超临界水中氨基乙酸的气化产氢特性

Glycine gasification in supercritical water for hydrogen production

鉴于湿生物质如食品加工工业残余物和城市污泥中含有大量蛋白质的情况,以氨基乙酸作为蛋白质的模型化合物进行超临界水气化实验,研究了反应温度和反应时间耦合条件下Na2CO3的催化特性以及氨基乙酸气化产物特性。结果表明:添加Na2CO3会增大氨基乙酸的气化效率、氢气的体积分数和产率以及反应后液体化学需氧量(COD)的去除率,且添加质量分数为0.1%时的催化效果优于0.2%;Na2CO3主要是对H2产率产生影响,其催化机理与已有碱性化合物的催化机理不同,可能是通过促进氨基乙酸的水解产物(甲酸)的脱羧反应来提高H2的产率;氨基乙酸气化效率可达99.4%,生成物包括H2、CO2、N2、CH4和C2～C3气体,其中H2的体积分数可超过50%,产率可达1.8L.g-1,且超过一半的份额来源于水,反应后液体清澈透明,COD和pH值指标均可以达到《生活杂用水水质标准》,可以进行回收利用。

Because wet biomass such as residues from food industry or sewage sludge usually contains plenty of protein, the experiments of glycine gasification in supercritical water were conducted, in which glycine was used as the model compound of protein. The catalytic mechanism of sodium carbonate, product characteristics of glycine gasification were investigated with coupled relation between reaction temperature and reaction time. The results showed that sodium carbonate could increase gasification efficiency of glycine, the yield and volume fraction of hydrogen, and the removal efficiency of chemical oxygen demand （COD） of liquid products. The catalytic effect of addition amount of 0.1% mass concentration was better than that of 0.2%. And the effect of sodium carbonate on hydrogen yield was greater than that on volume fraction. The catalytic mechanism of sodium carbonate for glycine gasification was different from that of alkali compounds which has been reported before. Sodium carbonate increased the hydrogen yield probably by accelerating the decarboxylation reaction of formic acid, which was a glycine hydrolysate. Glycine could almost be gasified completely. The gas products include H2, CO2, N2, CH4, C2--C3, in which hydrogen volume fraction could be higher than 50%, hydrogen yield could be up to 1.8 L· g^-1, and more than half of hydrogen came from water. The liquid after reaction could be reused not only because it was clear and transparent but also because both the COD and pH values were met the quality standard of domestic water for miscellaneous use.