氨水改性氧化石墨烯高效催化Knoevenagel缩合反应

Highly Efficient Aqueous Ammonia Modified Graphene Oxide for Knoevenagel Condensation

通过浸渍法制备了氨水改性氧化石墨烯，考察了其在苯甲醛和丙二腈的Knoevenagel缩合反应中的催化性能。通过X射线粉末衍射（XRD）、拉曼光谱（Raman）、傅里叶变换红外光谱（FTIR）、NH3程序升温脱附（NH3-TPD）、元素分析等对催化剂进行了表征，考察了工艺条件对其催化剂性能的影响。结果表明：氨水改性氧化石墨烯可以有效地将NH＋4固载于氧化石墨烯表面；氧化石墨烯经氨水改性后在苯甲醛和丙二腈的Knoevenagel缩合反应中表现出良好的催化性能，随着改性实验中氨水质量分数的增加，催化剂的活性不断增加。以质量分数5％的氨水为改性剂制备的催化剂（AW-GO-5％）在60℃、4h下催化苯甲醛和丙二腈的Knoevenagel缩合反应，苯甲醛的转化率高达93．6％，产物苄亚基丙二腈的选择性为94．8％，该催化剂重复使用4次后催化活性仍较高。

A series of aqueous ammonia modified graphene oxide samples were prepared by impregnation method and used to catalyze Knoevenagel condensation reaction between benzaldehyde and malononitrile. The prepared materials were characterized by X-ray diffraction, Raman spectra, Fourier transform infrared spectroscopy, NH3-TPD and elemental analysis. Moreover, the influence of technological conditions on the performance of catalyst was investigated. The results indicated that NH~ was successfully immobilized on the surface of graphene oxide. The aqueous ammonia modified graphene oxide samples exhibited excellent catalytic performances in the Knoevenagel condensation reaction between benzaldehyde and malononitrile. The catalytic activity increased gradually with increasing the concentration of aqueous ammonia. 93.6% benzaldehyde conversion and 94.8% benzylidene malononitrile selectivity were obtained when the reaction was carried out at 60 ℃ for 4 h in the presence of aqueous ammonia （5% mass fraction） modified graphene oxide （AW-GO-5%）. Catalytic activity was still excellent after the AW-GO-5% catalyst could be recycled four times.