Research On The Application Of Biomass Glycerol In The Synthesis Of Pesticide Intermediates

In recent years the shortage of fossil energy has promoted the the biodiesel industry developed rapidly, and global biodiesel production is expected to reach 20.5 million tons in 2011. Glycerol is the main by-product obtained and about 10wt% of glycerol is produced during the production of biodiesel. This is leading to excess output of glycerol on the market and price decline. The proper use of biomass glycerol can effectively reduce the cost of biodiesel and increase utilization rate of resourse. So it has attracted many researchers’interests. In this paper, the present applications of glycerol were reviewed and three new using strategies of glycerol were designed for the synthesis of pescitide and intermediates including 3-methoxypropanal, metolachlor and 1, 3-propanediol. This is important to solve application problems of glycerol.1. 3-methoxypropanal is the intermediate of imidazolinone herbicide imazamox which is high-effective and low-toxic. Using glycerol as the starting material, 3-methoxypropanal was obtained via two reaction steps of methylation and dehydration. A new complex catalyst, consisting of anhydrous copper sulfate and PEG600, was invented for the dehydration reaction. Compared with other existing preparing methods of 3-methoxypropanal, this method had such advantages as raw materials available readily, operation process simple and low cost. The method has application potential in the synthesis of 3-methoxypropanal.2. Metolachlor is a wide-spectrum, highly-active and chlorinated amide herbicide. The effect is widely recognized by the people. It is one of the main herbicide used in China at present. The herbicide metolachlor was synthesized using glycerol as the starting material, comprising five reaction steps. Firstly, acetol was produced by dehydration of glycerol. Then the intermediate N-(1’-methyl-2’-hydroxyethyl)-2-ethyl-6-methylaniline was obtained by condensation and hydrogenation reactions of acetol and 2-methyl-6-ethylaniline. Finally, through acylation with chloroacetyl chloride and etherification with methanol, metolachlor was ontained. The noval synthetic process of N-(1’-methyl-2’-hydroxyethyl) - 2-ethyl-6-methylaniline from glycerol has not been reported before. The optimized operation conditions were that using zinc chloride as catalyst, xylene as solvent, the mole ratio of acetol and 2-methyl-6-ethylaniline being 2, reaction pressure at 3.2 MPa and reaction temperature at 150℃. This method provided a feasible route for deep processing of glycerol.3. With glycerol as the starting material, 1, 3-propanediol was obtained via four reaction steps: protection as acetal, chlorination, hydrolysis and catalytic dechlorination-hydrogenation. Through the selection of aldehydes and the optimization of treatment, high purity 1, 3-protected product of 5-hydroxy-2-phenyl-1, 3-dioxane was obtained. Then the un-protected hydroxyl group was chlorinated with bis (trichloromethyl) carbonate, followed by deprotection and dechlorination-hydrogenation, 1, 3-propanediol was prospectively obtained with high selectivity. In our experimental results, however, a rearrangement reaction was conducted in the chlorination step, which causing the major product obtained was 1, 2-propanediol. This paper also examined the effect of catalysts and the types of substrate on the reaction of glycerol condensation, which laid a good foundation for improving the selectivity of 1, 3-protected product.In addition, in the early stage, the synthesis of a fluorine-contained pesticide intermediate of 4-chloro-2-trifluoromethyl aniline was researched. The results showed that 4-chloro-2-trifluoromethyl aniline was obtained in 95% conversion and 80% selectivity using o-(trifluoromethyl) aniline as raw material, hydrogen peroxide/hydrochloric acid as chlorination reagents and chloride copper as catalyst. This synthetic route is shorter and reaction condition is mild, which is suitable for industrial production. In summary, three new applications of glycerol in fine chemicals were developped, which expanded the application approaches of glycerol and laid a good foundation for the future work.