Presence Of Low Molecular Compounds Research Articles

Effects of low molecular compounds in coal on the catalytic upgrading of gaseous tar

The main purpose of this study was to investigate the effects of low molecular compounds in coal on the formation of benzene, toluene, xylene and naphthalene (BTXN) in the catalytic upgrading of tar from coal pyrolysis by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Low molecular compounds were extracted from mineral-free lignite (Coal DA) and bituminous coal (Coal DB), and then the gaseous tars from the pyrolysis of residual coal (Coal DAR and Coal DBR), extraction solution (AE and BE) and mineral-free coal were subjected to catalytic cracking using USY zeolite as catalyst. The results show that the total amount of BTXN in the extraction solution and residual coal is 27% and 4.8% lower than that in Coal DA and Coal DB during catalytic upgrading of gaseous tars, respectively. The presence of low molecular compounds can result in a significant increase in the BTXN amount after catalytic reforming. The extraction solution in Coal DA are predominantly aliphatic compounds (72.7%) and Oxygen-containing aromatics (21.9%), whereas that in Coal DB is naphthalene series (33.1%), condensed aromatics (29.4%), and aliphatic compounds (23.5%). Phenols and condensed aromatics in low molecular compounds can be cracked into BTXN under the catalysis of USY zeolite. More heavy aromatics are cracked to light arene instead of polycondensation in the presence of aliphatic compounds.

Difference method of evaluation of dynamic integral thermogravimetric curves in decomposition of polypropylene

A new differential method of evaluating integral thermogravimetric records of the formation of volatile products during the degradation of polypropylene in air is presented. The method, applied to 0–100% conversion of the polymer to volatile products, may distinguish the initial presence of low molecular compounds in the polymer, as well as changes in the mechanism of degradation of the material.

Radiation-chemical changes in polystyrene and its methyl derivatives

The radiation-chemical processes taking place during photolysis and radiolysis of polystyrene, polyvinyl toluene and poly-α-methylstyrene at 77–373°K, without additives and in the presence of low-molecular compounds, at dosages in the range of 1–1000 Mrad, in the condensed state and in solution, have been studied by ESR-, IR- and UV-spectroscopy and by various physicochemical methods. It is shown that in PS intermolecular bonds are formed by γ-radiation as a result of recombination of phenyl radicals and addition radicals, and in polyvinyltoluene, by recombination of phenyl and benzyl radicals. The presence of CH 3 groups in the benzene ring increases the efficiency of radiation crosslinking and protects the main chain of the polymer from degradation. The substitution of a methyl group for hydrogen on the α-carbon atom of the PS main chain weakens the C αC β bond considerably and assists degradation of the polymer.