Synthesis Of Mesoporous NaA Zeolite By Multiwall Carbon Nanotubes Templating

Zeolites with uniform microporous and pore size of molecular size are a class of sorbent or film-like material. Its diameter ranges from4A to12A, such as Y-type, ZSM-5zeolite. In petrochemical, fine chemicals and biochemical engineering areas, there are often some large molecules with their dynamics diameters larger than the pore size of zeolites, which make the reaction can’t proceed. Mesoporous zeolites improve the situation and expand the field of application of zeolites through changing the pore system to allow more large molecular to access the inner of zeolite.In this paper, the multiwall carbon nanotubes, which involve MWNTs-none, MWNTs-COOH and MWNTs-OH, was used as template agents to synthesize mesoporous NaA zeolite by hydrothermal method. The silane coupling agent was brought in to treat the MWNTs-OH, in order to improve the BET surface area. The conclusions are as follows:1. The crystallinity of mesoporous NaA zeolite is not varied with the different MWNTs-none amount. What’more, the mixing temperature and mixing time of MWNTs-none and Na2Si03does not affect the degree of crystallinity of the samples. The maximum BET surface area of sample is about10m2/g, which is larger than that of microporous NaA zeolite (about3.4m2/g). And, the pore size distribution ranges from5～50nm.2. The crystallinity of mesoporous NaA zeolite is not changed with the different MWNTs-COOH amount. What’more, the mixing temperature and mixing time of MWNTs-COOH and Na2Si03does not affect the degree of crystallinity of the samples. The maximum BET surface area of sample is about16.8m2/g, which is larger than that of samples by MWNTs-none templating. And, the pore size distribution ranging from10-30nm is more narrow than samples by MWNTs-none templating.3. The crystallinity of mesoporous NaA zeolite is not varied with the different MWNTs-OH amount. What’more, the mixing temperature and mixing time of MWNTs-OH and Na2Si03does not affect the degree of crystallinity of the samples. The maximum BET surface area of sample is about17.8m2/g, which is close to that of samples by MWNTs-COOH templating. And, the pore size distribution ranging from10-30nm is similar with that of samples by MWNTs-COOH templating.4. By contrast, it can be seen that the sample by MWNTs-OH templating has the largest BET surface area. It indicates the functionalized MWNTs can increase the sample BET surface area. The samples by MWNTs-COOH and MWNTs-OH templating have close BET surface areas, which suggests that the two have similar ability to make pores in zeolite. 5. The crystallinity is not affected for the amount of MWNTs-OH treated with KH-560and the mixing temperature or mixing time of MWNTs-OH and Na2SiO3. However, the sample BET surface area will be cut down with the increase of concentration of KH-560aqueous solution, and the maximal BET surface area is about13.7m2/g. That is maybe the alkoxy activity of KH-560is weaker than the surface hydroxyl of MWNTs-OH. So the more covered by KH-560on the surface, the weaker of the activity of MWNTs-OH. Finally, the BET surface area is deduced.6. The KH-660and the mixing temperature and mixing time of KH-660, MWNTs-OH and Na2SiO3almost don’t affect the degree of crystallinity of the mesoporous NaA zeolite zeolite. The KH-660does not affect the BET surface area, it is maybe the activity of KH-660is similar with that of MWNTs-OH, which make them have similar ability to form mesoporous.7. The crystallinity of mesoporous NaA zolite with polymer of KH-560and KH-660bridged MWNTs-OH as templates does not changed with conversion in mixing conditions. The maximum BET surface area of samples is about24.3m2/g, which is larger than that by KH-560or KH-660treating. That is because the KH-560and KH-660have reacted to enhance the binding force, so the MWNTs-OH can be encapsulated in zeolite crystal more.