Studies On Preparation,Crystallizing And Drying Of Taurine From Monoethanolamine

Taurine, which is a conditionally essential amino acid containing sulfur element, is one of the most abundant free amino acid in many tissues. Taurine is different than most other amino acids because it is not incorporated into proteins, but it does play many important roles in the body, including bile acid conjugation, detoxification, membrane stabilization, osmoregulation, modulation of excitatory neurotransmission and intracellular calcium levels, then protections for kind cells, tissues, organs and systems. Taurine is widely used as pharmaceutical ingredients, food additives, feed additives, cosmetic ingredients, and synthesis of surfactant, fluorescent bleacher and other organic substance. It is largely demanded in the international and domestic market with a total volume reaching to 50,000 metric tons, and the sales amount increases by more than 20% every year. The main source of taurine is from chemical synthesis.The synthesis method of taurine from monoethanolamine, the process optimization and the improvement for crystallizing and drying of the product were studied, in order to raise the synthesis yield of taurine and reduce the production cost.The optimization of esterification and sulfonation is as below:The temperature dropping sulfuric acid into monoethanolamine between 20-30℃ within time of 4 hours, esterification temperature should be controlled around 115℃; with sodium sulfite as sulfonation agent, the stoichiometric ratio of monoethanolamine hydrosulfate (MES) and sodium sulfite is optimized at 1:1.4, reaction time of 16 hours is enough for sulfonation reaction completion; and it is better to adjust the pH value of the solution of MES with ammonium bicarbonate than sodium carbonate. Among the 4 sulfonation agents, sodium sulfite, ammonium sulfite, potassium sulfite and ammonium hydrogen sulfite, ammonium sulfate can bring the highest yield of tauirne, yet effect of which in the post-processing for desalting is not as efficient as the situations of using sodium sulfite.The research of the influence factors for crystallization process of taurine indicates that the increase of the solution saturation results in smaller particle size of taurine crystallization and even size distribution. Using ethanol solution and regulating the proportion of ethanol and water can improve taurine particle fineness. And the bulk density and particle size of taurine can be adjusted through controlling the pH value, stirring speed, organic solvent polarity, cooling speed. The optimizations for taurine crystallizing are pH 5.5, stirring speed 100 r/min,10% ethanol as solvent, cooling rate 2℃/min.This paper also points out that the methods to improve the anti-caking performance of taurine product:Control the crystallization process to achieve the oven particle size distribution, lower product impurities and moisture content; shorten the storage time; keep storage temperature and humidity stable in a cool and dry storage conditions; use certain anti caking agent (such as silica 0.5%). Several drying methods, such as static hot air drying, double taper turning vacuum drying, and microwave drying, are studied and it shows that the microwave drying or vacuum microwave drying is the suitable drying way, because it keeps as much as possible taurine morphology and size distribution of taurine. The research of the stability of taurine confirm that the validity of taurine packed in PE bag lined carton or polybag and stored under 25±2℃ is above three years.