The platinum catalyzed hydrazine decomposition in non-nitrate acidic media

Ananiev, A.V.; Broudic, Jean-Charles; Brossard, Ph.

doi:10.1016/s0926-860x(02)00368-x

Cited by 21 publications

(10 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Being in large excess, the H + ions occupy predominantly the most energetically profitable active sites that causes the decrease of the hydrazoic acid adsorption heat and the growth of the apparent activation energy. The similar phenomenon was also observed and discussed recently for the catalytic decomposition of hydrazine in solutions of perchloric and sulfuric acids [9]. The experimental data obtained allows to conclude that in the range of small HNO 3 concentrations, the nitric acid does not participate directly in the rate-determining step of the reaction.…”

Section: Resultssupporting

confidence: 86%

Kinetics of the platinum catalyzed hydrazoic acid decomposition in acidic media

Ananiev

Shilov

Brossard

2004

Applied Catalysis A: General

View full text Add to dashboard Cite

Section: Resultssupporting

confidence: 86%

Kinetics of the platinum catalyzed hydrazoic acid decomposition in acidic media

Ananiev

Shilov

Brossard

2004

Applied Catalysis A: General

View full text Add to dashboard Cite

“…If take it into consideration that mechanism of platinum-catalyzing hydrazine decomposition in non-nitric acid, we can get these processes as follow [26]: …”

Section: U(v) → U(vi) + U(iv)mentioning

confidence: 99%

Research of thermodynamic and kinetics in preparing U(IV) by reducing and catalyzing U(VI) with hydrazine

Xia

et al. 2015

Radiochimica Acta

View full text Add to dashboard Cite

The effect of concentration of U(VI), hydrazine, nitric acid and the amount of catalyst, and the thermodynamics and kinetics of the reaction in preparing U(IV) by catalyzing and reducing U(VI) are studied in catalytic reduction of U(VI) with hydrazine as reductant and Pt as catalyst. The comparison of calculated theoretical reaction heat value and practical value is also given. The result shows that with the increase of density of U(VI) and hydrazine, increase of amount of catalyst and decrease of nitric acid, reaction rate slows down. The reaction kinetic rate equation is as follow: −d (UO 2 2+ )/d = 1.11 (UO 2 2+ ) 1.42 (N 2 H 5 + ) −0.72 (H + ), and the reaction rate constant is 1.3 × 10 −3 (mol/L) −0.81 /min when S/L is 0.008 kg/L at 50 ∘ C. The theoretical reaction equation of unit volume is as follows: = Δ f m,1 + Δ f m,2 [ (N 2 H 4 ) − (UO 2 2+ ) /2 − ]/3. The comparison shows the coincidence in 1 h of theoretical value and practical value.

show abstract

“…With certain approximation, we assumed that, similarly to catalytic decomposition of hydrazine in acidic solutions, the limiting stage of the process is the dissociation of hydrazine molecules adsorbed on the catalyst surface, followed by subsequent rapid reaction of sorbed NH 2 * radicals with hydrazine molecules in solution [5]. N In turn, N 2 H 3 * radicals decompose to form ammonia and nitrogen: The rate of this reaction is very high (k > 30 10 12 cm 3 mol 31 s 31 ) [15].…”

Section: Catalytic Decomposition Of Hydrazine In the Presence Of [Gramentioning

confidence: 99%

Catalytic decomposition of hydrazine in weakly alkaline solutions on platinum nanoparticles

et al. 2004

View full text Add to dashboard Cite

The kinetics and stoichiometry of catalytic decomposition of hydrazine in 0.01 M NaOH solutions in the presence of unstabilized ([gray] colloid) and stabilized with sodium polyacrylate ([brown] colloid) platinum nanoparticles were studied. The main decomposition products are ammonia and N 2 with H 2 impurity (up to 1.5%), i.e., hydrazine decomposition predominantly follows the stoichiometric equation 3N 2 H 4 = 4NH 3 + N 2 . The catalytic activity was studied as influenced by nanoparticle size distribution. Despite higher nanoparticle dispersion, the catalytic activity of the stabilized [brown] colloid is lower than that of the [gray] colloid. The reaction mechanism is discussed.Owing to high reduction activity, hydrazine is widely used in wet processes of the nuclear fuel cycle as stabilizer of actinide ions in lower oxidation states [1] or as nitrite scavenger [2]. The presence of hydrazine in aqueous waste is undesirable, because it often complicates treatment of liquid radioactive waste, in particular, in the course of chemical denitration [3]. It was found [4 3 6] that hydrazine is effectively decomposed in the presence of finely dispersed platinum catalyst supported on silica. However, this Pt/SiO 2 catalyst can be used only in acidic solutions because of low chemical stability of the support (silica) in alkaline and carbonate solutions. Hence, search for new catalytic materials stable in the above media is of particular importance.Colloids of platinum group metals are highly selective catalysts for many chemical reactions [7,8]. Platinum nanoparticles exhibit catalytic properties both in oxidation (e.g., of 2-propanol [9]) and reduction (reaction of molecular hydrogen with methylviologen [10]) processes. It was found [10] that the catalytic activity of platinum nanoparticles prepared by various procedures is considerably different.In this work we continued a study of the catalytic properties of platinum nanoparticles, with hydrazine decomposition in weakly alkaline solutions as example. EXPERIMENTAL Preparation of Platinum Nanoparticles and Their PropertiesCatalytic decomposition of hydrazine was studied using two types of colloids prepared by different procedures.In the first procedure, colloidal platinum was prepared directly in the reaction system by injection of an aliquot of H 2 PtCl 6 solution into a temperaturecontrolled working solution of sodium hydroxide (10 32 NaOH) containing excess hydrazine. In this case, platinum was rapidly reduced to the finely dispersed metal and the solution became gray due to platinum colloid; the [gray] colloid was stable within the entire experimental time. This colloid catalyzed decomposition of excess hydrazine.In the second case, platinum nanoparticles were prepared according to the standard procedure [10] by reduction of H 2 PtCl 6 or K 2 PtCl 6 in 10 32 M NaOH solution with molecular hydrogen in the presence of sodium polyacrylate stabilizer. As a result, stable brown colloidal solution was prepared ([brown] colloid).The size distributions of platinum nanopa...

show abstract

The platinum catalyzed hydrazine decomposition in non-nitrate acidic media

Cited by 21 publications

References 3 publications

Kinetics of the platinum catalyzed hydrazoic acid decomposition in acidic media

Kinetics of the platinum catalyzed hydrazoic acid decomposition in acidic media

Research of thermodynamic and kinetics in preparing U(IV) by reducing and catalyzing U(VI) with hydrazine

Catalytic decomposition of hydrazine in weakly alkaline solutions on platinum nanoparticles

Contact Info

Product

Resources

About