Jinfu Wang

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: Reaction and separation

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of techniques. A new process that used the coupling of the reaction and separation was employed, which greatly improved the conversion of cottonseed oil (triglyceride) and free fatty acids (FFA) when a model waste oil feedstock was used. The vegetable oil asphalt-based catalyst showed the highest catalytic activity. This was due to the high density and stability of its acid sites, its loose irregular network, its hydrophobicity that prevented the hydration of -OH species, and large pores that provided more acid sites for the reactants.

Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H2SO4 on TiO2 · nH2O and Zr(OH)4, respectively, followed by calcining at 823K. TiO2-SO42− and ZrO2-SO42− showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Brønsted acid sites on the catalysts.

Application of Doppler ultrasound velocimetry in multiphase flow

Abstract This work aims to extend the application of a commercial Doppler ultrasound velocimetry DOP2000 (Model 2030, signal processing S.A.) to multiphase systems. We firstly make a correction to the determination of Doppler angle and measuring location taking into account the ultrasound refraction and the ultrasound velocity difference in different medias, and then investigate the measurement of the solid concentration in a liquid–solid system and the bubble behavior in a gas–liquid system with low gas holdup. The experimental results show that the attenuation coefficient increases monotonously. A model based on the ultrasound reflection and refraction law is proposed to predict the received echo energy in homogeneous liquid–solid system. Furthermore, the signal response of bubbles is also discussed. By placing the probe in the direction of the flow, the difficulty of determining Doppler angle is avoided and the liquid and bubble rise velocities are simultaneously obtained.

Fluidization of coarse particles in gas–solid conical beds

Abstract In this paper, three flow regimes, such as fixed bed, partially fluidized bed and fluidized bed (or spouting bed), are observed successively with the increase of superficial gas velocity for a Geldart-D powder in a conical bed with three cone angles. The conditions of the regime transition and the hydrodynamics for the three flow regimes have been studied experimentally and systematically. The experimental results show that the bed cone angle and the particle bed height are the main factors influencing the regime transition and hydrodynamics of the particle bed. The measurements are compared with calculated results from relevant models and correlations. The predicting capability of the different models and correlations has been discussed. The mechanism for the occurrence of partial fluidization has also been analyzed and a correlation between the spouting pressure drop and the stagnant bed height H m is given based on the experimental measurements.

Silica white obtained from rice husk in a fluidized bed

Abstract In this paper, silica white, which is obtained from rice husk in a fluidized bed, is investigated. First, the experiments are carried out in the cold fluidized bed of 90-mm interior diameter (I.D.). The experimental results show that the ash mixed with a little rice husk can be fluidized when U g is within the range of 0.18–0.316 m/s. Then, the experiments of combustion of rice husk are investigated in the fluidized bed of 84 mm I.D. The experimental results show that the combustion occurs in the dense zone of the fluidized bed. The ash in the dense zone is easily purified to obtain the SiO 2 powder. The quality of silica white sampled from the dense phase zone is higher than that of GB-precipitated silica and approaches that of pyrogenic silica except for specific surface area and iron content.

Reaction Kinetics of Biodiesel Synthesis from Waste Oil Using a Carbon-based Solid Acid Catalyst

Abstract The kinetics of simultaneous transesterification and esterification with a carbon-based solid acid catalyst was studied. Two solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. These catalysts were characterized on the basis of elemental analysis, acidity site concentration, the Brunauer-Emmett-Teller (BET) surface area and pore size. The kinetic parameters with the two catalysts were determined, and the reaction system can be described as a pseudo homogeneous catalyzed reaction. All the forward and reverse reactions follow second order kinetics. The calculated concentration values from the kinetic equations are in good agreement with experimental values.

The synergy effect of process coupling for dimethyl ether synthesis in slurry reactors

The synergy effect of process coupling of reaction-reaction and reaction-heat transfer for dimethyl ether synthesis has been studied. The theoretical and experimental analyses show that the synergy of reaction-reaction is prominent and that the synergy of reaction-heat transfer is also feasible. Due to the synergy effect, CO-rich synthesis gas can be used for dimethyl ether synthesis and higher once-through conversion of CO can be obtained. Recycling and compression of the unreacted synthesis gas can be minimized considerably. Accordingly, savings will be made in energy consumption and the water gas shift reaction system, and the entire investment and production cost will decrease.

Bubble behavior in gas–liquid–solid three-phase circulating fluidized beds

Abstract A novel fiber optic probe system has been developed for studying the bubble behavior in gas–liquid–solid three-phase circulating fluidized beds (TPCFBs). Mathematical method to analyze data by probe technique has also been discussed in this paper. The bubble size and its distribution, bubble Sauter diameter, gas–liquid interfacial area and bubble rise velocity, have been experimentally studied using the fiber optic probe. The experimental results show that the bubble size distribution in TPCFBs follows lognormal function. The bubble Sauter diameter has the radial profile with smaller value in the central region than in the near-wall region, different from the conventional three-phase fluidized beds (CTPFBs) without outer particle circulation. The distribution of bubble rise velocity, gas–liquid interfacial area and effect of the operation conditions have been experimentally studied.

Methanol Synthesis from CO2 Hydrogenation with a Cu/Zn/Al/Zr Fibrous Catalyst

A highly active Cu/Zn/Al/Zr fibrous catalyst was developed for methanol synthesis from CO2 hydrogenation. Various factors that affect the activity of the catalyst, including the reaction temperature, pressure and space velocity, were investigated. The kinetic parameters in Graafs kinetic model for methanol synthesis were obtained. A quasi-stable economical process for CO2 hydrogenation through CO circulation was simulated and higher methanol yield was obtained.

Mass Transfer Characteristics of Syngas Components in Slurry System at Industrial Conditions

The gas-liquid mass transfer behavior of syngas components, H 2 and CO, has been studied in a three-phase bubble column reactor at industrial conditions. The influences of the main operating conditions, such as temperature, pressure, superficial gas velocity and solid concentration, have been studied systematically. The volumetric liquid-side mass transfer coefficient k L a is obtained by measuring the dissolution rate of H 2 and CO. The gas holdup and the bubble size distribution in the reactor are measured by an optical fiber technique, the specific gas-liquid interfacial area a and the liquid-side mass transfer coefficient k L are calculated based on the experimental measurements. Empirical correlations are proposed to predict k L and a values for H 2 and CO in liquid paraffin/solid particles slurry bubble column reactors.