Investigating the effect of thiophene on methylcyclopentane reforming reaction, the following conclusions were obtained.
(1) Initial reaction rate of dehydro-aromatization [v0(MCP=+Arom)] and of hydro-ring opening [v0(Ring open)] can be expressed by equation (A) and (B).
υ0(MCP=+Arom)=k(MCP=+Arom)K(MCP)pMCP/pH2/[1+K(MCP•)pMCP/pH21/2]2 (A)
υ0(Ring open)=k(Ring open)K(MCP•)pMCP/[1+K(MCP•)pMCP/pH21/2]2 (B)
These equations are in the same form with those found in reforming reaction of pure MCP.
(2) By addition of a very small quantity of thiophene (0.0025mol%), v0(MCP=+Arom.) and k(MCP=+Arom.) increase, while v0(Ring open) and k(Ring open) decrease. Both reaction steps are, however, suppressed remarkably by the addition of more than 0.02mol% thiophene.
(3) Especially, by the addition of 0.0025mol%-thiophene, the frequency factor of ring opening reaction [A(Ring open)] decreases remarkably in 0.035 times in comparison with pure MCP-reforming.
(4) Activation energy (E kcal/mol) and heat of adsorption (Q kcal mol) were obtained as follows.
E(MCP=+Arom.)=(29.0 at 0.0025mol%-36.8 at 2.0mol%-thiophene)
E(Ring open)=(34.7 at 0.0025mol%-39.3 at 2.0mol%-thiophene)
Q(MCP•)=(8.1 at 0.0025mol%-9.0-10.2 at 2.0mol%-thiophene)
(5) We could not explain such fact with customary hypothesis of two kinds of Pt-sites that dehydro-aromatization is promoted and hydro-ring opening is suppressed by the addition of a very small quantity of thiophene (0.0025mol%).