Reaction Kinetics Of Sodium Oxalate From Sodium Formate By Dehydrogenation

Oxalic acid, also known as ethanedioic acid, and its compounds havewidespread industrial applications in several fields .There are four methods forthe production of oxalic acid and the process depends upon the raw materialselected. The main method used in our country is thermal decomposition ofsodium formate. The most important step in the synthesis technology is thedehydrogenation process. Many studies before were mainly focused on staticdescriptions of the overall thermal decomposition behavior. However, thekinetics of the dehydrogenation has not yet been studied in detail because ofthe complexity of this decomposition process. A kinetic interpretation isalways required for an understanding of the process of solid-state reactions.Therefore, the main aim of this work is to get the information about thereaction and determine the kinetic parameters of calcinations process ofsodium formate.In this paper, the thermal characteristics of sodium oxalate and sodiumformate were investigated by in-situ thermal analysis technique at differentheating rates in different atmosphere. The influences of heating rate,atmosphere and NaOH on the process of the thermal decomposition were systemly studied, and the kinetic parameters of the main reaction and the sidereaction of the dehydrogenation of sodium formate were obtained for the firsttime.The experimental results showed that the calcinations process of sodiumformate can be divided into two distinguished steps from room temperature to600℃. The main reaction overlapped with the side reaction occurred in thefirst step and sodium oxalate and sodium carbonate are formedcoinstantaneously. The second step, which appears at higher temperature area,is mainly the thermal decomposition process of sodium oxalate, and the finalsubstance is sodium carbonate.Both heating rates and carrier gas affect the thermal analysis curves greatly,while NaOH have minor effects on the thermal decomposition process. TGand DTG curves all moved to higher temperature ranges with increasingheating rate. Inert atmosphere appeared to avail the main reaction; in theopposite, oxidative atmosphere appeared to avail the by reactions.The side reaction information was separated from the main reaction bybringing down the heating rate in oxygen atmosphere, and the thermal analysiskinetic triplets of the side reaction were obtained finally .Ea=(164.38±5.23)KJ.mol, G(a)=^{-ln(1-α)52}, ln(A)=24.57±0.21.The original data was revised according to the information about the sidereaction, and the thermal analysis kinetic triplets for the main reaction werealso obtained by Freeman-Carroll method and Anderson-Freeman method separately. For Freeman-Carroll method :Ea=84.45kJ/mol; reaction ordern=0.65. ln(A)=24.65; for Anderson-Freeman method: Ea=87.04kJ/mol; n=0.64; ln(A)=24.76。...