Rationales Design von nanostrukturierten Kupfer‐Zinkoxid‐Katalysatoren für die Dampfreformierung von Methanol

Abstract

Die Autoren bedanken sich bei der ZEIT-Stiftung (Nanotechnologie für eine zukünftige Automobiltechnik) und der Deutschen Forschungsgemeinschaft, DFG (SP "Brückenschläge in der heterogenen Katalyse) für die finanzielle Unterstützung. KeywordsIn situ, heterogeneous catalysis, structure-activity relationships, X-ray diffraction, NMR spectroscopy Abstract Ziel eines rationalen Designs von Cu/ZnO-Katalysatoren ist es, die Volumenstruktur der Kupfernanoteilchen durch Ausnutzen bekannter Struktur-Funktionsbeziehungen während der Präparation durch geeignete Verfahren zielgerichtet einzustellen. Altern der frisch gefällten Präkursoren führt zu charakteristischen Phasenumwandlungen und erlaubt es, Mikroverspannung und Größe der Kupfernanoteilchen zu beeinflussen.

In situ investigations of structure–activity relationships of a Cu/ZrO2 catalyst for the steam reforming of methanol

“…It seems that also in the Cu/ZrO 2 systems additional microstructural parameters need to be considered to account for differently active specific Cu surfaces observed. In contrast to our previous reports on the correlation of microstrain and activity of Cu/ZnO catalysts, [8,9] 63 Cu NMR spectroscopy studies on differently treated Cu/ZrO 2 catalysts yielded nearly symmetric NMR lines (Figure 12) independent on the treatment conditions. This is indicative of only minor amounts of microstrain in the copper phase in the Cu/ZrO 2 materials.…”

“…However, additional factors influence the activity of copper catalysts and deviations in the microstructure of the catalysts may result in differently active copper surfaces. Similar to our results on Cu/ZnO catalysts, [8][9][10] the MSR activity of the Cu/ZrO 2 catalyst described here (Table 1) exhibits no simple linear correlation with the specific Cu surface area. A sufficient copper surface area is a prerequisite for an active methanol catalyst, however, it cannot account for the differences observed after the various oxidation/reduction treatments (Table 1).…”

“…Hence, a decrease in the copper crystallite size results in a symmetric NMR line broadening, while an increase in strain or disorder causes an asymmetric NMR line profile. [9,24] Figure 12 shows the 63 Cu NMR spectra of the Cu/ZrO 2 catalyst after various reaction steps. Besides differences in the amplitude it can be seen, that the width of the NMR lines varies only slightly as a function of the treatment conditions.…”

“…[4][5][6][7] We have previously reported, that the activity of Cu/ZnO catalysts for the methanol synthesis reaction and the methanol steam reforming correlates to the microstrain in the copper phase. [8,9] The strain in the copper nanoparticles originates at the Cu-ZnO interface and emphasizes the role of ZnO to influence the microstructure of the active copper phase in addition to prevent sintering. For the MSR reaction we could also show that the increase in activity after a temporary addition of oxygen to methanol and water is correlated with an increase of the disorder in the copper particles.…”

A Straightforward Route to Copper/Zinc Oxide Nanocomposites: The Controlled Thermolysis of Zn[Cu(CN)3]

“…Typically, a mixed solution of copper and zinc salts (usually nitrates or acetates) is prepared and the precipitation of both carbonates is induced by addition of sodium or ammonium carbonate whilst stirring, followed by drying and calcination. [6][7][8][9] The particle size and crystallinity of the products can be adjusted by the pH, the concentration, the stirring rate, the duration of precipitation and aging, and the calcination conditions. [10] Pollard et al [4] 2 ] as precursors for copperzinc mixed oxides.…”