Acetic processing

Secondary Acetate Processes. There is no commercial process to directiy produce secondary cellulose acetate sufficientiy soluble in acetone to produce fiber. Hence, the cellulose is completely acetylated to the triacetate during the dissolution step and then hydrolyzed to the required acetyl value. 

The solution process consists of four steps preparation of cellulose for acetylation, acetylation, hydrolysis, and recovery of cellulose acetate polymer and solvents. A schematic of the total acetate process is shown in Figure 9. 

The poly(vinyl alcohol) made for commercial acetalization processes is atactic and a mixture of cis- and /n j -l,3-dioxane stereoisomers is formed during acetalization. The precise cis/trans ratio depends strongly on process kinetics (16,17) and small quantities of other system components (23). During formylation of poly(vinyl alcohol), for example, i j -acetalization is more rapid than /ra/ j -acetalization (24). In addition, the rate of hydrolysis of the trans-2iQ. -A is faster than for the <7 -acetal (25). Because hydrolysis competes with acetalization during acetal synthesis, a high cis/trans ratio is favored. The stereochemistry of PVF and PVB resins has been studied by proton and carbon nmr spectroscopy (26—29). 

Cmchonine, C19H22ON2. This alkaloid is usually present in cinchona and cuprea barks. One of the best sources is Cinchona micrantha bark. It occurs in the crude quinine sulphate mother liquors. The mixed alkaloids recovered from these may be extracted with ether to remove quinidine and cinchonidine and the insoluble residue boiled with successive small quantities of alcohol, from which cinchonine crystallises on cooling. The crude alkaloid is neutralised with dilute sulphuric acid and the sulphate recrystallised from boiling water. Cinchonine so prepared contains quinidine, from which it may be freed by crystallisation from boiling alcohol until it ceases to exhibit fluorescence in dilute sulphuric acid. It will then still contain 10 to 15 per cent, of dihydrocinchonine, which may be removed by reprecipitation as the cuprichloride, B. 2HC1. CuClj, or by the simpler mercuric acetate process of Thron and Dirscherl. ... 

Cinchotine (Hydrocinohonine, more correctly dihydrocinchonine, Cinchonifine, >fs-Cinchonine), C19H24ON2. This alkaloid occurs in commercial cinchonine to the extent of about 14 per cent. and may be prepared from this source by the mercuric acetate process, or more conveniently by the hydrogenation of commercial cinchonine previously freed from quinidine. ... 

Hydrodnchonidinc Dihydrocinchonidine, Cinchamidine), Cj This alkaloid was isolated by Forst and Bohringer from commercial cinchonidine, from which it may be obtained by the mereurie acetate process, but is more conveniently prepared by the hydrogenation of pure cinehonidine. It crystallises in six-sided leaflets, m.p. 232°,... 

Hydroquinine (Dihydroquinine), C20H26O2N2.2H2O. This base was isolated by Hesse from the mother liquors of quinine sulphate manufacture and is present to the extent of 5 to 6 per cent, in commercial sulphate of quinine, from which it is best isolated by the mercuric acetate process. The demand for hydroquinine as such and as a material for the preparation of hydrocupreine has led to its manufacture from quinine by catalytic hydrogenation. It crystallises from ether or benzene in needles, m.p. 173 5° (dry), — 235 7° (c = M/40, N/10 H2SO4) or... 

The presence of free sulphuric acid in rayon-spinning baths limits application of the austenitic steels, but they are used for acetylation of cellulose in the acetate process. They are also used for dissolving and spinning solutions in the cuprammonium processes. 

Eastman chemical engineers provided innovative solutions to key steps in the methyl acetate process. Computer simulations were used extensively to test ways to minimize the size of the reactors and recycle streams, to maximize yields and conversions, and to refine the methyl acetate in a minimum number of steps. 

Electron-rich aromatic systems can act efficiently as Michael donors, as shown recently by Krohn s group (Scheme 2.46) [111]. For example, reaction of the enone 2-193 with the resorcine derivative 2-194 in a domino Michael/acetalization process led to various naturally occurring xyloketals of type 2-196 in excellent yield. 

Haertling, G. H. 1992. An acetate process for bulk and thin film PLZT. Proc. 7th Inti. Symp. Appl. Ferro. (Urbana June 6-8). pp. 292-295. 

Continuous ethyl acetate process, 10 483 Continuous Exposure Guidance Levels (CEGL), 21 837 Continuous extractors, 10 751 Continuous falling film SO3 sulfonation process, 23 544, 550-552 Continuous fiber composites, fabrication of, 26 766, 767... 

Today acetic acid is produced mainly from methanol and carbon monoxide. This process, along with the Tennessee Eastman acetic anhydride plant using syn gas, are the current standards in the industry when considering new expansion regardless of the price of ethylene. The vinyl acetate process described here may achieve this stature if its commercial development is permitted to occur. 

The basic cellulose unit contains three hydroxyl groups. The triester cellulose triacetate forms when cellulose is reacted with glacial acetic acid. Hydrolysis removes some of the acetate groups to form a secondary ester, which averages about 2.4 acetyl groups per unit rather than three. The secondary ester is then dissolved in acetone and the solution ejected through a spinneret to form fibers. Cellulose acetate processed in this manner is referred to as acetate rayon, but it may be more commonly known by its trade name Celanese. 

The cuprammonia process, the viscose process, and the acetate process have been employed for the production of rayon. Cuprammonia and viscose rayons have similar chemical and physical properties. Both are easily dyed and lose their strength when wet because of a disruption of hydrogen bonding this wet strength is improved through chemical treatment of the rayon fabrics. Acetate rayon is readily softened in the ironing process and loses its luster in boiling water. 

Reis, Thomas, "Compare Vinyl Acetate Processes, Hydrocarbon Processing (1966) 45 (11), 171. 

Industrial problems have, in some instances, been solved either by a proper choice of construction materials and suitable process design or by development of heterogeneous catalytic systems using supported complexes or by generating active complexes in situ on a support material which avoid some of the problems of liquid-phase operation. For example, a number of the problems in liquid-phase vinyl acetate processing have been overcome by development of supported Pd catalysts (106). Vapor-phase hydroformylation has been carried out on supported rhodium complexes (107). 

The vinyl acetate process exists in both homogeneous and heterogeneous versions. The liquid-phase process developed by ICI is essentially a Wacker reaction performed in acetic acid ethylene, 02 and AcOH are reacted at 110 °C in the presence of PdCl2, Cu(OAc)2 and HC1. Overall yields are greater than 90%. Acetaldehyde is formed as a coproduct in the reaction, owing to the presence... 

Case E Eastman Chemical Methyl Acetate Process (Siirola, 1995, 1998). In the commercial operation of the Eastman methyl acetate process, many reaction and separation functions are combined in one single large column (a few meters in diameter and 80 meters high (38). The number of pieces of major equipment compared to a conventional design is reduced by a factor of 10 (36). The primary energy consumption and capital expenditure is reduced by a factor of 5 (38). 

Figure4.30 Chemical reactions and simplified process schematic for BP s AVADA ethyl acetate process.

Chen, R. and McAvoy, T. J. (2003). Plantwide control system design methodology and application to a vinyl acetate process. Ind. Eng. Chem. Res., 42, 4753-4771. 

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