Pyrolysis, discussion

The influence of electrospinning parameters on the thermal stability of nanofibers on pyrolysis discussed. 

Toluene disproportionation (TDP) is a catalytic process in which 2 moles of toluene are converted to 1 mole of xylene and 1 mole of benzene this process is discussed in greater detail herein. Although the mixed xylenes from TDP are generally more cosdy to produce than those from catalytic reformate or pyrolysis gasoline, thek principal advantage is that they are very pure and contain essentially no EB. 

Flame or Partial Combustion Processes. In the combustion or flame processes, the necessary energy is imparted to the feedstock by the partial combustion of the hydrocarbon feed (one-stage process), or by the combustion of residual gas, or any other suitable fuel, and subsequent injection of the cracking stock into the hot combustion gases (two-stage process). A detailed discussion of the kinetics for the pyrolysis of methane for the production of acetylene by partial oxidation, and some conclusions as to reaction mechanism have been given (12). 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Because of the importance of the petroleum-based processes discussed previously, only about 1% of the U.S. supply of BTX currentiy comes from coal pyrolysis (21). 

After brief discussion of the state-of-the-art of modern Py-GC/MS, some most recent applications for stixictural and compositional chai acterization of polymeric materials are described in detail. These include microstixictural studies on sequence distributions of copolymers, stereoregularity and end group chai acterization for various vinyl-type polymers such as polystyrene and polymethyl methacrylate by use of conventional analytical pyrolysis. 

Two linear columns from Showa Denko, Shodex SB-806M and Shodex SB-806MHQ, and two linear columns from TosoHaas, TSK GM-PWxl and TSK GM-PW, were evaluated. Prior to the evaluation, the number of theoretical plates for Shodex SB-806MHQ, SB-806M, PWxl, and PW was determined to be 15,100, 15,700, 11,390, and 4710, respectively, as per manufacturer inspection. The lower plate count of the TSK PW column is due to the larger particle size of this column. Two mobile phases, water with 0.1 M LiNOi and 50 50 methanol/water (v/v) with 0.1 M LiNOi, were used for each of the four columns. These four columns were new and only PEO and PVP were analyzed with these columns in this study. Waters Ultrahydrogel columns have also been used in this laboratory. However, Ultrahydrogel columns are exactly the same as the TSK GM-PWxl columns based on the calibrations curves supplied by the manufacturers and by the pyrolysis GC data discussed later. 

The sources of biofuels and the methods for bioenergy production are too numerous for an exliaustive list to be described in detail here. Instead, electricity production using direct combustion, gasification, pyrolysis, and digester gas, and two transportation biofuels, ethanol and biodiesel, are discussed below. 

Ethylbenzene (C6H5CH2CH3) is one of the Cg aromatic constituents in reformates and pyrolysis gasolines. It can be obtained by intensive fractionation of the aromatic extract, but only a small quantity of the demanded ethylbenzene is produced by this route. Most ethylbenzene is obtained by the alkylation of benzene with ethylene. Chapter 10 discusses conditions for producing ethylbenzene with benzene chemicals. The U.S. production of ethylbenzene was approximately 12.7 billion pounds in 1997. Essentially, all of it was directed for the production of styrene. 

Decompositions of oxalates containing the strongly electropositive metals yield an oxide product but the more noble elements yield the metal. Discussion of the mechanisms of these reactions and, in particular, whether metal formation necessarily involves the intermediate production of oxide which is subsequently reduced by CO has been extended to consideration of the kinetics of pyrolysis of the mixed oxalates [32]. 

Details are given of ways of obtaining energy from the pyrolysis of disposable syringes. The waxy product was chemically modified with maleic anhydride and tested in the processing of PP/LLDPE blends in a rheometer or twin-screw extruder. Compatibility of components in binary or ternary blends and DSC results are discussed. 35 refs. 

Feedstock recycling is examined as a method of plastics recovery. The range of techno logics currently employed are described, and include pyrolysis, hydrogenation, gasification, and chemolysis. Methods for the recycling of mixed plastics wastes are discussed, which include work by BP Chemicals, VEBA Oil, Shell Chemicals and Leunawerke. 

The use of pyrolysis for the recycling of mixed plastics is discussed and it is shown that fluidised bed pyrolysis is particularly advantageous. It is demonstrated that 25 to 45% of product gas with a high heating value and 30 to 50% of an oil rich in aromatics can be recovered. The oil is found to be comparable with that of a mixture of light benzene and bituminous coal tar. Up to 60% of ethylene and propylene can be produced by using mixed polyolefins as feedstock. It is suggested that, under appropriate conditions, the pyrolysis process could be successful commercially. 23 refs. 

This article examines the recovery of automobile shredder residue (ASR), and considers three recovery options ASR as a landfill day cover, ASR in the production of composite materials, and the pyrolysis of ASR to recover chemical feedstock. All are discussed in detail. 

The kinetics of thermal decomposition and depolymerisation of various polymers is discussed. The aim of the study was to find reaction conditions where different polymers can be separated from mixtures by decomposing them into their monomers or into pyrolysis products and where chlorine and/or nitrogen are eliminated from the polymers without forming toxic compounds. Data are given for PVC, PS, PE, and PR 13 refs. 

Current methods of feedstock recovery are reviewed. Brief details are given of pyrolysis, hydrogenation, gasification, and chemolysis. Activities of some European companies are briefly discussed in the areas of recycling mixed plastics waste and closed-loop recycling. 

Recycling plastics back to hydrocarbons (tertiary recycling) may offer significant promise. Three different options currently being evaluated for the tertiary recycling of polyolefins - refinery recycling, pyrolysis and depolymerisation - are discussed. 

This paper discusses the effects of the pyrolysis of wood and paper treated with pentachlorophenol or sodium pentachlorophenate along with the exposure of sodium pentachlorophenate to ultraviolet light. The effect of heat, light, and air with respect to some of the chlorinated dibenzo-p-dioxins will be considered. 

---