Pyrolysis procedure

The endothermic nitride is susceptible to explosive decomposition on friction, shock or heating above 100°C [1], Explosion is violent if initiated by a detonator [2], Sensitivity toward heat and shock increases with purity. Preparative precautions have been detailed [3], and further improvements in safety procedures and handling described [4], An improved plasma pyrolysis procedure to produce poly (sulfur nitride) films has been described [5], Light crushing of a small sample of impure material (m.p. below 160°C, supposedly of relatively low sensitivity) prior to purification by sublimation led to a violent explosion [6] and a restatement of the need [4] for adequate precautions. Explosive sensitivity tests have shown it to be more sensitive to impact and friction than is lead azide, used in detonators. Spark-sensitivity is, however, relatively low [7],... 

In our research at MIT we have found transition metal chemistry a very useful aid in the preparation of silicon-containing ceramics by the polymer pyrolysis procedure. 

From studies of the reactions of 2-arylazirines it is evident that transition metal carbonyls can also effect reactions under mild conditions to give products that would be obtained from alternative pyrolysis procedures. 

Pyrolysis Procedure and Sample Preparation. Pvrolyzed samples were prepared by heating 0.1-0.2 gram maceral in a boat under a stream of oxygen-free nitrogen at 10°/min. to the desired temperature, and maintaining the sample at that temperature for 1 hour. 

To obtain carbon membranes with molecular sieving properties, pore diameters in the range of a few angstroms are required. The associated pyrolysis procedures and post treatments are more involved. This subject will be treated later under section 3.2.10 Molecular Sieving Membranes. 

Pyrolysis Procedure. The shale oil samples were stressed at conditions similar to the petroleum refining process known as delayed coking (6). These conditions are 450°C and about 90 psi pressure. Each Thermal stress was conducted in a 1/4 inch o.d. 316 stainless steel tube fitted with a stainless steel valve via a Swagelok connection. The tube, with a weighed amount of sample (approximately 0.1 g), was attached to a vacuum system, cooled to -78°C, and pumped to remove air. The tube was then thawed and the cooling/pumping process repeated. The tubes were heated by inserting them into 9/32-inch holes in a six-inch diameter aluminum block fitted with a temperature controller. 

The pyrolysis procedure we used for phenylphosphonous dichloride was first reported by Michaelis in the 1870 s. In our first small pilot plant using hot tubes, we got only 2-3% conversion per pass of the reactants. Even though the unconverted reactants were recycled, the low conversion rate per pass was definitely a short-coming. 

Bromine and chlorine substituents have been employed in most syntheses as a compromise of thermal stability and reactivity of the reactants necessary in the pyrolysis procedure as outlined above. Needless to say that these halogen substituents must normally be introduced at those carbon atoms which eventually participate in the new C-C bond. If this is not possible for synthetic reasons, the substitution in other positions can provide an interesting alternative. It has... 

As the pyrolysis conditions have a marked effect on the range of the resulting products, on the reproducibility of the results obtained and on the relationship between the composition of the pyrolysis products and the nature (composition) of the pyrolysed sample, a great deal of attention is paid to the pyrolysis procedure and equipment in the literature. 

Py-GC finds extensive application in the identification of rubbers. The results obtained in this area have been summarized by Malyshev and Pomogaibo [150], who presented pyrograms of the pyrolysis products of a large number of rubbers with a detailed description of the pyrolysis procedure. 

The calculation of the relative characteristic peak areas on the chromatograms of the volatile pyrolysis products, using an external standard irrespective of the pyrolysis procedure, permits one to take into account the sensitivity of the detector, with easy computation of the ratio between the peak areas of the component of interest and the standard which, under normal conditions (sample size, carrier gas flow-rate, pyrolysis temperatures, etc.) are proportional to the absolute amounts of the pyrolysis products. This method of calculation is essentially a modification of the absolute calibration method in gas chromatography, which had never been used before in Py—GC.To facilitate comparison of the results obtained at different times or on different instruments, the results of individual measurements should preferably be presented in terms of specific yields (or relative characteristic peak areas), i.e., the yield of the volatile pyrolysis products must be calculated per 1 mg (or g or ng) of the pyrolysed sample with respect to 1 mg (or g or Mg) of the external standard. Such a calculation makes sense in the range of sample sizes which affect only insignificantly the specific yield of light pyrolysis products. 

Stahl (95) described a pyrolysis procedure that also used TLC to identify... 

In a study of the effect of steady-state pyrolysis of tobacco vs. pulsed pyrolysis simulating the pnfting seqnence in a smoked cigarette, Patterson et al. (2904) reported that the pulsed pyrolysis procedure gave much higher levels of the low molecular weight phenols (phenol, 2-, 3-, and 4-methylphenol [o-, m-,and... 

The reactions depicted above in pyrolysis of a component vs. those in the cigarette smoking process with a component added to the tobacco exist despite the assertion that the pyrolysis procedure has been specifically designed to simulate the smoking process (172b, 1648, 3616). 

In addition, the destructive distillation procedure used by Roffo is not comparable to the pyrolysis procedures used several decades later by other investigators, for example, Lam (2255, 2257) and Wynder et al. (4355). Roffo s work is presented here for the sake of historical completeness. In later reports, Roffo (3323, 3325) and his son (3316, 3318) claimed the identification of B[a]P in the destructive distillate of tobacco, but these claims were subsequently challenged by Wynder et al. (4306a) who noted ... 

Photoelectron and microwave spectroscopy have been used to detect and optimize the formation of various phosphaalkynes, RC=P, in gas-phase flow-pyrolysis procedures. Photoelectron spectra show that the ionization processes observed relate to electron-removal from orbitals of essentially n(CP) character. A close analogy exists between the ligand properties of such phosphaalkynes towards transition metals and those of conventional alkynes. ... 

Fig. 2.9 a The H-bonds between the PS-P4VP block copolymer and a phenolic resin, b As a result of H-bonding, the phenolic resin and P4VP are confined within the same self-assembled domains as they have microphases separated from the nonpolar PS domains. Crosslinking at elevated temperatures locks the structure, c Depending on the pyrolysis procedure, different pores are created with hydroxyl groups in the pore interior. Reproduced from Ref. [49] by permission of John Wiley Sons Ltd... 

Nowadays, analytical pyrolysis is widely used. Recently, there have been significant improvements in the pyrolysis procedure and, by coupling pyrolysis to gas chromatography (GC) and mass spectrometry (MS) a significant body of structural information on humic substances may be obtained. However, quantitation of pyrolysis GC-MS is limited by matrix effects that distorts the signals of detected and the high temperatures used during pyrolysis produce... 

As can be recognized, the micropore volume of the carbon is reduced by the impregnation, but again increased by the pyrolysis procedure. Note also that the average pore radius is somewhat shifted to a lower value by the impregnation but again increases after pyrolysation [1.36]. 

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