Haijie Sun

Progress in Ru-Based Amorphous Alloy Catalysts for Selective Hydrogenation of Benzene to Cyclohexene

Abstract Ru-based amorphous alloy catalysts prepared by the chemical reduction method have high activity and excellent cyclohexene selectivity due to their structure that has the merits of amorphous alloys and nano-particles. In particular, the supported catalysts have the advantages of better utilization of the Ru noble metal and ease of use in industry. The thermodynamics and kinetics for selective hydrogenation of benzene to cyclohexene over these catalysts, and the influence of the structure and composition of the catalysts were described. The reaction conditions, ability to modify the catalysts, and results of pilot tests were emphasized. Directions in this field for future research were suggested.

Selective hydrogenation of benzene to cyclohexene on Ru-based catalysts promoted with Mn and Zn

Abstract Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promoted with Zn or Mn alone. The optimum Mn/Zn molar ratio was determined to be 0.3. With the addition of 0.5 g NaOH, the Ru-Mn-Zn-0.3 catalyst, which was reduced at 150 °C, afforded a cyclohexene selectivity of 81.1% at a benzene conversion of 60.2% at 5 min and a maximum cyclohexene yield of 59.9% at 20 min. Based on characterizations, the excellent performance of Ru-Mn-Zn catalyst was ascribed to the suitable pore structure, the appropriate reducibility and the homogenous chemical environment of the catalyst.

Cu-Zn/Al2O3 Catalyst for the Hydrogenation of Esters to Alcohols

A chromium free Cu-Zn/Al2O3 catalyst was used for the slurry phase hydrogenation of palm oil esters to alcohols. Optimal reaction conditions were given. Under the relatively mild conditions of 240 °C and 10 MPa hydrogen pressure, the alcohol yield was above 86.3%, which was much higher than that of conventional Cu-Cr catalysts. Phase changes of the precursor and the calcined and used catalysts were investigated. The role of the active components and surface hydroxyl groups was discussed.

Monolayer Dispersed Ru-Zn Catalyst and Its Performance in the Selective Hydrogenation of Benzene to Cyclohexene

Abstract A series of Ru-Zn catalysts with different Zn loadings were prepared by co-precipitation. X-ray diffraction and X-ray photoelectron spectroscopy results showed that a large part of the Zn in the Ru-Zn catalysts were present in the form of ZnO and the ZnO on the catalyst surface could react with ZnSO 4 in the slurry to form a basic zinc sulfate salt during hydrogenation. The content of the basic salt increased with an increase in the Zn loading of the catalysts. This resulted in a decrease in catalyst activity and an increase in selectivity for cyclohexene. When the Zn loading was 8.6%, the basic salt dispersion was close to monolayer dispersion on the catalyst surface. When the catalysts were pretreated in the presence of 0.6 mol/L ZnSO 4 solution at 140 °C and at 5 MPa H 2 , a cyclohexene selectivity of 69.8% and a benzene conversion of 84.4% was achieved after 20 min.

Selective Hydrogenation of Benzene to Cyclohexene over a Ru-Zn catalyst with Diethanolamine as an Additive

A Ru-Zn catalyst was prepared by co-precipitation, and the effect of adding diethanolamine on benzene selective hydrogenation to cyclohexene was investigated. The catalyst was characterized by N2 physisorption, transmission electron microscopy, X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and temperature-programmed reduction. Diethanolamine reacted with ZnSO4 in the slurry to form (Zn(OH)2)3(ZnSO4)(H2O)3 and diethanolamine sulfate. The amount of (Zn(OH)2)3(ZnSO4)(H2O)3 adsorbed on the catalyst surface increased with increasing diethanolamine amount. The synergism of (Zn(OH)2)3(ZnSO4)(H2O)3 and diethanolamine sulfate improved the cyclohexene selectivity of the Ru-Zn(4.9%) catalyst. With a diethanolamine dosage of 0.3 g, (Zn(OH)2)3(ZnSO4)(H2O)3 was highly dispersed on catalyst surface and the sample after hydrogenation was characterized. This catalyst exhibited the best performance with a cyclohexene selectivity and yield of 75.5% and 63.6%, respectively, at the benzene conversion of 84.3% in the third run. Moreover, the benzene conversion and cyclohexene selectivity were stable above 75% and cyclohexene yield was above 58% in the fourth run.

Selective Hydrogenation of Benzene to Cyclohexene over Ru-Zn Catalyst with Nanosized Zirconia as Dispersant

Nanosized zirconia was prepared by hydrothermal synthesis. The effect of zirconia with the different surface areas of 34 and 87 m2/g (denoted ZrO2-34 and ZrO2-87, respectively) used as dispersants on the catalytic properties of the Ru-Zn catalyst was investigated. The crystallite sizes of ZrO2-34 and ZrO2-87 were 21.6 and 11.4 nm, respectively. They had similar purity and phases. Cyclohexene selectivity and the stability of the Ru-Zn catalyst dispersed using ZrO2-34 were better than that using ZrO2-87. This was due to the smaller surface area, bigger pore diameter, smaller particle size, narrower particle distribution, and bigger larger density of ZrO2-34.

Selective hydrogenation of benzene to cyclohexene over Ce-promoted Ru catalysts

Abstract Ru-Ce catalysts were prepared by a co-precipitation method. The effects of Ce precursors with different valences and Ce contents on the catalytic performance of Ru-Ce catalysts were investigated in the presence of ZnSO 4 . The Ce species in the catalysts prepared with different valences of the Ce precursors all exist as CeO 2 on the Ru surface. The promoter CeO 2 alone could not improve the selectivity to cyclohexene of Ru catalysts. However, almost all the CeO 2 in the catalysts could react with the reaction modifier ZnSO 4 to form (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 salt. The amount of the chemisorbed salt increased with the CeO 2 loading, resulting in the decrease of the activity and the increase of the selectivity to cyclohexene of Ru catalyst. The Ru-Ce catalyst with the optimum Ce/Ru molar ratio of 0.19 gave a maximum cyclohexene yield of 57.4%. Moreover, this catalyst had good stability and excellent reusability.

Selective hydrogenation of benzene to cyclohexene over monometallic ruthenium catalysts in the presence of CeO2 and ZnSO4 as co-modifiers

Abstract The monometallic Ru catalysts with the CeO 2 without calcination and ZnSO 4 as co-modifiers gave a cyclohexene yield of 58.5% at the optimum nominal CeO 2 /Ru molar ratio of 0.15. Moreover, this catalyst had a good stability. The chemisorbed (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 salt on Ru surface, which was formed by the CeO 2 reacting with ZnSO 4 , created the new Ru active sites suitable for the formation of cyclohexene and improved the selectivity to cyclohexene. In addition, the Zn 2+ in the aqueous phase could form a stable complex with cyclohexene, stabilizing the cyclohexene in the liquid phase and improving the selectivity to cyclohexene. The calcination treatment of CeO 2 was not beneficial for the enhancement of the selectivity to cyclohexene since it is difficult for the CeO 2 calcinated to react with ZnSO 4 to form the (Zn(OH) 2 ) 3 (ZnSO 4 )(H 2 O) 3 salt.