銅/鋅觸媒的鹼性改質對醇反應特性的影響

Effect of the basic metals modifiers on the alcohol reaction over CuO/ZnO catalysts

宋良君(Liang-Chun Sung)

指導教授 ： 林昇佃

元智大學/工程學院/化學工程與材料科學學系/碩士(1998年)

摘要

摘要
本研究探討CuO/ZnO系列觸媒經鹼性改質後的觸媒特性(如比表面積、CO2化學吸附量、程溫脫附性質、XRD及TGA)及催化單醇進料(如甲醇、乙醇、異丙醇及異丁醇)和雙醇進料(如甲醇+異丁醇)進行脫氫及縮合反應現象的影響。
前處理步驟對醇進料的催化反應有顯著影響，經氫氣活化後觸媒縮合活性有顯著提升，特性分析發現可能是因為部份CuO被還原成Cu並參與反應所致，未經氫氣活化觸媒仍然具有醇的脫氫活性，但幾乎不具縮合能力。
單成份進料反應測試發現，CuO/ZnO系列觸媒具有催化醇類脫氫為醛類或酮類的反應特性，且甲醇還有脫氫為一氧化碳的現象，而反應活性大小順序為異丙醇>異丁醇>乙醇>甲醇，其中以異丙醇和乙醇的縮合活性最顯著，可見醇的結構對反應特性有顯著影響。
所測試鹼性改質CuO/ZnO系列觸媒催化甲醇+異丁醇雙成份反應結果發現，經鹼改質觸媒縮合活性皆不如改質前，可能與BET顯著降低與改質觸媒還原Cu量減少有關，與鹼性基強度無明顯關連，測試結果以Na/CuO/ZnO商用觸媒具有最佳縮合反應活性，不過最佳的羥基三甲基乙醛生成活性只對應約10%的選擇率，顯示雙醇於觸媒表面仍是以脫氫反應為主。
以Na/CuO/ZnO商用觸媒進行改變進料成份與比例的測試，發現降低進料WHSV會造成甲醇反應活性降低，異丁醇反應活性無明顯變化，不過縮合產物羥基三甲基乙醛與新戊二醇選擇率會隨WHSV減少而下降。增加氫氣進料量會造成一氧化碳與羥基三甲基乙醛選擇率下降的趨勢，甲醇進料量增加可略增縮合活性，添加三聚甲醛並無法提升縮合活性，但水的添加卻可提升縮合活性。

關鍵字

銅鋅觸媒 ； 醇反應 ； 鹼改質

並列摘要

Abstract
The modification effect of basic metal modifiers on CuO-ZnO catalysts was investigated. These catalysts catalyzed alcohol dehydrogenation into aldehydes or ketones and, in some cases, condensation. The activity of the feed increased as follows: IPA > IBO > EtOH > MeOH. Isopropanol and ethanol show condensation activity and this indicates that the alcohol structure is an important factor.
The pretreatment condition was found to significantly affect the catalytic activity of CuO-ZnO catalysts. Without H2 reduction, the catalysts maintain dehydrogenation activity but almost no condensation was observed. The condensation activity was promoted with H2 pretreatment at 280oC. XRD, TGA and CO2 adsorption analysis showed that CuO was reduced to Cu after H2 reduction. The presence of Cu surface seemed to be an important factor.
From the results of CO2-TPD and kinetic analysis Cu surface area and the catalytic activity decreased with the addition of basic metals modifiers. However, the strength of basic site did not show significantly effect, probably due to the significant reduction of BET surface area with basic metal modification. The Na-CuO-ZnO commercial catalyst showed the highest MeOH+IBO cross-condensation activity after H2 pretreatment at 200oC, but only the condensation selectivity was only 10%. The dehydrogenation was still the major reaction over these CuO-ZnO catalysts.
The effect of feed stream composition was also examined for the MeOH+IBO reaction over Na-CuO-ZnO catalyst. The cross-condensation activity was found to increase by the addition of H2O but not by formalin, trioxane, or CO. The overall IBO activity was almost the same as that in the single-alcohol-feed experiment, but MeOH was obviously suppressed.

並列關鍵字

CuO/ZnO ； Alcohol reaction ； basic metals modifiders

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