Ethylbenzene methylphenylcarbinol

Sales demand for acetophenone is largely satisfied through distikative by-product recovery from residues produced in the Hock process for phenol (qv) manufacture. Acetophenone is produced in the Hock process by decomposition of cumene hydroperoxide. A more selective synthesis of acetophenone, by cleavage of cumene hydroperoxide over a cupric catalyst, has been patented (341). Acetophenone can also be produced by oxidizing the methylphenylcarbinol intermediate which is formed in styrene (qv) production processes using ethylbenzene oxidation, such as the ARCO and Halcon process and older technologies (342,343). 

Rhodium (2J) and ruthenium are excellent catalysts for the reduction of aromatic rings. It is with these catalysts that the best chance resides for preservation of other reducible functions (2,10,13,18,41,42,52). Rhodium (41) and ruthenium (45) each reduced methylphenylcarbinol to methylcyclohexyl-carbinol in high yield. Palladium, on the other hand, gives ethylbenzene quantitatively. Water has a powerful promoting effect, which is unique in ruthenium catalysis (36). 

Styrene is produced by the catalytic vapor phase dehydrogenation of ethylbenzene. Ethylbenzene is made by the Friedel-Crafts condensation of ethylene and benzene. Styrene is also produced by the palladium acetate-catalyzed condensation of ethylene and benzene and by the dehydration of methylphenylcarbinol obtained by the propylation of ethylbenzene. Because of the toxicity of styrene, its concentration in the atmosphere must be severely limited. 

Cobalt complexes with pyridine ligands, for example, catalyzed the oxidation of neat ethylbenzene to acetophenone in 70% conversion and 90% selectivity [35]. Mn porphyrin complex catalyzes the ethylbenzene oxidation with dioxygen to 3 14 mixture of methylphenylcarbinole and acetophenone in the presence of acetaldehyde [36]. The system CUCI2-crown ether in the presence of acetaldehyde is efficient as catalyst of oxidation of ethylbenzene, indane, and tetralin by dioxygen (70°C) into the corresponding alcohols and ketones with high TON [37]. The oxidations were established to occur via a radical pathway and not by a metal-oxo... 

The oxidation of ethylbenzene using iron-haloporphyrins in a solvent-free system under molecular oxygen at 70-110°C gives mixture of a-phenylethylhydroperoxide, methylphenylcarbinole, and acetophenone (1 1 1). The catalyst is (TPFPP=5,10,15,20-tetrakis (pentafluorophenyl) porphyrin). Ethylbenzene conversion does not more than 5%. The oxidation occurs via radical pathway [3 9]. The products of ethylbenzene oxidation with air under mild condition (T > 60°C, atmospheric pressure), catalyzed by [TPPFeJ O or [TPPMnJ O ( 0,-oxo dimeric metalloporphyrins, a,-oxo-bis(tetraphenylporphyrinato)iron (manganese)) without any additive are acetophenone and methylphenylcarbinole. The ethylbenzene oxidation is radical chain oxidation in this case also. The ketone/alcohol (mol/ mol) rations are 3.76 ([TPPMnJ O, ethylbenzene conversion - 8.08%), 2.74 ([TPPFe]20, ethylbenzene conversion - 3.73%) [40]. 

Benzaldehyde (BAL), benzyl alcohol (BZA), acetophenone (AP), methylphenylcarbinol (MPC), dimethyl phenylcarbinol (DMPC), and phenol (PhOH), as well as the RH content in cumene and ethylbenzene oxidation processes were examined by GLC [9-14,17], The overall rate of the process was determined from the rate of aceumulation of all oxidation products (toluene, ethylbenzene), or consumption of starting hydrocarbon (cumene). A correlation between RH consumption and product (P) accumulation was established A[RH] = S [P]. 

Methylphenylcarbinol is also an intermediate in the Halcon process, in which ethylbenzene is oxidized to a hydroperoxide at around 130 °C with air, then converted with propylene into propylene oxide and carbinol. The carbinol is subsequently dehydrated on a titanium catalyst at 180 to 280 °C to styrene. This process, first commercialized by Atlantic Richfield, has found large-scale application in a few isolated cases (e.g. Shell (Netherlands), Alcudia (Spain) and Nihon Oxirane (Japan)) it is only viable if there is sufficient demand for propylene oxide. 

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