Yunquan Yang

Hydrothermal synthesis of bimodal mesoporous MoS2 nanosheets and their hydrodeoxygenation properties

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.

Influence of ultrasonic on the preparation of Ni-Mo-B amorphous catalyst and its performance in phenol hydrodeoxygenation

Abstract The amorphous Ni–Mo–B catalysts were prepared by ultrasonic as well as regular chemical reduction and characterized by BET, SEM, XRD, XPS, and FTIR. Their catalytic activity in the hydrodeoxygenation of phenol was evaluated. The influences of the catalyst preparation conditions and the reaction temperature on the phenol hydrodeoxygenation were investigated, and a reaction mechanism was proposed. The results showed that the particle size, agglomeration phenomenon, surface area, and MoO 2 and B content of the Ni–Mo–B catalysts can be regulated by introducing the ultrasonic treatment into the chemical reduction, which is effective to enhance their catalytic activity in phenol hydrodeoxygenation. At 498 K, the conversion of phenol is 81.08% and the hydrodeoxygenation selectivity reaches 93.39%.

Highly selective catalytic hydrodeoxygenation of Caromatic–OH in bio-oil to cycloalkanes on a Ce–Ni–W–B amorphous catalyst

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.

Preparation of hydrophobic reduced graphene oxide supported Ni-B-P-O and Co-B-P-O catalysts and their high hydrodeoxygenation activities

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.

Study of mean diameter and drop size distribution of emulsion drops in a modified rotating disc contactor for an emulsion liquid membrane system

To improve the dispersity of the emulsion phase in an emulsion liquid membrane (ELM) system, a modified rotating disc contactor (MRDC) was developed. Then, the Sauter mean diameter (d32) of emulsion drops and their drop size distribution were measured by photographic method and analyzed by an image processing program in MATLAB. The effects of rotating speed, flow ratio, total flow, stirring paddle width and surfactant concentration on the drop size and its distribution were studied. The results show that, with the increase in the rotating speed and the paddle width, the degree of turbulence was enhanced which led to the reduction in the drop size. Meanwhile, membrane breakage increased with the turbulent fluctuation, which resulted in the leakage of the internal phase. Fortunately, the membrane breakage could be prevented by a suitable increase in the surfactant concentration. In addition, the drop size decreased with the increase in the surfactant concentration. Besides, the increase in the emulsion phase flow obviously increased the drop size, whereas the increase in the continuous phase flow induced the entrainment of small drops. An empirical correlation for the prediction of the d32 was established with an average absolute relative error (AARE) of 4.1%. The drop size distribution based on the drop volume was accurately fitted with a normal distribution, and its probability density function parameters (α and β) were well predicted by the dimensionless correlations, with the AAREs of 4.2% and 5.9%, respectively.

Synthesis of Ni–P–B amorphous nanoparticles with uniform size as a potential hydrodeoxygenation catalyst

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.

Highly selective catalytic conversion of phenols to aromatic hydrocarbons on CoS2/MoS2 synthesized using a two step hydrothermal method

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.

Experimental and modeling of nickel removal from sulfate solutions by emulsion liquid membrane using PC 88A

AbstractThe removal of nickel from sulfate media using emulsion liquid membrane with PC 88A as carrier was studied by simulation and experimental method. Combining reasonable assumptions from the existing models, a modified mathematical model was developed. It was assumed that the concentrations at the external interface were in dynamic equilibrium. The mass transfer rate of the nickel–carrier complexes at the interface of the emulsion droplet and that of the nickel ions in the external feed solution were assumed to be equal. According to these modifications, the computational results could agree well with the experimental data. The total average value of the squared residuals was less than 0.022. The effects of agitation speed, volume ratio, and the concentration of the nickel ions and that of the PC 88A on the removal rate of nickel were investigated. The concentration of the PC 88A has shown greater influence on the nickel removal in comparison with the other parameters. Under typical conditions, the r...

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

Based on the normal hydrothermal method, MoS2 amorphous catalysts were synthesized by using molybdenum(V) chloride to replace molybdate under microwave conditions. The catalysts with different structures and morphologies were obtained by changing the synthesis conditions such as pH value, reaction time, temperature and S/Mo molar ratio and their activities were tested in the hydrodeoxygenation (HDO) of p-cresol. The results showed that the structure of MoS2 and its catalytic activity were mainly influenced by the pH value in the synthesis procedure. The surface area decreased with the reduction of pH value. MoS2 possessed a sheet-like shape when the pH was adjusted to an appropriate value. The catalyst synthesis conditions for MoS2 had little effect on the product distribution but affected the conversion in the HDO of p-cresol. The HDO activity of MoS2 depended on the sheet-like shape and slab length. High reaction temperature was beneficial to enhance the deoxygenation degree. The prepared MoS2 had good stability during the reaction, and also presented high activity in the HDO of other phenols such as phenol, o-cresol and 4-ethylphenol. This facile process was easy to operate and the synthesis time for MoS2 was shortened to 0.5 h, which demonstrated its superiority and efficiency.

SDBS-assisted hydrothermal synthesis of flower-like Ni–Mo–S catalysts and their enhanced hydrodeoxygenation activity

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.