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The catalytic degradation of both low-and high-density polyethylene (LDPE and HDPE) and polypropylene (PP) has been investigated using MCM-41, a mesoporous aluminosilicate recently discovered, as catalyst. The results obtained have been compared to those of ZSM-5 zeolite and amorphous silica-alumina. For all the studied plastics, MCM-41 has been found more active than the amorphous SiO 2 -Al 2 O 3 , as a consequence of the higher surface area and the uniform mesoporosity present in the former. Compared to ZSM-5, MCM-41 exhibits a lower activity for the degradation of linear and low branched polymers (HDPE and LDPE, respectively), which can be related to the higher strength of the zeolite acid sites. However, the opposite is observed for the cracking of highly substituted plastics such as PP due to the severe steric hindrances these molecules encounter to enter into the narrow pores of the zeolite, as confirmed by molecular simulation measurements. Moreover, for the cracking of LDPE, HDPE, and PP, the selectivities toward hydrocarbons in the range of gasolines and middle distillates obtained over MCM-41 are clearly higher than those of ZSM-5. Therefore, MCM-41 is a catalyst potentially interesting for the conversion of polyolefinic plastic wastes into liquid fuels.

Kinetic studies on ozone decomposition in water were performed over a range of temperatures from 10 to 40 °C and pH rangp from 2.5 to 9. The ozone decomposition rate was determined in eq 24. This expression is supported by a reaction mechanism. The second term is negligible, at pH values below 3, leading to a first-order kinetic expression. The direct ozone-water reaction and the hydroxide ion initiation step are the main causes of ozone decomposition. Experimental and calculated ozone concentrations agree within ±10% for 95% of the experiments.

Experimental binary and ternary equilibrium data for the adsorption of hydrocarbon mixtures of methane, ethane, ethylene, and propylene on activated carbon at 20°C are presented and discussed. Reproduction of binary adsorption equilibria and prediction of ternary adsorption equilibria exclusively with data of binary systems have been carried out using a real adsorbed solution theory, which requires the calculation of the activity coefficients for the components in the adsorbed phase.Predicted equilibrium data are found to be in excellent agreement with experimental values using Wilson and UNIQUAC equations to calculate the activity coefficients. The real absorbed solution theory provides a much more accurate method for predicting multicomponent adsorption equilibria than the ideal adsorbed solution theory. SCOPEThe use of adsorption for the separation of gas mixtures has been continuously increasing. The main advantages of adsorption as compared with other separation techniques are the high selectivity that can be attained and the relatively high capacity of the adsorbents for volatile compounds, even at low partial pressures. Some applications of interest include the purification of methane, ethylene, and other light hydrocarbons; the covery of LPG from natural and refinery gas streams; the separation of olefins from cracked gases; and the recovery of acetylene and other pretrochemicals from dilute mixtures with other hydrocarbon gases.Although there are a great deal of publications on adsorption of mixtures of hydrocarbons on porous solids (Hill, 1949 On the other hand, most of the theoretical work based on the analogy between the thermodynamics of solutions and the thermodynamics of mixed adsorbates predicts adsorption equilibria using the assumption of an ideal behavior of the adsorbates on the solid surface, which can be expressed in terms of a Raoult's type law (Myers, 1965). However, predicted adsorption equilibria are not always found to be in good agreement with experimental data. Certainly, there is a competition of the adsorbed molecules for the active centers of the solid surface, due to the different adsorption capacity of the adsorbates, so that the ideal adsorbed solution theory can be improved modifying the Raoult's law by the introduction of the activity coefficients for the components in the adsorbed phase. This paper discusses new experimental data on adsorption for binary and ternary hydrocarbon mixtures on activated carbon at 20°C and a total pressure up to 760 mm Hg (101.33 K Pa). A thermodynamic method based on a real adsorbed solution theory is applied to reproduce experimental binary adsorption equilibria and to predict ternary adsorption equilibria, only with binary systems data, calculating the activity coefficients for the components in the adsorbed phase by means of Wilson and UNIQUAC equations for vapor-liquid equilibrium. CONCLUSIONS AND SIGNIFICANCEAn experimental technique based on a fluidized adsorbent bed can be used to determine adsorption equilibria of gaseous mixtures in por...

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Multiwalled carbon nanotubes (CNTs) were functionalized with HNO 3 , HNO 3 /H 2 SO 4 , and HNO 3 /Na 2 CO 3 . The preparation of metal supported on mesoporous carbon nanotube catalyst is described. The catalysts were synthesized by impregnation of carbon nanotubes with different metallic precursors (H 2 PtCl 6 ‚6H 2 O, RuCl 3 ‚ H 2 O, and CuCl 2 ‚2H 2 O) followed by reduction. The structures of the CNT modified with HNO 3 , HNO 3 /H 2 -SO 4 , and HNO 3 /Na 2 CO 3 and CNT-supported metal catalysts have been characterized by means of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and nitrogen adsorption/desorption isotherms (BET), and their activity was tested in continuous catalytic wet air oxidation of aniline. For the catalysts prepared with metal precursors, activities were found in the order of Pt/N-CNT > Cu/N-CNT > Ru/N-CNT. The structure of carbon nanotubes supported metal catalyst is responsible for the activity, and the absence of micropores enhances the potential capabilities of carbon nanotubes as support material.

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