摘要
用浸渍法制备了Ni/SAPO-5分子筛、Ni/AlPO_4-5分子筛和Ni/AlPO_4胶体三种催化剂, 并进行了它们的IR、TFD、EPR以及活性测试。实验结果表明:SAPO-5、AlPO_4-5和 AlPO_4胶体都具有L酸中心和B酸中心,且以I酸为主。三种载体载镍经氢气还原后, Ni/SAPO-5(R)和Ni/AlPO_4-5(R)的B酸增多,而Ni/AlPO_4胶体(R)的B酸几乎全 部消失。这与TPD测得的结果一致。对照它们的催化裂化活性大小,证实B酸位为裂化反应 的活性中心。由EPR测试结果又证实了Ni^0也是裂化反应的活性中心。由于Ni^0与强酸性 载体AlPO_4胶体的相互作用,致使Ni/AlPO_4胶体(R)的裂化活性低于Ni/AlPO_4-5(R)。
Ni/SAPO-5, Ni/AlPO4-5 and Ni/AlPO4 gel catalysts were prepared by the impregnation method, and characterized by IR, TPD, EPR as well as their activity determination for n-hexane cracking. The results showed that they contained both Lewis acid site and Bronsted acid site with the former predominant. After the reduction in hydrogen stream, Bronsled acid of Ni/SAPG-5(R) and Ni/AlPO4-5(R) were enhanced, while the B acid of Ni/AlPO4 gel(R) almost disappeared. These results were in agreement with those obtained by TPD.Conforming to (he catalytic cracking activity of these catalysts, Bronsted acid site -was confirmed to be the active center responsible for cracking reaction. EPR results showed that Ni0 was also the active ccntei for cracking. Due to the interaction between Ni0 and the strong acidic support A1PO4 gel, the cracking activity of Ni/AlPO4 gel(R) was lower than that of Ni/AlPO4-5(R).
