TY - JOUR

T1 - Counting of oxygen defects versus metal surface sites in methanol synthesis catalysts by different probe molecules

AU - Fichtl, Matthias B.

AU - Schumann, Julia

AU - Kasatkin, Igor

AU - Jacobsen, Nikolas

AU - Behrens, Malte

AU - Schlögl, Robert

AU - Muhler, Martin

AU - Hinrichsen, Olaf

PY - 2014/7/1

Y1 - 2014/7/1

N2 - Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N2O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N2O, temperature programmed desorption of H2, and kinetic experiments. The presence of ZnO dramatically influences the N2O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu-ZnO interface and can be used to easily quantify the intensity of Cu-Zn interaction. N2O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H2. A combination of N2O reactive frontal chromatography and H2 temperature-programmed desorption is used to analyze the interplay of copper and zinc oxide in methanol synthesis catalysts. This method provides an easy in situ approach to quantify the direct copper-zinc interaction (SMSI effect) and offers an important possibility to rational catalyst design also for other supported metal catalysts.

AB - Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N2O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N2O, temperature programmed desorption of H2, and kinetic experiments. The presence of ZnO dramatically influences the N2O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu-ZnO interface and can be used to easily quantify the intensity of Cu-Zn interaction. N2O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H2. A combination of N2O reactive frontal chromatography and H2 temperature-programmed desorption is used to analyze the interplay of copper and zinc oxide in methanol synthesis catalysts. This method provides an easy in situ approach to quantify the direct copper-zinc interaction (SMSI effect) and offers an important possibility to rational catalyst design also for other supported metal catalysts.

KW - catalyst-support interactions

KW - copper

KW - heterogeneous catalysis

KW - methanol

KW - oxygen defect sites

UR - http://www.scopus.com/inward/record.url?scp=84903314930&partnerID=8YFLogxK

U2 - 10.1002/anie.201400575

DO - 10.1002/anie.201400575

M3 - Article

AN - SCOPUS:84903314930

VL - 53

SP - 7043

EP - 7047

JO - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION

JF - ANGEWANDTE CHEMIE-INTERNATIONAL EDITION

SN - 1433-7851

IS - 27

ER -