Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/11—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by reactions increasing the number of carbon atoms
  • C07C37/14—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by reactions increasing the number of carbon atoms by addition reactions, i.e. reactions involving at least one carbon-to-carbon unsaturated bond

Definitions

• This disclosure relates to the synthesis of cumylphenols and particularly to the synthesis of p-cumylphenol.
• alpha-methylstyrene originates as a by-product of the phenol production process, and thus contains numerous other components such as alkylbenzenes, predominantly cumene.
• the alpha-methylstyrene is isolated by distillation or other costly means.
• the cost of the purified alpha-methylstyrene adds to the cost of producing cumylphenols. There accordingly remains a need in the art for selective, economical processes to produce cumylphenol, and especially para-cumylphenol.
• Figure 1 is a graph showing reaction selectivity for para-cumylphenol versus weight percent of cumene in the total feed.
• a method of preparing cumylphenol, particularly p-cumylphenol comprises reacting phenol and alpha-methylstyrene in the presence of an acid catalyst and an alkylbenzene, preferably cumene, to form a mixture comprising cumylphenol, wherein the alkylbenzene is present at about 1 weight percent to about 90 weight percent based on the weight of the total reaction mixture. It has been unexpectedly found that the presence of an alkylbenzene in the production of cumylphenol increases the selectivity of the reaction to favor the formation of cumylphenol, particularly para- cumylphenol.
• Phenol, alpha-methylstyrene (AMS), and a suitable alkylbenzene can be individually obtained from market sources.
• phenol and by-product alpha-methylstyrene are also readily available from the production of phenol from cumene, either separately or in the form of a mixture.
• alpha-methylstyrene is produced separately as a by-product from phenol production, it also generally contains an alkylbenzene such as cumene, in amounts of about 5 weight percent to about 90 weight percent of alkylbenzene based the total weight of alpha-methylstyrene and alkylbenzene.
• the alpha-methylstyreneby-product stream from the phenol production process is used directly to produce cumylphenols, without intermediate purification. This allows significant cost savings because there is no need to purify the alpha-methylstyrene (by distillation, e.g.,) prior to use.
• Suitable alkyl benzenes comprise a phenyl ring having from one to five saturated alkyl substituents, wherein the alkyl substiuents have 1 to about 12 carbon atoms.
• a preferred alkylbenzene is cumene.
• the amount of alkylbenzene present in the reaction is about 1% to about 90%, preferably about 20% to about 65%>, and most preferably about 35% to about 55% weight percent, based on the total weight of the reaction mixture.
• the phenol is advantageously present in excess relative to the alpha-methylstyrene.
• a suitable excess may be readily determined by one of ordinary skill in the art, depending on reactivity of the starting materials and catalyst and reaction conditions, e.g., temperature, time of contact, and the like.
• a suitable excess generally is about 2 to about 15 molar equivalents of phenol to one molar equivalent of alpha-methylstyrene.
• a preferred excess is about 3 to about 13, and a more preferred excess is about 5 to about 11.5 molar equivalents of phenol relative to one molar equivalent of alpha-methylstyrene.
• Suitable acid catalysts are known in the art.
• a solid acid catalyst is preferred to avoid unnecessary separation steps or acid recovery steps; however, homogeneous catalyst such as sulfuric acid, methane sulfonic acid and p-toluene sulfonic acid (PTSA) can be employed.
• PTSA p-toluene sulfonic acid
• Examples of solid acid catalyst include cation exchange resins, acid zeolites and acid aluminas.
• Exemplary solid acid catalyst systems are acidic cation exchange resins, which are generally well known, as are methods of their preparation. Strong acid ion exchange resins, such as those resins or polymers having a plurality of pendant sulfonic acid groups are preferred.
• Examples include sulfonated polystyrene or poly(styrenedivinylbenzene) copolymer and sulfonated phenolformaldehyde resins.
• sulfonated resins are commercially available in water-swollen form as gellular and macro-reticular types.
• Specific examples of commercially available resins are Amberlite® IR-120H, Amberlyst® 15, Amberlyst® 31, Dowex® 50-X-4, Dowex® MSC-1H, and Duolite® c-291. Further examples of such ion exchange resins, as well as methods for preparing such ion exchangers, are described in U.S. Pat. No. 3,037,052.
• the exchange capacity of the acidic resin is preferably at least 2.0 milliequivalents of protons per gram (meq H + /g) of dry resin, with exchange capacities in the range of from about 3.0 to about 5.5 meq H + /g of dry resin particularly preferred.
• One preferred catalyst is the Amberlyst® types, which comprise styrene cross-linked with a monomer such as divinylbenzene or the like, and having pendant sulfonic acid groups attached to the aromatic nucleus of the styrene moiety.
• Reaction conditions are readily determined by one of ordinary skill in the art, depending on factors such as type of starting material, length of contact, activity of the catalyst, amount of catalyst, and the like.
• the reaction is typically operated at inlet temperatures of about 40 to about 100°C, preferably about 45 to about 90°C, and more preferably about 50 to about 70°C.
• Reaction pressure is typically about 0.1 to about 0.7 MegaPascal (MPa) (about 14.7 pounds per square inch (psia) to about 100 psia).
• the method may be operated continuously or batch-wise.
• the feed rate in the continuous method as measured in weighted hourly space velocity (whsv), can vary from about 0.1 to about 12.0, preferably about 0.2 to about 6.0 pounds feed per hour per pound of dry catalyst. It is hypothesized that the production rate is dependent upon the viscosity of the reaction mass and that the presence of an alkylbenzene, especially cumene, in the feed stream of the reactor decreases the viscosity of the feed stream, lowering the pressure drop across the reactor and allowing for the reaction to be run at higher throughputs than reactions not containing an alkylbenzene.
• whsv weighted hourly space velocity
• the reaction mixture may contain unreacted phenol, alpha-methylstyrene, alkylbenzene such as cumene, para-cumylphenol (PCP), ortho- cumylphenol (OCP), and by-products such as di cumylphenol, dimers of alpha- methylstyrene such as trimethylphenylindane (TMPI), and other components.
• Isolation of the desired cumylphenol may be performed by methods well known in the art to purify cumylphenols, such as distillation.
• a preferred method of isolation comprises passing the reaction mixture through an anionic bed to remove any acid catalyst that may be present.
• the reaction mixture is then passed through a first distillation column operating under reduced pressure to remove any cumene and phenol that is present. The cumene and phenol may be recycled.
• the reaction mixture is then carried to a second distillation column operating under reduced pressure, generally about 20-40 mm Hga and an elevated temperature, typically about 170-225 °C wherein o-cumylphenol and TMPI are removed.
• the reaction mixture then proceeds to a third distillation column operating under reduced pressure, typically about 20-40 mm Hga and an elevated temperature, typically about 210-225 °C wherein the p-cumylphenol is separated from dicumylphenol.
• Example 2 was run according to the method of Comparative Example 1, with the substitution of crude alpha-methylstyrene for the pure alpha-methylstyrene.
• the crude alpha-methylstyrene was obtained from a phenol production plant.
• the crude alpha-methylstyrene contained about 20 weight percent of alpha-methylstyrene and about 78 weight percent of cumene based upon the total weight of the crude mixture.
• the selectivity of the reaction for p-cumyl phenol was 85.1%.
• Examples 3-7 were run according to the method of Comparative Example 1, with the substitution of a synthetic mixture of cumene and alpha- methylstyrene for the pure alpha-methylstyrene.
• the cumene was present at 15, 30, 45, 60, and 75 weight percent based on the weight of the total reaction mixture. Results are shown in Figure 1.
• the selectivity for the desired PCP is a function of the weight percent of cumene in the reaction feed.
• a surprising result was that an improved selectivity of the reaction was observed with cumene addition as compared with the reaction without cumene.
• An optimum selectivity resulted at the intermediate concentration of cumene and phenol.
• This improved selectivity is in addition to the benefit obtained from not having to purify the alpha-methylstyrene before utilizing it to produce cumylphenols, thus saving capital and operating costs.
• cumene reduces the viscosity of the reaction mixture enabling higher throughputs in fixed bed reactors.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2002
  • 2002-02-14 US US09/683,786 patent/US6448453B1/en not_active Expired - Lifetime
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