Pt Catalyst Supported on Multiwalled Carbon Nanotubes for Hydrogenation-Dearomatization of Toluene

Using homemade multiwalled carbon nanotubes (CNTs) as the support, the Pt/CNTs catalyst was prepared by an incipient wetness method. Performance of the catalyst for hydrogenation-dearomatization (HDA) of toluene was evaluated and compared with the reference catalysts supported on γ-Al2O3 and activated carbon (AC). Over the 1.0%Pt/CNTs catalyst under the reaction conditions of 0.4 MPa, 373 K, PhCH3/H2 = 6/94 (mol/mol), and GHSV = 120 L/(h·g), the observed conversion of toluene HDA reached 100%, and the corresponding specific reaction rate was 0.0523 mmol/(s·m2). This value was 1.17 and 1.18 times that of the 1.4%Pt/γ-Al2O3 and 2.4%Pt/AC catalysts with the respective optimal Pt loading, respectively. It was experimentally found that using CNTs in place of γ-Al2O3 or AC as the support of the catalyst did not cause a significant change in the apparent activation energy for the toluene HDA reaction but led to a slight increase in concentration of catalytically active Pt species (Pt0) at the surface of the functioning catalyst. In addition, the Pt/CNTs catalyst could reversibly adsorb a greater amount of hydrogen under atmospheric pressure at temperatures from room temperature to 573 K. This unique feature would help to generate a microenvironment with higher stationary state concentration of active hydrogen adspecies at the surface of the functioning catalyst. These effects favored the toluene HDA reaction.