自粘结低硅铝X型沸石的结构、吸附和N_2/O_2分离比

用原位合成方法直接将高岭土转化为所需形状的低硅X型沸石(PLSX),经X衍射,~(29)Si,~(27)AI MAS NMR谱证实PLSX的结构硅铝比接近1,它含LSX的组成为40.40%,含4A的组成为17.92%,其余为无定形硅、铝氧化物.LSX的骨架硅铝比接近1,是骨架负电荷分配最均匀的X型沸石,293K时静态法测定和推算ISX的饱和吸附水达39.80wt%,LSX的组成为Na(96-x)K_x(Al_(96)S_i(96)O_(384))·310H_2O,是吸附量高、价廉的吸水剂.PLSX对空气中氮氧的分离系数为α(N_2/O_2)=3.15,高于用于PSA的商品5A的α(N_2/O_2)=2.33和已报道的13X的α(N_2/O_2)=2.36.PLSX也是一种极好的吸附分离剂.

Characterization of Structural Composition,Adsorption Capacity, N_2/O_2 Separation for an In Situ Crystallization PLSX Zeolite

The PLSX (Pillard X Zeolite with lowest ratio of silicon to aluminum) has been made directly from calcined pillard Kaolin (i.e. metakaolin with pillard shape) as starting material by an in situ crystallization in the caustic solution. On the base of the measurement, by XRD, MAS NMR and water adsorption etc. method, it is shown that the PLSX contained 40.40% LSX (Lowest ratio of silicon to aluminum) zeolite whose composition is Na96-xKx(Si96Al96O384) 310H2O; 17.92% of it is 4A zeolite and other amorphous composition, i.e. silica and alumina. That the framework Si/Al of LSX zeolite equals to 1 results in the equal distribution of negative charges on the zeolite framework. The equilibrium content of water adsorption in the steam of saturation water solution of CaCl2 at 293K for LSX is 39.81wt%. The above results show that the LSX as water absorbent is cheap in cost and high in adsorption capacity. The a (separation faction) of PLSX zeolite for N2/O2 separation in the air is 3.15 which is larger than the 2.33 of the commercial 5A zeolite being used as PSA adsorption of air separation and also larger than 2. 36 of a of 13X zeolite reported. So. Therefore, the PLSX is an excellent absorbent in separation of air