Salwa A. Ghoneim

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.

Titania modified activated carbon prepared from sugarcane bagasse: adsorption and photocatalytic degradation of methylene blue under visible light irradiation

ABSTRACT Activated carbon (AC), prepared from sugarcane bagasse waste through a low-temperature chemical carbonization treatment, was used as a support for nano-TiO2. TiO2 supported on AC (xTiO2–AC) catalysts (x = 10, 20, 50, and 70 wt.%) were prepared through a mechano-mixing method. The photocatalysts were characterized by Raman, X-ray diffraction analysis, FTIR, SBET, field emission scanning electron microscope, and optical technique. The adsorption and photo-activity of the prepared catalysts (xTiO2–AC) were evaluated using methylene blue (MB) dye. The photocatalytic degradation of MB was evaluated under UVC irradiation and visible light. The degradation percentage of the 100 ppm MB at neutral pH using 20TiO2–AC reaches 96 and 91 after 180 min under visible light and UV irradiation, respectively. In other words, these catalysts are more active under visible light than under UV light irradiation, opening the possibility of using solar light for this application.

Para-xylene Maximization—Part VI: Shape-Selective Platinum-Promoted Methylation of Toluene

Abstract The need for increased production of para-xylene, which is the primary material for producing the polyester fibers, activated this research. Although the alkylation reaction is acid catalyzed, we found that a Pt promoter activates this reaction by virtue of the presence of a vacant d-orbital in the Pt atom. In this work, a series of catalysts containing 0.1, 0.2, or 0.3% Pt in H-ZSM-5 zeolite was tested for alkylating toluene with methanol, aiming to produce the xylenes and maximizing para-xylene production in a temperature range of 300°C–500°C in the presence of hydrogen flow in a continuous-flow fixed-bed reactor. The catalysts were characterized by temperature programmed desorption (TPD) of ammonia for acid sites distribution analysis and platinum dispersion in the catalysts by hydrogen chemisorption. Moreover, the diffusion resistance extent in the current catalysts during the alkylation reaction has been evaluated via estimation of the Thiele modulus, Φ L . The selectivity for para-xylene production was found to increase systematically with increasing the Pt content in the catalysts, whereas the unloaded zeolite did not follow this order. The Φ L values calculated were accordingly found to increase also with increasing Pt content in the catalysts. Although para-xylene was the highest on the 0.3% Pt/H-ZSM-5 catalyst, the heavy undesired trimethylbenzenes were the lowest to be formed on this catalyst.

Response surface methodology for carbon dioxide reforming of natural gas

ABSTRACT The performance of 0.5% wt Rh/γ-AL2O3 catalyst for the dry reforming of natural gas using carbon dioxide has been studied. The response surface methodology (RSM) is used to study the effect of two different operating parameters, namely the hourly space velocity at the levels 18,000, 36,000, 45,000, and 60,000 ccg−1 h−1 and the reaction temperature at the levels 600, 700, and 800°C, on the conversion of the different components comprising commercial natural gas. The RSM is used to illustrate such effect in the three dimensions and shows the location of the optimum for the conversion or production of each component.

The Experimental and Numerical Approach of Catalytic Combustion on Noble Metals Disc Burners of the Turbulent Gaseous Fuel Jet Diffusion Flames

Abstract Catalytic combustion is proposed and developed as an efficient method of promoting stability and oxidation of gaseous fuel with minimum pollutants. The effect of catalytic combustion of gaseous turbulent diffusion flames over catalytic discs containing Pt, Pd, and (Pt + Pd) supported on γ-Al2O3 were experimentally and mathematically studied. These flames have proved to be highly stable over the three catalytic burners and their catalytic enhancement is found to be in the order (Pt + Pd) > Pt > Pd. The axi-symmetric thermal distribution of flames developing over these burners record higher values due to enhancing the fuel oxidizability on the noble metal sites in the reaction zone of flames via improving homogeneous-heterogeneous chemical reactions. Lower values of CO and NO are measured at the axial flames direction in the presence of catalytic burners. A numerical approach has been investigated for the catalytic combustion process on the three noble metals disc burners showing high numerical evaluation of different predicted functions. Stability limits are analyzed following a 1st-degree polynomial. The model of temperatures distribution is described by Gaussian function. For CO distribution, a non-linear four parameters model has been predicted. A differential equation for NO x indicates perfectly the location of the peak values. These models have been strictly confirmed with the experimental data.

Visible light sensitive activated carbon-metal oxide (TiO2, WO3, NiO, and SnO) nano-catalysts for photo-degradation of methylene blue: a comparative study

Abstract Four composites of metal oxide doped with activated carbon with a metal oxide weight of 20% were prepared using mechano-mixing method. The nano-catalysts were characterized by N2-adsorption–desorption, X-ray diffraction analysis, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV-diffuse reflectance, and photoluminescence spectroscopy. Photo-catalytic degradation of methylene blue dye under UV 254  nm and visible light was examined. In general, prepared catalysts are more active for degradation of dye under visible light than UV, reaching 96% within 180 min irradiation using the SnO catalyst. Photo-degradation of methylene blue followed pseudo first order reaction mechanism with a rate constant of 14.8 × 10−3 min−1, and the time required for removal of 50% of dye was 47 min.

Comparative assessment of response surface methodology quadratic models and artificial neural network method for dry reforming of natural gas

ABSTRACT The performance of 0.5% wt Rh/γ-AL2O3catalyst for the dry reforming of natural gas using carbon dioxide has been considered. In the present work a comparative study has been performed using Radial Basis Function Neural Network (RBFNN) and Response Surface Methodology (RSM) quadratic models to investigate their predictive ability for the effect of two different operating parameters, naSSSmely the hourly space velocity and the reaction temperature on the conversion of the different components comprising commercial natural gas. The predictive capabilities of the two methodologies were compared employing statistical error functions. The results indicated the superiority of RBF in the prediction capability; for example, the F-ratio for the CH4 reactant is 86 and 1088185 employing RSM and ANN methods, respectively. Also for the various components involved in the reaction system R2 ranges from 0.74 to 0.96 in case of RSM while it is 1.0 for all components employing ANN. This is due to ANN ability to approximate the non-linearity between the input and output variables.

Numerical Evaluation of CO Emissions for Catalytic Combustion over Noble Metal Disc Burners of Turbulent Gaseous Fuel Jet Diffusion Flames

Performance of a combustion system is often constrained by limits of pollutant emissions such as CO. Catalytic combustion over noble metals promotes efficient combustion with minimum pollutant formation. In this study, the volumetric percentage of carbon-monoxide distribution along the catalytic flames operating over noble metal disc burners Pt, Pd, and (Pt + Pd) supported on γ-Al2O3 discs are analyzed through non-linear exponential model function. The numerical prediction correlates the response variable (CO %) with two explanatory (independent) variables: the axial mean temperature and axial distances over each catalytic burner simultaneously. The fitting process indicates high adequacy matching with the experimental data. The response surface construction, with corresponding contour maps, has been established to visually analyze the proposed model equations and to fully identify the extent of the estimated relationship in the combustion domain. These constructions reveal clearly that the response variable (CO %) is mainly dependant on the axial mean temperature distribution and slightly on the axial distances along the catalytic flames and also indicate the effectiveness of the three noble disc burners in reducing CO emissions along the catalytic flames minimizing the environmental pollution.