Experimental investigation of continuous multistage countercurrent crystallizer for separation P-nitrochlorobenzene and O-nitrochlorobenzene

Industrial grade 2-pyrrolidone with a purity of 99.5% is produced by aminolysis of γ-butyrolactone and subsequent fractional distillation, but it still contains trace amounts of γ-butyrolactone and...

Purification of 2-Pyrrolidone by Falling Film Melt Crystallization

Melt crystallization has been considered as a green separation technique and widely applied in industry and manufacture due to several attractive features, including no need for solvent, achieving specific product...

Recent Advance of Melt Crystallization, Towards Process Intensification and Techniques Development

With the increasingly fierce competition in the chemical industry and the increasing attentions paid to environmental protection by human beings around the world, the development of green and efficient industrial purification technology has become an inevitable trend, and the crystallization purification method has attracted the attentions of industry due to its good purification effect. Melt crystallization is widely used in industrial production due to its advantages of green, high efficiency and low energy consumption. This paper introduces the classification and principle of melt crystallization, and compares it with rectification and solution crystallization. Next, the influencing factors of the crystallization process are systematically summarized from three aspects: crystallization, sweating and external factors. Then, the coupling methods of melt crystallization with other techniques are reviewed. Finally, the prospect of melt crystallization is discussed. 

Recent Progress in Melt Crystallization

m-Cresol and p-cresol, important chemical intermediates, are widely used in medicine and pesticides. The mixture of m-cresol and p-cresol is easily produced in the industrial scale. However, it is very difficult to separate the mixture due to the boiling point. In this work, a new coupling process route combining complex crystallization and melt crystallization was proposed for the mixture separation. The key parameters in terms of crystallization temperature, solvent dosage, complexing agent dosage, initial purity of p-cresol, and crystallization time are investigated. The response surface methodology was employed to optimize the proposed process. The results show that the m-cresol and p-cresol mixture can be effectively separated, where the purity is >99% and the yields of m-cresol and p-cresol are over 63% and 55% respectively. In addition, recovery of solvents and complexing agents is achieved. The coupling route is proven to be a simple, environment-friendly, and sustainable process to separate industrial cresol. This study provided a reference for the isomerization separation process. 

Analysis and Optimization of a Novel Coupling Process for Industrial Cresol Separation

A new melt crystallization process for efficient purification of chlorobromobenzene

The invention provides a method for separating p-chlorobromobenzene and o-chlorbromobenzene by a suspension fusion crystallization method. The method comprises the following steps: carrying out ultrasonic dispersion on a solid-liquid mixture of o-chlorobromobenzene and p-chlorobromobenzene for 25-35 minutes to obtain a dispersion liquid; adding the dispersion liquid into a fusion crystallizer, andcarrying out heating to 60-75 DEG C to obtain a mixed molten liquid; and cooling the mixed molten liquid to a range from -10 DEG C to 20 DEG C at a cooling rate of 0.05-0.5 DEG C/min, growing crystals for 1-6 hours, and carrying out suction filtration, washing and drying to obtain p-chlorbromobenzene. According to the separating method of p-chlorbromobenzene and o-chlorobromobenzene, a reasonablecrystallization process route is designed, and crystallization process conditions are controlled, so that separation of a p-chlorobromobenzene isomer and an o-chlorobromobenzene isomer is realized. In addition, through controlling the cooling rate and the crystal growing temperature, the problems that the mother liquor is seriously occluded and the product purity is relatively low in a crystallization process by an ordinary melting crystallization method is avoided, purity of the p-chlorobromobenzene can reach 99% or above, and the highest one-way yield can reach 66.1%.

Baoshu Liu

Papers

A new melt crystallization process for efficient purification of chlorobromobenzene

Method for separating p-chlorobromobenzene and o-chlorbromobenzene by suspension fusion crystallization method