Hydrogenation Of Sec-Butyl Acetate To 2-Butanol Over Cu/ZrO₂ Catalyst

To advance understanding of the hydrogenation of sec-butyl acetate?SBA?over Cu-based catalysts,Cu/m-ZrO₂ has been employed as a model catalyst in the thesis to investigate the reaction path and kinetics of the SBA hydrogenation,as well as the structure-function relationship of Cu/m-ZrO₂catalysts with/without B₂O₃ dopant.Several conclusions have been drawn as follows.?1?The crystal phase of ZrO₂?m-ZrO₂ or t-ZrO₂?has little effect on the product distribution of SBA hydrogenation at similar SBA conversions.But the larger surface area of m-ZrO₂ than that of t-ZrO₂ facilitated the dispersion of Cu particles on m-ZrO₂.The average Cu particle size of Cu/m-ZrO₂ increased with increasing the Cu loading,leading to slightly higher selectivity of methyl ethyl ketone?MEK?.The interaction between Cu particles and support is,however,too weak to retard the aggregation of Cu particle in the hydrogenation of SBA,causing serious deactivation after a few catalytic runs.?2?Introduction of B₂O₃ to Cu/m-ZrO₂ enhanced remarkably the interaction between Cu species and support and improved substantially the Cu dispersion on the catalyst surface,thus prolonging the catalyst stability and lifespan in the hydrogenation of SBA.Simultaneously,the addition of B₂O₃ lowered the reducibility of Cu species and their activity toward the hydrogenation of esters.In addition,the strong acidic sites formed after the addition of B₂O₃ brought many acid-catalyzed by-products such as n-butanol and n-butyl acetate.?3?Hydrogenation of SBA over Cu catalysts is a complicated process involving sequential and parallel reaction.Hydrogenation of SBA to 2-butanol is the main reaction,followed by the further hydrogenation to MEK,isomerization to n-butanol or hydration to C₄ olefins.These by-products can be also converted to acetates via the competing esterification or transesterification reactions.The rate equation of the SBA hydrogenation measured in a CSTR can be written as r=0.215×10²e^-2551/Tp?H₂?^1.51c?SBA?^0.0522andr=0.543×10³e^-4411/Tp?H₂?^0.35c?SBA?^0.0556,respectively,for Cu/m-ZrO₂ and Cu/B/m-ZrO₂ catalysts.By comparison,the equation measured in a PBR under low SBA conversions and a fixed molar ratio of H₂/SBA at 10,can be described as r=1.233×10³e^-5522/Tp?H₂?^0.83p?SBA?^0.58.The apparent activation energy for the above reaction in the range of 210°C and 260°C was estimated to be 45.91kJ/mol.