Noble Metal Catalyzed Hydrogen Generation from Formic Acid in Nitrite-Containing Simulated Nuclear Waste Media

King, R. B.; Bhattacharyya, N. K.; Wiemers, K.D.

doi:10.1021/es950524c

Cited by 14 publications

(17 citation statements)

References 15 publications

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“…12 Data from the bead-frit runs cannot be used to test this finding, since there were large concentrations of nitrate in all tests and no systematic variations to initial nitrite or nitrate concentrations. Pd was obviously less active for hydrogen generation than Rh and Ru at comparable loadings in the nitrite and nitrate rich bead-frit sludge feed system.…”

Section: Wsrc-sti-2008-00002mentioning

confidence: 98%

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Noble Metal Chemistry and Hydrogen Generation During Simulated DWPF Melter Feed Preparation

Koopman¹

2008

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Section: Wsrc-sti-2008-00002mentioning

confidence: 98%

“…12 Two comparisons were made to test this, one with the frit pair at 0.1 and 0.2 wt%, and a second with the matching bead pair.…”

Section: Figure 38 Nitrite and Rh Versus Hydrogenmentioning

confidence: 99%

Noble Metal Chemistry and Hydrogen Generation During Simulated DWPF Melter Feed Preparation

Koopman¹

2008

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“…All reactions were conducted in glass reaction vessels of ∼550 mL total capacity equipped with a threaded plug and O-ring adapter used in the previous work ( − ). A pressure gauge was attached to the system.…”

Section: Experimental Approachmentioning

confidence: 99%

“…The reducing properties of formic acid can lead to a number of difficulties in the processing of nuclear wastes. Thus the catalytic decomposition of formic acid can lead to the unwanted generation of hydrogen by the reaction The catalytic role of the noble metals Ru, Rh, and Pd present in the wastes as uranium fission products () for hydrogen generation from formic acid is discussed in previous papers ( − ). In addition, formic acid can reduce nitrate to ammonia in the presence of the noble metals Rh and/or Pd under certain conditions as discussed in another previous paper ().…”

Section: Introductionmentioning

confidence: 99%

Redox Potential Monitoring as a Method To Control Unwanted Noble Metal-Catalyzed Hydrogen Generation from Formic Acid Treatment of Simulated Nuclear Waste Media

King¹,

Bhattacharyya²,

Smith³

et al. 1998

Environ. Sci. Technol.

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Simulants for the Hanford Waste Vitrification Plant feed containing the major nonradioactive components Al, Cd, Fe, Mn, Nd, Ni, Si, Zr, Na, CO3 2-, NO3 -, and NO2 - were used to study redox potential changes in reactions of formic acid at 90 °C catalyzed by the noble metals Ru, Rh, and/or Pd found in significant quantities in uranium fission products. Such reactions were monitored using gas chromatography to analyze the CO2, H2, NO, and N2O in the gas phase and a redox electrode to follow redox potential changes as a function of time. In the initial phase of formic acid addition to nitrite-containing feed simulants, the redox potential of the reaction mixture rises typically to +400 mV relative to the Ag/AgCl electrode because of the generation of the moderately strongly oxidizing nitrous acid. No H2 production occurs at this stage of the reaction as long as free nitrous acid is present. After all of the nitrous acid has been destroyed by reduction to N2O and NO and disproportionation to NO/NO3 -, the redox potential decreases upon further formic acid addition. Hydrogen production typically begins to occur when the redox potential of the reaction mixture becomes more negative than the Ag/AgCl electrode. The experiments outlined in this paper suggest the feasibility of controlling the production of H2 by limiting the amount of formic acid used and monitoring the redox potential during formic acid treatment.

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“…Work performed at PNL during FY 1990(b), FY 1991('), FY 1992(*), and FY 1993 (Smith 1993) further documented the generation of H, and NH, in NCAW slurries treated with HCOOH. Studies at the University of Georgia under contract with Savannah River Technology Center (SRTC) (King et al 1993) (King, Bhattacharyya 1994) and PNL verified the catalytic role of noble metals in generating H2 and NH,. Laboratory-scale and pilot-scale studies at SRTC have documented the H, andNH, generation phenomena (Ritter, Zamecnik, and Hsu 1992).…”

Section: O Introductionmentioning

confidence: 99%

Evaluation of HWVP feed preparation chemistry for an NCAW simulant -- Fiscal year 1993: Effect of noble metals concentration on offgas generation and ammonia formation

Patello¹,

Wiemers²,

Bell³

et al. 1995

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SummaryThe High-Level Waste Vitrification Program is developing technology for the Department of Energy to immobilize high-level and transuranic wastes as glass for permanent disposal. Pacific Northwest Laboratory (PNL) is conducting laboratory-scale melter feed preparation studies using a HWVP simulated waste slurry, Neutralized Current Acid Waste o. A FV 1993 laboratory-scale study focused on the effects of noble metals (Pd, Rh, and Ru) on feed preparation offgas generation and NH, production. The noble metals catalyze H, and NH, production, which leads to safety concerns. The information gained from this study is intended to be used for technology development in pilot scale testing and design of the Hanford High-Level Waste Vitrification Facility. The work performed during FY 1993 was initiated under the Hanford Waste Vitrification Program (HWVP).Six laboratory-scale feed preparation tests were performed as part of the FY 1993 testing activities using nonradioactive NCAW simulant. Tests were performed with lo%, 25%, 50% of nominal noble metals content and nominal noble metals content. Also tested were 25% of the nominal Rh and a repeat of 25% nominal noble metals.The following summarizes the results of the test activities:Offgas profiles exhibited three reaction stages: I, CO? decomposition, 11, NO, destruction, and 111, Hz plus NH, formation. Hydrogen is formed during reaction stage 111 as a product of noble metals catalyzed HCOOH decomposition. The peak Hz generation rate and total Hz measured increased with noble metal concentration until a maximum level was reached at 25%-50% nominal noble metals concentration. The maximum derivative of the Hz generation rate showed an almost linear increase as a function of noble metals concentration.The observed relationship between noble metals concentration and the H, generation rate may be coupled to a higher NO, concentration at the initiation of the H, peak in the 10% nominal noble metals test compared to the 25%, 50%, and nominal tests. Higher NO; would be expected to reduce the Hz generation rate (Smith 1993).A test performed with only 25 % Rh showed significantly different behavior than the 25 % nominal noble metals test; therefore, it was concluded that the other noble metals (Pd and Ru) contributed catalytic activity to Hz production. This conclusion does not agree with the work of King at the University of Georgia (King and Bhattacharyya 1993). A replicate of this test should be performed to verify the results.Ammonia is also formed during stage 111 as a product of a reaction between HCOOH and NO,. The amount of NH, measured in the slurry following stage 111 increased as the noble metals concentration increased. Ammonia production is speculated to be related to H, production because Hz is an intermediate reactant in the NH, reaction. Therefore, as the total Hz measured increases as a function of noble metals concentration, NH, generation increases as well.Formation of a black residue in the nominal noble metals concentration test indicated the presence of red...

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Noble Metal Catalyzed Hydrogen Generation from Formic Acid in Nitrite-Containing Simulated Nuclear Waste Media

Cited by 14 publications

References 15 publications

Noble Metal Chemistry and Hydrogen Generation During Simulated DWPF Melter Feed Preparation

Noble Metal Chemistry and Hydrogen Generation During Simulated DWPF Melter Feed Preparation

Redox Potential Monitoring as a Method To Control Unwanted Noble Metal-Catalyzed Hydrogen Generation from Formic Acid Treatment of Simulated Nuclear Waste Media

Evaluation of HWVP feed preparation chemistry for an NCAW simulant -- Fiscal year 1993: Effect of noble metals concentration on offgas generation and ammonia formation

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