應用銅-鈀/二氧化鋯雙金屬觸媒於羥甲基糠醛與異丙醇之催化轉移氫化反應

Transfer Hydrogenation of 5-Hydroxymethylfurfural with Isopropanol over Copper-Palladium Bimetallic Nanoparticles Supported on Zirconia

古浩銓(Hao-Chuan Ku)

指導教授 ： 游文岳

國立臺灣大學/工學院/化學工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202234

摘要

本研究目標研發催化轉移氫化(catalytic transfer hydrogenation, CTH)異相觸媒，將生質資源與液態氫源異丙醇進行反應，轉換成高值化的化學品。我們以共含浸法製備Cu-Pd/ZrO2雙金屬觸媒，應用於羥甲基糠醛(5-hydroxymethylfurfural, HMF)與異丙醇之加氫脫氧反應(hydrodeoxygenation)，生成新一代生質燃油—二甲基呋喃(2,5-dimethylfuran, DMF)。反應測試結果顯示，Cu-Pd/ZrO2觸媒的反應物轉化率與產物選擇率皆優於相應之單金屬觸媒(Cu/ZrO2和Pd/ZrO2)。雙金屬觸媒優異的催化表現可歸因於Cu-Pd兩金屬之協同作用，包含三個層面：金屬分散性、幾何效應與電荷效應。觸媒物化性質鑑定指出，雙金屬形成合金顆粒後使得金屬分散度提升，增加觸媒活性表面積。再者，我們應用一氧化碳吸附紅外光譜與氫氣脈衝吸附實驗等表面探測技術，發現雙金屬擔載比例可改變Pd位點連續性，進而影響生質衍生物與異丙醇氫源之交互作用，此現象亦利用密度泛函理論計算得到證實。觸媒化學環境鑑定則觀察到，Cu-Pd雙金屬表面存在電荷傳遞效應，其中Cuδ+位點可作為路易士酸性位點幫助吸附異丙醇，並脫去異丙醇中羥基的H原子，生成異丙氧基反應中間體；而Pdδ-位點能攫取異丙氧基的α-H原子，完成異丙醇脫氫反應。此外，Pd1/Cu(111)活性位點構型亦有利於舒緩異丙醇、羥甲基糠醛及含氧反應中間產物在觸媒表面的競爭型吸附，進而促進二甲基呋喃的選擇性生成。

關鍵字

催化轉移氫化 ； 雙金屬觸媒 ； 羥甲基糠醛 ； 二甲基呋喃 ； 異丙醇

並列摘要

This research is aimed at developing heterogeneous catalysts for catalytic transfer hydrogenation of biomass resources into value-added chemicals using isopropanol (IPA) as the liquid hydrogen source. In this work, Cu-Pd/ZrO2 bimetallic catalysts were prepared by co-impregnation method for the hydrodeoxygenation of 5-hydroxymethylfurfural (HMF) with IPA to form 2,5-dimethylfuran (DMF), a next-generation biofuel. Catalytic reaction tests show that Cu-Pd/ZrO2 exhibits higher bio-derived substrate conversion and product selectivity than its monometallic counterparts (i.e., Cu/ZrO2 and Pd/ZrO2). The outstanding catalytic performance of Cu-Pd/ZrO2 is attributed to the synergistic effect of Cu-Pd conjunction, which includes metal dispersion, geometric and electronic effect. Physicochemical characterization indicates that the formation of Cu-Pd alloy raises metal dispersion, increasing the active surface area. Also, on the basis of surface probing techniques, such as CO-chemisorbed infrared spectra and H2 pulse chemisorption, we observed that the continuity of Pd sites could be controlled by tuning the loading ratio of Cu-Pd metals, which further influence the interaction of bio-derivatives and IPA and was proved by theoretical investigation employing density functional theory (DFT) calculations. Characterizations on chemical environment of the catalysts found that the electron transfer occurs on the Cu-Pd bimetallic surface, where the Cuδ+ could serve as Lewis acid site to adsorb isopropanol and help abstract the hydroxyl H in IPA to form isopropoxide intermediate, and Pdδ- could dissociate the α-H from the isopropoxide to complete the dehydrogenation of IPA. Additionally, the observed configuration of Pd1/Cu(111) active sites is beneficial to relieve the competitive adsorption among IPA, HMF, and other oxygen-containing reaction intermediates on the catalyst surface, thus promoting the selective formation of 2,5-dimethylfuran.

並列關鍵字

catalytic transfer hydrogenation (CTH) ； bimetallic catalyst ； 5-hydroxymethylfurfural ； 2,5-dimethylfuran ； isopropanol

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