Preparation And Characterization Of Metal Nano-cluster/Cellulose Benzoyl Ester Hybrid Membrane With Different Substitution Degree And Its Catalytic Activity For Partial Hydrogenation Of Benzene

Cyclohexene is an important organic chemical raw material with active doublebond, which has more extensive use in the pharmaceutical and petroleum industry.Although cyclohexene is the intermediate product of benzene hydrogenation,cyclohexane is always the end product rather than cyclohexene, owing to thekinetically favored hydrogenation of cyclohexene to cyclohexane. Compared with thetraditional preparation method of cyclohexene, one-step synthesis by partialhydrogenation of benzene allows that the process is shortened, high efficiency, reducedinvestment in equipment. Therefore, it has vital significance and broad applicationprospects for the technology development and applications of benzene selectivehydrogenation to cyclohexene.Our research group has been committed to the study of membrane reactor. In ourprevious studies, Long shuai et al have investigated the catalytic activity of Pt nano-cluster/polyimide hybrid membrane to the partial hydrogenation of benzene, in which theselectivity to cyclohexene can reach to72.4%; Li man et al have studied the use of Runano-cluster/photosensitive polyimide hybrid membrane in partial hydrogenation of benzene, inwhich the selectivity to cyclohexene can achieve44.5%; Zhai hao et al have discussedthe application of Pt nano-cluster/chitosan hybrid membrane to the selectivehydrogenation of benzene, in which the selectivity to cyclohexene reached to72.4%,because the preparation process of polyimide is complex and costly. However the yieldof cyclohexene was very low. Therefore, it still needs further study for how to improvethe selectivity of cyclohexene and get a higher yield at the time.In this dissertation, the cheap and abundant natural polymer cellulose was chosenas raw materia on the basis of studies of research group. We synthesized cellulosebenzoyl ester(CB) with better film forming and swelling properties through modifying.Then the catalytic activity center was embedded in CB which contained complexationhydroxyl in the main chain. The structure and performance of the resulting swollenmembrane reactor which was used for the selective hydrogenation for higher yieldwere characterized and analyzed. There are three parts to be included in this paper:1. Cellulose benzoyl ester(CB) was synthesized from cellulose and benzoylchloride in presence of pyridine(Py) as catalyst. Different substitution degree CBs wereobtained by controlling the amount of benzoyl chloride, and the resulting CBs have different swelling degree in benzene, cyclohexene and cyclohexane, which meet therequirement of the carrier fou hydrogenation of benzene. The structure and propertiesof CBs were characterized by FT-IR and XRD. The results show that the hydroxyl wasreplaced by phenyl after esterification, and the chain structure of cellulose waschanged, while the crystallinity decreased with the increasing of CBs substitutiondegree.2. We prepared PVP-Ru colloid with a low boiling point of n-butyl alcohol byfluxing. Ru/CB hybrid membrane, which was used for the selective hydrogenation,was prepared by supporting Ru nano-clusters(obtained by dissolving PVP-Ru colloid)into CB of different substitution degree. The structure and properties of Ru/CB hybridmembrane were characterized by TEM, XRD and XPS. We optimized the reactionconditions of benzene hydrogenation, and then explored the substitution degree, loadand additive of water on the influence of selectivity and yield of cyclohexene.Research results demonstrated that swelling behavior of CB acts as a crucial factor tothe selectivity of cyclohexene; the selectivity of cyclohexene maximum was53.4%,the yield was0.92%when the DS was0.79; the selectivity of cyclohexene was hightestwhen the load was5.0%; and the additive of water could improve the conversion rateof benzene. Repeated experiment results showed that Ru/CB hybrid membrane couldbe reused.3. Pt nano-clusters were prepared by the reduction of H2PtCl6with ethyleneglycol under microwave condition. Pt/CB hybrid membrane, which was used for theselective hydrogenation, was prepared by supporting Pt nano-clusters into CB ofdifferent substitution degree. The structure and properties of Pt/CB hybrid membranewere characterized by XRD and XPS. The resulting hybrid membrane was used for theselective hydrogenation, GC results showed that swelling behavior of CB acts as acrucial factor to the selectivity of cyclohexene; the selectivity of cyclohexenemaximum was0.43%, the conversion rate of benzene was0.92%when the DS was0.42; repeated experiment results showed that Pt/CB hybrid membrane could bereused.