Hydrodeoxygenation Of Phenol Research Articles

Efficient C–O Bond Hydrogenolysis Over Polyoxometalate Catalysts in Mild Hydrodeoxygenation of Lignin-Derived Phenols to Cycloalkanes

Efficient C–O Bond Hydrogenolysis Over Polyoxometalate Catalysts in Mild Hydrodeoxygenation of Lignin-Derived Phenols to Cycloalkanes

Efficient hydrodeoxygenation of lignin-derived phenolics to cyclohexanol with N-doped alumina- carbide‐based RuCo catalysts derived from MOF under mild conditions

In this work, a novel RuCo bimetallic supported on N-doped carbon support containing alumina was prepared by in-situ pyrolysis using MOF-303 as the support precursor (Ru3Co1@CN-Al2O3), and it was applied to the efficient hydrodeoxygenation (HDO) of guaiacol under mild conditions (0.01 MPa H2, 200 °C, 3h), the yield of cyclohexanol reaches an impressive 83.12 %. In the absence of external hydrogen (2 MPa N2, 220 °C, 2 h), complete conversion of guaiacol was achieved, along with a remarkable 97.81 % selectivity towards cyclohexanol. The HDO of guaiacol under different atmospheres was further studied, and the possible mechanism was proposed. Characterization results indicated that the supported metals (Ru and Co) not only interacted with the N in the MOF-303 to enhance catalyst stability but also that the synergistic effect between Ru and Co was key to promoting the high yield of cyclohexanol through catalytic transfer hydrodeoxygenation (CTHDO) in isopropanol. Additionally, Ru3Co1@CN-Al2O3 was also effective in achieving the HDO of macromolecular lignin. This study provides a feasible approach for the high value-added green transformation of lignin and its derivatives under mild conditions, highlighting the significant potential of MOFs for lignin valorization.

Phyllosilicate-derived Ni/SiO2 catalyst for liquid-phase hydrodeoxygenation of phenol: Synergy of Lewis acid sites and Ni0

Designing effective catalysts using non-noble metals for bio-oil hydrodeoxygenation (HDO) into liquid fuels is greatly sought after, yet it remains a great challenge. Contrary to the prevailing belief that monometallic nickel lacked activity in the HDO of oxygen-containing compounds, this study demonstrates a remarkable catalytic performance over monometallic Ni catalyst. Herein, a Ni/SiO2 catalyst having both nickel phyllosilicate and Ni0 was synthesized by the ammonia evaporation (AE) method. The Ni-PS-400 catalyst reduced at 400 ℃ achieves a significant high activity and yields 97 % cyclohexane at a low reaction temperature of 190 ℃, surpassing both Ni-IMP-400 prepared by impregnation method and most of the reported other non-noble metal catalysts which are generally used at high temperature of above 240 ℃. It was found that the reduction temperature of Ni-PS-X influences the catalytic activity, as more dispersed Ni nanoparticles and acidic sites can be produced on the surface of the support at an appropriate temperature. The outstanding catalytic performance can be ascribed to the collaborative effect of well-scattered Ni nanoparticles and the significant presence of Lewis acidic sites, which result from coordinatively unsaturated Ni2+ sites situated within the remaining nickel phyllosilicate.

Role of solvent in selective hydrodeoxygenation of monomeric phenols

The current production of aromatic hydrocarbons, crucial in fuel and polymer production, relies heavily on fossil resources. Finding carbon-neutral alternatives is necessary to address the current environmental challenges. Lignin emerges as a promising source for bio-based aromatics. However, existing catalytic hydrodeoxygenation processes often yield mixtures of cycloalkanes and aromatics. In our study, we investigated a selective route to obtain aromatics from phenols using the keto-tautomer reaction mechanism. According to this mechanism, the initial hydrogenation of the carbonyl group while a phenol compound is in its keto form leads to the removal of the hydroxyl group while preserving the aromatic structure. Our experiments focused on p-cresol, guaiacol, and mequinol, employing Pd/C and Ru/C catalysts. Experimental results revealed that aromatic hydrocarbons were favored during the hydrodeoxygenation of p-cresol and mequinol, while steric effects from the methoxy group hindered guaiacol's conversion. Furthermore, we observed significantly higher conversion rates when using hydrocarbon solvents compared to water, with toluene yields of up to 13.5 % by mass achieved on Pd/C. Our computational simulations confirmed the feasibility of the keto-tautomer mechanism on Pd cluster surfaces, similar to those found in Pd/C catalysts.

The Hydrodeoxygenation of Phenol over Ni-P/Hβ and Ni-P/Ce-β: Modifying the Effects in Dispersity and Acidity

The Hydrodeoxygenation of Phenol over Ni-P/Hβ and Ni-P/Ce-β: Modifying the Effects in Dispersity and Acidity

La-Modified SBA-15 Prepared by Direct Synthesis: Importance of Determining Actual Composition

Lanthanum (La) integration (at various nominal contents) in SBA-15 prepared under acidic medium was intended from corresponding direct nitrate addition during mesoporous silica formation. Materials were impregnated with Pt (1.5 wt%) and studied through several textural (N2 physisorption), structural (XRD, TG-DTG), and surface (FTIR, STEM-HAADF, SEM-EDS, NH3, and CO2 TPD) instrumental techniques. Pt-impregnated solids were tested in phenol hydrodeoxygenation (HDO, T = 250 °C, 3.2 MPa, batch reactor, n-decane as solvent). Catalytic activity (in pseudo-first-order kinetic constant, kHDO basis) was not directly related to Pt dispersion, which was not determined by nominal rare earth content. Determining the actual composition of modified SBA-15 materials is crucial in reaching sound conclusions regarding their physicochemical properties, especially when La modifier is directly added during mesoporous matrix formation, where efficient interaction among constituents could be difficult to get. Otherwise, results from some characterization techniques (N2 physisorption and FTIR, for instance) could be misleading and even contradictory. Indeed, extant modifier precursors, when under SBA-15 synthesis conditions, could affect the properties of prepared materials even though they were absent in obtained formulations. Performing simple compositional analysis could eliminate uncertainties regarding the role of various modifiers on characteristics of final catalysts. However, several groups have failed in doing so.

Lignin-incorporated Co-MOFs-derived catalysts for selective hydrodeoxygenation of lignin-derived phenols into cyclohexanols

Lignin accounted for the second largest amount in biomass, and was regarded as an important carbon source and important renewable source for value-added chemicals. Herein, a series of lignin-derived carbon-based heterogeneous catalyst was synthesized through a simple hydrothermal method, using Co-MOFs as template. Lignin was introduced as a carbon material into MOF catalysts. Through some characterizations, it has been proven that lignin has been successfully introduced into MOF materials and significantly improved the catalyst performance. Then, lignin-MOF derived catalysts (Co/C-EL-X) were successfully introduced into the catalytic hydrodeoxygenation of lignin-derived phenols. The addition of enzymatic hydrolysis lignin (EL) in catalysts, calcination temperature and some other factors were investigated in detail, considering the catalytic performance during the HDO of vanillin and other typical lignin-derived phenols. Co/C-EL-0.5(500) exhibited the best catalytic performance for the conversion of different kinds of lignin-derived phenols to either 2-methoxy-4-methylphenol (MMP) or cyclohexanol. Under the optimal conditions of 240 °C, 0 MPa N2, and 2 h, the conversion rate of vanillin reached 100 %, and the yield of 4-methyl-2-methoxyphenol (MMP) was up to 92 %. Furthermore, vanillin could also be converted into 4-methylcyclohexanol (MCYL) by changing the initial nitrogen pressure. Also, Co/C-EL-0.5 (500) exhibited high activity for the conversion of other lignin-derived phenols into cyclohexanol (COL). This work provided a novel strategy for the catalytic valorization of lignin sources.

N-doped MOF-lignin hybrid catalyst for highly selective hydrodeoxygenation of lignin-derived phenols

Upgrading of lignin-derived bio-oil to value-added biofuel was of great significance for efficient utilization of renewable resources and reducing the use of fossil fuels. Hydrodeoxygenation (HDO) was considered to be a promising technology for the conversion of lignin-derived bio-oil. Herein, we reported a novel method for the preparation of lignin-MOF derived N-doped catalysts, which was then successfully introduced into the upgrading of lignin-derived phenols and lignin depolymerization. All catalysts were well characterized and Co/CN-0.5–750 exhibited excellent performance during the catalytic HDO process. The optimized catalyst demonstrated highly efficient active hydrogen generation from isopropanol. Moreover, it could afford the best vanillin (VAN) conversion (100 %) and highest 2-Methoxy-4-methylphenol (MMP) yield (92 %) under the mild reaction conditions (180 °C, 0.5 MPa nitrogen, 2 h). It was confirmed that the excellent performance was related to nitrogen doping. This study could provide some useful insights for the hydrodeoxygenation of lignin and its derivative.

Ce-Doped Co-ZIF as an efficient catalyst for hydrodeoxygenation of lignin-derived phenols: From guaiacol to cyclohexanol

Through the utilization of diverse technological processes, lignin could be transformed into a multitude of valuable chemicals and fuels. This transformation not only reduces our dependence on fossil energy but also fosters the promotion of environmental sustainability. In this study, Ce metal was incorporated into the zeolite imidazolium framework-67 (ZIF-67) using the impregnation method to prepare a series of bimetallic catalysts. Using isopropanol solvent as the hydrogen source, guaiacol was effectively converted to cyclohexanol with over 80.0% selectivity over the optimum catalyst at 240 °C, 1.5 MPa N2, for 4 hours. The prepared catalysts were subjected to characterization methods such as BET, SEM, XPS, TEM, XRD, H2-TPR and NH3-TPD. The results of the characterization show that the addition of Ce changed the zeolitic imidazolium ester backbone structure of ZIF-67 and encouraged the emergence of more oxygen vacancies, which strengthened the catalyst hydrodeoxygenation activity and reducibility. Based on the findings of the catalytic performance tests and a retesting, the reaction pathway of the guaiacol hydrodeoxygenation process was suggested.

Al-MIL-53 metal-organic framework supported Ru catalyst for selective hydrodeoxygenation of lignin-derived phenols into cyclohexane

Catalytic hydrodeoxygenation (HDO) of guaiacol, as a bio-oil model compound, was investigated employing Ru/Al-MIL −53 Metal-Organic Framework and Ru/γ-Al2O3 catalysts under external molecular hydrogen. Notably, the HDO results attributed the remarkable potential of the Ru/Al-MIL −53 MOF toward the comparatively high conversion of guaiacol (70%) together with a high proportion of cyclohexanol (23%) at a catalyst/feed (C/F) ratio of 1:5. However, only a 30% conversion was found with only 3.5% cyclohexanol for Ru/γ-Al2O3 for the same C/F ratio. This was due to the high porosity and presence of numerous vacancies in the MOF, which directly affects the H2-dissociation/ spillover that assists the transfer of produced H-radicals for further conversion of the adsorbed guaiacol molecules. Notably, the activity of Ru/Al-MIL −53 was remarkably increased by decreasing the amount of guaiacol. The maximum conversion was achieved (100%) for a C/F ratio of 1:1, with a higher (96.2%) selectivity for cyclohexane. The reusability test for the spent catalyst did not show any significant change in catalyst performance for up to five successive cycles.

Selective Hydrodeoxygenation of Phenol Driven by Synergistic Effects of Dual-Metal Atoms Over C2N Monolayer

Selective Hydrodeoxygenation of Phenol Driven by Synergistic Effects of Dual-Metal Atoms Over C₂N Monolayer

A first-principles study on the hydrodeoxygenation mechanism of the lignin-derived phenolic compounds over MoS2 catalysts

Understanding the hydrodeoxygenation (HDO) mechanism of phenolic compounds is crucial for advancing catalytic upgrading techniques of bio-oil. Herein, a comprehensive theoretical study of the HDO of lignin-derived phenolic compounds (phenol, cresols, and guaiacol) on the MoS2 surface was carried out using periodic density functional theory (DFT) calculations. Adsorption of phenolic compounds on different crystal faces was first compared. The MoS2 (100) crystal face is more favorable for the adsorption of phenolic compounds which show the horizontal adsorption configurations. Three kinds of HDO patterns were explored for the phenolic compounds. Phenol tends to transform into benzene via stepwise deoxygenation and hydrogenation under the induction of active hydrogen. For cresol isomers, their HDO mechanisms differ from each other due to the influence of the methyl group on the dehydroxylation process. Specifically, o-cresol follows a synergistic process of deoxidation and hydrogenation, m-cresol undergoes a two-step reaction involving direct dehydroxylation and hydrogenation, and p-cresol involves the identical HDO pathway as phenol. With regard to guaiacol, the preferred HDO route involves successive dehydroxylation and demethoxylation to benzene with the anisole intermediate. In addition, the adsorption of phenolics over transition metal-doped MoS2 catalysts was further explored to examine the potential of metal doping for the HDO of phenolics. The doping of Ta and W increases the adsorption capacity, which shows the potential to enhance the HDO activity of the catalyst theoretically.

Aqueous Phase Hydrodeoxygenation of Phenol on Hβ Zeolite Supported NiCo Alloy Catalysts

Aqueous Phase Hydrodeoxygenation of Phenol on Hβ Zeolite Supported NiCo Alloy Catalysts

Hydrodeoxygenation of lignin-derived phenols into cycloalkanes by atomically dispersed Pt-polyoxometalate catalysts

We report atomically dispersed Pt sites anchored on polyoxometalate cesium salts as robust and durable catalysts for upgrading lignin into hydrocarbons at relatively mild conditions. Experimental results and DFT calculations cross-validate the catalytic performance, considering the porosity, acidity, H2 storage capacity, and HOMO-LUMO energy gap of these catalysts. The optimal Pt0.4/CsPW-H2 catalyst enables the hydrodeoxygenation (HDO) of a diverse range of lignin-derived phenolics into hydrocarbons with up to 97% yield at the conditions of 150 °C and 0.1–2 MPa H2. A lignin oil from the reductive catalytic fractionation (RCF) of Eucalyptus wood can be transformed into cyclohexanes with a 32.7 wt% yield under a solvent-free condition. This catalyst demonstrates excellent reusability in the HDO of 4-propyl guaiacol for 20 cycles, achieving a 15095 molpropylcyclohexane molPt−1 total turnover number (TON). This work broadens the horizons of designing highly efficient catalytic systems aimed at sustainably producing liquid fuels from lignin.

Cs-promoted hydrogenation upgrading of bio-oil over macroporous Ru-containing catalysts using model compounds

Hydrogenation upgrading is an effective technique that lowers the oxygen content of bio-oil with the aim of improving its quality. In order to fabricate a series of Ru-based catalysts for the hydrodeoxygenation of bio-oil, several all-silica supports with different pore sizes are synthesized and modified with Al and Cs in this work. The physical morphology and electronic structure of the catalysts are characterized using multiple techniques including X-ray diffraction, in-situ pyridine adsorption infrared spectroscopy, in-situ diffuse reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, CO2 temperature-programmed desorption, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and N2 physical adsorption-desorption testing. Phenol, guaiacol, anisole and o-cresol are selected as model compounds to investigate the hydrodeoxygenation reactivity of the catalysts. The results reveal that there is a strong linear correlation between the pore size of the catalysts and the rates of the hydrogenation and hydrodeoxygenation of phenol. Importantly, both the oxygen vacancy density and relative content of Brønsted and Lewis sites (B/L) of the catalysts can be greatly increased by Cs modification, which further linearly promotes the hydrodeoxygenation activity of the catalysts. In addition, the in-situ infrared spectroscopy results show that the catalysts modified by Al and Cs heterolytically cleave H2 to supply H+ for the reaction. This work presents a novel approach for fabricating catalysts employed in the hydrotreatment process of bio-oil.

Engineered Ru on HY zeolite catalyst for continuous and selective hydrodeoxygenation of lignin phenolics to cycloalkanes under moderate conditions

We report a continuous selective hydrodeoxygenation (HDO) process of guaiacol conversion to cycloalkanes under 180 °C/1 MPa, which results in improved HDO chemistry for lignin-based jet fuel production. The incipient wetness impregnation method was modified to prepare an HY zeolite-supported Ru catalyst with better metal dispersion and acid site uniformity, which overcomes the low conversion and selectivity of previous literature. The modified catalyst (Ru-HY-60-MI) was tested in a continuous fixed bed reactor, resulting in increased HDO conversion of guaiacol to cycloalkanes compared to the unmodified catalyst. Pressure, temperature, and weight hourly space velocity-dependent tests validate guaiacol HDO over Ru-HY-60-MI catalyzed ring hydrogenation of guaiacol to 2-methoxycyclohexanol, acid-catalyzed demethoxylation and dehydration to cyclohexene, and further hydrogenation of cyclohexene to cyclohexane. These experiments enable exploring a continuous HDO process, demonstrate effectiveness for other β-β and α-O-4 lignin representatives and real lignin bio-oil, and pave the way towards commercialization of lignin-based jet fuel.

Bifunctional metal–acid sites on nickel boride catalysts: Phenol hydrodeoxygenation and water-promoted C = C hydrogenation

Modification of earth-abundant metal catalysts with optimized catalytic performance can be potential alternatives to precious metal catalysts for more sustainable processes. Using a chemical reduction method, nickel boride (Ni3B) alloy catalysts were prepared with a Ni/B ratio of 3. Ex-situ and in-situ characterization indicates that the structure of Ni3B changes from amorphous to crystalline with increasing pretreatment temperatures. The presence of B does not seem to alter the electronic properties of Ni. However, after pretreatment, oxidized B species (i.e., BOx and H3BO3) ex-solve from the bulk, leading to the formation of a B-enriched surface. In-situ titration and dehydration reaction experiments demonstrate the presence of acid sites, which play an important promoting role in the hydrogenation of C = C bonds. Moreover, Ni3B catalysts show a remarkable activity towards phenolic ring hydrogenation with the added ability to deoxygenate the secondary products via dehydration on the acid sites. Under water-free reaction conditions, the Ni3B catalysts exhibit similar hydrogenation activity to that of a pure Ni catalyst. Remarkably, the addition of small amounts of water leads to a > 100-fold increase on Ni3B catalysts, while it inhibits the reaction on bare Ni catalyst by blocking active sites. These observations highlight the cooperative role of bifunctional sites in Ni3B catalysts and solvent composition for C = C hydrogenation reactions.

Environmentally friendly and innovative design of ZIF-67 and lignin modified composites for efficient catalytic transfer hydrodeoxygenation of lignin-related phenols

Exploring lignin depolymerization and modification can yield high-value chemicals and liquid fuels, thereby enhancing resource utilization efficiency and alleviating pressure caused by energy shortages.

Effect of Pt and Ru-based catalysts on the electrochemical hydrodeoxygenation of phenol to cyclohexane

PtRuC offers the opportunity to electrochemically convert bio-oils to drop-in biofuels and platform chemicals. Here we demonstrate the concept using phenol to cyclohexane as a model reaction.

Highly efficient Co-based catalysts supported on K-modified alumina for selective hydrodeoxygenation of lignin-derived phenols to alkyl cyclohexanols

Highly efficient Co-based catalysts supported on K-modified alumina for selective hydrodeoxygenation of lignin-derived phenols to alkyl cyclohexanols