Bifunctional catalysts consisting of copper, zinc oxide, and γ -alumina have been produced by means of extrusion. The effects of formulation and forming conditions on morphology, pore texture, and copper surface area are discussed. These extruded catalysts have been employed in the fixed-bed gas-phase conversion of dimethyl maleate at temperatures between 453 and 493 K and space velocities ranging from 0.2 to 2.4 h −1 . Copper catalyzes the hydrogenation and hydrogenolysis reactions yielding γ -butyrolactone, and 1,4-butanediol. γ -Alumina provides weakly acidic sites which promote the subsequent dehydration of 1,4-butanediol to tetrahydrofuran. Coupled products are methanol and water. Through choice of composition and pore texture of the extrudates it is possible to achieve tetrahydrofuran yields of 100% (basis the C 4 -products) at a low pressure (2.5 MPa) in a single stage.
The gas-phase hydrogenolysis of dimethyl maleate at 10 bar and 513 K was investigated over a series of co-precipitated Cu/ZnO/ Al 2 O 3 catalysts. High copper surface areas were obtained with a molar Al content of 5 % in the catalysts. Upon variation of composition at fixed alumina content, copper surface areas increased until the molar ratio exceeded Cu/Zn = 2:1. At the given reaction conditions, dimethyl maleate was completely converted to dimethyl succinate, which further reacted to methanol, c-butyrolactone, tetrahydrofuran, and water over all catalysts. Initial deactivation of catalysts was mainly caused by a loss of copper surface area. The catalyst with a molar Cu/Zn ratio of 1:2 was found to be most active and stable under reaction conditions.
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