磁性固體觸媒之合成及其應用於生質柴油製造

Synthesis of Magnetic Solid Catalysts and Their Application for Biodiesel Manufacturing

蔡民鎰(Min-Yi Tsai)

指導教授 ： 張慶源

國立臺灣大學/工學院/環境工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201602580

摘要

為避免氣候變遷的衝擊，全球有必要轉型為低碳能源體系，因此再生能源的推廣應用為未來趨勢。本研究利用磁性固態鹼觸媒(CA/SM及SrO/SM)進行轉酯化反應製備生質柴油，除了製備出碳中性之生質柴油外，更結合了磁性固態觸媒，增加觸媒的回收率並能重複使用，達到降低成本以利未來工業上廣泛使用。 藉由磁性固態鹼觸媒對大豆油轉酯化反應找出最適條件，再進行痲瘋樹油兩階段轉酯化反應，並透過分析反應後所得生質柴油性質包括酸價、碘價、動黏度、密度、冷濾點及熱值等性質進行討論。
藉由醋酸鈣為前驅物披覆於磁性顆粒上(CA/SM)會有不均勻現象，且當觸媒Ca濃度(CCa)大於40 wt%時磁性載體會失磁。而由硝酸鈣為前驅物(CN/SM)時披覆較均勻，但由於前驅物熔點低，鍛燒後會有團聚現象導致催化活性低。另外SrO/SM觸媒藉由硝酸鍶為前驅物以含浸法、沉澱法製備時，由於Sr及Fe3O4皆為不穩定物質而導致鍛燒時Sr與載體反應成他物質且容易失磁，使觸媒無轉酯化能力。
CA/SM對大豆油進行轉酯化反應所得最適條件為甲醇與油莫耳比(M : O)為12:1、轉酯化反應溫度(TT)為338 K、反應時間(tT)為7 h、觸媒添加量(MC)為6 wt%及CCa為10 wt%，其產率為94%。然而，CA/SM的重複使用性不佳，使用第二次後產率已下降至60%，主要原因為Ca的溶出及觸媒表面沉積有機物等原因所導致。在對痲瘋樹油轉酯化反應中，產率隨著時間增長而提升，反應時間7 h已近反應平衡，產率達90%。
大豆油生質柴油及痲瘋樹油生質柴油性質如酸價、密度及冷濾點已符合法規標準(CNS 15072)，但含水率皆高於標準規範，可透過硫酸鎂脫水或蒸餾等方式去除水分。另外大豆油生質柴油的碘價及痲瘋樹油生質柴油的黏滯度皆略高於法規，此可藉由摻配方式改善。

關鍵字

生質柴油 ； 大豆油 ； 痲瘋樹油 ； 磁性固體觸媒 ； 轉酯化反應 ； 氧化鈣 ； 氧化鍶

並列摘要

In order to avoid the impact of climate change, the need for a global transition toward a low carbon energy system in urgent. This promotes the use of renewable energy sources for the future development. In this study, transesterifications of soybean oil and jatropha oil to biodiesel using magnetic solid alkali catalysts were examined. The nanometer magnetic catalysts were prepared by loading CaO and SrO onto the SiO2/Fe3O4 (CA/SM, SrO/SM). The magnetic catalyst can be separated easily by exerting magnetic field after transesterification reaction for further recovery, regeneration and reuse. This can simplify the process and decrease costs. A series of transesterification experiments were conducted to find proper operating conditions. The properties of biodiesel produced wewe measured and elucidated.
The results indicated that CA/SM catalysts prepared from calcium acetate were unevenly dispersed with CaO and lost magnetism when Ca concentration in Ca-containg catalyst (CCa) is higher than 40 wt%. In contrast, for the catalyst using calcium nitrate as precursor (CN/SM), calcium oxide was coated on the support SM more uniformly. However, the low melting point of calcium nitrate precursor lead to agglomeration resulting in low catalytic activity after calcination. The catalysts SrO/SM prepared from strontium nitrate by impregnation and precipitation methods lost magnetism easily and exhibited no catalytic capability for transesterification. This maybe attributed to the reactions of Sr and Fe3O4 forming other substances in the calcination process, thus inhibiting the catalytic ability of SrO.
The proper operating conditions for manufacturing soybean-oil biodiesel (SOB) are 12:1 molar ratio of methanol to oil (M : O), 6 wt% of catalyst loading relative to oil (MC) and 10 wt% CaO at 338 K (TT) for 7 h (tT). However, CA/SM reusability was not promising with yield declined from 94% to 60% for the second reuse. The main cause may be due to the dissolution of calcium and deposition of organic matter on catalyst surface. Jatropha-oil biodiesel (JOB) was producted by using a two-stage transesterification process, i.e., pre-esterification followed by post transesterification. The transesterification reaction approached equilibrium after 7 h, achirving yield of 90%.
Properties of soybean-oil biodiesel (SOB) and jatropha-oil biodiesel (JOB) of acid value, density and cold filter plugging point complies with standards (CNS 15072). However, the water contents are higher than the standard. The water in oil can be removed by distillation or magnesium sulfate. Furthermore the iodine value of SOB and kimetic viscosity of JOB are slightly higher than the standards and can be improved by blending with other biodiesel.

並列關鍵字

Biodiesel ； Soybean oil ； Jatropha oil ； Magnetic solid catalysts ； Transesterification ； Calcium oxide ； Strontium oxide

參考文獻

87. 田偲穎，2015，「以超音波輔助半連續式痲瘋油轉酯化程序產製生質柴油」，碩士論文，國立臺灣大學環境工程研究所碩士論文。

91. 吳憶伶，2009，「磁性觸媒應用於催化濕式氧化程序處理水中溶解性污染物之研究」，國立臺灣大學環境工程學研究所碩士論文，台北。

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