Ahmed K. Aboul-Gheit

Effect of decationation and dealumination of zeolite Y on its acidity as assessed by ammonia desorption measured by differential scanning calorimetry (DSC)

Abstract Zeolite NaY was decationated step-wise until the H-form was obtained (HY), and zeolite HY was dealuminated step-wise to increase its SiO2/Al2o3 ratio from 4.8 to 8.5. Ammonia was adsorbed on all the zeolite forms and was then desorbed thermally in a DSC cell, making use of the programmed temperature-increasing facility available in the DSC system. The total acidity of the zeolite was found to increase with decationation and decrease with dealumination. Strong acidity was found to increase with both decationation and dealumination, whereas weaker acidity decreased. The strength of strong acid sites increased further, whereas that of weaker acid sites decreased in both treatments.

Sol-Gel and Thermally Evaporated Nanostructured Thin ZnO Films for Photocatalytic Degradation of Trichlorophenol

In the present work, thermal evaporation and sol–gel coating techniques were applied to fabricate nanostructured thin ZnO films. The phase structure and surface morphology of the obtained films were investigated by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The topography and 2D profile of the thin ZnO films prepared by both techniques were studied by optical profiler. The results revealed that the thermally evaporated thin film has a comparatively smoother surface of hexagonal wurtzite structure with grain size 12 nm and 51 m2/g. On the other hand, sol–gel films exhibited rough surface with a strong preferred orientation of 25 nm grain size and 27 m2/g surface area. Following deposition process, the obtained films were applied for the photodegradation of 2,4,6-trichlorophenol (TCP) in water in presence of UV irradiation. The concentrations of TCP and its intermediates produced in the solution during the photodegradation were determined by high performance liquid chromatography (HPLC) at defined irradiation times. Complete decay of TCP and its intermediates was observed after 60 min when the thermal evaporated photocatalyst was applied. However, by operating sol–gel catalyst, the concentration of intermediates initially increased and then remained constant with irradiation time. Although the degradation of TCP followed first-order kinetic for both catalysts, higher photocatalytic activity was exhibited by the thermally evaporated ZnO thin film in comparison with sol–gel one.

Effect of combining the metals of group VI supported on H-ZSM-5 zeolite as catalysts for non-oxidative conversion of natural gas to petrochemicals

The most prestigious catalyst applied in natural gas (methane) non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5 was correlated with 3%Cr+3%Mo/H-ZSM-5 and 3%W+3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion. The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700 °C and a GHSV of 1500 ml·g.−1·h−1 Characterization of the catalysts using XRD, TGA and TPD were investigated. XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.

Catalytic para-xylene maximization II – alkylation of toluene with methanol on platinum loaded H-ZSM-5 zeolite catalysts prepared via different routes

Abstract Two series of catalysts, A and B, each containing 0.2%, 0.4%, and 0.6% Pt on H-ZSM-5 zeolite, were prepared via two different procedures; catalysts of series A were prepared via impregnating H-ZSM-5 with the Pt precursor (H 2 PtCl 6 ) solution, whereas those of series B were prepared via impregnating NH 4 -ZSM-5 zeolite with the Pt precursor solution followed by deammoniation to the Pt/H-ZSM-5 forms. The prepared catalysts were examined for toluene alkylation with methanol in a flow reactor under atmospheric conditions using H 2 gas carrier. The catalysts were characterized for acidity magnitude and strength via temperature programmed desorption of ammonia (TPD) and for Pt dispersion in the zeolite via H 2 chemisorption. Correlation of the catalysts characteristics with their reactivities for toluene conversion, xylenes production, trimethylbenzenes formation and xylene isomers in product relative to their thermodynamic equilibrium values were carried out.

Characterization of oils by differential scanning calorimetry

Abstract Lubricating and fuel oils can be characterized for their low-temperature specifications with better repeatability and reproducibility than the standard pour point and cloud point methods. These low-temperature tests are non-destructive and can be followed by using the same sample for measuring the high-temperature thermal stability of the oil (DSC destructive test). The oil sample can be as small as 10 mg. The presence of pour point depressant additives separated the wax crystallization DSC effect (exotherm) from the wax melting effect (endotherm), and also produced heat-flow effect in the higher temperature region.

Hydroconversion and diffusion of n-heptane on mordenite catalysts

Abstract Hydroconversion of n-heptane was carried out in a high-pressure continuous plug-flow reactor system using catalysts containing hydrogen mordenite (HM): Pt HM , Re HM , PtRe HM and PtTh HM . Pt HM was found most selective for n-heptane isomerization, whereas PtRe HM and PtTh HM possessed comparable intrinsic isomerization activities and excellent centric hydrocracking selectivities. PtTh HM gave the highest iC 4 nC 4 ratio. The Thiele modulus and effectiveness factor were calculated as diffusion parameters over the temperature range studied (250°–400°C) for all catalysts. A correlation of these parameters with catalytic behaviour shed some light on the migration of metals during catalyst preparation. Platinum appears to migrate away from the pore mouth to the pore interior via promotion with either rhenium or thorium.

Effect of hydrothermal treatment and ammonium ion incorporation in platinum-mordenite catalysis for n-hexane hydroconversion

Abstract Hydroconversion of n-hexane was studied on catalysts containing 0.25% Pt supported on H-mordenite (H-M) and NH4-M. The H-M containing catalysts were Pt/H-M, Pt on steamed H-M (Pt/St H-M) and steamed Pt/H-M (StPt/H-M), whereas the NH4-M containing catalysts were Pt/NH4-M and StPt/NH4-M. Steam-treatment of H-M containing catalysts enhanced the hydroconversion activity, whereas such treatment decreased the activity of the Pt/NH4-M catalyst. The diffusion resistance parameter, i.e., the Thiele modulus, ΦL, estimated for the reaction on the catalysts under study was found to increase with the increase in the catalytic activity, and both were found to decrease in the order: Pt/NH 4 -M>StPt/NH 4 -M>StPt/H-M>Pt/StH-M>Pt/H-M . Pt dispersion in the zeolite was not comparable with the catalytic activities of the H-M containing catalysts. The higher activity of the Pt/NH4-M catalyst could be attributed to a higher Pt dispersion in the zeolitic channels, higher strength of the acid sites (determined by temperature programmed desorption (TPD) of ammonia) and higher diffusion limitation of the reactant in the catalyst pores.

Para-Xylene Maximization. Part VIII: Promotion of H-ZSM-5 Zeolite by Pt and HF Doping for Use as Catalysts in Toluene Alkylation with Methanol

Toluene was alkylated with methanol in a flow type reactor at temperatures between 300 and 500℃ using H-ZSM-5 zeolite, 0.2%Pt/H-ZSM-5 and hydrofluorinated 0.2%Pt/H-ZSM-5 with HF concentrations of 1.0%, 2.0%, 3.0%, or 4.0%. Pt primarily enhances toluene conversion, total xylenes production, and p-xylene relative to its thermodynamic equilibrium. As the concentration of HF increases from 1.0% to 3.0%, the catalyst activity increases because of the increase in the number of acid sites and their strength. Additionally, the surface area and Pt dispersion also increases. An advantage of increased HF doping is that the formation of voluminous trimethylbenzene (TMB) byproducts is inhibited. However, at a HF concentration of 4.0%, Al and Si are partially leached and then deposited mostly in the wider catalytic pores. This was determined by evaluating the pore volume distribution and we determined that reactivity inhibition was obviously present and was due to diffusion restriction.

Catalytic Decomposition of Natural Gas to CO/CO2-Free Hydrogen Production and Carbon Nanomaterials Using MgO-Supported Monometallic Iron Family Catalysts

Monometallic Fe, Co, and Ni/MgO catalysts with 50 wt.% metal loadings were prepared and examined for natural gas decomposition to nanocarbonaceous materials, particularly multiwalled carbon nanotubes (MWCNTs) and co-valuable hydrogen. The catalytic testing was carried out in a fixed-bed horizontal reactor at 700°C under atmospheric pressure. The fresh and/or used catalysts were characterized using XRD, TPR, HRTEM, SEM, TG/DTA, Raman spectroscopy, and BET surface measurements. The resulting data showed that the 50%Co/MgO catalyst displayed higher catalytic decomposition activity of natural gas to COx-free hydrogen production (∼88%), higher yield of MWCNTs, and excellent stability up to 10 h time-on-stream. On the other hand, the Ni-containing catalyst showed lower catalytic activity toward hydrogen and CNTs production, principally due to the formation of rock-salt MgxNi(1-x)O solid solution as observed from XRD and TPR data. Accordingly, the concentration of Ni particles required for natural gas feed was extremely low. The d orbital of Ni was presumed to be occupied during the formation of the solid solution, which inhibits the solublization or adsorption of hydrocarbons on Ni particles. The MWCNTs obtained over Ni-based catalyst had narrow and homogeneous diameters (∼11–13 nm). However, the Fe/MgO catalyst exhibited intermediate activity between those of Ni and Co˭MgO catalysts toward hydrogen production (∼44%). This catalyst produced mixtures of carbon nanofibers and nanotubes.

Impregnation design for preparing bimetallic catalysts

Abstract The data show how two metal precursors, possessing equal rates of adsorptionon a λ-alumina support, be homogeously dispersed through adding a proper additive (HCl) for preparing bimetallic catalysts, whereas two metal precursors, possessing different adsorption rates, could not be homogeneously dispersed or distributed in the support while using this additive. Chloroplatinic and chloroiridic acids are examples of the first type whereby PtIr-containing catalysts are prepared. Chloroplatinic acid and ammonium paratungstate are examples of the second type whereby PtW-containing catalysts are prepared. For preparing PtIr-containing catalysts a single impregnation of the two precursors from one solution is thus possible, whereas for preparing PtW-containing catalysts, two impregnations from two separate precursor solutions are to be carried out.