Hydrodeoxygenation Of Phenol Research Articles

Hydrodeoxygenation of phenol and biomass fast pyrolysis oil (bio-oil) over Ni/WO3-ZrO2 catalyst

The hydrodeoxygenation of pure phenol in hexane solution and of catalytic biomass fast pyrolysis oil (bio-oil) over 10 %Ni/ZrO2 and 10 %Ni/WO3-ZrO2 catalysts was investigated in the present study, at relatively mild conditions (ca. 50−250 °C, 30 bar H2) in a continuous flow high-pressure fixed bed reactor. The catalysts were characterized for their structural, porosity, redox and acidic/basic properties which were used to rationalize the observed catalytic performance. The 10 %Ni/ZrO2 catalyst was very active and selective towards cyclohexanol in the phenol HDO experiments (100 % conversion and selectivity at 110 °C) but the enhanced acidity offered by the addition WO3 in ZrO2 was necessary to succeed a complete hydrodeoxygenation of phenol to cyclohexane at the low temperature of 150 °C with the 10 %Ni/WO3-ZrO2 catalyst. This catalyst was also proven very active in the hydrodeoxygenation of the catalytic bio-oil which consisted of mono-aromatics (i.e. alkyl-benzenes) and PAHs (mainly naphthalenes and indenes), and fewer oxygenated compounds (i.e. alkyl-phenols and benzofurans), providing a product oil containing mainly alkyl-cycloalkanes and fewer alkyl-benzenes, at the mild conditions of 210 °C and 30 bar H2.

Catalytic Hydrotreatment of β-O-4 Ether in Lignin: Cleavage of the C–O Bond and Hydrodeoxygenation of Lignin-Derived Phenols in One Pot

Selective hydrotreatment of β-O-4 ether bonds in lignin is a key strategy for the lignin valorization. The current catalytic strategy can only transfer β-O-4 model compounds to aromatics. Also, fur...

Hydrodeoxygenation of Lignin-Derived Aromatic Oxygenates Over Pd-Fe Bimetallic Catalyst: A Mechanistic Study of Direct C–O Bond Cleavage and Direct Ring Hydrogenation

Hydrodeoxygenation of lignin-derived phenols could be achieved generally with three reaction pathways: tautomerization, direct ring hydrogenation and direct C–O bond cleavage. The former pathway has been extensively studied over Pd/Fe catalyst in liquid-phase reaction, however, the contribution of the latter two is yet subject to further investigations. In this report, a comparative study of direct C–O bond cleavage and direct ring hydrogenation reaction pathways is presented on Pd/Fe, Fe and Pd/C catalysts using diphenyl ether as modelling compound. Despite its much higher activation energy than direct ring hydrogenation, direct C–O bond cleavage is dominant over Pd/Fe with much higher rates than the monometallic analogues due to the synergic catalysis of Pd–Fe. Based on this study and our previous results, the detailed reaction network for HDO of diphenyl ether is proposed.

A systematic study of the synthesis of transition metal phosphides and their activity for hydrodeoxygenation of phenol

Five different unsupported transition metal phosphides were synthesized and tested for hydrodeoxygenation of phenol in gas phase at 300 °C and atmospheric pressure. The metal phosphide phases were synthesized in two steps: synthesis of phosphates and temperature programmed reduction. In situ X-ray diffraction and temperature programmed reduction revealed the formation of the phosphide phases: Ni2P, MoP, CoP/CoP2, FeP and WP. The in situ diffractograms showed that the metal phosphate precursor is decomposed during reduction, producing metal oxide (Molybdenum) or pyrophosphate (Nickel, Iron) phases, without the formation of a metallic phase. All catalysts showed high selectivity to direct deoxygenation products, indicating that the phosphide phases promoted the direct cleavage of CO bond. However, product distribution varied significantly depending on the metal phosphide phase. Ni2P catalyst exhibited the highest selectivity to benzene, whereas CoP, FeP and WP showed a significant formation of cyclohexene. FeP also produced cyclohexane, while a large amount of C5 – C6 hydrocarbons was formed over MoP. Product distribution was correlated to the type of crystal structure of transition metal phosphides.

In Situ Formation of CoMoS Interfaces for Selective Hydrodeoxygenation of p-Cresol to Toluene

Catalytic hydrodeoxygenation (HDO) of phenolics to aromatics is one of the most important reaction routes in bio-oil upgrading. Sulfided CoMo catalysts are good candidates for this reaction, but their activities are strongly associated with the number of exposed surface sites and Co–Mo synergy. Herein, we employ zeolitic imidazolate framework-67 as a cobalt precursor and template for inverse deposition of MoS2 ultrathin sheets inside the framework to form CoMoS interfaces by using a simple hydrothermal method. The size-confined MoS2 possesses a few-layered structure and abundant surface defects. It is found that in situ generation of a CoMoS active phase would take place to reach the best activity of our catalysts under the HDO reaction condition or by H2 prereduction treatment. With varying different Co–Mo molar ratios, the optimized CoMoS-0.18 catalyst exhibits the highest HDO activity, with a p-cresol conversion of 92.4% and a toluene selectivity of 95.5% at 250 °C. The high performance is ascribed to the formation of an accessible surface CoMoS phase after surface restructuring.

Effect of surface structure and Pd doping of Fe catalysts on the selective hydrodeoxygenation of phenol

Density functional theory (DFT) calculations were performed to investigate the effects of surface structure and Pd doping of Fe catalysts on the activity and selectivity of phenol hydrodeoxygenation (HDO). Phenol adsorption via binding with the aromatic ring was found to be energetically more stable than adsorbing through solely the hydroxyl group on Fe(110), Fe(111) and Fe(211) surfaces. The adsorption strength on monometallic Fe surfaces increased in the sequence of Fe(211) < Fe(110) < Fe(111). Pd doping did not have a significant influence on the adsorption stability of phenol. The (211) facet of Fe featured particular steps showed good activity toward aromatics production, as evidenced by the lower barriers associated with the dehydroxylation followed by H addition to form benzene than the direct hydrogenation on the aromatic ring. In contrast, the ring saturation products would be dominant on Fe(110) and Fe(111) surfaces due to lower hydrogenation barriers on the aromatic ring of phenol as compared to the CAr-O bond cleavage. The kinetically preferred pathway for phenol conversion on Pd doped Fe(110) and Fe(111) surfaces was the direct hydrogenation on the aromatic ring, same to that identified on monometallic (110) and (111) surfaces. In comparison, on Fe(211), the difference in kinetic barrier between dehydroxylation and ring hydrogenation pathways became larger in the presence of Pd, promoting the selectivity to benzene formation. In the presence of Pd dopant, the H2 molecule was readily dissociated and the surface H* coverage was increased, leading to a lowering of the adsorption enthalpy of key surface species and ultimately enhancing the rates of HDO.

Hydrodeoxygenation of Lignin‐Derived Monomers and Dimers over a Ru Supported Solid Super Acid Catalyst for Cycloalkane Production

AbstractThe monomers and dimers produced via lignin depolymerization are a promising alternative to transportation fuels after hydrodeoxygenation (HDO). However, these compounds contain numerous oxygen‐containing functional groups that are strongly bonded to aromatic rings. Therefore, the conventional HDO of lignin‐derived compounds faces serious problems of catalyst deactivation due to coke deposition and low hydrocarbon yields. A metal–solid super acid catalyst, i.e., Ru(SO42−)/ZrO2–CeO2, is synthesized, characterized, and evaluated for the HDO of various lignin‐derived monomers and dimers in a biphasic n‐dodecane/H2O system. A high cyclohexane yield of 98.5% is obtained by the HDO of phenol performed at 200 °C and 5 MPa. The “hydrated” configuration can be formed between the hydrogenation intermediates and H2O on the Ru sites. In addition, the anionic vacancies of ZrO2–CeO2 can be occupied by H− derived from the heterolytic cleavage of H2, leading to the formation of metal hydrides. The strong acidity of SO42−/ZrO2–CeO2 is beneficial for the subsequent deoxygenation of the hydrotreated products. In addition, the biphasic system can minimize the side reactions induced by the strong acidity of the catalyst. The catalytic system also exhibits a good catalytic performance for the HDO of other lignin‐derived monomers and dimers to produce cycloalkanes.

Conversion of phenol to cyclohexane in the aqueous phase over Ni/zeolite bi-functional catalysts

A series of Ni/HZSM-5 and Ni/HIM-5 bi-functional catalysts were synthesized and applied to the aqueous-phase hydrodeoxygenation (HDO) of phenol. The Ni dispersibility and particle sizes were shown to be directly related to the porosity and crystal sizes of the parent zeolites, which further influenced the catalytic performances. The large pores and small crystal sizes of the parent zeolites were beneficial for dispersing Ni and forming small Ni particles, and the corresponding Ni/zeolite catalyst exhibited a higher phenol conversion and selectivity towards hydrocarbons. Importantly, the Ni/HIM-5 bi-functional catalyst exhibited a high activity (98.3%) and high selectivity for hydrocarbons (98.8%) when heated at 220°C for 1 h and is thus a new potential catalyst for the HDO of phenolics to form hydrocarbons in the aqueous phase.

Kinetic investigation of phenol hydrodeoxygenation over unsupported nickel phosphides

Three representative nickel phosphides (Ni2P, Ni12P5 and Ni3P) were prepared and characterized comparatively by means of XRD, N2 adsorption-desorption, ICP, TEM, XPS and NH3-TPD. It is shown that the binding energy ascribed to Niδ+ in nickel phosphide decreased, whereas that of Pδ− increased, as the Ni/P molar ratio increased from 2 (Ni2P) to 2.4 (Ni12P5) and to 3 (Ni3P). It is indicated that the slight transfer of electron density from Ni to P atoms decreased from Ni2P, Ni12P5 to Ni3P. NH3-TPD measurements revealed that the total acid amounts of the nickel phosphides decreased with increasing Ni/P molar ratio. Their catalytic performance in hydrodeoxygenation (HDO) were investigated using phenol in decalin (1.0 wt%) as the feed. It is found that phenol was readily hydrogenated to yield cyclohexanol over all the three unsupported nickel phosphides at low temperatures and the subsequent HDO of cyclohexanol was rate-determining. As a result, the overall kinetics of phenol HDO were investigated by measuring the rates of phenol HDO and cyclohexanol HDO. The activation energy for phenol hydrogenation decreased in the order Ni2P > Ni12P5 > Ni3P, whereas that for cyclohexanol dehydration increased.

Catalyst Characteristics and Performance of Silica-Supported Zinc for Hydrodeoxygenation of Phenol

The present investigation aimed to study the physicochemical characteristics of supported catalysts comprising various percentages of zinc dispersed over SiO2. The physiochemical properties of these catalysts were surveyed by N2 physisorption (BET), thermogravimetry analysis (TGA), H2 temperature-programmed reduction, field-emission scanning electron microscopy (FESEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), and NH3 temperature-programmed desorption (NH3-TPD). In addition, to examine the activity and performance of the catalysts for the hydrodeoxygenation (HDO) of the bio-oil oxygenated compounds, the experimental reaction runs, as well as stability and durability tests, were performed using 3% Zn/SiO2 as the catalyst. Characterization of silica-supported zinc catalysts revealed an even dispersion of the active site over the support in the various dopings of the zinc. The acidity of the calcinated catalysts elevated clearly up to 0.481 mmol/g. Moreover, characteristic outcomes indicate that elevating the doping of zinc metal led to interaction and substitution of proton sites on the SiO2 surface that finally resulted in an increase in the desorption temperature peak. The experiments were performed at temperature 500 °C, pressure 1 atm; weight hourly space velocity (WHSV) 0.32 (h−1); feed flow rate 0.5 (mL/min); and hydrogen flow rate 150 (mL/min). Based on the results, it was revealed that among all the prepared catalysts, that with 3% of zinc had the highest conversion efficiency up to 80%. However, the selectivity of the major products, analyzed by gas chromatography flame-ionization detection (GC-FID), was not influenced by the variation in the active site doping.

Mild Hydrodeoxygenation of Phenols into Cycloalkanes under Ambient Hydrogen Pressure over a Ni/H‐Beta Catalyst

AbstractHydrodeoxygenation of phenols is an important process for producing six‐membered ring hydrocarbons from lignin. The reaction generally requires high temperatures (300 °C or higher) and high‐pressure H2 gas. In recent years, milder reactions at around 100 °C under atmospheric pressure H2 have been developed by using noble metal catalysts. On the other hand, the reaction with less expensive base metal catalysts still requires either of high temperatures or high‐pressure H2, or the both. Herein, we performed the reaction of various phenols over a Ni/H‐Beta catalyst in octane at 110 °C under atmospheric pressure H2 in a batch reactor to give the corresponding cyclohexanes in 96–33% yield. The reaction proceeds through formation of cyclohexene intermediates, which are eventually converted to cyclohexanes either directly or via transient arene intermediates.

Gas-phase hydrodeoxygenation of phenol over Zn/SiO2 catalysts: Effects of zinc load, temperature, weight hourly space velocity, and H2 volumetric flow rate

The hydrodeoxygenation (HDO) of phenol catalyzed by Zn/SiO2 under atmospheric H2 pressure was investigated in a continuous fixed bed reactor. The effects of several process parameters (zinc load, reaction temperature, weight hourly space velocity (WHSV), and H2 volumetric flow rate) were evaluated to optimize process conditions. Phenol was selected as a stable model component for lignin degradation products in fast pyrolysis bio-oil. Silica-supported zinc catalysts were prepared with different loadings of the active metal (0.5%, 1%, 2%, 3%, and 4%) and assessed using characterization techniques such as XRD, ICP-OES, BET, H2-TPR/TPD, and FESEM–EDX. Reaction products including benzene, cyclohexene, and cyclohexane were identified through GC/FID analysis. Experimental results revealed that process yield increased with reaction temperature, metal loading, and WHSV. The selectivity percentages of the products were slightly changed by varying process parameters. Moreover, H2 volumetric flow rate exerted a negligible effect on product yield and selectivity.

Engineering Co Nanoparticles Supported on Defect MoS2–x for Mild Deoxygenation of Lignin-Derived Phenols to Arenes

To enhance the catalytic activity and temper the reaction conditions in the hydrodeoxygenation (HDO) of lignin-derived phenols to arenes, a Co–MoS2–x catalyst was proposed and prepared via a facile...

Selective Deoxygenation of Lignin-Derived Phenols and Dimeric Ethers with Protic Ionic Liquids

Hydrodeoxygenation (HDO) of lignin-derived phenols and dimeric ethers to biofuels has great significance for advanced utilization of renewable lignocelluloses and the future biobased economy. Herei...

Hydrodeoxygenation of 2-methoxy phenol: Effects of catalysts and process parameters on conversion and products selectivity

The hydrodeoxygenation (HDO) of 2-methoxy phenol (MP), a lignin-derived compound, has massive prospective for valuable compounds production. The lignin derived model compounds can be used for production of green chemicals. The model compound MP conversion into cyclohexane was investigated over Ru metal loaded on various supports (ZSM-5, Y-zeolite, β-zeolite, COK-12, mordenite, ZrO2, and TiO2). The catalytic properties such as the acidic sites, pore size, and morphology influenced the HDO activity and selectivity of the cyclohexane. The yield of cyclohexane increases up to optimum acidity further increases the acidity of the catalyst, the product yield decreased. The experiments carried out at temperature range of 200–300 °C, and 1–25 bar hydrogen pressure in a fixed bed reactor. The parameters greatly influenced the HDO as well as the cyclohexane yield, selectivity, and MP conversion. The highest conversion (100%) and yield of cyclohexane (99.0%) observed at 250 °C under pressure of 20 bar with Ru/ZSM-5 catalyst. Further the recyclability and stability have been checked and observed that Ru/ZSM-5 is stable up to 200 h and displayed excellence activity in both HDO and cyclohexane selectivity. Weight hourly space velocity (WHSV) was investigated (0.5–1.5 h−1). The suitable WHSV found for HDO of 2-methoxy phenol and cyclohexane yield was 1 h−1. The reaction mechanism showed that the Ru/ZSM-5 catalyst provoked the HDO compared to the others catalyst.

Flexible NiCo-based catalyst for direct hydrodeoxygenation of guaiacol to cyclohexanol

The catalytic hydrodeoxygenation (HDO) of lignin-derived phenols is an important step for bio-oil upgrading.

Hydrodeoxygenation of lignin-derived phenolics – a review on the active sites of supported metal catalysts

This article mainly reviews the state-of-the-art achievements of supported metal catalysts and the characteristics and actions of their active sites, working in the reactions involved in HDO of lignin-derived phenolic compounds.

Selective hydrodeoxygenation of lignin phenols to alcohols in the aqueous phase over a hierarchical Nb2O5-supported Ni catalyst

Lignin-derived phenols can be highly selectively converted to alcohols in the aqueous phase over hierarchical Ni/Nb2O5 assembled from Nb2O5 nanoplates.

Surface engineering of earth-abundant Fe catalysts for selective hydrodeoxygenation of phenolics in liquid phase.

Development of inexpensive sulfur-free catalysts for selective hydrogenolysis of the C-O bond in phenolics (i.e., selective removal of oxygen without aromatic ring saturation) under liquid-phase conditions is highly challenging. Here, we report an efficient approach to engineer earth-abundant Fe catalysts with a graphene overlayer and alkali metal (i.e., Cs), which produces arenes with 100% selectivity from liquid-phase hydrodeoxygenation (HDO) of phenolics with high durability. In particular, we report that a thin (a few layers) surface graphene overlayer can be engineered on metallic Fe particles (G@Fe) by a controlled surface reaction of a carbonaceous compound, which prevents the iron surface from oxidation by hydroxyls or water produced during HDO reaction. More importantly, further tailoring the surface electronic properties of G@Fe with the addition of cesium, creating a Cs-G@Fe composite catalyst in contrast to a deactivated Cs@Fe one, promotes the selective C-O bond cleavage by inhibiting the tautomerization, a pathway that is very facile under liquid-phase conditions. The current study could open a general approach to rational design of highly efficient catalysts for HDO of phenolics.

An efficient bifunctional Ru-NbOPO4 catalyst for the hydrodeoxygenation of aromatic ethers, phenols and real bio-oil

An efficient bifunctional NbOPO4 supported Ru catalyst (Ru-NbOPO4) was applied to the hydrodeoxygenation of aromatic ethers and phenols and the upgrading of bio-oil. Characterization results revealed that the Ru-NbOPO4 catalyst possessed strong acidity, including Lewis and Brønsted acids. The Lewis acid sites originated from the NbO bonding structures, including slightly distorted octahedral NbO6, regular tetrahedral NbO4 and highly distorted octahedral NbO6. In combination with the strong acidity of the NbO species and excellent hydrogenation activity of the metallic Ru, the bifunctional Ru-NbOPO4 catalyst exhibited an excellent catalytic activity in the hydrodeoxygenation of aromatic ethers and phenols with different structures, and even real bio-oil to alkanes. The hydrocarbon yield after real bio-oil upgradation was up to 88.2 %. Carbon deposition and enlargement of the Ru nanoparticles resulted in slight deactivation of the catalyst. The catalytic activity could be mostly recovered after being calcined and reduced.