Dehydration, phenol alkylation

Part of the benzaldehyde stream undergoes hydrogenation to benzyl alcohol (parallel to MPK —> MPC), which is returned to the dehydration reactor. Benzyl alcohol is partially consumed by phenol alkylation and other reactions over the alumina catalyst. As is also the case for BPEA, the rather low conversion leads to a significant benzyl alcohol recycle in dehydration and hydrogenation. 

Chemical Disinfectant A chemical or chemical solution capable of destroying micro-organisms through dehydration (alcohols), alkylation (aldehydes), protein denaturation (phenols), oxidation... 

For many reactions, in particular alcohol dehydrations, olefin isomerization, methylchloride synthesis, and phenol alkylations, the proton forms of zeolites are reported to be more active than alumina. However, alumina is preferably applied because of fewer byproducts and slower coking. Thus, the strong Lewis acidity and perhaps also the medium—weak Bronsted acidity of alumina provide an optimal balance between activity and stability these sites have sufficient activity while they deactivate only slowly. 

A typical phenol plant based on the cumene hydroperoxide process can be divided into two principal areas. In the reaction area, cumene, formed by alkylation of benzene and propylene, is oxidized to form cumene hydroperoxide (CHP). The cumene hydroperoxide is concentrated and cleaved to produce phenol and acetone. By-products of the oxidation reaction are acetophenone and dimethyl benzyl alcohol (DMBA). DMBA is dehydrated in the cleavage reaction to produce alpha-methylstyrene (AMS). 

Methylphenol. This phenol, commonly known as o-cresol, is produced synthetically by the gas phase alkylation of phenol with methanol using modified alumina catalysis or it may be recovered from naturally occurring petroleum streams and coal tars. Most is produced synthetically. Reaction of phenol with methanol using modified zeoHte catalysts is a concerted dehydration of the methanol and alkylation of the aromatic ring. 2-Methylphenol [95-48-7] is available in 55-gal dmms (208-L) and in bulk quantities in tank wagons and railcars. 

Reductive amination of cyclohexanone using primary and secondary aHphatic amines provides A/-alkylated cyclohexylamines. Dehydration to imine for the primary amines, to endocycHc enamine for the secondary amines is usually performed in situ prior to hydrogenation in batch processing. Alternatively, reduction of the /V-a1ky1ani1ines may be performed, as for /V,/V-dimethy1 cyclohexyl amine from /V, /V- di m e th y1 a n i1 i n e [121 -69-7] (12,13). One-step routes from phenol and the alkylamine (14) have also been practiced. 

Owing to its excellent thermal and mechanical stability and its rich chemistry, alumina is the most widely used support in catalysis. Although aluminium oxide exists in various structures, only three phases are of interest, namely the nonporous, crys-tallographically ordered a-Al203, and the porous amorphous t]- and y-Al203. The latter is also used as a catalyst by itself, for example in the production of elemental sulfur from H2S (the Claus process), the alkylation of phenol or the dehydration of formic acid. 

Cation-exchange resins are used as catalysts in the produdion of MTBE (methyl tertiary-butyl ether, 2-methoxy-2-methylpropane) and various other oxygenates and, lately, also in the dimerization of isobutene [30]. Other commercial applications of the cation-exchange resins indude dehydration of alcohols, alkylation of phenols, condensation readions, alkene hydration, purification of phenol, ester hydrolysis and other reactions [31]. The major producers of ion-exchange resins are Sybron Chemicals Incorporated [32] (Lewatit resins), Dow Chemical Company [33] (DOWEX resins), Purolite [28] (Purolite resins), and Rohm and Haas Company [27] (Amberlyst resins). 

Phenol and alkyl-substituted phenols yield dibenzofuran and alkyldiben-zofurans by catalytic dehydration-dehydrogenation over thorium or cerium oxides. This reaction can also be achieved by thermal cracking of... 

Essentially the same route is followed for the synthesis of the triphenylethylene nitromifene (8-5). The sequence starts with Friedel-Crafts acylation of the alkylation product (8-1) from phenol and 1,2-dibromoethane with the acid chloride from anisic acid (8-2). The displacement of bromine in the product (8-3) with pyrrolidine leads to the formation of the basic ether and thus (8-4). Condensation of that product with benzylmagnesium bromide gives the tertiary alcohol (8-5). This product is then treated with a mixture of nitric and acetic acids. The dehydration products from the first step almost certainly consist of a mixture of the E and Z isomers for the same reasons advanced above. The olefin undergoes nitration under reaction conditions to lead to nitromifene (8-6) as a mixture of isomers [8] the separated compounds are reported to show surprisingly equivalent agonist/antagonist activities. 

Reaction between alkoxides or arox-ides and alkyl halides (Williamson) 0-14 Reaction between alkoxides or arox-ides and inorganic esters 0-15 Alkylation of alcohols or phenols with diazo compounds 0-16 Dehydration of alcohols 0-17 Transetherification 0-19 Alkylation of alcohols with onium salts... 

AHC(18)337>. The 3-alkylbenzo[6 ]furans result from cyclodehydration of aryloxyacetones the most common dehydrating agents are sulfuric acid, phosphorus oxychloride and poly-phosphoric acid. The allyl ethers of phenols can be converted to 2-alkyl-2,3-dihydro-benzo[6]furan by heating with polyphosphoric acid, pyridine hydrochloride or magnesium chloride at 180 °C the intermediate o-allylphenol is not isolated. 

The ring closure of orf/io-substituted phenols is a route to production of benzo[6]furans on an industrial scale. The natural benzo[6 ]furan derivatives karanjin, pongapin, khellin and visnagin have been prepared via the respective o-hydroxyarylacetaldehydes, whilst an extension to the cyclization of o-hydroxybenzyl alkyl ketones has made it possible to synthesize polycyclic benzo[6]furans under the influence of demethylating and dehydrating media. Pterocarpans have been synthesized from suitable isoflavones by this route. 

The reaction apparently proceeds via dehydration of f-BuOH to generate isobutene, which reacts with phenol to form 2-isobutylphenols as anti-Markovnikov products. The hydroxy group presumably participates in the anti-Markovnikov alkylation and is further assisted by the increased water density.35... 

Alcohols and phenols are also weak bases. They can be protonated on the oxygen by strong acids. This reaction is the first step in the acid-catalyzed dehydration of alcohols to alkenes and in the conversion of alcohols to alkyl halides by reaction with hydrogen halides. Alkyl halides can also be prepared from alcohols to alkyl halides by reaction with hydrogen halides. Alkyl halides can also be prepared from alcohols by reaction with thionyl chloride or phosphorus halides. 

The procedure usually is unsuitable for tertiary alcohols since the reaction with phthalic anhydride or succinic anhydride either fails or results in dehydration of the alcohol. A few tertiary alkyl phthalates, however, have been prepared and resolved by first converting the alcohols to sodium or potassium salts and allowing these to react79 80 with phthalic anhydride. This modification has been applied successfully to dUa- and /S-santalols81 and cB-linalool.81 As already mentioned, glycols cannot be resolved by this procedure because they form polymeric esters when heated with phthalic or succinic anhydride. Phenols also usually form phthaleins or other condensation products instead of simple acid esters. 

Acid Form - Pseudoliquid Phase Behavior. Owing to a high affinity for polar molecules, large quantities of molecules such as alcohols and ether are absorbed within the bulk phase of crystalline heteropolyacids. The amounts of pyridine, methanol, and 2-propanol absorbed correspond to 50-100 times that which can be adsorbed on the surface, while nonpolar molecules like ethylene and benzene are adsorbed at the surface only. Catalytic reactions of polar molecules occiu both on the surface and in the bulk, so that the solid heteropolyacid behaves as a highly concentrated solution, called a pseudoliquid phase . The dehydration of alcohols, various conversions of methanol and dimethyl ether to hydrocarbons in gas-solid systems, and the alkylation of phenol and pinacol rearrangements can all occur in the pseudoliquid. The transient response using isotopically labeled 2-propanol provides evidence for the pseudoliquid phase behavior of H3PW12O40. This behavior influences the selectivity, for example, the aUcene/aUcane ratio, in the conversion of dimethyl ether. 

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