Liquid–liquid synthesis of oximes from carbonyl compounds: formation under neutral conditions and degradation at acidic hydrometallurgical process conditions

Abstract

BACKGROUND In order to elucidate kinetics in the synthesis of oxime liquid–liquid extraction reagents, used as ligands in hydrometallurgical copper production, the oximation reactions of salicylaldehyde and 2′‐hydroxyacetophenone with hydroxylamine were studied in a two‐phase system. Two experimental methods were applied: CSTR reactor under vigorous mixing and batch reactor under normal agitation. The reverse reaction in acidic conditions was also examined, because it results in hydroxyoxime reagent losses in copper liquid–liquid extraction process. RESULTS The overall oximation reaction was of a second‐order, first‐order with respect to each reactant. The estimated activation energy for oximation of salicylaldehyde was 34.2 kJ mol−1, and interfacial reaction rate constant at 40°C 4.81 × 10−3 L mol−1 s−1. The model used, including the empirical description for interfacial reactant concentrations, described the salicylaldehyde oximation reaction well over a wide concentration range. In the batch reactor more than 0.99 conversion for salicylaldehyde was achieved in 15 min at 50°C, but for 2′‐hydroxyacetophenone the maximum reaction conversion was only 0.17 at 70°C in 60 min. Both, aldoxime and ketoxime, were hydrolyzed into their corresponding carbonyl compounds in the presence of 180 g L−1 sulfuric acid. The ketoxime was completely converted into a ketone, but with the aldoxime 80% reagent degradation was observed at equilibrium. CONCLUSION A liquid–liquid system in neutral conditions is applicable for the oximation of aldehydes generated by degradation of hydroxyoxime solvent extraction reagents. For ketones the reaction is much slower. The degradation reaction was shown to be significant in conditions similar to the copper liquid–liquid extraction stripping stage. © 2016 Society of Chemical Industry

A novel and stable hydroxylamine salt generated from betaine hydrochloride and its application in the synthesis of cyclohexanone oxime

“…Hydroxylamine (NH 2 OH) is a versatile chemical, which plays an important role in various applications ranging from degradation of organic pollutants to pharmaceutical production, as well as in large-scale synthesis of cyclohexanone oxime for nylon 6 manufacture. [1][2][3][4][5] However, it contains an N-oxyenamine moiety, which is quite unstable and decomposes even at room temperature due to the low N O ⊞-bond energy at ca 57 kcal mol −1 , meaning that the handling of NH 2 OH as a free base is a challenge. [6][7][8][9] Two well-known catastrophic industrial explosions involving NH 2 OH occurred in Pennsylvania, USA, and in Gunnma, Japan, in 1999 and 2000, respectively.…”

Oxime-modified hierarchical self-assembly polyimide microspheres for high-efficient uranium recovery from wastewater

“…Finally, the carbonyl groups on HSPI were converted into oxime groups to fabricate HSPI-O, which took place in two steps, formation of a carbinolamine intermediate followed by its dehydration. 40 The surface morphologies of HSPI and HSPI-O were investigated by SEM. The HSPI displayed a microsphere structure with a diameter of approximately 25 μm, which was composed of hierarchical nanosheets (Fig.…”

“…34 However, the preparation process is relatively cumbersome by introducing a cyano group and using hydroxylamine hydrochloride to convert it. 35,36 In comparison with the amidoxime group, the oxime group which is also a group with relatively good affinity and selectivity to uranyl ions, 37,38 can be obtained through the conversion of carbonyl groups on the polyimide, [39][40][41] and the process is relatively simple.…”

Modeling the liquid–liquid extraction equilibrium of iron (III) with hydroxyoxime extractant and equilibrium-based simulation of counter-current copper extraction circuits

“…Even though hydroxyoxime extractants have been proven to be very selective towards copper (Szymanowski, 1993;Kabugo et al, 2017), the transfer of iron (III) and other impurities from the pregnant leach solution (PLS) to rich electrolytes (RE) is inevitable (Gotfryd and Pietek, 2013;Molnar and Verbaan, 2003). Most of the iron (III) transfer is due to chemical extraction, while entrainment contributes to a minor extent (Thomas, 2010).…”