## 3 Result and Discussion
### Catalyst Crystallinity  
The influence of acid activation and calcination on zeolite crystallite can be observed from the change of intensity at 2\(\theta\) angle by the changes of its peak intensity. The presence of the crystalline phase of zeolite is indicated by the sharp peaks in the diffractograms at 2\(\theta\) areas among 18\({}^{\circ}\)-28\({}^{\circ}\)[26]. Natural zeolite of Sarulla is a modern type of zeolite [21]. The \(Z\) diffractogram is shown in Figure 6 and the intensity values at the same 2\(\theta\) (degree) angle are presented in Table 4.  
Table 4 shows the comparison of intensity values at the same 2\(\theta\) (degree) angle. The Z3 catalyst has got the highest crystallinity compared to Z, Z5, and Z7. The rise of the intensity is due to acid activation, which can remove contaminants that cover the zeolite surface. As a result, the solid is cleaner, hence the increase of crystallinity. [PERSON] and [PERSON] [27] reported that the interaction of acid on the surface of zeolite would lead to the release of alumina species from zeolites. H\({}^{+}\) ions in the  
Figure 5: N\({}_{2}\) gas adsorption–desorption isotherm comparison graph of Z, Z3, Z5, Z7, Ni-Z3, Ni-Z5, and Ni-Z7. Figure 6: XRD diffractogram comparison of Z, Z3, Z5, and Z7. acid affect the free electrons in atom O to form coordination bonds. The Al-O group lacks electrons and will be more polar but less strong than before, so Al breaks from its bond. The same thing was reported by [PERSON] et al. [28], who stated that the dealumination of zeolite with HCl 3 M led to a cleaner zeolite surface and pores, as well as the increase of crystallinity. Dealumination causes the release of aluminum from the tetrahedral zeolite structure. Furthermore, crystal grain size can be obtained from XRD data, calculated by the Debye-Scherrer equation [29]. Based on Table 5, it can be seen that the Z7 catalyst has the largest crystal size, between 35-41 nm. Ni metal impregnated in catalysts Ni-Z3, Ni-Z5, and Ni-Z7 was detected at \(2\theta=62.52^{\circ}\), \(62.32^{\circ}\), and \(62.80^{\circ}\), respectively. The data align with a report from [PERSON] et al. [30], where Ni metal was detected at \(2\theta=62.90^{\circ}\). The XRD diffractogram and the calculation of the crystallinity degree of the Ni-Z catalyst are described in Figure 7 and Table 6 respectively. Ni-Z3 has got the highest crystallinity at 46.76%, while its lowest crystallinity is 34.15%. The hydrochloric acid 3 M activation step in Ni-Z3 has removed the contaminants on the zeolite surface. A cleaner zeolite surface gives higher intensity as X-ray diffraction is not blocked by any impurities [31]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Ni-Z3**} & \multicolumn{2}{c}{**Ni-Z5**} & \multicolumn{2}{c}{**Ni-Z7**} \\ \hline \hline
**2\(\theta\) (degree)** & **Intensity** & **2\(\theta\) (degree)** & **Intensity** & **2\(\theta\) (degree)** & **Intensity** \\ \hline
19.90 & 46 & 19.56 & 19 & 19.77 & 20 \\
21.12 & 59 & 21.42 & 23 & 21.88 & 60 \\
23.62 & 59 & 23.73 & 74 & 23.52 & 54 \\
27.78 & 248 & 27.89 & 228 & 27.79 & 163 \\
30.31 & 46 & 30.46 & 61 & 30.24 & 32 \\
**Crystallinity** & 46.76\% & **Crystallinity** & 42.49\% & **Crystallinity** & 34.15\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: 2\(\theta\) (degree) peak intensity comparison of Ni-Z3, Ni-Z5, and Ni-Z7 diffractograms. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Z**} & \multicolumn{2}{c}{**Z3**} & \multicolumn{2}{c}{**Z5**} & \multicolumn{2}{c}{**Z7**} \\ \hline \hline
**2\(\theta\)** & **Intensity** & **2\(\theta\)** & **Intensity** & **2\(\theta\)** & **Intensity** & **2\(\theta\)** & **Intensity** \\ \hline
22.03 & 83 & 21.97 & 70 & 21.88 & 98 & 22.02 & 124 \\
23.72 & 74 & 23.66 & 77 & 23.58 & 92 & 23.71 & 121 \\
27.93 & 196 & 27.85 & 238 & 27.71 & 215 & 27.64 & 246 \\
30.43 & 42 & 30.37 & 131 & 30.26 & 42 & 30.3 Catalyst activation by using hydrochloric acid of 5 and 7 mol/L leads to lower crystallinity.