CuZnMgAl觸媒的製備、結構鑑定與甲醇轉化反應特性的探討

CuZnMgAl catalysts: their preparations, structure characterization and performances in methanol conversions

夏棋(MUHAMMAD MUSTAFIZUR RAHMAN BHUIYAN)

指導教授 ： 葉君棣

共同指導教授 ： 林昇佃(Shawn D. Lin)

元智大學/工程學院/化學工程與材料科學學系/碩士(2009年)

摘要

本研究利用沈澱法和含浸法，採用不同流程由鎂、鋁、銅、鋅的硝酸鹽合成四元成分具有Hydyotalcite結構的混合氧化物(HTlcs, hydrotalcite-like compounds)，另以商購Mg-Al HTlcs擔體，經沈澱或含浸添加銅和鋅，以獲得成分相同但製法與結構有所不同的四元Hydyotalcite觸媒。所製備的四元Hydyotalcite觸媒於固定床中進行甲醇反應的探討，GC分析發現除了CO、CO2、甲醛之外，反應產物還包含長碳鏈的產物，不同觸媒製備程序所得四元Hydyotalcite觸媒的反應特性有所不同，研究結果顯示以商購擔體製備的四元Hydyotalcite觸媒的催化活性高於自製之觸媒，並以連續沈澱法添加銅和鋅所得的觸媒有最好的催化活性，且可獲得產率高於90%的甲醇縮合產物。本研究以X光繞射結構分析、熱重分析、與程溫還原分析等方法，嚐試解釋不同流程所製備觸媒的活性與選擇性之差異，推測是以Cu-Zn-Mg-Al在Hydrotalcite結構中的排列關係是影響甲醇催化反應的重要因子。

關鍵字

Hydrotalcite ； 甲醇 ； 縮合反應 ； X光繞射

並列摘要

The present work prepared tetra-cationic Hydrotalcite like compound (HTlc) from nitrate salts of Mg, Al, Cu and Zn by different sequences of precipitation and impregnation. A similar series of catalysts were also fabricated through deposition and impregnation of CuO and ZnO on commercial Mg-Al HTlc.

The prepared tetra-cationic HTlcs were used as catalysts to study methanol condensation reaction. A fix-bed reactor was used to study the activity of the prepared catalysts. GC was used to analyze the products. CO, CO2, formaldehyde and condensation products with negligible dimethyl ether were obtained. The activity and the selectivity over different catalysts were systematically examined.

(MA)c supported HTlcs exhibited higher catalytic activity than the homemade HTlcs. HTlcs obtained by sequential deposition of Cu and Zn over (MA)c exhibited the best catalytic activity at 300 0C with 90% yield of higher oxygenates from methanol. Only (MA)c and HTlcs derived from it contained Boehmite structure. Accordingly, the structure of Cu-Zn-Mg-Al HTlc was assumed to be the determining factor for the catalytic activity of methanol condensation.

並列關鍵字

Hydrotalcite ； symmetry ； oxygenates

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