Influence Of Pyrolysis Research Articles

Effect of heat treatment on the character of coke deposited on HZSM-5 and HY zeolites in acetone conversion

HZSM-5 and HY zeolites were coked at 350 °C during acetone conversion under on-stream conditions at atmospheric pressure, in some cases also in a static arrangement at lower pressures. The character of the carbonaceous residues deposited on both zeolites under the above conditions and the influence of pyrolysis as well as of partial oxidation were examined using infrared and 13C cross-polarization magic angle spinning nuclear magnetic resonance spectroscopies together with the mass spectrometric detection of the volatile products. The coke on HY zeolites was found to be composed of more condensed aromatics and branched aliphatic chains than that on HZSM-5. The pyrolysis removed the aliphatic chains, and on HZSM-5, the less condensed aromatic rings. Both these coke components were also preferentially oxidized. The partial oxidation led to a substantial increase in the void volumes compared with the parent coked zeolites. Oxidized intermediates were observed on the zeolite surfaces.

The influence of pyrolysis and matrix modifiers for analysis of glass materials by GFAAS using slurry sample introduction

The influence of pyrolysis and different matrix modifiers on the atomization of Cu, Co, Cr, Mn, Fe and Ni in slurries of glass samples using graphite furnace atomic absorption spectrometry has been investigated. Pyrolysis and matrix modification do not influence the analytical performance and therefore they can be omitted. Results obtained by scanning electron microscopy indicate that the use of a pyrolysis step causes the size of the original particles to increase. The sample particles then behave as a matrix modifier themselves, so that a significant delay in appearance time is observed in the absorption signals for most elements and materials studied. Analytical results of the analysis of several NIST siliceous standard reference materials, obtained without using a matrix modifier or a pyrolysis step, are presented and compared to the results obtained by the conventional acid digestion procedure.

Pulverized coal conversion in downflow gasifier

AbstractThe behaviour of coal particles undergoing pyrolysis in a downflow reactor is modelled in two dimensions using integral approximation. The governing equations are solved numerically by marching procedures using Adams–Moulton and Romberg integration methods. The conversion of coal particles is studied in terms of chemical kinetics, hydrodynamic flow of volatiles and the heat transfer mechanism at the interface. The conversion increases with decreasing velocity, solid loading, particle diameter and total pressure. Owing to large amounts of gas production, the influence of pyrolysis on the gas‐particle heat transfer and drag coefficients becomes important at large particle diameters. For particle diameters less than 100 μm, such influence is minimal.

Pyrolysis studies on polyacrylonitrile fibres: Physical property/chemical structure changes during the initial stages of pyrolysis

Abstract Polyacrylonitrile was prepared and wet spun into fibres. The influence of pyrolysis at 220° in oxygen and nitrogen on the tensile properties of the fibres, both drawn and undrawn, has been examined. Tensile strength, yield stress and initial modulus go through a maximum after about 60 min pyrolysis in oxygen and 120 min in nitrogen. Thermogravimetric analysis and differential scanning calorimetry was carried out, the latter indicating also that, in nitrogen, chemical changes were delayed compared with the reactions in oxygen. Infra red analyses support these findings, the ratio of absorbence at 6.3 μ to absorbence at 3.12 μ going through a maximum at a time of pyrolysis, dependent on whether or not oxygen was present. It is proposed that the results can be explained on the basis of two competitive reactions—cyclisation and degradation.