Reactions acetone, cracking

Acetone cracks to ketene, and may then be converted to anhydride by reaction with acetic acid. This process consumes somewhat less energy and is a popular subject for chemical engineering problems (24,25). The cost of acetone works against widespread appHcation of this process, however. 

As in the acetaldehyde process, this can be carried out commercially in either a single-step or a two-step process. The latter is economically more favourable because a propylene/propane mixture (made by petroleum cracking) can be directly used as the feedstock. Propane behaves like an inert gas and does not participate in the reaction. Acetone is separated from lower and higher boiling compounds in a two-step distillation. 

Figure 5 Acetone cracking. Determination of the order of the reaction at 750°C (from Froment et al. (5,6]).

Pure acetone is fed into an adiabatic PFR at a mass flow rate of 7.85 kg/h. The inlet temperature and pressure of the feed stream is 760°C and 162 kPa (1.6 atm), respectively. In a vapor-phase reaction, acetone (CH3COCH3) is cracked to ketene (CHjCO) and methane (CH4). The following reaction takes place ... 

Figure 14.8a shows a simplified flowsheet for the manufacture of acetic anhydride as presented by Jeffries. Acetone feed is cracked in a furnace to ketene and the byproduct methane. The methane is used as furnace fuel. A second reactor forms acetic anhydride by the reaction between ketene from the first reaction and acetic acid. 

To 450 cc. of concentrated hydrochloric acid (sp. gr. 1.19) and 500 cc. of water in a 4-I. (i-gal.) earthenware crock equipped with an efficient stirrer is added 143 g. (1 mole) of /3-naphthyla-mine. The suspension of the amine hydrochloride is cooled by the addition of 500 g. of cracked ice. When the temperature reaches 5° solid sodium nitrite (about 69 g.) is added until starch-iodide paper shows an excess. During the diazotization about 600 g. of cracked ice is introduced at such a rate as to keep the temperature at 50. The cold solution of the diazonium salt is filtered to remove a small amount of precipitate and returned to the crock. A solution of 271 g. (1 mole) of mercuric chloride in 300 cc. of concentrated hydrochloric acid is mixed with 300 g. of ice and added slowly to the rapidly stirred solution. A heavy yellow solid separates. Stirring is continued for one-half hour to secure complete reaction. The yellow addition compound of /3-naphthalene diazonium chloride and mercuric chloride is collected on a 20-cm. Buchner funnel, sucked as dry as possible, and then washed with two 400-cc. portions of water and two 150-cc. portions of acetone (Note 1). The... 

Our specific example involves the vapor-phase cracking of acetone into ketone and methane, described by the endothermic reaction... 

P8-23b The vapor-phase cracking of acetone is to be carried out adiabatically in a bank cf 10001 -in. schedule 40 tubes 10 m in length. The molar feed rate of acetone is 6000 kg/h at a pressure of 500 kPa. The maximum feed temperature is 1050K, Nitrogen is to be fed together with the acetone to provide the sensible heafof reaction. Determine the conversion as a function of nitrogen feed rate (in terms of ) for (a) Fixed total molar flowrate. 

Pilot plant studies give the following relationship between x the conversion, y the total moles present, and vv the fraction of the acetone that is cracked in the main reaction ... 

The reaction pattern includes the formation of PO, its consecutive isomerization to propanal, acetone and ally alcohol on acidic sites and combustion [43aj. Propanal and acrolein are also primary products. The formation of lower alkanes, alkenes, acetaldehyde and methanol results from cracking and oxidative C—C bond cleavage of propene and products. Additional side-reactions may occur in the gas phase, including radical-type oxidation of propene to acrolein, hexadiene and other byproducts. Alkyl dioxanes and alkyl dioxolanes may form via dimerization reactions of PO on acidic catalysts. Indeed, major by-products are heavy compounds that... 

To a solution of 4.0 g of 1,4-naphthoquinone in 800 mL (31.6 x 10 M) ethanol/triethyl-amine (50 50) in a pyrex tube, 0.8 g of freshly cracked cyclopentadiene (15.1 x 10" M) was added and the reaction mixture was purged with a slow stream of nitrogen for 10 min. Above solution was irradiated at 300 nm in a Rayonet photochemical reactor with constant stirring and cooling at room temperature for 6 h. Progress of the reaction was monitored by TLC and GC, until more than 95% of the dienophile is consumed. After removal of the solvent and triethylamine under reduced pressure, the residue was chromatographed over silica gel (60-120 mesh). Elution with 5% acetone/hexane gave 2.44 g (43%) of 3.3, mp 160 °C. 

Desulfurization of petroleum feedstock (FBR), catalytic cracking (MBR or FI BR), hydrodewaxing (FBR), steam reforming of methane or naphtha (FBR), water-gas shift (CO conversion) reaction (FBR-A), ammonia synthesis (FBR-A), methanol from synthesis gas (FBR), oxidation of sulfur dioxide (FBR-A), isomerization of xylenes (FBR-A), catalytic reforming of naphtha (FBR-A), reduction of nitrobenzene to aniline (FBR), butadiene from n-butanes (FBR-A), ethylbenzene by alkylation of benzene (FBR), dehydrogenation of ethylbenzene to styrene (FBR), methyl ethyl ketone from sec-butyl alcohol (by dehydrogenation) (FBR), formaldehyde from methanol (FBR), disproportionation of toluene (FBR-A), dehydration of ethanol (FBR-A), dimethylaniline from aniline and methanol (FBR), vinyl chloride from acetone (FBR), vinyl acetate from acetylene and acetic acid (FBR), phosgene from carbon monoxide (FBR), dichloroethane by oxichlorination of ethylene (FBR), oxidation of ethylene to ethylene oxide (FBR), oxidation of benzene to maleic anhydride (FBR), oxidation of toluene to benzaldehyde (FBR), phthalic anhydride from o-xylene (FBR), furane from butadiene (FBR), acrylonitrile by ammoxidation of propylene (FI BR)... 

When cumene hydroperoxide is heated to cumene cracking temperatures, at least partial decomposition probably occurs. Thus, it is desirable to measure the inhibitor action of the decomposition products of cumene hydroperoxide. Some low-temperature thermal decomposition products which were identified (by chemical and mass spectroscopic analyses) are acetophenone, phenyl-dimethyl-carbinol, a-methylstyrene, phenol, acetone, and methyl alcohol. Kharasch, Fono, and Nudenberg (7) obtained similar results. According to them, the chief decomposition products at 158° are acetophenone and phenyl-dimethyl-carbinol, with acetophenone becoming relatively more important at higher temperatures. Since the temperature used for the cracking reaction is above 300°, acetophenone is probably the most important decomposition product. The equilibrium constant for the adsorption of cumene hydroperoxide and some of the individual decomposition products on catalytic sites are included in Table I. 

Acetic acid is known to undergo a vapor-phase ketonization reaction with formation of acetone on Brpnsted acids in general, and on proton-zeolites in particular. On large-pore zeolites in their proton form, the ketonization reaction is followed by acid-catalysed self-condensation amounting to mesitylene, mesityl oxide and phorone as main products [1], the chemistry being essentially identical to that in mineral acids. In H-pentasil zeolites with suitable acid site density, phorone isomerises to isophorone, which is cracked to yield 2,4-xylenol [1]. With propionic acid a similar chemistry occurs, but the formation of phenolics is severely suppressed by transition-state shape-selectivity effects... 

At high-temperature conditions, the product distributions of typical decar-boxylative and aldol condensations vary with temperature, time on stream, and catalyst age. Several ketone isomers can be produced. With acetic acid, e.g., C5-C7 (e.g., methylhexanone, pentan-2-one, 3,3 -dimethylbutan-2-one) ketones and alkylphenols arise from acetone aldolization. An important cyclic product in low temperature acetone aldolization is isophorone (2-cyclohexen-l-one, 3,5,5 -trimethyl), formed by the aldol condensation of acetone with mesityl oxide, followed by 1,6-Michael addition. In reactions with acetic acid, we have observed 2-cyclohexen-l-one, 3,5-dimethyl, which is probably a cracking product of isophorone, and small amounts of isophorone itself. Cracking to produce... 

When submitted to thermal cracking conditions acetone decomposes according to the overall reaction ... 

Polyphosphoric acid functions as a catalyst in the formation of low-molecular-weight polymers up to C,2 (12.260), and it is also used to promote alkylation reactions such as (12.261) from which phenol and acetone can be derived. Some dehydrogenation reactions proceed at lower temperatures, and more efficiently, in the presence of polyphosphoric acid, than they do at the higher temperature and pressure otherwise used in cracking (12.262). 

Four-membered Rings. The ratio of cracking to geometric isomerization for cis-1,2-diphenylcyclobutane (Scheme 50) is 2.0 0.3 thermally, 7.1 0.7 on direct irradiation, and 2.6 0.2 on acetone-sensitized photolysis, indicating that there may be a significant concerted component to the cycloreversion reaction in the singlet excited state. ... 

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