Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1995-12-26
1997-09-02
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C07C 3784
Patent
active
056634560
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for obtaining large crystals with high purity by destructing part of the fines formed during crystallization, the application of said method, more particularly, a method for obtaining a crystalline product with large and uniform crystal size and high purity by effectively destructing a part of lines in slurry in a crystallizer by using special filters in the crystallizer and a special fines destruction loop outside the crystallizer and the application of the said method in the preparation of bisphenol A with high purity.
BACKGROUND OF THE INVENTION
According to the theory of solution crystallization, the purity of a crystalline product relies on the crystal size distribution to a large extent. Particularly, the purity of a crystalline product is greatly influenced by the fraction of fines. An increase in the fines fraction inevitably results in an increase in the crystal surface area per unit weight. This not only increases the amount of impure mother liquor entrained by the crystals, but also diminishes the benefit of filtering and washing operations. Consequently, it is difficult to obtain a high purity product in one stage crystallization and generally multi-stage crystallization is needed, causing unnecessary waste. Many studies support this finding. Therefore, in order to improve the product purity or obtain the greatest possible benifit from washing and filtering operations, it would be desirable to obtain a crystalline product with a large and uniform crystal size in the crystallization process.
In a continuous or batch crystallizer, crystal particles are formed as a result of the growth of individual crystal nuclei. In a fixed amount of slurry, if the number of the crystal nuclei is too large, the crystal size of the final product must be small since a limited mount of solute is distributed over excessive crystal nuclei. Therefore, it is necessary to destruct the excessive crystal nuclei in time. An effective destruction of fines is beneficial not only for increasing the mean crystal size of the product, but also for raising the crystal growth rate, because in a crystallizer with a fines destruction system the degree of supersaturation may be somewhat increased, and hence both the crystal growth rate and the production capacity of the crystallizer are improved.
The existing methods for destructing fines are the setting method based on elutriation theory and the size fractionation method, for example, see the following reference: Press, New York, 1988; Nyrlt, J., Industrial crystallization. The state of Art; VCH, Weinheim, 1982; U.S. Pat. Nos. 3,873,275; 5,124,265; Qing Xu-huai and Tan Qiu, Industrial Crystallization, Chemical Industry Press, Beijing, 1985. The settling method requires an annular baffle set in the crystallizer to form a settling zone. However, the presence of the settling zone not only increases the complicacy of the crystallizer structure, but also reduces the effective volume and the production capacity of the crystallizer. Moreover, it is difficult to apply the settling method to a crystallization processes which is carried out under vacuum, pressure or by evaporation. In brief, the settling method is troublesome in operation and poor in adaptability. On the other hand, the size fractination method requires complicated equipments and demonstrates poor suitability. In addition, both the above methods are essentially unsuitable to those systems in which the density difference between solid and liquid is small.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method for overcoming the disadvantages of the prior art mentioned above and for obtaining large crystals with high purity by destructing part of the fines in a slurry.
Another object of the present invention is to obtain a bisphenol A product with high purity by using the present method in the preparation of bisphenol A.
As a result of an extensive study carried out by the inventors, it was found that the said objects can be ach
REFERENCES:
patent: 3900292 (1975-08-01), Fairchild
patent: 3992900 (1976-11-01), Campbell
patent: 3996018 (1976-12-01), Midler, Jr.
patent: 4159194 (1979-06-01), Steward
patent: 4263010 (1981-04-01), Randolph
patent: 4670611 (1987-06-01), Lemay
patent: 4735781 (1988-04-01), Thijssen et al.
patent: 5043071 (1991-08-01), Anselme et al.
patent: 5074999 (1991-12-01), Drori
patent: 5124265 (1992-06-01), Randolph
patent: 5147412 (1992-09-01), Klinksiek et al.
Li Chuanzhao
Liu Zongzhang
Qian Shenghua
Yu Shenbo
Zhang Minhua
Badio Barbara
China Petro-Chemical Corporation
Dees Jos,e G.
Tianjin University
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