Solid-phase pyrolysis

Characterization of aromatic hydrocarbons from the gas-phase and solid-phase pyrolysis of tobacco 55th Tobacco Science Research Conference, Program Booklet and Abstracts, Vol. 55, Paper No. 21, 2001, pp. 32-33. 

Fig. 2. Overall schematic of solid fuel combustion (1). Reaction sequence is A, heating and drying B, solid particle pyrolysis C, oxidation and D, post-combustion. In the oxidation sequence, left and center comprise the gas-phase region, tight is the gas—solids region. Noncondensible volatiles include CO, CO2, CH4, NH, H2O condensible volatiles are C-6—C-20 compounds oxidation products are CO2, H2O, O2, N2, NO, gaseous organic compounds are CO, hydrocarbons, and polyaromatic hydrocarbons (PAHs) and particulates are inerts, condensation products, and solid carbon products.

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

The total emission In the commercial heat treatment of 5 to 8 hours at 170 to 160°C varied from 0.4 to 1.2% for CO2 and 0.05 to 0.2% for CO and 0.04 to 0.1% for total acids based on dry board. Some of this emission might emanate from pyrolysis of higher molecular weight material condensed and deposited on the walls of the heat treatment chamber. The heat of formation of this CO2 and CO Is about half the total heat release measured. Part of the oxidation products might remain in the solid phase within the board material, e.g. as bound carbonyl and carboxylic groups, partly followed by heat consuming dehydration reaction. 

Investigators have used the words carbon and soot to describe a wide variety of carbonaceous solid materials, many of which contain appreciable amounts of hydrogen as well as other elements and compounds that may have been present in the original hydrocarbon fuel. The properties of the solids change markedly with the conditions of formation and, indeed, several quite well-defined varieties of solid carbon may be distinguished. One of the most obvious and important differences depends on how the carbon is formed carbon may be formed by a homogeneous vapor-phase reaction it may be deposited on a solid surface that is present in or near the reaction zone or it may be generated by a liquid-phase pyrolysis. 

Mok and Antal [70,71] proposed a reaction tree, see Figure 51, consisting of both concurrent and consecutive pathways to describe the pyrolysis of polysaccharides taking place in the particle phase (Figure 42). The relative importance of each pathway is influenced by the intraparticle solid phase temperature, the presence of additives, pressures, etc [61]. 

Calculation of the rate of decomposition in the solid phase shows that it is significant only when Te/f approaches Ts. Thus, Teff Ts, and the apparent activation energy during linear pyrolysis is half of that measured in bulk degradation experiments. This conclusion can also be inferred from the relations given in Ref. 35.]... 

The pyrolysis products of expls in tandem with GC/MS served as indirect identification of contaminant expls in the environment. The pyrolysis products generated, which are indicative of the parent molecule, are separated by GC and identified by MS (Ref 108). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-DNT, 3- and 5-sulfonic acids (Ref 124). The enhanced detection of TNT vapors was achieved by pre-concn on a metal surface, and flash-desorbed onto a chromatograph interfaced with a quadrupole MS (Ref 76). Vapors of TNT, acetone, toluene, cyclohexanone, and an organosilicon were detected and identified by GC/MS (Ref 78). Various reports were surveyed to determine which methods, including GC/MS, aire potential candidates for the detection of traces of TNT emitted from military land-mines (Ref 80) The vapors collected from Comp B were analyzed by GC/MS besides the TNT and RDX, H20, N20, C02, plus several unidentified compds, were detected (Ref 79). By the use of GC, isomeric impurities in the vapor, as well as solid phase of TNT, were resolved and identified by MS (Refs 61,62 115)... 

Short-lived organic radicals, electron spin resonance studies of, 5, 53 Small-ring hydrocarbons, gas-phase pyrolysis of, 4, 147 Solid state, tautomerism in the, 32, 129 Solid-state chemistry, topochemical phenomena in, 15, 63 Solids, organic, electrical conduction in, 16, 159 Solutions, reactions in, entropies of activation and mechanisms, 1, 1 Solvation and protonation in strong aqueous acids, 13, 83 Solvent effects, reaction coordinates, and reorganization energies on nucleophilic substitution reactions in aqueous solution, 38, 161 Solvent, protic and dipolar aprotic, rates of bimolecular substitution-reactions in,... 

Empirical approaches are useful when macroscale HRR measurements are available but little or no information is available regarding the thermophysical properties, kinetic parameters, and heats of reaction that would be necessary to apply a more comprehensive pyrolysis model. Although these modeling approaches are crude in comparison with some of the more refined solid-phase treatments, one advantage is that all required input parameters can be obtained from widely used bench-scale fire tests using well-established data reduction techniques. As greater levels of complexity are added, establishing the required input parameters (or material properties ) for different materials becomes an onerous task. 

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