Zhilin Wu

Ultrasound-assisted oxidative desulfurization of liquid fuels and its industrial application

Latest environmental regulations require a very deep desulfurization to meet the ultra-low sulfur diesel (ULSD, 15 ppm sulfur) specifications. Due to the disadvantages of hydrotreating technology on the slashing production conditions, costs and safety as well as environmental protection, the ultrasound-assisted oxidative desulfurization (UAOD) as an alternative technology has been developed. UAOD process selectively oxidizes sulfur in common thiophenes in diesel to sulfoxides and sulfones which can be removed via selective adsorption or extractant. SulphCo has successfully used a 5000 barrel/day mobile Sonocracking unit to duplicate on a commercial scale its proprietary process that applies ultrasonics at relatively low temperatures and pressures. The UAOD technology estimate capital costs less than half the cost of a new high-pressure hydrotreater. The physical and chemical mechanisms of UAOD process are illustrated, and the effective factors, such as ultrasonic frequency and power, oxidants, catalysts, phase-transfer agent, extractant and adsorbent, on reaction kinetics and product recovery are discussed in this review.

Removal of blue-green algae using the hybrid method of hydrodynamic cavitation and ozonation.

A suspension of Microcystis aeruginosa (30 μg L(-1)chlorophyll a) was circulated in a hydrodynamic cavitation device and ozone was introduced at the suction side of the pump. The removal of algae over 10 min using hydrodynamic cavitation alone and ozone alone is less than 15% and 35%, respectively. The destruction of algae rises significantly from 24% in the absence of the orifice to 91% with the optimized orifice on 5 min of processing using hydrodynamic cavitation along with ozone (HC/O(3)) and the utilization of ozone increases from 32% to 61%. Interestingly, the suction process is more effective than the extrusion method (positive pressure) and the optimal bulk temperature for algal elimination was found to be 20 °C. Increasing the input concentration of ozone is favorable for the removal of algae but leads to a greater loss of ozone and a decrease in the utilization of ozone. Under the optimal conditions, the algal cells and chlorophyll a are completely destroyed in 10 min by use of the hybrid method.

Enhancement of chloroform degradation by the combination of hydrodynamic and acoustic cavitation.

The decomposition of chloroform by the combination of hydrodynamic and acoustic cavitation (Hydrodynamic-Acoustic-Cavitation/HAC) has been investigated. The flow rate and the hole diameter of the orifice plate remarkably affect the conversion of chloroform in the combined system. The conversion increases with increasing fluid velocity without any restriction. With a 2.8mm orifice plate the conversion reaches an optimal value. A synergistic effect has been obtained by the hybrid method of acoustic and hydrodynamic cavitation. The total synergistic effect achieves 17% and 73% per pass, respectively. The analysis of the energy efficiencies shows different results. Due to high optimization potential, this hybrid method can be visualized as a new step for wastewater treatment.

Enhanced effect of suction-cavitation on the ozonation of phenol.

800mL of 1.0mM phenol-containing aqueous solution was circulated at 20°C for 30 min in a suction-reactor, while 3.2 mg min(-1) ozone was introduced into the solution under the suction orifice. The removal rates of phenol vary polynomially with the orifice diameter as well as the suction pressure. The rate constant for the zero-order kinetics achieves the highest value at -0.070 MPa by using 5mm orifice. Although the suction-cavitation alone cannot remove phenol in 30 min, it can considerably enhance the ozonation of phenol. The rate constants for the zero-order kinetics by the simple ozonation and the combined method are 0.018 and 0.028 min(-1), respectively. Furthermore, no ozone was observed in the tail gas during the first 15 min for the ozonation in the suction reactor, and then the concentration of unreacted ozone slowly increased, indicating that the utilization rate of ozone is significantly improved by the suction-cavitation. The increasing input concentration of ozone obviously accelerates the ozonation of phenol, but the total required quantities of ozone are very close by various ozone input concentrations to reach the same degradation rate, indicating the ozonation assisted by the suction-cavitation can be considered as a quantitative reaction.

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

The reduction of organic compounds through catalytic hydrogenation is an important transformation in organic chemistry, especially in the synthesis of fine chemicals, natural products, and pharmaceuticals. This review mainly focuses on the selective reduction of substrates with multiple functional groups. Literature from the last two decades has proved the pivotal role that ultrasound and microwaves can play not only in the preparation of environmentally friendly, efficient catalysts but also in their use in catalytic reactions. Owing to the specific selective activation of the solid catalyst surface, dielectric heating and acoustic cavitation may dramatically enhance the reaction rate and selectivity. A thorough literature survey was the first step in the MAPSYN project (EU 7th Framework Program) and has the goal of the industrial demonstration of selective hydrogenations intensified by microwaves and ultrasound. Both techniques are irreplaceable tools in heterogeneous catalysis and can be expected to bring even greater success in the near future as processes are scaled up with suitable flow reactors equipped with on‐line analytical monitoring.

Adsorption behavior of phenanthrene onto coal-based activated carbon prepared by microwave activation

Coal-based activated carbon (CAC) was prepared from coal produced in Xinjiang of China by microwave activation. CAC was characterized and used as an adsorbent for phenanthrene adsorption. The effects of temperature, adsorption time, CAC amount, initial concentration and pH value of solution on phenanthrene adsorption were studied. The adsorption rate of phenanthrene onto CAC was obtained nearly 100% with initial concentration of 100 mg/L and CAC dosage of 0.3 g at 25 °C. Phenanthrene adsorption was well described with the Langmuir isotherm. The pseudo-second-order model was found to more effectively explain the adsorption kinetics of phenanthrene. The lower temperature was favorable to the adsorption rate and equilibrium adsorption capacity of phenanthrene onto CAC. The thermodynamic parameters ΔHθ, ΔSθ and ΔGθ computed for phenanthrene adsorption onto CAC demonstrate the process was spontaneous, radiative, and entropically driven. Thus, CAC prepared by microwave activation could be effective for removing phenanthrene.

Sonoelectrochemical degradation of phenol in aqueous solutions.

The sonoelectrochemical degradation of phenol in aqueous solutions with stainless steel electrodes and high-frequency ultrasound (850kHz) was investigated. A 60% synergetic effect was obtained in the combined reaction system. High concentration of electrolyte (sodium sulfate) and a high electrical voltage are favorable conditions for the degradation of phenol. A nearly complete degradation of phenol was achieved with 4.26g/L Na(2)SO(4) and 30V electrical voltages at 25°C in 1h. The degradation of phenol follows pseudo-first order kinetics. Considering costs and application, the energy efficiency of the reaction system with different reaction conditions was evaluated.

Ultrasound‐ and Microwave‐Assisted Preparation of Lead‐Free Palladium Catalysts: Effects on the Kinetics of Diphenylacetylene Semi‐Hydrogenation

The effect of environmentally benign enabling technologies such as ultrasound and microwaves on the preparation of the lead‐free Pd catalyst has been studied. A one‐pot method of the catalyst preparation using ultrasound‐assisted dispersion of palladium acetate in the presence of the surfactant/capping agent and boehmite support produced the catalyst containing Pd nanoparticles and reduced the number of pores larger than 4u2005nm in the boehmite support. This catalyst demonstrated higher activity and selectivity. The comparison of kinetic parameters for diphenylacetylene hydrogenation showed that the catalyst obtained by using the one‐pot method was seven times as active as a commercial Lindlar catalyst and selectivity towards Z‐stilbene was high. Our work also illustrated that highly selective Pd/boehmite catalysts can be prepared through ultrasound‐assisted dispersion and microwave‐assisted reduction in water under hydrogen pressure without any surfactant.

Microwave-Assisted Synthesis of Carbon-Based (N, Fe)-Codoped TiO2 for the Photocatalytic Degradation of Formaldehyde

A microwave-assisted sol–gel method was used to synthesize (N, Fe)-codoped activated carbon (AC)/TiO2 photocatalyst for enhanced optical absorption in the visible light region. The prepared samples were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, ultraviolet–visible light spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The results showed no significant difference in the surface area of AC/TiO2 (approximately 500xa0m2/g) after doping. TiO2 was uniformly distributed on the surface of AC, which exhibited coexisting anatase and rutile structures with a mean crystallite diameter of approximately 20xa0nm. N and Fe monodoping on AC/TiO2 reduced the energy band gap of TiO2 to 2.81 and 2.79xa0eV, respectively, which mainly attributed to the impurity energy formed in the energy gap of TiO2. In (N, Fe)-codoped AC/TiO2, N and Fe are incorporated into the TiO2 framework and narrow the band gap of TiO2 to 2.58xa0eV, thereby causing a large redshift. Codoping of N and Fe enhanced the production of hydroxyl radicals (⋅OH) and improved the photocatalytic activity of the resultant AC/TiO2 compared with those of undoped and N- or Fe-monodoped AC/TiO2. N-Fe-AC/TiO2 degraded 93xa0% of the formaldehyde under Xe-lamp irradiation. Moreover, the photocatalyst was easily recyclable. In summary, a novel and efficient method to mineralize low concentrations of HCHO in wastewater was discovered.

Oxidation of Primary Aromatic Amines under Irradiation with Ultrasound and/or Microwaves

Abstract The oxidation of primary aromatic amines, p-methylaniline, p-ethylaniline and p-chloroaniline to the corresponding azo- and azoxy-compounds has been observed in ultrasound and/or microwaves systems. The individual irradiation of microwaves and its simultaneous irradiation with ultrasound obviously elevate the conversion of amines, as compared with the individual irradiation of ultrasound and the heating in a plain water bath. However, the formation of formamidine resulted in poor selectivity toward azo and azoxy products in the presence of dimethylformamide (DMF).