Yunhan Bai,Xiaoshu Ding,Ying Sun,Yucong Song,Yanji Wang
The reverse water gas shift (RWGS) reaction is one kind of the catalytic conversion of CO 2 to reduce an enormous amount of CO 2 . However, the RWGS reaction has the safety hazards associated with the use of hydrogen and thermodynamic limitation. Therefore, this work proposes a new safe and efficient reaction route (CO 2 -MCH) to get CO from CO 2 and methylcyclohexane (MCH). Thermodynamic calculations showed that the equilibrium CO 2 conversion at 350 °C increased from 17.8 % of the RWGS reaction to 53.5 % of the CO 2 -MCH reaction. In the CO 2 -MCH reaction, the relationship of the catalytic performance with the metal dispersion, the Pt particle size and the acidity of Pt-based catalysts on the different supports was investigated, respectively. The results showed that the Pt/γ-Al 2 O 3 catalyst with high dispersion of Pt particles, small particle size and medium acidity had good activity and selectivity. The relationships among Pt loading and Pt particle size on the Pt/γ-Al 2 O 3 catalyst and the catalytic performance were evaluated. The Pt particle size gradually increased with the metal loading. A positive correlation was observed between Pt particle size and CO 2 conversion; a volcano-type relationship was observed between CO selectivity and Pt particle size. In the CO 2 -MCH reaction at 350 °C, 0.1 MPa, LHSV = 6 h −1 , the CO 2 conversion was 24.7 %, the CO selectivity reached 95.2 %, and the Pt/γ-Al 2 O 3 catalyst within 40 h showed good stability. Moreover, the mechanism of the CO 2 -MCH catalytic reaction over the Pt/γ-Al 2 O 3 catalyst was speculated.
The improvement of the sulfur tolerance over Pt catalyst is critical for the hydrotreatment of crude oil. Fe was co‒impregnation with Pt on γ-Al 2 O 3 at different calcination temperature. Results revealed that adding Fe significantly facilitated the reduction of Pt oxides for the catalyst calcined at 400 °C. The morphological analysis and CO chemisorption showed Fe improved the dispersion of Pt nanoparticles. The surface chemical state analysis implied the co‒existence of the electron‒deficient Pt and metallic Fe. However, the increase of calcination temperature caused a decreased reducibility of Pt oxides due to strong metal support interaction. A higher dibenzothiophene hydrodesulfurization conversion of 97.7 % with a dominant biphenyl selectivity of 96.7 % were acquired for the catalysts incorporated with Fe. The density functional theory calculations confirmed the alloyed Fe led to the formation of electron‒deficient Pt atoms, and the higher affinity to sulfur made Fe be a favorable additive for noble metal catalyst in the hydrodesulfurization.
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