Temperature-controlled pyrolysis

The formation of dimeric fluorinated products via heat-induced bond breaking has been more or less restricted to industrial processes. Thus, the pyrolysis of trifluoromethane (1) and chloro-difluoromethane (3) are the two industrial sources for tetrafluoroethene (2), hexafluoropropenc (4). and their corresponding oligomers and polymers.1-2 Hexafluoropropene (4) is formed as a byproduct in the pyrolysis of chlorodifluoromethane (3) however, a temperature-controlled pyrolysis of 3 has been worked out as a commercial process for the production of 4.3... 

Recently the pyrolysis of polymer mixtures has become a focus of interest due to the increasing role of plastics recycling. Many researchers have investigated the thermal decomposition of various polymers in the presence of PVC. Kniimann and Bockhom [25] have studied the decomposition of common polymers and concluded that a separation of plastic mixtures by temperature-controlled pyrolysis in recycling processes is possible. Czegfny et al. [31] observed that the dehydrochlorination of PVC is promoted by the presence of polyamides and polyacrylonitrile however, other vinyl polymers or polyolefins have no effect on the dehydrochlorination. PVC generally affects the decomposition of other polymers due to the catalytic effect of HCI released. Even a few per cent PVC has an effect on the decomposition of polyethylene (PE) [32], HCI appears to promote the initial chain scission of PE. Day et al. [33] reported that PVC can influence the extent of degradation and the pyrolysis product distribution of plastics used in the... 

Gallorini, M., Orvini, E.. Goetz, L., "PTetra, R., Sabbioni, E. (1987). Arsenic speciation in solid biological specimens by temperature-controlled pyrolysis and NAA, J. Radioanal. Nucl. Chem., Articles 112,125-132. 

Examination of flame-retarding additives was done by Heeren et al. using a direct temperature controlled pyrolysis external ion source and a 7 T FTICR. Samples were taken from common household appliances such as TV set housings, computer casings, and others and were pulverized to powder form. Direct heating of the filament probe with dried sample produced spectra with two distinct regions, corresponding to evaporation of nonbonded additives and pyrolysis of the polymer matrix. The xmknown polymer blends were foxmd to contain brominated biphenyls, brominated diphenyl ethers, tetrabromoBisphenol-A and its butylated isomers, polystyrene, and antimony oxides. 

Linear-temperature controlled pyrolysis with subsequent analysis of the pyrolysates (volatiles and residues) by FTIR spectroscopy can provide information on the thermal degradation mechanisms of polymers including aromatic polyesters (325). Thermal analysis of PS, poly-p-methylstyrene and poly-a-methylstyrene was carried out using evolved-gas IR analysis (302). 

Carbon fibers are special reinforcement types having a carbon content of 92-99 wt%. They are prepared by controlled pyrolysis of organic materials in fibrous forms at temperatures ranging from 1,000-3,000°C. 

The use is described of a process involving both hydrolysis and pyrolysis to recover caprolactam from nylon 6 used in carpet fibres. By means of precise temperature control and the use of a catalyst, nylon 6 can be isolated from the PP backing. The process has been developed by the National Renewable Resource Laboratory, and interest has been shown by AlliedSignal who are considering a cooperative research and development project. 

The pyrolysis of the plastics was carried out in a semi-batch reactor which was made of cylindrical stainless steel tube with 80mm in internal diameter and 135mm in height. A schematic diagram of the experimental apparatus is shown in Fig. 1, which includes the main reactor, temperature controller, agitator, condenser and analyzers. 

Fig. 6.4 Simple diagram of pyrolysis. 1 Stainless steel tube, 2 electrical heater, 3 temperature control monitor, 4 nitrogen pressure control monitor, 3 product exit valve, 6 condenser, 7 oily products collecting vessel, 8 nitrogen tube...

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... 

Pyrolysis GC-MS Analysis. Flash pyrolysis was performed by using a pyroprobe 100 (Chemical Data Systems) temperature-control system. Samples were pyrolyzed from 150 to 750 °C with a temperature program of 20 °C/ms and a final hold for 20 s. After pyrolysis, the fragments were separated on a 25-m CP WAX 57 fused silica capillary column (temperature program 25-220 °C at 3 °C/min), followed by MS on a R 10-10 C (Ribermag, Rueil-Malmaison, France) operated at 70 eV and scanned from 20 to 400 m/z. 

The kinetics of these pyrolysis reactions were followed by several complementary methods under conditions as close to the product studies as possible. The most frequently-used ampule technique14 17) with gc analysis of 5 and the scavenger technique, with chloranil or Koelsch radical as scavenger 18), for very labile compounds 5 were complemented by the DSC method, in which the heat flow under conditions of linear temperature increase is analysed. It proved to be a particularly convenient and reliable technique 18- 21). Rates were followed over a temperature span of at least 40 °C with temperature control of 0.1-0.2 °C. All rate data and activation parameters were subjected to a thorough statistical analysis including statistical weights of errors. The maximum statistical errors in k were 3%, in AH 1 kcal mol-1 in AS 513 e.u. and in AG (at the temperature of measurement) g0.5 kcal mol-1. 

Fig. 3.2 Setup of the spray pyrolysis system (1) temperature controller (2) peristaltic pump (3) temperature switch (4) chronometer (effective spraying and total time) (5) spray nozzle (6) motor for lateral and circular displacement (7) heating chamber (8) heating plate (9) lateral displacement support (10) generator (11) spray solution (12) carrier gas (N2) (13) connection to thermocouples (14) transmission gear (15) rotating system (16) flowmeter for the carrier gas (N2) (after Correa-Lozano et al. 1996)...

It was first produced in the early 1960s by The General Electric Company, UK, by using cellulose as a substrate. Present techniques of preparation of glassy carbon utilize such organic substrates as phenolic resins and involve controlled pyrolysis in inert atmosphere at temperatures ranging between 1000 and 3000 °C. 

Carefully controlled pyrolysis reaction temperature of around 500°C in the vapor phase, with short vapor residence times of typically less than 2 seconds... 

This procedure involves the pyrolysis of gas molecules with high content in carbon at elevated temperatures in the presence of catalyst [10, 25]. There are two basic protocols, in one of them, called supported growth process (the most used), the catalyst is prepared and deposited on a support medium, which is inserted into a flow apparatus (a tube at atmospheric pressure in a temperature controlled furnace) and exposed to elevated temperatures, usually 500-1100 °C for a given time. In the other protocol, called floating-catalyst growth, the catalyst and the... 

For the processes of different reactor types, kiln and retort pyrolysis processes are characterized by a relatively low capital investment. However, they suffer from unfavorable economics, due to the high processing costs compared with the value of the oil product obtained. Also, the characteristics of this process are relatively long residence times of waste in the reactor, poor temperature control due to large temperature gradients across their internal dimensions, fouling walls of the reactor by carbon residue and low liquid product quahty due to the production of a diverse number of pyrolysis products. 

The influence of the applied reaction conditions (temperatme, residence time, concentrations of reactants and products) on the product spectra obtained from pyrolysis of different plastic wastes could be estimated under the hypothesis of thermodynamic equilibrium, as shown by Westerhout et al. [43]. They evaluated the maximum achievable yield of valuable products during the pyrolysis of PE and PP, with the validation of experiments carried out under conditions of controlled temperatme and residence time. In large-scale reactors the residence time and temperature control are difficult and certainly... 

Figure 27.3 Rotary kiln pyrolyzer [2], 1 thermometer 2 bearing 3 gear transmission 4 electric furnace 5 rotary kiln 6 temperature controller 7 seal 8 two-step condenser 9 filter 10 total flowmeter 11 computer 12 gas sampler 13 feed and discharge opening 14 adjustable-speed motor. (Adapted from Shah, N., Rockwell, J. and Huffman, G.P., Conversion of Waste Plasticto Oil Direct Liquefaction versus Pyrolysis and Hydroprocessing, Energy Fuels, 13, 832-838 (1999))...

Pyrolysis Equipment and Procedure. The decant oil samples were pyrolyzed using a horizontal tube furnace equipped with an electronic temperature controller. The samples (1-2 g) were weighed into stainless steel tubes (6 mm o.d., 200 mm long), which were then flushed with nitrogen and sealed with Swagelok end caps. It was important that the sample holder be capable of complete disassembly to facilitate the recovery of the products of pyrolysis, which were largely viscous tars and coke. It had been found previously with a more elaborate flowthrough reactor system, that not all the carbonaceous reaction products could be recovered readily. 

Carbon molecular sieve membranes have been prepared on porous supports by controlled pyrolysis. For example, Chen and Yang [1994] prepar carbon molecular sieve membranes on porous graphite supports by coating a layer of polyfurfuryl alcohol followed by conu-olled pyrolysis with a Hnal temperature of 50O C. The procedure can be repeated to deposit a desired thickness of the carbon membrane. The choice of a graphite support is partially based on the consideration of the compatibility in thermal expansion between the carbon and the support. 

Temperature-programmed pyrolysis A pyrolysis in which the sample is heated at a controlled rate over a range of temperatures during which pyrolysis occurs. 

The reaction temperature was monitored with a thermocouple connected to a temperature controller that regulates the temperature of the heating system. The total pyrolysis time was defined here as the length of time. The glass reactor is inside the... 

The pyrolysis unit consisted of an insulated 316 stainless steel preheater tube (1.3 cm i.d. X 50 cm length) which extended 1 in. into a 316 stainless steel fixed bed tubular reactor (2.5 cm i.d. x 46 cm length), which was heated by a cylindrical block heater. Two type J (iron-constantan) thermocouple probes were used to both monitor the internal catalyst bed temperature and maintain a consistent reactor wall temperature in combination with a temperature controller, A syringe pump, condenser, vacuum adapter, receiving flask, nitrogen cylinder, and gas collection system were connected as shown in Fig uTe 2. The reactor midsection was packed with 40 g of activated alumina, which was held in place by a circular stainless steel screen. The preheater and reactor were operated at 180-190 and 450 C, respectively. The entire process remained at normal atmospheric pressure throughout the mn. 

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