Applied Petrochemical Research (v.1, #1-4)
Research for industry by Arno de Klerk; Soliman Al-Khowaiter (1-2).
Desulfurization of heavy oil by Rashad Javadli; Arno de Klerk (3-19).
Strategies for heavy oil desulfurization were evaluated by reviewing desulfurization literature and critically assessing the viability of the various methods for heavy oil. The desulfurization methods including variations thereon that are discussed include hydrodesulfurization, extractive desulfurization, oxidative desulfurization, biodesulfurization and desulfurization through alkylation, chlorinolysis, and by using supercritical water. Few of these methods are viable and/or efficient for the desulfurization of heavy oil. This is mainly due to the properties of the heavy oil, such as high sulfur content, high viscosity, high boiling point, and refractory nature of the sulfur compounds. The approach with the best chance of leading to a breakthrough in desulfurization of heavy oil is autoxidation followed by thermal decomposition of the oxidized heavy oil. There is also scope for synergistically employing autoxidation in combination with biodesulfurization and hydrodesulfurization.
Keywords: Desulfurization; Heavy oil; Bitumen; Hydrodesulfurization (HDS); Oxidative desulfurization (ODS); Biodesulfurization (BDS); Autoxidation
Direct production of dimethyl ether from synthesis gas utilizing bifunctional catalysts by Nahid Khandan; Mohammad Kazemeini; Mahmoud Aghaziarati (21-27).
In this study, direct synthesis of dimethyl ether from synthesis gas was investigated. For this purpose, H-mordenite zeolite was modified by wet impregnation of aluminum oxide onto it. The prepared catalysts were characterized by AAS, XRD and NH3-TPD analyses. Results of catalytic tests indicated that H-mordenite modified with 8 wt% aluminum oxide was an appropriate catalyst for synthesis of dimethyl ether (DME) from methanol in which methanol conversion and DME selectivity were 99.8 and 96.8%, respectively, without a noticeable change in catalyst stability. A series of bifunctional catalysts, Cu–ZnO–ZrO2/Al-modified H-mordenite, were prepared by co-precipitating sedimentation method and characterized. Synthesis of DME via direct CO hydrogenation was then evaluated in a three-phase slurry reactor. Experimental results showed that Cu–ZnO–ZrO2/Al-modified H-mordenite was a suitable catalyst for the production of dimethyl ether from synthesis gas. Ultimately, the effects of operating conditions such as temperature, pressure and feed flow rate on the process performance of the determined optimum bifunctional catalyst have been reported.
Keywords: Dimethyl ether; Synthesis gas; Bifunctional catalyst; Cu–ZnO–ZrO2/Al-modified H-mordenite
Preparation and evaluation of demulsifiers agents for Basra crude oil by Hikmeat Abd Al-Raheem Ali (29-33).
The present study relates to the preparation of demulsifiers from caster oil for dehydration (desalting) of Basra crude oil and water emulsions. It is an empirical application study. Two emulsifiers were compared, RP/6000, which is commercially available and ammonium castor oil sulfonate that was prepared. The general physical properties and IR spectra were measured for the demulsifiers. The demulsification studies were performed at 50 °C, using a water–oil emulsion containing 15 vol% water and 3 wt% NaCl in the water. Parameters that were studied include demulsification time, demulsifier dose and the effect of pH. The best water separation was obtained at highest pH and demulsifier dose.
Keywords: Demulsifiers; Basra crude oil
n-Alkane hydroconversion over carbided molybdena supported on sulfated zirconia by A. Galadima; R. P. K. Wells; J. A. Anderson (35-43).
A carbided molybdena on sulfated zirconia support has been prepared by in situ exposure to a methane/hydrogen mixture at 650 °C and the characteristics established using N2 adsorption and X-ray diffraction. The activity of the catalyst in the hydroconversion of C6 to C9n-alkanes was investigated in the temperature range 350–450 °C at 1 atm pressure. Activity and selectivity were found to show strong dependence on the choice of n-alkane with reaction rates found to be higher for the shorter alkanes. n-Hexane and n-heptane were hydroisomerised to the corresponding C6 and C7 isomers with high selectivity while the higher alkanes, especially nonane, produced mainly hydrocracking products. The catalyst offers a potential system for the upgrading of light naphtha range paraffins.
Keywords: n-Alkanes; Chain length; Hydroisomerisation; Hydrocrackingβ-Mo2C/SO42−–ZrO2
3-D finite element analysis of roller-expanded heat exchanger tubes in over-enlarged tubesheet holes by N. Merah; A. Al-Aboodi; A. N. Shuaib; Y. Al-Nassar (45-52).
Repeated de-stubbing and re-tubing of heat exchangers in petrochemical plants during their useful lifetime may result in over-enlarged tubesheet holes with overtolerances that exceed those prescribed by Tubular Exchanger Manufacturing Association (TEMA) standards (1988). Roller expansion of tubes in these over-enlarged holes may result in tube thinning and weakening of the joint due to a decrease of interfacial pressure between the tube and tubesheet. In the present work, a 3-D finite element (FE) model of a tube-tubesheet joint was used to determine displacement and stress distributions along the axial direction of roller expanded tube-tubesheet joint and to evaluate the combined effects of large initial clearance and strain hardening of tube material on interfacial pressure and tube deformation. The results obtained from the present model are compared to those of axisymmetric FE analysis and to the experimental results. Both axisymmetric and 3-D models are found to yield comparable trends showing that for elastic perfectly plastic tube material the residual contact pressure remains constant well above the prescribed TEMA maximum overtolerance values. In addition, both models show that for strain hardening tube materials the interfacial pressure increases with increasing clearance. An appreciable difference is observed at high overtolerances where the 3-D model predicts cut-off clearances (clearance at which the interfacial pressure starts to drastically drop) which are about 30% lower than those predicted by the axisymmetric models. The tube inner surface deformation and pull out forces estimated from 3-D results compares very well with those obtained from the experimental tests.
Keywords: 3-D Finite element; Tube-tubesheet joint rolling; Clearance effects; Strain hardening; Overtolerances