Two Stage Oxidation Of Anthracite In Alkaline Medium And Synthesis Of Terephthalic Acid By Isomerization Of Coal Acids

This work relates to a method of producing terephthalic acid from coal,including oxidation of coal for producing coal acids,which contains a large number of benzene more carboxylic acid(BPCA).In order to investigate the formation of aromatic polycarboxylic acids from coal, YangQuan Anthracite in aqueous alkali was studied.The coal oxidation was performed in 2 L autoclave and the reaction temperature,the alkali/coal,the initial oxygen pressure,reaction time and igitation frequency were changed respectively to study the influence on the yield of coal acids.The optimum reaction conditions are:reaction temperature:270℃;alkali/coal: 2.8:1;the initial oxygen pressure:5.5MPa;reaction time:2h;igitation frequency:70r/min. The highest yield of coal acids under the optimum reaction conditions was about 49.21%(daf to coal),which contains about 56.30%benzene poly carboxylic acids.Two-stage oxidation was adopted to improve the yield of benzene polycarboxylic acids from Yangquan anthracite.Preoxidation is added to alkali-oxygen oxidation,coal is heated by air in a fluid bed reactor.The samples of preoxided coal are analyzed to investigate the relations between structure,nature and the influence on formation of BPCA by means of ultimate analysis,infrared spectra,and analysis of groups.The optimum preoxidation conditions of Yangquan anthracite are obtained:300℃,3h,on the basis of optimum preoxidation conditions,the yield of BPCA to coal is 28.95%(daf),about more than 4.51%of that One-stage method.With addition of 12%acetic acid in the alkali-oxygen oxidation stage of two-stage method,the yield of BPCA to coal is 37.17%(daf to coal),about more than 34.19%of that One-stage method.Terephathalic acid can be obtained in the presence of a catalyst Zn(Bzo)₂ by isomerization of potassium salt of Yangquan coal acids in organic dispersant.Take the Benzoic acid as model compound,It was found the optimum Benzoic acid disproportionation temperature is 400℃, and the highest yield of terephathalic acid is 34.98%;With addition of 7%potassium cyanate in the reaction,the yield of terephathalic acid is 41.84%,more than 19.61%than without cocatalyst,with a purity 95.28%.The optimum isomerization of Yangquan coal acids are:reaction temperature 420℃, amount of catalyst 4%,the yield of TPA is 28.26%;with addition of 10%potassium cyanate in the reaction,the yield of terephathalic acid reached 32.92%.Under the optimum isomeization conditions,take the coal acids which obtained with addition of 12%acetic acid in the alkali-oxygen oxidation stage of two-stage method as reactant,the yield of TPA is 32.76%, and the yield 36.94%could be obtained with addition of 10%cocatalyst in the reaction,more than 12.76%,with a purity 98.43%.Coal acids and terephathalic acid are analyzed by gas chromatography.Comparison of spectrum peak time between products and guide samples is adopted in qualitative analysis,and internal standard method is adopted in quantitative analysis.