G. J. T. Fernandes

Thermogravimetric kinetics of polyethelyne degredation over silicoaluminophosphate

Abstract In the current work, we investigated the Thermogravimetric kinetics of degradation of high-density polyethylene (HDPE) alone, and mixed with silicoaluminophosphate catalyst (SAPO-37/HDPE). To estimate the kinetic parameters of the polymer degradation, the Vyazovkin model-free kinetic method was applied. The activation energy ( E ) was calculated as a function of conversion ( α ) and temperature ( T ), providing an estimate of the time required for the degradation process at a given temperature. The products due to thermal and catalytic cracking of polyethylene were analyzed by gas chromatography/mass spectrometry (GC/MS). The SAPO-37 showed good catalytic activity, decreasing the activation energy for the process.

Thermal Analysis Applied to Solid Catalysts Acidity, Activity and Regeneration

The use of catalysts in numerous important processes is widespread throughout the chemical and petroleum-processing industries. Thermal analytical techniques can be used to evaluate important properties and processes associated with solid catalysts. This paper presents examples carried out in our laboratory of the general application of TG and DSC to the acidity, activity and regeneration of solid catalysts.

Catalytic degradation of polyethylene evaluated by TG

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.

Kinetic Parameters of Polymer Degradation by SAPO-37

High density poly(ethylene) has been submitted to thermal degradation alone, and in the presence of silicoaluminophosphate SAPO-37. The processes were carried out in a reactor connected on line to a gas chromatograph/mass spectrometer in order to analyze the evolved products. Polymer degradation was also evaluated by thermogravimetry, from room temperature until 800°C, under nitrogen dynamic atmosphere, with multiple heating rates. From TG curves, the activation energy related to degradation process was calculated using the Flynn and Wall multiple heating rate kinetic model for pure polymer (PE) and for polymer in the presence of catalyst (PE/S37). SAPO-37 showed good selectivity for low molecular mass hydrocarbons in PE catalytic degradation.

Catalytic degradation of high density polyethylene by HZSM-5 zeolite

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. From TG curves, the activation energies, calculated using an integral kinetic method, decreased 60.6% in the presence of the zeolite.

Catalytic distillation of an atmospheric petroleum resid using HZSM-5 and HY zeolites

ABSTRACT This work presents a study of the reactive distillation of atmospheric petroleum residue (ATR) containing 10% in mass of HY or HZSM-5 zeolites. The process aims the upgrade of ATR in order to obtain valuable products. The fundamental characteristic of the process is the immediate separation under thermal conditions and subsequent reaction of the products generated by the zeolite catalysts, favoring the displacement of the equilibrium towards the desired reactions. Such reactions occurred in the heterogeneous form, adding the HY or HZSM-5 zeolites to the ATR charge, and heating the mixtures at temperatures in the range of 50 to 500°C. The heating promotes intense heat exchange, solid-liquid reactions, obtaining the desired products. In the reactive distillation process, in presence of the acid sites of the zeolites, the short contact time of the hydrocarbons thermally cracked at low pressures favored secondary cracking reactions, increasing the selectivity to lower weigh molecular hydrocarbons, in the range of liquid gases, naphta, gasoline, jet fuel, diesel and lubricants. The obtained results proved that catalytic or reactive distillation is a promising technology for waste recovery that is surplus to the atmospheric and vacuum distillation processes for the refineries.

TG Study of the Kinetic Parameters of Regeneration of Coked HZSM-5 Zeolite

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.

Kinetic of Regeneration of Coked Alumina by Thermogravimetry

Thermogravimetry is used for regeneration of the alumina catalyst which was deactivated by coke, formed in the transformation of 1,3-butadiene in a fixed bed continuous flow reactor. The Vyazovkin model-free kinetic analysis has been applied to data on thermal oxidation of carbonaceous deposits on the catalyst. This analysis has allowed us to estimate the activation energy (E) as a function of α (conversion) and to predict the time required to remove coke at a given temperature.