Study On The Dehydration Of Terpin Hydrate To Prepare Terpineol

Terpineol is an important fine chemical,which is widely used in daily necessities,medicine and health fields.Under the influence of the COVID-19 epidemic in 2020,terpineol has gained a broad market in the field of medicine and health due to its disinfectant and flavoring function.The process of synthesizing terpineol mainly includes one-step method and two-step method.Among them,the aroma of terpineol product of one-step method is not favorable,causing its market problem.On the other hand,the two-step product has good flavor,high price and large market demand,then has become the most important process for the production of terpineol in industry.However,there are some problems in the dehydration stage of terpin hydrate in the two-step process:terpinol selectivity was low(about 72%)and crystallization time was long(one week),which led to the limitation of terpineol output and affected the market.To solve the problem,this work tried to introduce two new technologies to shorten the production cycle:induced crystallization dehydration technology and supercritical fluid extraction enhanced dehydration technology.The dehydration of terpin hydrate to terpineol was implemented by the induced crystallization process which used an inducer to induce crystallization of the product after the dehydration reaction with relatively short time to improve the selectivity to terpineol;the unreacted raw material was reused.The optimal reaction time was 90 min and the temperature was 100℃ with the sulfuric acid concentration of 0.3%and the mass ratio of terpin hydrated to dilute sulfuric acid of 1:3.Under the conditions,the single-pass conversion of terpin hydrate was 83.4%,and the terpineol selectivity was 83.5%.Besides,when the inducer dosage was 2%(in mass)of the raw material,the crystallization time was shortened to 3 days compared to7 days for the traditional process.In the experiment,the dehydration reaction for the recycled crystals was carried out,and the reaction result was similar to that of initial feed.By this recycled process,the terpineol yield was finally 81%which was 11%higher than that of the traditional process.On the basis of the solubility study of terpin hydrate and terpineol in supercritical CO2 by theoretical calculation,supercritical extraction enhanced dehydration technology was proposed,by which the produced terpineol was timely separated from the reaction system to enhance the reaction.The optimal reaction time was 130 min,extraction pressure was 15 MPa and reaction temperature was 95℃.Under the conditions,the terpineol yield of the process was up to 93%,which was 23%higher than that of the traditional process.At the same time,the process reduced multiple processes and greatly improved the productivity of a single reactor.