Methanol synthesis catalysts based on cesium/copper/zinc oxide/metal oxide (metal = aluminum, chromium, gallium): genesis from coprecipitated hydrotalcite-like precursors, solid-state chemistry, morphology, and stability

Nunan, John; Himelfarb, P.B.; Herman, R.G.; Klier, K.; Bogdan, Charles E.; Simmons, G.W.

doi:10.1021/ic00319a023

Cited by 68 publications

(13 citation statements)

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“…We have shown that when K&O, is added by impregnation, the basicity of the impregnating solution can cause a restructuring of the surface of the material, thereby affecting both the total and the copper surface area [12]; the decrease of the copper surface area, however, was also found to be brought about partially by the potassium compound covering part of the copper. Such a restructuring effect has also been reported by Nunan et al [32] in relation to Cs-doped Cu/ZnO/Al,O, catalysts; the same authors found that when Al was replaced by Cr, this effect did not occur. We have shown from temperature programmed reduction profiles that the addition of &CO3 also influences the Cu-ZnO interaction in a Cu/ZnO/Al,O, catalyst [12]; when &CO, had been added, the copper oxide appeared to be more easily reduced than when no dopant had been added.…”

Section: Alteration Of Other Catalyst Properties By the Addition Of Psupporting

confidence: 77%

The synthesis of higher alcohols using modified Cu/ZnO/Al2O3 catalysts

1992

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This paper gives a review of research work in the synthesis of higher alcohols over catalysts based on Cu/ZnO/Al,O,, emphasizing three main topics: (i) the effect on selectivity of the addition of several compounds to this catalyst, (ii) the effect on selectivity of the reaction conditions used, and (iii) the reaction network leading to the different products found. Although the use of aLkali compounds has been studied most extensively, other corn~un~, for example those containing manganese, also appear to be promising additives. The process conditions are rather critical and this may cause some practical difficulties in industrial plants. An extended aldol condensation mechanism is proposed which can explain the product distribution found.

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Section: Alteration Of Other Catalyst Properties By the Addition Of Psupporting

confidence: 77%

The synthesis of higher alcohols using modified Cu/ZnO/Al2O3 catalysts

1992

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“…At higher temperatures the average crystallite size of the spinel in the h440i directions is larger in the COZNAL sample than in the COAL sample. However, one has to keep in mind that the half-width parameters were extracted from a single peak model of the 440 reflection, even though the spinel crystallites most likely had anisotropic morphology shortly after the spinel phases were formed, since the particles/crystallites of the precursor LDH are known for their sheet-like, platelet, or platy morphology (Nunan et al, 1989;Kelkar & Schutz, 1997;Adachi-Pagano et al, 2003). In that case, the average crystallite size in e.g.…”

Section: Figure 11mentioning

confidence: 99%

A comparativein situRietveld refinement study: thermal decomposition and transformation of CoAl and CoZnAl layered double hydroxides

Johnsen

Norby

2008

J Appl Cryst

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Rietveld refinement based on in situ X‐ray powder diffraction (XRPD) data was combined with thermogravimetric analysis (TGA) and mass spectrometry (MS) to study and compare the phase transformations, thermal stability, microstructural and structural changes of two cobalt‐containing nitrate‐based layered double hydroxides (LDHs) upon heating in a controlled inert atmosphere of nitrogen. The XRPD data were collected, using synchrotron X‐ray radiation, with a time resolution of 107 s, which made it possible to carry out detailed structural studies of the initial layered double hydroxides as well as their decomposition products: spinel for a CoAl–NO3 LDH and spinel/zincite for a CoZnAl–NO3 LDH. Correlating these data with those from the TGA–MS analyses gives us information about the transformation mechanisms. Rietveld refinements of the two spinel phases reveal remarkable differences. The a axis of the spinel formed by decomposition of the CoAl–NO3 LDH increases almost linearly from approximately 598 to 1163 K, mainly due to the dominating thermal expansion, whereas the a axis of the spinel formed by decomposition of the CoZnAl–NO3 shows a more complex temperature dependency. Between approximately 698 and 1073 K, the a axis is almost constant due to pronounced chemical interaction with an additional amorphous phase and the zincite phase, whereas from 1073 up to 1163 K it increases linearly. Calculations, based on the results of the Rietveld refinements, of the size of the octahedral and tetrahedral coordination polyhedra in the spinel show that the octahedra shrink and the tetrahedra expand with increasing temperature. The unusual thermal behaviour of the octahedra is discussed and attributed to the low formation temperature of the cobalt aluminium spinel phase. Finally, the intensity of a low‐angle scattering (LAS) signal observed in the XRPD patterns was correlated with the decomposition of the LDH, and determination of the specific surface areas gave the temperature‐dependent BET surface areas.

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“…Furthermore, Ga 2 O 3 was reported as catalyst promotor by Fujitani et al [21] and Toyir et al [22]. In addition, studies presented in literature [23,24,25,26] have already shown that it is possible to obtain LDH compounds with Cr and Ga as trivalent cation. Binary pure and well crystallized Cu,Cr LDH was prepared by Jiao et al [25] with a molar ratio of 2 : 1.…”

Section: Introductionmentioning

confidence: 97%

“…Venugopal et al [23]described ternary Cu/Zn/Cr 2 O 3 catalysts with a constant Cu content of 50 mol% [23] as well as quaternary Cu,Zn,Al,Ga catalysts [26], which were used for dimethyl ether synthesis. [26]Additionally, Nunan et al [24] presented Cs-doped Cu,Zn,X (X = Cr, Ga) catalysts obtained from LDH.…”

Section: Introductionmentioning

confidence: 99%

Ternary and quaternary Cr or Ga-containing ex-LDH catalysts—Influence of the additional oxides onto the microstructure and activity of Cu/ZnAl2O4 catalysts

et al. 2015

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The stepwise substitution of Al by Cr and Ga leads to quaternary LDH precursors for Cu/ZnM 2 O 4 (M = Al, Ga, Cr) catalysts. With the substitution of Al by Cr the interaction of the Cu phase with the oxide matrix is gradually weakened, which is caused by the participation of the chromium oxide phase in the redox processes during catalyst preparation. Such reactive Cr oxide matrix is less efficient than the inert Al oxide matrix in stabilizing the special microstructure of Cu/ZnM 2 O 4 catalysts. These weakened interactions led to a lowering of the Cu particle embedment, coinciding with a pronounced Cu crystallite growth during reduction. Both effects partially compensate each other and a maximum in Cu surface area is observed for intermediate Cr contents. In the Ga-substituted catalysts, two distinct Cu species were found for high Ga contents. This is attributed to the presence of partially crystalline spinel and the resulting different strength of interface interaction of the CuO phase with the crystalline and the amorphous oxide. After reduction Cu catalysts with similar average Cu particle sizes as well as Cu surface areas were obtained. In both sample series, the catalytic activity in methanol synthesis does not scale with the Cu surface area and the experiments show that a strong interaction to the oxide is necessary to gain stability and activity of the Cu phase. Al substitution thus confirms that interface interactions between Cu and the oxide seem to beneficially affect the activity of the Cu particles and the optimal catalyst requires a compromise of exposed surface and interface. * Ga20-calc CZA-calc Ga15-calc Ga10-calc Ga5-calc Ga25-calc Ga30-calc Ga33-calc

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Methanol synthesis catalysts based on cesium/copper/zinc oxide/metal oxide (metal = aluminum, chromium, gallium): genesis from coprecipitated hydrotalcite-like precursors, solid-state chemistry, morphology, and stability

Cited by 68 publications

References 1 publication

The synthesis of higher alcohols using modified Cu/ZnO/Al2O3 catalysts

The synthesis of higher alcohols using modified Cu/ZnO/Al2O3 catalysts

A comparativein situRietveld refinement study: thermal decomposition and transformation of CoAl and CoZnAl layered double hydroxides

Ternary and quaternary Cr or Ga-containing ex-LDH catalysts—Influence of the additional oxides onto the microstructure and activity of Cu/ZnAl2O4 catalysts

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