Oxidation Of Veratryl Alcohol Research Articles

Solar Selective Photooxidation of Veratryl Alcohol by Suppression of Reactive Oxygen Species Through Band Modulation in the BiOI/Bi4Ti3O12 Heterojunction.

Lignin valorization through heterogeneous photocatalysis is a promising pathway for obtaining value-added products, including chemical building blocks, biofuels, etc. However, several challenges still demand attention and resolution in this field. One of the key parameters in the heterogeneous photocatalytic process is the synthesis of efficient photocatalysts that can accomplish efficient and selective reactions. Selective conversion of lignin can be achieved by using heterojunction photocatalysts which can efficiently separate charge carriers' and promote selective reactions by band structure modulation. This work details a straightforward approach for synthesizing heterojunction photocatalysts based onBi4Ti3O12and BiOI involving the hydrothermal and co-precipitation methods. Additionally, the synthesized composites were employed in the selective oxidation of veratryl alcohol, a lignin-derived model compound, to produce high-value-added veratraldehyde. The experimental results showed that the BiOI/Bi4Ti3O12heterojunction (12.5 mol %BiOI)showedsuperior activity with a veratraldehyde yield of 5.4 and 27.2 times higher than those of Bi4Ti3O12and BiOI, respectively. The mechanistic studies revealed that the improved activity and selectivity were due to the enhanced charge carriers' separation and the suppression of reactive oxygen species formation through modulation of band structure. This study allows a green approach to lignin-derived biomass valorization to obtain high-value chemicals.

Catalytic oxidation of lignin model non-phenolic monomer Veratryl alcohol over iron containing mesoporous SBA-1

Catalytic oxidation of lignin model non-phenolic monomer Veratryl alcohol over iron containing mesoporous SBA-1

Synthesis and Evaluation of Mesoporous Silica Nanoparticle Catalyst Supports Prepared from South African Coal Fly Ash

The development of environmentally sustainable catalytic reaction systems for the oxidation of organic compounds has gained significant interest, with widespread application across various industries. This study investigates the suitability of mesoporous silica nanoparticles, synthesized from coal fly ash, as catalyst supports in the oxidation of veratryl alcohol, a compound that serves as a model to mimic the oxidation behavior of lignin-derived structures commonly found in biomass waste. A Cu(II) salicylaldimine complex was employed as the catalyst, with tert-Butyl hydrogen peroxide as the oxidant. Silica catalyst supports were synthesized from coal fly ash derived Na2SiO3 solutions. The effect of pre-dealumination of coal fly ash during Na2SiO3 preparation, variation of the surfactant in silica nanoparticle synthesis, and storage conditions of the catalyst supports on the performance of the coal fly ash derived silica catalyst supports were evaluated and compared to the performance of MCM-41 and SBA-15. The textural properties of the coal fly ash derived silica catalyst supports were notably influenced by the choice of surfactant used during its synthesis, while storage conditions affected the abundance of silanol groups necessary for successful catalyst immobilisation.Graphical

Tuning Chemoenzymatic Pd/Laccase Conformation Toward Optimized Heterogeneous Aerobic Oxidation.

Heterogeneous chemoenzymatic catalysts differing in their spatial organization and relative orientation of their enzymatic laccase and Pd units confined into macrocellular silica foams were tested on veratryl alcohol oxidation. When operating under continuous flow, we show that the catalytic efficiency of hybrids is significantly enhanced when the Pd(II) complex is combined with a laccase exhibiting a surface located lysine next to the T1 oxidation site of the enzyme.

Selective oxidation of veratryl alcohol to veratraldehyde using more active catalyst in a continuous reactor

Verataldehyde (3,4-dimethoxybenzaldehyde) was used as a precursor for various industrial applications, such as flavouring agents, odorants, and pharmaceuticals. The major approach of this study is to convert veratryl alcohol to veratraldehyde, and the whole reaction was carried out in a continuous-process reactor. A bimetallic catalyst was prepared by the wet impregnation method in four different ratios by varying the metal percentage (Mn-10 % and Zn-5–20 %). These metals were incorporated into the activated carbon, which has a high mesoporous nature and was prepared from the used waste surgical mask. The catalysts were subjected to analysis and characterization. Textural characteristics, morphology, chemical properties, and stability of the catalyst were ascertained by utilizing X-ray diffraction, Brunauer-Emmett-Teller, N2 adsorption–desorption isotherm, Fourier transform infrared spectroscopy, and a transmission electron microscope. By varying the continuous reactor parameters such as pressure, temperature, WHSV−1, and reaction time, the catalysts were optimised to achieve the maximum conversion and selectivity of the veratryl alcohol. The AC-Mn (10 %)/Zn (15 %) catalyst was carried out under ideal conditions: 90 °C, 5 mL of TBHP as the solvent, 15 bar of pressure, and 3.2 g of catalyst proven a greater result in the reaction with a conversion and selectivity of 98 %. The stability and reusability of the catalyst were confirmed by delivering a 95.8 % yield even after five reaction runs. A continuous reaction study can provide valuable inputs for the commercial exploitation of veratryl alcohol (VA) to veratraldehyde (VAld). Again, catalytic support was synthesised utilising waste products, and the metal components are cost-effective as compared to noble metals.

Liquid phase selective oxidation of veratryl alcohol to veratraldehyde using pure and Mg-doped copper chromite catalysts.

Mg-doped copper chromite (CuCr2O4) nanocomposites were synthesised through conventional technique. The pure and doped CuCr2-xMgx O4 (x = 0.00-0.1, 0.2 and 0.3%) nanocomposites were characterized in terms of their morphology, crystal structure, surface area and catalytic performance. The chemical composition of CuCr2-xMgx O4 was confirmed via FT-IR. The formation of pure and doped catalysts was validated by XRD results. TEM/SEM confirmed the formation of CuCr2-xMgxO4 nanoparticles. Mg-doped samples possess a high specific surface area compared to pure CuCr2O4. Thus, the effects of temperature, solvent, time, oxidant and the amount of catalyst on the oxidation of veratryl alcohol were reported. Furthermore, detailed mechanisms of the catalytic oxidation of veratryl alcohol as well as the reusability and stability of the nanomaterial were investigated. The resulting composites were shown to be effective heterogeneous catalysts for the oxidation of veratryl alcohol.

Fe-Ni bimetallic supported on mordenite catalyst for selective oxidation of veratryl alcohol in a continuous reactor

Veratryl alcohol (VA) is preferentially oxidized to veratraldehyde (VADE) using a heterogeneous catalyst, which is more favoured in industries. Commercial mordenite (Ca,Na2,K2) Al2Si10O24·7H2O) was desilicated with NaOH and loaded with nickel and iron bimetal by the wet impregnation method. The synthesised Mordenite-Fe(5 %)/Ni(5–20 %) bimetallic catalyst, possessing active Bronsted acid sites, was employed to selectively oxidize the veratryl alcohol reaction. FT-IR, XRD, BET, HR-SEM, HR-TEM, and TPD were employed to determine the catalyst's textural attributes, morphology, chemical properties, and stability. Selective oxidation was performed over the catalysts using TBHP as an oxidant in a continuous reactor. To examine the most active catalyst among the four and to maximise the conversion and yield, the reaction conditions are optimised for various reaction parameters The reaction conditions were optimized by attaining 100 % conversion at temperature (90° C) for time (2 hr) and a maximum conversion of 97 % and a selectivity of 99 % at 10 bar pressure, WHSV (1.0 h−1) with acetonitrile solvent. The result of the study display that Fe (5 %) and Ni(15 %) impregnated on mordenite exhibits excellent catalytic stability with conversion (100 %) and selectivity (99 %) among the other catalysts. During regeneration, the conversion rate declined from 99.5 to 92.4.7 % and selectivity declined from 100 % to 96.2 % at the end of the seventh cycle. The high selectivity and stability of MOR-Fe(5 %)/Ni(15 %) imply that they might function properly as appropriate catalysts for the oxidation of aromatic alcohols. The advantages of the current synthesis are its cost-efficiency and eco-friendliness.

Green synthesis of silver nanoparticles using sustainable bio-fertilizer (Panchakavyam) for the selective oxidation of propylene glycol and veratryl alcohol

This study demonstrates the selective oxidation of propylene glycol and veratryl alcohol utilizing silver oxide nanoparticles. This work adopted employing Panchakavyam, a medicinally rich bio-fertilizer for synthesizing silver oxide nanoparticles. In the present study, panchakavyam was prepared as a supporting material for the synthesis of silver oxide nanoparticles (Ag2O NPs). The traditional source of panchakavyam makes it cost effective, eco-friendly and the positive alteration of structure and shape of the catalyst enabled to deliver high yield of value added products. The synthesized silver oxide nanoparticle’s structure, shape, reactivity, stability, nature of the catalyst, thermal behaviour were studied and analysed through standard catalyst characterization techniques. Post synthesis of nanoparticles, selective oxidation reaction was carried out by confining the silver oxide nanoparticles as a nano catalyst. The tert-butyl hydroperoxide was chosen as the solvent for the oxidation studies of propylene glycol and veratryl alcohol. This study was performed by varying the reaction parameters such as temperature, pressure, time, WHSV−1 etc., to obtain the maximum yield of most desired product. The study involving conversion of propylene glycol(PG) to hydroxy acetone(HA) showed a conversion and selectivity of 100 and 99%, respectively. Similarly conversion of veratryl alcohol(VAOL) to veratraldehyde(VAL) showed a conversion and selectivity of 100 and 97.8%, respectively. The result of the study provides a path to explore the adoption of sustainable catalyst in the conversion of propylene glycol and veratryl alcohol to an industrially important products.

A copper decorated porphyrin-based porous organic polymer: Evaluation in the oxidation of lignin model compounds

A novel porous organic polymer containing porphyrin units was synthesized and decorated with copper to produce the metallated POP, Cu-TriPOP. The native POP, Nat-TriPOP and metal-decorated Cu-TriPOP exhibited BET surface areas of 595 m2/g and 373 m2/g, respectively. Excellent thermal stability up to 300 °C was observed by thermogravimetric analysis. Transmission electron microscopy (TEM) showed a sea urchin/bush-like morphology. The metal-decorated POP, Cu-TriPOP, was evaluated in the oxidation of veratryl alcohol and other related substrates. Excellent catalytic performance was achieved with conversions of around 80%. The addition of ascorbic acid, a well-known radical scavenger, significantly reduced the activity, suggesting that a radical mechanism is most likely operative. In addition, excellent catalyst recovery and recyclability were achieved for up to five cycles with minimal decrease in activity.

TiO2/SO4/Ni@SBA-15 catalysts for the selective oxidation of veratryl alcohol to veratraldehyde in a continuous reactor

Veratraldehyde is a crucial industrial component used to make important chemicals, drugs, flavours, perfumes, mosquito repellents and cancer-fighting substances. This research focuses on the continuous processing of veratryl alcohol to veratraldehyde using the catalyst system composed of SBA-15/TiO2/SO4/Ni. The objective of this study is to explore variations in continuous processing parameters and catalyst loading to achieve maximum conversion and selectivity of veratraldehyde. The catalyst was synthesized and then characterized using the X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) surface area analysis, and transmission electron microscopy (TEM), and Temperature Programmed Desorption (TPD). The catalyst was successfully synthesized, and the results of these characterization procedures revealed its particular porosity structure and composition. By attaining maximum conversion and selectivity at a lower temperature of 90 °C, the continuous process highlighted the catalyst's energy efficiency. The findings demonstrated that the highest veratraldehyde selectivity and yield were obtained under optimal reaction conditions, including a reaction time of 2 h for the catalyst SBA-15/TiO2/SO4/Ni(8%). This catalyst produced the best results, with a veratraldehyde selectivity and conversion of 100 and 99.5%, respectively. In addition to optimising the reaction conditions, the catalyst's reusability was assessed by running the same catalyst through the reaction seven times. The outcomes demonstrated that even after numerous applications, the catalyst maintained good activity and selectivity. This shows the promise of the SBA-15/ TiO2/SO4/Ni(8) catalyst system for the selective oxidation of veratryl alcohol to veratraldehyde in terms of excellent selectivity, good yield, and reusability. Veratraldehyde could be produced industrially at low cost and with minimal impact on the environment thanks to this investigation of a continuous process.

Controlled Immobilization of a Palladium Complex/Laccase Hybrid into a Macrocellular Siliceous Host.

This study investigates the site-directed immobilization of a hybrid catalyst bearing a biquinoline-based-Pd(II) complex (1) and a robust laccase within cavities of a silica foam to favor veratryl alcohol oxidation. We performed the grafting of 1 at a unique surface located lysine of two laccase variants, either at closed (1⊂UNIK157 ) or opposite position (1⊂UNIK71 ) of the enzyme oxidation site. After immobilization into the cavities of silica monoliths bearing hierarchical porosity, we show that catalytic activity is dependent on the orientation and loading of each hybrid, 1⊂UNIK157 being twice as active than 1⊂UNIK71 (203 TON vs 100 TON) when operating under continuous flow. These systems can be reused 5 times, with an operational activity remaining as high as 40 %. We show that the synergy between 1 and laccase can be tuned within the foam. This work is a proof of concept for controlling the organization of a heterogeneous hybrid catalyst using a Pd/laccase/silica foam.

Nanosponge-C3N4 composites as photocatalysts for selective partial alcohol oxidation in aqueous suspension.

A set of four composite materials was prepared, consisting of a nanosponge matrix based on β-cyclodextrin in which carbon nitride was dispersed. The materials were characterized by the presence of diverse cross-linker units joining the cyclodextrin moieties, in order to vary the absorption/release abilities of the matrix. The composites were characterized and used as photocatalysts in aqueous medium under UV, visible and natural solar irradiation for the photodegradation of 4-nitrophenol, and for the selective partial oxidation of 5-hydroxymethylfurfural and veratryl alcohol to the corresponding aldehydes. The nanosponge-C3N4 composites showed higher activity than the pristine semiconductor, which can probably be attributed to the synergic effect of the nanosponge, capable of increasing the substrate concentration near the surface of the photocatalyst.

Selective aerobic oxidation of biomass model compound veratryl alcohol catalyzed by air-stable copper(ii) complexes in water

Three new copper(ii) complexes were synthesized and successfully utilized as effective catalysts for the selective aerobic oxidation of biomass derived veratryl alcohol to veratraldehyde in water as a green and sustainable reaction medium.

Effects of the Preferential Oxidation of Phenolic Lignin Using Chlorine Dioxide on Pulp Bleaching Efficiency.

Chlorine dioxide is widely used for pulp bleaching because of its high delignification selectivity. However, efficient and clean chlorine dioxide bleaching is limited by the complexity of the lignin structure. Herein, the oxidation reactions of phenolic (vanillyl alcohol) and non-phenolic (veratryl alcohol) lignin model species were modulated using chlorine dioxide. The effects of chlorine dioxide concentration, reaction temperature, and reaction time on the consumption rate of the model species were also investigated. The optimal consumption rate for the phenolic species was obtained at a chlorine dioxide concentration of 30 mmol·L-1, a reaction temperature of 40 °C, and a reaction time of 10 min, resulting in the consumption of 96.3% of vanillyl alcohol. Its consumption remained essentially unchanged compared with that of traditional chlorine dioxide oxidation. However, the consumption rate of veratryl alcohol was significantly reduced from 78.0% to 17.3%. Additionally, the production of chlorobenzene via the chlorine dioxide oxidation of veratryl alcohol was inhibited. The structural changes in lignin before and after different treatments were analyzed. The overall structure of lignin remained stable during the optimization of the chlorine dioxide oxidation treatment. The signal intensities of several phenolic units were reduced. The effects of the selective oxidation of lignin by chlorine dioxide on the pulp properties were analyzed. Pulp viscosity significantly increased owing to the preferential oxidation of phenolic lignin by chlorine dioxide. The pollution load of bleached effluent was considerably reduced at similar pulp brightness levels. This study provides a new approach to chlorine dioxide bleaching. An efficient and clean bleaching process of the pulp was developed.

Catalytic activity of SBA-15 supported CuO for selective oxidation of veratryl alcohol to veratraldehyde

Selective oxidation of veratryl alcohol (VAlc) to veratraldehyde (VAld) under mild conditions using heterogeneous catalysts is advantageous for industrial applications. In the present study, newly developed SBA-15 supported copper oxide catalyst designated as CuO(5,10,15 wt.%)/SBA-15 was examined for the selective oxidation of VAlc to VAld using tert-butyl hydroperoxide (TBHP) as an oxidant between 40 and 100 °C. CuO(10 wt.%)/SBA-15 showed high conversion (82.5%) compared to others by forming VAld with 100% selectivity. We examined its selective oxidising power using a substrate possessing both the primary and secondary alcoholic functions, namely propylene glycol (PG). In this substrate, only the secondary alcoholic group was oxidized to hydroxyacetone (HA). It suggests preferential adsorption of the primary alcoholic group of PG on the catalyst surface close to the adsorbed TBHP, thus leaving only the secondary alcoholic group positionally favourable for oxidation. In addition, the catalyst effectively oxidized 2-butanol to 2-butanone. So, the catalyst is verified active against both primary and secondary alcohols, but when both of them are present on the adjacent carbons of the same compound, only the secondary alcoholic function is oxidized. So, the present catalyst could have tremendous applications for selective oxidation in organic synthesis.

Production of Recombinant Laccase From Coprinopsis cinerea and Its Effect in Mediator Promoted Lignin Oxidation at Neutral pH.

Laccases are multi-copper oxidases that use molecular oxygen as the electron acceptor to oxidize phenolic and indirectly also non-phenolic substrates by mechanisms involving radicals. Due to their eco-friendliness and broad substrate specificity, laccases span a wide range of biotechnological applications. We have heterologously expressed a laccase from the coprophilic basidiomycete Coprinopsis cinerea (CcLcc9) in the methylotrophic yeast Pichia pastoris. The recombinant CcLcc9 (rCcLcc9) oxidized 2,6-dimethoxyphenol in the neutral pH range, and showed thermostability up to 70°C. The rCcLcc9 efficiently oxidized veratryl alcohol to veratraldehyde in the presence of low molecular weight mediators syringyl nitrile, methyl syringate and violuric acid, which are syringyl-type plant phenolics that have shown potential as natural co-oxidants for lignocellulosic materials. In addition, rCcLcc9 is able to depolymerize biorefinery hardwood lignin in the presence of methyl syringate and syringyl nitrile as indicated by gel permeation chromatography, and infrared spectral and nucleic magnetic resonance analyses. Furthermore, we showed that several added-value aromatic compounds, such as vanillin, vanillic acid, syringaldehyde, syringic acid and p-hydroxybenzoic acid, were formed during sequential biocatalytic chemical degradation of biorefinery lignin, indicating that rCcLcc9 harbors a great potential for sustainable processes of circular economy and modern biorefineries.

Synergistic Effect in Au-Cu Bimetallic Catalysts for the Valorization of Lignin-Derived Compounds

The selective oxidation of veratryl alcohol as lignin-derived compound was studied under mild conditions, using Au-Cu catalysts synthesized from pre-formed nanoparticles with different Au:Cu molar ratios. Bimetallic catalysts show higher activity compared to monometallic counterparts, highlighting a clear synergistic effect. By comparing the physico-chemical surface properties of catalysts supported on carbon and Al2O3, we were able to establish a strong support effect, with alumina-based catalysts being more active than carbon-supported ones. Moreover, TEM and X-ray photoelectron spectroscopy (XPS) analyses showed a different composition of nanoparticles (NPs) and metal exposure, and we established that Au is the active phase of the reaction. The co-presence of Au and Cu species, and their different interaction with the support, enabled obtaining more than 70% conversion of veratryl alcohol to veratryl aldehyde as a unique product. Moreover, the Au1Cu1 supported on alumina catalyst was recovered by filtration and reused without significant loss of activity and selectivity up to four times.

Heterogeneous catalyst for the veratryl alcohol oxidation based on gold nanoparticles decorated with graphene quantum dots supported on silicon dioxide

The oxidation of veratryl alcohol can produce veratryl aldehyde or veratryl acid, which are industrially important chemicals widely used in the food and pharmaceutical industries. Gold nanoparticles (AuNPs) functionalized with graphene quantum dots (GQDs) have shown high activity and selectivity as a catalyst for veratryl alcohol oxidation. However, the AuNP/GQD catalyst has excellent dispersibility in aqueous solutions, which makes it difficult to recycle all the catalyst after reaction. In this work, AuNP/GQD catalysts were further immobilized onto a silicon dioxide support by different methods, including physical adsorption, one-pot synthesis, and hydrothermal synthesis to produce AuNP/GQD/SiO2 composites. Extensive characterization of the microstructure, crystallinity, chemical structure, and catalytic performance of the catalysts was performed to evaluate the processing methods. It was demonstrated that the obtained composites are suitable heterogeneous catalysts for the oxidation of veratryl alcohol.

Extracellular Oxidases of Basidiomycete Neonothopanus nambi: Isolation and Some Properties.

Using the original technique of treating biomass with β-glucosidase, a pool of extracellular fungal enzymes was obtained for the first time from the mycelium of basidiomycete Neonothopanus nambi. Two protein fractions containing enzymes with oxidase activity were isolated from the extract by gel-filtration chromatography and conventionally called F1 and F2. Enzyme F1 has a native molecular weight of 80-85 kDa and does not contain chromophore components; however, it catalyzes the oxidation of veratryl alcohol with Km = 0.52 mM. Probably, this enzyme is an alcohol oxidase. Enzyme F2 with a native molecular weight of approximately 60 kDa is a FAD-containing protein. It catalyzes the cooxidation of phenol with 4-aminoantipyrine without the addition of exogenous hydrogen peroxide, which distinguishes it from the known peroxidases. It was assumed that this enzyme may be a mixed-function oxidase. F2 oxidase has Km value 0.27 mM for phenol. The temperature optimums for oxidases F1 and F2 are 22-35 and 55-70°C, and pH optimums are 6 and 5, respectively.

Electrochemical Conversion of the Lignin Model Veratryl Alcohol to Veratryl Aldehyde Using Manganese(III)-Schiff Base Homogeneous Catalysts

Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1–7 were synthetized and characterized by different analytical and spectroscopic techniques. The tetragonally elongated octahedral geometry for the manganese coordination sphere and the global µ-aquo dimeric structure were revealed by X-ray diffraction (XRD) studies for 1, Mn2L12(H2O)2(N(CN)2)2 (N(CN)2 = dicyanamide). Complexes 1–4 behave as more efficient peroxidase mimics as compared to 5–7. Electrochemical oxidation of the lignin model veratrylalcohol (VA) to veratrylaldehyde (VAH) is efficiently catalyzed by a type of dimanganese(III) complexes in a chlorine-free medium. The electrocatalytic reaction proceeds through the oxidation of chloride into hypochlorite at alkaline pH along with the formation of hydrogen from water as a subproduct.