Research on Raman Spectra of Oxalic Acid During Decarboxylation under High Temperature and High Pressure
WANG Hui-yuan, ZHENG Hai-fei*
Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, and School of Earth and Space Science, Peking University, Beijing 100871, China
Abstract:The present research studied the thermal stability of oxalic acid under high temperature and pressure and its in-situ transformation by Raman spectroscopy using a hydrothermal diamond anvil cell. Raman spectra allow the detection of ionic and covalent atomic aggregates through the acquisition of vibrational spectra that are characteristic of their structures and molecular bond types. The result showed that there was no change in characteristic vibrational Raman peaks of oxalic acid in the low-temperature stage. With the increase in temperature and pressure, the characteristic vibrational Raman peaks of oxalic acid became weaker and the peaks disappeared at a certain high temperature, and decarboxylation happened. Oxalic acid decomposes to produce CO2 and H2, according to the reaction: C2H2O4—2CO2+H2. It was found that the decarboxylation was highly related with pressure and that the decarboxylation would be hindered at high pressure. Decarboxylation of oxalic acid under high temperature and pressure showed a linear relationship between temperature and pressure. The data fitting generated the formula: P(MPa)=12.839T(K)-5 953.7,R2=0.99. The molar volume change of decarboxylation of oxalic acid can be described by ΔV(cm-3·mol-1)=16.69-0.002P(MPa)+0.005 2T(K),R2=0.99.
Key words:Raman spectra;High temperature and high pressure;Oxalic acid;Decarboxylation;Molar volume change
王慧媛,郑海飞*. 高温高压下草酸脱羧反应中的拉曼光谱研究[J]. 光谱学与光谱分析, 2012, 32(03): 669-672.
WANG Hui-yuan, ZHENG Hai-fei* . Research on Raman Spectra of Oxalic Acid During Decarboxylation under High Temperature and High Pressure . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2012, 32(03): 669-672.
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