Adipic acid, crystals

HK Chan, DJW Grant. Influence of compaction on the intrinsic dissolution rate of modified acetaminophen and adipic acid crystals. Int J Pharm 57 117-124, 1989. 

Frequency dependence on the temperature. The average frequency shifts with a change in the temperature The average wavenumber of the adipic acid crystals increases by 30 cm-1 from 0 to 300 K [2]. Greater shifts have been observed such as 70 cm-1 for CH3OH, or 52 cm-1 for CH3OD, between 170 K and 280 K [3,4],... 

It is the purpose of this work to employ calculations of the solvent accessible area (SAA) of sucrose and adipic acid crystals as a first attempt to quantify the effect of solvent on the crystal morphology. 

Following hydrogenation over palladium on carbon(33), dimethyl adipate hydrolysis to adipic acid is carried out using a strong mineral acid such as sulfuric acid. Hydrolysis is nearly quantitative with a selectivity of 99.5%. Since the adipic acid from the oxycarbonylation process contains no branched by-product acids, as is the case with the commercial oxidation process, extensive recrystallization is not required to produce a polymer grade material. Results indicate that the dried adipic acid crystals contain less than. 5 weight % moisture and are 99.95 weight % pure on a dry basis. 

The reaction mixture is poured into a beaker and on cooling the adipic acid crystallizes. It is filtered with suction (Note 5), and the precipitate is washed once with about 200 cc. of cold water and dried in the air. The yield of slightly yellow adipic acid is 375-386 g. (55-56 per cent of the theoretical amount). This product is pure enough for most purposes. However, to remove the yellow color and obtain a purer product, this crude acid may be recrystallized from 700 cc. of concentrated nitric acid (sp. gr. 1.42). The loss in this purification is less than 10 per cent. The recrystallized acid melts at 1530 (Notes 6 and 7). 

Fig. 12.14. Flow diagram for the manufacture of nylon 66 yarn (1) air (2) cyclohexane from petroleum (3) reactor (4) recycle cyclohexane (5) still (6) cyclohexanol-cyclohexanone (7) nitric acid (8) converter (9) adipic acid solution (10) still (11) impurities (12) crystallizer (13) centrifuge (14) impurities (15) adipic acid crystals (16) dryer (17) vaporizer (18) ammonia (19) converter (20) crude adiponitrile (21) still (22) impurities (23) hydrogen (24) converter (25) crude diamine (26) still (27) impurities (28) nylon salt solution (29) reactor (30) stabilizer (31) calandria (32) evaporator (33) excess water (34) autoclave (35) delustrant (36) water sprays (37) casting wheel (38) polymer ribbon (39) grinder (40) polymer flake (41) spinning machine (42) heating cells (43) spinnerette (44) air (45) draw twisting (46) inspection (47) nylon bobbin. (Note Whenever the demand for liquid polymer at a spinnerette is large, as, for example, in the spinning of tire yarn, it is pumped directly from the autoclave.)...

Michaels, A.S. Tausch, F.W., Jr. Modification of growth rate and habit of adipic acid crystals with surfactants. J. Phys. Chem. 1961, 65, mO-mi. 

Chow, K.Y. Go, J. Mehhdiazadeh, M. Grant, D.J.W. Modification of adipic acid crystals influence of growth in the presence of fatty acid additives on crystal properties. Int. J. Pharm. 1984, 20, 3-24. 

Figure 1.8 (a) Effect of anionic and cationic surfactants on the habit of adipic acid crystals, (b) A diagrammatic (not to scale) representation of the arrangement of molecules at the crystal surface. 

Davto, R., Villermaux, J Marchal, P. Klein, J. P. 1991 Crystallization and precipitation engineering - IV. Kinetic model for adipic acid crystallization. Chemical Engineering Science 46, 1129-1136. 

Figure 3.17 An inclusion in an adipic acid crystal examined with scanning electron microscopy.

Law, D. Grant, D.J.W. Influence of traces of w-octanoic acid in adipic acid crystals on Hiestand s indices of tableting performance of the crystals. In Agglomeration and Size Enlargement A Symposium in the First International Particle Technology Forum of the AIChE. American Institute of Chemical Engineers Denver, CO, 1994. 

Recovery of Nylon 6,6 Monomers Adipic acid and HMDA are obtained from nylon 6,6 by the hydrolysis of the polymer in concentrated sulfuric acid (Fig. 16.3). The adipic acid is purified by recrystallization, and the HMDA is recovered by distillation after neutralizing the acid. This process is inefficient for treating large amounts of waste because of the required recrystallization of adipic acid after repeated batch hydrolyses of nylon 6,6 waste. In a continuous process [25], nylon 6,6 waste is hydrolyzed with an aqueous mineral acid of 30-70% concentration and the resulting hydrolysate is fed to a crystallization zone. The adipic acid crystallizes and the crystals are continuously removed from the hydrolysate. Calcium hydroxide is added to neutralize the mother liquor and liberate the HMDA for subsequent distillation. 

Continuous recovery requires adipic acid crystals having an average diameter of ca. 40-50 nm. Such crystals are obtained by continuously introducing the hot hydrolysate containing 10-20% adipic acid into an agitated crystallization vessel while maintaining an average temperature of 20-30°C. The slurry obtained from... 

Purification and Characterization. Dry the adipic acid crystals in an oven at 110-125 °C for 10 min. Weigh the product and calculate the percent yield. Determine the melting point and obtain an IR spectrum. Compare your results to those recorded in the literature. 

David, R., J. Villermaux, P. Marchal and J. P. Klein, Crystallization and Precipitation Engineerings—IV. Kinetic Model of Adipic Acid Crystallization, Chem. Eng. Sci., 46, 1129-1136 (1991). 

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