Y型沸石钙交换过程及机理研究

STUDY ON THE PROCESS OF Y ZEOLITE EXCHANGED WITH CALCIUM

采用PASCA、NMR、IR等技术研究NaY沸石钙交换过程及机理.结果表明,NaY沸石中引入钙离子(钙交换度>20%时)并在水蒸气气氛中焙烧,可导致沸石骨架中产生非骨架铝(NFAl)和大量平均孔直径达到18nm的二次孔道(SP).产生最大数量的NFAl和产生最多SP的最佳交换度为60%,此时CaNaY沸石中含有最大量的B酸和最大量的L酸.结果还表明,在钙交换过程中,钙必须以Ca^(2+)离子的形式交换在NaY沸石骨架上,因此,交换过程中控制好浆液的pH值是必要的,最佳pH值为5.5.CaNaY沸石的最佳水热处理温度为550℃.

PASCA (Positron annihilation spectroscopy for chemical analysis), NMR and IRwere used to study the process and also the mechanism of NaY zeolite exchanged with calci-um. The results indicate that the introduction of Ca2+ ions into the zeolite framework (withan exchange degree>20% ) combined with calcination under steam resulted in the formationof non-frame-work aluminium (NFAl) and a large number of secondary pores (SP) with thepore size up to 18 nm. The optimum degree of Ca2+ exehange for producing maximum amountof NFAl and SP was 60%, meanwhile, the CaNaY zeolite reached its maximum of B(Bronsted)and L (Lewis)acids. It is necessary to control the pH value of the exchange slurry,and the optimum pH value of Ca2+ ion exchange was 5. 5. The optimum calcination tempera-ture for CaNaY was 550℃.