EFFECT OF pH CHANGE ON THE STABILITY OF HETEROMETALIC COMPLEX COMPOUNDS OF NICKEL (II)–COBALT (III) WITH MONOETHANOLAMINE IN ALCOHOL SOLUTIONS
DOI:
https://doi.org/10.20535/kpi-sn.2019.3.175733Keywords:
Monoethanolamine, Cobalt (III), Nickel (II), Potentiometric titration, Electronic absorption spectraAbstract
Background. The application of the cobalt (III) nickel (II) heterometalic complex with monoethanolamine, which is used as a precursor for the preparation of electrocatalytic materials on inert carriers, remain insufficiently studied. Of particular importance is the control of the pH range of the reaction medium, which can significantly affect the composition and structure of the active centers after deposition and pyrolytic decomposition.
Objective. The purpose of the paper is the experimental determination of the pH range in which the composition of 2Co–Ni complex compounds with monoethanolamine will remain unchanged and study of the transformations that occur with complex compounds depending on the change in pH value.
Methods. Synthesis of {Ni[CoEtm3]2}(NO3)2 and studies of its durability by methods of potentiometric titration with chloride acid (C = 0.1 M) and sodium hydroxide (C = 0.1 M). Studying the structural transformations of the obtained complex compound and its decomposition products in alcohol solutions using electronic absorption spectra.
Results. The study of the stability of alcoholic solutions of the intracomplex cobalt (III) compound with monoethanolamine and the heterometallic compound 2Co–Ni with monoethanolamine in alkaline and acidic media made it possible to establish the limits of the pH range in which the synthesis of the synthesized complex compounds does not occur. For the results of the analysis of the obtained absorption spectra and redox titration, it can be argued that there is no change in the coordination environment of metals (Co (III), Ni (II)) in the range of 7 to 8 pH. With an increase in the pH of the medium above 8, the complex compounds are destroyed with the formation of Co2+ and Ni2+ salts. In the case of lowering the pH below 7, the above complex compounds are converted to chloroacidic amines. The corresponding transformations that occur with CoEtm3 and {Ni[CoEtm3]2}(NO3)2 under the influence of acid and alkali in alcohol solutions are described by the proposed decomposition schemes.
Conclusions. The obtained results indicate the need to control the pH of the reaction medium with the promising development of technology for producing catalytic materials using the {Ni[CoEtm3]2}(NO3)2 heteronuclear complex as precursors and clearly set the pH limits in the range from 7 to 8 units.
References
Z. Wang et al., “High-performance catalytic perovskite hollow fiber membrane reactor for oxidative propane dehydrogenation”, J. Membrane Sci., no. 578, pp. 36–42, 2019. doi: 10.1016/j.memsci.2019.02.012
S. Badoga et al., “Combined effects of EDTA and heteroatoms (Ti, Zr, and Al) on catalytic activity of SBA-15 supported NiMo catalyst for hydrotreating of heavy gas oil”, Ind. Eng. Chem. Res., vol. 53, no. 6, pp. 2137−2156, 2014. doi: 10.1021/ie400695m
J. Santander et al., “Ni–Nb mixed oxides: One-pot synthesis and catalytic activity for oxidative dehydrogenation of ethane”, Chem. Eng. J., vol. 255, pp. 185–194, 2014. doi: 10.1016/j.cej.2014.06.048
Z. Li et al., “Fine-tuning the activity of metal-organic framework-supported Cobalt Catalysts for the oxidative dehydrogenation of propane”, J. Am. Chem. Soc., vol. 139, no. 42, pp. 15251–15258, 2017. doi: 10.1021/jacs.7b09365
A.A. Andriiko et al., Discharge-ionization of hydrogen on modified carbon nanotube electrodes”, Int. J. Hydrogen Energy, vol. 38, no. 14, pp. 5983–5988. 2013. doi: 10.1016/j.ijhydene.2013.02.088
А.О. Zulfigarov et al., “Syntesis route for preparation of precursor solutions”, in Promising Materials and Processes in Applied Electrochemistry. Kyiv, Ukraine, 2017, рр. 235–240.
А.О. Zulfigarov et al., “Structure and thermal destruction trinuclear complexes 2Co(+3):Ni(+2) with aminoalcohols”, Ukrainian Chemistry Journal, vol. 82, no. 7, pp. 46–53, 2016.
I.V. Pyatnickui, Cobalt Analytical Chemistry. Мoscow. SU: Nauka, 1965.
Downloads
Published
Issue
Section
License
Copyright (c) 2019 The Author(s)
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under CC BY 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work
