固体碱MgO/η-Al2O3的制备及其催化废水中尿素水解的研究

Preparation of MgO/η-Al2O3 solid base catalyst for the hydrolysis of urea from wastewater

摘要:

以η-Al2O3为载体，制备了一系列不同负载量的MgO/η-Al2O3固体碱，采用X射线衍射、N2-BET手段表征了固体碱的晶型结构和表面性质，运用返滴定法测定了其表面碱量。以该固体碱为催化剂进行了催化废水中尿素水解的实验研究，考察了MgO负载量（质量分数），催化剂用量，温度（油浴温度）和反应时间对尿素水解反应的影响。结果发现：MgO/η-Al2O3具有较好的催化水解效果，尿素去除率随MgO负载量的增加逐渐增大，当负载量为14.29%时尿素去除率达到最大；采用14.29% MgO/η-Al2O3为催化剂，在温度为170 ℃，催化剂用量为40 g/L，反应时间为8 h的条件下，水解后的尿素含量为9.04 mg/L，达到了10 mg/L的排放要求。此外，重复利用性实验还表明MgO/η-Al2O3固体碱具有良好的稳定性。

Abstract:

MgO/η-Al2O3 solid base catalysts with η-Al2O3 as carrier were prepared and used for catalytic hydrolysis of urea in wastewater. X-ray diffraction and N2-BET techniques were applied to characterize the crystal structure and surface properties of catalysts, and back titration method was used to determine the basic sites amount. The effects of MgO loading amount (mass fraction), catalyst dosage, temperature of oil bath and reaction time on urea hydrolysis were respectively investigated. The results show that MgO/η-Al2O3 exhibits excellent catalytic activity for urea hydrolysis, and the urea removal rate increases with MgO loading amount and reaches the maximum when the loading amount is 14.29%. Under the condition of catalyst dosage of 40 g/L, temperature of 170 ℃ and reaction time of 8 h, a low urea concentration of 9.04 mg/L which has met the emission requirement (10 mg/L) is obtained by using 14.29% MgO/η-Al2O3 as catalyst. Furthermore, according to the results of stability tests, MgO/η-Al2O3 demonstrates a good recycling ability.