ZnC2O4의 Oxalate로의 효과적 분리 및 이의 전기화학적 환원을 통한 글리콜산으로의 전환 = Facile Separation of Zinc Oxalate to Oxalate and its Conversion to Glycolic Acid via Electrochemical Reduction

다국어 초록 (Multilingual Abstract)

Oxalic acid has been traditionally obtained via the oxidation of carbohydrates using nitric acid and catalysts. However, this process produces a variety of nitrogen oxides during oxidation and requires a separation process due to its various intermediates. These products and additional steps increase the harmfulness and complexity of the process. Recently, the electrochemical reduction of carbon dioxide into oxalic acid has been suggested as an environmentally friendly and efficient technology for the production of oxalic acid. In this electrochemical conversion system, zinc oxalate (ZnC2O4) is obtained by the reaction of Zn2+ ions produced by Zn oxidation and oxalate ions produced by CO2 reduction. ZnC2O4 can then be converted to form oxalic acid, but this requires the use of a strong acid and heat. In this study, a system was proposed that can easily convert ZnC2O4 to oxalic acid without the use of a strong acid while also allowing for easy separation. In addition, this proposed system can also further convert the products into glycolic acid which is a high-value-added chemical. ZnC2O4 was effectively separated into Zn(OH)2 powder and oxalate solution through a chemical treatment and a vacuum filtration process. Then the Zn(OH)2 and oxalate were electrochemically converted to zinc and glycolic acid, respectively.

국문 초록 (Abstract)

옥살산(oxalic acid)은 기존에 질산을 사용한 carbohydrates의 산화 공정에 의해 얻어질 수 있으며 여러 분야에서 사용되고 있다. 하지만 이 반응은 다양한 질소 산화물을 형성하고 많은 증간 생산물의 분리를 필요로 하기에 복잡하고 환경에 유해하다. 한편, 이산화탄소로부터 전기화학적 방법에 의해 옥살산을 높은 효율로 얻을 수 있는 방법이 제안되었다. 아연 전극 산화에 의해 생성된 Zn2+이온과 CO2 환원에 의한 oxalate이온의 반응으로 zinc oxalate(ZnC2O4)가 얻어진다. 이후 산처리에 의해 옥살산이 생성될 수 있으나 강산과 열을 필요로 한다. 본 연구에서는 CO2의 전기화학적 전환으로 형성된 ZnC2O4을 강산을 사용하지 않고, 간단하고 분리가 쉬운 방법을 적용하여 옥살산으로 전환하고자 한다. 또한, 고부가 물질인 글리콜산으로 더 전환시킴으로써 이산화탄소에 서 고부가 물질로의 전환 가치를 높이고자 하였다. ZnC2O4를 상온, 상압에서 화학적 방법 및 여과 과정을 통해 효과적으로 Zn(OH)2 입자와 oxalate 용액으로 분리하였으며 얻어진 Zn(OH)2와 oxalate는 전기화학적 방법을 사용하여 각각 Zn, 글리콜산으로 전환되었다

참고문헌 (Reference)

1 Luca, F. D., "g-C3N4 decorated TiO2 nanotube ordered thin films as cathodic electrodes for the selective reduction of oxalic acid" 84 : 25-30, 2021

2 Lee, Y., "Ultrathin multilayer Sb-SnO2/IrTaOx/TiO2nanotube arrays as anodes for the selective oxidation of chloride ions" 840 : 155622-, 2020

3 Schuler, E., "Towards sustainable oxalic acid from CO2 and biomass" 14 : 3636-3664, 2021

4 Fischer, J., "The production of oxalic acid from CO2 and H2O" 11 : 743-750, 1981

5 Valderrama, M. A. M., "The potential of oxalic - and glycolic acid based polyesters (review). Towards CO2 as a feedstock (Carbon Capture and Utilization - CCU)" 119 : 445-468, 2019

6 Khalil, S. A., "The kinetics of zinc dissolution in nitric acid" 118 : 453-462, 1987

7 Krężel, A., "The biological inorganic chemistry of zinc ions" 611 : 3-19, 2016

8 Dawass, N., "Solubilities and transport properties of CO2, oxalic acid, and formic acid in mixed solvents composed of deep eutectic solvents, methanol, and propylene carbonate" 126 (126): 3572-3584, 2022

9 Beverskog, B., "Revised purbaix diagram for zinc at 25-300°C" 39 : 107-114, 1997

10 Costa, R. S., "Production of oxalic acid by electrochemical reduction of CO2 using silver-carbon material from babassu coconut mesocarp" 147 : 109678-, 2020

11 Lee, W. H., "Photocatalytic reduction of aqueous mercury(II) using hybrid WO3-TiO2nanotubes film" 13 : 1-9, 2017

12 Eggins, B. R., "Improved yields of oxalate, glyoxylate and glycolate from the electrochemical reduction of carbon dioxide in methanol" 27 : 706-712, 1997

13 Im, S., "Facilitated series electrochemical hydrogenation of oxalic acid to glycolic acid using TiO2nanotubes" 135 : 107204-, 2022

14 Yan, H., "Engineering Pt-Mn2O3 interface to boost selective oxidation of ethylene glycol to glycolic acid" 284 : 119803-, 2021

15 Boor, V., "Electrochemical reduction of CO2 to oxalic acid: experiments, process modeling, and economics" 61 : 14837-14846, 2022

16 Sadakiyo, M., "Electrochemical hydrogenation of nonaromatic carboxylic acid derivatives as a sustainable synthesis process: from catalyst design to device construction" 21 : 5882-5889, 2019

17 Abramo, F. P., "Electrocatalytic production of glycolic acid via oxalic acid reduction on titania debris supported on a TiO2 nanotube array" 68 : 669-678, 2022

18 Ruiz-Lopez, E., "Electrocatalytic CO2 conversion to C2 products: Catalysts design, market perspectives and techno-economic aspects" 161 : 112329-, 2022

19 Niu, D., "Effects of organic solvents in anodization electrolytes on the morphology and tube-to-tube spacing of TiO2 nanotubes" 735 : 136776-, 2019

20 Fang, D., "Effect of heat treatment on morphology, crystalline structure and photocatalysis properties of TiO2 nanotubes on Ti substrate and freestanding membrane" 257 : 6451-6461, 2011

21 Xie, H., "Cu-based nanocatalysts for electrochemical reduction of CO2" 21 : 41-54, 2018

22 Centi, G., "Chemical engineering role in the use of renewable energy and alternative carbon sources in chemical production" 1 : 5-, 2019

23 Zhang, Z., "Catalytic oxidation of carbohydrates into organic acids and furan chemicals" 47 : 1351-1390, 2018

24 Perathoner, S., "Catalysi ws for solar-driven chemistry: The role of electrocatalysis" 330 : 157-170, 2019

25 Yang, Y., "Aromatic ester-functionalized ionic liquid for highly efficient CO2 electrochemical reduction to oxalic acid" 13 : 4900-4905, 2020

26 Zhang, Z., "Analysis of glyoxal and related substances by means of high-performance liquid chromatography with refractive index detection" 51 : 893-898, 2012

27 Indira, K., "A review on TiO2 nanotubes: Influence of anodization parameters, formation mechanism, properties, corrosion behavior, and biomedical applications" 1 : 28-, 2015