白金系石油改質触媒による純炭化水素の反応(第6報)

シクロヘキサン改質反応の動力学的検討

抄録

Reforming reaction of cyclohexane (CH) over stabilized Pt/Al₂O₃/Cl type catalyst was investigated under the conditions of industrial use such as reaction temperature; 400-470°C, liquid hourly space velocity; 3-30vol/vol•hr, initial hydrogen pressure; 17.8-35.0atm and H₂/CH ratio; 5-15mol/mol. The following conclusions were obtained.
(1) The conventional rate equations of initial overall reaction [υ_0(T)], initial dehydrogenation [υ_0(Bz)] and initial ring-isomerization [υ_0(MCP)] are indicated as follows,
υ_0(T)=k_Tp_CH^-0.94p_H2^0.66, υ0(Bz)=k_Bzp_CH^-0.94p_H2^0.65 and υ_0(MCP)=k_MCPp_CH^-0.85p_H2^0.49
(2) Initial rate equations for individual reaction are indicated as follows,
υ_0(T)=k_TK(CH•)p_CH/p_H2^1/2/[1+K_(CH•)p_CH/p_H2^1/2]², υ_0(Bz)=k_BzK_(CH•)p_CH/p_H2^1/2/[1+K_(CH•)p_CH/p_H2^1/2]² and υ_0(MCP)=k_MCPK_(CH•)p_CH/p_H2^1/2/[1+K_(CH•)p_CH/p_H2^1/2]²
These are derived from the rate controlling step; [(CH•)_ads. on Pt-site_??_(CH:)_ads. on Pt-site+(H•)_ads. on Pt-site]. And these Langmuir-Hinshelwood type-initial rate equations satisfied the experimental data.
(3) Activation energies (Ekcal/mol) and heat of adsorption [Q_(CH•)kcal/mol] of cyclohexyl radical on Pt-site from the examination of initial rate equations are obtained.
E_(T)=18.2, E_(Bz)=17.9, E_(MCP)=19.6 and Q_(CH•)=2.5-2.8
(4) Reaction mechanism of reforming reaction of cyclohexane over Pt/Al₂O₃/Cl type petroleum reforming catalyst is assumed to be as follows.