Pyrolysis volatile products

The beneficial effects are demonstrated of heterogeneous secondary pyrolysis reactions on the liquid products of PU pyrolysis. Pyrolysis volatiles are passed through a packed bed of carbonaceous solids that promote the secondary reactions. Activated carbon and reaction injection moulded PU (RIM) char were found to be suitable bed materials. The long-term object was to develop marketable solid products by pyrolysis of wastes, so obtaining high char yields. In addition to affecting the liquid products, RIM char also increased the total char... 

Pyrolysis gas chromatography is an indirect method of analysis in which heat is used to transform a sample into a series of volatile products characteristic of sample and the... 

Mass spectrometry (MS) coupled with pyrolysis has been a key technique in detecting the thermal degradation products of polymers, and thereby elucidating their thermal decomposition pathways [69]. In pyrolysis-MS, a sample is thermally decomposed in a reproducible manner by a pyrolysis source that is interfaced with a mass spectrometer. The volatile products formed can then be analysed either as a mixture by MS or after separation by GC/MS [70]. 

V.A. Basiuk, Pyrolysis of valine and leucine at 500°C identification of less volatile products using gas chromatography Fourier Transform infrared spectroscopy mass spectrometry, J. 

The two polymer substrates investigated as part of the study of DBDPO mixtures were polypropylene (PP) and linear high density polyethylene (HDPE). while both PP and HDPE decompose by similar random chain scission, radical mechanisms, chain transfer occurs much more teadily during the pyrolysis of PP because of the presence of the tertiary hydrogens. In addition, only primary chain end radicals are formed when the HDPE chain cleaves homolytically. Therefore, a comparison of the PP/DBDPO and the HDPE/DBDPO mixtures volatile product distributions was undertaken. 

Heating pure TBMS, TBS and TBSS films at 130 C gave no volatile products. Pyrolysis at 725°C gave rise to both deprotection (as determined by the evolution of isobutene and carbon dioxide), and depolymerization to afford the respective monomers, sulfur dioxide, 4-hydroxystyrene, or 4-hydroxy-a-methylstyrene. The compounds, 4-hydroxystyrene and 4-hydroxy-a-methylstyrene, were identified on the basis of their mass spectra, which were consistent with those reported in the literature for these materials (22,23). Additionally, TGA analysis confirmed that all three polymers undergo complete volatilization upon heating to >400 C. 

Non volatile organic compounds are not amenable for gas chromatography. However, some types of non volatile compounds, upon pyrolysis, yield volatile products which are characteristic of the original substance and can be used as a basis of a method for estimating these substances. 

Various pyrolysis processes have been reported in the literature. A popular approach, called flash pyrolysis, applies high temperature and short residence time to minimize the condensation of the volatile products. The BTG wood Pyrolysis process is a typical example. 

The wood pyrolysis is attractive because forest and industrial wood residues can be readily converted into liqtrid products. These liqtrids, as erode bio-oil or slurry of charcoal of water or oil, have advantages in transport, storage, combustion, retrofitting and flexibility in production and marketing (Demirbas, 2007). In the first step of pyrolysis of carbohydrates dehydration occtrrs and at low temperatures dehydration predominates. Dehydration is also known as a char-forming reaction. Between 550 and 675 K volatile products, tar, and char are formed. The volatile products are CO, CO, H O, acetals, furfural, aldehydes and ketones. Levoglucosan is the principle component in tar. 

Vacuum pyrolysis reactions were typically performed in sealed T-shaped Pyrex tubes in a temperature controlled ( - funmee. Volatile products were collected in the side arm trap... 

The volatile components from coal pyrolysis are primarily small hydrocarbons and oxygen-containing molecules. By adding H2O and limited O2 and while heating coal, these products incorporate considerable 0 atoms into the volatile products to form alcohols, aldehydes, ketones, and acids. However, these products consist of many molecules that... 

Coke and charcoal are highly porous, coke from the holes left behind when the volatile components evaporate, and charcoal remains from the cellular framework of wood fibers. Addition of limited air in pyrolysis produces more volatile products and makes a more porous carbon residue. 

Neither the thermal nor the cobalt-catalyzed decomposition of 3-butene-2-hydroperoxide in benzene at 100 °C. produced any acetaldehyde or propionaldehyde. In the presence of a trace of sulfuric acid, a small amount of acetaldehyde along with a large number of other products were produced on mixing. Furthermore, on heating at 100°C., polymerization is apparently the major reaction no volatile products were detected, and only a slight increase in acetaldehyde was observed. Pyrolysis of a benzene or carbon tetrachloride solution at 200°C. in the injection block of the gas chromatograph gave no acetaldehyde or propionaldehyde, and none was detected in any experiments conducted in methanol. 

Analogously, the thermolysis of the 1-methyl derivative in bis(2-methoxyethyl) ether (diglyme) at 160 °C for 30 minutes gave 2-methyIbicyclo[3.2.0]hept-l-ene (5) with 82% selectivity in 12% overall yield, while flash-vacuum pyrolysis (250°C/1 x lO -lO 3 Torr) gave 5 with 75% selectivity and 47-68% overall yield of volatile products.68... 

In a modified flash-vacuum-pyrolysis apparatus (Otto Fritz company, Hofheim, Germany) the Na salt of l-methylbicyclo[2.2.1]heptan-7-one tosylhydrazone (1 g, 3.2 mmol) was added in small portions over 1 h to silylated silica gel (2 - 3 g) in a preheated (250 "C) pyrolysis flask at 1 x 10 4-10 3 Torr. The volatile products (47-68%) were collected in a cooled [N2(1)J flask and were separated by preparative GC (Car-bowax + KOH on Chromosorb W, 4.5 m, 60 °C). 

Table III. Volatile Products from Pyrolysis of a Novolak Resin (Ref. 25)...

Several zeolites were used both in original and calcined form. The volatile products of pyrolysis either analyzed directly by GC/MS or after passing over the respective zeolites. 

The presence of zeolite catalysts increases the amount of gaseous hydrocarbons produced during pyrolysis but decreases the amount of pyrolysis oil. Further, significant quantities of coke were formed on the surface of the catalysts in the course of pyrolysis. The catalysts reduced the yield of e.g., as styrene and cumene, in favor of naphthalene. The zeolite catalysts, especially Y-Zeolite, were found to be very effective in removing volatile organo bromine compounds. However, they were less effective in removing antimony bromide from the highly volatile products of pyrolysis (133). 

Peter H. Given J. R. Jones and I have studied the pyrolysis of some aromatic sulfur compounds, including dibenzothiophene and thioxanthone (dibenzothiopyrone). Much of the sulfur is lost from the thioxanthone as volatile products, whereas much of the sulfur in dibenzothiophene is retained in the char. The difference in behavior no doubt arises from some difference in aromatic stability between the two sulfur heterocycles hence, aromaticity or aromatic character may well be a general factor determining how much sulfur is retained in the char on pyrolysis. 

Pyrolysis. A technique by which nonvolatile samples are decomposed in the inlet system and the volatile products are separated in the chromatographic column. 

Study of Volatile Products from Thermal Analyzers. The MC-2 mass chromatograph is ideally suited for thermal analysis or pyrolysis studies for the obvious reasons of quantitative and qualitative analysis and also for its unique trapping assembly. With the traps, sample effluents can be collected and concentrated over extended periods of time prior to analysis. 

Pyrolysis. In the pyrolysis experiment, typically 30 mg of sample was heated in a quartz tube at 400°C for 24 hrs at 2xl0"6 torr. Tars were trapped at room temperature and the more volatile products at liquid nitrogen temperature. These two fractions were analyzed by GCMPES (MPD-850) using a 25m x 0.25 mm i.d. OV-101 fused silica column and by GCMS (Kratos MS-25) using a 30m x 0.25 mm i.d. DB-5 column. 

A more detailed study of the pyrolysis of H3SiMn(CO)5 in a sealed tube for various periods of time at 450°C showed that the volatile products were H2, CO, SiH. , and CH4 a metallic-looking brown film covered the walls of the tube, and an apparently amorphous grey powder was also present (33). Figure 5 shows that hydrogen and methane are produced in increasing amounts as the reaction proceeds, while CO reaches a steady concentration after about 10 min. Silane reaches a maximum concentration after about 5 min, then decreases to zero after 60 min. silane is known to decompose to silicon and hydrogen above about 425°C (368), and its presence is readily accounted for by the disproportionation reaction (109). 

Fig. 5. Volatile products from the static pyrolysis of H 3iMn(CO)5. Key left-hand scale, SiH O, CH, A right-hand scale, H2 , CO .

The addition of a Lewis acid, i.e., ZnC significantly decreases the production of tar and enhances the production of char due to the enhanced dehydration reactions. At higher temperatures the glycosyl units and the random condensation products are further degraded to a variety of volatile products, as shown in Table V (9). Comparison of this table with the high temperature pyrolysis products listed for cellulose in Table III shows that the products of both fractions are basically similar. The significant increase in the yields of 2-furaldehyde, water and char and decrease in the yield of tar by the addition of ZnCl verifies the enhanced dehydration and is similar to observed effects in cellulose pyrolysis. 

When heated under nonisothermal conditions, the maximum volatile product evolution temperature was 425°C for isotactic PP, yielding volatile products comprising dienes, alkanes, and alkenes. Furthermore, the hydrogen content of pyrolysis products obtained by flash pyrolysis at 520°C indicates the magnitude of the flammability problem in term of its fuel-forming potential.23 The flammability of volatiles is further enhanced by the abundance of unsaturated less-volatile fuel fragments that behave as secondary fuel sources and which decompose further.24... 

L. Ballice, Classification of volatile products evolved during temperature-programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP). Fuel, 81(9),1233-1240 (2002). 

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