The relation between reduction temperature and activity in copper catalysed ester hydrogenolysis and methanol synthesis

Brands, D. S.; Poels, E.K.; Krieger, Tamara; Макарова, О. В.; Weber, Casper; Veer, S. S.; Bliek, A.

doi:10.1007/bf00807616

Cited by 53 publications

(54 citation statements)

References 14 publications

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“…Such spillover and a bifunctional synthesis mechanism were demonstrated by infrared spectroscopy to occur during methanol synthesis from CO 2 -containing reactants [8,38]. There is also evidence that reconstruction of Cu particles supported on ZnO [26][27][28][29] Although we detect Cu(II) in our Cu/SiO 2 catalyst, the fraction of the Cu atoms in this form does not correlate with the rate of methanol synthesis. Other groups have already concluded that Cu metal is the only required form of Cu at least for CO 2 -containing synthesis gas reactants [11,12], and have explicitly rejected the presence of Cu(I) in working catalysts.…”

Section: Discussionmentioning

confidence: 63%

“…Incomplete reductions of Cu-ZnO/Al 2 O 3 at 503 K [16,17] and of Cu/SiO 2 at 500 K [28,36,37] have been reported and the reduction of CuO x phases may lead to an increase in reaction rates with time on stream. van der Grift et al [36,37] found by temperature programmed reduction (TPR) that several copper hydrosilicate phases reduced only above 600 K. Brands et al [28] found that Cu metal surface area increased, when a Cu/SiO 2 catalyst previously reduced at 600 K was re-reduced at 700 K. Clausen et al [26] reported that the morphology of Cu particles formed on SiO 2 by reduction in various synthesis gas mixtures at 493 K was insensitive to gas composition. Although Cu particle sizes were not reported, inspection of the EXAFS data presented with the paper indicates that the Cu particles on SiO 2 were similar in size to the particles on ZnO, for which dynamical behavior was clearly observed.…”

Section: Discussionmentioning

confidence: 99%

“…The small Cu particles required for high volumetric productivity form in a narrow range of pre-treatment temperatures. Crystallite growth is rapid in H 2 well below 700 K, but complete reduction requires temperatures above 500 K. Brands, et al [28] recently reported that Cu in 14% Cu/7% Zn/SiO 2 became reduced in H 2 at 693 K but spontaneously re-oxidized when He or vacuum replaced the H 2 atmosphere. Tohji et al [29] reported similar behavior for Cu in a Cu/ZnO catalyst reduced in H 2 between 400 and 550 K, with re-oxidation observed below 400 K in non-reducing environments.…”

Section: Introductionmentioning

confidence: 99%

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New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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X-ray absorption spectroscopic studies from several different groups provide a consistent structural picture of methanol synthesis catalysts. Copper metal is the principal Cu species detected in all in-situ XAS studies. A small amount of Cu(II) persisted in many samples reduced below 600 K, but it appears to be catalytically irrelevant. Cu(I) was not detected in any of the in-situ XAS studies. The Zn structure did not change in response to chemical treatments in any of the ZnO-containing methanol synthesis catalysts.We conclude that the slow approach to steady-state rate of methanol synthesis from CO/H 2 mixtures cannot result from changes in the Cu metal component of Cu/SiO 2 catalysts. By eliminating this possibility, we provide indirect evidence for the proposal that initial induction periods reflect slow changes in the surface of the SiO 2 or ZnO component in the catalysts. A bifunctional mechanism involving the formation of formate from CO on support hydroxyl groups would increase methanol synthesis rates as OH groups are formed by hydrolysis of Si-O bonds using the H 2 O formed in slow methanation side reactions. The bifunctional mechanism is not required for the synthesis of methanol from CO 2 -containing mixtures, because formate can form on Cu directly from CO 2 and H 2 .

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Meitzner¹,

Iglesia

1999

Catalysis Today

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“…Milling in synthetic air (20% O 2 in N 2 , 99.999% pure) was performed at a pressure of 2 bar after evacuation, filling with this gas and again evacuation to 10 -6 mbar. The Cu 0 specific surface areas of Cu/ZnO samples were determined by N 2 O chemisorption according to the method described in [15] using Thermogravimetic Analysis (TGA). Prior to the chemisorption experiments, the samples were pre-treated in Ar and reduced in H 2 /Ar (see below).…”

Section: Methodsmentioning

confidence: 99%

Oxidation and reduction in copper/zinc oxides by mechanical milling

Castricum¹,

Bakker²,

Poels³

2001

Materials Science and Engineering: A

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When zinc oxide is milled under vacuum or in the presence of oxygen, creation of various types of defects results in an increased amorphous fraction, as well as higher surface area. Mechanochemical reactions occur when copper and copper oxides are milled together with zinc oxide: oxidation of copper and copper oxides takes place in the presence of oxygen, whereas reduction takes place under vacuum. These reactions are promoted by the presence of ZnO. Formation of a Cu 2 O-like intermediate is suggested, which is not observed when milled without ZnO. The various resulting copper species reduce at different temperatures in H 2 atmosphere. Both Cu 0 specific surfaces and BET surfaces are substantially increased for all milled Cu/ZnO samples, making this method an interesting alternative for the preparation of promoted heterogeneous catalysts.

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“…[10]. For chemisorption measurements the samples were calcined for 12 h in situ in an Ar-flow (99.999% pure at 120 ml/min) after heating up at 200 K/h to 508 K; at 100 K/h to 523 K; cooling in Ar to ambient and subsequently reduced for 1 h in Ar/H 2 (at a ratio of 33/66; total flow: 120 ml/min; hydrogen purity: 99.996%) with an identical temperature programme.…”

Section: Methodsmentioning

confidence: 99%

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Huang¹,

Kramer²,

Wieldraaijer³

et al. 1997

Catalysis Letters

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Methanol Synthesis over Cu/ZnO Catalysts Prepared by Ball MillingHuang, L.; Kramer, G.J.; Wieldraaijer, W.; Brands, D.S.; Poels, E.K.; Castricum, H.L.; Bakker, H. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Cu/ZnO catalysts (with a Cu/Zn atomic ratio of 30/70) have been prepared by high intensity mechanical mixing of copper and zinc oxide powder in air and under vacuum. During milling in vacuum gradual amorphisation of the constituents occurs, as evidenced by broadening of the Cu 0 and ZnO diffraction peaks in XRD, but the two original phases remain. The result of such treatment is a catalyst with low BET area and low Cu metal surface area. Consequently, the activity of the vacuum milled samples in batch methanol production from synthesis gas (CO/CO 2 /H 2 20/5/75) at 50 bar and 250 C is low. Milling in air leads to oxidation of the copper metal phase and much higher BET surface area and, after reduction, Cu metal surface area. Prolonged milling times in air result in more than 90% Cu 2 formation as evidenced by TPR. Activity in methanol synthesis for the air milled samples is comparable to a conventional Cu/ZnO catalyst prepared by coprecipitation. It is concluded that high intensity ball milling at ambient conditions is a promising method to prepare mixed oxide catalysts or catalyst precursors.

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The relation between reduction temperature and activity in copper catalysed ester hydrogenolysis and methanol synthesis

Cited by 53 publications

References 14 publications

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

New insights into methanol synthesis catalysts from X-ray absorption spectroscopy

Oxidation and reduction in copper/zinc oxides by mechanical milling

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