Reduction of Pu(IV) and Np(VI) with hydroxylamine in solutions of low acidity with high uranium content

et al. 2021

J. Phys. Chem. A

Effectively adjusting and controlling the valence state of neptunium from the spent fuel reprocessing process is essential to separating neptunium. Hydrazine and its derivatives as free-salt reductants have been experimentally demonstrated to effectively reduce Np(VI) to Np(V). We have theoretically investigated the reduction mechanisms of Np(VI) with hydrazine and three derivatives (HOC2H4N2H3, CH3N2H3, and CHON2H3) in previous works. Herein, we further explored the reduction reaction of Np(VI) with phenylhydrazine (C6H5N2H3) including the free radical ion mechanism and the free radical mechanism. Potential energy profiles (PEPs) indicate that the rate-determining step of both mechanisms is the first stage. Moreover, for the free radical ion mechanism, phenylhydrazine possesses better reduction ability to Np(VI) compared to HOC2H4N2H3, CH3N2H3, and CHON2H3, which falls completely in line with the experimental results. Additionally, the analyses of the quantum theory of atoms in molecules (QTAIM), natural bond orbitals (NBOs), electron localization function (ELF), and localized molecular orbitals (LMOs) have been put forward to elucidate the bonding evolution for the structures of the reaction pathways. This work offers insights into the reduction mechanism of Np(VI) with phenylhydrazine from the theory point of view and contributes to design more high-efficiency reductants for the separation of U/Np and Np/Pu in spent fuel reprocessing.

Section: Introductionmentioning

confidence: 99%

Theoretical Insights into the Reduction Mechanism of Np(VI) with Phenylhydrazine

et al. 2021

J. Phys. Chem. A

“…Therefore, how to adjust and control the valence state of Np in the PUREX process is an important issue. So far, there are some investigations on the Np(VI) reduction with salt-free reductants such as hydroxylamine, − aldehydes, , oximes, , urea, − hydrazine, − and their derivatives. Zhang et al reported that N , N -diethylhydroxylamine (DEHAN) can reduce Np(VI) to Np(V), which is very beneficial for the separation of Np from U and Pu .…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al reported that N , N -diethylhydroxylamine (DEHAN) can reduce Np(VI) to Np(V), which is very beneficial for the separation of Np from U and Pu . Np(VI) can be reduced with hydroxylamine in low acidity with high uranium content . Moreover, the reaction kinetics of Np(VI) and butyral species have been studied in the nitric acid solution, which showed that n -butyraldehyde and isobutyraldehyde are able to reduce Np(VI) rather than U(VI) and Pu(IV) .…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study on the Reduction Mechanism of Np(VI) by Hydrazine Derivatives

et al. 2020

J. Phys. Chem. A

The key to effective separation of neptunium from the spent fuel reprocessing process is to adjust and control its valence state. Hydrazine and its derivatives have been experimentally confirmed to be effective salt-free reductants for reducing Np(VI) to Np(V). We theoretically studied the reduction reactions of Np(VI) with three hydrazine derivatives (2hydroxyethyl hydrazine (HOC 2 H 4 N 2 H 3 ), methyl hydrazine (CH 3 N 2 H 3 ), and formyl hydrazide (CHON 2 H 3 )) and obtained the free radical ion mechanism and the free radical mechanism. Their potential energy profiles (PEPs) suggest that the free radical mechanism is the most probable reaction. Based on the energy barrier of the free radical ion mechanism, the trend of the reduction ability of the three hydrazine derivatives is HOC 2 H 4 N 2 H 3 > CH 3 N 2 H 3 > CHON 2 H 3 , which is in excellent agreement with the experimental results. Lastly, the analyses of natural bond orbitals (NBOs), quantum theory of atoms-in-molecules (QTAIM), and electron localization function (ELF) have been carried out to explore the bonding evolution of the structures along the reaction pathways. This work provides an insight into the reduction mechanism of Np(VI) with hydrazine derivatives from the theoretical perspective and helps to design more effective reductants for the separation of U/Np and Np/Pu in spent fuel reprocessing.

“…It has aroused extensive attention in virtue of their applications such as pharmaceutical, [1] pesticide, [2] rubber, [3] dye, [4] military [5] and nuclear industries. [6] Nowadays much effort has been devoted to preparing NH 2 OH. The common way is neutralization method.…”

Section: Introductionmentioning

confidence: 99%

Application of an immobilized ionic liquid for the preparation of hydroxylamine via hydrolysis of cyclohexanone oxime

Zeitschrift anorg allge chemie

Liu

Cheng

et al. 2021

Preparation of hydroxylamine via hydrolysis of cyclohexanone oxime was studied over porous SiO 2 supported acid ionic liquid catalyst. The catalyst [SPIPTES]CF 3 SO 3 @SiO 2 was prepared through sol-gel method and characterized by elemental analysis, IR and TG, etc. Various parameters such as reaction temperature and time, catalyst amount were investigated systematically. The optimized reaction conditions investigated were catalyst:cyclohexanone oxime (mass ratio) 4 : 1, conducted at 60°C for 1 h. Since the present hydrolysis reaction is controlled by thermodynamics, the conversion of cyclohexanone oxime could not be very high. However, reasonable result was achieved under the optimized reaction conditions. Cyclohexanone oxime conversion was 38.41 % and NH 2 OH yield was 37.65 %. Additionally, combining experiments with density functional theory calculations, a possible catalyst structure and reaction pathway involved protonated cyclohexanone oxime mechanism was proposed for the present hydrolysis in this study.