Hydrodeoxygenation Of P-cresol Research Articles

Rational design of Ni-MoO3–x catalyst towards efficient hydrodeoxygenation of lignin-derived bio-oil into naphthenes

Design of a robust catalyst with high activity but the low cost for the hydrodeoxygenation (HDO) of bio-oils is of great importance to bring the biorefinery concept into reality. In this study, density functional theory (DFT) calculation was adopted to analyze the optimal location of Ni on MoO3–x containing oxygen vacancy, and the corresponding result demonstrated that metallic Ni cluster located at the neighborhood of oxygen vacancies would significantly evoke HDO activity. Enlightened by DFT results, NiMoO4 was first hydrothermally synthesized and then employed to fabricate Ni-MoO3–x catalyst via a low-temperature reduction, where Ni escaped from NiMoO4 and was reduced to its metallic state. Such an evolution of Ni species also induced the formation of oxygen vacancies around metallic Ni cluster. In the HDO of p-cresol, Ni-MoO3–x exhibited high activity with a complete conversion and a methylcyclohexane selectivity of 99.4% at 150 °C. Moreover, the catalyst showed good versatility in catalyzing HDO of diverse lignin-derived oxygenates and lignin oil. 2D HSQC NMR, gas chromatograph and elemental analysis of the lignin oil demonstrated the high deoxygenation efficiency and saturation of the benzene ring over Ni-MoO3–x. In the upgrading of crude lignin oil, the deoxygenation degree was up to 99%, and the overall carbon yield of the naphthenes was as high as 69.4%. Importantly, the structures and carbon numbers of the naphthene products are similar to jet fuel-range cycloalkanes, which are expected to have a high density that can be blended into jet fuel to raise the range (or payload) of airplanes. This work demonstrates the feasibility for improving the targeted catalytic reactivity by rational tailoring the catalyst structure under the guidance of theoretical analysis, and provides an energy-efficient route for the upgrading of lignin crude oil into valuable naphthenes.

Comparison of Co-Mo-S and remote control model for designing efficient Co-doped MoS2 hydrodeoxygenation catalysts

Co-promoted MoS2 catalysts as good candidates can effectively remove the oxygen in bio-oil through the hydrodeoxygenation (HDO) of phenolics. However, it is of great importance to maximize the synergistic effect between Co and MoS2 which is conductive to the design of highly efficient Co-doped MoS2 HDO catalysts. Herein, two model catalysts with Co-Mo-S and CoS2/MoS2 (remote control model) as the active phases were successfully constructed and evaluated in the HDO of p-cresol. It was found that Co-Mo-S catalyst showed a significantly higher intrinsic HDO activity than CoS2/MoS2 catalyst, and the synergy factor between Co dopant and MoS2 of Co-Mo-S was 3.1 times that of CoS2/MoS2. The greatly enhanced HDO performance of Co-Mo-S catalyst is attributed to remarkably weakened strength of MoS bond, which can facilitate the sulfur vacancies (Vs) formation on the sulfur edges and promote the reaction rate of direct deoxygenation (DDO) pathway. This work revealed that Co-Mo-S model could better promote the CoMo synergy than the remote control model so as to design more efficient MoS2-based catalysts for HDO reactions.

Hydrodeoxygenation of p-cresol over CuNi@C catalyst derived from metal-organic frameworks precursor

Catalytic hydrodeoxygenation is becoming more important industrially due to the urgent need for the conversion of oxygen-rich biomass into a renewable hydrocarbon energy source as means to tackle the climate change crisis. This research examined the catalytic hydrogenation of p-cresol as a model compound, using CuNi bimetallic nanoparticles incorporated into a carbon matrix (CuNi@C) as the catalysts, which were prepared using MOFs as the precursors. Various MOFs with varying molar content of nickel (Cu, CuNi0.2, CuNi0.5, CuNi0.8 and CuNi1.1) were prepared and used to derive the MOF-based bimetallic catalysts. The effect of the relative bimetallic compositions, surface morphology, and the oxidation of the metals of the catalysts was studied at different hydrogenation reaction temperatures varying from 200 to 300 °C. Advanced characterisations demonstrate that the MOF-derived Cu/Ni carbon nanocomposite catalyst at a Cu/Ni mole ratio of 0.5 (CuNi0.5/C) shows the highest catalytic activities at 300 °C, giving rise to a conversion rate of 80.3% and selectivity of 82.7% for the formation of 4-methylcyclohexanol (hydrogenation pathway). Cyclic hydrogenation tests also reveal that the CuNi0.5/C showed the highest thermochemical stability with a negligible decrease in catalytic activity despite the high temperature examined for a fast conversion. The preliminary results augur well for the sound promise of using corresponding MOFs derived novel catalysts for hydrogenation application.

Creating Edge Sites within the Basal Plane of a MoS2 Catalyst for Substantially Enhanced Hydrodeoxygenation Activity

A two-dimensional MoS2 catalyst uses edge sites for catalytic activity while its basal plane remains inert in heterogeneous catalysis. To significantly boost the intrinsic activity of MoS2, a metal insertion–deinsertion procedure was developed to prepare Pt–MoS2–x catalysts. Of which, Pt4+ partially substituted Mo4+ in the basal plane of 1T-MoS2–x and then Pt was deinserted from the basal plane after reduction and finally located at the neighborhood of its original position, where abundant edge sites were created and rich Pt–edge interfaces were formed in the “inert” basal plane of MoS2. This Pt–MoS2–x exhibited high activity in hydrodeoxygenation of p-cresol, presenting in 100% oxygen removal at a low temperature of 120 °C and almost no sulfur loss nor deactivation in recycling runs. A Pt–MoS2–x catalyst was also efficient in hydrodeoxygenation of diverse lignin model compounds and lignin-derived bio-oil. This methodology opens up an innovative strategy for the design of robust MoS2 catalysts featuring the activation of the basal plane and provides an energy-efficient alternative for the upgradation of raw bio-oil.

Co-promoted few-layer and defect-rich MoS2 for enhanced hydrodeoxygenation of p-cresol

Unsupported CoMo sulfide catalysts are good candidates in the hydrodeoxygenation (HDO) of phenol compounds to aromatics which is important for bio-oil upgrading. However, the key to prepare efficient catalysts is how to increase the content of Co-Mo-S active phase as much as possible. Herein, a dual strategy of layer and defect engineering was realized for the synthesis of few-layer and defect-rich MoS2 (MoS2-FL-DR) through a simple one-pot hydrothermal method. By decreasing the layer number and manufacturing abundant defects on the basal planes, more coordinatively unsaturated sites (CUS) were formed to provide additional sites to accommodate Co atoms. After promoted with Co, Co/MoS2-FL-DR exhibited an excellent performance in the HDO of p-cresol, with p-cresol conversion of 100 % and toluene selectivity of 99.7 % at 230 °C. This catalyst also showed a relative good stability after reaction for 72 h. The excellent performance was attributed to the few-layer and defect-rich structure of MoS2 and the formation of large amount Co-Mo-S active phase.

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.

Understanding the promoter effect of bifunctional (Pt, Ni, Cu)-MoO3-x/TiO2 catalysts for the hydrodeoxygenation of p-cresol: A combined DFT and experimental study

The effect of Pt, Ni, and Cu promoters on the partial reduced MoO3-x/TiO2 catalysts for the hydrodeoxygenation (HDO) reaction of p-cresol was investigated through experiments and density functional theory (DFT) calculations. The MoO3-x/TiO2 was firstly prepared and then Pt, Ni, or Cu precursor was introduced. The mixed Mo4+, Mo5+, and Mo6+ states were identified by XPS. The HR-TEM and TEM-EDX images suggest that the MoO3-x becomes amorphous and is well-dispersed on TiO2 supports leading to direct contact of the metal on MoO3-x/TiO2. The HDO of p-cresol under a low hydrogen pressure (5 bar) at 300 °C showed the %conversion as the following order: Pt-MoO3-x > Ni-MoO3-x > Cu-MoO3-x > MoO3-x. DFT results explained the differences of catalytic performance of the catalysts and the role of the promoters in enhancing the H2 activation. The high electronegativity and density of state near the Fermi level are responsible for the high catalytic performance of Pt-MoO3-x/TiO2, which shows barrierless for H2 dissociation and allows this catalyst to be active under a milder reaction temperature and pressure. These results deepen the fundamental understanding of the role of the promoters toward the key reaction step in HDO, which is beneficial for guiding the development of catalysts for biomass conversion.

N2 catalyzes p-cresol transformation

Gaseous nitrogen is a bit of a chemical wallflower. While high temperatures and pressures such as those used in the Haber-Bosch process can convince the compound to react, gaseous N2 rarely acts as an active catalytic species. Now a group of international researchers has found that adding N2 gas to a ruthenium-based catalyst speeds up the hydrodeoxygenation of p-cresol into toluene by over 400%; it’s a reaction that could have applications in converting bio-oils into useful chemicals (Nat. Catal. 2019, DOI: 10.1038/s41929-019-0368-6). Led by Jun Li from Tsinghua University and Edman Tsang and Dermot O’Hare from the University of Oxford, the researchers stumbled across this chemistry when trying to pressurize their reactor with an inert gas, O’Hare says. They added gaseous N2 to a solid-state titanium oxide–supported Ru catalyst, with hydrogen gas and p-cresol, and found that the Ru surface activates the N2 to form either N2H or N2H2. These

Preparation of Fe promoted MoS2 catalysts for the hydrodeoxygenation of p-cresol as a model compound of lignin-derived bio-oil

Fe promoted MoS2 catalysts were prepared by one-step hydrothermal method and then applied into the hydrodeoxygenation (HDO) of p-cresol as a model compound of lignin-derived bio-oil. The as-prepared samples had FeS2 and MoS2 phases with low crystallinity. After further hydrogen-treatment at 250 °C in dodecane, some peaks to FeS phase were observed. The surface area of Fe promoted MoS2 catalyst decreased firstly and then increased with Fe content in the catalysts increasing. In the HDO of p-cresol, the addition of Fe sulfides into MoS2 enhanced conversion and toluene selectivity. When the Fe/Mo molar ratio is 0.7:1, the conversion and deoxygenation degree reached up to 96.3% and 95.7% after reaction at 250 °C for 3 h, respectively. The high HDO activity was attributed to the synergistic effect and contact surface area between Fe sulfides and MoS2. During the HDO recycling reaction, the deactivation was observed, which resulted from the sulfur loss and the formation of Fe oxides, but its activity could be regenerated after a simple sulfuration procedure.

Preparation of Al-based layered double hydroxides and corresponding mixed oxides supported Pt catalysts and their performance in the hydrodeoxygenation of p-cresol

Al-based layered double hydroxides and corresponding mixed oxides were prepared and used as the supports for the Pt based catalysts; their catalytic performance in the hydrodeoxygenation (HDO) of p-cresol was then investigated. The results indicate that the catalytic performance of Pt based catalysts is related to the composition and structure of the support; Pt directly supported on the Al-based layered double hydroxides exhibits higher activity in p-cresol HDO than that supported on corresponding mixed oxides. Especially, for the HDO at 275°C and 2 MPa for 1 h, the conversion of p-cresol over Pt-Ni-Al-H is 99.8%, with a selectivity of 1.4% to toluene, whereas the selectivity to toluene over Pt-Zn-Al-H reaches 84.1%. Moreover, the Pt based catalysts are also active for the dehydrogenation of methylcyclohexane to toluene, which can effectively reduce the hydrogen consumption in HDO.

Hydrodeoxygenation of p-cresol as a model compound for bio-oil on MoS2: Effects of water and benzothiophene on the activity and structure of catalyst

MoS2 was prepared by a hydrothermal method and then applied into the hydrodeoxygenation (HDO) of p-cresol as a model compound for bio-oil to study the effects of water and benzothiophene on the conversion, product distribution and stability in detail. The presence of water enhanced the HDO activity and decreased the hydrogen consumption: the deoxygenation degree and toluene selectivity reached to 97.0% and 88.0%, respectively. When water was replaced by benzothiophene, p-cresol conversion increased to 92.3% with toluene selectivity of 72.4%. With water and benzothiophene simultaneously introduced, at 275 °C and 4.0 MPa, the conversion and toluene selectivity were 86.0% and 79.1%, respectively. The reaction temperature and hydrogen pressure were also significant factors. The conversion was raised to 97.4% with toluene selectivity of 80.1% when the reaction temperature increased to 300 °C, but decreased to 71.7% with toluene selectivity of 77.2% when hydrogen pressure increased to 5.0 MPa. The characterization results of the spent catalysts indicated that some defects in the (0 0 2) plane of MoS2 caused by the loss of sulfur were observed after the HDO reaction, which resulted in its deactivation. This deactivation was accelerated by adding water but inhibited by adding benzothiophene.

Facile hydrothermal synthesis of flower-like Co–Mo–S catalysts and their high activities in the hydrodeoxygenation of p-cresol and hydrodesulfurization of benzothiophene

Co–Mo–S catalysts were synthesized by a facile hydrothermal synthesis and their activities were tested in the hydrodeoxygenation (HDO) of p-cresol, hydrodesulfurization (HDS) of benzothiophene, and simultaneous HDO of p-cresol and HDS of benzothiophene. When Co/Mo mole ratio in Co–Mo–S was adjusted to 0.3, the catalyst presented a flower-like morphology and exhibited high HDO and HDS activity, which was attributed to its specific structure and the maximum synergy between CoS2 and MoS2. In the HDO of p-cresol, direct deoxygenation (DDO) was the main reaction route and toluene selectivity reached to 97.5%. The hydrogen consumption was markedly cut down. By adding small amount of benzothiophene, p-cresol conversion was enhanced because the produced H2S from the HDS of benzothiophene slowed down the catalyst deactivation. In simultaneous HDO of p-cresol and HDS of benzothiophene, because of the competitive adsorption of reactants on the active sites, both the toluene selectivity and desulfurization degree were lowered compared with the single component reactions.

Microwave-assisted hydrothermal synthesis of amorphous MoS2 catalysts and their activities in the hydrodeoxygenation of p-cresol

MoS2 was fast synthesized by microwave-assisted hydrothermal method using MoCl5 and (NH2)2CS as starting materials and exhibited high activity: the deoxygenation degree reached to 92.4% in the HDO of p-cresol at 300 °C for 6 h.

Preparation of Ni–Mo–S catalysts by hydrothermal method and their hydrodeoxygenation properties

Unsupported Ni–Mo–S catalysts with different Ni/(Ni+Mo) molar ratio were prepared by hydrothermal method using ammonium heptamolybdate and thiocarbamide as materials. The resultant catalysts were characterized by X-ray diffraction, nitrogen physisorption and transmission electron microscopy, and their activities were measured using the hydrodeoxygenation (HDO) of p-cresol as a probe reaction. The addition of Ni promoter caused a reduction in the surface area. The peaks attributed to NiS2 on catalyst surface became noticeable as the Ni content increased in the catalyst. The catalyst with an optimal Ni/(Ni+Mo) molar ratio (0.3) exhibited the highest activity (99.8% deoxgenation degree at 300°C and 4.0MPa hydrogen pressure for 6h). The HDO of p-cresol on these prepared Ni–Mo–S catalysts proceeded with two parallel routes: hydrogenation-dehydration (HYD) and direct deoxygenation (DDO), and HYD/DDO closely related to the Ni/(Ni+Mo) molar ratio in the catalyst, the HDO reaction temperature and H2 pressure. The comparison of Ni–Mo–S with MoS2–NiS2 (prepared by two hydrothermal method) and MoS2+NiS2 (prepared by physically mixing separately MoS2 and NiS2) indicated that the high HDO activity of Ni promoted MoS2 catalyst was attributed to the synergistic effect of MoS2 and NiS2 rather than the formation of Ni–Mo–S phase, which could be well explained by the remote control model.

Synthesis of Highly Active Co–Mo–S Unsupported Catalysts by a One-Step Hydrothermal Method for p-Cresol Hydrodeoxygenation

Because of energy crisis, how to minimize hydrogen consumption and improve the catalytic activity is of importance for the hydrodeoxygenation (HDO) of phenols. In this study, Co–Mo–S catalysts were prepared by a one-step hydrothermal method, and their properties were characterized by nitrogen physisorption, X-ray diffraction, and transmission electron microscopy. The effects of Co content and catalyst preparation temperature on the catalytic activity were studied using the HDO of p-cresol as a probe. The effects of reaction conditions such as temperature and hydrogen pressure on the conversion and product distribution were also studied. Adding Co into the MoS2 catalyst decreased its surface area but increased the HDO activity and reduced the hydrogen consumption. The HDO of p-cresol on Co–Mo–S proceeded with two separate reaction routes: hydrogenation–dehydration (HYD) and direct deoxygenation (DDO). The HDO active sites were well explained by the Rim–Edge model. The high conversion of p-cresol and low HY...

Hydrodeoxygenation of p-cresol on MoS2: the effect of adding hexadecyl trimethyl ammonium bromide during the catalyst synthesis

This study prepared unsupported MoS2 catalysts by a one-step hydrothermal method using ammonium heptamolybdate and thiocarbamide as materials. The morphology and microstructure of MoS2 catalysts were changed by adding different amounts of hexadecyl trimethyl ammonium bromide (CTAB). The resultant catalysts were characterized by X-ray diffraction, nitrogen physisorption and transmission electron microscopy. The surface area and pore volume of MoS2 increased first and then decreased with the addition amount of CTAB. The structural difference between these catalysts lies in the number of layers in stacks and slab length of MoS2 structure. The structure–activity correlation was studied by using the hydrodeoxygenation (HDO) of p-cresol as the probe reaction. In the HDO of p-cresol, the end products were toluene, 4-methylcyclohexene and methylcyclohexane, and the possible HDO reaction routes were proposed. The effects of addition of CTAB during the synthesis of MoS2 and HDO reaction temperature on conversion and products distribution were analyzed. The changes of product distribution were explained based on the Rim-Edge model. The direct deoxygenation (DDO) route occurs on the edge active sites while the hydrogenation–dehydration (HYD) route occurs on brim sites of multi-stacks MoS2 particles. Thus, the slab length and slab stacking layers had a great effect on the catalytic activity of MoS2 and products distribution.

Hydrodeoxygenation of p-cresol on unsupported Ni–W–Mo–S catalysts prepared by one step hydrothermal method

Unsupported Ni–Mo–W sulfide catalysts were prepared by one step hydrothermal method using ammonium heptamolybdate and thiocarbamide in water, and characterized by X-ray diffraction (XRD), nitrogen physisorption and transmission electron microscopy (TEM). The effect of W/Mo molar ratio on the catalytic performance was studied using the HDO of p-cresol as a probe. The results showed that the Ni–Mo–W–S catalyst with an appropriate W/Mo molar ratio possesses the short slab length of MoS2 or WS2 structure and many active sites, leading to the high HDO activity and HYD selectivity.

Hydrodeoxygenation of p-cresol on unsupported Ni–P catalysts prepared by thermal decomposition method

Abstract Unsupported Ni–P catalysts were prepared from the mixed precursor of NiCl2 and NaH2PO2 by thermal decomposition method, and their catalytic activities were measured using the hydrodeoxygenation (HDO) of p-cresol as probe. The effects of the H2PO2−/Ni2 + molar ratio in the precursor and the thermal decomposition temperature on the catalyst purity, crystallite size and HDO activity were studied. The HDO of p-cresol on these Ni–P catalysts proceeded with two parallel pathways yielding methylbenzene and methylcyclohexane as final products. The higher HDO catalytic activity of the catalyst was attributed to its bigger crystallite size and purer phase of Ni2P.