Shyamal K. Bej

Effect of diluent size on the performance of a micro-scale fixed bed multiphase reactor in up flow and down flow modes of operation

The comparative behaviors of a micro-scale fixed bed multiphase reactor in up flow and down flow modes of operation were studied for hydrodesulfurization of atmospheric gas oil over a commercial catalyst. The experiments for the two modes of operation were conducted for a wide range of diluent size and other process variables such as liquid hourly space velocity and hydrogen/gas oil ratio. The results showed that the down flow mode of operation using 0.19 mm size of diluent could be used for generating reliable and meaningful data. On the other hand, the use of up flow mode of operation is restricted only for higher space velocities even while using 0.19 mm size of diluent. The results also indicated that the performance of the up flow mode of operation was poor at higher hydrogen/gas oil ratio. This change in performance is pronounced when higher size of diluent was used with the catalyst. In contrary, the hydrogen/gas oil ratio had minimum effect on the performance of the reactor for down flow mode of operation.

KINETICS OF HYDRODESULFURIZATION OF HEAVY GAS OIL DERIVED FROM OIL-SANDS BITUMEN

ABSTRACT With gradual shortage in the supply of crude oil, the importance of producing synthetic crude oil from oil sands and shale oil is increasing day by day. In the present paper, the effects of various process variables such as temperature, liquid hourly space velocity and hydrogen/heavy gas oil volumetric ratio on the removal of sulfur compounds from oil sands derived heavy gas oil has been studied. The experiments have been carried out in a micro scale trickle bed reactor over a commercial Ni–Mo catalyst. The temperature, liquid hourly space velocity and hydrogen/heavy gas oil volumetric ratio have been varied from 365 to 415°C, 0.5 to 1.9 h−1 and 400 to 1000 ml, respectively. Under optimum reaction conditions over 96% conversion of sulfur compounds was achieved. The kinetics of the rate of sulfur removal from the oil sands derived heavy gas oil has also been discussed in this article.

Hydrodynamic characteristics of cocurrent upflow and downflow of gas and liquid in a fixed bed reactor

The residence time distribution (RTD) of a bench-scale multiphase reactor has been investigated in the present study using air as a gaseous phase and water as a liquid phase. Two different sizes (1.1 and 0.3 mm) of silicon carbide were used as diluent for the catalyst bed. In the entire study, equal volumes of catalyst and diluent were used in the bed. The ranges of air and water velocities were kept at such levels as to simulate the liquid hourly space velocities and hydrogen/oil ratios of typical bench-scale hydroprocessing units. The experiments were conducted in both upflow and downflow modes of operation in the reactor. The two modes of operation showed wide differences in RTD when a larger size of diluent was used. However, the differences in RTD in both the modes of operation were eliminated by using a smaller size of diluent. The effect of gas and liquid velocities on different hydrodynamic parameters such as bed Peclet number of liquid, mean residence time of liquid and operating liquid holdup were also investigated for these two levels of diluent size.

Ethanol amination catalysis over early transition metal nitrides

Several high surface area early transition metal nitrides were evaluated for their ability to catalyze ethanol amination. These materials were very active with turnover frequencies comparable to those of supported Pt and Ni catalysts. Their activities ranked in the following order: VN>Mo2N>W2N>TiN>NbN. Like the Pt and Ni catalysts, the nitrides were very selective to the production of ethylamine. In addition, the nitrides demonstrated better selectivities to diethylamine and triethylamine at high conversion. The mechanistic pathways for ethanol amination over the nitride catalysts have been investigated. Ethanol appears to undergo reductive amination to produce ethylamine through an acetaldehyde intermediate. Ethene was produced as a byproduct via ethanol dehydration.

Production of hydrogen and medium btu gas via pyrolysis of a Kraft lignin in a fixed-bed reactor

Lignins are generally used as a low grade fuel in the pulp and paper industry. In this work, pyrolysis of a Kraft lignin obtained from Westvaco was carried out in a fixed-bed reactor to produce hydrogen and gas with medium heating value. The effects of carrier gas (helium) flow rate (13.4-33 ml/min/g lignin), heating rate (5-15/spl deg/C/min) and temperature (350-800/spl deg/C) on the lignin conversion, product yield and the product gas composition were studied.