基于紫外吸光度的生物柴油氧化降解程度分析

doi:10.16085/j.issn.1000-6613.2019-0659

摘要/Abstract

摘要：

为快速检测出生物柴油的氧化降解程度，利用小桐子生物柴油在氧化过程中共轭二烯以及共轭三烯的变化致使230nm处吸光度随氧化时间延长逐渐增强、270nm处吸光度逐渐减弱的现象，建立了生物柴油酸值与紫外吸光度的线性、指数、对数和乘幂这4种模型。留一法交叉验证显示线型模型的预测均方根误差最小，预测值与实测值的相关性最高。利用最小二乘法建立酸值与吸光度线性方程，并对模型进行了验证。结果表明：该拟合方程的拟合优度R²为0.987，表明该预测模型的拟合效果较好；模型验证中实测值与预测值的拟合优度R²为0.980；样本的最大相对误差为5.27%，该模型具有较高的准确度与精确度，可以用该方法代替滴定法快速准确地预测出酸值来表征氧化降解程度。

关键词: 生物柴油, 紫外吸收光谱, 酸值预测, 共轭结构, 氧化降解

Abstract:

The change of conjugated diene and conjugated triene in the oxidation process of Jatropha biodiesel resulted in the increase of absorbance at 230nm and the decrease of absorbance at 270nm with increasing oxidation time. Four models of linearity, exponential, logarithm and power of biodiesel acid value and the UV absorbance were established in order to quickly detect the degree of oxidative degradation of biodiesel. The leave-one-out cross-validation showed that the predicted root mean square error of the linear model was the smallest, and the correlation between the predicted value and the measured value was the highest. The linear equations of acid value and absorbance were established by least squares method and the model was verified. The results showed that the fitting goodness R² of the fitting equation was 0.987, which indicated that the fitting model had better fitting effect; the goodness of fit between the measured value and the predicted value in the model verification was 0.980; the maximum relative error of the sample was 5.27%, and the model had high accuracy and precision. This method can be used instead of titration to quickly and accurately predict the acid value to characterize the degree of oxidative degradation.

Key words: biodiesel, ultraviolet absorption spectrum, acid value prediction, conjugated structure, oxidative degradation

中图分类号:

TQ645

王霜,王友昊,李法社,王文超,隋猛. 基于紫外吸光度的生物柴油氧化降解程度分析[J]. 化工进展, 2020, 39(2): 506-512.

Shuang WANG,Youhao WANG,Fashe LI,Wenchao WANG,Meng SUI. Analysis of oxidative degradation degree of biodiesel based on UV absorbance[J]. Chemical Industry and Engineering Progress, 2020, 39(2): 506-512.

图/表 11

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名称	质量分数/%
棕榈酸甲酯C16∶0	12.96
硬脂酸甲酯C18∶0	7.66
油酸甲酯C18∶1	41.89
亚油酸甲酯C18∶2	34.45
亚麻酸甲酯C18∶3	0.56

名称	质量分数/%
棕榈酸甲酯C16∶0	12.96
硬脂酸甲酯C18∶0	7.66
油酸甲酯C18∶1	41.89
亚油酸甲酯C18∶2	34.45
亚麻酸甲酯C18∶3	0.56

氧化时间/h	230nm吸光度	实测酸值/mg·g^-1	线性拟合值 y=ax+b	指数拟合值 y=ae^bx	对数拟合值 y=alnx+b	乘幂拟合值 y=ax^b
2	1.213	2.6732	2.5815	2.7130	2.2229	2.4668
4	1.425	2.7760	2.7938	2.8523	2.6922	2.7685
6	1.543	2.8771	2.8993	2.9242	2.8802	2.9012
8	1.662	2.9574	3.0091	3.0042	3.0519	3.0316
10	1.942	3.0894	3.2726	3.2109	3.4103	3.3273
12	1.835	3.2888	3.1387	3.0973	3.2481	3.1842
18	2.28	3.4714	3.5645	3.4527	3.7598	3.6368
24	2.334	3.7102	3.5863	3.4692	3.7806	3.6533
48	4.257	5.3272	5.2585	6.1263	4.4456	4.7387

氧化时间/h	230nm吸光度	实测酸值/mg·g^-1	线性拟合值 y=ax+b	指数拟合值 y=ae^bx	对数拟合值 y=alnx+b	乘幂拟合值 y=ax^b
2	1.213	2.6732	2.5815	2.7130	2.2229	2.4668
4	1.425	2.7760	2.7938	2.8523	2.6922	2.7685
6	1.543	2.8771	2.8993	2.9242	2.8802	2.9012
8	1.662	2.9574	3.0091	3.0042	3.0519	3.0316
10	1.942	3.0894	3.2726	3.2109	3.4103	3.3273
12	1.835	3.2888	3.1387	3.0973	3.2481	3.1842
18	2.28	3.4714	3.5645	3.4527	3.7598	3.6368
24	2.334	3.7102	3.5863	3.4692	3.7806	3.6533
48	4.257	5.3272	5.2585	6.1263	4.4456	4.7387

氧化时间/h	270nm吸光度	实测酸值/mg·g^-1	线性拟合值 y=ax+b	指数拟合值 y=ae^bx	对数拟合值 y=alnx+b	乘幂拟合值 y=ax^b
2	3.382	2.6732	2.6577	2.7640	2.7385	2.8238
4	3.331	2.7760	2.7678	2.8333	2.8208	2.8748
6	3.294	2.8771	2.8423	2.8816	2.8773	2.9104
8	3.235	2.9574	2.9757	2.9783	2.9845	2.9873
10	3.122	3.0894	3.2293	3.1752	3.1968	3.1497
12	3.136	3.2888	3.1696	3.1221	3.1412	3.1004
18	2.964	3.4714	3.5593	3.4484	3.4828	3.3807
24	2.913	3.7102	3.6495	3.5255	3.5631	3.4474
48	2.132	5.3272	5.2584	6.1091	5.6804	6.9777