Study On Green Synthesis Technics Of Methyl N-Phenyl Carbamate

Methyl N-phenyl carbamate(MPC) is intermediate product of 4,4 '-diph-enylmethane diisocyanate (MDI),while the isocyanate is an important raw material for producing polyurethane.Traditional synthesis industry of MDI is adopt to phosgene,whose technics route is long,technology is complex,equipment is expensive and especially the toxicity of phosgene is too serious to pollute environment.Methyl phenyl carbamate(MPC) is greenly synthesized from aniline and dimethyl carbonate(DMC), which becomes the focus of research and development because of overcoming the above disadvantages.Based on method of high pressure of the reaction,this paper successfully explores effective synthesis ways under microwave,bridging the gap in our country and blazing a new trail for synthesis MPC in the way of green, efficience,and low power consumption.In this paper,effective synthesize ways of MPC are stressfully investigated under the microwave.Effect of dosage of catalyzer,temperature,time,power and loaded capacity on catalytic reactions are discussed to confirm the optimum technics conditions.The mainly reason of catalyst deactivation is analyzed,meanwhile the effective fixed modified method and the dosage of sodium silicate are proposed.The result of experiment indicates that the reaction is able to carry through and have a good catalytic effect in the condition that the size of catalyst is general equal to reagent.The neutral carrier-activated carbon is beneficial to the synthesis reaction under the microwave condition . Supported catalysts Zn(OAc)₂/AC is used to inspect catalytic reaction. The optimum process parameters determined by comparative analysis of a single factor are as follows: reaction temperature is 140℃,reaction time is 7 min,reaction power is 100W,zinc acetate load is 10 percent.Through experiment of comparing supported catalyst before washed with after washed,it is initial proved that the catalyst center exists in the vast majority of activated carbon surface.After supported catalysts is repeated use,the main reason of catalyst deactivation is that zinc acetate absorbed on the activated carbon is lossing continuously . In order to resolve the loss of Zn(OAc)₂ on the surface of activated carbon,sodium silicate,humic acid and hydroxymethyl cellulose sodium are used to modify catalyst fixation.Then immobilization of sodium silicate is found to be good catalytic effect.Modification of sodium silicate catalyst also made a corresponding amount of discussion,when the sodium content is up to 3%,still have good catalytic effect,and extended life.Since three different methods of immobilization,which is fully demonstrated that the promotion of the catalytic reaction center is a complete molecular zinc acetate.The experimental results show that using microwave technique to synthesize MPC can greatls accelerate the reaction rate.Compare with conventional high pressure,microwave method can be more than 40 times faster,synthetic short time,saving energy,with a wide range of industrial application foreground.