Pyrolysis - liquid trapping system

The pyrolysis-liquid trapping system used in this work is illustrated in Figure 1.11. 

Figure 1.11 Setup of pyrolysis-liquid-trapped system (1) pyroprobe, (2) pyroprobe interface, (3) helium carrier gas inlet, (4) latex sample, (5) output needle, and (6) liquid collection vial. Reprinted with permission from F.C-Y, Wang, B. Gerhart and C.G. Smith, Analytical Chemistry, 199S, 67, 20, 3681. 1995, American...

Volatile room temperature condensibles pyrolysis products were collected at cold parts within the reactor and in a collecting system made of a liquid trap followed by a Cambridge filter. The liquid trap contained inhibitor free tctrahydrofiiran (THF) at O C. The filter and the cold parts of reactor were washed with inhibitor free THF. Dry tars were prepared by evaporating the solvent in a vacuum oven at about 45°C. 

It is now clearly demonstrated through the use of free radical traps that all organic liquids will undergo cavitation and generate bond homolysis, if the ambient temperature is sufficiently low (i.e., in order to reduce the solvent system s vapor pressure) (89,90,161,162). The sonolysis of alkanes is quite similar to very high temperature pyrolysis, yielding the products expected (H2, CH4, 1-alkenes, and acetylene) from the well-understood Rice radical chain mechanism (89). Other recent reports compare the sonolysis and pyrolysis of biacetyl (which gives primarily acetone) (163) and the sonolysis and radiolysis of menthone (164). Nonaqueous chemistry can be complex, however, as in the tarry polymerization of several substituted benzenes (165). 

In order to simulate the condensing system of an industrial vacuum pyrolysis plant which consists of two condensing packed towers continuously operating, the liquids collected in each trap were mixed and then evaporated at 45 "C during half an hour in a rota-vapour (Biichi, RE 111). The heavy fraction which remained in the flask corresponds to the oil from the first condensing tower and is called bio-oil , while the evaporated fraction which consists of water and light organic compounds corresponds to the aqueous phase of the second tower and is called "aqueous phase . 

The solid is placed in a large sublimation apparatus with a high capaci ty cold trap. Evacuation of the system results in collection of a substantial amount of water and some organic liquid in the trap. The organic material, which contains a small amount of codistilled product, is extracted with ht2C), concentrated, and returned to the sublimer. The residue of diisopropylethanediol is sublimed at 60-80 "C/0.1 mbar, yield 100 g [85 % based on estimated diisopropyldioxolane from pyrolysis, 62 % based on (4/f.5/f)-4,5-bis(l-ace-toxy-l-methylethyl)-2,2-dimethyl-l,3-dioxolane, 41-47% based on tartaric acid] mp 74 76 C [a] 5 + 1.3 (c = 2.7. toluene) [2] -3.78 (c = 4.2, CH3OH). 

To a 5-mL flask with a capillary inlet attached to a source of dry nitrogen, was added 4.72 g of the Diels-Alder cycloadduct from cyclooctatriene and dimethyl acetylenedicarboxylate. The flask was connected to a 25-cm tube, which served as an air-cooled condenser, and which led to a trap cooled with liquid nitrogen. The system was evacuated at 100 mmHg, and the flask was heated in a bath at 200° C for 20 min. The flask was cooled, and nitrogen was admitted. The trap contained 0.97 g cyclobutene (95%), which was solid at the temperature of liquid nitrogen and liquefied when placed in a dry ice bath at —78°C. The residue from the pyrolysis of cycloadduct was shown to be dimethyl phthalate by comparing its infrared spectrum with the spectrum of an authentic sample and by saponification to phthalic acid, isolated by sublimation as phthalic anhydride. 

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