應用微波及傳統加熱輔助機械攪拌程序 產製桐油基底生質柴油之研究

Abstract

本研究首先探討以桐油產製生質柴油，其次再摻配桐油、棕櫚油及芥花油依重量百分比20、30及50%混合而得之綜合油，以改進桐油生質柴油之不合格項目並增加合乎標準之生質柴油之產量。桐油與綜合油兩者合稱為桐油基底油。本研究就微波、傳統加熱板之熱鹼催化轉酯化以及常溫鹼催化轉酯化等三種程序，由其產率、油品品質及能耗探討不同油品之最適轉酯化生產程序。本研究並探討沉降時間與油品轉酯率之關聯性。 本研究結果顯示桐油基底油在相同攪拌時間下，微波熱鹼催化轉酯化程序之轉酯率較穩定並大於其他兩種程序。傳統加熱板做為加熱器時，熱能利用效率不良無法有效提升轉酯化。微波系統並較加熱板節約了75.72-85.27% 之能量，顯示出微波裝置在轉酯率、加熱效率及能源利用效率皆優於傳統加熱板。純化程序中的沉降時間(tS)是使粗脂肪酸甲基酯以及粗甘油分離不可缺少之步驟。增加沉降時間將有助於使轉酯化反應更趨近完全。本實驗所用原料油品為未精煉之桐油，在相同反應條件下，其轉酯率低於棕櫚油、芥花油以及以綜合油。故桐油中不純物中可能干擾鹼催化轉酯化反應。 於轉酯化條件為微波加熱功率900 W，加熱兼攪拌時間(tHCS) 60 s，tS為1440 min時，桐油生質柴油之密度(ρB)、動黏滯度(KV)、酸價(AV)、碘價(IV)、冷濾點(CFPP)以及酯含量分別為897 kg m-3、8.34 mm2 s-1、0.12 mg KOH、164 g I2 100 g-1、-16 oC及86.7 wt.%；綜合油產製之生質柴油則為885 kg m-3、4.91 mm2 s-1、0.11 mg KOH、120.86 g I2 100 g-1、-5 oC及97.8 wt.%。可見預摻配油品可改良桐油生質柴油之品質。但綜合油生質柴油在碘價方面仍小幅超標，故另外調配綜合油二號(桐油、棕櫚油及芥花油依重量百分比10、30及60%)，所產製生質柴油其ρB =883 kg m-3、KV = 4.67 mm2 s-1、AV = 0.13 mg KOH、IV =118.90 g I2 100 g-1、CFPP = -3.5 oC以及酯含量為96.1 wt.%，其IV 已合乎標準。

Because fossil energy is non-renewable and environmental impacts of its use are serious, the biodiesel produced using non-food stuff materials is regarded as a renewable and green energy. In this study, the transesterification reactions of Tung-oil, palm oil, canola oil and blended oil were examined. Three transesterification processes were assessed, namely, 1) alkaline-catalyzed transesterifications without and 2) with heating via microwave or 3) traditional heating plate (HP). The pre-mixed blended oil consists of Tung-oil (20 wt.%), palm oil (30 wt.%) and canola oil (50 wt.%). The transesterification yield (YF) of fatty acid methyl ester (FAME) via the combined microwave and stirring process is higher than those via the other two processes at the same other conditions. The low energy efficiency of heating via HP process barely improves the transesterification reaction. Moreover, the microwave process saves about 75.72-85.27% energy as compared to HP process. The YF of Tung-oil that is an unrefined oil from Tung tree seed, is smaller than those of other oils. The non-oil substances in Tung-oil may interfere with the transesterification reaction. The biodiesel of blended oil (BME) exhibits lower density (ρB), kinematic viscosity (KV) and iodine value (IV) of biodiesel than the Tung-oil (TME). The corresponding values ofρB, KV, AV, IV, cold filter plug point (CFPP) and ester content of BME are 885 kg m-3, 4.91 mm2 s-1, 0.11 mg KOH, 120.86 g I2 100 g-1, -5 oC and 97.8 wt.%, respectively, and those of TME are 897 kg m-3, 8.34 mm2 s-1, 0.12 mg KOH, 164 g I2 100 g-1, -16 oC and 86.7 wt.% respectively. In comparison with the biodiesel standards of Taiwan and Europe with ρB = 800-900 kg m-3, KV = 3-5 mm2 s-1, IV = 120 max. g I2 100 g-1 and ester content = 96.5 wt.%, BME is better than TME. The unsatisfied IV of 120.86 g I2 100 g-1 of BME can be satisfied reducing the content of Tung-oil in blended oil, for example, with 10 wt.% of Tung-oil, 30 wt.% of palm oil and 60 wt.% of canola oil, yielding the modified BME noted as BME2. The BME2 gives ρB = 883 kg m-3, KV = 4.67 mm2 s-1 and IV = 118.90 g I2 100 g-1.