Pyrolysis acetone

There are many other unitary operations which are used by organic chemistry plants to manufacture synthetic solvents. These include alkoxylation (ethylene glycol), halogenation (1,1,1-trichloethane), catalytic cracking (hexane), pyrolysis (acetone and xylene), hydrodealkylation (xylene), nitration (nitrobenzene), hydrogenation (n-butanol, 1,6-hexanediol), oxidation (1,6-hexanediol), esterification (1,6-hexanediol), and many more. 

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

Acetone was originally observed about 1595 as a product of the distillation of sugar of lead (lead acetate). In the nineteenth century it was obtained by the destmctive distillation of metal acetates, wood, and carbohydrates with lime, and pyrolysis of citric acid. Its composition was determined by Liebig and Dumas in 1832. 

The production of ketene by this method has no significant environmental impact. The off-gases from the ketene furnace are either circulated to the furnace and burned to save energy or led to a flare system. The reaction can also be carried out at 350—550°C in the presence of alkaH-exchanged zeoHte catalysts (54). Small quantities of ketene are prepared by pyrolysis of acetone [67-64-1] at 500—700°C in a commercially available ketene lamp (55,56). 

Thermal Stability. The saturated C —C 2 ketones are thermally stable up to pyrolysis temperatures (500—700°C). At these high temperatures, decomposition can be controlled to produce useful ketene derivatives. Ketene itself is produced commercially by pyrolysis of acetone at temperatures just below 550°C (see Ketenes, ketene dil rs, and related substances). 

IsoxazoIidine-3,3-dicarboxylic acid, 2-methoxy-dimethyl ester reaction with bases, 6, 47 Isoxazolidine-3,5-diones synthesis, 6, 112, 113 Isoxazoli dines conformation, 6, 10 3,5-disubstituted synthesis, 6, 109 oxidation, 6, 45-46 PE spectra, 6, 5 photolysis, 6, 46 pyrolysis, 6, 46 reactions, 6, 45-47 with acetone, 6, 47 with bases, 6, 47 reduction, 6, 45 ring fission, S, 80 spectroscopy, 6, 6 synthesis, 6, 3, 108-112 thermochemistry, 6, 10 Isoxazolidin-3-ol synthesis, 6, 111 Isoxazolidin-5-oI synthesis, 6, 111... 

The 5-substituted 1,3-dioxolan-4-one 23 is readily deprotonated at the 5 position and can be alkylated with a variety of alkyl halides. The resulting products 24 decompose upon flash vacuum pyrolysis (FVP) at 600°C with loss of acetone... 

Pyrolysis of hafnium acetyl acetonate, Hf(C5H702)3, at 400-750°C or hafnium trifluoro-acetylacetonate, Hf(C5H402p3)4 at 500-550°C with helium and oxygen as carrier gases. 

The study [39] shows that similar equation is valid for adsorption of NH- and NH2-radicaIs, too. There are a lot of experimental data lending support to the validity of the proposed two-phase scheme of free radical chemisorbtion on semiconductor oxides. It is worth noting that the stationary concentration of free radicals during the experiments conducted was around 10 to 10 particles per 1 cm of gas volume, i.e. the number of particle incident on 1 cm of adsorbent surface was only 10 per second. Regarding the number of collisions of molecules of initial substance, it was around 10 for experiments with acetone photolysis or pyrolysis provided that acetone vapour pressure was 0,1 to 0,01 Torr. Thus, adsorbed radicals easily interact at moderate temperatures not only with each other but also with molecules which reduces the stationary concentration of adsorbed radicals to an even greater extent. As we know now [45] this concentration is established due to the competition between the adsorption of radicals and their interaction with each other as well as with molecules of initial substance in the adsorbed layer (ketones, hydrazines, etc.). 

Similar results have been derived in generating free radicals through pyrolysis of acetone on a platinum filament [50]. Adsorption of more complex radicals such as C2H5, C3H7, CH2C6, etc. has been studied using the same methods. The above relationship asserts satisfactorily in these cases, too. This provides the evidence for versatility of the found relationship (3.22) which can be successfully applied in the methods involving the use of sensors. 

Fig.4.5. Relative variation rate of the electric condnctivity of the sensor i as a function of the temperature of the pyrolysis filament, plotted in o - T axes (a) and Ig o - P axes (6). The temperatures in the vessel are 323 C (/) and 350 C (2), the pressure of acetone ac = 0.5 Torr.

The results on pyrolysis of acetone displayed in Fig. 4.5 are consistent with formula (4.8). Thus, variation of the concentration of free radicals near the sensor surface and, consequently, variation of the value idv/dt)tMi = o as functions of the filament temperature are governed by relation (4.8). As the acetone pressure increases, this relation fails because of fast interaction of CH3 radicals with acetone molecules. 

Emission of free radicals was observed in case of relaxation of disordered surface of selenium with adsorbed methyl radicals [18, 39] which were obtained during pyrolysis of acetone [40] over the temperature range 500 - 650 C, as well. As during pyrolysis of diethylselenide the above temperature range was chosen to ensure low probability of the brake up of C-H bond. 

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). 

Pyrolyses. A film from Au-acetone was pyrolyzed in stages up to 300°C. At intervals mass spectra were recorded, which showed the evolution of acetone (mainly) as well as other products. A similar experiment, where GC-MS was employed allowed identification of several of these minor products as CO, H20, CA, CX, C Hg, chH8 C HgO, and C H2 (probably butadiyne). Pyrolysis of adsorbid acetone may be the source of these materials. 

Reaction of HCofPfOPh), with PMMA. A 1.0g sample of PMMA and 1.0g of the cobalt compound were combined as above. After pyrolysis at 375°C for two hours the tube is noted to contain char extending over the length of the tube with a small amount of liquid present. The gases were found to contain CO, C02, hydrocarbon (probably methane), and 0.1 Og methyl methacrylate. Upon addition of acetone, 1.0g of soluble material and 0.19g of insoluble may be recovered. The infrared spectrum of the insoluble fraction is typical of char. 

Conversion data were obtained in a tubular flow reactor for the pyrolysis of acetone at 520 C and 1 atm to form ketene. The reactor was 3.3 cm ID and 80 cm long. Find a rate equation. 

---