Selective Catalytic Hydrogenation Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of hazardous compounds which originate from coal tar, crude oil but mainly arise from the incomplete combustion of fossil fuels and organic matters. Because of the carcinogenic properties and the wide distribution in environment, PAHs have been regarded as the priority pollutants and have taken seriously ecological problems. In contrast, the partial saturated PAHs which formed by reduction of corresponding PAHs are less toxic compounds and moreover, they are widely used in pharmaceutical, dyes and fuels. Therefore, converting the toxic PAHs into high-valued partial saturated PAHs will be a meaningful protocol for both the environment and the chemical production. In this thesis, we used catalytic hydrogenation which follows the conception of atomic economy and be friendly to environment to systematically study the regularity of selective catalytic hydrogenation of PAHs.In the reaction of selective hydrogenation of naphthalene to tetralin, the rapidly quenching Skeletal Ni (QS Ni) showed excellent activity and selectivity to tetralin. Excellent100%naphthalene conversion and100%tetralin selectivity were obtained in one-pot reaction under353K and1.0MPa H2pressure in cyclohexane. In presence of thiophene, QS Ni showed stronger ability to immune to sulfur deactivation than NS Ni. Further study the regularities of selective hydrogenation of other condensed aromatics over QS Ni. As for the bicyclic condensed aromatics (BCAs), the size of the substitued group, the sites of BCAs that be subsituted, and coordination ability of the heteroatoms substitued in the skeleton of BCAs greatly affected the reaction rate and the distribution of the hydrogenation products. As for the condensed aromatics with three or more rings, the steric hindrance around the benzen rings will determin the reaction rates and the distribution of the hydrogenation products.In the reaction of selective hydrogenation of quinoline to1,2,3,4-tetraquinoline, QS Ni showed excellent selectivity, however, the reactivity greatly decreased after the first usage. By contrast, a series of [Pd-Pt]/C catalyts which were prepared by colloidal method exhibited excellent high reactivity, selectivity and stability. When two kinds of surfactants (Brij-35and Tween-20) were used to protect the [Pd-Pt] nanoparticle simultaneously, the5wt%[Pd-Pt (1:3)]/C hold the highest activity. Excellent100%quinoline conversion and100%1,2,3,4-tetraquinoline selectivity were obtained in one-pot reaction under403K,2.5MPa H2pressure in ethanol for50min. In the reaction of selective hydrogenation of biphenyl (BP) to cyclohexylbenzene (CHB), QS Ni exhibited higher reactivity and selectivity to CHB than NS Ni and other supported noble metal catalysts. Excellent100%BP conversion and99.5%CHB selectivity were obtained in one-pot reaction under373K,2.0MPa H2pressure in THF for1.5h. Further study the selective hydrogenation of the regularity of selective hydrogenation of other biphenyl compounds and multiphenyl alicyclic hydrocarbons over QS Ni. As for the biphenyl compounds, the size of the substitued group, the sites that be subsituted and coordination ability of the substitued heteroatoms greatly affected the reaction rate and the distribution of the hydrogenation products. As for the multiphenyl alicyclic hydrocarbons, the distance between the phenyl groups and the steric hindrance around the benzene rings determined the reaction rate and the distribution of hydrogenation products.In the reaction of selectivie hydrogenation of p-phenylphenol (p-PP) to p-cyclohexylphenol (p-CP), a series of Pd/C were prepared by colloidal method exhibited excellent reactivity and selectivity. Using polar solvents as reaction medium, Pd(OAc)2as Pd precursors and active carbon as the catalyst spport favors the selectivity to p-CP. Excellent100%p-PP conversion and89%p-cyclohexylphenol selectivity were obtained in one-pot reaction under363K and8.0MPa H2pressure in THF for90min.