مجله پژوهش نفت
پیاپی 58 (پاییز و زمستان 1387)

Soils contaminated with organic pollutants are nowadays one of the important environmental issues. Bioremediation is a simple, economic method for decontamination of such soils. In this work, biodegradability of hexadecane in slurry phase by an isolated bacterium is investigated in order to reduce the carbon content of a polluted clay soil. A model system was used including Kaolin clay soil of mesh size 100 and n-hexadecane (equivalent to diesel fuel) as the model soil and pollutant, respectively. Polluted soil containing hexadecane as the only carbon source for the bacterium has been incubated in slurry phase for 20 days in shaking cultures (200 rpm and temperature of 30 oC). Hexadecane decomposition at various hexadecane concentrations (10000 and 30000 ppm), soil to water ratios (0.2 and 0.33) amounts of inoculum (5 and 10 %) and initial pH (5.5 and 7) has been investigated. Hexadecane decomposition has been assessed based on measurement of total organic carbon (TOC). 10-70 % reduction in TOC was observed under various conditions indicating the high capability of this bacterium in biodegradability of hexadecane in slurry phase. Since the presence of biosurfactants in media containing organic compounds can increase the solubility of such compounds, surface tension was also measured as a criterion for the presence of biosurfactants. Surface tensions of 29-60 mN.m-1 were measured at various conditions confirming biosurfactant production by this bacterium.

The influence of preparation conditions of Cu/ZnO/Al2O3 catalysts by co-precipitation method on its performance in methanol synthesis from syngas was studied. By changing the preparation parameters at two levels, the optimized preparation conditions was determined and confirmed by reactor test of the catalyst prepared accordingly. The influence of the promoters Mn, Mg, Zr, Cr, Ba, Ce and W on catalyst activity and stability was also studied. Cerium exhibited the highest influence on catalyst stability. To investigate the effect of preparation procedure, catalyst samples were prepared by sequential precipitation method under similar conditions. It was found that catalyst prepared by sequential precipitation show higher catalytic activity. Optimized catalyst prepared by both method showed better performance compared to available commercial catalysts. Consequently, the developed formulations are capable of scale-up and commercial production processes.

Unique properties of ionic liquids such as low vapor pressure, high thermal stability, and their ability to dissolve polar compounds makes them potential alternatives for organic solvents lacking such characteristics. Studies show that substantial efforts are being made to synthesize these ionic liquids under milder reaction conditions. Quaternary imidazolium, pyridinum, and pyrrolidinium based salts are unfortunately prepared at high temperatures over long periods of time, making the syntheses economically inefficient. Parameters involved in the synthesis of each of these salts have been optimized in this work and the synthesis conditions have been compared. Results indicate that the synthesis of dialkyl imidazolium chlorides gives higher yields and requires shorter reaction times in comparison with the other two groups

The effect of the Ru and Re promoters on the physico-chemical properties, activity, selectivity of Fischer- Tropsch synthesis (FTS), deactivation and activity recovery of Co/Al2O3 catalysts are investigated. 1 wt% Ru and 1.4wt% Re increased the activity of the catalyst by a factor of 2.8 and 2.5 respectively. Both promoters enhance the selectivity of FTS is towards the higher molecular weight hydrocarbons. Promoted catalysts deactivated faster than unpromoted catalysts. High temperature H2 treatment (400 oC) restored the catalytic activity of the catalysts by about 98%.

Due to their high thermal effectiveness, good flow distribution and ease of sanitation, plate heat exchangers (PHEs) are widely used for continuous pasteurization of liquid food products. Since most food products in this research are non-Newtonian fluids, flow behavior in various chevron angles of non–Newtonian power law fluids is studied by means of 2D Computational Fluid Dynamics (CFD). For this purpose, aqueous solutions of carboxy-methyl-cellulose (CMC) at different weight concentrations, ranging from 0.5 % to 2% and 10≤Reg≤300 held at a constant temperature of 20oC were considered as operating conditions. To generate geometry and mesh, solve governing equations by finite volume method and analyze CFD results, software applications Gambit 2.0 and FLUENT 6.0.12 were used respectively. Analyses over the relationship between Reynolds number, fanning friction factor and rheological parameters of the fluid and chevron angles of the plates for different concentrations of CMC have been performed. Predictions of CFD calculations were compared to the experimental data, and these results showed a very good agreement.

Mesoporous nanocrystalline zirconia powders with high specific surface area and stable tetragonal crystallite phase were prepared by surfactant assisted precipitation method. The obtained results showed that the nanocrystalline zirconia powders have a good potentional as catalyst support in natural gas reforming with carbon dioxide. The activity results indicated that the nickel catalyst with 5 wt.% nickel loading showed stable activity for syngas production with a decrease of about 4% in methane conversion after 50 h of reaction. Addition of promoters (CeO2, La2O3, MgO and K2O) to the catalyst improved both the activity and stability of the nickel catalyst and increased the nickel dispersion and had a positive effect in preventing coke formation. The nickel catalyst (5% Ni–3% CeO2/ZrO2) showed high catalytic stability under severe reaction conditions for more than 1550 h on stream. Based on our knowledge, there is no prior documentation for a nickel catalyst that is comparable to this catalyst in catalyst stability under the reaction conditions employed in this study.

The invert-emulsion drilling fluids are commonly used to drill reactive formations because they inhibit water interaction with sensitive shales and dispersive formations. In an invert-emulsion drilling fluid solid additives should not be wet. In the absence of oil wetting agents, solid particles including weighting agents and shale are usually preferentially water-wet in mineral oils/brine emulsions saturated with calcium chloride or sodium chloride. Phospholipid and alkylimidazoline were used to make the solids oil-wet. Then the wettability of Barite and Calcite in invert-emulsion was studied along with evaluation of yield point and gel strength of drilling fluids. These oil- wetting agents caused Barite and Calcite to be moderately to strongly oil-wet resulting in lower yield point and gel strength for fluid. Alkylimidazoline is the comparatively more effective oil-wetting agent in different invert-emulsion drilling fluids.

Oxygenated additive (MTBE) widely used as octane enhancer of gasoline. Due to high water solubility of MTBE (50 gr/l), it can pollute ground waters as a result of production, storage, leakages of oxygenated gasoline from pipelines cracking, underground storage tanks in gas stations, transportation and distribution of MTBE. These items are major source of pollution of ground waters. MTBE concentration in a given well was considered 50 ppb. Treating this water with adsorption process on granular activated carbon filtrasorb (F-600) that has high-energy sites was studied by RSSCT and pilot plant methods and their results were compared. RSSCT system was designed to simulate pilot plant scale at EBCT=10 min. According to the results, breakthrough time calculated by RSSCT method was completely similar to operational value in pilot plant study.