226 research outputs found
TPR Investigation of bimetallic Ru-Cu samples supported on SiO 2 , Al 2 O 3 and MgO
Bimetallic Ru-Cu samples supported on SiO 2 , Al 2 O 3 and MgO were studied by the temperature-programmed reduction (TPR) technique. Experiments were carried out both on unreduced impregnated salts and after oxidation of already reduced samples. The TPR profiles reveal a simultaneous reduction of ruthenium and copper precursors, even though the Ru and Cu in the monometallic catalysts exhibit reduction peaks which differ by up to 150 Β°C. It is suggested that the two metal salts interact during the stages of preparation and drying, and after reduction form bimetallic aggregates which are not stable and tend to separate. The stability of the bimetallic particles was found to be strongly dependent on the support used, being higher on SiO 2 than on Al 2 O 3 and MgO. It is suggested that the chemical nature of the support determines the different degree of interaction and/or agglomeration of the bimetallic particles. Auf SiO 2 , Al 2 O 3 und MgO aufgebrachte bimetallische Ru-Cu-Proben wurden mittels temperaturprogrammierter Reduktion (TPR) untersucht. Experimente wurden sowohl mit unreduzierten, durch Impregnation aufgebrachten Salzen als auch mit nach vorangegangener Reduktion reoxydierten Proben ausgefΓΌhrt. Die TPR-Profile lassen eine gleichzeitige Reduktion der Ruthenium- und Kupfervorstufen erkennen, obwohl Ru und Cu in monometallischen Katalysatoren Reduktionspeaks zeigen, die um bis zu 150 Β°C voneinander entfernt liegen. Es wird angenommen, daΓ die zwei Metallsalze wΓ€hrend des Darstellungs- und Trocknungsstadiums miteinander in Wechselwirkung treten und nach der Reduktion nicht stabile, zum Zerfall tendierende bimetallische Aggregate bilden. Die StabilitΓ€t der bimetallischen Partikel ist stark vom TrΓ€ger abhΓ€ngig, sie ist an SiO 2 hΓΆher als an Al 2 O 3 und MgO. Es wird angenommen, daΓ die chemische Natur des TrΓ€gers den Grad der Wechselwirkung und/oder Agglomeration der bimetallischen Partikel bestimmt. ΠΠ΅ΡΠΎΠ΄ΠΎΠΌ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ ΠΎ-ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΠΎΠ³ΠΎ Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ (Π’ΠΠ) ΠΈ Π·ΡΡΠ΅Π½Ρ Π±ΠΈΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΎΠ±Ρ Π°Π·ΡΡ ΡΡΡΠ΅Π½ΠΈΠΉ β ΠΌΠ΅Π΄Ρ Π½Π° ΠΏΠΎΠ΄Π»ΠΎΠΆΠΊΠ°Ρ
ΠΈΠ· Π΄Π²ΡΠΎΠΊΠΈΡΠΈ ΠΊΡΠ΅ΠΌΠ½ΠΈΡ, ΠΎ ΠΊΠΈΡΠΈ Π°Π»ΡΠΌΠΈΠ½ΠΈΡ ΠΈ ΠΎΠΊΠΈΡΠΈ ΠΌΠ°Π³Π½ΠΈΡ. ΠΠΊΡΠΏΠ΅Ρ ΠΈΠΌΠ΅Π½ΡΡ Π±ΡΠ»ΠΈ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ Ρ ΠΊΠ°ΠΊ Ρ Π½Π΅Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½Π½ΡΠΌΠΈ ΠΏΡΠΎΠΏΠΈΡΠ°Π½Π½ΡΠΌΠΈ ΡΠΎΠ»ΡΠΌΠΈ, ΡΠ°ΠΊ ΠΈ Ρ Π²Π½ΠΎΠ²Ρ ΠΎΠΊ ΠΈΡΠ»Π΅Π½Π½ΡΠΌΠΈ ΡΠ°Π½Π΅Π΅ Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½Π½ΡΠΌΠΈ ΠΎΠ± ΡΠ°Π·ΡΠ°ΠΌΠΈ. ΠΡΠΎΡΠΈΠ»ΠΈ ΠΊΡΠΈΠ² ΡΡ
ΠΏΠΎΠΊΠ°Π·ΡΠ²Π°ΡΡ ΠΎΠ΄Π½ΠΎΠ²ΡΠ΅ΠΌ Π΅Π½Π½ΠΎΠ΅ Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈ Π΅ ΡΡΡΠ΅Π½ΠΈΡ ΠΈ ΠΌΠ΅Π΄ΠΈ, ΡΠΎΠ³Π΄Π° ΠΊΠ°ΠΊ Π² ΡΠ»ΡΡΠ° Π΅ ΠΌΠΎΠ½ΠΎΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ² ΠΏΠΈΠΊΠΈ Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ ΡΡΡΠ΅Π½ΠΈΡ ΠΈ ΠΌΠ΅Π΄ΠΈ ΠΎΡΠ»ΠΈΡΠ° ΡΡΡΡ Π½Π° 150 Β°C, ΠΡΠΎ ΡΠ²ΠΈΠ΄Π΅ΡΠ΅Π»ΡΡΡΠ²ΡΠ΅Ρ ΠΎ ΡΠΎΠΌ, ΡΡΠΎ ΡΠΎΠ»ΠΈ ΠΎΠ±ΠΎΠΈΡ
ΠΌΠ΅ΡΠ°Π»Π»ΠΎΠ² Π²Π·Π°ΠΈΠΌ ΠΎΠ΄Π΅ΠΉΡΡΠ²ΡΡΡ ΠΌΠ΅ΠΆΠ΄Ρ ΡΠΎΠ± ΠΎΠΉ Π½Π° ΡΡΠ°Π΄ΠΈΠΈ ΠΏΠΎΠ»ΡΡΠ΅Π½ΠΈΡ ΠΈ Π²ΡΡΡΡΠΈΠ²Π° Π½ΠΈΡ, Π° ΠΏΠΎΡΠ»Π΅ Π²ΠΎΡΡΡΠ°Π½ΠΎΠ²Π»Π΅Π½ΠΈΡ ΠΎΠ±ΡΠ° Π·ΡΡΡ Π±ΠΈΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈ Π΅ Π°Π³ΡΠ΅Π³Π°ΡΡ, ΠΊΠΎΡΠΎΡΡΠ΅ Π½Π΅ΡΡΡΠΎΠΉΡΠΈΠ²Ρ ΠΈ ΠΈΠΌΠ΅ΡΡ ΡΠ΅Π½Π΄Π΅Π½ΡΠΈΡ ΠΊ ΡΠ°Π·Π΄Π΅Π»Π΅Π½ΠΈΡ. Π£ΡΡΠ°Π½ΠΎΠ² Π»Π΅Π½ΠΎ, ΡΡΠΎ ΡΡΠ°Π±ΠΈΠ»ΡΠ½ΠΎΡΡ Ρ Π±ΠΈΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ°Ρ ΡΠΈΡ ΡΠΈΠ»ΡΠ½ΠΎ Π·Π°Π²ΠΈΡΠΈΡ ΠΎΡ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠ° ΠΏΠΎΠ΄Π»ΠΎΠΆΠΊΠΈ, Ρ Π²Π»ΡΡΡΡ Π±ΠΎΠ»Π΅Π΅ Π²ΡΡΠΎΠΊΠΎΠΉ Π½Π° Π΄Π²ΡΠΎΠΊΠΈΡΠΈ ΠΊΡΠ΅ΠΌΠ½ΠΈΡ ΠΏΠΎ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Ρ ΡΠ΅ΠΌ, ΡΡΠΎ Π½Π° ΠΎΠΊΠΈΡΠΈ Π°Π»ΡΠΌΠΈΠ½ΠΈΡ ΠΈ ΠΎΠΊΠΈΡ ΠΈ ΠΌΠ°Π³Π½ΠΈΡ. ΠΡΠ΅Π΄ΠΏΠΎΠ»ΠΎΠΆΠ΅Π½ ΠΎ, ΡΡΠΎ Ρ
ΠΈΠΌΠΈΡΠ΅ΡΠΊΠ°Ρ ΠΏΡΠΈΡΠΎΠ΄Π° ΠΏ ΠΎΠ΄Π»ΠΎΠΆΠΊΠΈ ΠΎΠΏΡΠ΅Π΄Π΅Π»ΡΠ΅Ρ ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ ΡΡΠ΅ΠΏΠ΅Π½Ρ Π²Π· Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ ΠΈΠ»ΠΈ Π°Π³Π» ΠΎΠΌΠ΅ΡΠ°ΡΠΈΠΈ Π±ΠΈΠΌΠ΅ΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠ°Ρ ΡΠΈΡ.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43142/1/10973_2005_Article_BF01912699.pd
Identification of active sites on supported metal catalysts with carbon nanotube hydrogen highways
Catalysts consisting of metal particles supported on reducible oxides exhibit promising
activity and selectivity for a variety of current and emerging industrial processes. Enhanced
catalytic activity can arise from direct contact between the support and the metal or from
metal-induced promoter effects on the oxide. Discovering the source of enhanced catalytic
activity and selectivity is challenging, with conflicting arguments often presented based on
indirect evidence. Here, we separate the metal from the support by a controlled distance
while maintaining the ability to promote defects via the use of carbon nanotube hydrogen
highways. As illustrative cases, we use this approach to show that the selective transformation
of furfural to methylfuran over Pd/TiO2 occurs at the Pd-TiO2 interface while anisole
conversion to phenol and cresol over Cu/TiO2 is facilitated by exposed Ti3+ cations on the
support. This approach can be used to clarify many conflicting arguments in the literatureWe acknowledge financial support from the National Science Foundation, Grant CAREER1653935. Use of the Advanced Photon Source is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. E.C.W. and J.T.M. were supported in part by Center for Innovative Transformation of Alkane Resources (CISTAR) by the National Science Foundation under Cooperative Agreement No. EEC-1647722.
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Near Absence of Support Effects in Toluene Hydrogenation Catalyzed by MgO-Supported Iridium Clusters
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