《Table 3 Product composition of1 0 0%n-heptane (wt%)》

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《Difunctional Adsorbents Ni/ZnO–HZSM-5 on Adsorption Desulfurization and Aromatization of Olef in Reaction》

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C4:butane and 2-methyl-1-propene

The product distribution of Ni/ZnO–Al 2 O 3 was analyzed by GC–MS，as shown in Table 4.The main products were1-hexene isomerides with branched chains，accounting for 8.0%.The results imply that rearrangement reaction occurred on the active Ni sites.Based on the above discussion and experimental phenomena，we infer that the competition between sulfides and olefins did not only exist in physical adsorption on the adsorbent surface but also in subsequent chemical reaction on active Ni sites.In this process，hydrogen molecules reacted with Ni to produce H-positive and H-negative ions.Then，the H-positive ions attacked the 1-hexene adsorbed on Ni byπ-bond formation to generate carbocation[30].Next，the carbocation molecules underwent structural rearrangements and generated branched isomers on the Ni surface[31]，which follows the minimum energy principle.However，while HZSM-5 was used as carrier，almost no 1-hexene isomers were present in the product.Instead，a large amount of aromatics toluene and xylene were generated，as shown in Table 4.Therefore，we speculate that in olefin aromatization，Ni played a major role in activating olefins into carbocation；then，carbocation followed oligomerization，cyclizing dehydrogenation in the pore of HZSM-5[29，32，33].On the other hand，nickel also played a key role in desulfurization via removing S atoms from the ring of thiophene.Thus，the high aromatics yield would weaken desulfurization performance because desulfurization and olefin aromatization both require the participation of active Ni sites at the same time.