高比表面积Cr2O3-α-AIF3催化剂的制备和应用

摘要

A high specific surface area Cr2O3-α-AIF3 catalyst was prepared using a carbon hard template method.The synthesis procedure consisted of three consecutive steps:(1) the impregnation of a sucrose (C12H22O11) aqueous solution with Cr2O3-y-Al2O3 and subsequent thermal treatment; (2) the thermal treatment of the obtained solid with HF,C@Cr2O3-y-AI2O3 can be completely transformed into C@Cr2O3-y-AIF3 at 400 ℃ with hydrogen fluoride; (3) the removal of the carbon template in C@Cr2O3-y-AIF3 upon high temperature combustion giving the high surface area Cr2O3-y-AIF3 (115 m2· g-1).The catalysts were characterized by X-ray diffraction (XRD),N2 physisorption,ammonia temperatureprogrammed desorption (NH3-TPD),transmission electron microscopy (TEM),scanning electron microscopy (SEM),and energy dispersion X-ray (EDX) techniques.We found that the fluorination process was crucial for the resulting Cr2O3-α-AIF3 with a high specific surface area of 115 m2· g-1 under optimal conditions.The Cr2O3-α-AIF3 catalyst with a high specific surface area was more active for the decomposition of 1,1-difluoroethane than the catalyst prepared by the direct fluorination of Cr2O3-y-AI2O3,because it contained a higher amount of acid sites.%采用炭硬模板法制备了高比表面积Cr2O3-α-AIF3催化剂.该催化剂的合成过程主要包括三步:(1)将一定浓度的蔗糖溶液浸渍到Cr203-y-Al2O3中,然后经过热处理,使得蔗糖分解为炭；(2)将含炭的Cr2O3-y-Al2O3固体在400℃用HF气体进行完全氟化;(3)在高温下利用燃烧法除去炭硬模板.对所制备的催化剂进行了X射线衍射(XRD),氮气吸脱附曲线,氨气程序升温脱附(NH3-TPD),透射电镜(TEM),扫描电镜(SEM)和X射线能量散射(EDX)技术表征.结果表明,氟化过程对Cr2O3-α-AIF3催化剂比表面积有重要影响,在最佳实验条件下,能够得到比表面积为115 m2·g-1的催化剂.此催化剂对催化裂解二氟乙烷(HFC-152a)制备氟乙烯(VF)的催化活性明显高于直接氟化制备的Cr2O3-α-AIF3催化剂,这是因为高比表面积的Cr2O3-α-AIF3催化剂具有较大的酸量.