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Reuse of spent hydrodesulphurization (HDS) of middle petroleum fractions catalyst CoMo/γAl2O3 was accomplished via removal of coke and contaminants such as vanadium, Iron, Nickel, and sulfur. Three processes were adopted; extraction, leaching, decoking. Soluble and insoluble coke was removed. Leaching step used three different solvents (oxalic acid, ammonium peroxydisulfate and oxalic acid + H2O2) in separate in order to remove contaminant metals (V, S, Ni and Fe).    The effect of soluble coke removal on leaching step was studied. It was found that the removal of soluble coke significantly enhances the leaching of contaminants and barely affected the removal of active metals (Co and Mo). It was found that the best route (sequence) was soluble coke extraction followed by contaminants leaching then decoking process and the best leaching solvent was oxalic acid. According to this determination, the removed contaminants were 79.9 % for sulfur, 13.69% for vanadium, 82.27 % for iron, and 76.34 % for nickel. The active components loss accompanied with this process were 5.08 % for cobalt and 6.88% for molybdenum. Leaching process conditions (leaching solvent concentration, temperature and leaching time) were studied to determine the best-operating conditions. The rejuvenated catalyst activity was examined by a pilot scale HDS unit of naphtha. Sulfur content removal of naphtha was found to be 85.56 % for single pass operation under typical operating conditions of refinery HDS unit of naphtha which are 1 ml/min feed flow rate, 200 H2/HC ratio, 32 bar operating pressure and 320 °C operating temperature.

The inhibitive power of Polyvinyl Alcohol (PVA) was investigated toward the corrosion of carbon steel in 0.2N H2SO4 solution in the temperature range of 30-60˚C and PVA concentration range of 150-2000 ppm.    The corrosion rate was measured using both the weight loss and the electrochemical techniques. The weight loss results showed that PVA could serve as a corrosion inhibitor but its inhibition power was found to be low for the corrosion of carbon steel in the acidic media. Electrochemical analysis of the corrosion process of carbon steel in an electrochemical corrosion cell was investigated using 3-Electrode corrosion cell. Polarization technique was used for carbon steel corrosion in 0.2N H2SO4 solutions in presence and absence of the inhibitor investigated. Electrochemical runs were done in the PVA concentrations of 150, 1000, and 2000 ppm and temperatures of 30, 40, 50, and 60˚C.    It was shown that the inhibition efficiency for PVA decreased with increasing temperature at a given PVA concentration. On the other hand it was shown that at given temperature the inhibition efficiency of PVA was increased with increasing of PVA concentration in the corrosive acid until a PVA concentration of 2000 ppm was reached.    The Maximum inhibition efficiency reached was about 71 % at 30ºC and 2000 ppm concentration, calculated by the weight loss technique.  It was indicated also that the corrosion of carbon steel in 0.2N H2SO4 is highly activation controlled and inhibition action is occurring at both anodic and cathodic sites on the metal surface.

The enhancements of heat transfer coefficient and Nusselt number in a heat exchanger system were achieved by using Titanium-dioxide (TiO 2 ) nanoparticles with an average diameter of 10 nm. TiO 2 nanoparticles/water has a better thermal conductivity compared to conventional working fluids (water). The heat transfer rate in a vertical shell and tube heat exchanger counter flow under laminar and turbulent flow conditions were investigated. The liquid flow rate has been varied in the range of 50-300 l/h while the inlet temperature was between 20 to 60 ºC. The effects of factors such as the Reynolds number and the peclet number on the heat transfer and flow characteristics were carried out and investigated. It was observed that the convection heat transfer increased remarkably with the increment of the temperature under various values of the Reynolds number. As well as, the Nusselt number increased about 17% as compared to pure water; at a nanofluid velocity of 0.0192 m/s at inlet temperature of 60 0 C.