## 3 Results and Discussion  
### Catalyst Characterization  
XRD pattern of the as-prepared Ni-Fe/Al\({}_{2}\)O\({}_{3}\) catalyst is illustrated in Figure 2A. The peaks at around 45.0\({}^{\circ}\) and 65.6\({}^{\circ}\) are assigned to spinel NiAl\({}_{2}\)O\({}_{4}\). In addition, the peaks at 30.3\({}^{\circ}\) and 43.4\({}^{\circ}\) are attributed to spinel NiFe\({}_{2}\)O\({}_{4}\) and the peaks at 37.4\({}^{\circ}\), 46.1\({}^{\circ}\), and 66.9\({}^{\circ}\) are related to \(\gamma\)-Al\({}_{2}\)O\({}_{3}\)[17].  
Figure 2B represents the FTIR spectra of Ni-Fe/Al\({}_{2}\)O\({}_{3}\) catalyst. The absorption bands at 3406 cm\({}^{-1}\) and 1643 cm\({}^{-1}\) are related to the stretching vibration of the physically adsorbed water on the sample surface [18]. A strong infrared absorption band appears in the 400 to 1000 cm\({}^{-1}\) region, which is attributed to the vibrational absorption of Al-O in the carrier Al\({}_{2}\)O\({}_{3}\)[17; 18].  
N\({}_{2}\) adsorption-desorption analysis was conducted to examine the textural characteristics of the synthesized catalyst. The catalyst displays type IV isotherms accompanied by a H3-type hysteresis loop (Figure 2C), indicating the presence of a mesoporous structure within the composite [19]. As a result, the texture of the prepared catalysts consists of plate-like structures featuring slit-shaped pores. Additionally, the significant rise in adsorption near P/P\({}_{0}\) = 1 suggests the presence of a large-sized mesoporous structure within the catalysts. Furthermore, the pore size distribution for each sample, determined using the BJH method, is displayed in Figure 2D. As demonstrated, all the synthesized catalysts exhibit a narrow pore size distribution primarily ranging from 2 to 30 nm, confirming their mesoporous nature. The BET surface area of the Ni-Fe/Al\({}_{2}\)O\({}_{3}\) was 161.5 m\({}^{2}\)/g with total pore volume and average pore diameter of 0.56 cm\({}^{3}\)/g and 13.9 nm, respectively. The obtained high surface area of prepared catalyst can effectively improve the adsorption of reactant on the surface of the catalyst. Therefore, there will be more active sites to proceed the reaction.  
The nominal and experimentally determined metal loadings for Fe/Al2O3, Ni/Al2O3, and Ni-Fe/Al2O3 catalysts are comprehensively presented in Table 1, providing a direct comparative analysis of intended and realized metal incorporation.  
The minimal discrepancy between the nominal and experimental metal loadings, as determined by ICP-OES, underscores the effectiveness of the synthesis method.  
To evaluate the acidic characteristics of the newly prepared catalytic materials, temperature-programmed desorption of ammonia (NH3-TPD) was performed. The quantity of ammonia retained by the acidic locations on each catalyst was quantified, with the results presented in Table 2. It was observed that the incorporation of metals onto the alumina (Al2O3) support led to a substantial decrease, exceeding 50%, in the over  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Catalyst** & **Nominal Loading (\(wtwt\)) \%** & **Experimental Loading (\(wtwt\)) \%** \\ \hline Ni/Al2O3 & 10 & 0 & 7.1 & 0 \\ Fe/Al2O3 & 0 & 10 & 0 & 6.9 \\ Ni-Fe/Al2O3 & 5 & 5 & 3.1 & 3.0 \\ \hline \hline \end{tabular}
\end{table}
Table 1: ICP-OES results of the prepared catalysts.  
Figure 2: (**A**) XRD pattern, (**B**) FTIR spectra, (**C**) N2 adsorption–desorption isotherms, and (**D**) Pore size distribution of Ni-Fe/Al2O3 catalyst.  
all number of acidic sites. This reduction followed a specific sequence: Al\({}_{2}\)O\({}_{3}\) exhibited the highest acidity (0.90 mmol/g), followed by Ni/Al\({}_{2}\)O\({}_{3}\) (0.48 mmol/g), Fe/Al\({}_{2}\)O\({}_{3}\) (0.43 mmol/g), and finally bimetallic Ni-Fe/Al\({}_{2}\)O\({}_{3}\) (0.42 mmol/g), which displayed the lowest acidity. Additionally, a significant decline in the density of medium and strong acidic sites was detected, while conversely, the population of weak acidic sites increased as metal loading progressed.