化学改性对催化裂化催化剂氢转移性能的影响

 研究了用草酸处理裂化催化剂的活性组分USY型分子筛以及在催化剂基质中添加磷改性的氧化铝等方法对裂化催化剂氢转移反应活性的影响. 实验结果表明,酸处理能脱除USY型分子筛孔道中的无定形氧化铝,疏通分子筛孔道,提高分子筛的氢转移反应活性,减少积碳; 对于含稀土的REUSY型分子筛,酸处理首先脱除的是稀土离子,降低了分子筛的裂化反应活性,但提高了氢转移反应活性. 在催化剂基质中添加磷改性的氧化铝能增加基质的弱酸性中心,增加裂化反应的活性中心,提高催化剂的裂化及氢转移反应活性,同时减少催化剂上的积碳.     

Computational study of the decomposition mechanisms of ammonium dinitramide in the gas phase

CBS-QB3 method has been employed to determine the geometries, the vibrational frequencies of the reactants, the products and the transition states involved in intramolecular hydrogen-transfer and decomposition reactions of the free gas-phase H₃N···HN(NO₂)₂ (ADN^*). The results show that the intramolecular hydrogen-transfer reaction of ADN^* is more feasible than that of HDN. ADN^* and its hydrogen-transfer isomers ADN^*-IIa,b,c decompose along four channels to form NH₃ + HONO + 2NO (P_I), ?H + ?O₃ + N₂ + NH₃ (P_II), ?H + ?O₂ + N₂O + NH₃ (P_III), and HNO₃ + N₂O + NH₃ (P_IV), respectively. It has been found that the dominant decomposition channels are P_I and P_III. The hydrogen-transfer reaction can reduce the barrier of elimination of NO₂ and forming N₂O reactions in ADN^* and HDN. The decomposition of ADN^*-IIc to form NO₂ and N₂O is more feasible than that of the gas-phase HDN. The rate constants (k) of rate-determining step of ADN^* show that k_PI and k_PIII are higher than k_PIV and k_PII. Compared with HDN-IIc → N₂O+?H+?O₂, k_PIII of ADN^*-IIc is significantly higher than that of k^HDN-IIc. These results reveal that NH₃ (as a chaperon) has a certain influence on the decomposition mechanisms and kinetics of ADN^*.     

稳定同位素方法研究模型化合物之间的氢转移反应

二十烷,菲作为模型化合物,以四氢萘为供氢剂,在临氮及临氢体系中应用氘代四氢萘考察供氢剂的氢转移反应,发现供氢剂抑制烷烃的裂化,其作用是通过脱氢湮灭自由基来抑制裂化反应。临氮及临氢条件下,与正二十烷与菲的二元体系相比,正二十烷,菲和四氢萘三元体系中四氢萘不仅能生成较多的菲的氢化芳烃产物,而且稳定同位素方法表明氘代四氢萘可以向菲和菲的氢化芳烃产物转移更多的氘,同时发现H12－四氢萘和D12－四氢萘的供氢（氘）率上存在着动力学同位素效应。