Mamdouh S. Elmelawy

Characterization and Catalytic Activities of ZrO2-TiO2 Supported Hydrodesulfurization Catalysts

Abstract Pure ZrO2, TiO2, and ZiO2-TiO2 mixed oxides are prepared by urea hydrolysis. Hydrotreating catalysts containing 8 wt% (MoO3) and 3 wt% (NiO) are prepared using these oxides and characterized by the Brunauer, Emmett, and Teller (BET) surface area, pore volume, X-ray diffraction, Fourier transform infrared, differential thermal analysis, and scanning electron microscopy. Thiophene hydrodesulfurization, cyclohexene hydrogenation, and cumene hydrocracking are taken as model reactions for evaluating catalytic activities in a micro-catalytic reactor at 350°C and atmospheric pressure. Sulfided catalysts showed a wide range of activity variation as a function of support composition, which established that NiMo sulfided active phases strongly depend on the nature and composition of the support. It is found that catalytic activities increase with increasing zirconia content in mixed oxide and reach maximum values for 20% zirconia content. (20%) Zr/Ti mixed oxide supported catalyst was tested at high pressure with real gas oil feedstock. A thorough study of the relationship between operating conditions and product quality would contribute much to the optimization of hydrotreatment processes.

The Support Effect on Hydrogenolysis of Thiophene and Gas–Oil

Abstract Results are reported on the support effect on the catalytic activity in thiophene hydrodesulfurization (HDS) of sulfided Ni-Mo catalysts supported on pure niobia, mixed oxides of Nb2O5-TiO2 prepared by sol-gel method, and Nb2O5/TiO2 and Nb2O5/Al2O3 prepared by surface deposition. The prepared samples were characterized using N2 adsorption at −196°C, X-ray diffraction (XRD), and temperature-programmed reduction (TPR) techniques. This study showed activity variation as a function of support composition. The activity of niobia-rich catalysts was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. It was found that 5 wt% Nb2O5/TiO2-supported catalyst was the better catalyst for thiophene HDS. It was shown that by means of an adequate support design it is possible to significantly increase the functionalities of HDS catalysts. Semiconducting supports like TiO2 can improve the HDS activity by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. The 5 wt% Nb2O5/TiO2 was also tested at high pressure with gas oil feedstock. It is observed with the hydrogeolysis of sulfur compounds against time-on-stream that the activity of this catalyst decreases fast with time.

Can Mesoporous TiO2-Al2O3-Supported NiMoS OR CoMoS Effectively Perform in Ultra-Deep Desulfurization of Gas Oil?

Waste aluminum foil was used for preparation of mesoporous TiO2-Al2O3 using starch as a textural modifier. The catalytic species, Mo and Ni or Co were loaded onto the mesoporous support, following incipient wetness sequential impregnation. To gain an insight into the pore dimensions effect, Ni and Mo species with the same mass ratio were loaded onto the TiO2-Al2O3, prepared from analytical grade chemicals without templating. TPR spectra, TEM images and BET analysis showed how the promoter (Ni or Co), TiO2 and the template (starch) affect the ease of reduction of Mo species, the morphology of the active MoS2 phase and the pore dimensions of the catalysts. The catalysts were employed in hydro-desulfurization process of gas oil using a fixed bed down flow microreactor at varying operating conditions, viz., temperature (320–400°C), Liquid hourly space velocity (0.5–4 h–1), H2/oil ratio of 450 v/v, and 6 MPa operating pressure. The results showed that the promotion effect prevails over the textural effect, where Ni promoted catalyst (with lower surface parameters) exhibits higher activity than Co promoted one. The dual layer catalytic bed system achieved the sulfur level less than 10 ppm.

A study on optimization of acid sites concentration versus pore dimensions in modified solid acid catalysts for biodiesel production

ABSTRACT The acid sites concentration of silica sulfuric acid was optimized against pore dimensions depending on the intensity of silanol groups as a key for binding modifier molecules. The texturally modified rice husk silica, of determined intensity of silanol groups, was functionalized with different loadings of SO3H groups to produce solid acid catalysts with different concentrations of acid sites and different sizes of the pore systems. The catalysts were employed in trans-esterification of waste-cocking oil. The obtained optimum catalytic activity was attributed to the proper compensation between acid sites intensity and pore dimensions. The estimated TOF for methyl ester production was found to decrease with the increase of SO3H loading on the catalyst surface. The role of compatibility of the reactants phase with the catalyst nature could be validated by the observed much higher activity of sulfonated lignin in the studied esterification reaction than the modified RHS-acid catalysts under study.

Study of the Role of Lanthanum Containing Titania in Hydrogenolysis of Thiophene and Gas Oil

Abstract Pure La2O3 and La2O3-TiO2 mixed oxides are prepared by sol-gel method. Hydrodesulfurization catalysts containing 8 wt% MoO3 and 3 wt% NiO are prepared using these oxides and characterized by Brunauer, Emmett, and Teller (BET) surface area, pore volume, X-ray diffraction, differential thermal analysis, Fourier transform infrared and scanning electron microscopy. The effects of support composition have been investigated in order to determine their influence on hydrodesulfurization catalytic process. Hydrodesulfurization of thiophene model molecule reaction was carried out in a micro-catalytic reactor at 250°C–425°C and atmospheric pressure. Sulfided catalysts showed a wide range of activity variation as a function of support composition, which established that NiMo sulfided active phases strongly depend on the nature and composition of support. It is found that 10% La/Ti supported catalyst was the better catalyst for thiophene hydrodesulfurization. It was also tested at high pressure with a real feed Gas oil.