MOF-Derived ZrO2-Supported Bimetallic Pd-Ni Catalyst for Selective Hydrogenation of 1,3-Butadiene

A series of MOF-derived ZrO2-supported Pd-Ni bimetallic catalysts (PdNi/UiO-67-CTAB(n)-A500) were prepared by co-impregnation and pyrolysis at 500 °C under air atmosphere using UiO-67-CTAB(n) (CTAB: cetyltrimethylammonium bromide; n: the concentration of CTAB; n = 0, 3, 8, 13, 18) as a sacrificial template. The catalytic activity of PdNi/UiO-66-CTAB(n)-A500 in 1,3-butadiene hydrogenation was found to be dependent on the crystal morphology of the UiO-67 template. The highest activity was observed over the PdNi/UiO-67-CTAB(3)-A500 catalyst which was synthesized using UiO-67-CTAB(3) with uniform octahedral morphology as the template for the 1,3-butadiene selective hydrogenation. The 1,3-butadiene conversion and total butene selectivity were 98.4% and 44.8% at 40 °C within 1 h for the PdNi/UiO-67-CTAB(3)-A500 catalyst, respectively. The catalyst of PdNi/UiO-67-CTAB(3)-A500 can be regenerated in flowing N2 at 200 °C. Carbon deposited on the surface of the catalyst was the main reason for its deactivation. This work is valuable for the high-efficiency bimetallic catalyst's development on the selective hydrogenation of 1,3-butadiene.

Host-induced alteration of the neighbors of single platinum atoms enables selective and stable hydrogenation of butadiene

Tuning the coordination neighbors of the metal center is emerging as an elegant approach to manipulating the performance of supported single-atom catalysts in heterogeneous catalysis. Herein, atomically dispersed Pt species with different coordination neighbors hosted on nitrogen-doped carbon (NC) and graphitic carbon nitride (C₃N₄) are constructed through an impregnation-activation approach. Advanced characterization techniques including X-ray electron microscopy, X-ray absorption spectroscopy, and high angle annular dark-field scanning transmission electron microscopy reveal the different nature of active sites induced by the hosts: i.e., the Pt-N_x configuration in NC but both Pt-N and Pt-O coordinations in C₃N₄. H₂-D₂ exchange experiments and electron microscopy further evidence that Pt/NC exhibits a high propensity for H₂ splitting and high thermal stability of the Pt species against agglomeration, whereas Pt/C₃N₄ cannot dissociate H₂ and the Pt atoms easily aggregate in the reductive stream. Consequently, when applied in the selective hydrogenation of 1,3-butadiene, Pt/NC exhibits higher selectivity to butenes and excellent stability, but Pt/C₃N₄ behaves as a nanoparticle analogue favoring deep hydrogenation. The superior selectivity patterns of the single Pt atoms over Pt nanoparticles are rationalized by the inversed adsorption strength between the H₂ and 1,3-butadiene molecules at different metal sites, which is substantiated by the kinetic studies.

Comparative Study of Pd-Ni Bimetallic Catalysts Supported on UiO-66 and UiO-66-NH2 in Selective 1,3-Butadiene Hydrogenation

Selective hydrogenation of 1,3-butadiene (BD) is regarded as the most promising route for removing BD from butene streams. Bimetallic Pd-Ni catalysts with changed Pd/Ni molar ratios and monometallic Pd catalysts were synthesized using two differently structured metal-organic framework supports: UiO-66 and UiO-66-NH₂. The effects of the structure of support and the molar ratio of Pd/Ni on the catalytic property of selective BD hydrogenation were studied. The Pd-Ni bimetallic supported catalysts, PdNi/UiO-66 (1:1) and PdNi/UiO-66-NH₂ (1:1), exhibited fine catalytic property at low temperature. Compared with UiO-66, UiO-66-NH₂ with a certain number of alkaline sites could reduce the catalytic activity for the BD hydrogenation reaction. However, the alkaline environment of UiO-66-NH₂ is helpful to improve the butene selectivity. PdNi/UiO-66-NH₂ (1:1) catalyst presented better stability than PdNi/UiO-66 (1:1) under the reaction conditions, caused by the strong interaction between the -NH₂ groups of UiO-66-NH₂ and PdNi NPs. Moreover, the PdNi/UiO-66-NH₂ (1:1) catalyst presented good reproducibility in the hydrogenation of BD. These findings afford a beneficial guidance for the design and preparation of efficient catalysts for selective BD hydrogenation.

Tuning the electronic property of Pd nanoparticles by encapsulation within ZIF-67 shells towards enhanced performance in 1,3-butadiene hydrogenation

The low olefin selectivity of Pd-based catalysts is a long-term challenge for the selective hydrogenation of 1,3-butadiene.

A DFT study on the mechanism of HCl and CO2 capture by CaO

HCl exhibits a preferred interaction with the O atom of CaO (100) surface, with the adsorption energy of −1.85 eV. HCl and CO2 are in competition with one another at the O site. The presence of HCl inhibits CO2 adsorption and promotes CO2 desorption.

Influence of surface Sn species and hydrogen interactions on the OH group formation over spherical silica-supported tin oxide catalysts

The catalyst stability for propane dehydrogenation can be improved by adding acidic nanomaterials that serve as coke reservoirs.