Purity phenol hydrogenation

The alpha-methyl styrene can be recovered as a product or catalytically treated with hydrogen and converted back to cumene for recycling. The acetophenone has some commercial use in pharmaceuticals and at one time was used to make ethylbenzene. A high purity phenol is sometimes made by a crystallization step, since phenol freezes at about 109°F. With alpha-methyl styrene recycled, the ultimate yield is about 97%. 

In contrast to phenolic hydroxyl, benzylic hydroxyl is replaced by hydrogen very easily. In catalytic hydrogenation of aromatic aldehydes, ketones, acids and esters it is sometimes difficult to prevent the easy hydrogenolysis of the benzylic alcohols which result from the reduction of the above functions. A catalyst suitable for preventing hydrogenolysis of benzylic hydroxyl is platinized charcoal [28], Other catalysts, especially palladium on charcoal [619], palladium hydride [619], nickel [43], Raney nickel [619] and copper chromite [620], promote hydrogenolysis. In the case of chiral alcohols such as 2-phenyl-2-butanol hydrogenolysis took place with inversion over platinum and palladium, and with retention over Raney nickel (optical purities 59-66%) [619]. 

The sequence includes several synthetic steps over polymer-supported catalysts in directly coupled commercially available Omnifit glass reaction columns [41] using a Syrris Africa microreactor system [14], Thales H-Cube flow hydrogenator [32] and a microfluidic chip. The process affords the alkaloid in 90% purity after solvent evaporation, but in a moderate 40% yield. After a closer investigation it was concluded that this is due to the poor yield of 50% in the phenolic oxidation step. On condition that this is resolved with the use of a more effective supported agent, the route would provide satisfactory yields and purities of the product. 

B. Hydrogenolysis of the Phenolic Ether Biphenyl. To a solution of 10 g. (0.032 mole) of the product from Part A in 200 ml. of benzene is added 2 g. of 5% palladium-on-charcoal, and the mixture is shaken with hydrogen in a Parr apparatus at 40 p.s.i. and 35-40° for 8 hours (Note 3). The mixture is filtered, and the insoluble residue is washed with three 100-ml. portions of hot ethanol (Note 4). The filtrates are combined, and the solvent is removed by means of a rotary evaporator at 60° (12 mm.) to leave a solid residue. The product is dissolved in 100 ml. of benzene, and 100 ml. of 10% sodium hydroxide solution is added. The mixture is shaken, and the layers are separated. The aqueous layer is extracted with 100 ml. of benzene, and the original benzene layer is washed with 100 ml. of water (Note 5). The benzene solutions are combined and dried over magnesium sulfate. Removal of the benzene by distillation yields 4.0-4.7 g. (82-96%) of biphenyl as a white powder, m.p. 68-70° (Note 6). The infrared spectrum is identical with that of an authentic sample, and a purity of at least 99.5% was indicated by gas chromatography analysis. 

In CS3 (Figure 5.25), the hydrogen fresh feed is increased by about 9% from 348.5 to 380, while the recycle flow of phenol remains fixed to 220kmol/h. This control structure works well. Both the production of cyclohexanone and cyclohexa-nol is increased by about 4%, while phenol makeup increases with 8%. The purity of both products remains above 98%. A somewhat shorter transition time is obtained. The fact that hydrogen pushes the plant better than phenol is quite surprising, but it can be explained by the fact that there is no snowball effect on the gas-recycle side. 

Acetone and phenol can be recovered after the neutralization of the acidic mixture from the cleavage reactor with sodium hydroxide or phenolate solution. The neutralized mixture is then subjected to a series of distillations. Acetone is first distilled, then cumene is recovered, together with a-methylstyrene, which is either purified and marketed or hydrogenated back to cumene and recycled to the oxidation. Phenol is finally distilled with a purity up to 99.99%, suitable for the production of polycarbonate grade bisphenol A and other chemicals and polymers. 

Yields and kinetics depend on the type and number of Ti species and the crystal size of the catalyst used. Ti distribution between lattice (selective) and extra-lattice (unselective) sites is, in turn, closely linked to synthesis and characterization procedures, both of which require special thoroughness [4]. Inadequate characterization and, therefore, the impossibility of clear assessment of siting of Ti in the catalyst, is a frequent obstacle to a correct evaluation of the literature, especially early publications. These considerations are of general value, but are central to the hydroxylation of phenol where extra-framework species are a major source of hydrogen peroxide decomposition and radical chain oxidations. The hydroxylation of phenol was indeed proposed by three different groups as an additional test to assess the purity of TS-1 [2, 9, 11]. Van der Pool et al. estimated from Weisz... 

Description Cumene is oxidized (1) with air at high efficiency (-i-95%) to produce cumene hydroperoxide (CHP), which is concentrated (2) and cleaved (3) under high-yield conditions (-i-99%) to phenol and acetone in the presence of an acid catalyst. The cleavage mixture is neutralized and fractionated to produce high-purity products (4-8), suitable for all applications. AMS is hydrogenated to cumene and recycled to oxidation or optionally recovered as a pure byproduct. 

The yield and kinetics of phenol hydroxylation are strongly dependent on the purity, crystal size, and the concentration of TS-1, and on the temperature. High selectivity is directly correlated to framework titanium, whereas extra-framework titanium species initiate the decomposition of hydrogen peroxide and subsequent hydroxylation paths, which are far less selective. 

Bis-(4-hydrox5 henyl)-fluorene is commercially synthesized by the reaction of phenol with 9-fluorenone, in the same way as the synthesis of bisphenol A proceeds. Hydrogen chloride, 3-mercaptopropionic acid or methanesulfonic acid are used as catalysts. The condensation reaction of fluorenone and phenol in the presence of gaseous hydrogen chloride proceeds with sufficient speed already by 30°C. ° A high purity monomer can be obtained by a two-step purification process. In the first purification step, the crude 9,9-bis-(4-hydrox5 henyl)-fluorene is refluxed in acetonitrile and recrystallized. In the second step, the product is purified by crystallization from a toluene/isopropanol mixture. 

Although the reaction theoretically requires the molar ratio of reactants to be 2 1, an improved yield of bisphenol A is obtained if additional phenol is present the optimum molar ratio is 4 1. In a typical process, the phenol and acetone are mixed and warmed to 50 C. Hydrogen chloride (catalyst) is passed into the mixture for about 8 hours, during which period the temperature is kept below 70 C to suppress the formation of isomeric products. Bisphenol A precipitates and is filtered off and washed with toluene to remove unreacted phenol (which is recovered). The product is then recrystallized from aqueous ethanol. Since epoxy resins are of low molecular weight and because colour is not normally particularly important, the purity of bisphenol A used in resin production is not critical. Material with a p,p -isomer content of 95-98% is usually satisfactory the principal impurities in such material are o,p - and o,o -isomers. 

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