Yield Of Aniline Research Articles

Halogenation of Anilines: Formation of Haloacetonitriles and Large-Molecule Disinfection Byproducts.

Aniline-related structures are common in anthropogenic chemicals, such as pharmaceuticals and pesticides. Compared with the widely studied phenolic compounds, anilines have received far less assessment of their disinfection byproduct (DBP) formation potential, even though anilines and phenols likely exhibit similar reactivities on their respective aromatic rings. In this study, a suite of 19 aniline compounds with varying N- and ring-substitutions were evaluated for their formation potentials of haloacetonitriles and trihalomethanes under free chlorination and free bromination conditions. Eight of the aniline compounds formed dichloroacetonitrile at yields above 0.50%; the highest yields were observed for 4-nitroaniline, 3-chloroaniline, and 4-(methylsulfonyl)aniline (1.6-2.3%). Free bromination generally resulted in greater haloacetonitrile yields with the highest yield observed for 2-ethylaniline (6.5%). The trihalomethane yields of anilines correlated with their haloacetonitrile yields. Product analysis of aniline chlorination by liquid chromatography-high-resolution mass spectrometry revealed several large-molecule DBPs, including chloroanilines, (chloro)hydroxyanilines, (chloro)benzoquinone imines, and ring-cleavage products. The product time profiles suggested that the reaction pathways include initial ring chlorination and hydroxylation, followed by the formation of benzoquinone imines that eventually led to ring cleavage. This work revealed the potential of aniline-related moieties in micropollutants as potent precursors to haloacetonitriles and other emerging large-molecule DBPs with the expected toxicity.

Synthesis and characterization of Zn-In-S composites for photocatalytic benzyl alcohol oxidation and nitrobenzene reduction

Photocatalytic transformation of organics is a promising alternative to conventional synthetic methodologies. ZnIn2S4 is active in photocatalytic redox reactions, but its performance is hindered by fast charge carrier recombination, and optimizing its properties through synthesis or modification is complicated. Herein, Zn-In-S based composites were prepared via a facile solvothermal method by varying the ratio of sulfide precursor (TAA) with a fixed Zn/ In molar ratio of 1: 2. The phase composition of the obtained materials depends on the amount of TAA. At lower ratios, composites consisting of crystalline In(OH)3 and unknown ZnxInySz phase were formed. Pure-phase ZnIn2S4 was obtained when the feed molar ratio of zinc and TAA was 1: 6 or higher. The photocatalytic oxidation of benzyl alcohol (BA) and reduction of nitrobenzene (NB) in a coupled system were applied to evaluate the activity of Zn-In-S-based composites. Under visible light irradiation, the ZnxInySz/ In(OH)3 composite (ZIS14) synthesized with a molar ratio of Zn to TAA of 1: 4 exhibited boosted and optimal performance compared to the bare ZnIn2S4 and other samples. After 5 hours of irradiation, the BA conversion and benzaldehyde (BAD) yield were 57 % and 55 %, respectively, and the NB conversion and aniline (AN) yield were 70 % and 35 %, individually, outperforming previous studies under similar experimental conditions. This work not only elucidates the photoredox process of BA and NB in one system, but also has significant implications for understanding the complex hydro/solvothermal processes involved in the fabrication of multicomponent sulfides.

Highly active iron oxide@NC catalyst derived from the iron acetate/polyacrylonitrile threads: Driving nitroarene conversion to value‐added amines

AbstractChemoselective reduction of nitroarenes to corresponding arylamines is a significant reaction in the chemical industry. However, in the presence of other reducible groups, including halogenated nitrobenzene, nitrobiphenyl, and nitroquinoline in the same molecule of nitroaromatics, the control of chemoselectivity remains challenging. Here, a facile fabrication of a heterogeneous iron‐based catalyst is reported as a potential alternative to precious metal catalysts for the chemoselective reduction of nitroarenes. The pyrolysis of iron acetate/polyacrylonitrile (PAN) template under an inert atmosphere furnishes active Fe3O4 nanoparticles (NPs) encapsulated in nitrogen‐doped (N‐doped) carbon layers, which can provide more catalytic active sites (Fe3O4/PAN@800). Notably, non‐precious iron oxide NPs supported on N‐doped carbon support prevent aggregation, thereby enhancing the catalytic activity. The sustainable and reusable Fe3O4/PAN@800 catalyst, having only 0.8% metal content as demonstrated by x‐ray photoelectron spectroscopy, delivers excellent yields of corresponding amines from differently functionalized nitroarenes. Hydrogenation of a series of structurally functionalized nitroarenes produced excellent yields of anilines, which serve as building blocks and intermediates for fine and bulk chemicals. Hydrogenation of 2‐chloro‐3‐nitropyridine, 2‐nitro‐1,1′‐biphenyl, ortho‐nitroaniline, and 4‐aminophenyl acrylonitrile yielded respective anilines up to 99%. The active sites of Fe3O4 have magnetic performance, hence, the catalyst can be easily recovered using a magnet and reused for at least five cycles without significant loss of catalytic activity. Therefore, the easily prepared, cost‐effective, and reusable Fe3O4/PAN@800 catalyst presented in this study shows potential for applications in the selective reduction of aromatic nitro compounds. Consequently, this study potentially establishes a guideline for the facile preparation of abundant transition‐non‐noble metal‐based reusable supported catalysts for various applications in the chemical industry.

Superhydrophobic biochars as catalysts for efficient hydrogen transfer in N-heterocycles and nitrobenzene reactions

The heteroatom-doped carbon nanomaterials can be the active catalysts in hydrogen transfer reactions, however, carbon-catalyzed hydrogen transfer processes in the absence of additives and cocatalysts have been rarely described. Herein, functional biochar catalysts (FBCs) were successfully fabricated from wheat straw by a simple scalable two-step strategy via reconstructing the catalytic active sites in carbon precursors and subsequently controlled carbonization. The characterization of FBCs was discussed with regard to morphologic structures, chemical constitutions and performance, revealing that the high hydrophobicity is beneficial for obtaining high activity. Wherein the optimized FBC-850 catalyst exhibited high activity and durability toward the reaction of N-heterocycles and nitrobenzene in the aqueous systems due to the synergistic effects that were attributed to the external superhydrophobicity, internal capillary repulsion and hydrogen transfer property, eliminating the need for additional co-catalysts or additives. In the model reaction, the yields of quinoline and aniline were respectively achieved at 92% and 90%. Furthermore, the encapsulated quinone units as the active sites in FBC-850 formed the bipyramidal structure, enabling the hydrogen transfer process through a cyclical hydrogen exchange, which was proved from kinetic studies combined with spectral characterization and theoretical calculation. In addition, a possible reaction mechanism was proposed based on the observation of key intermediates and DFT calculations, also providing a rationale for the existing active site structures.

Development of Magnetizable, Nickel-Ferrite-Decorated Carbon Nanocomposites as Hydrogenation Catalyst for Aniline Synthesis.

Catalysts with magnetic properties can be easily recovered from the reaction medium without loss by using a magnetic field, which highly improves their applicability. To design such systems, we have successfully combined the magnetic properties of nickel ferrite nanoparticles with the positive properties of carbon-based catalyst supports. Amine-functionalized NiFe2O4 nanoparticles were deposited on the surfaces of nitrogen-doped bamboo-like carbon nanotubes (N-BCNT) and carbon nanolayers (CNL) by using a coprecipitation process. The magnetizable catalyst supports were decorated by Pd nanoparticles, and their catalytic activity was tested through the hydrogenation of nitrobenzene (NB). By using the prepared catalysts, high nitrobenzene conversion (100% for 120 min at 333 K) and a high aniline yield (99%) were achieved. The Pd/NiFe2O4-CNL catalyst was remarkable in terms of stability during the reuse tests due to the strong interaction formed between the catalytically active metal and its support (the activity was retained during four cycles of 120 min at 333 K). Furthermore, despite the long-lasting mechanical stress, no significant palladium loss (only 0.08 wt%) was detected.

CuII-Hfur–imidazole] compounds as precursors of efficient hydrogenation and reductive alkylation catalysts in flow systems

The reaction of copper(II) acetate with furoic acids (2Hfur / 3Hfur) and imidazole (Im) in methanol resulted in mononuclear complexes [Cu(fur)2(Im)2(H2O)]·L (fur- = 2fur- (1, 2), 3fur- (3); L = MeCN (1)) whose structures were determined by direct single crystal X-ray analysis. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al2O3 obtained by chemical reduction of 1, 2 and 3 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of mono- and dihydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD). The catalytic activity tests show a high selectivity (97 %) of the catalyst obtained from an ethanolic solution of complex 1 in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with an excess of hydrogen, whereas the catalyst obtained from an aqueous solution of complex 1 showed 98 % total hydrogenation product (THDCPD) selectivity. The catalysts based on all the complexes 1–3 were successfully used in reactions of nitrobenzene (NB) reduction to aniline (AN) and in the reductive alkylation of nitrobenzene with isobutanol (i-BAN) 100 % yields of aniline and N-isobutylaniline were obtained at LHSV 0.16 h−1.

Amine Functionalization Leads to Enhanced Performance for Nickel- and Cobalt-Ferrite-Supported Palladium Catalysts in Nitrobenzene Hydrogenation.

Easy preparation, good yield and easy recovery are the key challenges in the development of industrial catalysts. To meet all these three criteria, we have prepared intelligent, magnetizable NiFe2O4- and CoFe2O4-supported palladium catalysts that can be easily and completely recovered from the reaction medium by magnetic separation. The fast and facile preparation was achieved by a solvothermal method followed by sonochemical-assisted decomposition of the palladium nanoparticles onto the surface of the magnetic nanoparticles. The metal-support interaction was enhanced by amine functionalization of the supports using monoethanolamine. The performance and stability of the non-functionalized and amine-functionalized NiFe2O4- and CoFe2O4-supported palladium catalysts were compared in the industrially important nitrobenzene hydrogenation reaction. All catalysts showed high catalytic activity during aniline synthesis; complete nitrobenzene conversion and high aniline yield (above 97 n/n%) and selectivity (above 98 n/n%) were achieved. However, during reuse tests, the activity of the non-functionalized catalysts decreased, as the palladium was leached from the surface of the support. On the other hand, in the case of their amine-functionalized counterparts, there was no decrease in activity, and a non-significant decrease in palladium content could be measured. Based on these results, it can be concluded that amine functionalization of transition metal ferrites may result in more effective catalysts due to the enhanced metal-carrier interaction between the support and the precious metal.

Green synthesis of metronidazole-based stabilized silica-coated Fe3O4 as a novel modified magnetic catalyst for the green solvent-free halogenation of aromatic compounds

Herein, Fe3O4 nanoparticle was first synthesized, then its surface was modified with tetraethyl orthosilicate, and finally, metronidazole was covalently fixed on its surface to synthesize Fe3O4@SiO2@(CH2)3-Metronidazole (FSCM). Synthesized materials were characterized. The catalytic activity of MNPs Fe3O4@SiO2@(CH2)3-metronidazole was studied by the aromatic bromination/iodination of aromatics under solvent-free conditions. Bromination/iodination products were characterized using 1H NMR and 13C NMR. The conversion yield of aniline to 4-bromoaniline using 0, 100, 200, 300, 400, and 500 mg of Fe3O4@SiO2@(CH2)3-Metronidazole at 25 min and 25 °C were trace, 76, 85, 96, 89, and 79 %, respectively. The catalyst showed high catalytic performance with excellent yields at short reaction times. The results showed that Fe3O4@SiO2@(CH2)3-Metronidazole can be used as a heterogeneous catalyst after 5 cycles without significant loss of catalytic activity (89%) for the bromination and iodination of aromatic hydrocarbons with KBr/KI.

Green halogenation of aromatic compounds using environmentally friendly synthesized rod-like metal-organic framework (MIL-88A) catalyst

Metal-organic frameworks (MOFs) have been extensively investigated as catalysts to synthesis of various chemical and eliminate toxic pollutants in water. Herein, MOF was used as an efficient catalyst for the halogenation of aromatic materials (aniline, b-naphthol, and naphthalene). The rod-like MIL-88A as an iron-based MOF was synthesized using Fe3+ with fumaric acid in water as a green solvent. The synthesized catalyst was characterized by FT-IR, XRD, SEM, and Raman. The rod-like MIL-88A is evaluated as the heterogeneous catalyst to activate KBr/I for the halogenation of aromatic compounds. 1HNMR and 13CNMR were used to characterize the halogenated aromatic materials. Halogenation of aromatic rings has been studied using potassium bromide (KBr) and potassium iodide (KI) as brominating and iodinating agents in the presence of rod-like MIL-88A as oxidant under solvent-free reaction (grinding) conditions. The halogenation yield of aromatics materials was 80–99%. The conversion yield of aniline to 4‑bromo aniline using 0, 10, 20, 30, 40, and 50 mg of rod-like MIL-88A at 25 min and room temperature (25 ºC) were 0%, 76%, 85%, 90%, 95%, and 88%, respectively. In addition, the conversion yield of B-naphthol to 1-Bromo-2-naphthol using a green catalyst was 97%. Also, the conversion yield of Naphthalene to 1-Bromonaphthalene using a rod-like catalyst. In most cases, mono-halogen derivatives were obtained in good yield without the aid of strong acids. In addition, the rod-like MIL-88A catalyst shows excellent stability and can be reused after proper washing treatments. It could be concluded that green synthesized rod-like MIL-88A could be used as an environmentally friendly catalyst for the halogenation of aromatics via grinding as a solvent-free reaction at room temperature.

Synthesis of Mesoporous Silica-Supported NiCo Bimetallic Nanocatalysts and Their Enhanced Catalytic Hydrogenation Performance.

In this work, mesoporous silica SBA-16-supported NiCo bimetallic nanocatalysts were synthesized by coimpregnation of Ni and Co precursors followed by calcination and reduction, and various characterization techniques confirm the formation of NiCo bimetallic nanostructures in the catalysts. The synthesized NiCo/SBA-16 shows enhanced catalytic performance for hydrogenation of a series of nitroaromatics. Under the reaction conditions of 80 °C and 1.0 MPa of H2, the yields of aniline for nitrobenzene hydrogenation over NiCo0.3/SBA-16 can reach more than 99% at 2.0 h. The enhanced catalytic performance can be ascribed to the formation of NiCo bimetallic nanostructures, where the synergistic effect between Ni and Co improves their catalytic activities for hydrogenation of nitroaromatics.

Pd/Co Catalyst with High Pd Atom Utilization Efficiency for Nitrobenzene Hydrogenation at Room Temperature: Experimental and DFT Studies.

Enhancing catalytic performance as well as reducing catalyst cost are the eternal pursuit for the catalysis community. Herein, a simple and effective palladium-doped cobalt (Pd/Co) catalyst with high Pd atom utilization efficiency was synthesized via galvanic replacement reaction for the selective hydrogenation of nitrobenzene with H2 at room temperature, delivering >99 % yield of aniline with up to 158 times higher catalytic activity than commercial palladium powder. Detailed characterizations and DFT calculations revealed that Co-Pd interaction leads to a decrease in electron density of Pd and the distance between Pd atoms that results in the enhanced catalytic performance. Further experiments indicated that the Pd/Co catalyst serves as a highly efficient, selective, and recyclable catalyst for a range of nitroarene substrates. This work might provide a green and sustainable methodology to design and synthesize highly active catalysts with high utilization efficiency of the noble metals in fundamental and applied research.

A Mechanistic Study of HZSM-5-Catalyzed Guaiacol Amination Using Photoionization Time-of-Flight Mass Spectrometry

Thermal-catalytic conversion and amination (TCC-A) of lignin and lignin derivates over zeolites is a promising and renewable method to produce aromatic amines, but suffers from product diversity. Currently, no unambiguous mechanism could fully describe the chemistry of this process. In this work, the TCC-A mechanism of guaiacol, a typical lignin model compound, with ammonia over HZSM-5 was investigated by online photoionization time-of-flight mass spectrometry combined with density functional theory. Various products including amines, pyrroles, and pyridines were identified. The formation of methylamine and aminophenol below 400 °C via nucleophilic substitutions is attributed to the strong adsorption of ammonia on the active site of HZSM-5. Aniline is the major product above 400 °C coproduced with pyrroles and pyridines. It is suggested that the reactions among radical intermediates (•CH3 and •NH2) and molecules (guaiacol and catechol) lead to poor aniline selectivity via transmethylation, amination, and partial deoxygenation reactions. Hydroamination is proposed as the main formation mechanism of pyrroles and pyridines. The maximum yield of aniline can be achieved at 650 °C owing to the enhancement of amination and deoxygenation and the suppression of transmethylation reactions.

Selective Photocatalytic Reduction of Nitrobenzene to Aniline Using TiO2 Embedded in sPS Aerogel

In recent years, aromatic substances have become the focus of environmental pollution-related concern due to their high stability and mutagenicity. In this regard, researchers have focused their attention on the development of photocatalytic processes to convert nitroaromatic compounds into aniline. In this work, the photocatalytic conversion of nitrobenzene (NB) to aniline (AN) was studied. The photocatalytic reaction was performed using commercial TiO2 (P25) and a photocatalytic aerogel, based on P25 embedded in syndiotactic polystyrene (sPS) aerogel (sPS/P25 aerogel) as photocatalysts. Different alcohols were used as hydrogen sources during the photocatalytic experiments. At the optimized operating conditions (photocatalysts dosage: 0.5 mg/L and 50% (v/v) EtOH%), an AN yield of over 99% was achieved. According to the results, this work could open avenues toward effective production of AN from NB using mild reaction conditions with sPS/P25 aerogel-in view of a possible scale-up of the photocatalytic process.

Au@Pt nanoparticles modified classical CdS nanorods for synergistically utilizing photoexcited charges in coupled selective organic transformations

The photocatalyst construction determines the cost and photoexcited charge kinetics, whereas reaction system design ensures the synergic utilization of photoexcited charges. Herein, a novel Au13@Pt/CdS hybrid nanomaterial was prepared and used for the coupling selective redox system of aromatic alcohols and nitroarenes. The Au13@Pt nanoparticles evenly and tightly anchored on CdS provided abundant e– enrichment sites and wider charge transfer channels and largely improved photocatalytic performance. After 4 h visible-light illumination (λ > 420 nm), the optimal 0.00115 % Au13@Pt/CdS sample displays that the theoretical yields of aniline (AL) and p-methoxybenzaldehyde (p-MBA) are up to 71.5 % and 94.7 % with an impressive selectivity of over 95 %, therefore, parts of the generated AL and p-MBA further formed Schiff base with a 24.3 % yield. Therefore, this work is expected to offer a way to fabricate a dual-functional photocatalyst for selective organic transformations (P-SOTs). A coupling mechanism of simultaneous SO p-MBA and SR of NB in one system was proposed by a series of physical and chemical characterizations combined with in suit DRIFTS and theoretical calculations.

Synergetic roles of pyridinic nitrogen and carbonyl sites in nitrogen-doped carbon for the metal-free transfer hydrogenation reactions

Transition metal catalysts are commonly used for chemical reactions, especially for transfer hydrogenation reactions. From the viewpoints of green and sustainable chemistry, it is highly demanded to develop metal-free catalytic systems. Herein, oxygen-containing groups modified nitrogen-doped carbon catalysts were discovered to be robust for the transfer hydrogenation reaction between nitroarenes and saturated N-heterocyclic compounds, achieving high yields of anilines and unsaturated N-heterocyclic. Control experiments and characterization results indicate that pyridinic N and carbonyl groups are the active sites. Furthermore, DFT calculation indicate that pyridinic N serves the role in the capture of the H atom from the N−H site in N-heterocycles and carbonyl group assists to capture the H atom from the adjacent carbon site. The as-formed H• species are then transferred to nitro groups in nitroarenes to generate anilines. This amalgamation of multiple active sites reveals opportunities for developing modified metal-free carbon catalysts for extensive applications.

Nano-sized Ce-substituted hexagonal Co2–Y ferrite; a valuable catalyst for heterogeneous reduction of toxic nitro-organic pollutants

This paper describes the synthesis of Ce-substituted Y-type barium hexaferrites (Co 2 –Y) {Ba 2 Co 2 Fe 12-x Ce x O 22 (0 ≤ x ≥ 0.30)} through the sol-gel auto-combustion route and its suitability as a heterogeneous catalyst for the reduction of nitroaromatic-compounds, one of the significant water contaminants. The synthesized nanocrystalline hexaferrite powders were characterized using XRD, FTIR, BET, SEM, and VSM. Furthermore, the catalytic functioning of the Co 2 –Y hexaferrite powder was evaluated based on the isolated yield of aniline in the reaction product through column chromatography. It was found that 100 mg pure Co 2 –Y hexaferrite samples could provide complete conversion of nitrobenzene and 65% selectivity of aniline within the water as a solvent and two mmol of reducing agent, hydrated hydrazine (N 2 H 2 .H 2 O), at 100 °C for 12 h. The influence of Ce substitution at the iron site for the aniline selectivity was also investigated in optimized situations. In comparison with pure Co 2 –Y hexaferrite, the catalytic efficiency was considerably enriched in all substituted samples and obtained its extreme performance (73% selectivity of aniline) with Ba 2 Co 2 Fe 11.80 Ce 0.20 O 22 ferrite. The enriched performance was explained with the help of surface chemistry using the XPS & BET analysis for these samples. The as-prepared catalysts were magnetically-separable and recycled for five subsequent trials without any significant losses of catalytic performance. This catalyst may be convenient to be adopted for industrial applications due to its ease of synthesis, extraordinary stability, superior catalytic competence, and cost-effectiveness.

CdS decorated graphitic carbon nitride catalyzed one-pot hydrogenation of nitroaromatics and benzylamine derivatives coupling under visible light irradiation

Oxidation and reduction reactions are essential in the chemical industries to produce various fine chemicals. However, the selectivity of the oxidized and reduced products is still a challenge to chemists and needs to be focused on. In the present work, CdS nanoparticles were decorated at carbon nitride nanosheets via the sol-gel method. The nanocomposite’s activity was investigated for nitroarenes and benzylamines’ reduction and oxidation reactions. The heterojunction improved the charge carriers’ separation, which enhanced the yields of aniline and imines up to 99% with >99% selectivity. The reaction yields with the recovered photocatalyst were relatively similar to the fresh photocatalyst up to five cycles without losing the photocatalytic activity and without leaching the metal content in the reaction mixture. The heterojunction’s physicochemical properties were also determined to investigate. The excellent photocatalytic activity of carbon nitride-based photocatalyst and one-pot two reactions has a broad scope and can elaborate on other organic transformations.

Preparation of Co‐based N‐doped Meso‐microporous Carbon for Hydrogenation of Nitroarenes

AbstractThe development of high‐efficiency and low‐cost heterogeneous catalysts with superior selectivity for the reduction of nitro compounds is desirable. Herein, we prepared Co‐based nitrogen‐doped meso‐microporous carbon (Co/N−C) derived from polyvinylpyrrolidone (PVP)‐coated zeolitic imidazolate framework (ZIF)‐67 as a heterogeneous catalyst for the synthesis of aromatic amines via in‐situ restricted pyrolysis. The structure, morphology, and catalytic activity of Co/N−C were investigated, and the results indicated that Co/N−C‐800 has the combined advantage of the excellent catalytic activity of cobalt nanoparticles and the high mass transfer rate of the N‐doped meso‐microporous carbon framework, achieving superior catalytic ability for the selective hydrogenation of 20 representative nitroaromatic compounds. Co/N−C‐800 was recyclable by simple separation due to the strong magnetism of the Co nanoparticles and exhibited excellent reusability, with 100 % yield of aniline even after six cycles. The catalytic reduction may be attributed to the dissociation of hydrazine to H+/H− via the action of Co/N−C.

Mo2N as a high-efficiency catalyst for transfer hydrogenation of nitrobenzene using stoichiometric hydrazine hydrate

A straightforward and commonly-used approach of direct pyrolysis for the preparation of molybdenum nitride (Mo2N) is conducted via reduction of MoO3 under ammonia atmosphere. The as-synthesized Mo2N catalyst demonstrated high activity for transfer hydrogenation of nitrobenzene, giving a 99% aniline yield at near-room temperature of 30 °C within only 50 min. More significantly, the amount of the hydrogen donor hydrazine monohydrate (N2H4·H2O) can be limited to stoichiometric molar ratio (-NO2: N2H4·H2O = 1: 1.5), preventing the possible generation of hazardous NH3, which is seldom reported in previous protocols. Through various characterizations and control experiments, conclusively, the remarkable catalytic performance of Mo2N catalyst should be credited to the large quantity of Lewis-acidic Mo sites. This research might provide a practical approach to aromatic amines production.

Palladium decorated nickel and zinc ferrite spinel nanoparticles applied in aniline synthesis – development of magnetic catalysts

Aniline is one of the most important chemical in the polyurethane industry and it is produced by the catalytic hydrogenation of nitrobenzene. The development of novel, multifunctional catalysts, which are easily recoverable from the reaction mixture is therefore of paramount importance. Transition metal-containing ferrites decorated with palladium were prepared by using a combination of sonochemical and combustion steps. First of all, magnetic ferrites were produced to be used in catalyst preparation as supports for palladium nanoparticles. On the surface of the ferrite particles palladium nanoparticles were deposited by applying ultrahigh sonication in an alcoholic phase. All in all, three magnetic catalysts, Pd/NiFe2O4, Pd/ZnFe2O4, and Pd/NiZnFeO4 have been created. The catalysts have been tested and their activity have been compared in nitrobenzene hydrogenation to synthesize aniline at four different temperatures, and 20 bar pressure. The most active catalysts were the Pd/ZnFe2O4 and Pd/NiZnFeO4 systems with which aniline yields of 99.2 and 92.8 n/n% were achieved after 3 h of hydrogenation, respectively. In contrast, by applying the Pd/NiFe2O4 catalyst, a significantly lower aniline yield was achieved. It was proved that, due to their magnetic properties, the prepared catalysts are easily removable from the reaction medium by using a magnetic field. Thus, catalysts with excellent properties have been successfully developed and tested in nitrobenzene hydrogenation.