Associated with the carbonization of glucose in the hydrothermal process, MoS2/amorphous carbon composites were synthesized by a one-step hydrothermal method and characterized by various technologies. Introducing carbon into MoS2 increased its surface area and enlarged the edge-to-corner ratio of the MoS2 slab of the MoS2 phase, which contributed to a high deoxygenation degree in the hydrodeoxygenation (HDO) of p-cresol, but excessive carbon covered some MoS2 edges that acted as active sites for HDO reaction and lowered the conversion. The presence of water modified the surface structure of MoS2 and had a great effect on the HDO activity and product distribution. During the HDO reaction, sulfur–oxygen exchange at the edges of MoS2 resulted in the loss of S atoms and the intensity decrease of the (002) diffraction peak for MoS2 phase, which was accelerated by increasing the amount of added water. Carbon in MoS2 only acted as a support and had no preventing effect on water. When the added water was 0.2 g, i.e., water/p-cresol molar ratio was 0.5:1, after reaction at 275 °C for 8 h, toluene selectivity and deoxygenation degree increased to 91.3% and 94.2%, respectively.

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 HYD/DDO was attributed to the short slab length and high number of layers in stacks, respectively.

Hydrophobic reduced graphene oxide supported Ni-B-P-O and Co-B-P-O catalysts were synthesized by a chemical reduction method and these dispersed relatively well in a non-polar solvent, prevented contact with water, and consequently protected the active phases and exhibited high catalytic activity in the liquid-phase p-cresol hydrodeoxygenation reaction: both the conversion and deoxygenation degree were higher than 99% at 225 °C for 1 h.

CoS2/MoS2 catalysts were prepared using a two-step hydrothermal procedure for the first time, i.e., MoS2 was synthesized and then CoS2 was prepared and deposited on the surface of the MoS2. The characterization results presented that CoS2 and MoS2 are separated in the resultant catalysts and the surface area of CoS2/MoS2 was much higher than that of Co–Mo–S prepared using a one step method. In the hydrodeoxygenation (HDO) of p-cresol, the presence of CoS2 enhanced the conversion, but excessive CoS2 on the surface of the MoS2 reduced its activity. With an appropriate amount of CoS2, the catalyst presented an unprecedented HDO activity and direct deoxygenation (DDO) selectivity: 98% deoxygenation degree with a selectivity of 99% toluene at 250 °C for 1 h. This CoS2/MoS2 catalyst also exhibited high DDO activity for other phenolic monomers, which minimized hydrogen consumption and improved the economic efficiency.

•Flower-like Co–Mo–S catalyst was synthesized by a facile hydrothermal synthesis.•Co–Mo–S exhibited a high activity and aromatics selectivity in p-cresol HDO and benzothiophene HDS.•The synergy between CoS2 and MoS2 and flower-like morphology resulted in the high HDO activity.•Adding appropriate benzothiophene into the HDO of p-cresol on Co–Mo–S maximized the deoxygenation degree.•Adding p-cresol decreased the desulfidation activity in benzothiophene HDS because of the competitive adsorption.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.Flower-like Co–Mo–S catalyst was synthesized by a facile hydrothermal synthesis and exhibited high activity and aromatics selectivity in the HDO of p-cresol and HDS of benzothiophenes. Adding appropriate amount of benzothiophene into the HDO of p-cresol over Co–Mo–S enhanced the deoxygenation degree. In the simultaneous HDO and HDS reactions, the initial reaction rate constant for p-cresol/benzothiophene, DDO activity or desulfidation degree were decreased compared with that in single reactions.

•Two-step hydrothermal method was developed for the synthesis of NiS2//MoS2 catalysts.•NiS2 and MoS2 existed separately in the resultant catalysts.•NiS2//MoS2 catalyst presented a higher surface area and exposed more active sites.•Both methylcyclohexane selectivity and deoxygenation degree on NiS2//MoS2 catalysts were enhanced.•The hydrodeoxygenation mechanism was well explained by the Remote Control model via spillover hydrogen.NiS2//MoS2 catalysts with different Ni/Mo molar ratios were prepared by two-step hydrothermal method, i.e., MoS2 was firstly synthesized and then NiS2 was prepared and deposited on the surface of MoS2. The resultant catalysts were characterized by XRD, XPS, TEM, SEM, N2 physisorption and their activities were tested using the hydrodeoxygenation of p-cresol as a probe. The results showed that separated NiS2 and MoS2 phases rather than Ni–Mo–S phase existed in NiS2//MoS2 catalysts. In the HDO of p-cresol, NiS2 acted as a donor phase to provide spillover hydrogen, which migrated to MoS2 for reaction. Because of the particular synthesis procedure, NiS2//MoS2 had higher surface area to expose more active sites. When Ni/Mo molar ratio was adjusted to 0.3, p-cresol conversion and the deoxygenation degree reached to 98.5% and 95.4% at 275 °C for 4 h, respectively. The hydrogenation activity was enhanced in the presence of NiS2, leading to the increases on both methylcyclohexane selectivity and deoxygenation degree. NiS2//MoS2 catalysts prepared by this two-step synthesis method exhibited higher hydrodeoxygenation activity than that by other methods, presenting a good potential of this method for the synthesis of other bi-component sulfides with high catalytic activity.NiS2//MoS2 catalysts were prepared by two-step hydrothermal method and separated NiS2 and MoS2 phases were presented in the resultant catalysts. In the HDO of p-cresol, because of the large surface area to expose more active sites, these catalysts exhibited higher activity than that synthesized by other methods. Both methylcyclohexane selectivity and deoxygenation degree were enhanced.

An Ni–P–B amorphous nano-catalyst was synthesized using a facile chemical reduction method. The amorphous degree was enhanced and the transferred electron decreased with an increase of P content in Ni–P–B. In the hydrodeoxygenation (HDO) of p-cresol, the conversion using Ni–P–B was high up to 98.9% with a selectivity of 6.5% for toluene and a deoxygenation degree of 96.8% at 498 K.

In this study, bimodal mesoporous MoS2 nanosheets were successfully synthesized by a hydrothermal method. The effect of pH value, pressure, time and temperature in the preparation process of MoS2 on its structure property and catalytic activity were studied in detail. Low pH value and pressure were beneficial for the preparation of a MoS2 nanosheet with a large surface area and narrow bimodal pore distribution, which exposed more effective active sites on the surface and provided suitable space for reactants and products to diffuse in less resistance. But the acceleration hydrolysis of CS(NH2)2 at the low pH value enhanced the formation rate of MoS2 and then weakened the nanosheet structure. In the HDO of p-cresol, MoS2 exhibited high catalytic activity, and the dominant route was direct deoxygenation. After 4 h, both the conversion and deoxygenation degree reached 99.9% at 300 °C, and toluene selectivity was 66.2%. The HDO reaction mechanism could be well explained by the Rim-Edge model. The higher conversion in the HDO of p-cresol on MoS2 depended on the larger surface area and greater number of big pores of the catalyst, while the higher direct deoxygenation activity of MoS2 depended on the greater number of layers in its stacks.

Ni–Mo–S catalysts were prepared by sodium dodecyl benzene sulfonate (SDBS) assisted hydrothermal synthesis. The presence of SDBS increased the NiS2 crystallite size, enlarged the interlayer distance of MoS2 plane and formed loose flower-like architecture, which contributed to the enhanced HDO activity. Compared with Ni–Mo–S synthesized in the absence of SDBS, p-cresol conversion, methylcyclohexane selectivity and deoxygenation degree was increased by 24%, 25.1% and 26.3%, respectively.

This study focused on the preparation of Ce–Ni–W–B amorphous catalysts and the effect of Ce content on their catalytic activities in the hydrodeoxygenation (HDO) of phenols in bio-oil. Adding the promoter Ce could increase the content of Ni0 and WO3 on the Ce–Ni–W–B catalyst surface, leading to the improvement of the deoxygenation activity, but excess Ce would cover some active sites, resulting in a reduction of the catalytic activity. Because of the amorphous structure and the electron transfer between Ni0 and B0, these catalysts possess very high hydrogenation activity, making the HDO of phenols on these amorphous catalysts proceed with a hydrogenation-dehydration route, which not only decreases the aromatic content in the product but also the reaction temperature. With an optimal Ce content (2.5 mol%), the total aromatic selectivity reduced to 1.0% and the HDO reaction temperature decreased to 498 K. This research provides a high activity catalyst for transforming phenols into cycloalkanes.