Optimization of microwave-assisted synthesis of medium-chain triacylglycerols using response surface methodology

doi:10.11949/j.issn.0438-1157.20161354

Abstract

Abstract:

As a new functional oil, the medium-chain triacylglycerols (MCTs) hold promising applications in diverse areas such as food, cosmetics and other fields.Several methods have been developed for the synthesis of MCTs, including traditional chemical processes and lipase-catalyzed, both them have great drawbacks such as the long reaction time.As a new alternative method, microwave irradiation on the esterification of caprylic/capric acids with glycerol was investigated in this study.Subsequently, Fourier-transform infrared spectrometry (FTIR) and gas chromatography mass spectrometry (GC/MS) were used to determine the structure and compositions of the liquid products, respectively.Compared to the conventional heating method, microwave assisted synthesis of MCTs shortened the reaction time greatly when achieving the same conversion.Response surface methodology (RSM) with a 3-level-3-factor central composite design (CCD) was applied to model and optimize the reaction conditions and, a quadratic model was developed as consequence, in order to correlate the preparation variable to the response.The optimum conditions for the synthesis of MCTs were as follows:reaction temperature of 190℃, substrate mole ratio (fatty acid:glycerol) of 3.33:1 and PTSA loading of 4.30%(mass).Under these conditions, the actual hydroxyl value 1.12 mg KOH·g^-1 was obtained, which is comparably well with the minimum predicted value of 1.03 mg KOH·g^-1, corresponding to the conversion yield was 99.7%.

Key words: MCTs, microwave, response surface methodology, FTIR, GS/MS

摘要：

以对甲苯磺酸为催化剂，在微波环境下合成辛酸癸酸甘油三酯，并利用响应面法优化辛酸癸酸甘油三酯的合成过程条件。首先，通过单因素灵敏度分析法对催化剂的选择、酸/醇摩尔比、反应温度、微波功率、催化剂用量、反应时间6个因素进行实验考察，确定了酸/醇摩尔比、反应温度、催化剂用量3个关键因素的优化值及取值范围。采用中心组合设计原则对3个关键因素进行实验设计。以产品羟值为响应值，基于响应实验结果，利用响应面法对实验结果进行了方程回归，得到3个关键因素与响应值的二次关联模型。通过方差分析和平行实验，证明该模型准确可用。确定了中碳链甘油三酯（MCTs）最佳合成条件为：酸/醇摩尔比为3.33：1，反应温度为190℃，催化剂用量为甘油质量的4.30%，微波功率为500 W，反应时间为3 h，得到产品羟值为1.12 mg KOH·g^-1，酯化率高达99.7%，与理论预测值基本相符。与传统加热方式对比，微波辅助合成MCT大大缩短了反应时间。测定了精制提纯后MCT产品的各项物化性能指标，均已达到企业标准。通过红外光谱表征和GC/MS进一步表征产物结构和混合物油脂的组成，甘油三酯得率达到95.7%。

关键词: 中碳链甘油三酯, 微波, 响应面法, 红外光谱, 气质联用

CLC Number:

TQ645.8

LING Hui, ZHENG Cheng, MAO Taoyan, WEI Yuan, LIU Ying. Optimization of microwave-assisted synthesis of medium-chain triacylglycerols using response surface methodology[J]. CIESC Journal, 2016, 67(S2): 231-244.

凌慧, 郑成, 毛桃嫣, 魏渊, 刘颖. 响应面法优化微波辅助合成中碳链甘油三酯工艺[J]. 化工学报, 2016, 67(S2): 231-244.

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