甲醇氧化羰基化觸媒催化性能之提昇研究

Improving Oxidative Methanol Carbonylation Catalysts

鄭鈺婷(Yu-Ting Cheng)

指導教授 ： 張仁瑞

國立中正大學/工學院/化學工程學系/碩士(2013年)

摘要

本研究目的乃在於製備以甲醇生產碳酸二甲酯之氧化羰基化觸媒並且其主要目的為提昇觸媒之穩定性。研究中選用HY Zeolite (CBV760)、活性碳(GAC830)與二氧化矽(CARIACT 50)為擔體並以微濕含浸法製備銅觸媒。經由連續式固定床反應器測試觸媒的催化活性並藉由XRPD (X-ray powder diffraction)與XAS (X-ray absorption spectroscopy)儀器分析觸媒之結構，使用氣相層析儀(Gas Chromatography)分析甲醇之轉化率及產物之選擇性，以及氣相層析質譜儀(GC-Mass)鑑定產物之成分。催化性能結果得知在壓力400psig下最適化之反應溫度為130C。更高的反應溫度及更低氧氣分壓會使反應從羰基化反應轉變成脫水反應。此外，結合催化性能及結構特性之結果發現晶相Cu2(OH)3Cl是氧化羰基化反應的主要活性點，而此物種傾向與水反應使晶相轉變成銅氧化物，因而導致觸媒的失活。既然在反應過程中無法避免水的產生，因此製備疏水性觸媒抑制Cu2(OH)3Cl與水反應以降低觸媒的失活速率似乎是一種可行的方法。藉由生長奈米碳管於粒狀SiO2以製備疏水性銅觸媒，如預期的該催化劑比無還原性的金屬氧化物支撐式催化劑表現出更好的催化穩定性。然而奈米碳管層的質傳阻力會降低有效因子而使得一開始的總反應速率下降。

關鍵字

甲醇 ； 碳酸二甲酯 ； 粉末X光繞射 ； 銅觸媒 ； 二氯化銅

並列摘要

The goal of this study is to prepare oxidative carbonylation catalysts for the production of DMC (dimethyl carbonate) from methanol and the specific goals are to improve the stability of the catalysts. Supported copper catalysts were prepared by incipient wet impregnation technique and HY Zeolite (CBV760), active carbon (GAC830) and SiO2 (CARIACT 50) were used as catalysts supports. The structure of catalysts was characterized by synchrotron XRPD (X-ray powder diffraction) and XAS (X-ray absorption spectroscopy) while the performance of the catalysts were examined by a continuous fixed bed reaction system. Species formed in the reaction were identified by GC-Mass and the concentration was determined by GC. The catalytic performance results show the optimal reaction temperature is at 130C under the pressure of 400 psig. Higher reaction temperature and lower air flow rate turns the catalytic reaction from carbonylation to dehydration reaction. In addition, the combination of catalytic performance and structural characterization results suggested that Cu2(OH)3Cl are the main sites for oxidative carbonation, whereas the species tend to react with water and convert to copper oxides, leading to a catalyst deactivation. Since water formation in the reaction is unavoidable, preparation of hydrophobic catalysts so as to inhibit the reaction of Cu2(OH)3Cl with water seems a feasible way to slow down the catalyst deactivation rate. The hydrophobic catalyst was prepared by growing carbon nanotube on pellet SiO2. As expected, the catalyst exhibited much better stability than did non-reducible metal-oxide supported catalysts. However, diffusion
resistance of the carbon nanotube layer decrease the effectiveness factor and thus decrease the overall reaction rate at the start of run.

並列關鍵字

Methanol ； Dimethyl Carbonate ； X-ray Powder Diffraction ； Cu catalyst ； Copper dichloride

參考文獻

Lee J. F., “Application of X-ray Absorption Sepectroscopy to Catalyst Characterization”, Chemistry, 53, 280 (1995)

陳世揚，氧化羰基化甲醇觸媒之合成，結構，與催化反應研究，碩士論文，國立中正大學化學工程研究所，第43-53頁，民國一百零一年。

Aresta M. and Quaranta E., “Mechanistic studies on the role of carbon dioxide in the synthesis of methylcarbamates from amines and dimethylcarbonate in the Presence of CO2”, Tetrahedron, 47, 9489-9502 (1991)

Babad H. and Zeiler A. G., “The Chemistry of Phosgene”, Chemical Reviews, 73, 75 (1973)

Chin C. S., Shin D., Won G., Ryu J., Kim H. S. and Lee B. G., “The effects of catalyst composition on the catalytic production of dimethyl carbonate”, Journal of Molecular Catalysis A：Chemical, 160, 315-321 (2000)