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.

In recent years, metal-organic frameworks (MOFs) have emerged as a class of promising precursors or sacrificial templates for synthesizing various porous metal oxides or carbon with complex compositions and a unique structure via pyrolysis owing to abundant intrinsic molecular metal sites, an ordered pore structure, high porosity, and an adjustable pore size [25][26][27][28][29][30].The composition and structure of MOF derivatives can be easily realized by adjusting the precursors or sacrificial templates of MOFs, modifying the pyrolysis temperature, and changing the pyrolysis atmosphere (inert or air atmosphere) [26,29,31,32].Moreover, the ordered pore structure of MOFs can envelop other metal salts or organic species which could further modify MOF derivatives [26,33].Recently, MOF derivatives have been widely used in heterogeneous catalysis, especially those using MOF derivatives as a support for metal nanoparticles [34][35][36][37][38]. Zeng et al. [34] synthesized the hierarchical mesoporous CuO@NiO (M-CuO@NiO) catalyst using MOFs as the precursor.The M-CuO@NiO catalyst displayed excellent catalytic activity and selectivity for the deoxygenation of fatty acids [34].The conversion of stearic acid and the selectivity of C 8 -C 18 alkanes reached 99.9% and 94.4%, respectively, which were comparable to the Pt/C catalyst [34].Lei et al. [39] successfully synthesized M-Co 1 Y 1 O x (Y = Cu, Mn, Fe, and Ni) catalysts using Y-doped ZSA-1 as a precursor via pyrolysis at 350 • C. The dopants displayed a great effect on the catalytic performance for toluene catalytic destruction on Co 3 O 4 derived from Co-MOF [39].They found that M-Co 1 Cu 1 O x showed the most prominent activity with T 90% reduced 31 • C (compared to M-Co 3 O 4 ) due to improved physical properties [39].They also reported that Co-Mn metal oxides synthesized through the pyrolysis of Mn-doped ZSA-1 presented excellent catalytic performance for toluene catalytic oxidation [40].Wang et al. [41] prepared the nitrogen-doped carbon material (NC-E) from ZIF-8 using a novel and simple method assisted by eutectic salts.They also prepared carbon materials NC-T from ZIF-8 using traditional calcination [41].The NC-E-supported Pt-Sn catalyst exhibited improved electrochemical activity and stability for the ethanol oxidation reaction than NC-T-and carbon black-supported Pt-Sn catalysts [41].Wang et al. [42] found that MOF-derived CeO 2 -supported Ag catalysts (Ag-Ce-BTC-C) prepared via one-pot and pyrolysis at 500 • C under Ar and O 2 atmosphere displayed good catalytic performance for the toluene oxidation reaction (T 90 = 226 • C).
eV can be ascribed to Pd 2+ 3d5/2 and Pd 2+ 3d3/2 (Figure 5b) [20,74].For the Ni 3p spectrum of PdNi/UiO-67-CTAB(3)-A500, a peak at 855.3 eV as well as a satellite peak at 861.4 eV were apparent in the Ni 2+ 2p3/2 region, whereas a signal at 873.1 eV as well as a satellite peak at 879.6 eV were observed in the Ni 2+ 2p5/2 region (Figure 5c) [34,75].As shown in C1s peaks, the strong peak at 284.4 eV was attributed to the graphite carbon, and the peaks at 284.8 eV, 286.4 eV, and 288.7 eV corresponded to the calibration peak C-C, C-O-C, and O = C-O, respectively (Figure 5d) [76,77].The Raman spectra of PdNi/UiO-67-CTAB(3)-A500 displayed two obvious peaks at 1381 cm −1 (D band) and 1592 cm −1 (G band) which can be attributed to the amorphous carbon species and highly symmetrical and ordered graphitized carbon species (Figure 6) [78,79].Both the results of XPS and Raman spectroscopy for PdNi/UiO-67-CTAB(3)-A500 illustrated the existence of carbon species; this may be due to the incomplete combustion of catalysts.

Molecules 2024 ,
29,  x FOR PEER REVIEW 7 of 18 diameter, and pore volume) of the MOF template have little influence on the BET surface area and pore volume of the catalysts obtained by pyrolysis.

Table 1 .
Comparison of physicochemical properties of different samples.

Table 1 .
Comparison of physicochemical properties of different samples.

Table 2 .
The catalytic performance of reported Pd-based catalysts in the hydrogenation of 1,3-butadiene.