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Title: Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles

Abstract

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

Authors:
; ; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - NE
OSTI Identifier:
912361
Report Number(s):
INL/JOU-05-00546
Journal ID: ISSN 0360-3199; IJHEDX; TRN: US200801%%795
DOE Contract Number:
DE-AC07-99ID-13727
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Hydrogen Energy; Journal Volume: 32; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
08 - HYDROGEN; ATMOSPHERIC PRESSURE; CATALYSTS; KINETICS; OXIDES; PLATINUM; STABILITY; SULFUR; SULFURIC ACID; SURFACE AREA; VELOCITY; WATER; Catalyst stability; Hydrogen; Sulfur cycles; Sulfuric acid decomposition

Citation Formats

Daniel M. Ginosar, Lucia M. Petkovic, Anne W. Glenn, and Kyle C. Burch. Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles. United States: N. p., 2007. Web. doi:10.1016/j.ijhydene.2006.06.053.
Daniel M. Ginosar, Lucia M. Petkovic, Anne W. Glenn, & Kyle C. Burch. Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles. United States. doi:10.1016/j.ijhydene.2006.06.053.
Daniel M. Ginosar, Lucia M. Petkovic, Anne W. Glenn, and Kyle C. Burch. Thu . "Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles". United States. doi:10.1016/j.ijhydene.2006.06.053.
@article{osti_912361,
title = {Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles},
author = {Daniel M. Ginosar and Lucia M. Petkovic and Anne W. Glenn and Kyle C. Burch},
abstractNote = {The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.},
doi = {10.1016/j.ijhydene.2006.06.053},
journal = {International Journal of Hydrogen Energy},
number = 4,
volume = 32,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
  • Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on platinum supported on titania (rutile) catalysts to investigate the causes of catalyst deactivation under sulfuric acid decomposition reaction conditions. Samples of 1 wt% Pt/TiO2 (rutile) catalysts were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different times on stream (TOS) between 0 and 548 h. Post-operation analyses of the spent catalyst samples showedmore » that Pt oxidation and sintering occurred under reaction conditions and some Pt was lost by volatilization. Pt loss rate was higher at initial times but total loss appeared to be independent of the gaseous environment. Catalyst activity showed an initial decrease that lasted for about 66 h, followed by a slight recovery of activity between 66 and 102 h TOS, and a period of slower deactivation after 102 h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity and the activity profile suggested that a complex dynamical situation involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes affected catalyst activity in a non-monotonic way.« less
  • Abstract not provided.
  • Simple thermochemical cycles-those in which only one element besides H, O, and sometimes Cl undergoes oxidation and reduction-can be treated conceptually as a series of acid-base reactions. For workable cycles involving oxides, the Lux-Flood acid-base model is used; the maximum temperature for a workable cycle is 1300 K. Simple oxide cycles are classified according to their chemistries as (A) cycles involving stable high-oxidation-state oxides, (B) cycles involving unstable high-oxidation-state oxides, and (C) cycles involving unstable low-oxidation-state oxides. In type A and type B cycles, bases drive steam oxidation reactions and acids drive reductive thermal decompositions. In type C cycles, basesmore » drive reduction and acids drive oxidation. Salts are formed in all of these cycles; completion of the cycles requires thermochemical splitting of the salts to regenerate the acid and bases. It is postulated that the standard enthalpy of reaction between the strongest acid and the strongest base used in a cycle is a measure of the chemical energy provided to the cycle by acid-base reactions. It is also shown that-in workable cycles-this standard enthalpy value must ie between -210 and -400 kJ/mol of evolved H/sub 2/. The acid-base postulates are combined with oxide decomposition temperatures in a scheme that can serve as a guide for the experimental development of new thermochemical cycles.« less
  • In this communication experiments are described which delineate the effects of heat and visible light on platinum in deoxygenated water. Hydrogen is evolved when platinum and water are heated at relatively low temperatures in the range of 130 to 210/sup 0/C. No significant amounts of oxygen were detected in the thermochemical reactions. Upon illuminating platinized chlorophyll a, hydrogen is detected as well as a small amount of oxygen of uncertain origin. No molecular hydrogen and oxygen were detected when Pt in water was illuminated in the visible wavelength region. 3 figures.
  • Thermochemical cycles for water splitting employ thermal energy to drive a cyclic series of chemical reactions, the sum of which is just H/sub 2/O + thermal energy = H/sub 2/ + 1/2 O/sub 2/. It was shown previously that cerium (IV) oxide, CeO/sub 2/, reacts with alkali metal hydrogen phosphates - MH/sub 2/PO/sub 4/ or M/sub 2/HPO/sub 4/, where M = Li, Na, K - at > 600/sup 0/C to produce O/sub 2/(g), cerium(III) phosphate, CePO/sub 4/, and alkali metal orthophosphates, M/sub 3/PO/sub 4/. When M = Na or K, the double phosphate M/sub 3/Ce(PO/sub 4/)/sub 2/ forms from themore » CePO/sub 4/ and the M/sub 3/PO/sub 4/. In seeking ways to use these reactions in thermochemical cycles, it was discovered that steam will oxidize CePO/sub 4/ to CeO/sub 2/ in the presence of lithium halides - LiX, where X = Cl, Br, I - according to the following reaction: 2CePO/sub 4/(c) + 6LiX(c,l) + 4H/sub 2/O(g) = 2CeO/sub 2/(c) + 2LiPO/sub 4/(c) + 6HX(g) + H/sub 2/(g), (c), (l), and (g) refer respectively to the states crystalline, liquid, and gaseous. This paper describes studies of this reaction and its use in thermochemical cycles based on the Ce(IV)/Ce(III) redox couple.« less