Catalytic effect of metal oxides on thermal-decomposition reactions. I. The mechanism of the molten-phase thermal decomposition of potassium chlorate in mixtures with potassium chloride and potassium perchlorate

Rudloff, Winfried K.; Freeman, Eli S.

doi:10.1021/j100725a006

Cited by 25 publications

(10 citation statements)

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“…The exotherms attributed to chlorate decomposition in the potassium chlorate/Fe‐bearing phase mixtures occurred within the same temperature range as the melting temperature of potassium chlorate, which likely obscured potassium chlorate melting endotherms (Figure ). This phenomenon has been observed in previous analyses investigating the thermal decomposition of potassium chlorates in the presence of metal oxides (Rudloff & Freeman, ). The 25‐μmol Fe‐bearing phase and 5‐mg palagonite data were not plotted to permit easier comparisons between sample treatments.…”

Section: Resultssupporting

confidence: 78%

“…Potassium chlorate by itself produced a broad oxygen release peak at 482°C (Figure ), a sharp endotherm peak at 355°C, and a broad exotherm concurrent with the oxygen release (Figure and Table ). The endotherm (355°C; Figure ) was caused by potassium chlorate melting (Pourmortazavi et al, ; Rudloff & Freeman, ), while the broad exotherm (497°C) and associated oxygen release (Figure ) were caused by the thermal decomposition of potassium chlorate into potassium chloride (reaction ; Pourmortazavi et al, ).

{2KClO}_{3} \to 2KCl + {3O}_{2}

…”

Section: Resultsmentioning

confidence: 99%

“…Analyses of Fe‐bearing phases mixed with perchlorates lowered the thermal decomposition and oxygen release temperatures of perchlorates and were more consistent with SAM data from Gale Crater samples (Sutter et al, , ). Fe‐bearing phases are known to have a catalytic effect on perchlorate decomposition, reducing the temperature at which they decompose (Rudloff & Freeman, ; Zhang et al, ). The interaction between the Fe cation (Fe 2+ or Fe 3+ ) in the mineral and the unshared electron pairs in the perchlorate anion weakens the oxygen‐chlorine bond in the perchlorate and thus catalyzes decomposition of the perchlorate to a lower temperature (Zhang et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Chlorate/Fe‐Bearing Phase Mixtures as a Possible Source of Oxygen and Chlorine Detected by the Sample Analysis at Mars Instrument in Gale Crater, Mars

et al. 2018

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Oxygen and HCl gas releases detected by the Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover in several Gale Crater samples have been attributed to the thermal decomposition of perchlorates and/or chlorates. Previous experimental studies of perchlorates mixed with Fe-bearing phases explained some but not all of the evolved oxygen releases and cannot explain the HCl releases. The objective of this paper was to evaluate the oxygen and HCl releases of chlorates and chlorate/Fe phase mixtures in experimental studies and SAM evolved gas analysis data sets. Potassium, magnesium, and sodium chlorate were independently mixed with hematite, magnetite, ferrihydrite, and palagonite and analyzed in a thermal evolved gas analyzer configured to operate similarly to the SAM instrument. Fe phases depressed the chlorate decomposition temperature 3-214°C and consumed up to 75% of the evolved oxygen from chlorate decomposition. Chlorate/Fe phase mixtures have oxygen and HCl releases consistent with some samples analyzed by SAM. Reported oxychlorine abundances based on calculations using oxygen detected by SAM could be minimum values because Fe phases consume evolved oxygen. The results of this work demonstrate that chlorates could be present in the Martian soil and that oxygen and HCl release temperatures could be used to constrain which chlorate cation species are present in samples analyzed by SAM. Knowledge of which chlorates may be present in Gale Crater creates a better understanding of the detectability of organics by evolved gas analysis, habitability potential, and the chlorine cycle on Mars.Plain Language Summary The Sample Analysis at Mars (SAM) instrument on board the Curiosity rover heats Martian soil and then detects the gases produced from the breakdown of chemicals. The SAM instrument has detected oxygen and hydrochloric acid (HCl) gas in several Gale Crater samples, which have been attributed to perchlorates (ClO 4 À ) and/or chlorates (ClO 3 À ). In this study, we mixed chlorates with iron minerals that exist on Mars (e.g., hematite). These mixtures and pure chlorates were analyzed in a SAM-like laboratory instrument. Oxygen and HCl gas releases were compared to SAM data sets. Iron minerals decreased the chlorate breakdown temperature and the amount of oxygen produced. Chlorate/iron mineral mixtures have oxygen and HCl releases consistent with some samples analyzed by SAM. Reported perchlorate/chlorate abundances based on calculations using oxygen detected by SAM could be minimum values because iron minerals decrease the amount of oxygen produced from chlorates. These results demonstrate that chlorates could be present on Mars and that oxygen and HCl release temperatures could be used to constrain which type of chlorates are present in SAM samples. Knowledge of which chlorates may be present in Gale Crater creates a better understanding of the detectability of organic material by SAM, habitability potential, and the chlorine cycle on Mars. ment. Perchlorate was first det...

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Section: Resultssupporting

confidence: 78%

{2KClO}_{3} \to 2KCl + {3O}_{2}

…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Chlorate/Fe‐Bearing Phase Mixtures as a Possible Source of Oxygen and Chlorine Detected by the Sample Analysis at Mars Instrument in Gale Crater, Mars

et al. 2018

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“…Na, K, and Ca perchlorate thermally decomposed into chlorides and evolved O 2 with peaks at 578,~600, and 486 • C, respectively (reactions 3-5; Table 2) Na, K, and Ca perchlorate did not evolve HCl release peaks within the temperature range of SAM [45,49,50]. However, some studies suggested that Ca perchlorate starts to evolve HCl at the high end of the SAM temperature range due to reactions with water [25].…”

Section: Perchloratesmentioning

confidence: 99%

A Review of Sample Analysis at Mars-Evolved Gas Analysis Laboratory Analog Work Supporting the Presence of Perchlorates and Chlorates in Gale Crater, Mars

et al. 2021

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The Sample Analysis at Mars (SAM) instrument on the Curiosity rover has detected evidence of oxychlorine compounds (i.e., perchlorates and chlorates) in Gale crater, which has implications for past habitability, diagenesis, aqueous processes, interpretation of in situ organic analyses, understanding the martian chlorine cycle, and hazards and resources for future human exploration. Pure oxychlorines and mixtures of oxychlorines with Mars-analog phases have been analyzed for their oxygen (O2) and hydrogen chloride (HCl) releases on SAM laboratory analog instruments in order to constrain which phases are present in Gale crater. These studies demonstrated that oxychlorines evolve O2 releases with peaks between ~200 and 600 °C, although the thermal decomposition temperatures and the amount of evolved O2 decrease when iron phases are present in the sample. Mg and Fe oxychlorines decompose into oxides and release HCl between ~200 and 542 °C. Ca, Na, and K oxychlorines thermally decompose into chlorides and do not evolve HCl by themselves. However, the chlorides (original or from oxychlorine decomposition) can react with water-evolving phases (e.g., phyllosilicates) in the sample and evolve HCl within the temperature range of SAM (<~870 °C). These laboratory analog studies support that the SAM detection of oxychlorine phases is consistent with the presence of Mg, Ca, Na, and K perchlorate and/or chlorate along with possible contributions from adsorbed oxychlorines in Gale crater samples.

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“…In the first step, ClO − 4 decomposed into ClO − 3 and O 2 , as seen in reactions (4) and (5) [8]. In the following step, ClO − 3 decomposed according to the mechanism proposed by Rudloff and Freeman [29], as seen in reactions (6) and (7). The reactions are as follows:…”

Section: G Hypothetic Mechanism Analysis Of Liclo 4 Decompositionmentioning

confidence: 97%

Catalyst for Lithium Perchlorate Decomposition

Zhang

Yan

Qiu

et al. 2015

Journal of Propulsion and Power

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The use of metal oxide additives to modify the ability of solid propellants and other energetic materials has been the topic of much study. This work reports the enhancement of the decomposition of lithium perchlorate (LiClO 4 ) by means of employing Ce x Cu 1−x O 1x as a catalyst. The Ce x Cu 1−x O 1x composite catalysts synthesized through the collosol-gelling method with different mole ratios were designed to strongly enhance LiClO 4 decomposition through comparison with blank tests. The synthesized catalysts were characterized by scanning electron microscope, Brunauer-Emmett-Teller, x-ray diffraction, x-ray photoelectron spectra, and H 2 -TPR analyses. Results showed that a solid solution was formed in the Ce x Cu 1−x O 1x catalysts. The Ce x Cu 1−x O 1x composite catalysts showed more lattice defects, smaller crystallites, larger surface area, and more oxygen vacancies than pure CuO and CeO 2 samples because of the interaction of Ce and Cu ions. Lattice defects, especially the reduced surface sites (that is, Ce 3 , Cu , and oxygen vacancies), played dominant roles in catalytic reactions of LiClO 4 decomposition. In addition, a hypothetical mechanism for LiClO 4 catalytic decomposition of the Ce x Cu 1−x O 1x catalyst was proposed.

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Catalytic effect of metal oxides on thermal-decomposition reactions. I. The mechanism of the molten-phase thermal decomposition of potassium chlorate in mixtures with potassium chloride and potassium perchlorate

Cited by 25 publications

References 2 publications

Chlorate/Fe‐Bearing Phase Mixtures as a Possible Source of Oxygen and Chlorine Detected by the Sample Analysis at Mars Instrument in Gale Crater, Mars

Chlorate/Fe‐Bearing Phase Mixtures as a Possible Source of Oxygen and Chlorine Detected by the Sample Analysis at Mars Instrument in Gale Crater, Mars

A Review of Sample Analysis at Mars-Evolved Gas Analysis Laboratory Analog Work Supporting the Presence of Perchlorates and Chlorates in Gale Crater, Mars

Catalyst for Lithium Perchlorate Decomposition

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