Hydrodeoxygenation Of Vanillin Research Articles

Construction of dendritic mesoporous SiO2 supported Cu catalyst for hydrodeoxidation of lignin derivatives

Chemoselective hydrodeoxygenation (HDO) of lignin derivatives is of great importance in converting biomass into high value-added chemicals. Herein, we report a simple hydrothermal pathway to fabricate a highly active, chemically selective, and reusable catalyst (Cu/DMSN) by loading copper clusters on “dendritic” mesoporous silica nanospheres. Cu/DMSN exhibits exceptional catalytic activity (conversion > 99 %, selectivity > 99 %) in the HDO of vanillin toward 2-methoxy-4-methylphenol under mild conditions (140 °C, 0.5 MPa, 3 h), along with good scalability and a wide range of substrates. The excellent catalytic performance can be owed to the combination of suitable acid site and more exposed metal site. This study provides a new strategy for designing supported metal catalysts for hydrodeoxidation of biomass and its derivatives.

Investigation of ruthenium loaded beta zeolite catalyst performance in vanillin hydrodeoxygenation yielding both monomeric and dimeric cycloalkanes

The valorization of lignin-derived bio-oil is studied extensively due to its promising contribution to sustainability. Among these studies, many have focused on the hydrodeoxygenation (HDO) of phenolic model compounds as it is a crucial process in obtaining valuable oxygen-free hydrocarbons. In this work, vanillin HDO was performed on various bifunctional ruthenium-based zeolite catalysts with different zeolite supports (Y, ZSM-5, and beta) in a batch reactor. Ru-loaded beta zeolite catalysts (Ru/Hβ) exhibited the highest HDO activity among them, and the formation of dimeric cycloalkanes of high value were also observed specifically when using the Ru/Hβ catalyst. Due to their benefits of direct use in blending of biofuel, factors promoting the dimerization of phenolic monomers were extensively examined through a series of experiments using a mix of phenolic model compounds as HDO reactants. Specific oxygen containing functional groups contributed to the aldol condensation of aromatic species, and the structure and kinetic diameter of the monomers had a profound effect on the ability to participate in dimerization. Additionally, the metal loading of the catalyst and reaction conditions such as temperature and hydrogen pressure were varied to observe each of their effects on the product distribution. The change in metal loading had a remarkable impact on the preferred reaction pathway and product selectivity, while a high temperature of 200 °C and hydrogen pressure of 50 bar was determined to be necessary to fully achieve HDO to cycloalkanes. Consequently, this study has provided useful information on the production of both monomeric and dimeric cycloalkanes and has contributed to the development of the bio-oil upgrading process.

Construction of Molecularly Dispersed Polyoxometalate-Alumina Hybrid Hollow Nanoflowers via Water-Induced Kirkendall Effect.

Hybrid nanomaterials with controllable structures and diverting components have attracted significant interest in the functional materials field. Here, we develop a solvent evaporation-induced self-assembly (EISA) strategy to synthesize nanosheet-assembled phosphomolybdic acid (H3PMo)-alumina hybrid hollow spheres. The resulting nanoflowers display a high surface area (up to 697 m2 g-1), adjustable diameter, high chemical/thermal stability, and especially molecularly dispersed H3PMo species. By employing various microscopic and spectroscopic techniques, the formation mechanism is elucidated, revealing the simultaneous control of the morphology by heteropoly acids and water through the water-induced Kirkendall effect. The versatility of the synthesis method is demonstrated by varying surfactants, heteropoly acids, and metal oxide precursors for the facile synthesis of hybrid metal oxides. Spherical hybrid alumina serves as an attractive support material for constructing metal-acid bifunctional catalysts owing to its advantageous surface area, acidity, and mesoporous microenvironment. Pt-loaded hollow flowers exhibit excellent catalytic performance and exceptional stability in the hydrodeoxygenation of vanillin with recyclability for up to 10 cycles. This research presents an innovative strategy for the controllable synthesis of hybrid metal oxide nanospheres and hollow nanoflowers, providing a multifunctional platform for diverse applications.

Encapsulated metal-based MOF nanoparticles as efficient catalysts for catalytic transfer hydrodeoxygenation of lignin-derived vanillin to 2-methoxy-4-methylphenol

A range of carbon-encapsulated non-precious metal catalysts (Ni@C, Ce@C, Mo@C, and Zn@C) were prepared using the hydrothermal approach for the catalytic transfer hydrodeoxygenation of vanillin compound derived from lignin. The catalytic efficacy was affected by the level of acid sites, catalyst durability, and the cooperation with H-donor solvents. Analysis indicated that the thin carbon layer enclosing the active sites notably improved catalytic effectiveness and thermodynamic stability compared to alternative catalysts. Notably, Ni@C demonstrated superior catalytic performance, achieving a vanillin conversion rate of 98.72 % and an 87.12 % yield of the major product 2-methoxy-4-methylphenol under specific conditions (240 ℃, 2.0 MPa N2, ethanol as a solvent, 4-hour reaction time). These findings underscore the significant potential of carbon-wrapped MOF catalysts in advancing the sustainable utilization of lignin and fostering the growth of a more eco-friendly bioeconomy.

Highly dispersed Pd nanoparticles in situ reduced and stabilized by nitrogen-alkali lignin-doped phenolic nanospheres and their application in vanillin hydrodeoxygenation

Highly dispersed Pd nanoparticles in situ reduced and stabilized by nitrogen-alkali lignin-doped phenolic nanospheres and their application in vanillin hydrodeoxygenation

Pd‐Pt Bimetallic Catalysts for Enhanced Low‐Temperature Hydrodeoxygenation of Vanillin

AbstractTo make pyrolytic bio‐oil useful as a transportation fuel, the oxygen content must be reduced, and this can be carried out by using catalytic hydrodeoxygenation (HDO) reaction. The greatest challenge is associated with the removal of strongly bound oxygenated groups without saturating the aromatic ring while preserving the number of carbons. However, the development of a stable catalyst that can selectively remove such oxygenated groups with low hydrogen consumption is still challenging. In this context, a systematic study on HDO of vanillin on bimetallic Pd−Pt catalysts was carried out. It aims to study the effect of bimetallic synergy in terms of activity and selectivity to creosol. Metallic nanoparticles of Pd and Pt were synthesized by sol immobilization technique and deposited on TiO2. The conversion of vanillin was correlated to the Pd−Pt atomic ratio, while the production of the creosol was correlated to the Pd(0)/(Pd+Pt) ratio at the surface. Full conversion of vanillin was obtained at low reaction temperature (20 °C) achieving nearly 100 % selectivity to creosol. These results represent a step forward in advancing the development of more efficient and sustainable processes for bio‐oil upgrading.

Promoting Effect of Ce and La on Ni-Mo/δ-Al2O3 Catalysts in the Hydrodeoxygenation of Vanillin.

A crucial aspect of adding an economical and environmental dimension to the upgrading of bio-oils is to develop catalysts with enhanced and prolonged activity. In the present study, the effect of doping δ-alumina (Al2O3) with oxides of cerium (Ce) and lanthanum (La) before thermal treatment was investigated. The performance of such an Al2O3-supported nickel-molybdenum (Ni-Mo) catalyst was evaluated by studying the selectivity for the direct hydrodeoxygenation (HDO) of vanillin to cresol under continuous-flow conditions. In addition, the effect of adding H2S during catalyst activation and/or performance tests was also evaluated. Overall, enhanced performance of the doped NiMo catalyst in the HDO process has been demonstrated and an increased selectivity for cresol via direct HDO observed. The advantage of adding La and Ce is supported by the characterization results, where less sintering and enhanced pore diameter of the doped Al2O3 were observed after thermally inducing the transformation from the δ to θ phases. The improved characteristics and prolonged activity of the doped Al2O3 were also deduced by the lower acidity of the catalyst, which resulted in reduced coke formation during the HDO process.

Synergy of metallic Co and oxygen vacancy sites in Co/Ce-MOF catalysts for efficiently promoting lignin derived phenols and macromolecular lignin hydrodeoxygenation

The enhanced utilization of biomass-derived chemicals for the generation of high value aromatics through an advanced catalytic strategy has captured considerable attention within the realm of eco-friendly manufacturing. This work presented four innovative three-dimensional rod-shaped mesoporous Ce-based MOF materials, which were coupled with a H-donor solvent to facilitate vanillin hydrodeoxygenation and macromolecular lignin. Under the optimized conditions (30 mg CoCe@C catalyst, 2 MPa N2 pressure, 15 mL isopropanol, 190 °C, and 5 h), the CoCe@C catalyst achieved nearly complete conversion of vanillin and demonstrated 87.8 % selectivity in the hydrogen-donor solvent. The characterization findings suggested that the synergy between metallic Co and oxygen vacancy sites enabled the effective activation of CHO group in vanillin, leading to formation of reactive product MMP. In addition, the optimal CoCe@C catalyst could also achieve macromolecular lignin hydrodeoxygenation to obtain high yield of lignin oil products with narrower molecular weight distribution. This study presented a viable approach for the concurrent utilization of lignin derivatives in the generation of high value fuels and chemicals.

Synthesis of palladium-decorated defective tungsten oxide heterostructures with enhanced photothermal catalytic activity for hydrodeoxygenation of vanillin

The selective hydrodeoxygenation (HDO) of sustainable lignocellulosic biomass plays a pivotal role in the conversion of biomass into high-value fuels and chemicals. Nevertheless, HDO for biomass upgrading always demands high temperatures and high hydrogen (H2) pressure. Photothermal catalysis has been recognized as an effective approach for boosting chemical reactions under mild conditions while maintaining superior selectivity. Herein, we report the design of palladium-decorated defective tungsten oxide (Pd/WO3-x) catalysts with enhanced photothermal catalytic performances for the efficient HDO of vanillin. Pd/WO3-x nanoflowers have been synthesized through a solvothermal/in-situ reduction two-step strategy, and they exhibit notable photoabsorption in a wide range (200–1100 nm), high photothermal conversion and efficient charge separation efficiency. Under simulated sunlight irradiation (0.3 W cm−2), Pd/WO3-x exhibits a maximum vanillin conversion up to 86.8 % with a 2-methoxy-4-methylphenol (MMP) selectivity of 100 %, which is obviously higher than that (vanillin conversion = 33.1 %, MMP selectivity = 100 %) in the oil bath at the same temperature. Such higher conversion efficiency and selectivity under sunlight should result from the synergistic integration of hot electrons and photothermal heating, both of which are derived from localized surface plasmon resonance (LSPR) in WO3-x. Importantly, Pd/WO3-x catalyst demonstrates good stability and high selectivity to MMP even after 5 cycles. This work may offer a novel viewpoint on the advancement of photothermal catalysts and the realization of photothermal catalytic biomass conversion under mild conditions.

Cover Feature: Ni Nanoparticles Supported Montmorillonite Clay for Selective Catalytic Transfer Hydrodeoxygenation of Vanillin into 2‐Methoxy‐4‐methylphenol (ChemCatChem 9/2024)

Cover Feature: Ni Nanoparticles Supported Montmorillonite Clay for Selective Catalytic Transfer Hydrodeoxygenation of Vanillin into 2‐Methoxy‐4‐methylphenol (ChemCatChem 9/2024)

Mesoporous organic resin supported palladium nanoparticles for efficient hydrodeoxygenation of vanillin

Resorcinol 1,4-phthalaldehyde resin (RPR) was successfully synthesized using a solvent-free self-assembly method employing a template (F127) and a mixture of resorcinol and 14-phthalaldehyde. After the removal of the template (F127) by heating, the PRR exhibited an ordered mesoporous structure with a size of approximately 5.8 nm. After impregnating with Pd species, a RPR supported Pd catalyst (Pd/RPR) was finally obtained, which demonstrated outstanding catalytic performance and good stability in the hydrodeoxygenation of vanillin. With an optimal catalyst, 100% conversion of vanillin and 96.7% selectivity for 2-methoxy-4-methylphenol were achieved under the reaction conditions of 2 MPa H2 in ethanol at 90 ℃ over 4 hours. The superior catalytic properties of Pd/RPR with high activity and stability are anticipated to be significant for future biofuel upgrades.

Enhanced Effect of Carbon for the Ni/T-Nb2O5 Catalyst on Vanillin Hydrodeoxygenation in the Aqueous Phase

Enhanced Effect of Carbon for the Ni/T-Nb₂O₅ Catalyst on Vanillin Hydrodeoxygenation in the Aqueous Phase

Efficient Atomically Dispersed Co/N-C Catalysts for Formic Acid Dehydrogenation and Transfer Hydrodeoxygenation of Vanillin.

Atomically dispersed catalysts have gained considerable attention due to their unique properties and high efficiency in various catalytic reactions. Herein, a series of Co/N-doped carbon (N-C) catalysts was prepared using a metal-lignin coordination strategy and employed in formic acid dehydrogenation (FAD) and hydrodeoxygenation (HDO) of vanillin. The atomically dispersed Co/N-C catalysts showed outstanding activity, acid resistance, and long-term stability in FAD. The improved activity and stability may be attributed to the high dispersion of Co species, increased surface area, and strong Co-N interactions. XPS and XAS characterization revealed the formation of Co-N3 centers, which are assumed to be the active sites. In addition, DFT calculations demonstrated that the adsorption of formic acid on single-atom Co was stronger than that on Co13 clusters, which may explain the high catalytic activity. The Co/N-C catalyst also showed promising performance in the transfer HDO of vanillin with formic acid, without any external additional molecular H2.

MOFs-derived carbon-covered nickel phosphide for catalytic transfer hydrodeoxygenation of lignin-derived vanillin

The catalytic transfer hydrodeoxygenation (CTH) of lignin and its derivates to biofuels and fine chemicals was a promising technology for efficient utilization of biomass. Herein, a series of MOFs derived carbon-covered Ni2P@C-x catalysts were successfully fabricated via chemical vapor deposition for the CTH of lignin-derived vanillin to produce 2-methoxy-4-methylphenol (MMP). Ni2P@C-3 catalyst exhibited an excellent CTH performance, obtaining nearly 100 % conversion of vanillin and 95 % yield of MMP under the conditions of 180 °C, 3 h, and 0 MPa N2 in an isopropanol environment. Based on characterization results, the high catalytic activity of Ni2P@C-3 catalyst was attributed to Niδ+ species owing to the electron transfer from Ni to P and the P-OH groups in Ni2P phase, which provided more Lewis acid sites and Brønsted acid sites. Moreover, the small particle size with high dispersion and surface carbon defects also promoted the CTH performance. This work could provide some useful insights for the hydrodeoxygenation of lignin and its derivatives in the future.

Hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol over in-situ reduced CuO/Al2O3 catalysts under mild conditions

A new method for the hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol (MMP) by in-situ reduced CuO/Al2O3 catalysts was developed. The CuO/Al2O3 catalysts with different CuO contents were prepared by simple wet impregnation and could provide complete vanillin conversion with 99 % MMP selectivity under mild conditions (120 °C, 0.5 MPa H2, 8 h). The results from XPS and H2-TPR characterizations of the CuO/Al2O3 catalysts suggested that CuO species had a strong interaction with the Al2O3 support, which was beneficial for the in-situ reduction of CuO to Cu+ and Cu0 species during the hydrodeoxygenation reaction. The synergistic effect of Cu+ and Cu0 species was believed to promote the hydrodeoxygenation of vanillin, in which Cu0 accounts for the hydrogenation reaction, while Cu+ is responsible for the adsorption of vanillin and 4-hydroxy-3-methoxybenzyl alcohol to facilitate the further dehydration of 4-hydroxy-3-methoxybenzyl alcohol. In addition, the CuO/Al2O3 catalyst could maintain high catalytic activity after three reaction cycles and showed versatility for various lignin derivatives. The development of this in-situ reduceable catalyst could provide a cost-effective approach for the upgrading of biomass derived products.

Ni Nanoparticles Supported Montmorillonite Clay for Selective Catalytic Transfer Hydrodeoxygenation of Vanillin into 2‐Methoxy‐4‐methylphenol

AbstractThe targeted catalytic transfer hydrodeoxygenation (CTHDO) of vanillin (VAN) to 2‐methoxy‐4‐methylphenol (MMP) holds promise as a noteworthy subject in the domain of bio‐oil utilization, offering potential as a future biofuel and finding versatile use in fragrances and pharmaceutical industry. In this study, stable, cost‐effective Ni nanoparticles supported on montmorillonite (MMT) clay was synthesized for eco‐friendly, alcohol‐mediated CTHDO of VAN to MMP. The Ni(10 %)/MMT catalyst achieved >99 % VAN conversion and 95.2 % MMP selectivity using isopropanol (IPA) as a solvent and hydrogen donor. Characterization encompassing PXRD, SEM, TEM, and XPS confirmed successful Ni integration onto MMT. NH3‐TPD, pyridine‐IR, and H2‐TPR analysis evaluated catalyst surface acidity and reducibility. The synergy between surface‐modulated acidity of MMT and Ni nanoparticles collectively facilitated IPA and VAN activation, driving CTHDO performance. The Ni(10 %)/MMT catalyst displayed sustained activity over five recycles. Its exceptional stability and performance underscore its potential as an eco‐friendly, sustainable, non‐noble transition metal‐based catalyst for the hydrogenating lignin bio‐oil model compounds, contributing to greener catalytic advancements.

Regulation of Ni valence state and synergistic effects of supports in the hydrodeoxygenation of lignin-derived vanillin using pseudoboehmite-supported Ni catalysts

ABSTRACT Preparing 2-methoxy-4-methylphenol (MMP) through the vanillin (VAN) route is a crucial step in the high-value utilization of lignin (VTM). In this study, a series of Ni/PB catalysts were synthesized using pseudoboehmite (PB) as a carrier. Changes in the valence states of Ni were induced through H2 activation, while the impacts of reaction temperature, initial pressure, and catalyst addition were investigated based on the VTM process. The results revealed that PB exhibited a distinct mesoporous structure (average pore size of 5.8 nm), with Ni loaded in small particles size (3.88 nm). Ni species on the catalyst existed in a + 2-valence state, undergoing a change after H2 activation, with an increase in Ni0 promoting enhanced activity. The Ni/PB-450 catalyst exhibited excellent activity at 250°C for 3 hours (VAN conversion and MMP selectivity > 99%), and the catalyst demonstrated good durability, maintaining 99.1% VAN conversion and 80% MMP selectivity after two cycles. Combining the characterization and experimental results, the etherification and hydrogenation of VAN were identified as the primary reaction pathways. This study aimed to provide a new avenue for the high-value utilization of lignin and its derivatives through controlled catalyst preparation.

Mesoporous Zirconium Oxides and Cobalt Oxides for Selective Hydrodeoxygenation of Vanillin

Mesoporous Zirconium Oxides and Cobalt Oxides for Selective Hydrodeoxygenation of Vanillin

Ni/Ce co-doping metal–organic framework catalysts with oxygen vacancy for catalytic transfer hydrodeoxygenation of lignin derivatives vanillin

Exploring an advanced catalytic strategy for the high value utilization of lignin derived chemicals into value-added aromatics has attracted tremendous sights for green manufacturing. In this paper, a series of bifunctional 3D rod-shaped mesoporous NiCe metal–organic framework catalysts coupling with hydrogen-donner solvent were reported for the hydrodeoxygenation of vanillin to obtain 2-methoxy-4-methylphenol. Under the optimal conditions, 3Ni-Ce/C catalyst realized the highest conversion of vanillin (>95.0 %) and selectivity of 81.4 % in the absence of additional hydrogen pressure. The characterization results indicated that the interaction of metallic Ni and CeO2 promoted the generation of Ni-CeO2-x interface and oxygen vacancies (Ov), which could efficiently adsorb and activate aldehyde group of vanillin to obtain reactive intermediates. And then metallic Ni sites activated the hydrogen-donner solvent to form adsorbed H atoms, which then spilled over to the adjacent Ov to stabilized reactive intermediates. Whereafter, bifunctional 3D rod-shaped mesoporous NiCe metal–organic framework catalysts achieved the hydrodeoxygenation upgrading of vanillin to obtain 2-methoxy-4-methylphenol. Density functional theory (DFT) calculations further revealed that the synergistic effect of Ni-CeO2 and oxygen vacancies promoted the activation and dissociation of aldehyde group bond in vanillin, enhanced the ability of protonation hydrogenolysis. Additionally, 3Ni-Ce/C catalyst displayed robust activity for no less than four recycles, which provided a feasible method for the build of simultaneous utilization of lignin derivates to value-added fuels and chemicals.

Fabrication modulation of lignin-derived carbon nanosphere supported Pd nanoparticle via lignin fractionation for improved catalytic performance in vanillin hydrodeoxygenation

Nano-lignin presents great potential in advanced carbon materials preparation since it integrates the advantages of nanomaterials as well the preferable properties of lignin (e.g. high carbon content and highly aromatic structure). Herein, lignin-derived carbon nanosphere supported Pd catalysts (Pd@LCNS) were prepared via a two-step carbonization of Pd2+ adsorbed lignin nanospheres (LNS) and applied in vanillin hydrodeoxygenation. The effect lignin heterogeneity on the synthesis of Pd@LCNS as well as its catalytic performance was further investigated through the synthesis of Pd@LCNS using three lignin fractions with different molecular weight. The results showed that the three Pd@LCNSs exhibited significant differences in the morphology of both carbon support and Pd nanoparticles. Pd@LCNS-3 prepared from high molecular weight lignin fraction (L-3) presented stable carbon nanosphere support with the smallest particle size (∼150 nm) and the highest Pd loading amount (3.78 %) with the smallest Pd NPs size (∼1.6 nm). Therefore, Pd@LCNS-3 displayed superior catalytic activity for vanillin hydrodeoxygenation (99.34 % of vanillin conversion and 99.47 % of 2-methoxy-4-methylphenol selectivity) at 90 °C without H2. Consequently, this work provides a sustainable strategy to prepare uniformly dispersed lignin-based carbon-supported Pd catalyst using high molecular weight lignin as the feedstock and further demonstrate its superior applicability in the selective transfer hydrogenation of vanillin.