## 3 Results and Discussion  
### Structure and Textural of ZSM-23 Zeolites  
The XRD patterns of the different zeolites synthesized under different hydrothermal synthesis conditions are showed in Figure 1. All the samples present characteristic diffraction peaks of ZSM-23 [21], and no impurity phase is formed. The crystallinity of ZSM-23 zeolites synthesized with aluminum sulfate as silicon source is higher than that with aluminum nitrate as silicon source (Table 1). In addition, the ZS-1 has the highest crystallinity due to the low temperature pre-crystallization and SO\({}_{4}\)\({}^{2-}\) anions, which introduces more silicon into the framework of zeolite. It is well known that the use of different raw materials and crystallization methods in zeolite synthesis will result in products with significantly different crystal sizes and shapes. The SEM and TEM images of three ZSM-23 zeolites are shown in Figure 2. The ZS-1 is formed by sheet cross polymerization with a length of 600-900 nm. This is due to the formation of a lot of crystal nucleus during aging and then aggregation. Sample ZS-2 presents the typical needle-shaped morphology of MTT zeolites [21] with a size of about 60 nm in diameter and above 1 um in length. However, the sample ZN-1 shows the jujube core morphology, which is polymerized by lots of irregular flakes with length of about 40 nm. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Samples** & **Si/Al 1** & **Si/A 1 2** & **Si/Al 3** & **Pt Particle Size nm 4** & **Pt Dispersion 5** & **Relative Crystallinity 6** \% \\ \hline ZS-1 & 55 & 48.6 & 14.2 & 2.1 & 50.9 & 100 \\ ZS-2 & 55 & 46.2 & 13.8 & 2.5 & 42.4 & 97.2 \\ ZN-1 & 55 & 42.2 & 12.7 & 2.0 & 53.5 & 93.5 \\ \hline \hline \end{tabular}  
* Si/Al represent the ratios of Si/Al. 1 Obtained by feed ratio of initial solutions. 2 Calculated using ICP-OES.
* The value of Si/Al on the surface is obtained by XPS. 4 Obtained by chemical adsorption of CO. The average size of Pt particle was assumed to be uniform semispherical Pt particle. 5 Obtained by pulse adsorption of CO.
* Obtained by using ZS-1 (100%) as a standard.  
\end{table} 
Table 1: Textural properties of the different zeolites. Figure 1: XRD patterns of different samples. The textural properties of the zeolites obtained are shown in Table 1. Different samples have the same feed ratio of Si/Al, while all samples have higher surface aluminum content than body phase. However, the Si/Al ratio of body phase and the surface of the zeolite prepared from using aluminum sulfate as aluminum source are higher than that prepared from using aluminum nitrate as aluminum source. This may be due to the fact that the presence of the SO\({}_{4}\)\({}^{2-}\) inhibited the incorporation of Al [15] into the ZSM-23 framework. And the value of Si/Al on the surface of zeolite was determined by XPS. From the \({}^{27}\)Al MAS NMR spectra (Figure 3), it can be seen that an intense signal appears at 54 ppm in all the samples, which is assigned to the four-coordinating Al, and no Al signal belonging to the extra-framework is detected at 0 ppm. It is indicated that the Al atoms of ZSM-23 obtained by the three schemes are almost in the framework of zeolite. Figure 2: SEM and TEM images of the ZSM-23 zeolites. At P/P0 < 0.01, the adsorption amount of N\({}_{2}\) molecules increase dramatically, and exhibit a type IV N\({}_{2}\) isotherm, which show typical microporous structures (Figure 4). The increase of the curve at higher relative pressures is caused by the multi-layer adsorption of N\({}_{2}\) on the surface of the zeolite. Compared with the other two samples, the hysteretic ring of H-ZN-1 is larger, which is due to the increase of mesoporous in zeolite composed of small flake crystals, consistent with the SEM and TEM images. The basic properties of respective zeolite are shown in Table 2. The external surface area of H-ZS-2 is about 45.9 m\({}^{2}\)/g, which is lower than that of the other two samples as well as the lowest microporous volume, which is due to the regular needle-shaped morphology.