The Improvement Process Of Methyl Acetate Carbonylsynthesize Acetic Anhydride Andthereaserchof Trace Iodine Addsorption In Product

Acetic anhydride is one of the most important chemical intermediates in modern industry,which is mainly used to produce cellulose acetate,and also applied in medicine,dye and spices industry.Due to the short process,better quality products,low consumption and less pollution,carbonyl synthesis is becoming the main synthesis for acetic anhydride gradually,which represents the advanced technology.To improve the production capacity and technical level of acetic anhydride industry in China and occupy the high-end market both at home and abroad by constructing carbonyl synthesis device with independent knowledge property rights has profound economic and strategic significance.The consequence of original esterification process which uses methanol and acetic acid as raw materials and sulfuric acid as catalyst produced amounts of waste water.The content of sulfuric acid in the waste water is up to 2-3%.To neutralize this water need to consume a large amount of lye,and have much trouble in biochemical treatment with sulfate radical.To solve this problem,we developed a new process that produce methyl acetate under high pressure at high temperature with no sulfuric acid as catalyst.When the temperature increased from 110 ? to 180 ?,pressure increased from 0.8 MPa to 2.8 MPa,the conversion of methanol increased from low conversion rate of 31%to the high conversion rate of 66%.However,the acetic acid and methanol was no longer continued to react without sulfuric acid as catalyst in the subsequent rectifying column.So,the ratio of acetic acid in the bottom could reach up to 45%,causing waste of raw materials.Then,acid recovery tower was now designed after the esterification reaction kettle to separate acetic acid in methyl acetate and water.Eventually,waste water with acid of 2-3%and a trace of methanol,acetic acid methyl ester were obtained in the tower top.Then,the waste water was poured into the neutralization pool and acetic acid with 97?98%was received in tower kettle.The obtained acetic acid was recycled as raw materials for the esterification process which can reduce the cost of production.Carbonylation,namely,methyl acetate and CO were reacted to generate acetic anhydride with rhodium and methyl iodide as catalysts.A trace of methyl iodide could not be separated lead to the loss of catalyst and influence the quality of the acetic anhydride products at the same time.Combining silver ion exchange resin and activated carbon to adsorb iodide under this reaction conditions:the temperature is 35 ?,the pressure is 0.2 MPa,the flow is about 1-1.2 L h-1and the bed height is 140-160 mm.The removal efficiency of iodine ion in more than 98%,and the iodine methane removal efficiency is over 96%.The residual iodine in product is below 20 PPb,which is better than that of potassium permanganate as the removing agent.In the end,high quality acetic anhydride products were obtained.