Catalytic Synthesis Of Carbamic Ester From Urea And Alcohol Over Alkali-treated Zeolites

In this paper, molecular sieve HZSM-5(Si/Al = 38) was treated by using different concentrations of NaOH aqueous solution and the treated HZSM-5 materials was characterized by SEM, XRD, FT-IR, NH3-TPD and N2 adsorption-desorption technique for determine their surface morphology and properties.The alkali-treated zeolite by different concentrations of NaOH aqueous solution(HZSM-5-x, x represents the concentrations of NaOH aqueous solution) used as effective catalysts for reaction of urea and methanol to generate methyl carbamate. The HZSM-5-0.2 exhibited excellent catalytic performance for producing methyl carbamate from methanol and urea. The relationship between catalytic activity and morphology, specific surface area, acidity on the surface of the zeolite was discussed. The results indicated that the treated zeolites with medium concentration of NaOH aqueous solution represented high catalytic activity due to their moderate acidity on the surface. At the same time, the optimal conditions for zeolite treatment and the synthesis reaction by using HZSM-5-0.2 as catalyst was determined: after the zeolite was calcined at 550 °C for 6 h. The HZSM-5 was treated with 0.2 mol/L of NaOH aqueous solution at 80?for 2 h, followed by dried at 120 °C for 12 h. And the optimal reaction conditions: the CH3OH/Urea molar ratio 40:1, the reaction temperature 180?, the reaction time 8h and amount of the catalyst 0.3g. Under these conditions the conversion of urea 99.0% and 97.8 % selectivity to MC were achieved.In addition, the catalytic performance of HZSM-5-x for producing benzyl carbamate from benzyl alcohol and urea was also evaluated. The results showed that the catalyst HZSM-5-0.1 exhibited good catalytic activity for this reaction, achieving conversion of urea 97.0% and 95.1% selectivity to benzyl carbamate. The optimal reaction conditions using HZSM-5-0.1 catalyst were also obtained: the BzOH/Urea molar ratio 40:1, the reaction temperature 180?, the reaction time 6h and amount of the catalyst 0.2g.