臺灣博碩士論文加值系統

利用批式反應器，研究甲醇與第三丁基醇在固體酸觸媒合成甲基第三丁基醚。選擇三種系列的固體酸觸媒:(1)不同矽-鋁比值之HZSM-5、HY與Hβ；(2)金屬氧化物及陽離子交換樹脂；以及(3)酸修飾之Hβ(75)。利用表面積測試儀與氨的溫度程控脫附儀，鑑定觸媒之表面積與酸性。
觸媒性質的鑑定結果顯示：(1)HZSM-5、HY與Hβ沸石，隨著矽鋁比值的增加，酸強度明顯增加而酸量則減少。表面積介於300∼600m2/g。(2)酸修飾之Hβ(75)，其酸強度及酸量大小順序為10-wt%H2SO4/Hβ(75)≧3-wt% SO4(-2)/Hβ(75)＞10-wt% H3PO4/Hβ(75)＞10-wt% TFA/Hβ(75)，其表面積皆比未修飾前小。(3)金屬氧化物之表面積與酸量皆小於沸石。
甲基第三丁基醚的生成隨反應溫度增加而減少，亦隨酸強度及表面積增加而增加，而反應時間的影響不大。在酸修飾沸石中，因10-wt% H2SO4/Hβ(75)的表面積及酸強度比其它酸修飾觸媒佳，所以反應效果較好。金屬氧化物之酸性與表面積皆比沸石小，故反應效果亦比沸石差。
甲醇與第三丁基醇之脫水反應分別經由分子間及分子內脫水生成甲基第三丁基醚與異丁烯，觸媒具有較強的酸強度與大的表面積，且於低溫下，有利於分子間脫水。實驗結果顯示，選擇甲醇與第三丁基醇莫耳比為1.5，利用氧化矽／氧化鋁莫耳比75之Hβ沸石，於95℃催化反應4小時，可得最佳產率之甲基第三丁基醚。

The synthesis of methyl tert.-butyl ether (MTBE) from methanol and tert.-butanol on solid acid catalysts was studied by using a batch reactor. Three types of catalysts were utilized: (1) HZSM-5, HY and Hβzeolites with difference SiO2/Al2O3; ratios; (2) Metal oxides and the cation-exchanged resin; (3) Hβp(75) modified with acids. The surface area and the acidity of catalysts were characterized by the methods of surface adsorption and temperature programmed desorption of ammonia.
The catalyst characterized shows the following results: (1) For HZSM-5, HY and Hβ zeolites, a decrease of SiO2/Al2O3 mole ratio results in the decrease of catalyst acidic strength; (2) For Hβ(75) modified with acid, the surface areas decrease evidently. The relative magnitude of both acid amount and acidic strength follows the order of 1O-wt% H2SO4/ Hβ(75)＞3-wt% S04(-2)/Hβ(75)＞10-wt% H3PO4/Hβ(75)＞10-wt% TFA/Hβ(75); (3) The surface area and acid amount of metal oxides are less than those of zeolites.
The selectivity of MTBE increases with increasing the acidic strength and the surface area of catalysts, but it decreases with increasing the reaction temperature. Among the acid modified Hβ(75) zeolites, 10-wt% H2SO4/Hβ(75) exhibits better catalytic results due to its higher surface area and acidic strength.
The dehydration of methanol and tert.-butanol leads to the formation of MTBE and isobutene via intermolecular and intermolecular dehydration, respectively. Intermolecular dehydration is favored with large surface area and high acidic strength of catalysts. According to the experimental results, the optimum conditions for the MTBE yield are Hβ(75) zeolite, methanoi /tert.-butanol mole ratio 1.5 , reaction temperature 95℃ and reaction time 4 hours.