Acetic acid, esterification

Methyl acetate from methanol and acetic acid Esterification... 

In a typical process for manufacture on a commercial scale bleached wood pulp or cotton linters are pretreated for 12 hours with 40-50% sulphuric acid and then, after drying, with acetic acid. Esterification of the treated cellulose is then carried out using a mixture of butyric acid and acetic anhydride, with a trace of sulphuric acid as catalyst. Commercial products vary extensively in the acetate/ butyrate ratios employed. 

Zu ZP, Chuang KT (1996) Kinetics of acetic acid esterification over ion exchange catalysts. Can J Chem Eng 74 493-500... 

In liquid phase reactions, the importance of the swelling properties and the related sorption capacities for the catalytic activity of ion exchangers was demonstrated. The rate coefficient of 1-butanol—acetic acid esterification [431] decreased with the degree of crosslinking in the same manner as did the water sorption capacity and the solvation coefficient of 1-butanol. A similar effect was found for the transesterification of ethyl acrylate with 1-butanol [404]. 

Pervaporation membrane reactors are not a recent discovery. The use of a PVMR was proposed in a U.S. patent dating back to 1960 [3.6]. Though the technical details on membrane preparation and experimental apparatus were rather sketchy, the basic idea was described there, namely, the use of a water permeable polymeric membrane to drive an esterification reaction to completion. A more detailed description of a PVMR can be found in a later European patent [3.7], which described the use of a flat membrane (commercial PVA or Nafion ) placed in the middle of a reactor consisting of two half-cells. The reaction studied was the acetic acid esterification reaction with ethanol. For an ethanol to acetic acid ratio of 2, liquid hourly space velocities (LHSV) in the range of 2-5, and a temperature of 90 °C complete conversion of the acetic acid was reported. The use of PVMR for this reaction shows promise for process simplification, as indicated schematically in Figure 3.2, which shows a side-by-side comparison of a conventional and a proposed PVMR plant for ethyl acetate production. 

Naproxen is prepared (13) by the acylation of 6 substituted naphthalenes by AcCI forming the 2-acetyl derivative, which is further converted to 2-naphthyl acetic acid. Esterification and alkylation of 2-naphthyl acetic acid in the prescence of H2SO4, MeOH, NaH, Mel and with NaOH gave after hydrolysis the naphthyl propionic acid. Resolution of 2-(6-methoxy-2-naphthyl) propionic (Naproxen) was readily achieved by crystallization of the cinchonidine salt. 

Also, one might expect that many met catalysts would have a very high site density, perhaps near 10 cm In 1966 Horiuti and coworkers ( ), using a method we showed ( ) is almost equivalent to the TST method, examined the reported data for 66 metal-catalyzed reactions. They found their assumptions to be valid. (Miyahara, one of Horiuti s coworkers, and Kazusaka later (50) modified the method to take variable orders into account.) Again, a very high site density is required for the postulated mechanism of isopropanol-acetic acid esterification over silica gel, as reported by Fricke and Altpeter ( M). We showed (52), that such a high value for the site density is obtain usjng TST. 

Oijuela, A., Kolah, A., Lira, C. T., Miller, D. J. (2011). Mixed succinic acid/acetic acid esterification with ethanol by reactive distillation. Industrial Engineering Chemistry Research, 50, 9209—9220. 

Popken, T., L. Gotze J. Gmehling (2000) Reaction kinetics and chemical equilibrium of homogeneously and heterogeneously catalyzed acetic acid esterification with methanol and methyl acetate hydrolysis. Industrial Engineering Chemistry Research, 39, 2601-2611,1SSN 0888-5885. 

STEADY-STATE DESIGN FOR ACETIC ACID ESTERIFICATION... 

Figure 7.1 Azeotropes and two-liquid zone for five quaternary systems for acetic acid esterification MeAc, EtAc, IP Ac, BuAc, and AmAc.

Before leaving this section, it should be pointed out that the type III flowsheet is probably the most general configuration for acetic acid esterification. In addition to BuAc and AmAc systems, the production of w-propyl acetate, isobutyl acetate, isoamyl acetate, and -hexyl acetate also fall into this category when economic factors arc taken into consideration. 

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