Pyrolysis Computer Programs

The pyrolysis high resolution mass spectrometry (PyHRMS) technique has been described in detail previously (20). Briefly, the coal sample was placed on a platinum rhodium mesh on the end of a probe as a slurry. After the solvent had evaporated, the probe was inserted into the mass spectrometer and positioned within 5 mm of the source. The probe, which had been previously calibrated with an infra-red thermometer, was computer-controlled to give a temperature profile beginning at 100°C and increasing at 50°C/min to 800 C. The precise masses were matched to their corresponding chemical structures by computer programs developed in-house. This technique results in the relatively slow vacuum pyrolysis of the coal sample. 

Chemical kinetics describes the change of species with time under the conditions of nonequilibrium. For qualitative statements, we require a reaction mechanism and the associated kinetic constants of the individual reactions. For special areas, like pyrolysis and flames, there are already sophisticated computer programs, which develop automatically kinetic models [1] and perform a data reduction [2]. Also in the field of geochemistry, such programs are available [3]. 

SPYRO is a computer program for calculating a steamcracking reactor with hydrocarbon loads ranging from ethane to the naphthas. The computer program contains a detailed reaction mechanism for the pyrolysis of molecules containing from 1 to 4 carbon atoms and lumped mechanisms for larger species. The approach developed by the authors has been validated industrially. 

Comparison of commercial computer programs for investigation of kinetics of pyrolysis and oxidation reactions of heavy petroleum products... 

Pyrolysis-Gas Chromatography-Mass Spectrometry. In the experiments, about 2 mg of sample was pyrolyzed at 900°C in flowing helium using a Chemical Data System (CDS) Platinum Coil Pyrolysis Probe controlled by a CDS Model 122 Pyroprobe in normal mode. Products were separated on a 12 meter fused capillary column with a cross-linked poly (dimethylsilicone) stationary phase. The GC column was temperature programmed from -50 to 300°C. Individual compounds were identified with a Hewlett Packard (HP) Model 5995C low resolution quadruple GC/MS System. Data acquisition and reduction were performed on the HP 100 E-series computer running revision E RTE-6/VM software. 

The HRMS data were collected on a Kratos MS-50 operating with an El source at low eV with resolving power of 80,000 (batch tars) and at 70 eV with 50,000 resolution (in situ pyrolysis). The data was transferred to another computer system and analyzed using a program which we have developed. Initially, empirical formulae were assigned and deviations between calculated and observed masses determined. Next, peaks were sorted by heteroatom content, and finally by hydrogen deficiency (HD = rings... 

Py-GC experiments were performed using a modified SGE pyrolysis inlet, interfaced either with a Chrompack gas chromatograph (model 437S) equipped with a flame ionization detector and a double flame photometric detector or with a Delsi gas chromatograph (model DI300) interfaced with a Delsi mass spectrometer (model R10 10). The control of the Chrompack GC and the data acquisition were done with a PCI-Chrompack program and a PC computer. 

The reaction mechanism used for this study was the alkane pyrolysis scheme of Edelson and Allara. [10] This consists of 98 reactions involving 38 chemical species. It is not so large that it overburdens the computers used yet is of a size sufficient to yield meaningful timing of the program modules. 

Two approaches to autosampling with resistively heated filaments are available, one in which multiple filaments are used and one in which a common filament is used. The former uses up to 14 different filament interfaces, each of which is connected sequentially to the gas chromatograph for pyrolysis. The computer permits individual control of each filament, so each sample may be analyzed using a different program. Like the Curie-point systems, the samples may be placed directly onto the heating filament. 

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