Elsevier

Catalysis Today

Volumes 107–108, 30 October 2005, Pages 431-435
Catalysis Today

New supported Pd catalysts for the direct transformation of ethanol to ethyl acetate under medium pressure conditions

https://doi.org/10.1016/j.cattod.2005.07.057Get rights and content

Abstract

The direct transformation of ethanol to ethyl acetate was studied over supported palladium catalysts with low palladium content (1%, w/w Pd) at 1 MPa pressure. SiO2, Al2O3, ZnO, SnO2 and WO3-ZrO2 (29%, w/w WO3) were used as supports. The catalytic behaviour of samples was related to the characteristics of the support and the presence of mono- or bimetallic entities. The best catalytic results were obtained with ZnO- and SnO2-supported catalysts, which can easily lead to alloyed palladium phases.

Introduction

There is a growing interest in developing ecofriendly chemicals and processes in the context of a new green chemistry concept. In this area, ethyl acetate is replacing the use of aromatic compounds used as solvents of paints and adhesives. However, the classical processes of obtaining ethyl acetateCH3COOH + CH3CH2OH  CH3COOCH2CH3 + H2OC2H4 + CH3COOH  CH3COOCH2CH32CH3CHO  CH3COOCH2CH3require acetic acid or acetaldehyde as feedstock and both reactants are difficult to handle due to corrosion or toxicity problems.

An alternative route to conventional processes is the production of ethyl acetate by dehydrogenative dimerization of ethanol2CH3CH2OH  CH3COOCH2CH3 + H2This alternative route shows the advantage of using only ethanol as feedstock and the production of H2, which can be used for several purposes. Moreover, if bio-derived ethanol is used, then the production of ethyl acetate will be based on biomass and the process will not depend on fossil fuels as do the above-mentioned conventional processes.

There is a commercial process (Davy process technology) which is based on the dehydrogenative dimerization of ethanol to synthesize ethyl acetate [1], [2], [3]. However, the ethyl acetate stream, which is produced over a copper-based catalyst, is impure and passes through consecutive units of selective hydrogenation and distillation to remove by-products [4].

Although several papers dealing with the use of copper-based catalysts for the above-mentioned reaction have been reported [5], [6], [7], [8], other active phases have not been extensively studied. Taking into account that the selectivity is a major problem for the production of ethyl acetate from ethanol, further studies addressed to a better knowledge of new catalysts and their catalytic behaviour are desired. One of the few studies which have been reported using other catalytic phases is that of Iwasa et al. with Pd-based catalysts (10–30%, w/w Pd loading) under atmospheric pressure conditions [9]. The authors have proposed a relation between the yielding of acetaldehyde and ethyl acetate and the presence of Pd–Zn, Pd–Ga or Pd–In alloys. However, no surface characterization of the catalysts was reported and the behaviour of catalysts was referred to Pd-alloys determined by means of X-ray diffraction (XRD) analysis [9].

The aim of this work is to evaluate the catalytic behaviour of supported palladium catalysts with low palladium content (ca. 1%, w/w Pd loading) on the ethanol transformations at 1 MPa of pressure. ZnO, SnO2, SiO2, Al2O3 and a WO3-ZrO2 mixed oxide were used as supports. The catalytic evaluation of supports and supported palladium catalysts and the surface characterization by X-ray photoelectron spectroscopy and FTIR of CO adsorption as probe molecule, allowed us to discuss the catalytic behaviour of samples in terms of the support used in the preparation and the presence of bimetallic palladium entities.

Section snippets

Preparation of catalysts

SiO2, γ-Al2O3, ZnO, SnO2 and WO3-ZrO2 supported palladium catalysts were prepared by incipient-wetness or wet impregnation methods. Commercial SiO2 (hydrophobic silica HDK-20, BET 170 m2 g−1, from Wacker) and γ-Al2O3 (T-126, BET 180 m2 g−1 from Girdler) were used. The other oxides used as supports were synthesized in our laboratory as follows: for the preparation of ZnO aqueous solutions of Zn(NO3)2·6H2O and (NH4)2CO3 were mixed at room temperature. After filtering and washing, solid was dried at

Results and discussion

Supports prepared in this work were characterized by X-ray diffraction and BET surface areas. X-ray diffraction patterns corresponded to expected ZnO and SnO2 phases. For WO3-ZrO2 (29%, w/w WO3), the pattern indicated the presence of tetragonal ZrO2, this phase was stabilized by the incorporation of tungsten. The materials showed surface area values of 70 m2 g−1 for ZnO, 135 m2 g−1 for SnO2 and 96 m2 g−1 for WO3-ZrO2. Table 1 shows catalysts prepared and their metallic content.

Surface

Conclusions

ZnO and SnO2 are appropriate supports for preparing Pd-supported catalysts with low palladium content active in the dehydrogenative dimerization of ethanol. These reducible supports favour the formation of alloyed phases, which are very effective for the dehydrogenation of ethanol to acetaldehyde. Then, in a second step, ethyl acetate is produced.

Under 1 MPa and at 523 K, Pd/ZnO catalyst (1%, w/w Pd) produces under ca. 40% ethanol conversion, an ca. 40% ethyl acetate/48% acetaldehyde mixture.

Acknowledgments

We thank MCYT (MAT 2002-01739) and CIRIT (2001SGR-00052) for financial support, A.B.S. is grateful to CONACYT (Mexico) for a Ph.D. grant.

References (20)

  • K. Inui et al.

    J. Catal.

    (2002)
  • K. Inui et al.

    Appl. Catal. A: Gen.

    (2002)
  • S. Verdier et al.

    J. Catal.

    (2003)
  • P. Légaré et al.

    Surf. Sci.

    (1989)
  • Z. Zsoldos et al.

    J. Catal.

    (1994)
  • B.E. Green et al.

    J. Catal.

    (1993)
  • J. Araña et al.

    J. Mol. Catal. A: Chem.

    (2000)
  • A. Palazov et al.

    J. Catal.

    (1975)
  • C.R. Fawcett, M.W.M. Tuck, C. Rathmell, S.W. Colley, WO 0020375...
  • N. Harris, C. Rathmell, S.W. Colley, WO 0020374...
There are more references available in the full text version of this article.

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