Hydrodeoxygenation Of Guaiacol Research Articles

Production of Valuable Aromatics from the Hydrodeoxygenation of Guaiacol and Real Bio-Oil over Ni–Nb/HZSM-5 under Supercritical Ethanol

Production of Valuable Aromatics from the Hydrodeoxygenation of Guaiacol and Real Bio-Oil over Ni–Nb/HZSM-5 under Supercritical Ethanol

Insights into reverse oxygen spillover effect induced via CeO2 modulation to enhance the stability of CuCoOx catalysts in hydrodeoxygenation of biomass derivatives

In hydrodeoxygenation (HDO) reactions, the evolution of the chemical states of active species in the catalyst caused by the spillover effects greatly influences their catalyst performance. Herein, the HDO of guaiacol (GUA) over CuCoOx and CuCoCeOx catalysts synthesized by co-precipitation method was systematically investigated. During the HDO reaction of GUA, acid sites (Co(II)) facilitated the C-O bond (demethylation via -OCH3) cleavage, which was the rate-determining step. A series of characterizations and experimental results revealed that introducing CeO2 into the CuCoOx catalyst could enable the catalyst to undergo reverse oxygen spillover in the hydrogenation environment, promoting the regeneration of CoO in the catalyst. Therefore, the deactivation of the CuCoOx catalyst due to hydrogen spillover leading to CoO reduction could be avoided, and the catalyst stability improved. The present study methodically investigated the spillover effects induced by Cu and CeO2 and provided the theoretical basis for the structural design of heterogeneous catalysts.

Insights into reverse oxygen spillover effect induced via CeO2 modulation to enhance the stability of CuCoOx catalysts in hydrodeoxygenation of biomass derivatives

In hydrodeoxygenation (HDO) reactions, the evolution of the chemical states of active species in the catalyst caused by the spillover effects greatly influences their catalyst performance. Herein, the HDO of guaiacol (GUA) over CuCoOx and CuCoCeOx catalysts synthesized by co-precipitation method was systematically investigated. During the HDO reaction of GUA, acid sites (Co(II)) facilitated the C-O bond (demethylation via -OCH3) cleavage, which was the rate-determining step. A series of characterizations and experimental results revealed that introducing CeO2 into the CuCoOx catalyst could enable the catalyst to undergo reverse oxygen spillover in the hydrogenation environment, promoting the regeneration of CoO in the catalyst. Therefore, the deactivation of the CuCoOx catalyst due to hydrogen spillover and CoO reduction could be avoided, and the catalyst stability improved. The present study methodically investigated the spillover effects induced by Cu and CeO2 and provided the theoretical basis for the structural design of heterogeneous catalysts.

Vapour phase hydrodeoxygenation of Guaiacol using Ni/SBA-15 for bio-oil upgrading

Vapour phase hydrodeoxygenation of Guaiacol using Ni/SBA-15 for bio-oil upgrading

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.

Bimetallic Ni-Co catalyst for improving selectivity in transfer hydrogenation of phenolic compounds

The study investigated the transfer hydrogenation of guaiacol, anisole, phenol, and positional isomers of dimethoxybenezene using 2-PrOH as the H-donor over Ni, Co, and Ni-Co catalysts. The catalysts, which contained 5 wt% metal, were prepared by the deposition-precipitation method. The results showed that the catalysts had developed a pore structure and fine metal particles. The Ni and Ni-Co catalysts demonstrated exceptional activity in the transfer hydrogenation of phenolic compounds with a substrate to metal molar ratio of 100 to 1. Furthermore, the addition of Co to Ni significantly impacted the selectivity of transfer hydrogenation promoting hydrodeoxygenation of anisole and guaiacol.

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.

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.

Hydrodeoxygenation of lignin bio-oil model compounds and surrogate mixtures over zeolite supported nickel catalysts

Bifunctional catalysts based on nickel supported on ZSM-5 and BETA zeolites were studied in the hydrodeoxygenation of lignin derived model compounds as well as in surrogate mixtures simulating the light fraction of lignin fast pyrolysis bio-oil. A screening of the hydrodeoxygenation reaction conditions (temperature, time, H2 pressure, catalyst amount) was carried out using the simplest phenolic compound, phenol. As in real lignin bio-oils more complex phenolic compounds are present, a series of relevant alkyl- and methoxy-substituted phenol and benzene (o- and m-cresol, catechol, anisole, guaiacol, syringol, creosol and 1,2,3-trimethoxybenzene) were also investigated as feedstocks. Furthermore, the effect of the different porous and acidic properties of the zeolitic supports was investigated in the hydrodeoxygenation of guaiacol. The conversion of the model phenolics and the yield of the respective (alkyl)cyclohexanes at relatively mild conditions (220 °C, 50 bar H2, 1 h) were in the range of 80–100% and 47–83%, respectively, being dependent mainly on the complexity/side-chain group of the phenolic/benzylic ring and on the balanced content of Brønsted acid sites of increased strength. Regarding the hydrodeoxygenation of the surrogate mixture (C7-C10 phenolics), 100% hydrodeoxygenation efficiency was achieved towards >60% yield of (alkyl)cyclohexanes (C6-C9 hydrocarbons). All hydrodeoxygenation tests were conducted in hexadecane as solvent/substrate in order to simulate model co-processing (i.e. bio-based phenolics with petroleum derived feedstocks) conditions. Reusability tests revealed the stability of the catalysts which showed partial (30%) deactivation after the third catalytic cycle.

Catalytic potential of green ordered mesoporous carbons, obtained from biomass-derived xylose, glucose, and lignin

Green high-surface area Ordered Mesoporous Carbons (OMCs) (576–948 m2/g) were successfully synthesized by the hard template method using xylose, glucose and lignin solutions obtained from almond shells, a local biomass waste, as carbon precursors, and SBA-15 as a template. The catalytic potential of OMCs, as catalytic supports or as catalysts, has been preliminarily tested for different reactions of interest. A dried sulfonic-acid treated OMC, obtained from xylose extract, led to full conversion and 92% selectivity to di- and tri-ethers of glycerol for the glycerol etherification with isobutene at 80 °C. A sulfonic-acid treated OMC, obtained from glucose, presented a higher turnover frequency (TOF) value and slightly lower selectivity to levulinic acid than commercial Amberlyst-15 for the conversion of 5-hydroxymethylfurfural at 180 °C. The use of an OMC obtained from lignin as catalytic support of a nickel catalyst combined with H-Beta led to 78% of selectivity to cyclohexane at total conversion for the hydrodeoxygenation of guaiacol at 180 °C.

A highly dispersed Co/SiO2–Al2O3 catalyst for hydrodeoxygenation of guaiacol to cyclohexane

A highly dispersed Co/SiO2–Al2O3 catalyst for hydrodeoxygenation of guaiacol to cyclohexane

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.

Selective hydrodeoxygenation of guaiacol to cyclohexanol using activated hydrochar-supported Ru catalysts

Selective hydrodeoxygenation of guaiacol to cyclohexanol using activated hydrochar-supported Ru catalysts

Catalytic conversion of guaiacol to phenol and alkylphenols over Mo-promoted Ni/CeO2 catalyst in supercritical ethanol

The study explored the catalytic hydrodeoxygenation (HDO) of guaiacol using nickel-loaded cerium oxide (Ni/Ce) and molybdenum-promoted Ni/Ce (Mo-Ni/Ce) catalysts in supercritical ethanol. The use of Mo-Ni/Ce at 300 °C maximized H2 production, guaiacol conversion (84.1%), and deoxygenation compared to Ni/Ce. Mo-Ni/Ce also achieved the highest efficiency for producing desired products, resulting in 7.8% phenol and 29.0% alkylphenols selectivities. Mo-Ni/Ce's better efficiency stemmed from enhanced ethanol dehydrogenation, H2 dissociation and spillover, and accelerated HDO reactions owing to improved Ni dispersion and catalyst oxygen vacancies. Testing different Ni and Mo loading amounts revealed the optimum catalyst efficiency when using 20% Ni and 5% Mo (5Mo-20Ni/Ce). Temperature optimization with 5Mo-20Ni/Ce increased guaiacol conversion (up to 95.6% at 340 °C) and yielded more phenol (27.4%) and alkylphenols (66.1%). DFT calculations revealed that adding molybdena clusters notably reduced the energy required for creating oxygen vacancies, indicating enhanced catalytic properties for oxygen vacancy generation in 5Mo-20Ni/Ce.

Hydrodeoxygenation of mixtures of biomass-derived model compound oxygenates over Pt/HY catalysts

In this study, a systematic analysis of the effect of three biomass pyrolysis oxygenates, viz., acetic acid, cyclopentanone and furfural, on the hydrodeoxygenation (HDO) of guaiacol is performed. Bifunctional Pt/HY catalysts with different Si/Al ratios were screened for the HDO of guaiacol. Guaiacol conversion and the cyclohexane yield increased with the concentration of acid sites in the zeolites. The presence of acetic acid and cyclopentanone did not affect the guaiacol conversion and the product selectivity, while guaiacol conversion decreased significantly in the presence of furfural. The effects of temperature, reaction time, and the guaiacol-furfural molar ratio on the HDO of guaiacol were studied. The time evolution of products showed that the furan ring opening influences the conversion of guaiacol.Quantum chemicaldensity functional theorycalculations using individual and binary model compounds revealed the decrease in adsorption energy of guaiacol over Pt (111) in the presence of furfural.

Selective hydrodeoxygenation of guaiacol to phenol over CoFe/reduced graphene oxide

A reduced graphene oxide (rGO)-supported CoFe bimetallic catalyst (CoFe/rGO) was synthesized and used for hydrodeoxygenation of guaiacol to phenol (Ph). The CoFe/rGO catalyst without reduction pretreatment showed excellent catalytic performance, achieving 94.0 mol% conversion and 70.8 mol% selectivity to Ph at mild reaction temperature and low H2 pressure. The microstructure and chemical composition of the CoFe/rGO catalyst were characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and H2 temperature-programmed reduction (H2-TPR) characterization analysis. Co and Fe are supported on rGO in forms of the isolated metal atoms embedded in the rGO matrix and the CoFe oxide nanoparticles attached on rGO surface. Fe as a promoter weakens the hydrogenation activity of Co to benzene ring and dramatically improves the selectivity to Ph. The unique of rGO on constructing catalytic active sites and the synergistic effect of Co and Fe bimetals make CoFe/rGO an excellent catalyst.

Hydrodeoxygenation of guaiacol over physically mixed Co/TiO2 and WO3/TiO2 catalysts

The physically mixed Co/TiO2 and WO3/TiO2 catalysts exhibited excellent catalytic performance in the hydrodeoxygenation of guaiacol, and the deactivated catalyst could be successfully regenerated after magnetic separation.

Regulation of surface hydrophobicity and metal dispersion on Pt-based catalyst for the boosted hydrodeoxygenation of guaiacol into bio-hydrocarbons

Transformation of lignin-derived feedstocks into valuable hydrocarbons is of significant importance but still challenging. This work investigates the hydrodeoxygenation (HDO) of lignin compound guaiacol on Pt-based catalysts with improved surface hydrophobicity and metal dispersion for the first time. The efficiency of guaiacol hydrodeoxygenation into hydrocarbons over Nb2O5-modified Pt-based catalyst reaches 51 %, nearly doubling that over unmodified Pt/γ-Al2O3 catalyst (25 %). On the one hand, Nb2O5 causes the decrease of hydroxyl groups on catalyst, leading to the enhanced hydrophobicity of catalysts, which increases the reaction rate of guaiacol into hydrocarbons on unit of Pt metal sites. On the other hand, Nb2O5 strengthens the metal-support interaction, which minimizes the size of Pt nanoparticles, providing more exposed metal sites, thus leading to a higher hydrocarbons yield on catalyst. However, excess introduction of Nb2O5 leads to partial coverage of Pt metal sites, resulting in decreased yield of hydrocarbons. Furthermore, the routes of guaiacol HDO reaction over modified Pt-based catalysts are investigated. This work further illustrates the influence of catalyst surface properties on the HDO process of lignin compound, and thereby provides a promising approach for adjustment of catalyst surface properties in order to promote water-liberated reactions.

A Cu-ZnO-Al2O3 catalyst with oxygen vacancy for efficient hydrodeoxygenation of lignin-derived guaiacol to hydrocarbons

This study explores the efficacy of a cost-effective Cu-ZnO-Al2O3 catalyst for one-pot hydrodeoxygenation of guaiacol into hydrocarbons. Notably, complete conversion of guaiacol was achieved, yielding a 99.6% hydrocarbon over the robust Cu(6)Zn(3)Al(1) catalyst under the conditions of 4 MPa H2, 300 °C, and 8 h with a catalyst/guaiacol ratio of 0.5 g/1.0 g. In-depth catalyst characterizations unveiled the presence of oxygen vacancies within the ZnO surface layer, acting as pivotal active sites that facilitated the hydrodeoxygenation of guaiacol. Furthermore, Density Functional Theory (DFT) calculations were employed to evaluate several potential active sites, revealing that the oxygen vacancy of ZnO on the Cu surface played a crucial role. This vacancy enhanced the adsorption of intermediate cyclohexanol and markedly reduced the energy barrier for the rate-limiting step. This comprehensive investigation sheds light on the catalytic pathway and offers insights into designing efficient and sustainable biofuel production processes.

Hydrodeoxygenation of guaiacol to bio-hydrocarbons in alkaline condition on the Ni/AC catalyst with an “acid-switch”

Due to the mass manufacturing of global papermaking black liquor, lignin remained in strong-alkaline black liquor is a promising raw material for bulk hydrocarbons production with huge carbon–neutral value. In this work, the alkaline in reactant is proved to inhibit the hydrodeoxygenation reaction of guaiacol severely due to the formation of phenates and cyclohexadienones. A hydroxyl interventional Ni/AC catalyst, on which an “acid-switch” is built with combination of hydroxyl groups and Ni nanoparticles, achieves 4-fold bio-hydrocarbons yield in alkaline condition compared to conventional Ni/AC catalyst. It is implied that hydroxy groups promote the C(sp2)-O reaction route with the aid of activated hydrogen on Ni nanoparticles, while acidic groups on catalyst reduce the size of Ni nanoparticles, thus further enhances the HDO efficiency. It is the first time we propose a reaction mechanism of HDO of guaiacol on Ni-based catalyst in alkaline condition to give insight into HDO reaction of lignin compounds in black liquor. This work gives insights into the relationship between catalyst surface properties and HDO efficiency, and provides a promising approach for green utilization of lignin in alkaline black liquor.