Intermetallicization of Pd with Sn to Match Adsorption Configuration toward Highly Selective Hydrogenation
Wenhua Li, Xiaohu Ge, Chang Yao, Yueqiang Cao, Jing Zhang, Gang Qian, Xinggui Zhou, De Chen, Weikang Yuan, Xuezhi Duan
Abstract
Heterogeneous hydrogenation promoted by metal catalysts is a pivotal reaction in industrial processes, where the metal–substrate interactions often dictate adsorption behaviors and can compromise the selectivity. Here, we employ Sn sites to intermetallize Pd sites for regulating the adsorption behaviors on the Pd–Sn intermetallic surface toward the selective hydrogenation of 4,6-dinitroresorcinol (DNR) to 4,6-diaminoresorcinol (DAR), a key monomer in poly p -phenylene benzobisoxazole (PBO) fiber production. The Pd–Sn intermetallic catalysts were controllably synthesized by in situ growth of Sn(OH) 4 on PdMgAl layered double hydroxides (LDHs), followed by a thermally induced structure transformation under hydrogen. By a combination of systematic characterizations and density functional theory calculations, the Sn sites on the intermetallic surfaces are shown to isolate Pd sites and enrich the electron density around the Pd sites. Catalytic tests, kinetics studies, and microkinetics modeling simulations reveal that, as compared with those on the Pd, Pd 3 Sn, and PdSn 2 catalysts, the adsorption of DNR and related intermediates from the hydrogenation is appropriately weakened on the PdSn catalyst due to the well-matched configuration. Such optimized adsorption behaviors promote the activation of hydrogen and desorption of target DAR, resulting in enhanced catalytic activity and selectivity, with DAR selectivity reaching 96.7% at full DNR conversion. These findings highlight a strategy for modulating the strong adsorption of substrates and intermediates on active sites to improve hydrogenation, offering a promising approach for designing high-performance catalysts for selective hydrogenations.