Pyrolysis inhibition

Bhupendra K. Mazumdar I do not see how a significant amount of useful products could be obtainable by degradation in the presence of chlorine. We have found that treatment by chlorine before or during pyrolysis inhibits tar formation completely. Consequently, 93-94% of the carbon in the coal is fixed in the char. Thus, only a relatively small proportion of carbon could be devolatilized, leading to the formation of small amounts of interesting products."... 

Phosphite additives to preliminarily degraded PSF and further heat treatment do not make the polymer eolor lighter and, according to IR spectra, have no effect on intensity of absorption bands associated with oxidized structures, for example, carbonyl groups. To put it differently, phosphorylation, noticeable, as the heat stabilization mechanism in other systems, for example, at PET and PMMA combustion and pyrolysis inhibition [76] or thermal oxidation of synthetic rubbers and vinylchloride polymers [63], is not observed during inhibited high-temperature PSF degradation. 

Cellulose pyrolysis kinetics, as measured by isothermal TGA mass loss, were statistically best fit using 1st- or 2nd-order for the untreated (control) samples and 2nd-order for the cellulose samples treated with three additives. Activation parameters obtained from the TGA data of the untreated samples suggest that the reaction mechanism proceeded through an ordered transition state. Sample crystallinity affected the rate constants, activation parameters, and char yields of the untreated cellulose samples. Various additives had different effects on the mass loss. For example, phosphoric acid and aluminum chloride probably increased the rate of dehydration, while boric acid may have inhibited levoglucosan... 

Palmer et al have studied the pyrolysis of C302 at temperatures in the range 900-1100 °K by following the rate of carbon deposition from a He stream containing 0.1-0.5 mole % C302. The reaction was first order in C302 and was inhibited by the addition of CO a substance other than C302 or CO was responsible for carbon deposition at the wall. Reaction (1) and its reverse... 

However, the question whether the combustion of oxidised or weathered pulverised coal would maintain a self-sustaining flame in a full-size industrial boiler at maximum load cannot be addressed within the present study. The inhibition of volatile matter release, due to the promotion of char condensation reactions during coal pyrolysis, suggests that this may not be the case, a point pertaining especially to the more severely oxidised coals (i.e. 373 K for 112 days). Clearly there is need for ture work within this area of pulverised coal combustion. 

It is possible to inhibit reaction (5) by employing spray pyrolysis to deposit a compact layer of 2 on the Sn02 substrate before deposition of the nanocrystalline 2 film [9,10]. It is, however, relatively difficult to achieve a pinhole-free film. We chose to investigate the electropolymerization of an insulating film on the exposed parts of the Sn02 after the nanocrystalline 2 film has been depos-... 

Some semi-quantitative confirmation of these A factors comes from the consideration that the pyrolysis of C2H8 at 900°K. is a chain reaction in which the data on maximal inhibition indicate a chain length X of the order of 10. Since the only likely homogeneous, initiation process is the fission of C2H8 into 2CH3, the hypothetical first-order rate constant for the pyrolysis can be set equal to this initiation rate constant multiplied by X ... 

However, the considerable decrease in methane yield in the above case does not indicate the contribution of the hydroaromatic structure towards methane formation. It has been established (19, 23) that complete or even a partial dehydrogenation inhibits tar formation completely (though a minimum dehydrogenation is necessary for this effect) and retains all the hydroaromatic carbon in the char. The decrease in methane yield on pyrolysis of... 

Sagert and Laidler366 proposed that termination in the NO-inhibited pyrolysis of w-C4H10 is principally by... 

Day, M., Suprunchuk, T., and Wiles, D. M., Combustion and pyrolysis of poly(ethylene terephthalate) II. Study of the gas-phase inhibition reactions of flame retardant systems, J. Appl. Polym. Sci., 1981, 26, 3085-3098. 

For PC/ABS/PTFE, a combustion efficiency close to 1 (% = 0.98) was observed. Almost all volatile pyrolysis products were completely oxidized. This is in good accordance with the absence of a flame inhibition effect and the well-ventilated cone calorimeter fire scenario.33 Corresponding results have been reported previously for different polymers in the cone calorimeter.34 Adding BDP, RDP, and TPP results in a very similar flame inhibition activity in PC/ABS/PTFE (% = -0.8), increasing slightly in the order BDP < RDP < TPP.104 Using the combination of BDP and ZB results in the... 

Fenimore and Jones (12) report die first of their investigations into the modes of inhibiting polymer flammability. They show that chlorine substituted in polyethylene inhibits by affecting the pyrolysis of the condensed phase, but the pair of reactants, antimony plus a little chlorine, poisons the flame. Bromine is more effective than chlorine because it also poisons the flame. They speculate that halogen seems necessary to vaporize Sb from Sb203. 

It is a known fact that the gas-phase pyrolysis kinetics of alkyl bromides have not been extensively investigated due to the experimental difficulties as well as to the complexity of concurrent unimolecular and radical chain mechanisms. However, when these organic bromides are pyrolyzed under maximum inhibition, the reaction in the presence of a free radical suppressor is a molecular elimination. Sometimes, these organic bromides are pyrolyzed under maximum catalysis with HBr gas, and the process may proceed by an autocatalytic molecular mechanism. 

The result of a fall-off curve under maximum inhibition was compared with the theoretical curve estimated by the RRKM formulation. From the foregoing observations, the authors offered a reaction mechanism which may explain satisfactorily the process of the 1,2-dibromopropane pyrolysis. 

A previous investigation indicated that the pyrolysis of methyl 3-bromopropionate alone was autocatalyzed by the HBr gas product. However, under maximum free-radical inhibition the reaction was homogeneous, unimolecular and of first order111. Moreover, the acidity of the hydrogen adjacent to the COOCH3 was held responsible for the faster... 

The overall rate of elimination of methyl 4-bromocrotonate was found to be significantly higher than that of methyl 4-bromobutyrate (Table 22)171. The participation by the COOCH3 group is more effective as predicted67 because of the high polarity of the allylic C—Br bond in the transition state. The pyrolysis, under maximum inhibition, gave parallel reactions as described in equation 77. 

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