## 3 Result and Discussion
### Catalyst Morphology
The results of SEM-mapping surface images of the Ni-Z3, Ni-Z5, and Ni-Z7 catalysts in Figure 4 show that the Ni is homogeneously distributed on the Z carrier surface. There are no significant differences among metal distribution on Ni-Z3, Ni-Z5, and Ni-Z7 catalysts. Si and Al are observed to be the main components of catalysts. These components are distributed in the same areas and they form chunks that indicate zeolite existence. Moreover, Ni metal mapping shows that Ni is spread evenly in all areas rather than just being concentrated in one certain place. With this result, Ni metal has successfully been exchanged and impregnated in the catalyst structure or surface. Meanwhile, to confirm the loading of nickel onto the Z catalysts, the EDS test was conducted, the results of which can be seen in Table 2. Based on Table 2, the amount of Ni metal that is exposed to each catalyst of Ni-Z3, Ni-Z5, and Ni-Z7 was 0.98%, 1.11%, and 1.48%, respectively. This value is still in accordance with theoretical calculations for the Ni metal that is embedded by \(\pm\)1%. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{3}{c}{**Mass (\%)**} \\ \cline{2-4}  & **Ni-Z3** & **Ni-Z5** & **Ni-Z7** \\ \hline C & 29.69 & 12.69 & 20.27 \\ O & 42.39 & 52.15 & 45.02 \\ Si & 18.58 & 23.80 & 27.38 \\ Al & 4.60 & 5.72 & 3.49 \\ Ni & 0.98 & 1.11 & 1.48 \\ S & 0.55 & - & 0.80 \\ K & 0.30 & 1.57 & 0.66 \\ Fe & 1.87 & 1.90 & - \\ Zn & 1.09 & - & - \\ Na & - & 0.48 & - \\ Mg & - & 0.58 & - \\ Ti & - & - & 0.90 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The comparison of Si, Al, and Ni elements in Ni-Z3, Ni-Z5, and Ni-Z7. Figure 3: Catalyst surface morphology at 1000\(\times\) magnification of (**a**) Ni-Z3, (**b**) Ni-Z5, and(**c**) Ni-Z7. Based on Table 3 above, it can be observed that the activation treatment with different acid concentrations produces different specific surface area characteristics, volume pores, and average radius pores. Z7 catalyst has a larger surface area, total pore volume, and pore network compared to Z, Z3, and Z5. Acid was used to clean both crystalline and amorphous impurities that covered the zeolite pores. The activation process, with a concentration of 7 M HCl, was able to optimally dissolve and remove metal oxides from Fe, F, Ca Mg, and Ti, which are absorbed and cover the surface of zeolite, while also being able to optimize the amount of aluminum in the tetrahedral zeolite framework. Therefore, the Z7 catalyst has high surface and thermal stability. The zeolite dealumination due to acid treatment only releases inactive skeleton aluminum, so that the increased amount of aluminum produces Bronsted and Lewis acid sites, which are very important for catalytic processes. Meanwhile, the influence of metal loading on each catalyst can be seen to give the Ni-Z7 catalyst a greater surface area and the total pore volume compared to Ni-Z3 and Ni-Z5. This shows that the loading of Ni-Z7 metal was more homogeneously distributed on the surface and pore of the catalyst. Different results are shown by Ni-Z3 and Ni-Z5 catalysts, where metal loading results in decreased catalyst surface areas. This is due to the inhomogeneous distribution of metals, which results in the closure of the small zeolite pore. As a result, the surface area and pore volume of the catalyst decrease, and the pore size distribution shifts to a larger pore diameter. Uneven metal dispersion is strongly influenced by the nonuniform shape of the zeolite carrier surface. These results are consistent with the results of SEM and EDS characterization, which show that Z7 has a smoother and more uniform surface morphology. The Z3, Z5, Ni-Z3, Ni-Z5, and Ni-Z7 catalysts are included in the micropore type, with a pore size of \(<\)2 nm. Meanwhile, the Z7 catalyst is included in the mesoporous type, with a pore size of \(>\)2 nm.