Cracking of benzene

In the cracking of benzene to acetylene over alumina- and silica-supported nickel catalysts it was observed that the selectivity of the reaction, expressed as the ethyne/ ethene ratio, was dramatically affected (from 1 9 to 9 1) by controlling the micro-wave energy input (i. e. 90% selectivity) [83]. 

For reactions that occur with different selectivities or kinetics on the induced sites, the implications are far more complex. Teichner has found that the selectivities for the isomerization of methylcyclopropane and for cracking of benzene and cyclohexadienes may be substantially different on activated silica or alumina than on the normal oxides (see above). In these cases, a separate rate expression may need to be included. Depending on the rate constants and relative kinetics, this can substantially change the reaction-rate expression. Further, differences in the activation energies may affect the contribution at different temperatures. If the reaction temperature is sufficient, the activation of the support may be able to occur during the course of the experiment. 

The purported Fischer-Tropsch alkylation of benzene catalyzed by [Mm(CO) ](M = Cr, W, Ru, Co, or Rh) in the presence of AICI3 is simply the result of a Lewis acid-catalyzed cracking of benzene since similar alkylations occur when benzene and AICI3 are heated together. It had also been reported that cobalt carbonyls in glyme solvents catalyzed the hydrogenation of CO but experiments carried out with CO now indicate that >90% of the ethanol formed is derived from the solvent. Similarly the trimethyl phosphite-enhanced formation of methane from synthesis gas in the presence of fIr4(C ))i2] f )s3(C ))i2 ] has been... 

Arosolvan process A process for the extraction of benzene and toluene from a mixture of aromatic and saturated hydrocarbons using a mixture of water and N-methylpyrrolidone. The process is used when naphtha is cracked to produce alkenes. To prevent extraction of alkenes these are saturated by hydrogenation prior to extraction. 

CeH3Me3. Liquid produced by catalytic cracking of methyl benzenes. Used to prepare trimellitic anhydride. 

Pyrolysis gasoline is a by-product of the steam cracking of hydrocarbon feeds in ethylene crackers (see Ethylene). Pyrolysis gasoline typically contains about 50—70 wt % aromatics, of which roughly 50% is benzene, 30% is toluene, and 20% is mixed xylenes (which includes EB). 

Aromatic. Aromatic feedstreams (C-8, C-9, C-10) derived from the steam cracking of petroleum distillates are composed of styrene, iadene, vinyltoluenes (eg, meta- and i ra-methylstyrene), and their respective alkylated analogues. A typical aromatic feedstream might contain 50% reactive olefins with the remainder being alkylated benzenes and higher aromatics. 

Petroleum-derived benzene is commercially produced by reforming and separation, thermal or catalytic dealkylation of toluene, and disproportionation. Benzene is also obtained from pyrolysis gasoline formed ia the steam cracking of olefins (35). 

FIG. 23-3 Temperature and composition profiles, a) Oxidation of SOp with intercooling and two cold shots, (h) Phosgene from GO and Gfi, activated carbon in 2-in tubes, water cooled, (c) Gumene from benzene and propylene, phosphoric acid on < uartz, with four quench zones, 260°G. (d) Mild thermal cracking of a heavy oil in a tubular furnace, hack pressure of 250 psig and sever heat fluxes, Btu/(fr-h), T in °F. (e) Vertical ammonia svi,ithesizer at 300 atm, with five cold shots and an internal exchanger. (/) Vertical methanol svi,ithesizer at 300 atm, Gr O -ZnO catalyst, with six cold shots totaling 10 to 20 percent of the fresh feed. To convert psi to kPa, multiply by 6.895 atm to kPa, multiply by 101.3. 

In a 4-I. wide-mouthed glass jar, fitted with a mechanical stirrer, is placed a solution of 150 g. (3 moles) of sodium cyanide (Note i) in 500 cc. of water and 318 g. (3 moles) of u.s.P. benz-aldehyde. The stirrer is started and 850 cc. of a saturated solution of sodium bisulfite (Note 2) is added to the mixture, slowly at first and then in a thm stream. The time of addition is ten to fifteen minutes. During the addition of the first half of this solution, 900 g. of cracked ice is added to the reaction mixture, a handful at a time. The layer of mandelonitrile which appears during the addition of the sulfite solution is separated from the water in a separatory funnel. The water is extracted once with about 150 cc. of benzene, the benzene is evaporated, and the residual mandelonitrile is added to the main portion. 

Raw materials for obtaining benzene, which is needed for the production of alkylbenzenes, are pyrolysis gasoline, a byproduct of the ethylene production in the steam cracking process, and coke oven gas. Reforming gasoline contains only small amounts of benzene. Large amounts of benzene are further produced by hydrodealkylation of toluene, a surplus product in industry. 

The main products of diphenylmethane (DPM) cracking were benzene and toluene. Very small amounts of polymerized by-products have been found (< 0.5%), but no cyclohexane or partially hydrogenated compounds like cyclohexylphenylmethane were detected. 

For the purposes of this illustrative example, we wish to calculate the combined and effective diffusivities of cumene in a mixture of benzene and cumene at 1 atm total pressure and 510 °C within the pores of a typical TCC (Thermofor Catalytic Cracking) catalyst bead. For our present purposes, the approximation to the combined diffusivity given by equation 12.2.8 will be sufficient because we will see that the Knudsen diffusion term is the dominant factor in determining the combined diffusivity. 

Besides methane and hydrogen, other products observed were mainly ethane, ethylene (probably due to propane cracking), propene which are shown in figure 3. Minor amounts of benzene and toluene were also found but these products could not be quantified because their slow desorption from the zeolite s channels. 

Whereas over the dual-bed catalyst system, namely Pt/Z12(80) HB(20), a significant improvement in benzene purity up to 94.60% was observed. This is ascribed due to selective cracking of naphthenes over acidic zeolite H-Beta at the bottom bed. 

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