硫酸铝催化剂在强温室气体1,1-二氟乙烷气相催化裂解脱HF反应中的性能研究

Application of aluminum sulphate catalysts in the gas-phase catalytic cracking of potent greenhouse gas 1,1-difluoroethane

通过评价系列硫酸盐催化剂对1,1-二氟乙烷(HFC-152a)气相催化裂解脱HF反应的催化活性,筛选出活性最优的硫酸铝催化剂,并采用热失重分析(TG-DTG)、X射线衍射(XRD)、扫描电镜(SEM)、N2物理吸附-脱附(BET)、吡啶红外(Py-IR)等手段对不同焙烧温度处理硫酸铝催化剂进行表征.结果表明,通过对比不同焙烧温度的硫酸铝催化剂发现结晶水含量对催化活性有抑制作用.反应后的催化剂具有更高的Lewis酸量,一方面是由于脱出结晶水有助于增加Al物种不饱和配位点,而其中部分不饱和位点被F物种占据,进而有助于增强Lewis酸性;另一方面,催化剂表面Brønsted酸位点同样易被F物种取代,具有一定的刻蚀作用,所以在增加Lewis酸量的同时,也增加了催化剂的比表面积,提高反应分子与活性位点的接触机率.最后通过采用原位红外表征(In-situ DRIFTS)研究硫酸铝催化剂在HFC-152a气相催化裂解中的催化机理.

The catalytic activity of series sulfate catalysts for the gas-phase catalytic cracking of 1,1-difluoroethane(HFC-152a)was evaluated,and the aluminum sulfate catalysts exhibited the optimal activity.The catalytic properties of aluminum sulfate catalysts were characterized by thermal weight loss analysis(TG-DTG),X-ray diffraction(XRD),scanning electron microscopy(SEM),N2 adsorption-desorption,pyridine infrared(Py-IR).Comparation the catalytic activity of series aluminum sulfate treated with different calcination temperatures,the results showed that crystalline water had an opposite impact on the activity.Moreover,the spent catalysts had higher Lewis acid sites compared with fresh catalysts.On the one hand,the removal of crystalline water helped to increase the unsaturated coordination sites of aluminum species,then some of these unsaturated sites were occupied by fluorine species,which in turn helped to enhance the Lewis acidity of Al species;on the other hand,the Brønsted acid sites on the surface of catalyst were also susceptible to replace by fluorine species,which had a certain etching effect.Accordingly,the amount of Lewis acid sites as well as the specific surface area of the catalyst were improved,increasing the chance of contact between the reacting molecules and the active sites.Lastly,the catalytic mechanism of HFC-152a gas-phase catalytic cracking over aluminum sulfate catalyst was revealed by in-situ infrared characterization(In-situ DRIFTS).