Precisely tailoring the location and strength of Brønsted acid is crucial for the catalytic cracking of polyolefins. Here, by simple sodium cation exchange ( x Na-USY, where x is the Na/Al ratio), it was unexpectedly discovered that x Na-USY ( x < 0.5) displayed a lower cracking temperature of polypropylene (PP) with optimum performance and excellent reproducibility at x = 0.38, rather than pure H-USY, as generally believed. Combining spectroscopic and microstructural characterizations, a putative mechanism was proposed from the perspective of proton location and acid strength. When lacking strong Brønsted acid near site II, PP tended to cleave into longer alkane fractions at low temperatures and volatilized directly, exhibiting significant apparent cracking capacity. Meanwhile, the lower distribution of olefins and aromatics remarkably reduced coke generation at high temperatures. These findings not only shed light on the optimization of plastic degradation catalysts but also expand our knowledge of the zeolitic acid-catalyzed cracking process.
Jing Liu,Yuena Ge,Yueqin Song,Ming Du,Xiaolong Zhou,Jin'An Wang
This work reports a new technical approach for the production of aviation gasoline through the catalytic dimerization of iso-butene on sodium exchanged Amberlyst-15 resins (20–40 mesh) in the absence of selectivity-enhancing components at T = 50 °C, P = 2 MPa and LHSV of 2 h −1 . The dimers selectivity could be significantly improved by effectively controlling the acid capacity of resins via Na + exchange. When the acid capacity of the catalyst was controlled to <2.45 mmol/g, the 2,4,4-trimethylpentenecontent in C8 olefins reached ~100%. It was also confirmed that the sodium exchanged resins have longer lifetime than Amberlyst-15 resins.
危险品化学品经营许可证（带存储）