## 3 Result and Discussion  
### Catalyst Morphology  
SEM analysis was conducted to determine the changes in zeolite surface topology due to acid activation treatment. The results of SEM photographs, with 1000 times magnification for each catalyst, are presented in Figure 2. Figure 2a shows the surface topology of Z without the acid activation treatment, indicating an irregular grain shape. The Z surface morphology looks heterogeneous, and a contaminant seems to cover the pores. In particular, the comparison of zeolite surface topology after acid activation is given in Figure 2b-d. In Figure 2b, Z3 produces a more uniform surface topology, and the presence of granules tends to be cubic, while in Figure 2c,d, the catalysts Z5 and Z7 show a more uniform surface topology, with finer grains, and tend to be flat or slab. To conclude, increasing acid concentration will give more uniform morphology as the activation with HCl can remove both crystalline and amorphous impurities that cover the zeolite pores. Acid activation and calcination treatments indicate the formation of smaller grain, as well as giving a uniform surface of zeolite. [PERSON] et al. [23] have reported that Malang natural zeolite that has undergone a dealumination and calcination process showed smaller grain and uniform morphology. However, there is no confirmation of zeolite structure changes. The same result was reported by [PERSON] et al. [21], describing that surface morphology of the Sarulla natural zeolite after the activation and calcination process became finer and more uniform. Figure 1: Hydrodeoxygenation (HDO) process scheme. Note: (1) sample bottom flask; (2) thermometer; (3) condenser; (4) reactor; (5) hydrogen gas tank; (6) heater. Figure 2: _Cont._Chemical compositions of Sarulla natural zeolite were also observed (Table 1). Based on Table 1, the main components of Sarulla natural zeolite (Z) were found to be O, Si, Mg, and Al. After dealumination, Si content increased by 70%, while Al content decreased by 30%. This indicates that the use of acid was able to increase Si and remove the impurities that cover the surface and pore zeolites, resulting in a more porous and homogeneous morphology. The acid activation and calcination allow carbon deposition to occur during the acid activation process, and the acid density used influences the content of carbon formed. This is possible since the natural zeolite raw material already contains carbon as an organic impurity, both crystalline and amorphous, that exists on the surface of the pores, or trapped inside the pores, even though in very small amounts. The activation of acid causes most of these impurities to emerge from the opening of the pores and allows the formation of carbon deposits during the process. The same results have also been reported by [PERSON] et al. [24], where EDS data show Bayah natural zeolite has a carbon level of 13.83%, which even increases after the activation process with HCl acid to 30-36%. Based on the surface morphology of nickel loaded on the zeolite catalyst (Figure 3), the crystal size change is more homogenous, indicating the absence of a sintering process. The distribution of Ni metal dispersed on the surface of the catalyst, analyzed by SEM-mapping, is described in Figure 4. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Elements**} & \multicolumn{4}{c}{**Mass (\%)**} \\ \cline{2-5}  & **Z** & **Z3** & **Z5** & **Z7** \\ \hline C & - & 23.25 & 2.68 & 20.27 \\ O & 61.58 & 49.08 & 60.81 & 71.01 \\ Si & 15.73 & 23.72 & 25.35 & 23.74 \\ Al & 5.64 & 3.45 & 0.90 & 3.79 \\ K & 3.16 & - & - & 0.98 \\ Fe & 4.60 & - & - & - \\ F & - & - & 1.28 & - \\ Ca & - & 0.50 & 4.52 & - \\ Mg & 7.93 & - & 4.47 & - \\ Ti & 1.37 & - & - & - \\ Hg & - & - & - & 0.48 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Catalyst chemical compositions based on scanning electron microscope and energy-dispersive x-ray spectroscopy (SEM-EDX) data. Figure 2: SEM morphology at 100 times magnification for catalysts of (**a**) Z, (**b**) Z3, (**c**) Z5, and (**d**) Z7.