Study Of Acetaldehyde Ammoximstion Catalyzed By TS-1

Acetaldehyde oxime is a kind of important pesticide and pharmaceutical intermediate,and it can also be used as a new type of boiler deoxidizer,excellent extractant and adsorbent,etc.The traditional method for the synthesis of acetaldehyde oxime is hydroxylamine sulfate or hydroxylamine hydrochloride,which have complicated steps and lead to large pollution.As a new,green synthesis method,acetaldehyde oxime can be obtained via the system of TS-1/H2O2.The reaction of acetaldehyde ammoxidation was used as a probe reaction to investigate the reaction mechanism,and the optimum synthesis conditions of TS-1and acetaldehyde oxime.The morphology and structure of TS-1 were analyzed by XRD,FTIR,SEM,XRF and BET.The reason of TS-1 deactivation was investigated and the catalyst is regenerated by high-temperature roasting.The mechanism of TS-1/H2O2 catalytic oxidation was studied by ReactIR15.The results showed that the catalytic oxidation process of TS-1/H2O2 follows the hydroxylamine route,which is that ammonia was firstly oxidized by H202 to form intermediate product hydroxylamine under the catalysis of TS-1,and then acetaldehyde oxime forms after hydroxylamine reacts with acetaldehyde.TS-1 catalyst was prepared by hydrothermal synthesis method.The best Si/Ti and TPAOH/Si were 50 and 0.035 respectively,and the optimum crystallization time was 48h.The optimum calcination time was 6h.According to the results of catalytic performance,the suitable reaction conditions showed that the optimum reaction temperature was 60℃.When acetaldehyde dosage was 0.1mol,tert-butyl alcohol and catalyst dosage were respectively 22g and 3g.The best ratio of ammonia to acetaldehyde was 3.0,and the best ratio of H2O2 to acetaldehyde was 1.3.H2O2 was added into the system by continuous feeding,and the best dropping time was 1.5h.The whole reaction time was 2h.Under the optimum reaction conditions,the conversion rate of acetaldehyde and acetaldehyde oxime selectivity were 89.48%and 82.69%,respectively.TS-1 deactivation was caused by carbon deposition.The catalytic activity of catalyst,which was regenerated by high temperature calcination,could almost all be recovered,and the conversion rate of acetaldehyde and acetaldehyde oxime selectivity were 88.50%and 81.11%,respectively.The regeneration temperature should be higher than 500 ℃,and the regeneration time should be longer than 5h when the temperature was 500℃.With the increase of regeneration temperature,regeneration time can be shortened.When the regeneration temperature is 700℃,the regeneration time can be reduced to 4h.