Dehydration of acetic acid

New acid catalyst comprising Keggin-type heteropoly acid supported on mesoporous silica for dehydration of acetic acid... 

The first attempt to synthesize and characterize Kegj -type heteropoly acid supported on various mesoporous silicas and its application to add catalysis in the formation of acetic anhydride via dehydration of acetic acid were described in this study. A variety of characterization techniques such as Na adsorption, TEM and XRD were applied... 

The selectivity for acetic anhydride in the catalytic dehydration of acetic acid could be controlled by the pore size of pure mesoporous silica SBA-15. New acid catalyst comprising Keggin-type heteropoly acid supported on SBA-15 enhanced the activity etfectively when tungstophosphoric acid was highly dispersed on the silica substrate. 

Table 10.3 Economics of Different Processes for Dehydration of Acetic Acid... 

In the 1940 s, in addition to these operations, two other processes became important. Acetic acid was made by reacting methanol with carbon monoxide, and acetic anhydride was being made by the ethylidene diacetate process, which in effect is the dehydration of acetic acid to the anhydride by the use of acetylene. Fermentation ethyl alcohol was converted to acetic acid via acetaldehyde as well as by the direct oxidation of ethyl alcohol. A new operation on the Gulf Coast was also based on acetaldehyde. However, the acetaldehyde is made by the direct oxidation of liquefied petroleum gas. A further process for the production of these materials, in which acetaldehyde is oxidized in one step to a mixture of anhydride and acid, was also begun. 

Ordinary rectification for the dehydration of acetic acid requires many trays if the losses of acid overhead are to be restricted, so that azeotropic processes are used exclusively. Among the entrainers that have been found effective are ethylene dichloride, n-propyl acetate, and n-butyl acetate. Water contents of these azeotropes are 8, 14, and 28.7 wt%, respectively. 

Acetic anhydride is produced by three major processes (I) dehydration of acetic acid, t2) decomposition of acetone, and t.3) oxidation of acetaldehyde The formates und ucct3tes are prepared hy reacting the appropriate alcohol and organic acid in the presence of p-toluene-sulfonic acid... 

Koops et al. [39] investigated the pervaporation selectivity as a function of membrane thickness for the polysulfone, poly(vinyl chloride) and poly(acrylonitrile) membranes in the dehydration of acetic acid and reported that selectivity decreases with decreasing membrane thickness, below a limiting value of about 15 pm. 

S.P. Kusumocahyo, M. Sudoh, Dehydration of acetic acid by pervaporation with charged membranes, J. Membr. Sci. 161 (1999) 77-83. 

X.P. Wang, Modified alginate composite membranes for the dehydration of acetic acid, J. Membr. Sci. 170 (2000) 71-79. 

Let us consider some examples, such as conjugated oxidative dehydration of acetic acid [7] 2CH3COOH(lq) (CH3C0)20(lq) + H20(lq), (3.11)... 

Mujtaba and Macchietto (1992) summarises a list (Table 9.1) of reaction schemes with boiling points of the species involved. For each reaction scheme (with reactants shown on the left and products on the right), the right type of batch distillation column is indicated. The recommendation does not hold when the desired products are those shown on the left hand side of each reaction scheme. For example, acetic anhydride is produced by dehydration of acetic acid (Acetic Acid <=> Acetic Anhydride + Water). In such cases, the use of CBD will be favourable to remove the water or the use of IBD will be favourable to remove the anhydride. In both configurations the equilibrium will shift to the right and the productivity of anhydride will improve. Wajge and Reklaitis (1999) considered such reaction scheme in a CBD column. Further details are in section 9.9. 

Wajge and Reklaitis (1999) considered a simple single duty multiperiod operation using the hydrolysis reaction of acetic anhydride (Ullmann, 1985) to demonstrate the RBDOPT framework. Acetic anhydride is manufactured by dehydration of acetic acid. The by-product of the process is a mixture of acetic anhydride, water and acetic acid with boiling points 412 K, 373.2 K and 391.1 K respectively for each component in the mixture. The main concern is that the acetic anhydride and water in the mixture may hydrolyse quite quickly to produce back the acetic acid. 

Dehydration of acetic acid, alcohols, and acetone by pervaporation... 

Ray S and Ray SK. Dehydration of acetic-acid, alcohols and acetone by pervaporation using acrylonitrile-maleic anhydride copolymer membrane. Sep. Sci Tech. 2005 40(8) 1583-1596. 

Only one monocarboxylic acid anhydride is encountered very often however, this one, acetic anhydride, is immensely important. It is prepared by the reaction of acetic acid with ketene, CH2==C- O, which itself is prepared by high-temperature dehydration of acetic acid. 

Definitive evidence for the imidate intermediate was provided by Glikmans in 1966. Reaction between isobutene and acrylonitrile in anhydrous acetic acid containing 100% sulfuric acid allowed isolation and characterization of (7), which was readily hydrolyzed to the corresponding amide by dehydration of acetic acid (equation 1). Subsequent work by NorelF on reactions of alkenes with nitriles In anhydrous liquid hydrogen fluoride allowed isolation of imidoyl fluorides such as (8) for the first time. Such materials, obtained pure and fully characterized, react instantly with water to yield the amide (Scheme 4). 

Sato K, Sugimoto K, Kyotani T, Shimotsuma N, Kurata T. Synthesis, reproducibUity, characterization, pervaporation and technical feasibUity of preferentially b-oriented mordenite membranes for dehydration of acetic acid solution. J Membr Sci 2011 385-386 20-29. 

Othmer D. R, Process for dehydration of acetic acid and other lower fatty acids. U.S. Patent 2,050,234 (1936). 

The product of the condensation of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a major application, and uses approximately 25% to 30% of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene, which condenses with acetic acid to give the anhydride ... 

The two-carbon short-chain acetic acid is start material for the production of vinyl acetate monomer (VAM). This application consumes one third of the world s production of acetic acid (Cheung et al. 2005). The product of the condensation of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a further major application and uses approximately 25-30 % of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene at the temperature of 700-750 °C. Ketene is thereafter reacted with acetic acid to obtain the anhydride (Held et al. 2005). Acetic anhydride is an acetylation agent. As such, its major application is for cellulose acetate, a... 

In liquid separation, hollow fiber membranes based on PBI have shown excellent performance for pervaporation dehydration of organic liquids. For example, a dual layer PEI-PBI hollow fiber membrane with an outer selective layer of PBI showed better performance than most other polymeric membranes in pervaporation dehydration of ethylene glycol. Sulfonation modifications of PBI membranes have demonstrated excellent separation efficacies in the dehydration of acetic acid. Studies have shown that PBI hollow fiber membranes were effective in separating chromates from solutions. Also, PBI nanofiltration hollow fiber membranes are promising candidates as forward osmosis membranes. In gas separation, recent studies sponsored by the Department of Energy at Los Alamos National Laboratories and SRI International demonstrated potential applications of PBI membranes in carbon capture and Hj purification from synthesis gas streams at elevated temperatures. H2/CO2 selectivity > 40 has been achieved at H2 permeability of 200 GPU at 250°C. ... 

Y. Wang, T.S. Chung, M. Gruender, SuUonated polybenzimidazole membranes for pervaporation dehydration of acetic acid J. Membr Sci., 415-416,486-495 (2012). 

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