## 3 Results and Discussion
### Catalytic Performance  
At present, there is still much debate on the effective acidic sites in long-chain alkanes hydrogen isomerization. However, many studies have shown that [28] the branched chains formed in the hydroisomerization of long-chain alkanes cannot be carried out in the pores due to the diffusion limitation. [PERSON] [29] and others further studied that the isomerization of long-chain alkanes mainly occurred on the surface of zeolite and the acidic sites near the pore, but could not occur in the zeolite pore. They also proposed the concept of \"pore and key-lock\" catalysis in alkane isomerization of microporous zeolites. For the metal-acid bifunctional catalysts, it is recognized that alkanes are first adsorbed at the metal sites and dehydrogenated to form olefins, then the olefins diffuse to the acid sites for isomerization, and finally the iso-olefins intermediates diffuse to the metal site for hydrogenation reaction [30]. Thus, the balance between metals and acids is crucial to isomerization performance of alkanes [31]. In this paper, we use n-dodecane isomerization as the probe reaction to study the catalytic performance of zeolites. The results of the isomerization reaction of n-dodecane on different samples are shown in Figure 11. From these results, we can see that the conversion of all the catalysts increases gradually with the increase of reaction temperature (Figure 11a). Pt/H-ZN-1 with the strongest B acid sites showed the highest conversion of n-dodecane. In contrast, Pt/H-ZS-2 with the fewest B acid sites needs higher reaction temperature to reach the same conversion as Pt/H-ZS-1 and Pt/H-ZN-1 catalysts. The variation trend of i-dodecane selectivity on the catalysts with the reaction conversion is plotted in Figure 11b. With the increase of n-dodecane conversion, the i-dodecane selectivity of all catalysts decreases gradually, which is due to the fact that high temperature is favorable for cracking side reaction. When the reaction temperature is 271.5 \({}^{\circ}\)C, the n-dodecane conversion on the Pt/H-ZN-1 is 91.4% and the selectivity of i-dodecane is only 72.2%. This may be due to the H-ZN-1 carrier contains a large number of strong L acid and B acid, which enhance the cracking reaction. When the reaction temperature is 245.5 \({}^{\circ}\)C, the n-dodecane conversion on Pt/H-ZS-2 is 36.8%, and the selectivity of the i-dodecane is 89.7%, which is due to its Low B acid strength and low L acid content, and L acids can cause cracking of alkanes. When the reaction temperature rises to 275.8 \({}^{\circ}\)C, the conversion of n-dodecane is 90.4%, while the selectivity of i-dodecane is decreased to 79.5%. This may be because the low dispersion and large particle size of Pt on the Pt/H-ZS-2, providing fewer metal sites, which makes the de/hydrogenation and isomerization reactions mismatched [32]. Under the condition of high conversion, the olefin intermediates cannot be hydrogenated at the metal center in time, resulting in a decrease of catalyst activity and isomer selectivity. However, at the reaction temperature of 274.4 \({}^{\circ}\)C, the n-dodecane conversion of Pt/H-ZS-1 is 90.7%, and the i-dodecane selectivity is 81.2%. Obviously, Pt/H-ZS-1 exhibits higher stability and i-dodecane selectivity than the other two catalysts under high conversion conditions, which attributes to the suitable B acid and high Pt dispersion. Figure 11: Reaction results of n-dodecane isomerization on different samples: (**a**) n–dodecane conversion as a function of temperature, (**b**) i-dodecane selectivity versus conversion. (Reaction condition: H\({}_{2}\)/n-dodecane = 750, LHSV = 1.2 h-1, P = 4 MPa)[PERSON]  
[PERSON] et al.