Oo Ye Min, Prasit Tanongsak, Thawornprasert Jarernporn, Somnuk Krit
Department of Mechanical and Mechatronics Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand.
Department of Mechanical and Mechatronics Engineering, Energy Technology Research Center, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand.
ACS Omega. 2022 Apr 20;7(17):14666-14677. doi: 10.1021/acsomega.1c07230. eCollection 2022 May 3.
Double-step esterification to produce biodiesel from palm fatty acid distillate (PFAD) was performed by utilizing an ultrasound clamp reactor. Six pairs of ultrasonic clamps were attached to the left and right sides of the stainless-steel tube, and each pair was separated 100 mm apart from each other. Therefore, a total of 12 units of ultrasound clamps distributed 4800 W maximum power (12 × 400 W) throughout the continuous reactor by an ultrasonic generator. To optimize each step of the continuous esterification process for producing methyl ester from PFAD, a response surface methodology was used. The final 93.32 wt % methyl ester purity was attained under a double-step esterification process. For the first step, a 3.75:1 molar ratio of methanol to PFAD (46.4 vol % methanol), 6.6 vol % sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h PFAD flow rate for converting the PFAD to 60.24 wt % methyl ester were recommended. For the second step, the esterification was repeated under a molar ratio of methanol to the first esterified oil of 2.87:1 (61.6 vol % methanol), 5.6 vol % of sulfuric acid, and 400 mm length of ultrasound clamp at 25 L/h esterified oil flow rate. The ultrasonic clamp reactor achieved high yields of esterified oil and the crude biodiesel in a relatively short residence period of 32 s. To determine the product yields of a double-step esterification process, the maximum yields were 103.9 wt % first esterified oil, 107.6% crude biodiesel, and 98 wt % purified biodiesel when calculated on the basis of 100 vol % initial PFAD. The average energy consumed in the production of double-step esterification biodiesel was 0.05796 kWh/L. Therefore, this current approach has a high potential for producing biodiesel with less energy and requires less time to convert the PFAD to a high purity of methyl ester.
利用超声夹式反应器对棕榈脂肪酸馏出物（PFAD）进行两步酯化反应来生产生物柴油。六对超声夹分别安装在不锈钢管的左右两侧，每对超声夹之间相距100毫米。因此，通过超声发生器，总共12个超声夹在整个连续反应器中分布着最大功率为4800瓦（12×400瓦）的功率。为了优化从PFAD生产甲酯的连续酯化过程的每一步，采用了响应面法。在两步酯化过程中，最终获得了93.32重量%的甲酯纯度。第一步，建议甲醇与PFAD的摩尔比为3.75:1（甲醇体积分数为46.4%），硫酸体积分数为6.6%，超声夹长度为400毫米，PFAD流速为25升/小时，以便将PFAD转化为60.24重量%的甲酯。第二步，在甲醇与第一步酯化油的摩尔比为2.87:1（甲醇体积分数为61.6%）、硫酸体积分数为5.6%、超声夹长度为400毫米、酯化油流速为25升/小时的条件下重复酯化反应。超声夹式反应器在相对较短的32秒停留时间内实现了酯化油和粗生物柴油的高产率。为了确定两步酯化过程的产物产率，以100体积%的初始PFAD为基础计算时，最大产率分别为103.9重量%的第一步酯化油、107.6%的粗生物柴油和98重量%的纯化生物柴油。两步酯化生物柴油生产过程中的平均能耗为0.05796千瓦时/升。因此，这种目前的方法在以较少的能量生产生物柴油方面具有很大潜力，并且将PFAD转化为高纯度甲酯所需的时间较少。
