Hydrodeoxygenation Of Phenol Research Articles

Hydrodeoxygenation of phenol over metal supported niobia catalysts

This work studied the performance of Rh, Pd and Ni supported on Nb2O5 catalysts for hydrodeoxygenation of phenol in the vapor phase. In general, an increase in reduction temperature favored benzene selectivity. For Ni/Nb2O5, this selectivity increased around 50%. The change in reduction temperature also affected the reaction rates. After reduction at 500 °C, there was a decline in these rates for all samples (a 75-fold decrease for Pd/Nb2O5). This behavior was related to structural modifications caused by strong metal-support interaction (SMSI). For Pd sample, the increase in benzene selectivity (around 30%) was related to a partial encapsulation of the metal by NbOx, which led to an electron enrichment of the Pd particles, as indicated by XPS analysis. This alteration caused an enhancement in the adsorption of phenol through its oxygen. For Rh/Nb2O5, the reduction temperature did not change the benzene selectivity. According to TPR-XANES results, Rh is fully reduced for both reduction conditions studied. On other hand, Ni sample was not fully reduced after H2 treatment at 300 °C, as observed in TPR-XANES at Ni K-edge. It was hypothesized that higher reduction temperatures favored the Ni-NbOx interface, which probably improved the oxophilicity of this sample and, consequently, the benzene selectivity.

Performance of a Ni-Cu-Co/Al2O3 Catalyst on in-situ Hydrodeoxygenation of Bio-derived Phenol

The in-situ hydrodeoxygenation of bio-derived phenol is an attractive routine for upgrading bio-oils. Herein, an active trimetallic Ni-Cu-Co/Al2O3 catalyst was prepared and applied in the in-situ hydrodeoxygenation of bio-derived phenol. Comparison with the monometallic Ni/Al2O3 catalyst and the bimetallic Ni-Co/Al2O3 and Ni-Cu/Al2O3 catalysts, the Ni-Cu-Co/Al2O3 catalyst exhibited the highest catalytic activity because of the formation of Ni-Cu-Co alloy on the catalyst characterized by using X-ray powder diffraction (XRD), temperature programmed reduction (TPR), N2 physisorption, scanning electron microscope (SEM), and transmission electron microscope (TEM). The phenol conversion of 100% and the cyclohexane yield of 98.3% could be achieved in the in-situ hydrodeoxygenation of phenol at 240 °C and 4 MPa N2 for 6 h. The synergistic effects of Ni with Cu and Co of the trimetallic Ni-Cu-Co/Al2O3 catalyst played a significant role in the in-situ hydrodeoxygenation process of phenol, which not only had a positive effect on the production of hydrogen but also owned an excellent hydrogenolysis activity to accelerate the conversion of cyclohexanol to cyclohexane. Furthermore, the catalyst also exhibited excellent recyclability and good potential for the upgrading of bio-oils.

Factors influencing selectivity in the liquid-phase phenol hydrodeoxygenation over ZSM-5 supported Pt/Ir and Pt+Ir catalysts

The effect of partial Pt substitution by Ir on the catalytic response of bimetallic Pt-Ir/ZSM-5 (Pt/Ir = 1) catalyst in the liquid-phase hydrodeoxygenation (HDO) of phenol was investigated. To evaluate the catalyst intrinsic activity, the ZSM-5 supported Pt, Ir and Pt + Ir catalysts were prepared with similar total metal loading (ca. 3 wt.%) and acidity. The catalysts were characterized by several physical and chemical techniques and tested in the HDO of phenol reaction carried out in a batch reactor at T = 200 °C under H2 pressure of 3.0 MPa. For all the catalysts, the phenol transformation mainly proceeds via hydrogenation + dehydration (HYD reaction route) leading to cyclohexane as the main product (selectivity 60–96%). Partial substitution of Pt by Ir in catalyst formulation (Pt50-Ir50/ZSM-5) enhances both activity and selectivity toward O-free products. This was associated to Ir surface enrichment (from HRTEM). The Ir/ZMS-5 and Pt50-It50/ZMS-5 catalysts having well dispersed Ir nanoparticles were more selective toward dehydration than Pt/ZSM-5 having Pt species with a broad size distribution range. The catalyst activity-structure correlation suggests that the dehydration of cyclohexanol (intermediate product) can occur at the interface between the metal and acid sites of the support.

Surface Modification of a Supported Pt Catalyst Using Ionic Liquids for Selective Hydrodeoxygenation of Phenols into Arenes under Mild Conditions.

The selective and efficient removal of oxygenated groups from lignin-derived phenols is a critical challenge to utilize lignin as a source for renewable aromatic chemicals. This report describes how surface modification of a zeolite-supported Pt catalyst using ionic liquids (ILs) remarkably increases selectivity for the hydrodeoxygenation (HDO) of phenols into arenes under mild reaction conditions using atmospheric pressure H2 . Unmodified Pt/H-ZSM-5 converts phenols into aliphatic species as the major products along with a slight amount of arenes (10 % selectivity). In contrast, the catalyst modified with an IL, 1-butyl-3-methylimidazolium triflate, keeps up to 76 % selectivity for arenes even at a nearly complete conversion of phenols. The IL on the surface of Pt catalyst may offer the adsorption of phenols in an edge-to-face manner onto the surface, thus accelerating the HDO without the ring hydrogenation.

Valorization of biomass derivatives through the conversion of phenol over silica-supported Mo-Re oxide catalysts

Liquid-phase hydrodeoxygenation of phenol over silica-supported MoOx-ReOx catalysts was investigated at 300 °C and 5 MPa of H2. Mixed-oxides catalysts with similar surface metal density (2.3 atoms of metal per nm2 of SiO2) but different relative Mo and Re loadings were prepared by incipient wetness impregnation. The catalysts were characterized by N2 adsorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), ultraviolet visible diffuse reflectance (UV–vis-DR) spectroscopy, X-ray diffraction (XRD) and temperature programmed desorption of NH3 (TPD-NH3). All the catalysts were highly active and selective towards deoxygenated products. However, MoOx/SiO2 was the most selective towards cyclohexane formation. Higher amount of benzene was produced with the Re-containing catalysts than it was over the MoOx/SiO2 catalyst, indicating that ReOx favored direct deoxygenation over hydrogenation of the aromatic ring. The catalyst containing equimolar amounts of MoOx and ReOx exhibited the highest yield of benzene. This result can be attributed to a synergistic effect that arises from electronic interaction between rhenium and molybdenum oxides which favors the formation of new oxygen vacancy sites. The study reveals that benzene selectivity is mainly influenced by ReOx sites and the activity can be tuned by a balance of MoOx and ReOx sites.

Hydrodeoxygenation of phenols, acids, and ketones as model bio-oil for hydrocarbon fuel over Ni-based catalysts modified by Al, La and Ga

The large-scale application of bio-oil has been restricted due to its high O content, strong acidity and low heat value. Therefore, the hydrodeoxygenation (HDO) of phenols, acids, and ketones as bio-oil model compounds for hydrocarbon fuel via Ni-based catalysts modified by metal oxides (Al, La and Ga) was investigated. The results showed that the hydrocarbon content was over 70.65% when the mixed supported catalysts Ni/HZSM-5-γ-Al2O3, Ni/HBeta-La2O3 and Ni/HBeta-Ga2O3 were used for the HDO of guaiacol (GUA). Cyclic hydrocarbons and aromatic hydrocarbons were the main products. Among these catalysts, Ni/HZSM-5-γ-Al2O3 was the most effective in the HDO of acetic acid. The conversion and hydrocarbon content were 100.00% and 88.62%, respectively. Long-chain alkanes were the main components of the upgraded liquid. Ni/HZSM-5-γ-Al2O3 was beneficial for the HDO of hydroxyacetone with 100.00% conversion, 80.30% hydrocarbon content and 48.67% yield. The HDO pathways of GUA, acetic acid and hydroxyacetone were as follows: 1) GUA was mainly converted into benzene and its derivatives by transmethylation, isomerization and hydrogenation (HYD). 2) Acetic acid was converted to long-chain alkanes by HYD, self-condensation, saturated HYD and isomerization. 3) Hydroxyacetone was converted into long-chain alkanes by HYD, self-condensation, demethylation, aldol condensation and saturated HYD. This work provides basic data for obtaining renewable hydrocarbon fuel from biomass via HDO with a low-cost catalyst.

Preparation of hydrophobic MoS2, NiS2-MoS2 and CoS2-MoS2 for catalytic hydrodeoxygenation of lignin-derived phenols

The water produced during the hydrodeoxygenation (HDO) processes has a negative effect on sulfide catalysts, which lowers the activity and stability. To solve this problem, hydrophobic MoS2, NiS2-MoS2 and CoS2-MoS2 catalysts are prepared and then applied into the HDO of 4-ethylphenol and 4-propylguaiacol. The obtained MoS2 had strong hydrophobicity and its air-water contact angle reached up to 147.5°, which might be attributed to that modification of the surface morphology due to the addition of silicomolybdic acid. During the HDO reaction on MoS2, the specific surface area played an important effect on the HDO activity. After the deposition of NiS2 or CoS2, the hydrophobicity of NiS2-MoS2 and CoS2-MoS2 reduced slightly, but the HDO activities of these two catalysts were enhanced, especially for CoS2. 99.9% Conversion was achieved with a selectivity of 99.6% ethylbenzene after the HDO of 4-ethylphenol at 225 °C for 3 h. These hydrophobic catalysts also had good activity for the HDO of 4-propylguaiacol. Moreover, because the hydrophobicity could prevent water from contacting with active sites and then protect the sulphide structure, hydrophobic sulphide catalysts exhibited high stability.

Kinetic analysis and reaction mechanism for anisole conversion over zirconia-supported molybdenum oxide

Gas-phase catalytic conversion of anisole and its reaction intermediates was studied over a 10 wt% MoO3/ZrO2 catalyst at temperatures between 553 and 633 K and H2 partial pressures (PH2) ≤ 1 bar. Benzene, phenol, cresol and methyl anisole were identified as the primary products from the hydrodeoxygenation (HDO), hydrogenolysis, intra- and intermolecular alkylation of anisole, respectively. The anisole to benzene conversion featured a first-order dependence with respect to PH2, while the conversion of phenol to benzene and m-cresol to toluene, showed PH2 and Poxygenate reaction orders of 1/2 and zero, respectively. A kinetic model showed that although the secondary pathway of phenol HDO to benzene has a rate constant ∼3 times higher than that for the HDO of anisole to benzene, the anisole HDO pathway is dominant at low anisole conversions. Apparent orders of ∼½ with Poxygenate for anisole hydrogenolysis and alkylation to form phenol, cresol, and methyl anisole implied the existence of different active sites than those responsible for HDO. Co-feed studies with H2O, pyridine, and di-tert butyl pyridine (DTBP) indicated that the active-sites responsible for HDO have a Lewis acid character that is associated with oxygen vacancies and that is distinct from the nature of sites responsible for hydrogenolysis and alkylation. Accordingly, co-feeding CH3OH resulted in increased phenol alkylation rates to form alkylated cresols along with inhibition of phenol to benzene HDO rates. A three-site model was proposed to unify the HDO, hydrogenolysis, and alkylation reactivity data obtained from the kinetic and co-feed studies.

Mesoporous Aluminosilicate Nanofibers with a Low Si/Al Ratio as Acidic Catalyst for Hydrodeoxygenation of Phenol

AbstractMesoporous aluminosilicate nanofibers (mASNF) were prepared using hard and soft dual templates approach. The mesoporous material was fully characterized and its acidic nature was confirmed by FTIR spectroscopy of pyridine adsorption and 27Al/29Si solid state NMR. Thanks to the incorporated aluminum atoms, the acidic material showed high hydrothermal stability which is an essential property for biomass conversion applications. The catalytic performance of Pd supported on mASNF for hydrodeoxygenation (HDO) of lignin model compound was also investigated. A complete conversion and a high selectivity towards cyclohexane (up to 95 %) starting from phenol were achieved with this bifunctional catalyst. In comparison, no cyclohexane has been produced with a non‐acidic material which underlines the importance of acidic sites in HDO process selectivity control. Moreover, the catalyst can be recycled without losing its initial structure.

Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol

This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (MoOh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of CoOh and the catalytic performance. At low CoOh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS2 slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available CoOh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio.

Effect of Doped Metals on Hydrodeoxygenation of Phenol over Pt-Based Bimetallic Alloys: Caryl–OH Versus CaliphaticH–OH Bond Scission

Herein, using density functional theory calculations complemented by microkinetic modeling, we systematically investigated hydrodeoxygenation (HDO) of phenol, a model compound for phenolic oxygenat...

Hydrodeoxygenation (HDO) of Aliphatic Oxygenates and Phenol over NiMo/MgAl2O4: Reactivity, Inhibition, and Catalyst Reactivation

This study provides new insights into sustainable fuel production by upgrading bio-derived oxygenates by catalytic hydrodeoxygenation (HDO). HDO of ethylene glycol (EG), cyclohexanol (Cyc), acetic acid (AcOH), and phenol (Phe) was investigated using a Ni-MoS2/MgAl2O4 catalyst. In addition, HDO of a mixture of Phe/EG and Cyc/EG was studied as a first step towards the complex mixture in biomass pyrolysis vapor and bio-oil. Activity tests were performed in a fixed bed reactor at 380–450 °C, 27 bar H2, 550 vol ppm H2S, and up to 220 h on stream. Acetic acid plugged the reactor inlet by carbon deposition within 2 h on stream, underlining the challenges of upgrading highly reactive oxygenates. For ethylene glycol and cyclohexanol, steady state conversion was obtained in the temperature range of 380–415 °C. The HDO macro-kinetics were assessed in terms of consecutive dehydration and hydrogenation reactions. The results indicate that HDO of ethylene glycol and cyclohexanol involve different active sites. There was no significant influence from phenol or cyclohexanol on the rate of ethylene glycol HDO. However, a pronounced inhibiting effect from ethylene glycol on the HDO of cyclohexanol was observed. Catalyst deactivation by carbon deposition could be mitigated by oxidation and re-sulfidation. The results presented here demonstrate the need to address differences in oxygenate reactivity when upgrading vapors or oils derived from pyrolysis of biomass.

Effect of Support on the Hydrodeoxygenation of Phenol using Ni-based Metal Catalysts: Ni/SiO2, Ni/ZrO2, and Ni/Al2O3

Hydrodeoxygenation (HDO) reaction is a fundamental step for producing bio-oil from lignocellulosic biomass. One of the major components from biomass is lignin which can be hydrolysed into phenolic derivatives. Here, we reported the preparation of Ni-based metal catalysts with the variation of a metal oxide for HDO of phenol. The Ni loading for each metal oxides is 15% (w/w), supported on SiO2, ZrO2, and Al2O3. The XRD analysis showed that Ni metal was detected in the SiO2 support at 2θ = 44.26°, 51.72°, 76.5°; Ni in ZrO2 at 2θ = 44.55°, 51.9°, 76.4°; and Ni in Al2O3 at 2θ = 44.12°, 51.72°, and 76.78°. The catalytic test for HDO reaction was carried out in the autoclave oil batch reactor, heated for 2 hours at 200°C with H2 gas atmosphere. Based on GC-MS analysis, the reaction at 200°C usingNi-SiO2 gave the highest product conversion, that is 52.2% with the selective formation of 2-methyl-1-butanol (52.2%). On the other hand, the reaction using Ni/ZrO2 only produce 17.64% of the products with selective formation of cyclohexanone (35.35%). The result showed that products distribution is significantly affected by the type of the support.

Synthesis of Ni Catalyst Supported on SiO2-ZrO2 Binary Oxide for Hydrodeoxygenation of Phenol

Hydrodeoxygenation is a one-step reaction that involve the hydrogenation of unsaturated carbon followed with the deoxygenation of the carbon-oxygen bond. This reaction is effective for converting biomass-derived chemicals from bio-oils, fats, woods, and lignocellulosic materials into biofuels using metal-based oxide catalysts. A Ni based-metal oxide catalyst is reported for hydrodeoxygenation reaction of phenol. The catalyst was prepared by a wet-impregnation method using Ni(NO3)2.6H2O dissolved in deionized water and mixed with the previously prepared SiO2-ZrO2 binary oxide as support. After calcination and reduction at 500 °C, Ni/SiO2-ZrO2 catalyst was obtained. The XRD results showed 2θ peaks for metallic Ni at 30°, 44° and 76°. Additional peaks were detected at 2θ = 35°, 50°, 51°, and 60° for ZrO2 tetragonal phase. However, peaks were not detected for SiO2 suggesting amorphous SiO2-ZrO2 composite formation. The XRF analysis of Ni loading was detected at 16.45%. The catalyst activity test for hydrodeoxygenation of phenol was performed using a batch reactor at 200 °C for 2 h and 8 h. The GC-MS analysis gave product conversion for 2 h at 16.84% with the selectivity formation of cyclohexanol and cyclohexanone at 48.10% and 45.78% yield, respectively. After a prolonged reaction time of 8 h, 100% selectivity for cyclohexanol was achieved. Product distribution showed that the catalyst is active for hydrogenation of benzene better than -OH or C=O deoxygenation. The results suggest Ni/SiO2-ZrO2 could be a potential catalyst for biofuel production via hydrogenation reaction.

Catalytic Activity of Rhodium Phosphide for Selective Hydrodeoxygenation of Phenol

Effect of P/Rh ratio and reduction temperature on catalytic activity and product selectivity of rhodium phosphide (Rh2P) for hydrodeoxygenation (HDO) of phenol was studied to develop production of ...

The synergistic effect between Ni sites and Ni-Fe alloy sites on hydrodeoxygenation of lignin-derived phenols

The catalytic hydrodeoxygenation (HDO) of lignin-derived phenolic compounds is a critical step in the upgrading of bio-oil. Here, bimetallic Ni-Fe nanoparticles supported on mesoporous carbon spheres (MCSs) were fabricated and applied in HDO of phenol. In comparison with monometallic Ni and Fe catalysts, the bimetallic Ni-Fe catalyst exhibited better performance for phenol HDO due to the formation of Ni-Fe alloy phase identified by X-ray powder diffraction (XRD) and Mössbauer spectroscopy techniques. Among several explored ratios, the catalysts with Ni/Fe ratio of 3/1 presented the highest cyclohexane yield. The reaction occurred in two consecutive steps: the hydrogenation of phenol to cyclohexanol and the further hydrogenolysis of cyclohexanol to cyclohexane. Kinetic studies showed that the hydrogenolysis of cyclohexanol controlled the overall reaction rate of phenol HDO due to the lower reaction rate of this step. Indeed, the turnover frequency (TOF) values of cyclohexanol normalized by surface metallic Ni sites exhibited a linear correlation with Ni-Fe alloy sites. The alloying of iron in the bimetallic Ni-Fe catalysts significantly enhanced the adsorption strength of cyclohexanol, which is the reason of the high activity of the Ni-Fe alloy particles. Thus, Fe-containing sites adsorb the hydroxyl species while Ni sites perform the H2 activation, their synergistic effect plays a key role in phenol HDO process.

Development of Bifunctional Hydrodeoxygenation Catalyst Rh‐HY for the Generation of Biomass‐Derived High‐Energy‐Density Fuels

Liquid‐phase hydrodeoxygenation (HDO) of phenol, anisole, and guaiacol over rhodium‐doped, high‐silica content zeolite catalysts (Si/Al = 15), HY, is investigated in a high‐pressure‐fixed bed reactor. These catalysts are characterized by inductively coupled plasma optical emission spectrometry, scanning electron microscopy with energy‐dispersive spectroscopy, thermogravimetric analysis, X‐ray diffraction, N2 physisorption, ammonia temperature‐programmed desorption, temperature‐programmed oxidation, temperature‐programmed reduction, 27Al magic angle spinning nuclear magnetic resonance, and X‐ray photoelectron spectroscopy. The effects of reaction temperature (150–250 °C) and weight hourly space velocity (WSHV = 1.0–2.8 h−1) on activity, stability, and product distribution are investigated. The main products obtained from HDO reactions are methylcyclopentane, cyclohexane, methylcyclohexane, and bicyclohexyl. Cyclohexanone is the most abundant oxygenated product along with deactivation. For all tested catalysts, increasing the reaction temperature up to 250 °C improves the HDO reactions without significant activity or selectivity loss. Higher rhodium loading extends the catalyst life and increases the activity and cyclohexane selectivity for the guaiacol feed. The experiments indicate that anisole, phenol, and guaiacol undergo aromatic hydrogenation on rhodium particles first, followed by deoxygenation on the acid sites over zeolite combined with additional hydrogenation.

On the Feasibility of Using Hierarchical ZSM‐5 and Beta Zeolites as Supports of Metal Phosphides for Catalytic Hydrodeoxygenation of Phenol

Hierarchical ZSM‐5 and beta zeolites are assessed and compared as supports for the preparation of Ni and Co phosphide‐based hydrodeoxygenation (HDO) catalysts. Zeolites are first impregnated with the metals and P precursors, followed by temperature‐programmed reduction, to obtain the corresponding Ni2P and Co2P phases. In the HDO tests, phenol is used as a model compound typically present in pyrolysis bio‐oils. Me2P deposition affects the textural and acidic properties of the zeolitic supports, especially in the case of h‐beta, because a collapse of its mesoporosity and the formation of aluminophosphate species are observed. For both zeolites, Ni2P is the most active phosphide phase. In particular, Ni2P/h‐ZSM‐5 exhibits outstanding results (almost full phenol conversion, complete deoxygenation, and narrower compound yield distribution), even when compared with other Ni2P‐supported materials reported in the literature. Moreover, this catalyst can be effectively regenerated by calcination and subsequent reduction treatment, so that the catalytic performance remains hardly unaltered. The superior catalytic activity for phenol HDO of the h‐ZSM‐5 support is assigned mainly to the preservation of the secondary mesoporosity, which provides a good dispersion of the Ni2P nanoparticles and a good accessibility to the zeolite acid sites.

Effect of acid-metal balance of bifunctional Pt/Beta catalysts on vapor phase hydrodeoxygenation of m-cresol

Abstract Metal/zeolite bifunctional catalysts have been widely explored for hydrodeoxygenation (HDO) of phenolics. However, the effect of acid-metal balance is not clearly understood because it is difficult to decouple this from other effects. In this work, a series of 1 wt.% Pt/Beta catalysts with different Bronsted acid site (BAS) to surface Pt ratios (BAS/Pt) were prepared by varying only the density of BAS, and tested in HDO of m-cresol at 250 °C and atmospheric pressure. Increasing BAS density increases intra-crystallite diffusion constraints of m-cresol/products due to strong chemisorption on BAS, and therefore slows their transportation through BASs toward the Pt sites inside the micropores of zeolite. As a result, both the reaction rate and turnover frequency of HDO are reduced with increasing BAS/Pt ratio. Increasing BAS/Pt ratio increases the yield of ring contraction products but reduces the yields of methylcyclohexane and methylcyclohexanone, because of the increased acid functionality and diffusion constraints of intermediates. A low BAS/Pt ratio is beneficial for improving catalytic stability by reducing coke deposition.

Phenol Hydrodeoxygenation over a Reduced and Sulfided NiMo/γ-Al2O3 Catalyst

Phenol hydrodeoxygenation over a commercial NiMo/γ-Al2O3 catalyst in a reduced and sulfided form was investigated. Crushed particles (0.165–0.315 mm) were employed to determine the intrinsic reacti...