Cerium doped copper/ZSM-5 catalysts used for the selective catalytic reduction of nitrogen oxide with ammonia

Abstract

Abstract:The CuCe/ZSM-5 catalysts with different cerium loadings (0, 0.5, 1.0, 1.5 and 2.0 wt.%) was investigated to evaluate the correlation between structural characteristics and catalytic performance for the selective catalytic reduction (SCR) of NO by NH3. It was found that the addition of cerium increased copper dispersion and prevented its crystallization. According to the results of X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H2-TPR), copper species were enriched on the ZSM-5 grain surfaces and part of copper ions was incorporated into the cerium lattice. Addition of cerium improved the redox properties of the CuCe/ZSM-5 catalysts, owing to the higher valence of copper and mobility of lattice oxygen than those of Cu/ZSM-5 catalyst. Hence the introduction of * Corresponding author. Tel.: +86-22-60601278; Fax.: +86-22-60600320 E-mail address: haoqinglan@tust.edu.cn ** Corresponding author. Tel.: +822 2220 0441; fax: +822 2220 2299 (K. Hui)E -mail address: kshui@hanyang.ac.kr (K. Hui) 2 cerium in Cu/ZSM-5 improved significantly NO conversion. On the one hand, the cerium introduction into Cu-Z enhances their low-temperature activities. 95% NO conversion is reached around 197 ºC for Cu-Z while the corresponding temperature value decreases to 148 ºC for CuCe4-Z. On the other hand, the temperature range of efficient NO reduction (95%) also extends to higher temperature when the cerium are added to Cu/ZSM-5. Among the Cu-Ce/ZSM-5 catalysts tested, the CuCe4-Z sample exhibits the highest catalytic activity with the temperature range for 90% NO removal of 148-427 ºC.

The promotional role of Ce in Cu/ZSM-5 and in situ surface reaction for selective catalytic reduction of NOx with NH3

“…The Cu2p3/2 peaks can be deconvoluted to two peaks, and the peaks at 933.4 eV represent the agglomerated CuO nanoparticles on the surface of catalysts, and the one at BE ¼ 935.2 eV is attributed to isolated Cu 2+ ion coordinated to supercial oxygen atoms of zeolite. 18,20 Since the diffraction peaks of CuO species could not be observed in the XRD spectra, these CuO crystallites' size should be lower than 3 nm. " was calculated by Cu (at%) Â (m/(1 + m)) and "CuO" was calculated by Cu (at%)/(1 + m).…”

The Role of Copper Speciation in the Low Temperature Oxidative Upgrading of Short Chain Alkanes over Cu/ZSM‐5 Catalysts

“…270 and 450 °C. The lower temperature desorption is attributed to adsorption at weak acid sites (Brønsted and Lewis) with the high temperature desorption unequivocally assigned to NH 3 chemisorbed at strongly acidic Brønsted sites . All zeolites showed decreased NH 3 capacity following Cu impregnation, averaging a loss of 26.0 % (±5.4 %) of total strong‐Brønsted sites.…”

“…As H 2 -TPR studies suggested the presence of exchanged Cu 2 + species, the occupation of exchange sites was confirmed through desorption is attributed to adsorption at weak acid sites (Brønsted andL ewis)w ith the high temperature desorption unequivocally assigned to NH 3 chemisorbed ats trongly acidic Brønsted sites. [48][49][50][51][52][53] All zeolites showedd ecreased NH 3 capacity following Cu impregnation, averaging al oss of 26.0 %( AE 5.4 %) of total strong-Brønsted sites. This was supported by DRIFTS spectra in Figure 3ii which showed decreased intensity of the peak at 3607 cm À1 (OH groups coordinated to Td framework Al 3 + )f or each ZSM-5 following Cu impregnation.…”

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

“…Today, researchers tend to focus on different compound oxides for catalyst support since they possess great features that would result in the higher removal of nitric oxide. Zeolite Socony Mobil–5 (ZSM-5) [62], TiO 2 [37,47,58–59], and Al 2 O 3 [60] are some of the examples of the most frequently used catalyst supports. The ZSM-5 support is reported to have a remarkable ion-exchange capacity [121].…”