Photocatalytic Reduction Of Nitrobenzene Research Articles

Phenyl-bridged N,N,N'N'-Tetrasubstituted bis(2-amino-5-thiazolyl) diamine: Synthesis and applications in electrochromism and photocatalytic nitrobenzene reduction

A novel type of triphenylamine derivatives, phenyl-bridged N,N,N′,N′-tetrasubstituted bis(2-amino-5-thiazolyl) diamine (4) and its cationic form (5) were synthesized via the Hantzsch reaction. The UV–Vis spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculation results showed that the diamine possesses excellent redox properties and a narrow optical energy gap (∼1.85 eV). As an electrochromic material, compound 4 exhibits a notable color change from colorless to blue. It maintains stable cycling performance for up to 175 cycles, even within a higher voltage range of −2.4 to 2.4 V. In addition, as a catalyst, compound 5 exhibits good substrate compatibility and an aniline conversion rate of up to 89 % during the photocatalytic reduction of nitrobenzene. These results would contribute to understand the synthesis of triphenylamine electrochromic materials and expand their applications in the field of photocatalysis.

Mesoporous PdO–loaded WO3 nanocrystals: A promising photocatalyst for highly efficient photoreduction of nitrobenzene to aniline under visible light

BackgroundNitrobenzene (NTB) conversion to aniline (AN) is a key technology for large-scale industrial chemical production and wastewater treatment. Accordingly, photocatalytic reduction of nitrobenzene has emerged as a green technology to produce aniline. MethodsThis study offers a simple nontoxic surfactant-assisted fabrication of mesoporous tungsten oxide (WO3) nanostructures accompanied by the incorporation of tiny contents (0.5‒2.0 wt%) of palladium oxide (PdO) nanoparticles through impregnation and calcination. Significant findingsPhysicochemical investigations of fabricated heterostructures revealed the formation of mesoporous surfaces and showed the implication of PdO loading on textural and optoelectronic characteristics of WO3. Only 2.0 wt% PdO on the WO3 surface caused a notable decline in the energy bandgap from 2.77 to 1.07 eV, confirming visible light-harvesting improvement. The prepared PdO–loaded WO3 was examined for NTB photoreduction to AN. The optimum content of 1.5 wt% PdO/WO3 (2.0 g L–1) exhibited a complete phototransformation of NTB to AN after only 40 min with excellent reusability and recyclability. The PdO loading significantly facilitated photoinduced charge carriers’ separation and mobility through the construction of Step (S)-scheme heterojunction. This work opens the door for developing semiconductor-based photocatalysis as a green process for effectively converting contaminated water into useful value-added chemicals.

Impact of hole scavengers on photocatalytic reduction of nitrobenzene using cadmium sulfide quantum dots

One key factor that affects the reaction yield and selectivity of nanoparticle-catalyzed photochemical reactions is the type of hole scavengers. In this work, we examine the effect of hole scavengers in photoreduction of nitrobenzene catalyzed by cadmium sulfide quantum dots. We discover that the hole scavengers can determine the reduction pathway as well as the final product. Specifically, when methanol is the solvent and the sole hole scavenger, or when it is used in conjunction with ascorbic acid, ammonium formate, mercaptopropionic acid, or sodium borohydride, the reaction follows a direct reduction pathway. In contrast, with methanol and sodium sulfite, the reaction proceeds via a coupling route. Some hole scavengers directly participate in the redox reaction of intermediates. This study demonstrates that the type of hole scavenger can alter the reaction pathways and determine the reaction outcome and should be chosen with careful consideration. • Nitrobenzene is photo-catalytically reduced by CdS quantum dots with hole scavengers • Different hole scavenger combinations lead to different products • The type of hole scavenger affects reaction times and pathways The role of hole scavengers in photocatalysis is often regarded to be removing the holes in photocatalysts by donating electrons to them. Mureithi et al. show that the effect of hole scavengers goes beyond removal of holes to affecting the reaction time, pathways, and products in photocatalytic reactions.

Cover Feature: Selective Production of Secondary Amine by the Photocatalytic Cascade Reaction Between Nitrobenzene and Benzyl Alcohol over Nanostructured Bi2MoO6 and Pd Nanoparticles Decorated with Bi2MoO6 (Chem. Asian J. 22/2021)

A photocatalytic one-pot cascade synthesis of secondary amine by the reaction between benzyl alcohol (BA) and nitrobenzene (NB) using LED and sunlight is shown on the cover image. The hand represents Bi2MoO6 with flower-like morphology. The photocatalytic reduction of NB takes place on one arm, while on another, photocatalytic oxidation of BA occurs. The reduction of NB produces aniline, while the oxidation of BA produces benzaldehyde. These products further condense to form imine at the junction of the folded hand. Finally, the imine is reduced over the surface of Pd NPs decorated Bi2MoO6 using molecular H2 to secondary amine as the final product. More information can be found in the Full Paper by Rajendra Srivastava et al.

Imposed dynamic irradiation to intensify photocatalytic reactions

Dynamic irradiation is a potent option to influence the interaction between photochemical reactions and mass transport to design high performant and efficient photochemical processes. To systematically investigate the impact of this parameter, the photocatalytic reduction of nitrobenzene was conducted as a test reaction. Dynamic irradiation was realized through provoked secondary flow patterns, multiple spatially distributed light emitting diodes (LEDs) and electrical pulsation of LEDs. A combined experimental and theoretical approach revealed significant potential to enhance photochemical processes. The reaction rate was accelerated by more than 70% and even more important the photonic efficiency was increased by more than a factor of 4. This renders imposed dynamic irradiation an innovative and powerful tool to intensify photoreactions on the avenue to large scale sustainable photochemical processes.

Silver-Doped Antimony Trioxide Nanocomposites for the Photocatalytic Reduction of Nitrobenzene.

A sol-gel technique was used to synthesize silver-doped antimony trioxide nanocomposites. Antimony trioxide and silver-doped antimony trioxide samples were characterized by multiple techniques. The TEM images reveal that antimony trioxide and silver-doped antimony trioxide nanocomposites have nanoparticle shapes. Antimony trioxide has a wide band gap that can be controlled by the doping of silver, and the content of doped silver plays a vital role controlling the band gap energy. The photocatalytic performance of antimony trioxide and silver-doped antimony trioxide nanocomposites was investigated via aniline preparation from the photocatalytic reduction of nitrobenzene. The XPS results reveal that the silver is found in the metallic silver state. Silver doping improves the photocatalytic activity of antimony trioxide for the preparation of aniline. This effect can be ascribed to the narrowing of the band gap and the elongation of the lifetime for electron-hole recombination of antimony trioxide photocatalyst by silver doping. Thus, a photocatalyst with improved photocatalytic activity, limited band gap and improved e-h recombination rate was synthesized by a facile sol-gel process method.

Determination of band edges and their influences on photocatalytic reduction of nitrobenzene by bulk and exfoliated g-C3N4.

Thermally and chemically exfoliated metal-free semiconducting g-C3N4 are synthesized from bulk g-C3N4. Thorough characterization of the synthesized materials is performed with the help of XRD, FTIR, FE-SEM, PL, surface area analysis and DRS to probe differences in structural, morphological and optical properties between thermally and chemically exfoliated g-C3N4. The synthesized materials are exposed to light for photocatalytic reduction of nitrobenzene. The complete reduction reaction mechanism and product selectivity over the synthesized catalysts are studied in this report. The rate of reduction of nitrobenzene is found to be higher with thermally exfoliated g-C3N4, and the selectivity of aniline is found to be higher in the case of chemical exfoliated g-C3N4. The differences in the reactivity are explained in terms of structure, surface morphologies and band edge positions.

Gd-cobalt selenite as an efficient nanocomposite for aniline synthesis from photocatalytic reduction of nitrobenzene

In this investigation, Gd-CoSeO3 nanocomposite with controlled Gd doping contents was synthesized using a sol gel method. The resultant specimen was found to have large specific surface area (115m2/g) and limited particle size (15nm). TEM examination illustrated that the synthesized Gd-CoSeO3 nanocomposite exhibited nanospherical morphology. Also, it was revealed that band gap controlling of the CoSeO3 nanoparticles could be accomplished via managing the Gd contents. The photocatalytic activity of the Gd-CoSeO3 nanocomposite samples was inspected via Nitrobenzene – aniline transformation applying visible light irradiation. Gadolinium doping was adopted to improve the photo-catalytic of the synthesized CoSeO3. This can be accredited to band gap decrease of CoSeO3 by Gd doping as well as life time increase of e-h recombination rate which occur via electron trapping by Gd metal. Therefore, we can prepare an efficient photocatalyst by sol- gel method and photoassisted deposition method to control band gap and e-h recombination rate.

Preparation of aniline from photocatalytic reduction of nitrobenzene using Pt/Nd2O3 nanocomposite

In this manuscript, a template method was used to synthesis Pt-doped Nd2O3 nanostructures with controlled Pt doping contents. The characterizations illustrated that the obtained samples have ultra high surface area (190 m2/g), high crystallinity, small grain size (20 nm) and hollow spherical like morphology. Also, the band gap of the Pt-doped Nd2O3 nanostructures can be controlled by controlling the Pt contents. The photocatalytic activity of the Pt-doped Nd2O3 nanostructures samples was studied by studying the reduction of nitrobenzene into aniline using visible light irradiation. The photocatalytic performance of Nd2O3 was enhanced by Pt doping. This can be attributed to the fact that the trapping effect of the Pt-doped Nd2O3 nanostructures and the red shift of absorption edge. The study result provides an effective method to create different photocatalysts with enhanced visible-light-driven photocatalytic performance.

Visible light photocatalytic reduction of nitrobenzene using Ag/Bi2MoO6 nanocomposite

The hydrothermal method was used to prepare Bi2MoO6 nanoparticles, and photo-assisted deposition method (PAD) was used to doped silver into Bi2MoO6 surface. Different characterization techniques were used to characterize the produced Bi2MoO6 and Ag/Bi2MoO6 nanoparticles, such as for the surface area measurement, X-ray diffraction, photoluminescence emission spectra, transmission electron microscopy, ultraviolet and visible spectroscopy, and X-ray photoelectron spectroscopy. Photocatalytic reduction of nitrobenzene under visible light irradiation was used to measure the photocatalytic performance of Bi2MoO6 and Ag/Bi2MoO6 nanoparticles. The results reveal that doping of silver led to a shift of the absorption edge of Bi2MoO6 to high wavelength. 0.15wt% Ag/Bi2MoO6 has the highest photocatalytic activity. The highest photocatalytic activity of 0.15wt% Ag/Bi2MoO6 nanoparticle remains unchanged after being reused five times.

Stoichiometric production of aminobenzenes and ketones by photocatalytic reduction of nitrobenzenes in secondary alcoholic suspension of titanium(IV) oxide under metal-free conditions

Photocatalytic conversion of nitrobenzenes in 2-propanol suspensions of bare titanium(IV) oxide (TiO2) under various conditions was examined. Aniline and acetone were simultaneously produced almost stoichiometrically from a 2-propanol suspension of TiO2 containing nitrobenzene under deaerated conditions without the use of a precious metal. Nitrobenzenes having another reducible group such as vinyl, chloro and bromo were chemoselectively reduced to corresponding aminobenzenes in 2-propanol suspensions of a TiO2 photocatalyst with an almost stoichiometric amount of acetone. Photocatalytic reduction of nitrobenzene and oxidation of 2-propanol occurred even in the presence of oxygen, and no re-oxidation of anilines occurred.

Efficient hydrogen production and photocatalytic reduction of nitrobenzene over a visible-light-responsive metal–organic framework photocatalyst

Efficient hydrogen production and photocatalytic reduction of nitrobenzene were achieved by using a Pt-deposited amino-functionalised Ti(IV) metal–organic framework (Pt/Ti-MOF-NH2) under visible-light irradiation. XRD and N2 adsorption measurements revealed that crystalline microporous structures were formed and maintained even after the Pt deposition. The photocatalytic activity for the visible-light-promoted hydrogen production was improved through the optimization of the deposition amount of Pt as a cocatalyst. The optimised amount of Pt was determined to be 1.5 wt%. The results of in situ ESR measurements clearly indicate that the reaction proceeds through the electron transfer from the organic linker to deposited Pt as a cocatalyst by way of titanium-oxo clusters. In addition, the Pt/Ti-MOF-NH2 photocatalyst was found to catalyse photocatalytic reduction of nitrobenzene under visible-light irradiation. It was also confirmed that the catalyst can be reused at least three times without significant loss of its catalytic activity.

Preparation, characterization, and photocatalytic performance of Ce2S3 for nitrobenzene reduction

Ce2S3 photocatalysts were synthesized by a co-precipitation method using cerium nitrate and thioacetamide as raw materials. The samples were characterized by X-ray powder diffraction analysis, UV–visible diffuse reflectance spectroscopy, scanning electron microscopy, and differential thermal analysis. Photocatalytic reduction of nitrobenzene (NB) under UV or visible light illumination was used to evaluate the photocatalytic activity of the Ce2S3 samples. The result indicated that the sample prepared at 300°C for 12h exhibited the highest activity. For 140mL 8.13×10−4mol/L of NB in methanol solvent, after illumination for 5h, about 43.9% and 34.7% of NB were reduced to aniline over the sample under UV and visible light irradiation, respectively. The effects of the catalyst amount, illumination time, and sorts of solvent on the photocatalytic performance were investigated specifically. The reduction process of NB over Ce2S3 was finally discussed.

Preparation of Hydroxynaphthalene-Modified TiO2 via Formation of Surface Complexes and their Applications in the Photocatalytic Reduction of Nitrobenzene under Visible-Light Irradiation

Visible light-sensitive photocatalysts were designed by the surface modification of TiO(2) using hydroxynaphthalenes, i.e., mono- and dihydroxy derivatives of naphthalene, via formation of surface complexes. The differences in the coordination ability on TiO(2) were confirmed depending on the numbers and substitution patterns of hydroxy groups. The relatively intense visible light absorption was observed after modification of TiO(2) surface by colorless 2,3-dihydroxynaphthalene (2,3-DN) having two neighboring hydroxy groups. Platinized TiO(2) (Pt-TiO(2)) modified with suitable amount of 2,3-DN showed higher photocatalytic performances and good reusability in the reduction of nitrobenzene to aminobenzene with relatively high selectivity under irradiation of visible light (λ > 420 nm).

Photocatalytic Reduction of Nitrobenzene with NaBH4 in Aqueous Medium Over the Ag/AgBr/TiO2/NZ and Ag/AgBr/NZ Nanocomposites

A new approach forward to photocatalytic reduction of nitro compounds was studied, over the clinopti- lolate-based silver bromide and silver bromide-titanium dioxide photocatalysts that were prepared and characterized. The photoreaction performed at the presence of NaBH4 which is a strong reducing agent in solution medium. A new mechanism is proposed for nitrobenzene reduction under the photocatalytic conditions. The effect of pH, illumination source, NaBH4 concentration and temperature were also studied. The results showed that the best efficiency obtains over the Ag/AgBr/TiO2/NZ in natural pH under UV light. Also, we observed that the photoreduction efficiency was affected by changing the NaBH4 concentration and temperature. However the effect of former case was more considerable compared to the latter case.

Preparation, characterization and activity evaluation of Ag2Mo4O13 photocatalyst

Ag2Mo4O13 photocatalyst was prepared by the hydrothermal method using AgNO3 and (NH4)2MoO4 as raw materials in one step. The Ag2Mo4O13 photocatalyst was characterized by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, N2 adsorption measurements, and terephthalic acid photoluminescence (TA-PL) probing technique. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic oxidation of methyl orange and photocatalytic reduction of nitrobenzene. The results showed that, the optimum catalyst concentration is 3g/L, and the optimum optical thickness is 49.4. When the reaction solution was illuminated for 60min and 10h, and the amount of photocatalyst was 2.0g/L, the methyl orange conversion and aniline yield were 76.4% and 63.3%, respectively. The effect of different heat treatment conditions on the photocatalytic activity of the photocatalyst was also investigated. The best preparation condition is heat treatment at 500°C for 10h. Compared with those photocatalysts prepared at any other conditions, the photoabsorption wavelength range of the photocatalyst calcined at 500°C for 10h extends greatly towards visible light and it also improves the utilization of the total spectrum. The mechanisms of influence on the photocatalytic activity were also discussed.

Photocatalytic reduction of nitrobenzene over titanium dioxide: by-product identification and possible pathways

The photocatalytic reduction of nitrobenzene (ethanol + TiO2 + UV-light) in non-aqueous suspension yielded aniline and acetaldehyde as main products. However, various by-products as intermediates of nitrobenzene photoreduction (i.e. nitrosobenzene and hydroxyaniline) and others (i.e. indoles and quinolines) were also detected. These last results were explained in terms of reactions between aniline and oxidation products of ethanol.

Photochemical and photocatalytic reduction of nitrobenzene in the presence of cyclohexene

Irradiation with light of wavelength higher than 350 nm of deaerated mixtures of nitrobenzene and cyclohexene leads to the reduction of the nitro-compound, with the formation of C 6H 5N(O)NC 6H 5 (32%), C 6H 5NNC 6H 5 (21%), C 6H 5NH 2 (15%), C 6H 5N(H)C 6H 9 (32%). The same stable reduction products are obtained when the photochemical experiments are carried out in the presence of powder dispersions of TiO 2 or WO 3 or CdS. On the other hand, the photocatalytic contribution of these semiconductors plays an important role in the relative product distribution, which is observed to depend on both competitive adsorption–desorption equilibria of the involved reagents and intermediates on the solid surface and the different reducing power of the photoexcited semiconductors. Cyclohexene participates in the photoinduced reduction of nitrobenzene, undergoing oxidation, and producing the required electrons and protons. Experimental evidence for the formation of radical species deriving from the oxidation of this alkene is obtained by ESR spin trapping investigation. We report here for the first time, the photoinduced allylic amination of cyclohexene with nitrobenzene to give the important building block of synthetic interest C 6H 5N(H)C 6H 9.

Photoreduction of nitrobenzene to aniline in ?hybrid? photocatalytic systems

Irradiation of suspensions of CdS in water-ethanol mixtures containing nibrobenzene with light at λ > 320 run does not in practical terms lead to the reduction of the nitrobenzene to aniline. It has been shown that the formation of aniline occurs when solvato complexes of vanadium(III) (γPhNH2=18.1·10−3) and vanadium(IV) (γPhNH2= 2.84·10−3) are added to the system. The photocatalytic reduction of nitrobenzene is accompanied by oxidation of the alcohol to acetaldehyde and acetal. The proposed process mechanism includes stages and acceptance of an electron photogenerated in the semiconductor by vanadium compounds and of a hole by molecules of the alcohol and subsequent stages of reaction of the reduced forms of vanadium, and also of the ethoxy radicals with nitrobenzene, which leads to its reduction.