HZSM-5分子筛的磷改性及其在加氢蜡油裂化中的性能研究

Study on phosphorus modification of HZSM-5 zeolite and its performance in hydrowaxter cracking

关键词:  浸渍  磷改性  HZSM-5  活性  选择性

Key words:  impregnation  phosphorus modification  HZSM-5  activity  selectivity

摘要:

通过浸渍法制备了系列磷改性的HZSM-5分子筛,利用X射线衍射、N₂物理吸附、X射线荧光光谱分析、NH₃程序升温脱附、吡啶吸附的红外光谱等方法对其进行表征,并考察了不同磷含量的HZSM-5分子筛的结构、酸性及其在加氢蜡油裂化方面的影响规律。结果 表明,随着磷含量的增加,其B酸性位减少,孔容及比表面积均有所降低。由于强B酸性位的降低抑制了氢转移反应,因此轻烯烃的选择性提高。因改性后的HZSM-5分子筛孔道堵塞,随着磷含量的增加,其活性降低明显,从而使丙烯收率呈现先升高后降低的趋势,当磷质量分数为5%时,丙烯收率最高可达5.9%。在多产丙烯助剂开发过程中,考查合适的磷含量尤为重要。 

Abstract:

A series of phosphorus modified HZSM-5 molecular sieves are prepared by impregnation method. X-ray diffraction (XRD), N₂ physical adsorption, X-ray fluorescence spectrometry, NH₃ temperature-programmed desorption, and infrared spectra of pyridine adsorption methods are used for its characterization and the different phosphorus content of HZSM-5 molecular sieve structure, acidity and the influence law on hydrogenation wax cracking are examined. The results show that with the increase of phosphorus content, the B acid site decreases, and the pore volume and specific surface area decreases. The selectivity of light olefins increases due to the decrease of strong B acid site which inhibited hydrogen transfer reaction. As the modified HZSM-5 molecular sieve pore is blocked, its activity decreases significantly with the increase of phosphorus content. Therefore, the yield of propylene presents a trend of first increasing and then decreasing. When phosphorus mass fraction is 5%, propylene yield can be up to 5.9%. It is particularly important to check the appropriate phosphorus content during the development of the productive propylene additive.