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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. [ABSTRACT FROM PUBLISHER]

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, ΦL. 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 ΦL 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. [ABSTRACT FROM AUTHOR]