THERMAL RECYCLING

Another example of this rearrangement has been used to prepare 1,2,3-triazole 146 from furazanic phenylhydrazone 147 (Scheme 84) [93JCS(P1)2491]. Interestingly, furoxanic Z-phenylhydrazones 150 underwent thermal recyclization to 1,2,3-triazole A-oxides 152, evidently through intermediate 151. Treatment of the hydrazone 150 with rerr-BuOK leads to the nitromethyl derivative 149 [OOOMIl] (Scheme 84). Lead tetraacetate oxidation of 147 with subsequent Lewis acid treatment of the initially formed intermediate afforded indazole 148 (Scheme 84) (85JHC29). 

The thermal recyclization of 4,4 -bis(acetamido)-3,3 -azofuroxan 195 to (nitrotriazol-2-yl) furoxan 196 has been shown to involve two consecutive MHR (99MC17) (Scheme 128). Intramolecular nucleophilic attack initiated the process. 

This paper provides a detailed overview of the current plastics waste management situation in Japan. It discusses material, chemical, and thermal recycling, and incineration versus landfill. It also provides a flow sheet showing recycling and the treatment/disposal of plastics waste in Japan in 1991. Conclusions are drawn, and the outlook for the future is considered. 5 refs. 

Paper, Film Foil Converter 68,No.7, July 1994,p.63/4 THERMAL RECYCLING OF PLASTICS GAINING POPULARITY IN JAPAN... 

Thermal recycling of plastics is becoming a more popular option in Japan, largely because of a lack of landfill sites, and also because of the materials potential as an untapped source of energy. The article supplies brief details of the advantages of thermal recycling. 

Thermal recyclization of the 3-diazenofuroxanyl unit to form the 4-nitro-l,2,3-triazole fragment has been found in noncondensed 1,2,5-oxadiazole 2-oxide derivatives (3,3 -azofuroxans) with acetamido substituents in the 4,4 -posi-tions <1999MC17>. 

In 2000, NEC developed an epoxy resin with what it describes as a fire-retardant structure that avoids the need for either TBBA or phosphorus-based flame retardants in circuit boards. The new resin contains a metal hydroxide retardant. The company claims the new board is almost totally free of pollutants, and is easy to process and thermally recycle. By also integrating flame retardant properties within the board, use of the metal hydroxide is minimised, while offering good electrical properties, higher heat resistance and improved processing characteristics. ... 

Epoxide 96 was prepared such that photolytic conversion to the carbonyl ylide could be followed by an intramolecular cycloaddition with the tethered pendant olefin. However, photolysis of epoxide 96 led only to the formation of the regio-isomer 97 and the aldehyde 98 with no evidence of the corresponding cycloadduct. It was presumed that 97 arose from the ylide by thermal recyclization to the epoxide while 98 could form through the loss of a carbene from the ylide. The failure of the tethered alkene to undergo cycloaddition may have resulted from a poor trajectory for the cycloaddition. An extended analogue (99) allowed greater flexibility for the dipolarophile to adopt any number of conformations. Photolysis of epoxide 99 did lead to formation of the macrocyclic adduct 100, albeit in modest yields. 

T0604 Philip Environmental Services Corporation, Thermal Recycling System... 

T0604 Philip Environmental Services Corporation, Thermal Recycling System T0606 PHYTOKinetics, Inc., Phytoremediation T0607 Phytoremediation—General... 

The thermal recycling system (TRS) is a thermal desorption unit designed for the on-site, ex situ remediation of mercury from contaminated soils. The system volatilizes and then condenses mercury for recovery. The TRS processes contaminants in a nonreactive atmosphere. It uses indirect heat sources to desorb contaminants and recovers 90% of the contaminants. 

The plasma energy recycle and conversion (PERC) process is an indirectly heated ex situ thermal recycling and conversion technology. According to the vendor, it treats hazardous waste, mixed radioactive waste, medical waste, municipal solid waste, radioactive waste, environmental restoration wastes, and incinerator ash in gaseous, hquid, slurry, or solid form. The technology uses an induction-coupled plasma (ICP) torch as its heat source coupled to a reaction chamber system to destroy hazardous materials. 

The principle of thermal recycling is also used in reactors with a boiling layer, in which the heat from the hot region of the reactor is transported to the cold region by circulating solid particles suspended in the gas flow.15 Methods of the theory of chemical reactor regulation have been successfully used in other sciences as well. We note the model of Belousov-Zhabotinskii, proposed for the description of heart disease, of spasmatic contractions of the cardiac muscle. 

Metallocene catalysts supported on SiC>2 are practically free of chlorine. This could be an advantage from an ecological standpoint when the chemical or thermal recycling of polymeric products reaches a large scale [211]. 

A regional integrated recycling system covering nine countries in Asia, with a centralised recycling centre in Thailand, was established and launched in December 2004. Nearly 100°/o recycling (material and thermal recycling) is achieved while four hazardous parts are separated and sent to Japan for proper treatment. 

Utilization of plutonium in early research and commercial orders to fabricate thermal recycle and fast breeder fuels did not coincide in timing with Pu availability from different sources. The plutonium comes mainly from high-exposure light-water reactor fuel reprocessing extended storage of this Pu as a nitrate solution leads to 241 contents up to 3%. For hands-on operation with this material it is necessary to reduce the Am content to about 0.5%. It was also necessary to minimize the liquid waste streams from the plant. In designing a technical-scale process, it was... 

Thermal recyclization of the 4,4 -bis(acetamido)-3,3 -azofuroxan leads to 4-acetamido-3-(5-acetamido-4-nitro-l,2,3-triazol-2-yl)furoxan [558], This transformation is probably initiated by the nucleophilic attack of an amide anion or amine on the nitrogen atom of the furoxan. The oxidation of the latter results in two isomers 4-nitro-3- and 3-nitro-4-(4,5-dinitro-l,2,3-triazol-2-yl)furoxan in the 8 1 ratio, which were separated by chromatography on Si02 (Scheme 102). 

Chemical reactors are inherently nonlinear in character. This is primarily due to the exponential relationship between reaction rate and temperature but can also stem from nonlinear rate expressions such as Eqs. (4.10) and (4.11). One implication of this nonlinearity for control is the change in process gain with operating conditions. A control loop tuned for one set of conditions can easily go unstable at another operating point. Related to this phenomenon is the possibility of open-loop instability and multiple steady states that can exist when there is material and/or thermal recycle in the reactor. It is essential for the control engineer to understand the implications of nonlinearities and what can be done about them from a control standpoint as well as from a process design standpoint. 

J. M. Arandes, J. Erena, M. J. Azkoiti, M. Olazar, and J. Bilbao, Thermal recycling of polystyrene and polystyrene - butadiene dissolved in a light cycle oil,. 1. Anal Appl Pyrol, 70, 747 (2003). 

W. Kaminsky, Thermal recycling of polymers, J. Anal. Appl. Pyrolysis, 8, 439-448, (1985). 

As all the pyrolysis and distillation plant outputs are mechanically or thermally recycled except for hydrochloric acid, the total recycle ratio in the pyrolysis process is calcnlated as 99.0%. 

An early example having potential commercial importance comes from tlie Trost laboratory s synthesis of vitamin D analogs (Scheme 6-23) [51], Their combination of vinyl bromide 129 and alkyne 130 to form triene 131 led to a concise and efficient synthesis of (-i-)-alphacalcidiol (134). In this reaction, vinyl bromide 129 participates in a bimolecular Heck reaction with alkyne 130 and the resulting alkenylpalladium intermediate 133 undergoes subsequent intramolecular Heck reaction with the pendant terminal alkene to provide 131. Under the reaction conditions, some of the desired product undergoes a [1,7]-hydrogen shift to yield 132. After thermal recycling of the minor component, a remarkable 76% yield of 131 was obtained. 

This chapter describes post-consumer plastic recycling, where recycling refers to plastic material and may involve material recycling, chemical recycling or thermal recycling. 

Thermal recycling involves, in most cases, the simple burning of collected material and the utilization of the resultant exothermic heat. In some cases, the material may have a chemical use such as in the chemical reduction of iron oxides in a furnace. In this example, the plastic replaces coal as the reducing agent. 

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