Benzaldehyde Selectivity Research Articles

High-efficiency activation of the C–H bond to synthesize p-methoxy benzaldehyde over a MnO2/CNT/Gr catalyst

The selective oxidation of C(sp3)–H was achieved by the MnO2/CNTs/Gr electrocatalyst: 81.03% faradaic efficiency and 82.73% selectivity of p-methoxy benzaldehyde were obtained.

Synthesis, Crystal Structure of Tetra-Nuclear Macrocyclic Zn(II) Complex and Its Application as Catalyst for Oxidation of Benzyl Alcohol

A new six coordinated tetra-nuclear macrocyclic Zn(II) complex, ZnL4(Phen)2 (1) (HL= 3-bromo-2-hydroxybenzaldehyde-pyridine-2-carbohydrazone, Phen = 1,10-phenanthroline) has been synthesized by the self-assembly of 3-bromo-2-hydroxybenzaldehyde-pyridine-2-carbohydrazone, Zn(CH3COO)2•2H2O, NaOH and 1,10-phenanthroline in water/ethanol (v:v = 1:3) solution. Complex 1 was characterized by elemental analysis, infra red (IR), and single-crystal X-ray diffraction (XRD) analysis. The results show that Zn1 and Zn1b ions are six-coordinated with a distorted octahedral geometric configuration by four O atoms of two different L ligands and two N atoms of two different L ligands, Zn1a and Zn1c ions are also six-coordinated with a distorted octahedral geometric configuration by two N atoms of two different L ligands, two N atoms of Phen ligands and two O atoms of two different L ligands. Complex (1) forms 3D network structure by the - interaction. The selective oxidation reactions of benzyl alcohols catalyzed by complex (1) was investigated. The highest benzyl alcohol conversion and benzaldehyde selectivity were obtained at 100 °C for 4 h under 5 bar of O2. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Selective Oxidation of Benzyl Alcohol in the Aqueous Phase by TiO2‐Based Photocatalysts: A Review

AbstractProduction processes of benzaldehyde have been studied intensively due to its wide range of applications in the industry. The selective oxidation of benzyl alcohol to benzaldehyde by TiO2 is promising as it can occur under mild conditions without toxic by‐products. This article mainly describes the challenges in the photooxidation of benzyl alcohol and the strategies to enhance both the efficiency and selectivity for benzaldehyde. Visible‐light response, charge separation, morphology, and reaction conditions have been listed as critical factors for this process. Different modification methods to improve the insufficient photocatalytic activity of TiO2, such as surface adjustments, metal/non‐metal doping, or semiconductor coupling, are presented. The perspectives for further research in this field are also discussed.

Compatibility between Activity and Selectivity in Catalytic Oxidation of Benzyl Alcohol with Au-Pd Nanoparticles through Redox Switching of SnOx.

A balance between catalytic activity and product selectivity remains a dilemma for the partial oxidation processes because the products are prone to be overoxidized. In this work, we report on the partial oxidation of benzyl alcohol using a modified catalyst consisting of nanosized Au-Pd particles (NPs) with tin oxide (SnOx) deposited on a mesoporous silica support. We found that the SnOx promotes the autogenous reduction of PdO to active Pd0 species on the Au-Pd NP catalyst (SnOx@AP-ox) before H2 reduction, which is due to the high oxophilicity of Sn. The presence of active Pd0 species and the enhancement of oxygen transfer by SnOx led to high catalytic activity. The benzaldehyde selectivity was enhanced with the increase of SnOx content on catalyst SnOx@AP-ox, which is ascribed to the modulated affinity of reactants and products on the catalyst surface through the redox switching of Sn species. After H2 reduction, SnOx was partially reduced and Au-Pd-Sn alloy was formed. The formation of Au-Pd-Sn alloy weakened both the catalytic synergy of Au-Pd alloy NPs and the adsorption of benzyl alcohol on the reduced catalyst, thus leading to low catalytic activity.

Role of water on ozonation of cinnamaldehyde to benzaldehyde under Ca(OH)2 catalysis: A combined in situ DRIFTS and DFT study

The role of water on cinnamaldehyde ozonation to benzaldehyde under Ca(OH)2 catalysis was studied by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) and Density Function Theory (DFT). According to the thermogravimetry results, the water, generated in the ozonation, reacted with CaO to form Ca(OH)2 and then existed on the Ca(OH)2 surface in the form of adsorbed and interlayer water. The experiment results showed that lab-made and pre-processed Ca(OH)2 had better catalytic activities because their specific surface area values were 3.59 and 4.46 times larger than CaO. DFT results indicated that the competitive adsorption between water and ozone was weak due to the difference of their average adsorption energy difference. The major effect of water was to promote ozonide decomposition and ·OH formation. At the presence of water, the DRIFTS signals of physisorption ozone and ozonide disappeared within 20 min, but the signals of oxygen atoms and O2– had about 12% and 33% increasing, respectively. As the water content increased in the system and the key intermediates, ozonides, and ·OH, changed, the ozonation mechanism was changed from the Criegee mechanism to the free radical mechanism, resulting in a significant decrease in the selectivity of benzaldehyde.

Nanostructure Shape-Effects in ZnO heterogeneous photocatalysis

Selective oxidation of alcohols is an essential reaction for fine chemical production. Here, the photocatalytic oxidation of benzyl alcohol by zinc oxide (ZnO) nanocrystals was investigated to clarify the mechanism of selective oxidation with this process. Reactivity when in contact with three distinct ZnO nanocrystal shapes: nanocones, nanorods and nanoplates, was studied in order to compare crystal facet-specific effects in the reaction system. The same non-hydrothermal and non-hydrolytic aminolysis method was used to synthesise all three nanocrystal shapes. The ZnO catalysts were characterized using by a range of techniques to establish the key properties of the prominent ZnO crystal facets exposed to the reaction medium. The ZnO nanocrystals photocatalysed the benzyl alcohol oxidation reaction when irradiated by a 370 – 375 nm LED output and each ZnO crystal morphology exhibited different reaction kinetics for the oxidation reaction. ZnO nanocones displayed the highest benzyl alcohol conversion rate while nanorods gave the lowest. This established a facet-dependent kinetic activity for the benzyl alcohol reaction of (101¯1) > (0001) > (101¯0). Experimental and density functional theory computation results confirm that the {101¯1} facet is a surface that exposes undercoordinated O atoms to the reaction medium, which explains why the reactant benzyl alcohol adsorption on this facet is the highest. Light irradiation can excite valence band electrons to the conduction band, which are then captured by O2 molecules to yield superoxide (O2•–). In a non-aqueous solvent, the photogenerated holes oxidise benzyl alcohol to form a radical species, which reacts with O2•– to yield benzaldehyde. This results in 100% product selectivity for benzaldehyde, rather than the carboxylic acid derivative.

A New Strategy to Regulate the Selectivity of Photo-Mediated Catalytic Reaction.

Here we developed a new method for regulating the selectivity of photo-mediated catalytic reaction by manipulating the surface charge of Au/TiO2 (gold/titanium dioxide) catalysts within chemical reaction timescales. Two kinds of photocatalytic reactions, hydrogenation of acetophenone and benzyl alcohol oxidation, have been applied to investigate the photocatalytic performance over Au/TiO2 catalysts with tunable surface charges. We found that a suitable timescale of switching surface charge on Au would benefit for the enhanced quantum efficiency and play different roles in the selectivity of desired products in hydrogenation and oxidation reactions. Au/TiO2 catalyst under 5 μs flashing light irradiation exhibits much higher selectivity of 1-phenylethanol in the hydrogenation of acetophenone than that under continuous light and 5 s flashing light irradiation; by contrast, Au/TiO2 catalysts under both flashing light and continuous light irradiation exhibit a similar selectivity of benzaldehyde in benzyl alcohol oxidation. Our findings will benefit for a better understanding of electronic structure–mediated reaction mechanism and be helpful for achieving highly efficient photocatalytic systems.

Oxidation of Toluene on Supported and Unsupported LaCoO3 Perovskites Catalyst

Perovskite type oxide are known to be catalysts for a number of reactions such as total and partial oxidation, hydrocracking, hydrogeneous, hydrogenolysis and reduction etc. Efforts has largely been directed towards synthesis of unsupported and supported perovskites oxides of moderates or high specific area, their bulk and surface properties and their role in heterogenous catalysis. Oxidation of aromatic and aliphatic hydrocarbon over LaMO3 (M=Al, Ni, Mn, Co, Fe, Cr etc.) perovskites have been studied. Vapour phase catalytic oxidation of toluene over perovskites Viz., LaCoO3, LaCoO3/ SiO2 and LaCoO3/Al2O3 has been studied. The characterization of the catalyst was carried out using technique Viz. I.R., Surface area, Packing density. Surface acidity, Surface basicity. The surface area measurements in the temperature range 350ºC to 600ºC. The maximum surface area & maximum activity was observed at 450ºC. The heterogeneous catalytic vapour phase oxidation of toluene give benzaldehyde, benzoic acid, maleic acid and CO2 as products over LaCoO3 and LaCoO3 supported on Al2O3 and SiO2 as catalyst. The LaCoO3 supported on Al2O3 has been found to be the most active and selective catalyst giving 84.0% selectivity for benzaldehyde at 450⁰C with surface area 78.9m2/g. The overall Kinetic analysis indicate that the oxidation of Toluene to benzaldehyde is first order. The order of catalytic reactivity is LaCoO3/Al2O3 > LaCoO3/ SiO2 > LaCoO3.

Enhancement of photocatalytic oxidation of benzyl alcohol by edge-functionalized modified carbon nitride: A DFT evaluation

New dye functionalized polymeric carbon nitrides with increased visible light response were designed and fabricated. In this research, Rose Bengal (RB) was immobilized on g-C3N4 (CN) and carboxylated g-C3N4 (CCN) through the formation of a covalent bond. The covalent bonding of Rose Bengal to the CN or CCN resulted in the transfer of electrons from the dye to the semiconductor and the enhancement of the light harvesting performance, which promoted the photocatalytic efficiency. The photocatalytic activity of CN, CCN, and their hybrids with RB toward selective oxidation of benzyl alcohol was investigated under the visible light irradiation. The results obtained from the GC–MS analyses related to the oxidation reaction displayed the highest percentage of benzyl alcohol conversion and benzaldehyde selectivity for the hybrid structures compared to the bare RB, CN, CCN, or a mixture of RB and CN (or CCN). The effect of several parameters, including the amount of photocatalyst and promoter, irradiation time, and photocatalyst type, was studied and optimized. The recovery of RB-CCN (the most active catalyst) was surveyed in five runs, and the results verify that the activity is mostly maintained. Finally, the optimized structure, energy gap, and frontier orbitals of Rose Bengal/graphitic carbon nitride were investigated by DFT methods.

Catalytic Oxidation of Toluene into Benzaldehyde and Benzyl Alcohol Using Molybdenum-Incorporated Manganese Oxide Nanomaterials.

Oxidation of toluene (an organic pollutant), into useful chemical products, is of great interest nowadays. However, efficient conversion of toluene under mild and sustainable conditions is a thought-provoking task. Here, we report MnMoO4 nanomaterials (CH1–CH2), synthesized through a very facile solvothermal approach. Catalytic efficiencies of MnMoO4 nanomaterials were evaluated by direct oxidation of toluene via C–H activation. Toluene was converted into benzaldehyde and benzyl alcohol in the presence of H2O2 as an oxidant at 80 °C. The reaction parameters, that is, catalyst dose, time, and toluene concentration, were varied to obtain the optimal conditions for the oxidation process. The 40.62% maximum toluene conversion rate was obtained after 18 h of oxidation activity with 0.06 g of catalyst CH1. A maximum of 78% benzaldehyde selectivity was obtained with 0.06 g of catalyst CH1 after 18 h of toluene oxidation activity. Also, 62.33% benzyl alcohol selectivity was achieved using 0.1 g of catalyst CH1 after 1 h of activity. Several catalytic cycles were run with CH1 to evaluate catalyst reusability. Potential % toluene conversion was obtained for up to six cycles and their turnover frequencies were found to be 1.94–1.01 s–1. FTIR spectra of catalyst CH1 before and after recovery indicate no significant change. The good conversion rate of toluene and efficient selectivity toward benzaldehyde and benzyl alcohol indicates the robustness and high potential of these catalysts to oxidize toluene under a milder, greener, and hazardous chlorine-free environment.

Coproduction of styrene and benzaldehyde over a boron nitride-supported monomeric MoOx catalyst

Styrene and benzaldehyde are manufactured by energy-intensive direct dehydrogenation and an intermittent liquid chlorine oxidation batch process, respectively. The coproduction of styrene and benzaldehyde through selective oxidation of ethylbenzene is an environmentally friendly and economically feasible alternative. However, it is hard to control the selectivity for styrene or benzaldehyde as a result of deep oxidation reactions. Here, we report an efficient selective oxidation catalyst, boron nitride-supported monomeric MoOx (MoOx/BN), over which styrene and benzaldehyde can be selectively coproduced. Structure characterization and catalytic evaluation reveal that the MoOx/BN catalyst is conducive to the generation of benzaldehyde and less formation of COx than for monomeric MoOx supported on inert silica. Based on the kinetic analysis, over MoOx/BN catalyst, styrene is the primary product and benzaldehyde is the major by-product in the subsequent oxidation reaction. The boron hydroxy groups of the MoOx/BN catalyst are involved in the reaction network, which could regulate the reaction behavior of monomeric MoOx species; thus the reaction generates more benzaldehyde.

Mechanism and kinetics of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin in a membrane microchannel reactor

The highly efficient selective aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin was achieved in a membrane microchannel reactor. The efficiency of benzyl alcohol oxidation was remarkably improved in the micro-structured chemical system, achieving a conversion and benzaldehyde selectivity of 82% and 98%, respectively, in 6.5 min. The classification and transfer of free radicals, as well as the oxygen-transfer mechanism, were determined by in situ EPR (electron paramagnetic resonance) and in situ UV–visible spectroscopy. Further kinetic studies revealed that the oxidation of benzyl alcohol follows the Michaelis–Menten kinetics, with Km = 0.133 mol/L.A mathematic kinetic model was proposed, and the kinetic model fitted the experimental data well. The mathematical model can predict the reaction process at a wide range of benzyl alcohol concentrations, which is beneficial for the process optimization and reactor design.

Simultaneously Enhanced Activity and Selectivity for C(sp3)\u2013H Bond Oxidation Under Visible Light by Nitrogen Doping

Selective oxidation of saturated C(sp3)–H bonds in hydrocarbon to target chemicals under mild conditions remains a significant but challenging task because of the chemical inertness and high dissociation energy of C(sp3)–H bonds. Semiconductor photocatalysis can induce the generation of holes and oxidative radicals, offering an alternative way toward selective oxidation of hydrocarbons under ambient conditions. Herein, we constructed N-doped TiO2 nanotubes (N-TNTs) that exhibited remarkable activity and selectivity for toluene oxidation under visible light, delivering the conversion of toluene and selectivity of benzaldehyde of 32% and > 99%, respectively. Further mechanistic studies demonstrated that the incorporation of nitrogen induced the generation of N-doping level above the O 2p valance band, directly contributing to the visible-light response of TiO2. Furthermore, hydroxyl radicals generated by photogenerated holes at the orbit of O 2p were found to be unselective for the oxidation of toluene, affording both benzaldehyde and benzoic acid. The incorporation of nitrogen was able to inhibit the generation of hydroxyl radicals, terminating the formation of benzoic acid.

Synthesis of a 2,4-DcCoPc/MIL-101(Fe) composite and catalytic oxidation of styrene to benzaldehyde

A new type of 2,4-DcCoPc/MIL-101(Fe) composite was synthesized by modifying MIL-101(Fe) with 2,4-dichlorophenoxy phthalocyanine cobalt (2,4-DcCoPc). X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), N2 physisorption measurements, scanning electron microscopy (SEM), transmittance scanning electron microscopy (TEM) and thermogravimetry analysis (TGA) characterize and analyze the composite material. Due to the excellent catalytic properties of MIL-101(Fe) and 2,4-DcCoPc, 2,4-DcCoPc/MIL-101(Fe) was used to catalyze the oxidation of styrene to benzaldehyde. Significantly, at the molar ratio of 0.24:1, 2,4-DcCoPc/MIL-101(Fe) achieved optimal catalytic performance with conversion rate of styrene at 88% and selectivity for benzaldehyde of 91%. Compared with 2,4-DcCoPc or MIL-101(Fe) alone, the catalytic performance was improved. The composite material can be used as a catalyst for oxidation of styrene to benzaldehyde.

Catalytic Performance of TiO2–Carbon Mesoporous-Derived from Fish Bones in Styrene Oxidation with Aqueous Hydrogen Peroxide as an Oxidant

The catalytic performance of titania-supported carbon mesoporous-derived from fish bones (TiO2/CFB) has been investigated in styrene oxidation with aqueous H2O2. The preparation steps of (TiO2/CFB) catalyst involved the carbonization of fish bones powder at 500 °C for 2 h. followed by impregnation of titania using titanium(IV) isopropoxide (500 µmol) precursor, and calcined at 350 °C for 3 h. The physical properties of the adsorbents were characterized using Fourier transform infrared, X-ray diffraction (XRD), Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), and nitrogen adsorption-desorption studies. The catalytic test was carried out using styrene oxidation with H2O2 as an oxidant at room temperature for 24 h. Its catalytic activity was compared with Fe2O3/CFB, CuO/CFB, TiO2, and CFB catalysts. It is demonstrated that the catalytic activity of TiO2/CFB catalyst has the highest compared to Fe2O3/CFB, CuO/CFB, TiO2, and CFB catalysts in the oxidation of styrene with styrene conversion ~23% and benzaldehyde selectivity ~90%. Kinetics of TiO2/CFB catalyzed oxidation of styrene has been investigated and mechanism for oxidation of styrene has been proposed. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

A novel selective oxidative cleavage of C[sbnd]C bond mediated by black nickel oxide in the presence of molecular oxygen

A selective aerobic oxidative cleavage of CC bond is developed with black nickel oxide (NiOx) as the catalyst. For the oxidation of 1-phenyl-1, 2-ethanediol, a 97.5% conversion in 96.7% selectivity of benzaldehyde is obtained under 0.3 MPa of O2 at 140 °C for 3 h. The relationship between the catalytic performance of NiOx and structure is discussed. It is concluded that the existence of Ni3+ should be crucial to the activity of catalyst. Moreover, the recycling experiments showed that the catalyst can retain a high activity even after being reused for five times.

Transition metal Schiff base complexes supported on layered double hydroxide: synthesis, characterization and catalytic activity for the oxidation of toluene

The catalytic oxidation of toluene was studied over Mn(III) and Fe(III) Schiff base complexes supported layered double hydroxide catalysts. The supported catalysts were synthesized by intercalation method and abbreviated as LDH-[NAPABA-M], {where M = Mn(III) and Fe(III)}. The obtained material was characterized by various physical techniques such as ICP-AES, EDX, XRD, FTIR, SEM, TEM, BET surface area, EPR, and TGA. The liquid-phase catalytic oxidation of toluene was studied using LDH-[NAPABA-M]/TBHP system. A maximum conversion of toluene (55.3%) and selectivity of benzaldehyde (86.1%) was observed with LDH-[NAPABA-Mn(Cl)]/TBHP system, when the reaction is carried out at toluene to tert-butylhydroperoxide (TBHP) molar ratio 1:3, temperature 373 K, and catalyst amount, 100 mg. The catalyst, LDH-[NAPABA-Mn(Cl)] gave excellent; conversion of toluene and selectivity of benzaldehyde in comparison to LDH-[NAPABA-Fe(Cl)] catalyst. The catalyst, LDH-[NAPABA-Mn(Cl)] showed good stability and reusability up to five cycles without significant loss of catalytic activity.

Effect of phthalocyanines supported carbon nanotube for the catalytic oxidation of benzyl alcohol

A series of tetra-substituted metal phthalocyanine-multi-walled carbon nanotube composites ([4a (OPh-p-Cl)MPc]-MWCNTs) were fabricated, which were used to effectively catalyze the oxidation of benzyl alcohol. The as-prepared composites were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscope and transmission electron microscope. In order to improve the catalytic activity, the effects of solvent, amount of oxidant, amount of catalyst, temperature and reaction time on catalytic oxidation of benzyl alcohol to benzaldehyde were studied. It can be found that the Cu phthalocyanine based composite [4a (OPh-p-Cl)CuPc]-MWCNTs have the best catalytic activity in the oxidation of benzyl alcohol. The conversion rate of benzyl alcohol can reached 70%, the selectivity of benzaldehyde was 87%, and the yield of benzaldehyde can reached to 61%. In addition, a possible mechanism for the enhanced catalytic activity of the optimized [4a (OPh-p-Cl)MPc]-MWCNTs has been discussed.

Cobalt Single Atoms Embedded in Nitrogen-Doped Graphene for Selective Oxidation of Benzyl Alcohol by Activated Peroxymonosulfate.

The development of novel single atom catalyst (SAC) is highly desirable in organic synthesis to achieve the maximized atomic efficiency. Here, a Co-based SAC on nitrogen-doped graphene (SACo@NG) with high Co content of 4.1wt% is reported. Various characterization results suggest that the monodispersed Co atoms are coordinated with N atoms to form robust and highly effective catalytic centers to activate peroxymonosulfate (PMS) for organic selective oxidation. The catalytic performance of the SACo@NG/PMS system is conducted on the selective oxidation of benzyl alcohol (BzOH) showing high efficiency with over 90% conversion and benzaldehyde selectivity within 180min under mild conditions. Both radical and non-radical processes occurred in the selective oxidation of BzOH, but the non-radical oxidation plays the dominant role which is accomplished by the adsorption of BzOH/PMS on the surface of SACo@NG and the subsequent electron transfer through the carbon matrix. This work provides new insights to the preparation of efficient transition metal-based single atom catalysts and their potential applications in PMS mediated selective oxidation of alcohols.

Fabrication of Pd–Au Clusters by In Situ Spontaneous Reduction of Reductive Layered Double Hydroxides

In this work, layered double hydroxides (LDHs) including the variable valence Co2+ ions (CoAl-LDHs) is discovered to be capable of serving as the support and the reducing agent for the fabrication of well-distributed PdAu nanoparticles because of the low potential for reduction. Specifically, the active metal precursors undergo the redox process, in which Co2+ is oxidized to Co3+, while active metal ions are successfully reduced to bimetallic PdAu nanoparticles with the dispersion of 73%. Furthermore, the obtained catalysts are evaluated in the selective oxidation of benzyl alcohol as the probing reaction to explore the catalytic behavior. As for intrinsic activity, PdAu/CoAl-LDHs derived by the above in situ spontaneous reduction exhibits activation energy of 62.4 kJ mol−1, much lower than that of PdAu/CoAl-LDHs prepared by sol-immobilization. When the reaction time reaches to 4 h, the benzaldehyde selectivity over the former catalyst is up to 94%, originating from the surface electron starvation of active metals that promots the hydroxyl groups reacting with O2 to produce benzaldehyde.