苯酞(Phthalide)是一種用於醫藥、精細化學品和有機合成的重要工業中間體，其使用範圍非常廣泛，過去使用化學還原法製備苯酞，有過程繁複與環境污染等問題，因此將苯酐(Phthalic Anhydride, PA)直接氫化為苯酞，免去繁複的過程也減少污染物產生，成為一種備受矚目的方式。本研究使用非均相觸媒在液相溶液中將PA氫化為Phthalide，在觸媒方面分為不同製備方式、不同擔體以及活性金屬三個方向進行探討。在觸媒製備方法中以SBA-15作為擔體，分別使用初濕含浸法(Incipient Wetness Impregnation, IWI)、化學流體沉積法(Chemical Fluid Deposition, CFD)製備鎳鐵觸媒，發現氫化效果為CFD > IWI，因超臨界二氧化碳幾無黏度的特性能夠使奈米金屬更加均勻分散於擔體中，進而獲得更小的粒徑，因此具備更高的催化活性。
擔體研究以CFD法合成不同擔體的鎳鐵觸媒，結果發現SBA-15因具有較小的孔徑，因此可以限制奈米金屬成長而具較好的催化活性；MCF則因較大的孔道減少了反應物滯留的時間，避免過度反應而有較佳的選擇性。
於活性金屬探討方面，為了增加觸媒活性，在原本的鎳鐵觸媒基礎上引入2.5 wt%的Pt，因Pt金屬具較強的CO鍵解離能力，能有效幫助PA轉化為Phthalide，但對比於純鎳鐵觸媒，Pt的引入雖能有效提升轉化率，同時也增加副反應的進行。
最後本研究也探討了反應時間對PA氫化的影響，反應過程中除了目標產物Phthailde的生成外，同時也生成副產物O-Toluic acid及其衍生物，根據文獻提出的推測反應途徑認為此過程為一串聯反應，因此嘗試改變反應時間，觀察產物中各成分的比例與反應時間的關係，發現Phthalide的生成速率與PA濃度呈正相關，而O-Toluic acid等副產物生成速率則與Phthalide濃度無關。

Phthalide is an important industrial intermediate with significant applications in medicine, fine chemicals and for organic synthesis. Generally, phthalide is prepared using a chemical reduction method, which is complicated and leads to environmental pollution. Thus, the direct hydrogenation of phthalic anhydride (PA) to phthalide, and thereby eliminating the complexities of the reduction process and reducing the generation of pollutants has become highly coveted. This study reports the development of selective heterogeneous catalyst to hydrogenate PA to phthalide in a liquid solution through comparing different catalyst synthesis methods, choice of support material and the selection of active metals. Initially, SBA-15 was used as the support and Ni-Fe bimetallic catalysts were synthesized using incipient wetness impregnation (IWI) and chemical fluid deposition (CFD) to prepare nickel-iron catalysts. The CDF catalyst was found to be superior to the IWI catalyst. This was attributed to the uniform distribution and small particle size of the Ni-Fe alloy nanoparticles in the CFD catalyst since the low viscosity and almost negligible surface tension of supercritical CO2 made it easy to deposit the Ni-Fe alloy nanoparticles inside the pores of well-ordered SBA-15.
Based on this result, while studying the effect of support material on the hydrogenation of PA to phthalide, all catalysts were synthesized using the CFD method. Well-ordered 2-dimensional SBA-15 was compared to a disordered 3-dimensional mesocellular foam (MCF) support as it was found that the SBA-15 supported catalyst had better hydrogenation activity than the MCF supported catalyst. However, the MCF supported catalyst had a higher selectivity for phthalide. It was reasoned that since SBA-15 had a smaller pore size than MCF, the Ni-Fe alloy nanoparticle size could be limited by the pore opening. Smaller Ni-Fe alloy nanoparticles meant better dispersion and a higher number to active sites in the support and therefore better hydrogenation activity. The MCF catalyst on the other hand reported better selectivity for phthalide due to its large pores, that reduced retention time of the hydrogenated product inside the pores of the catalyst, thereby preventing overreaction.
In order to further increase catalyst activity, 2.5 wt% Pt was introduced to the original Ni-Fe catalyst. Since Pt has a strong CO bond dissociation ability, it was expected to increase the hydrogenation of PA to phthalide. However, when compared to the Ni-Fe catalyst, although Pt enhanced the conversion rate, it also increases the generation of side reactions.
Finally, the effect of reaction time on PA hydrogenation was studied. In addition to the formation of the desired product phthailde, o-toluic acid and its derivatives were also produced as by-products with an increase in by-product selectivity observed with increase in time. Based on speculation that the reaction pathway for the hydrogenation of PA to phthalide and subsequent by-products is a series reaction and experimental estimation of phthalide and by-products formed during the hydrogenation of PA with respect to increasing time, it was thus concluded that the rate of formation of phthalide was directly proportional to the concentration of PA in the reactant solution. The rate of formation of by-products was independent of the concentration of phthalide formed.

[1] K. Massonne, R. Becker, W. Reif, J. Wulff-Doering, Preparation of phthalide from phthalic anhydrides using nickel catalysts, in: BASF AG, WO, 1998.
[2] Phan-Vu, D.H., Tan, C.S. 2017. Synthesis of phthalate-free plasticizers by hydrogenation in water using RhNi bimetallic catalyst on aluminated SBA-15. Rsc Advances, 7(30), 18178-18188.
[3] Yen, C.H., Lin, H.W., Tan, C.S. 2011. Hydrogenation of bisphenol A - Using a mesoporous silica based nano ruthenium catalyst Ru/MCM-41 and water as the solvent. Catalysis Today, 174(1), 121-126.
[4] Yu, W., Hsu, Y.P., Tan, C.S. 2016. Synthesis of rhodium-platinum bimetallic catalysts supported on SBA-15 by chemical fluid deposition for the hydrogenation of terephthalic acid in water. Applied Catalysis B-Environmental, 196, 185-192.
[5] Lekhal, A., Glasser, B.J., Khinast, J.G. 2001. Impact of drying on the catalyst profile in supported impregnation catalysts. Chemical Engineering Science, 56(15), 4473-4487.
[6] Vandergrift, C.J.G., Wielers, A.F.H., Mulder, A., Geus, J.W. 1990. The Reduction Behavior of Silica-Supported Copper-Catalysts Prepared by Deposition Precipitation. Thermochimica Acta, 171, 95-113.
[7] Erkey, C. 2009. Preparation of metallic supported nanoparticles and films using supercritical fluid deposition. Journal of Supercritical Fluids, 47(3), 517-522.
[8] Dhepe, P.L., Fukuoka, A., Ichikawa, M. 2003. Novel fabrication and catalysis of nano-structured Rh and RhPt alloy particles occluded in ordered mesoporous silica templates using supercritical carbon dioxide. Physical Chemistry Chemical Physics, 5(24), 5565-5573.
[9] Chatterjee, M., Ikushima, Y., Hakuta, Y., Kawanami, H. 2006. In situ synthesis of gold nanoparticles inside the pores of MCM-48 in supercritical carbon dioxide and its catalytic application. Advanced Synthesis & Catalysis, 348(12-13), 1580-1590.

[10] Yu, W., Lin, H.W., Tan, C.S. 2017. Direct synthesis of Pd incorporated in mesoporous silica for solvent-free selective hydrogenation of chloronitrobenzenes. Chemical Engineering Journal, 325, 124-133.
[11] Behrens, P., Stucky, G.D. 1993. Ordered Molecular Arrays as Templates - a New Approach to the Synthesis of Mesoporous Materials. Angewandte Chemie-International Edition in English, 32(5), 696-699.
[12] Zhao, D.Y., Feng, J.L., Huo, Q.S., Melosh, N., Fredrickson, G.H., Chmelka, B.F., Stucky, G.D. 1998. Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores. Science, 279(5350), 548-552.
[13] Beck, J.S., Vartuli, J.C., Roth, W.J., Leonowicz, M.E., Kresge, C.T., Schmitt, K.D., Chu, C.T.W., Olson, D.H., Sheppard, E.W., Mccullen, S.B., Higgins, J.B., Schlenker, J.L. 1992. A New Family of Mesoporous Molecular-Sieves Prepared with Liquid-Crystal Templates. Journal of the American Chemical Society, 114(27), 10834-10843.
[14] Schmidt-Winkel, P., Lukens, W.W., Zhao, D., Yang, P., Chmelka, B.F., Stucky, G.D. 1999. Siliceous mesostructured cellular foams with uniformly sized and shaped pores. Organic/Inorganic Hybrid Materials Ii, 576, 241-246.
[15] Liu, Y.X., Xing, T.F. 2013. Effects of Heat Treatment Temperatures on the Performance of Au/TiO2 Catalyst for Liquid Phase Selective Hydrogenation of Phthalic Anhydride. Asian Journal of Chemistry, 25(5), 2833-2835.
[16] Liu, Y.X., Wei, Z.J., Xing, T.F., Lu, M., Li, X.N. 2015. Performance of Au/FeOx-TiO2 catalyst for liquid phase selective hydrogenation of phthalic anhydride to phthalide. Journal of Industrial and Engineering Chemistry, 23, 321-327.
[17] Liu, Y.X., Gu, Y.J., Hou, Y.X., Yang, Y., Deng, S.G., Wei, Z.J. 2015. Hydrophobic activated carbon supported Ni-based acid-resistant catalyst for selective hydrogenation of phthalic anhydride to phthalide. Chemical Engineering Journal, 275, 271-280.

[18] Zhang, L.L., Chen, X., Jin, S.H., Di, X., Williams, C.T., Peng, Z.J., Liang, C.H. 2016. Highly selective hydrogenation of phthalic anhydride to phthalide over CoSix/CNTs catalyst prepared by multi-step microwave-assisted chemical vapor deposition. Materials Chemistry and Physics, 180, 89-96.
[19] Zhang, L.L., Chen, X., Chen, Y.J., Peng, Z.J., Liang, C.H. 2019. Acid-tolerant intermetallic cobalt-nickel silicides as noble metal-like catalysts for selective hydrogenation of phthalic anhydride to phthalide. Catalysis Science & Technology, 9(5), 1108-1116.
[20] Sitthisa, S., An, W., Resasco, D.E. 2011. Selective conversion of furfural to methylfuran over silica-supported Ni-Fe bimetallic catalysts. Journal of Catalysis, 284(1), 90-101.
[21] Wei, L., Zhao, Y.X., Zhang, Y.H., Liu, C.C., Hong, J.P., Xiong, H.F., Li, J.L. 2016. Fischer-Tropsch synthesis over a 3D foamed MCF silica support: Toward a more open porous network of cobalt catalysts. Journal of Catalysis, 340, 205-218.
[22] Xing, M.Y., Qi, D.Y., Zhang, J.L., Chen, F., Tian, B.Z., Bagwas, S., Anpo, M. 2012. Super-hydrophobic fluorination mesoporous MCF/TiO2 composite as a high-performance photocatalyst. Journal of Catalysis, 294, 37-46.
[23] Qi, D.Y., Xing, M.Y., Zhang, J.L. 2014. Hydrophobic Carbon-Doped TiO2/MCF-F Composite as a High Performance Photocatalyst. Journal of Physical Chemistry C, 118(14), 7329-7336.
[24] Zhu, J., Holmen, A., Chen, D. 2013. Carbon Nanomaterials in Catalysis: Proton Affinity, Chemical and Electronic Properties, and their Catalytic Consequences. Chemcatchem, 5(2), 378-401.
[25] Schnorr, J.M., Swager, T.M. 2011. Emerging Applications of Carbon Nanotubes. Chemistry of Materials, 23(3), 646-657.
[26] Tauster, S.J., Fung, S.C., Baker, R.T.K., Horsley, J.A. 1981. Strong-Interactions in Supported-Metal Catalysts. Science, 211(4487), 1121-1125.

[27] Wei, Q., Li, Y., Zhang, T., Tao, X.J., Zhou, Y.S., Chung, K., Xu, C.M. 2014. TiO2-SiO2-Composite-Supported Catalysts for Residue Fluid Catalytic Cracking Diesel Hydrotreating. Energy & Fuels, 28(12), 7343-7351.
[28] Wang, R., Liu, X.W., He, Y., Yuan, Q., Li, X.T., Lu, G.Y., Zhang, T. 2010. The humidity-sensitive property of MgO-SBA-15 composites in one-pot synthesis. Sensors and Actuators B-Chemical, 145(1), 386-393.
[29] Qi, S.T., Cheney, B.A., Zheng, R.Y., Lonergan, W.W., Yu, W.T., Chen, J.G.G. 2011. The effects of oxide supports on the low temperature hydrogenation activity of acetone over Pt/Ni bimetallic catalysts on SiO2, gamma-Al2O3 and TiO2. Applied Catalysis a-General, 393(1-2), 44-49.