以超音波輔助半連續式痲瘋油轉酯化程序產製生質柴油

Abstract

本研究以超音波(ultrasonic irradiation, UI)輔助程序將痲瘋油(jatropha oil, JO)進行兩階段轉酯化程序產製痲瘋生質柴油(jatropha oil biodiesel, JOB)。進行兩階段轉酯化反應之前，將麻瘋原油(raw jatropha oil, JOR)進行油品性質分析，分析項目包含有酸價(AV)、含水率(mW)、動黏度(KV)、密度(ρO)、熱值(H)和冷濾點(CFPP)。本研究在第一階段酯化反應中使用酯化條件為醇油莫耳比(MIPA/JOR) = 5、反應溫度(TE) = 120 ℃、酸觸媒硫酸體積(VH2SO4) = 1.02 mL、連續加入異丙醇和硫酸混合液流速(QE) = 1.5 mL/min、反應時間(tE) = 59.08 min、原料油(JOR) = 200 g。酯化後的油品(JO after esterification, JOE)進行油品性質分析。 在相同酯化條件後進行第二階段轉酯化，醇類分別使用異丙醇或甲醇進行轉酯化後，探討使用異丙醇或甲醇在不同轉酯化反應溫度(TT)、醇油莫耳比(MIPA/JOE 或 MMOH/JOE)和反應時間(tT)對於油品性質和生質柴油轉酯率(YF)，並找出最適之轉酯化反應溫度、醇油莫耳比及反應時間。 使用異丙醇轉酯化中，轉酯化反應後的酸價比酯化後的酸價有些微的上升，增加醇油莫耳比能有效降低油品酸價。當TT = 80 ℃及tT = 180 min，轉酯化反應最適之醇油莫耳比為9，此時的轉酯率為96.06 %，酸價為0.429 mg KOH/g，動黏度為4.01 mm2/s，密度為872.47 kg/m3，熱值為29.88 MJ/kg和冷濾點為-3.5 ℃。當反應溫度在80 ℃時有最佳的酸價(最低)和轉酯率(最高)，其他油品特性亦可以符合CNS 15072的標準規範。反應時間90分鐘有最好的油品性質，當反應時間增加酸價會有些許的上升，轉酯率有些微下降。 在TT = 60 ℃下使用甲醇進行轉酯化反應，最適醇油莫耳比為6，醇油莫耳比增加對降低酸價及增加轉酯率有限。反應時間在10分鐘以上的油品性質相似。反應時間10分鐘已經完成轉酯化反應，此時得到的轉酯率97.08 %，酸價0.097 mg KOH/g，動黏度4.40 mm2/s，密度881.50 kg/m3，熱值38.14 MJ/kg和冷濾點-1 ℃。使用甲醇作為轉酯化醇類比異丙醇反應時間較短，反應溫度較低，所需的醇油莫耳比較少，得到的酸價更低，但是冷濾點較高。 使用甲醇或異丙醇作為酯化反應時的醇類，得到的轉酯率和其他油品特性差異性並不大。轉酯化反應中使用甲醇的最適反應醇油莫耳比較低，反應溫度較低，反應時間也可以縮短，在酯化製程中使用異丙醇作為反應醇類，轉酯化過程中使用甲醇，一方面可以將異丙醇作為廢液回收使用，另一方面也可以達到CNS 15072的標準規範。

In this study, jatropha oil was used in a two-stage transesterification process with assistance of ultrasound irradiation (UI) to manufacture jatropha-oil biodiesel (JOB). The main properties measured inclued, acid value (AV), water content (mW), kinematic viscosity (KV), density (ρO), heating value (H) and cold filter plugging point (CFPP). In the first-stage of esterification, the reaction conditions were set using including molar ratio of isopropanol (IPA) to raw jatropha oil (JOR) (MIPA/JOR) = 5, reaction temperature (TE) = 120 ℃, volume of H2SO4 (VH2SO4) = 1.02 mL, injection flow rate of mixture of IPA and H2SO4 (QE) = 1.5 mL/min, reaction time at constant TE (tE) = 59.08 min and input JOR = 200 g. In order to observe the influence of alcohols on properties and yield (YF) of transesterification, the second-stage of transesterification was constracted by using either IPA or methanol (MOH) in different transesterification reaction temperature (TT), molar ratio of alcohol to product of esterification (JOE) (MIPA / JOE or MMOH / JOE) and reaction time (tT). Finally, the optimal temperature, molar ratio and reaction time of the transesterification reaction could be found. According to experimental result, AV of JOB with IPA is slightly higher than that of JOE. The AV of JOB decreases with increasing MIPA / JOE. At the conditions of TT = 80 ℃ and tT = 180 min with the optimal MIPA / JOE of 9, the yield is 96.06 % with AV = 0.429 mg KOH/g, KV = 4.01 mm2/s, ρO = 872.47 kg/m3, H = 29.88 MJ/kg and CFPP = -3.5 ℃. The best AV (lowest) and yield (highest) are achieved at TT = 80 ℃ with other properties satisfied with CNS 15072 standards. The best reaction time is 90 min. As reaction time further increases, AV rises a little and yield drops slightly. For transesterification with MOH at TT = 60 ℃, MMOH / JOE = 6 is the optimal condition. There is no evident impact on increasing yield and reducing AV by increasing MMOH/JOE. The oils made by transesterification with reaction times longer than 10 min are similar. At the conditions of TT = 60 ℃, MMOH / JOE = 6 and tT = 10 min, the biodiesel YF is 97.08 % with AV = 0.097 mg KOH/g, KV = 4.40 mm2/s, ρO = 881.50 kg/m3, H = 38.14 MJ/kg and CFPP = -1 ℃. Compared with IPA, the use of MOH needs shorten tT, lower TT and less MMOH / JOE. It produces JOB with lower AV, but higher CFPP. The properties and YF by using MOH or IPA as alcohol for esterification are similar. Because IPA can come from the waste stream, one may thus use IPA in the first-stage esterification, while MOH employ in the second-stage transesterification. This not only achieves waste recycling but also satisfies with CNS 15072 standard.