Hydrodeoxygenation Of Phenol Research Articles

Boosted Hydrodeoxygenation of Lignin-Derived Phenolics to Cycloalkanes with a Complex Copper Acid Catalyst

Boosted Hydrodeoxygenation of Lignin-Derived Phenolics to Cycloalkanes with a Complex Copper Acid Catalyst

Hydrodeoxygenation of lignin-derived phenolics over facile prepared bimetallic RuCoNx/NC

Cyclohexanols, promising oxygenated fuel additives and value-added chemicals, can be obtained by hydrodeoxygenation (HDO) of lignin-derived phenolics. Here, an N-doped bimetallic RuCoNx/NC catalyst was facilely prepared for HDO by direct pyrolysis of chitin impregnated with precursors of Ru and Co. Characterization of RuCoNx/NC with N2 sorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and NH3 temperature-programmed desorption (NH3-TPD) reveal that the metallic particles of electron-deficient Ru species and electron-enriched Co species were uniformly anchored on the micro-mesoporous N-doped carbon matrix with high dispersion and nano-scale size. The abundant accessible active sites and continuous spillover of H from Ru to Co make RuCoNx/NC an excellent HDO catalyst. 4-Propylguaiacol, a typical phenolic compound from lignin degradation, was hydrodeoxygenated into 92% 4-propylcyclohexanol over RuCoNx/NC at 210 ℃. With temperature increasing, propylcyclohexane became the major product, possessing 95% selectivity at 280 °C after 6 h. Reusability tests show that RuCoNx/NC can be recycled four times without the loss of conversion and initial selectivity. HDO of other phenolic compounds confirms the general applicability of RuCoNx/NC.

In Situ Hydrodeoxygenation of Lignin-Derived Phenols With Synergistic Effect Between the Bimetal and Nb2O5 Support

Nb2O5-supported bimetallic catalysts were prepared by the impregnation method applied for the in situ hydrogenation of guaiacol. Guaiacol can be effectively transformed into cyclohexanol over different bimetallic catalysts using alcohol as the hydrogen donor. Meanwhile, the effects of different hydrogen donors such as isopropanol, sec-pentanol, and ethylene glycol on in situ hydrogenation of guaiacol were investigated in detail, and the results showed that isopropanol is the best hydrogen supply solvent. Then, the dependence of Ni–Mn/Nb2O5 properties on metal loading, reaction time, reaction temperature, and reaction pressure was studied for the in situ hydrogenation of guaiacol by using isopropanol as the hydrogen donor. Guaiacol can be completely converted, and the yield of cyclohexanol reached 71.8% over Ni–Mn/Nb2O5 with isopropanol as the hydrogen donor at 200°C for 5 h. The structures and characteristics of better catalytic properties of the Ni–Mn/Nb2O5 catalyst were determined by BET, NH3-TPD, XRD, XPS, SEM, and TEM, and the results indicated the particle size of the metal was small (approximately 10 nm) and the metal particles are finely dispersed in the whole support. Therefore, a large number of medium acid sites were generated on the 10Ni-10Mn/Nb2O5 with a large specific surface area, which could increase the interface between the metal and the support and may be beneficial to the hydrodeoxygenation of guaiacol.

Elucidating the Active Site and the Role of Alkali Metals in Selective Hydrodeoxygenation of Phenols over Iron-Carbide-based Catalyst.

Iron-carbide-based catalysts have been explored in the selective hydrodeoxygenation (HDO) of phenol, aiming at elucidating the role of active site and alkali metal. Complementary characterization such as X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and scanning transmission electron microscopy coupled with electron energy loss spectroscopy, together with catalytic evaluations revealed a rapid structural reconstruction of iron carbide (Fe3 C) catalysts, leading to a stable defective graphene-covered metallic Fe active phase (G@Fe) under reaction conditions. Further studies using different alkali metals (i. e., Na, K, and Cs) revealed that alkali metals showed negligible effect on the phase transformation of Fe3 C. However, the reconstructed G@Fe doped with alkali metals inhibited the tautomerization, a facile reaction pathway to saturation of the aromatic ring, leading to enhanced selectivity to arene. The extent of inhibition of tautomerization or selectivity to arene was closely related to the degree of electron donation of alkali metal to Fe.

Regulating the nanoscale intimacy of metal and acidic sites in Ru/γ-Al2O3 for the selective conversions of lignin-derived phenols to jet fuels

Catalytic hydrodeoxygenation (HDO) of biomass-derived oxy-compounds to advanced hydrocarbon fuels usually requires bifunctional catalysts containing metals and acidic sites. The appropriate tuning of metal and/or acidic active sites at interfaces of bifunctional catalysts can significantly improve catalyst activity and product selectivity. Here, 4-trifuoromethyl salicylic acid (TFMSA), as a hydrothermal stable organic acid, was employed to tailor the bifunctional interface of Ru/γ-Al2O3 to enhance the catalytic performance on converting lignin-derived phenols to jet fuel range cycloalkanes. More than 80% phenol was converted into cyclohexane at 230 °C for 1 h over Ru/γ-Al2O3 modified by TFMSA, which was about three times higher than that over unmodified Ru/γ-Al2O3. X-ray diffraction (XRD), Transmission electron microscope (TEM), H2 chemisorption, and energy dispersive X-ray spectroscopy (EDS) elemental mapping results indicated that Ru nanoparticles and TFMSA were well distributed on γ-Al2O3, and a nanoscale intimacy between Ru and TFMSA was reached. Meanwhile, Fourier transform infrared spectroscopy after pyridine adsorption (Py-FT-IR) analysis proved that Brønsted acidic sites on the catalytic interfaces of TFMSA modified Ru/γ-Al2O3 had been improved. Moreover, the kinetic and density functional theory (DFT) results suggested that the synergistic effects of adjacent Ru nanoparticles and acidic sites were crutial for promoting the rate-limiting conversion step of phenol HDO to cyclohexane.

Selective hydrodeoxygenation of lignin-derived phenolics to cycloalkanes over highly stable NiAl2O4 spinel-supported bifunctional catalysts

Hydrodeoxygenation (HDO) of lignin-derived bio-oil offers a promising route for the production of advanced biofuels. However, the conventional HDO of lignin-derived bio-oil faces serious problems, such as low hydrocarbon yield and easy deactivation of catalysts. Herein, a novel reaction system consisting of a highly stable bifunctional catalyst (i.e., Ni−WOx/NiAl2O4) and a dodecane solvent was developed for the HDO of lignin-derived phenolics. The Ni0 species, derived from NiWO4 precursors on the NiAl2O4, were of small crystallite size and high dispersion, together with the strong oxophilicity of W, thereby exhibiting high activity. The use of a highly stable NiAl2O4 spinel support and the replacement of common solid acid with more stable WOx for the cleavage of CO bond accounted for excellent stability. The optimized 10Ni−15WOx/NiAl2O4 exhibited a high guaiacol conversion of 97.8% with a high cycloalkane yield of 83.8% under the optimum conditions (250 °C, 5 MPa H2, and 4 h). Cycloalkanes with a high yield over 90% were also obtained by the HDO of other complex lignin-derived compounds. More importantly, the catalyst always retained its initial activity for the HDO of guaiacol in five runs, with negligible coke formation. Subsequently, the HDO behavior of the bio-oil obtained from walnut shell pyrolysis was also studied. The relative content of cycloalkanes in the products reached 44.3% after the reaction. This study highlights the prospect of a highly stable catalyst consisting of hydrogenation metal and oxophilic promoter, and dodecane solvent to enable efficient production of cycloalkanes from the HDO of lignin-derived phenolics.

Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions

Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions

Hydrodeoxygenation of phenol and pyrolysis oil using Raney Ni and IL/Zr-SBA-15 catalysts

A novel IL/Zr-SBA-15 (n(Si)/n(Zr)= 2,10,40) catalysts were synthesized, and characterized by XRD, FTIR, SEM, TEM, N2 adsorption–desorption measurement and DSC/TG. The results showed that ionic liquid (IL) has been successfully immobilized on the surface of Zr-SBA-15, and the ordered mesoporous structure can also be well preserved, even after chemical grafting reaction. Using water as a solvent, Raney Ni and IL/Zr-SBA-15 composite catalysts were investigated by hydrodeoxygenation (HDO) of phenol. The synergy of acid and metal catalysts can effectively catalyze phenol as a model compound for pyrolysis oil by tandem reactions. Under optimum reaction condition, the mean selectivity and yield of cyclohexane was 81.08% and 76.26%, respectively. The catalyst still provided satisfactory results after 5 runs. With reference to the study of phenol, HDO was carried out on the coconut clothes pyrolysis oil. The process conditions were optimized by response surface methodology. In addition, it is concluded that reaction conditions affect the order of naphthenes component content as reaction temperature>reaction time>hydrogen pressure. As a result, the content of naphthenes components in the bio-fuel reaches 34.43% and the HHV of 37.58 MJ/kg, indicating that this catalyst also has a good effect on HDO of the pyrolysis oil.

Tailoring of Surface Acidic Sites in Co-MoS2 Catalysts for Hydrodeoxygenation Reaction.

CoMo sulfides are typical catalysts for selective hydrodeoxygenation (HDO) of phenolics to aromatics which is important in bio-oil upgrading. However, it is still a challenge to promote the intrinsic activity of Co-MoS2 catalysts. Defect chemistry provides a good option to improve surface reactivity in catalysis. In this work, we report a facile H2O2 etching method to tailor the concentration of surface acidic sites. The molar ratio of H2O2/MoS2 can be altered to tune sulfur defects on the MoS2 surface for stabilizing Co species to form CoMoS active sites. The optimized Co-MoS2-2 catalyst, with the highest concentration of acidic sites, exhibits 3.4 times higher activity than the Co-MoS2-0 sample in the HDO of p-cresol to toluene. It is also found the HDO activity shows a linear relationship with the amount of surface acid (both Lewis and Brønsted acid) over the Co-MoS2-x catalysts. We believe that the understanding of the role of surface acidity would provide new opportunities for the rational design of efficient Co-MoS2 catalysts.

An efficient Pd/carbon-silica-alumina catalyst for the hydrodeoxygenation of bio-oil model compound phenol

Abstract Bio-oil is a kind of viable renewable and environmentally sustainable energy, which is obtained from fast pyrolysis of biomass. However, bio-oil is not suitable for direct application due to the high content of oxygen and moisture. The upgrading of bio-oil, especially hydrodeoxygenation of bio-oil is highly demanded but remains a challenge owing to the absence of efficient and stable catalysts. Herein, an amphiphilic Pd/carbon-silica-alumina catalyst could catalytic reactions at the oil/water interface and simultaneously stabilized the oil/water emulsions, which would be highly advantageous in bio-oil upgrading. Significantly, the hydrophilicity and hydrophobicity of the catalyst could be adjusted by changing the input amount of precursor with resols, tetraethyl orthosilicate and aluminum chloride hexahydrate. In the catalytic reaction, phenol was used as a model bio-oil compound, where decalin and water were used to simulate an oil/water mixed bio-oil system. The as prepared amphipathic Pd/MCSA-24 catalyst showed the highest conversion of phenol (98.0%) and highest selectivity for cyclohexane (87.7%) at 200 °C, which presented great potential in further bio-oil upgrading applications.

Why phenol is selectively hydrogenated to cyclohexanol on Ru (0001): An experimental and theoretical study

Ruthenium shows unique catalytic properties in selective hydrodeoxygenation of lignin-derived phenols to alkyl cyclohexanols, but seldom exploration has been devoted to the mechanism of phenol hydrogenation on Ru. Herein, the mechanism of phenol hydrogenation to cyclohexanol on Ru is explored combining experiments and density functional theory (DFT) calculations. The experimental results show that the selectivity to cyclohexanol is higher than cyclohexanone over 3% Ru-SiO2 when the conversion is higher than 25%. Mechanistic study by DFT shows that after forming cyclohexenol as an intermediate, the hydrogenation can proceed along both the classical tautomerization pathway and direct hydrogenation pathway, with tautomerization pathway being the dominant one. Further, the hydrogenation pathways producing cyclohexanol without the generation of cyclohexenol could also run parallel to the two pathways through it. These pathways together lead to the high selectivity to cyclohexanol on Ru catalyst. The refreshed hydrogenation pathway can contribute to a new insight into the mechanism of phenol hydrogenation on Ru based catalyst.

Co-processing of hydrodeoxygenation and hydrodesulfurization of phenol and dibenzothiophene with NiMo/Al2O3–ZrO2 and NiMo/TiO2–ZrO2 catalysts

Abstract The influence of Al2O3–ZrO2 and TiO2–ZrO2 supports on NiMo-supported catalysts at a different sulfur concentration in a model hydrodeoxygenation (HDO)-hydrodesulfurization (HDS) co-processing reaction has been studied in this work. A competition effect between phenol and dibenzothiophene (DBT) for active sites was evidenced. The competence for the active sites between phenol and DBT was measured by comparison of the initial reaction rate and selectivity at two sulfur concentrations (200 and 500 ppm S). NiMo/TiO2–ZrO2 was almost four-fold more active in phenol HDO co-processed with DBT than NiMo/Al2O3–ZrO2 catalyst. Consequently, more labile active sites are present on NiMo/TiO2–ZrO2 than in NiMo/Al2O3–ZrO2 confirmed by the decrease in co-processing competition for the active sites between phenol and DBT. DBT molecules react at hydrogenolysis sites (edge and rim) preferentially so that phenol reacts at hydrogenation sites (edge and edge). However, the hydrogenated capacity would be lost when the sulfur content was increased. In general, both catalysts showed similar functionalities but different degrees of competition according to the highly active NiMoS phase availability. TiO2–ZrO2 as the support provided weaker metal-support interaction than Al2O3–ZrO2, generating a larger fraction of easily reducible octahedrally coordinated Mo- and Ni-oxide species, causing that NiMo/TiO2–ZrO2 generated precursors of MoS2 crystallites with a longer length and stacking but with a higher degree of Ni-promotion than NiMo/Al2O3–ZrO2 catalyst.

A bifunctional Ni3P/γ-Al2O3 catalyst prepared by electroless plating for the hydrodeoxygenation of phenol

A bifunctional Ni3P/γ-Al2O3 catalyst was prepared by an electroless plating method and characterized by XRD, XPS, N2 adsorption–desorption, ICP, TEM, CO chemisorption, NH3 TPD, and Py-FTIR. To improve the dispersion of Ni3P on γ-Al2O3, highly dispersed nickel aluminum oxide hydrate was deposited on γ-Al2O3 by a deposition–precipitation procedure. The resulting Ni3P nanoparticles (~3.8 nm) were homogeneously dispersed on γ-Al2O3. The Ni3P/γ-Al2O3 catalyst exhibited high performance in the hydrodeoxygenation of phenol, in which both hydrogenation and dehydration were involved. The Ni3P/γ-Al2O3 was remarkably stable both in catalytic performance and in structure during a 100-h run.

Highly efficient unsupported Co-doped nano-MoS2 catalysts for p-cresol hydrodeoxygenation

To prepare catalyst with high activity, high selectivity and good stability remains the biggest challenge in the hydrodeoxygenation (HDO) of phenols by adopting MoS2-based sulfides as catalysts. Herein, we report a simple hydrothermal method to synthesize highly-dispersed nano-MoS2 with abundant defects and some curved slabs. All these advantages enable nano-MoS2 to provide a large number of coordination unsaturated sites to anchor Co atoms. The unsupported Co-doped catalyst with an optimal Co/(Co + Mo) molar ratio of 0.3 exhibited excellent performance in the HDO of p-cresol with conversion of 98.7 % and toluene selectivity of 98.9 % at 220 °C. Moreover, the optimized Co/MoS2-0.3 catalyst had a good stability after reaction of 72 h. The excellent HDO performance was attributed to the formation of abundant Co-Mo-S active sites which optimize the electrical structure of nano-MoS2 by Co promoter.

In Situ Hydrodeoxygenation of Phenol as a Model Compound for Pyrolysis Oil Using Raney Ni and Molecular Sieve Catalysts

In order to reduce the consumption of a large amount of externally supplied hydrogen, methanol was used as the hydrogen donor solvent. Phenol, a model compound of coconut clothes pyrolysis oil, was...

Elucidating the Structure of Bimetallic NiW/SiO2 Catalysts and Its Consequences on Selective Deoxygenation of m-Cresol to Toluene

As a non-noble metal, Ni could offer significant economic advantages if used as a catalyst for hydrodeoxygenation (HDO) of lignin-derived phenolics to produce aromatics. However, on unmodified Ni c...

Vapor phase hydrodeoxygenation of phenolic compounds on group 10 metal-based catalysts: Reaction mechanism and product selectivity control

Catalytic hydrodeoxygenation (HDO) of phenolics is a crucial step to convert lignin-biomass to chemicals and fuels. Catalysts based on group 10 metals (Ni, Pd and Pt) are widely used in HDO of phenolics. However, achieving a high yield toward the desirable product remains a challenge since a number of competing reactions take place at the same time, resulting in a complex product distribution. Herein, we review the recent advances in understanding the reaction mechanism on group 10 metal based catalysts and the novel strategies for selective deoxygenation of phenolics to aromatics on these catalysts under mild conditions (intermediate temperature and atmospheric pressure). Typically, HDO on Ni, Pd and Pt involves three main reaction pathways: a) hydrogenation to cyclohexanones/cyclohexanols; b) deoxygenation to aromatics, and c) C − C hydrogenolysis to CH4. Among the possible mechanisms proposed for deoxygenation to aromatics, the partial hydrogenation mechanism shows the lowest barrier for C − O cleavage, and is therefore most likely to happen. Strategies such as increasing affinity to the O atom of phenols on the surface of Ni, Pd and Pt based catalysts by either reducing the particle sizes, alloying with an oxophilic metal, modifying the metal catalyst with a reducible oxide, or combining with an acidic zeolite have been reviewed. These strategies have been shown to improve the selectivity of HDO to aromatics over the hydrogenation and C − C hydrogenolysis products and are expected to provide useful guidance for rational design of the selective HDO catalysts.

Synergetic Effect between Pd Clusters and Oxygen Vacancies in Hierarchical Nb <sub>2</sub>O <sub>5</sub> for Lignin-Derived Phenol Hydrodeoxygenation into Benzene

Synergetic Effect between Pd Clusters and Oxygen Vacancies in Hierarchical Nb <sub>2</sub>O <sub>5</sub> for Lignin-Derived Phenol Hydrodeoxygenation into Benzene

Catalytic Hydrodeoxygenation of Lignin-Derived Feedstock Into Arenes and Phenolics

lignin, as the only most abundant aromatic source in nature, shows great potential to address environmental and energy problems. Hydrodeoxygenation (HDO) as a useful way of converting lignin and its-derived compounds into value-added aromatic chemicals and fuels is able to transform the vision “fueling the future” into reality, thus garnering considerable attention in the past decade. The purpose of this minireview is to specifically address the removal of phenolic hydroxyl groups and/or methoxy groups within lignin, mainly focusing on the core questions and challenges of catalytic systems. Our own insights into future studies and recommendations for future research in this promising field are also provided.

Ambient-pressure and low-temperature upgrading of lignin bio-oil to hydrocarbons using a hydrogen buffer catalytic system

Catalytic hydrodeoxygenation is an essential step for bio-oil upgrading. However, hydrodeoxygenation usually requires a high hydrogen pressure and high temperature due to the good stability of the C–O bonds. Here we report an effective multiphase hydrodeoxygenation of lignin-based bio-oil at temperatures <100 °C and hydrogen pressures <1 atm using a synergetic catalyst system that consists of a low redox potential H4SiW12O40 (SiW12) and suspended Pt-on-carbon (Pt/C) particles. We propose that SiW12 plays three critical roles in bio-oil hydrodeoxygenation. First, it quickly oxidizes the H2 gas to form reduced SiW12 in the presence of Pt/C. Second, it transfers both electrons and H+ ions to the bulk phase to form active H* or H2 on the Pt/C surface. Third, the formation of the oxonium ion in a SiW12 superacid solution reduces the deoxygenation energy. The SiW12-enhanced proton-transfer hydrodeoxygenation mechanism is supported by density functional theory computations. As a result of the hydrogen buffer and acidic effect, up to a 90% yield of hydrocarbons (cyclohexane, benzene and their derivatives) was achieved from the hydrodeoxygenation of phenol and its derivatives. Bio-oil derived from biomass has great potential as a more sustainable fuel but its formation typically relies on energy-intensive processes. Liu et al. show how a tri-phase hydrogen-transfer catalytic system can drive hydrodeoxygenation in water under mild conditions to achieve up to 90% hydrocarbon yield.