Pyrolysis Product Composition

It can be seen that under these conditions high amounts of aromatics are produced. The benzene content is 12.2 wt% at a pyrolysis temperature of 740°C and 24.75 at 780°C. Other main components of the PE pyrolysis (780°C) are methane, ethylene, and propene as gas and toluene, naphthalene as aromatics. The amount of carbon soot is low. Tire pyrolysis produces mainly carbon black (filler), gas, and aromatics. Steel cord is one of the other main products if whole tires are fed. 

The pyrolysis of polypropylene gives similar results to the pyrolysis of polyethylene (Table 17.3). The amount of methane and oil is slightly higher, the amount of aliphatics is lower. The feedstock recycling of polyolefins is easy. Up to 50 wt% can be obtained as aromatics if the pyrolysis gas is cycled and used as fluidizing gas. The other 50% are gas components. Benzene and toluene reach 25 wt%. 

A real plastic waste collected by the German Dual System (DSD) from municipal packaging waste was pyrolyzed in the laboratory plant as well as in the pilot plant. The composition of the mixed plastic wastes is shown in Table 17.4. 

Beside polyolefins it contains polystyrene, polyesters, and PVC up to 4% and others. Table 17.5 gives a detailed composition of the obtained pyrolysis products. 

The results are similar to those with polyolefins as feedstock, but the amount of styrene is higher because of the high amount of polystyrene in the feed. The HCl coming out from PVC was quantitatively absorped by calcium oxide which was added in 5% weight to the feed. The CaCb formed was separated in the cyclone after the fluidized-bed reactor. 

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Table 9.1 Biomass ultimate analysis and primary pyrolysis product compositions...

Similarly, low-temperature photolysis of 4,5,6-fluorosubstituted 1,2,3-tna zines results in the elimination of nitrogen, but the product composition depends on the substituents When the substituents are fluonne atoms, the intermediate product IS a four-membered, mtrogen-contaming ring that quickly dimenzes When all the substituents are perfluoroalkyl groups, the pyrolysis results in a mixture perfluoroalkyl acetylenes and perfluoroalkyl cyanides [79] (equations 48 and 49). 

In cyclic systems, conformational effects and the requirement for a cyclic TS determine the product composition. This effect can be seen in the product ratios from pyrolysis of /V,/V-dimethyl-2-phcnylcyclohexylaminc-/V-oxide. 

If additional information pertaining to the rubber composition were sought, FTIR analysis of the pyrolysis products would have been performed. Even more detailed analysis can be obtained by gas chromatography (GC) separation of the multiple pyrolysis products followed by mass spectrometric (MS) detection. The gas chromatography-mass spectrometry (GC-MS) method is well suited to deformulation and contaminant analysis. 

As expected, the composition of feedstock can greatly impact the pyrolysis product yields. Table 4.2 reports product yields from pyrolysis of various biomass and fossil feedstocks at 500°C. 

Several researchers have shown that alkali present in the feedstock influences the yields and compositions of the pyrolysis products [56, 59]. An interesting result was reported by Brown and coworkers [60] who found that addition of (NH4)2S04 as catalyst to the pyrolysis of dematerialized (alkali free) corn stover resulted in a pyrolysis oil that contained 23 wt.% levoglucosan (normally 1-3 wt.% levoglucosan is present in pyrolysis oil). Levoglucosan is a component from which various fuel blends and chemicals can be produced. 

This example belongs to chemotaxonomy, a discipline that tries to classify and identify organisms (usually plants, but also bacteria, and even insects) by the chemical or biochemical composition (e.g., fingerprint of concentrations of terpenes, phenolic compounds, fatty acids, peptides, or pyrolysis products) (Harbome and Turner 1984 Reynolds 2007 Waterman 2007). Data evaluation in this field is often performed by multivariate techniques. 

Mansuy et al. [97] investigated the use of GC-C-IRMS as a complimentary correlation technique to GC and GC-MS, particularly for spilled crude oils and hydrocarbon samples that have undergone extensive weathering. In their study, a variety of oils and refined hydrocarbon products, weathered both artificially and naturally, were analyzed by GC, GC-MS, and GC-C-IRMS. The authors reported that in case of samples which have lost their more volatile n-alkanes as a result of weathering, the isotopic compositions of the individual compounds were not found to be extensively affected. Hence, GC-C-IRMS was shown to be useful for correlation of refined products dominated by n-alkanes in the C10-C20 region and containing none of the biomarkers more commonly used for source correlation purposes. For extensively weathered crude oils which have lost all of their n-alkanes,it has been demonstrated that isolation and pyrolysis of the asphaltenes followed by GC-C-IRMS of the individual pyrolysis products can be used for correlation purposes with their unaltered counterparts [97]. 

The composition of the conversion gas corresponds to the sum of the inorganic and organic gaseous pyrolysis products illustrated in Figure 54... 

Complex pyrolysis chemistry takes place in the conversion system of any conventional solid-fuel combustion system. The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicellulose, and lignin. Pyrolysis of these biopolymers proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products which can be divided into char, volatile (non-condensible) organic compounds (VOC), condensible organic compounds (tar), and permanent gases (water vapour, nitrogen oxides, carbon dioxide). The pyrolysis products should finally be completely oxidised in the combustion system (Figure 14). Emission problems arise as a consequence of bad control over the combustion system. 

The qualitative investigation of copolymers is considerably more difficult when the homopolymers cannot be distinguished by their solubility. In this case other physical data of the supposed copolymer can be compared with the corresponding data for various physical mixtures of homopolymers, for example, softening point and melting range, density, and crystallinity. Copolymers can frequently be distinguished from physical mixtures of homopolymers by the qualitative and quantitative composition of their pyrolysis products. 

Rabinovitch and Setser107 found no effect upon adding up to 10% 02 in the reaction of CH2, produced by CH2N2 pyrolysis, with olefins. Frey,42 however, observed a striking effect on the product composition upon the addition of a few mm. of 02 in the photolysis of CH2N2-cfs-2... 

In some instances, subtle changes in the precursor architecture can change the composition and microstructure of the final pyrolysis product. For example, pyrolysis of —[MeHSiNH] — leads to amorphous, silicon carbide nitride (SiCN) solid solutions at >1000°C (see SiCN section). At ca 1500 °C, these material transform to SisN SiC nanocomposites, of interest because they undergo superplastic deformation20. In contrast, chemically identical but isostructural — [F SiNMe] — transforms to Si3N4/carbon nanocomposites on heating, as discussed in more detail below21. 

The pyrolysis products from 9.13 can give essentially pure silicon carbide in 89% yield. Intermediates that contain from 5 to 25% allyl functionalized units give ceramics with progressively larger amounts of carbon beyond the 1 1 Si C ratio. This process has been developed into a manufacturing sequence for the production of reinforced composites for aircraft brakes and high temperature coatings. 

Curie point pyrolysis mass spectrometry has also been valuable in providing information about the chemical types that are evolved during the thermal decomposition of coal (Tromp et al., 1988) and, by inference, about the nature of the potential chemical types in coal. However, absolute quantification of the product mixtures is not possible, due to the small sample size, but the composition of the pyrolysis, product mix can give valuable information about the metamorphosis of the coal precursors and on the development of the molecular structure of coal during maturation. However, as with any pyrolysis, it is very important to recognize the nature and effect that any secondary reactions have on the nature of the volatile fragments, not only individually but also collectively. 

It appears, then, that there is a general, meaty aroma, common to cooked beef, pork, and lamb (and probably poultry), attributable to the pyrolysis of the mixture of low molecular weight nitrogenous and carbonyl compounds extracted from the lean meat by cold water. But the aromas of roast beef, roast pork, roast lamb, and roast chicken are unmistakably different. The chemical composition of the muscular fat deposits of these animals differ appreciably, and it is to these lipid components that we must look to account for the specific flavor differences. Heating the carefully separated fat alone does not give a meaty aroma at all, much less an animal-specific one. It is the subsequent reactions of pyrolysis products of nonlipid components that give the characteristic aromas and flavors of roasted meats (20). 

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