Study On Kolbe-Schmitt Reaction Mechanism Of Dichlorophenol In Carbonation

As an increasing requirement on environmental protection and greenhouse gas reduction, the demand for low toxicity pesticide dicamba which is widely used in crop production gradually increases and the market looks up. Preparation 3,6-Dichlorosalicylic acid which is the main feed stock of dicamba from carbon dioxide and 2,5-Dichlorophenol becomes the emphasis of research. Study on reaction characteristics of preparation 3,6-Dichlorosalicylic acid from 2,5-Dichlorophenol was studied. The suitable preparation method and catalysts or. assistants in carbonation were screened. The main factors influencing the process were. investigated and the thermodynamics was calculated simultaneously. Besides, the carbonation kinetics and reaction mechanism were also studied. The results show that measures like salify, carbonation and acidification was the appropriate preparation method and potassium carbonate was the suitable catalyst or assistant. The best process conditions were found to be ratio of feed stock=1:1, temperature=160℃, pressure=6MPa, stirring rate=600r.p.m, reaction time=4h, addition of potassium carbonate=104g and the maximal per pass and overall yield were 60% and 85% respectively. The output of heat was low in the process which can be easily controlled. The kinetic equations in different temperature and pressure show that the experimental values were well identical to the theoretical values and the process of reaction was mainly influenced by ash zone diffusion. The shell of reaction products gradually increased with time. The process reached equilibrium and turned to be controlled by mass transfer. The design tests determined reaction equation of carbonation. The reasonable reaction mechanism and effect of potassium carbonate in carbonation were supposed. The elementary research content optimized the whole process and the following deep exploration was demonstrated.