Abstract
A series of Sc-doped ZrO2 supports, with Sc2O3 content in the range of 0 to 7.5% (mol/mol), were prepared using the hydrothermal method. Ni/Sc-doped ZrO2 catalysts with nickel loading of 10% (w/w) were prepared using impregnation method, and characterized with the use of XRD, Raman, H2 temperature-programmed reduction (H2-TPR), H2 temperature-programmed desorption (H2-TPD), XPS, and in situ FT-IR techniques. The catalytic performances of Ni/Sc-doped ZrO2 catalysts in maleic anhydride hydrogenation were tested. The results showed that the introduction of Sc3+ into ZrO2 support could effectively manipulate the distribution of maleic anhydride hydrogenation products. γ-butyrolactone was the major hydrogenation product over Sc-free Ni/ZrO2 catalyst with selectivity as high as 65.8% at 210 °C and 5 MPa of H2 pressure. The Ni/Sc-doped ZrO2 catalyst, with 7.5 mol% of Sc2O3 content, selectively catalyzed maleic anhydride hydrogenation to succinic anhydride, the selectivity towards succinic anhydride was up to 97.6% under the same reaction condition. The results of the catalysts’ structure–activity relationships revealed that there was an interdependence between the surface structure of ZrO2-based support and the C=O hydrogenation performance of the ZrO2-based supported nickel catalysts. By controlling the Sc2O3 content, the surface structure of ZrO2-based support could be regulated effectively. The different surface structure of ZrO2-based supports, resulted in the different degree of interaction between the nickel species and ZrO2-based supports; furthermore, the different interaction led to the different surface oxygen vacancies electron properties of ZrO2-based supported nickel catalysts and the C=O hydrogenation activity of the catalyst. This result provides new insight into the effect of ZrO2 support on the selective hydrogenation activity of ZrO2-supported metal catalysts and contributes to the design of selective hydrogenation catalysts for other unsaturated carbonyl compounds.
Highlights
Maleic anhydride (MA)—a typical α, β-unsaturated carbonyl compound—can be hydrogenated to produce succinic anhydride (SA), γ-butyrolactone (GBL), 1,4-Butanediol (BDO), and tetrahydrofuran (THF) (Figure 1)
Nickel species had weaker interaction with pure monoclinic ZrO2 support and the interaction promoted the additional relatively electron-deficient oxygen vacancies generated on surface of Ni/ZrO2 catalyst (H2 -TPR, Raman and X-ray photoelectron spectroscopy (XPS))
This work found the interdependence between the surface structure of ZrO2 -based support and the selective hydrogenation performance of ZrO2 -supported nickel catalysts, presented an effective strategy for manipulating the selective hydrogenation performance of the catalyst in catalyzing
Summary
Maleic anhydride (MA)—a typical α, β-unsaturated carbonyl compound—can be hydrogenated to produce succinic anhydride (SA), γ-butyrolactone (GBL), 1,4-Butanediol (BDO), and tetrahydrofuran (THF) (Figure 1). The coupled molecular structure leads to a delocalization of the electron density in the C=C and C=O bonds, which makes it hard for the selective hydrogenation of the C=C bond to obtain SA or for the selective hydrogenation of C=C and C=O bonds to obtain GBL [2]. For these reasons, the tailoring of high activity and selectivity catalysts to obtain SA or GBL, as well as an exploration of the relationship. Catalysts 2019, 9, 366 between the structure of the catalysts and their hydrogenation performances, are scientifically significant and of practical value [3,4].
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