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Abstract  

A thermogravimetric method is proposed for study of the kinetic parameters of coked HZSM-5 zeolite regeneration. The technique, which makes use of integral thermogravimetric curves, was optimized by microprocessed integrated mathematical methods. The kinetic parameters obtained from the TG curves are the activation energy, the rate constants, the half-life times, and in particular the coke removal time as a function of temperature. The activation energy calculated by using the Flynn and Wall kinetic method was 81.4 kJ mol−1. It was observed that, to remove 99% of the coke from the zeolite in a period of 1 h, it would be necessary to carry out thermo-oxidation at 748 K, with a dry air purge flow of 120 cm3 min−1.

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transformed into its acidic type via NH 4 NO 3 solution ion-exchange. Four series of modified nano-sized HZSM-5 zeolites were prepared by subjecting the zeolite to steaming, steaming–HNO 3 leaching, HNO 3 leaching–steaming, and HNO 3 leaching

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Abstract  

Temperature-programmed desorption (TPD) of water was applied to characterize short-time dealuminated HZSM-5 zeolites. Using a regularization method, distribution functions of the effective desorption energy of water were calculated. The results clearly show that during dealumination a new adsorption site is formed which can be attributed to non-framework or transient aluminium species. The highest concentration of these sites was observed for a dealumination time of 25-30 min. NO adsorption studies support this result. Furthermore, it could be concluded that the heterogeneity and the average acid strength of the remaining Si-OH-Al groups of the dealuminated samples do not change compared to the Si-OH-Al groups of the parent HZSM-5 zeolite.

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The temperature-programmed desorption (tpd) of the amount of ammonia which is preadsorbed at about 373 K at HZSM-5 zeolites yields a complex desorption curve consisting of two overlapped peaks (Β andγ peak). Parts of the ammonia desorbed can be attributed to SiOHAl groups considering also1H-MAS NMR measurements.

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Abstract  

High-density polyethylene (HDPE) was cracked over HZSM-5 and HY zeolites and the reaction was followed using simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC) and was compared with the degradation of the same material in the absence of an added catalyst. The products obtained in the degradation reaction were analyzed by gas chromatography. The simultaneous use of the signals from the TG and DSC allowed an accurate description of the thermal and catalytic degradation of the polymer by application of a novel kinetic model that correlates the two signals that are measured. The kinetic parameters were estimated by fitting this model to the experimental data obtained by TG and DSC. For both zeolites, the polymer degradation takes place at lower temperatures when compared with pure thermal degradation. It was also observed that the two zeolites have a distinct influence on the product distribution.

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Abstract

The effect of regeneration conditions on the composition of the gases evolved during the catalytic pyrolysis of low density (LDPE) and high density polyethylene (HDPE) with HUSY and HZSM5 catalysts has been analysed by the TG/FTIR technique. When regenerated HUSY was employed, the evolution of the gases obtained was similar to that with fresh HUSY, indicating that the regeneration treatment did not affect its properties. Nevertheless with HZSM5, as the regeneration temperature was higher, the composition of the gases gradually became more similar to that evolved in the thermal process.

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. Experimental Preparation and characterization of the solid catalysts The protonic HZSM-5 zeolite used in this work was synthesized at different Si/Al (25, 40 and 118) ratios according to a procedure described in detail elsewhere [ 17

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Abstract  

HZSM-5 zeolite was screened as catalyst for high density polyethylene degradation at 450‡C, under nitrogen static atmosphere. Two different samples were studied in this condition: HDPE alone and mixed with HZSM-5. The reactor was connected on line to an HP 5890-II gas Chromatograph. Sample degradation was investigated using a Perkin-Elmer Delta 7 Thermobalance, from room temperature to 800‡C, with heating rates of 5.0, 10.0 and 20.0‡C min−1. From TG curves, the activation energies, calculated using an integral kinetic method, decreased 60.6% in the presence of the zeolite.

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naphthalene in the absence of oxygen over several transition metals supported on HZSM-5 zeolite. This reaction, which is also called methane dehydroaromatization (MDA), has been widely tested on many transition metals supported on HZSM-5 such as Mo, W, Fe, V

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detector (SP6800A, 2 m stainless steel column packed with Propark Q support). For comparison, the catalysts for cation exchange resin Amberlyst-15 (Rohm and Haas shanghai chemical industry Co., Ltd.) and HZSM-5 zeolite (SiO 2 /Al 2 O 3 = 25, Nankai

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