SBA-15 mesoporous molecular sieves modified with copper (Cu-SBA-15) were prepared by pH-adjusting hydrothermal method and characterized by X-ray diffraction, BET, transmission electron microscopy, UV–Vis and 29Si MAS NMR. The pH of the synthesis gel has a significant effect on the amount and the dispersion of copper on SBA-15. The Cu-SBA-15(4.5) (where 4.5 denotes the pH value of the synthesis gel) modified with highly dispersed copper was used as catalyst for the oxidation of aniline by H2O2. The Cu-SBA-15(4.5) shows a higher catalytic activity compared to CuO on the surface of SBA-15. The influences of reaction conditions, such as initial pH of the aqueous solutions, temperature, as well as the dosages of H2O2 and catalyst were investigated. Under weakly alkaline aqueous solution conditions, the aniline conversion, the H2O2 decomposition and the total organic carbon (TOC) removal could be increased significantly compared to the acid conditions. The percentage of leaching Cu2+ could be decreased from 45.0% to 3.66% when the initial pH of solution was increased from 5 to 10. The TOC removal could be enhanced with the increases of temperature, H2O2 and catalyst dosage, but the aniline conversion and H2O2 decomposition change slightly with further increasing dosage of catalyst and H2O2. At 343 K and pH 8.0, 100% aniline conversion and 66.9% TOC removal can be achieved under the conditions of 1.0 g/L catalyst and 0.05 mol/L H2O2 after 180 min. Although copper might be slightly leached from catalyst, the homogeneous Cu2+ contribution to the whole catalytic activity is unimportant, and the highly dispersed copper on SBA-15 plays a dominant role.

Synthesis of 4,4′-Methylenedianiline Catalyzed by SO3H-Functionalized Ionic Liquids

4,4′-Methylenedianiline (4,4′-MDA) is a key intermediate for the production of polyurethanes. A series of SO3H-functionalized ionic liquids (SFILs) were synthesized, and their catalytic performance was evaluated in the condensation reaction of aniline with formaldehyde for the synthesis of 4,4′-MDA. The result showed that SFILs had excellent catalytic activity, and their catalytic activity was consistent with their acid strength. [HSO3-bmim]CF3SO3 (SImTf) with the highest acid strength showed the best catalytic activity. Then, the influence of reaction conditions on the condensation reaction of aniline with formaldehyde to 4,4′-MDA was investigated using SImTf as the catalyst, and suitable reaction conditions were obtained as follows: molar ratio of aniline to formaldehyde = 5, mass ratio of SImTf to formaldehyde = 3.5, reaction temperature of 80 °C, and reaction time of 8 h. Under the above reaction conditions, the conversion of aniline was 36.3%, and the yield and selectivity of 4,4′-MDA were 79.4% and ...

Cerium dioxide catalyzed synthesis of methyl N-phenylcarbamate from carbon dioxide, aniline and methanol in the presence of n-butyllithium

Direct synthesis of methyl N-phenylcarbamate (MPC) from carbon dioxide (CO2), aniline and methanol catalyzed by cerium dioxide (CeO2) in the presence of n-butyllithium (BuLi) was developed. The catalytic activity of CeO2 was significantly improved by the addition of BuLi. The conversion of aniline and the yield of MPC were dependent on the amount of CeO2 and BuLi, reaction conditions including the pressure of CO2, reaction time and temperature, and 9.4% yield of MPC was obtained under the optimized conditions. The formation pathway of MPC was also investigated in detail by varying reactants based on previously reported investigations, and phenyl isocyanate (PI) was believed to be the intermediate for the synthesis of MPC. A possible reaction pathway for the direct synthesis of MPC from CO2, aniline and methanol was proposed.

The one-pot synthesis of methylene diphenyl-4,4′-dicarbamate

Methylene diphenyl-4,4′-dicarbamate (MDC) is an intermediate for the preparation of methylene diphenyl diisocyanate. This paper reports the one-pot synthesis of MDC using aniline, dimethyl carbonate, and formalin as raw materials. Phenyl N-methyl carbamate (MPC) synthesis was carried out in a batch reactor using Zn(OAc)2 as the catalyst, following which, without any separation, an Hβ catalyst and formalin were added to continue to MPC condensation to give MDC. It was found that there were interactions between the MPC synthesis and MPC condensation, such that the presence of aniline could inhibits MPC condensation. Zn(OAc)2 was also found to adsorb on the Hβ surface to form Si–O–Zn bonds during the condensation, decreasing the quantity of strong acid sites on the Hβ and reducing the catalytic performance. Under the optimal conditions for the one-pot synthesis of MDC, aniline conversion was 100% and the MDC yield was 73.9% (based on HCHO). The deactivated catalyst could be easily regenerated by treatment with acetic acid. The filter cake was dried and calcined to obtain regenerated Hβ and the filtrate was dried by vacuum rotary evaporation to obtain Zn(OAc)2. No significant loss in catalytic activity was observed for the regenerated catalyst.

Solid base catalyzed highly efficient N-alkylation of amines with alcohols in a solvent-free system

Different from any other catalytic systems containing transition metals and additives, sodium hydroxide itself was found to be a unique and effective catalyst for the solvent-free synthesis of the secondary amines via the N-alkylation of amines with alcohols. For the reaction of aniline with benzyl alcohol, 99.6mol% conversion of aniline and 99.5% selectivity of the product were achieved under optimal conditions. Also, high conversion and selectivity could be acquired for the N-alkylations of various amines with alcohols, implying the universality of this methodology. Mechanistic studies revealed that this novel reaction most possibly proceeds with a base-catalyzed mechanism.

Catalytic wet air oxidation of phenol, nitrobenzene and aniline over the multi-walled carbon nanotubes (MWCNTs) as catalysts

Wet air oxidation (WAO) is one of effective technologies to eliminate hazardous, toxic and highly concentrated organic compounds in the wastewater. In the paper, multi-walled carbon nanotubes (MWCNTs), functionalized by O3, were used as catalysts in the absence of any metals to investigate the catalytic activity in the catalytic wet air oxidation (CWAO) of phenol, nitrobenzene (NB) and aniline at the mild operating conditions (reaction temperature of 155°C and total pressure of 2.5 MPa) in a batch reactor. The MWCNTs were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), gas adsorption measurements (BET), fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The functionalized MWCNTs showed good catalytic performance. In the CWAO of phenol over the functionalized MWCNTs, total phenol removal was obtained after 90 min run, and the reaction apparent activation energy was ca. 40 kJ·mol−1. The NB was not removed in the CWAO of single NB, while ca. 97% NB removal was obtained and 40% NB removal was attributed to the catalytic activity after 180 min run in the presence of phenol. Ca. 49% aniline conversion was achieved after 120 min run in the CWAO of aniline.