Rationally Engineering a CuO/Pd@SiO₂ Core–Shell Catalyst with Isolated Bifunctional Pd and Cu Active Sites for n-Butylamine Controllable Decomposition

Abstract

Volatile organic amines are a category of typical volatile organic compounds (VOCs) extensively presented in industrial exhausts causing serious harm to the atmospheric environment and human health. Monometallic Pd and Cu-based catalysts are commonly adopted for catalytic destruction of hazardous organic amines, but their applications are greatly limited by the inevitable production of toxic amide and NO x byproducts and inferior low-temperature activity. Here, a CuO/Pd@SiO 2 core−shell-structured catalyst with diverse functionalized active sites was creatively developed, which realized the total decomposition of n-butylamine at 260 °C with a CO 2 yield and N 2 selectivity reaching up to 100% and 98.3%, respectively (obviously better than those of Pd@SiO 2 and CuO/SiO 2 ), owing to the synergy of isolated Pd and Cu sites in independent mineralization of n-butylamine and generation of N 2 , respectively. The formation of amide and short-chain aliphatic hydrocarbon intermediates via C−C bond cleavage tended to occur over Pd sites, while the C−N bond was prone to breakage over Cu sites, generating NH 2 • species and long free-N chain intermediates at low temperatures, avoiding the production of hazardous amide and NO x . The SiO 2 channel collapse and H + site production resulted in the formation of N 2 O via suppressing NH 2 • diffusion. This work provides critical guidance for a rational fabrication of catalysts with high activity and N 2 selectivity for environmentally friendly destruction of nitrogen-containing VOCs.

N-Butylamine Decomposition over Hierarchical Porous Copper–Manganese Composite Oxides: Overcoming the Limitation Between Activity and N2 Selectivity

“…51 The band at 1250 cm −1 is assigned to δ(CH 2 ) of n-butylamine and intermediates. 7 The peak at 1160 cm −1 is assigned to the vibrations of the C−C bond in alcohols. The bands at 1050, 1076, and 1114 cm −1 are correlated to the alcohol species.…”

“…However, single Cu based catalysts show inferior activity for complete mineralization of nbutylamine. 7 For instance, Xing et al prepared the Cu-ZSM-5 catalyst for n-butylamine catalytic oxidation, and 100% yield to CO 2 can only be achieved at 350 °C with ∼90% N 2 selectivity, even at relatively low n-butylamine concentration (375 ppm) and space velocity (12 000 h −1 ). 15 The introduction of strong oxidizing active sites is an effective approach to improving the catalytic activity for complete mineralization of pollutants.…”

“…5,6 As a typical NVOCs, n-butylamine has been widely used as an ingredient in the manufacture of pesticides, pharmaceuticals, and emulsifiers. 7,8 Several terminal control technologies for VOCs have been developed recently, mainly including biological purification, thermal combustion, thermal catalytic oxidation, plasma oxidation, and photocatalytic purification. 9,10 Among them, thermal catalytic oxidation is one of the most promising methods due to its advantage of low energy consumption and high efficiency.…”

Formaldehyde Ambient-Temperature Decomposition over Pd/Mn3O4–MnO Driven by Active Sites’ Self-Tandem Catalysis

“…Thus, it is crucial to remove HCHO within indoor environments. Among various purification technologies, catalytic oxidation (especially at ambient temperature) has been demonstrated as one of the most energy-efficient and environmental-friendly methods as it can effectively decompose HCHO into harmless carbon dioxide (CO 2 ) and water (H 2 O) without generating any additional energy consumption or toxic byproducts. − …”

A [Cu2O2]2+ Core in Cu/ZSM-5 for Efficient Selective Catalytic Oxidation of Nitrogen-Containing VOCs and NH3

“…Volatile organic compounds (VOCs) are the main precursors of ozone and photochemical smog, seriously harmful to the environment and human health, attracting much public attention. − Nitrogen-containing VOCs (NVOCs) such as amides, nitrile, amines, and nitro-compounds, which originate primarily from industrial processes and motor vehicles under low-speed driving, are often foul-smelling and highly toxic and are more harmful than conventional VOCs. − So far, various methods have been developed for NVOC removal, such as absorption, thermal combustion, and catalytic oxidation. With advantages in purification efficiency and cost, catalytic oxidation is one of the most promising methods. ,− Different from other VOCs oxidation, the N 2 selectivity during selective catalytic oxidation (SCO) of NVOCs must be considered as an important target to avoid the secondary pollution of NO x . − Therefore, the cooperative control of VOCs and NO x is the key issue in eliminating NVOCs.…”