Molecular Structure Effect on the Epoxidation of 1-Butene and Isobutene on the Titanium Silicate Catalyst under Transient Conditions in a Trickle Bed Reactor

Epoxidation of two butane isomers (1-butene and isobutene)on thecommercial titanium silicate (TS-1) catalyst was studied in a laboratory-scaletrickle bed reactor. The transient step response technique was usedas the main tool in the investigation. The transient responses revealeddifferent dynamics of product formation in continuous operation. Thestudy of isomers showed the impact of the molecular structure on thetransient and stationary states of the system. The four-carbon chainpresent in 1-butene displayed a dynamic behavior with a prominentmaximum of the conversion as a function of time-on-stream. On thecontrary, the behavior of isobutene was displayed to be closer toethene and propene under similar conditions reaching a steady stateafter ca. 2 h. The structure of the epoxide was an important factorin order to achieve a high epoxide selectivity. In isobutene epoxidation,the primary product 1,2-epoxy-2-methylpropane was highly reactive,giving a spectrum of parallelly formed byproducts. Therefore, theselectivity of the epoxide from isobutene was limited to ca. 70%.In the epoxidation of 1-butene, 1,2-epoxybutane was displayed to bea highly stable product with a selectivity close to 99%. Based onthe transient and stationary data, a reaction mechanism was proposedfor the epoxidation and ring-opening reactions present in the system.