層狀複金屬氫氧化物應用於攪拌填充床進行生質柴油之生產及甘油之轉酯化

Biodiesel Synthesis and Glycerol Transesterification by Layered Double Hydroxides in Stirring Packed-Bed Reactor

許毓婷(Yu-Ting Hsu)

指導教授 ： 吳紀聖

國立臺灣大學/工學院/化學工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.00155

摘要

石化能源帶給人們方便，卻也讓人類面臨全球暖化等危機，因此許多人投入研究綠色或是永續能源，生質柴油便是其中重要的一角。生質柴油性質與傳統石化柴油相近，又能和石化柴油混合使用，亦具有無毒、生物可分解性、成分中不含硫化物和芳香族類等優點，因此為目前為重要的替代能源之一。
本研究利用層狀複金屬氫氧化物(Layered Double Hydroxides, LDHs)家族中的Mg-Al LDH作為鹼觸媒，以甲醇和大豆油進行轉酯化反應合成生質柴油，並將生質柴油的副產物甘油轉酯化成更具經濟價值的丙三醇1,2-碳酸酯。本研究探討了Mg/Al比例、鍛燒溫度、反應溫度、觸媒使用量以及碳酸二甲酯/甘油之莫耳比值等因素對於反應性之影響，並將LDH合成於α-Al2O3小球上，填充於攪拌填充床連續式反應系統進行反應。
本研究先將Mg-Al LDH進行鍛燒，再利用去碳酸根水─甘油混合液進行層狀結構之重構，並同時於觸媒表面包覆一層甘油防止觸媒因接觸空氣失活。在大豆油之轉酯化反應中，反應溫度60oC、甲醇/大豆油莫耳比為30:1，Mg/Al=5之觸媒使用量為10wt%時，四小時內可達65.72%，升高溫度至100oC，三小時可達87.45%。在甘油轉酯化反應中，在反應溫度95oC下，碳酸二甲酯/甘油莫耳比值為16，並使用二甲基亞碸作為溶劑， Mg/Al=5之顆粒觸媒用量為總反應系統總重之10wt%時，可於7.5小時內達到93.4%的產率。在四角觸媒柱連續式攪拌反應中，當反應溫度為90oC，碳酸二甲酯/甘油為16，使用Mg/Al=5之顆粒觸媒，用量為反應物總重的約10wt%，在滯留時間22.5小時，可於11小時達到穩態，產率80.17%。

關鍵字

攪拌填充床反應器 ； 層狀複金屬氫氧化物 ； 轉酯化反應 ； 生質柴油 ； 甘油碳酸酯

並列摘要

Fossil fuel brings mankind lots of convenience and boosts the technology development. However, fossil fuel also brings crisis such as global warming and energy shortage. To deal with the problems, many scientists devote themselves into finding green and sustainable energies, and biodiesel is one of them. Biodiesel can be mixed with petro-diesel at any ratio and used in a diesel engine. Biodiesel contains no sulfur and no aromatic compounds. The surge of interest in biodiesel has also highlighted the reduction of greenhouse gas emission and pollution as well as nontoxic and biodegradable.
In this research, we transesterificated (1) triglycerides to synthesize biodiesel and; (2) its byproduct glycerol to form a more valuable chemical, glycerol 1,2-carbonate, using layered double hydroxides (LDHs), specifically Mg-Al LDH. We studied the different Mg/Al ratios in catalyst preparation, calcination temperatures of LDH, reaction temperatures, catalyst loadings and the molar ratios of dimethyl carbonate/glycerol, etc., which are critical factors in both transesterification reactions. We had Mg-Al LDH coated on the 3mm spherical α-Al2O3 catalyst in the stirring packed-bed reactor.
Mg-Al LDH was first calcined and then rehydrated with decarbonated water-glycerol solution to reconstruct the layer structure and also to protect the catalyst deactivation by air at the same time. In biodiesel synthesis, the yield reached 65.72% in 4 hours under 60oC, 87.45% in 3 hours under 100oC, when the methanol/soybean oil molar ratio was set to be 30, and 10wt% Mg/Al=5 LDH was used in the reaction. The glycerol transesterification was carried out by dimethyl carbonate/glycerol molar ratio 16 with the existence of solvent, dimethyl sulfoxide, using 10wt% Mg/Al=5 LDH on spherical α-Al2O3 at 95oC. The yield of glycerol 1,2-carbonate could reach up to 93.4% within 7.5 hours. When applying 10wt% catalyst of Mg/Al=5 LDH on spherical α-Al2O3 into the stirring packed-bed reactor, the yield of glycerol 1,2-carbonate reached to 80.17% within 11 hours under the residence time 22.5 hours, and dimethyl carbonate/glycerol molar ratio = 16 at 90oC.

並列關鍵字

Stirring Packed-Bed Reactor ； Layered double hydroxides (LDHs) ； Transesterification ； Biodiesel ； Glycerol carbonate

參考文獻

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