A Comparative Study of Partial Oxidation of Methanol over Zinc Oxide Supported Metallic Catalysts
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A Comparative Study of Partial Oxidation of Methanol over Zinc Oxide Supported Metallic Catalysts Wang Jianxin Æ Luo Laitao
Received: 12 July 2008 / Accepted: 20 August 2008 / Published online: 18 September 2008 Ó Springer Science+Business Media, LLC 2008
by technical difficulties in storage, transportation and distribution of hydrogen. The difficulties may be avoided by an on-board production of hydrogen from liquid fuels. Methanol is a promising fuel candidate because of its easy handling, high H/C ratio, and low price [2]. Hydrogen may be produced directly from methanol according to a number of different processes such as methanol decomposition (MD) [3], steam reforming (SRM) [4, 5], oxidative steam reforming (OSRM) [6, 7] and partial oxidation (POM) [8–11].
Abstract Au/ZnO, Pd/ZnO and Au–Pd/ZnO catalysts were prepared by PVP-stabilized reduction method by C2H5OH. The catalysts have been used successfully for hydrogen production by partial oxidation of methanol (POM). The influence of Au, Pd and Au–Pd on the performance of supported catalysts for POM has been investigated. The prepared samples were characterized by ICP, XRD, BET, TPR and TPD. The results show that the Au–Pd/ZnO catalyst are more active and exhibit higher hydrogen selectively compared to the Pd/ZnO and Au/ZnO catalyst, the methanol conversion of 99.5% and hydrogen selectivity of 65.6% were obtained at 573 K. The enhanced activity and stability of the bimetallic Au–Pd/ZnO catalyst has been explained in terms of the higher dispersion and basic density, smaller particles of gold and synergetic effect between gold and palladium.
SRM CH3 OH þ H2 O ! 3H2 þ CO2 DH298 K ¼ 49:0 kJ/mol
ð2Þ
Keywords Au–Pd catalyst ZnO support Partial oxidation of methanol Hydrogen generation
POM CH3 OH þ 1/2O2 ! 2H2 þ CO2 DH298 K ¼ 192:2 kJ/mol
ð3Þ
1 Introduction Fuel cell technology is promising for efficient conversion of chemical energy into electrical energy with negligible emission of pollutant [1]. There are many type of fuel cell under development. Among them, the proton exchange membranes fuel cell (PEMFC) is the most promising fuel cell and may be applied to mobile cars, cell phones and notebook computers. However, the application is hindered W. Jianxin L. Laitao (&) Institute of Applied Chemistry, Nanchang University, Nanchang 330031, Jiangxi, China e-mail: [email protected]
DM
CH3 OH ! 2H2 þ CO
DH298 K ¼ 90:1 kJ/mol ð1Þ
OSRM CH3 OH þ 1=2H2 O + 1/4H2 ! 5=2H2 þ CO2 DH298 K ¼ 12 kJ/mol ð4Þ Partial oxidation of methanol (POM, Eq. 3) in the absence of steam offers several advantages over steam reforming, as the reaction is exothermic, uses air or oxygen as oxidant instead of steam and so steam generation unit is not required. Therefore, POM has been suggested as a suitable route for hydrogen extraction from methanol. The POM reaction had been studied over copper [12] and palladium based [8, 9] catalysts. Unfortunately, these catalysts produce considerable amount of carbon monoxide as a by-product. CO is a poison to fuel cell anodes. If th
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