Effects of Different Copper Species on the Combustion of Dichloromethane over Cu/HZSM-5 Zeolite Nanoporous Catalysts

Abstract

This study compared the reaction behaviors of dichloromethane (DCM) catalytic combustion over Cu/HZSM-5 (H form of Zeolite Socony Mobil-5) nanoporous catalysts at different copper loadings. Among the samples investigated, Cu/HZSM-5 with 2.5 wt % Cu showed the best stability with a 90% DCM conversion at 320 °C during a 3 h reaction run. The analysis of the results showed different copper species (including cations and oxides particles) accounted for the diverse reaction behaviors observed. With a low copper loading (≤2.5 wt %), copper cations (such as isolated Cu + /Cu 2+ and oxocations) were the dominant copper species, which were strongly resistant to chlorine poisoning. However, we found the continuous coking deactivation of Cu/HZSM-5 with 1 wt % Cu loading owing to its low redox capacity. With further increase in the Cu content, the proportion of bulk-like CuO x species quickly increased. During the reaction with DCM, CuO x particles were involved in a chlorination process at a bulk level with the formation of CuCl x and Cu x (OH) y Cl crystalline phases, resulting in a rapid deactivation at the initial reaction stage. Cation-dominant copper nanomaterials are recommended for reaching a high stability in chlorinated volatile organic compound catalytic oxidation.

Regulating the Spatial Distribution of Ru Nanoparticles on CeO2 Support for Enhanced Propane Oxidation

“…The emission of volatile organic compounds (VOCs) is known to cause ozone layer depletion and photochemical smog formation . Catalytic combustion is considered to be one of the most effective strategies because it is highly adaptable to a broad range of VOC gas concentrations, free of secondary pollution, and able to be run at mild reaction temperatures. − Light alkanes (C2–C4) contribute a large fraction of the VOC emissions, particularly ethane and propane, which make up 3.9 and 2.6% of the total VOC emissions, respectively . However, these short-carbon-chain molecules are thermodynamically and chemically stable, making them difficult to catalytically convert. ,− With the increase of interest in using propane as a fuel in the transportation sector, it is critical to design a robust and economical catalyst that can operate at mild temperatures to control light-alkane oxidation.…”

Cu-VWT Catalysts for Synergistic Elimination of NOx and Volatile Organic Compounds from Coal-Fired Flue Gas

“…To further investigate the surface acidity or alkalinity and redox ability of the Cu-VWT catalyst, H 2 -TPR and a series of TPD (O 2 -TPD, NH 3 -TPD, and NO-TPD) tests were performed. For H 2 -TPR (Figure S11b), the reduction peak at 234 °C corresponds to the reduction of isolated Cu 2+ to Cu + , those at 263 °C and 312 °C correspond to the reduction of Cu 2+ in crystalline CuO, and that at 375 °C corresponds to the reductions V 5+ → V 4+ and Cu + → Cu . All of the reduction peaks of Cu-VWT were more intense than those of VWT and appeared at lower temperatures.…”

“…For H 2 -TPR (Figure S11b), the reduction peak at 234 °C corresponds to the reduction of isolated Cu 2+ to Cu + , those at 263 °C and 312 °C correspond to the reduction of Cu 2+ in crystalline CuO, and that at 375 °C corresponds to the reductions V 5+ → V 4+ and Cu + → Cu. 40 All of the reduction peaks of Cu-VWT were more intense than those of VWT and appeared at lower temperatures. The H 2 -TPR results thus showed that the Cu-VWT catalyst had a superior redox ability to that of the VWT catalyst.…”

Insight into the Role of Cerium in the Enhanced Performances during Catalytic Combustion of Acetonitrile over Core–Shell-like Cu–Ce/ZSM-5 Catalysts

“…The absorption of the UV region (208 nm) might be due to the charge-transfer band of O zeolite → Cu + /Cu 2+ related to isolated copper ions in the inner zeolite framework − and the peak at 224 nm could be attributed to oligomeric copper oxides (Cu–O–Cu complex) . The band at 780 nm was assigned to d–d transition Cu 2+ ions in the pseudo-octahedral environment such as Cu­(H 2 O) 6 2+ . , The Ce 5 /ZSM-5 sample exhibited two bands (217 and 320 nm), which were attributed to O 2– → Ce 3+ and O 2– → Ce 4+ charge transfers of ceria species, respectively. − With the addition of ceria, a new band at about 460 nm appeared for the Cu x Ce y /ZSM-5 catalyst, which could be attributed to the three-dimensional Cu + cluster in the CuO matrix . In addition, the band at 654 nm was assigned to the d–d transitions of Cu 2+ in a distorted O h (square planar) configuration, which belonged to bulk CuO species .…”

“…42 The band at 780 nm was assigned to d−d transition Cu 2+ ions in the pseudooctahedral environment such as Cu(H 2 O) 6 2+ . 43,44 The Ce 5 / ZSM-5 sample exhibited two bands (217 and 320 nm), which were attributed to O 2− → Ce 3+ and O 2− → Ce 4+ charge transfers of ceria species, respectively. 45−47 With the addition of ceria, a new band at about 460 nm appeared for the Cu x Ce y /ZSM-5 catalyst, which could be attributed to the three-dimensional Cu + cluster in the CuO matrix.…”