Palladium membrane ethylene hydrogenation

Ceramic and semiconductor thin films have been prepared by a number of methods including chemical vapor deposition (CVD), spray-coating, and sol-gel techniques. In the present work, the sol-gel method was chosen to prepare uniform, thin films of titanium oxides on palladium Titanium oxide was chosen because of its versatility as a support material and also because the sol-gel synthesis of titania films has been clearly described by Takahashi and co-workers (22). The procedure utilized herein follows the work of Takahashi, but is modified to take advantage of the hydrogen permeability of the palladium substrate. Our objective was to develop a reliable procedure for the fabrication of thin titania films on palladium, and then to evaluate the performance of the resulting metalloceramic membranes for hydrogen transport and ethylene hydrogenation for comparison to the pure palladium membrane results. 

A.F.Y. Al-Shammary, I T. Caga, J.M. Winterbottom, A.Y. Tate and I.R. Harris, Palladium-Based Diffusion Membranes as Catalysts in Ethylene Hydrogenation , J. Chem. Tech. Biotech., 52 571-85 (1991). 

H. Nagamoto, H. Inoue, Mechanism of ethylene hydrogenation by hydrogen permeable palladium membrane, J. Chem. Eng. Japan 14 311 (1981). 

Harris, Palladium-based diffusion membranes as catalysts in ethylene hydrogenation,/. Chem. Tech. Biotechnol. 1991, 52, 571-585. 

F.L. Chen, Y. Kinari, F. Sakamoto, Y. Nakayama and Y. Sakamoto, Hydrogen Permeation through Palladium-Based Alloy Membranes in Mixtures of 10% Methane and Ethylene in the Hydrogen , Int. J. Hydrogen Energy, 21 [7] 555-61 (1996). 

Shown in Table 8.6 arc some literature data on the use of dense membrane reactors for liquid- or multi-phase catalytic reactions. Compared to gas/vapor phase application studies, these investigations are relatively few in number. Most of them involve hydrogenation reactions of various chemicals such as acetylenic or ethylenic alcohols, acetone, butynediol, cyclohexane, dehydrolinalool, phenylacetylene and quinone. As expected, the majority of the materials adopted as membrane reactors are palladium alloy membranes. High selectivities or yields are observed in many cases. A higher conversion than that in a conventional reactor is found in a few cases. 

On the metallic membrane side, a well known type of material with this characteristic is Pd and certain Pd alloys. Palladium is known to be catalytic to many reactions including oxidation, hydrogenation and hydrocracking. It has been found that the catalytic activity of selected binary Pd alloys is higher than that of pure Pd. Silver catalyzes a number of oxidation reactions such as oxidation of ethylene and methanol. In addition, nickel is catalytic to many industrially important reactions. 

Metal- and alloy-containing membranes are currently applied mainly in ultrapure hydrogen production. Pilot plants with palladium alloy tubular membrane catalyst were used in Moscow for hydrogenation of acetylenic alcohols into ethylenic ones. In the Topchiev Institute of Petrochemical Synthesis, a laboratory-scale reactor of the same type was tested... 

A.N. Karavanov and V.M. Gryaznov, The liquid-phase hydrogenation of acetylenic and ethylenic alcohols on the membrane catalysts from the palladium-nickel and palladium-nithenium binary alloys, Kinetika i Kataliz 25 69 (1984). 

---