The effects of dispersed catalyst and hydrogen donor on the cracking and cracking selectivity of characteristic model compounds in residue oil, such as N-eicosane, butyl benzene and 1,6-diphenylheptane, were investiga...The effects of dispersed catalyst and hydrogen donor on the cracking and cracking selectivity of characteristic model compounds in residue oil, such as N-eicosane, butyl benzene and 1,6-diphenylheptane, were investigated in the thermal, hydrothermal and catalytic hydrocracking systems at 440?℃. The three compounds had different cracking characteristics. N-eicosane had the simplest bond-scission way. The bond-scissions of butyl benzene in the thermal system were mainly β- and γ- bond-scission, while β- in hydrothermal and α- bond-scission in catalytic hydrocracking were main reactions. 1,6-diphenylheptane had more complex cracking ways, which were α-, β-, homolysis and γ-bond-scission. The bond-scissions of 1,6-diphenylheptane in thermal cracking underwent such four ways, how-ever, α- and β-bond-scission or α-bond-scission were main reactions in hydrothermal or in catalytic hydrocracking of 1,6-diphenylheptane, respectively. It seems that these three model compounds experienced the radical reaction in the single systems of model compounds or in the binary system of model compounds/tetralin for thermal, hydrothermal and catalytic hydrocracking. Molecular hydrogen as well as dispersed catalyst enhanced the cracking of model compounds, while H-donor depressed the cracking. For cracking selectivity of the three compounds, thermal and hydrothermal cracking were the basis of other processes and dispersed catalysts clearly affected the cracking selectivity of alkyl aromatics. On the other hand, hydrogen donor had influence on a certain extent on the cracking selectivity on the basis of the thermal, hydrothermal and catalytic hydrocracking systems.展开更多
B3LYP/6-31G(d,p) method was used to investigate the catalytic cracking mechanism of biomass tar model compound.Phenol,toluene and benzene were selected as the tar model compounds and CaO was selected as the catalyst.T...B3LYP/6-31G(d,p) method was used to investigate the catalytic cracking mechanism of biomass tar model compound.Phenol,toluene and benzene were selected as the tar model compounds and CaO was selected as the catalyst.The pathways of tar compound radical absorbed by CaO were determined firstly through comparing enthalpy changes of the absorption,and then Mulliken population changes were analyzed.The results show that the absorption of tar model compound radical and CaO is an exothermic reaction.Formation of C—O—Ca is more easily than that of C—Ca—O and formation of Caromatic—Caromatic—Ca—O is more easily than that of Caromatic—C(O)—Ca—O.The C—C bond Mulliken populations in tar model compound radicals are reduced by 11.9%,10.5% and 15.5% in the case of a hydrogen atom removed,and those are 15.7%,14.3% and 16.3% in the case of two hydrogen atoms removed through the absorption of CaO.Catalytic ability of CaO acting on the tar model compound is in an order of phenol>benzene>toluene.展开更多
文摘The effects of dispersed catalyst and hydrogen donor on the cracking and cracking selectivity of characteristic model compounds in residue oil, such as N-eicosane, butyl benzene and 1,6-diphenylheptane, were investigated in the thermal, hydrothermal and catalytic hydrocracking systems at 440?℃. The three compounds had different cracking characteristics. N-eicosane had the simplest bond-scission way. The bond-scissions of butyl benzene in the thermal system were mainly β- and γ- bond-scission, while β- in hydrothermal and α- bond-scission in catalytic hydrocracking were main reactions. 1,6-diphenylheptane had more complex cracking ways, which were α-, β-, homolysis and γ-bond-scission. The bond-scissions of 1,6-diphenylheptane in thermal cracking underwent such four ways, how-ever, α- and β-bond-scission or α-bond-scission were main reactions in hydrothermal or in catalytic hydrocracking of 1,6-diphenylheptane, respectively. It seems that these three model compounds experienced the radical reaction in the single systems of model compounds or in the binary system of model compounds/tetralin for thermal, hydrothermal and catalytic hydrocracking. Molecular hydrogen as well as dispersed catalyst enhanced the cracking of model compounds, while H-donor depressed the cracking. For cracking selectivity of the three compounds, thermal and hydrothermal cracking were the basis of other processes and dispersed catalysts clearly affected the cracking selectivity of alkyl aromatics. On the other hand, hydrogen donor had influence on a certain extent on the cracking selectivity on the basis of the thermal, hydrothermal and catalytic hydrocracking systems.
基金Project(51276023)supported by the National Natural Science Foundation of China
文摘B3LYP/6-31G(d,p) method was used to investigate the catalytic cracking mechanism of biomass tar model compound.Phenol,toluene and benzene were selected as the tar model compounds and CaO was selected as the catalyst.The pathways of tar compound radical absorbed by CaO were determined firstly through comparing enthalpy changes of the absorption,and then Mulliken population changes were analyzed.The results show that the absorption of tar model compound radical and CaO is an exothermic reaction.Formation of C—O—Ca is more easily than that of C—Ca—O and formation of Caromatic—Caromatic—Ca—O is more easily than that of Caromatic—C(O)—Ca—O.The C—C bond Mulliken populations in tar model compound radicals are reduced by 11.9%,10.5% and 15.5% in the case of a hydrogen atom removed,and those are 15.7%,14.3% and 16.3% in the case of two hydrogen atoms removed through the absorption of CaO.Catalytic ability of CaO acting on the tar model compound is in an order of phenol>benzene>toluene.
