Pyrolyzed sample

Another possible explanation for activity in these materials is that metal centers can reform once the catalyst is placed in the electrolyte. It has been established that a portion of the metal dissolves when pyrolyzed samples are placed in an acidic solution, and interestingly, such a wash improves activity.72 It is thus possible that... 

A final issue that faces this class of catalysts is stability in the fuel cell environment. Deactivation of materials in a fuel cell environment has been shown to be minimal in some studies,31,137 and severe in others.128,142 More active catalysts seem more susceptible to deactivation. Deactivation has been linked to the formation of peroxide and the loss of metal from the catalyst.128 On the other hand, demetallization has also been observed in pyrolyzed samples that did not lose activity with time.84 Another possible mode of deactivation could be due to the oxidation of the carbon surface. However, it seems reasonable that a complete understanding of the deactivation mechanism would first require a well-developed understanding of the active site. 

Conductive polymers do not perform particularly well as ORR catalysts compared to the most active pyrolyzed samples. While a measurable ORR current is often observed at potentials as high as 0.6 V v.y. NHE, the current is generally slow to take off.171 The PANI samples are only active when the polymer is in its reduced... 

Results for Pyrolyzed Samples. The complete set of data obtained is collected in Table III and some typical trends are shown in Figures 4 and 5. For consistency, the figures shown for unpyrolyzed samples are all data obtained by the Penn State group. At 550°C. the vitrinites suffered about 25%... 

Pyrogram. The resulting chromatogram from the sensing of the fragments of a pyrolyzed sample. 

A patented process has been developed for the production of electrode binder pitch from petroleum-based materials. Carbon anodes produced from the petroleum-based pitch and coke have been used successfully on a commercial scale by the aluminum industry. One stage of the process involves the pyrolysis of a highly aromatic petroleum feedstock. To study the pyrolysis stage of the process a small, sealed tube reactor was used to pyrolyze samples of feedstock. The progress of the reaction is discussed in terms of the formation of condensed aromatic structures, defined by selective solvent extraction of the reaction product. The pyrolysis of the feedstock exhibits a temperature-dependent induction period followed by reaction sequences that can be described by first-order kinetics. Rate constants and activation energies are derived for the formation of condensed aromatic structures and coke. 

It is likely that the iodine-catalyzed decomposition is a chain reaction initiated by iodine atoms. The iodine-catalyzed decomposition has also been studied with mixtures of acetone and acetone-c/g. The isotope distribution of the acetone in the pyrolyzed sample has been found to approach the composition expected on statistical grounds. The rapid isotope mixing indicates the presence of chains. 

The second gc technique determined the individual n-alkanes and 1-alkenes in the pyrolyzed sample. A 100 m wall-coated glass capillary gave the required resolution and the n-alkanes and 1-alkenes stood out as distinct, well resolved peaks. OV-101 or OV-17 wall coatings provide adequate separation. A carrier gas flow of one cc/min was combined with an inlet split ratio of 50 1 and a 310°C injector temperature. The column temperature was raised to 250°C at 4°/min after an 8.0 min initial hold at 80°C. Peak identification was based on retention time matching with n-alkane and 1-alkene standards. 

The MP-3 multipurpose thermal analyzer is manufactured by the Spex Industries. It pyrolyzes sample at programmed rates from 4°/min-40°C/min up to 1000°C. It was modified by the addition of two laminar flow controllers (HGC 187 Analabs) which provide controlled atmospheres of up to four gaseous mixtures. The CDS 820 (Chemical Data Systems) consists of a Pyroprobe 100 capable of delivering to a polymer sample a maximum heating rate of 20,000°C/sec the CDS 820 provides a controlled atmosphere for the Pyroprobe. 

Consider the pyrolysis of a small sample of organic material in the pyrolysis zone of the tubular reactor system. At any time t the rate of evolution of gaseous volatile matter (rriv) from the pyrolyzing sample is given by ... 

Fig. 5. GC-MS key ion plots for the alkylnaphthalene series in the unheated and pyrolyzed samples 1-7 (sum of m/z 128, 142, 156, 170 and 184 pyrolysis temperatures are indicated 1, naphthalene 2, 2-methylnaphthalene 3, 1-methylnaphthalene 4, dimethylnaphthalenes 5, trimethylnaphthalenes 6, tetramethylnaphthalenes and bibenzothiophene).

Fig. 8. GC-MS key ion plots for the thio-PAHs in the pyrolyzed samples 2-7. Sum of m/z 184, 234, 284 temperatures are indicated 1, dibenzothiophene 2, benz[T ]naphtho[l,2-d]thiophene 3, benzo[b]-naphtho[2,l-d]thiophene 4, benzo[b]naphtho[2,3-d]thiophene peak cluster at scans 1300-1420, dinaphthothiophenes.

Fig. 10. (a) Plot of organic carbon versus stable carbon isotope composition for the kerogen concentrates of the composited unheated and pyrolyzed samples, (b) Plot of the stable carbon isotope composition versus pyrolysis temperature for the kerogen concentrates (sample numbers cf. Tables 1 and 2, samples 1 and 8 are the unheated composites). 

All the pyrolyzed samples were XRD amorphous. Weight loss ( 28 weight-%) and linear shinkage ( 29%) associated to the pyrolysis treatment were found to be... 

In order to pyrolyze samples rapidly for introduction to a gas chromatograph, furnace pyrolyzers are generally held isothermaUy at the desired pyrolysis temperature and the samples introduced into the hot volume. Carrier gas is generally routed through the furnace to remove the pyrolysate quickly from the pyrolysis zone to minimize secondary pyrolysis. 

Dilution tests were carried out by supplementing the original air stream of 100 dm h with an additional air supply of 50 to 1400 dm h. Through the exposure chamber, the flow rate of the gas mixture was 200 dm h in each case. The sample size in the quartz tube was adjusted so that the mass flux of pyrolyzed sample produced by the moving oven was 0.12 g/cm. 

Further, they normalized the CO2 capture capacities in accordance with narrow micropore volume and nitrogen content, with the aim to determine the influence of both textural and surface chemistry properties on their capture performance. The normalization of the CO2 capture capacities by the narrow micropore volume shows the effect of surface chemistry properties of the samples on the CO2 uptake, while the normalization by nitrogen content exhibits the contribution of textural properties. From the results, we can assume that samples prepared from low treatment temperature (i.e., 600 °C) exhibit the greatest capacity per narrow micropore volume, while high-tem-perature pyrolyzed samples show increased contribution by the micropores. 

Pyrolysis is based on the rapid heating of the sample under controlled conditions and online identification of the decomposition products. GC, FTTR, and MS are used for the analysis of the pyrolyzed samples. 

Fig. 16.13 Effect of heat treatment on the kinetic current density for oxygen reduction for some Co, Fe, and metal-free macrocycles (Pc phthalocyanine, OEP octaethylporphyrin and TPP tetraphenylporphyrin). All samples were supported on the same carbon black for the pyrolyzed samples, the highest kinetic current densities are given, achieved after a heat treatment at temperatures ranging from 600 to 800°C. Current values were taken from [41], figure 1...

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