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Title: Selective hydrogenation of hexyne : the influence of sulphur and tin catalyst modifiers
Author: Hagebols, Erik
ISNI:       0000 0004 9353 6380
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2015
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The influence of sulphur and tin modifiers as well as the metal surface structure of the catalyst on the selective hydrogenation of hexyne over Pd/Al2O3 was investigated. Herrero et al.(1) and Jenkins et al.(2) have shown that reductive treatment of catalysts in dilute solutions of modifiers can result in deposition onto specific metal surface features. Anderson et al.(3) blocked step sites of Pd/Al2O3 by this method, which resulted in an increased 1-hexene selectivity during 1-hexyne hydrogenation. In this work contact treatment was compared with impregnation. Tin acetate was also used in a modified Lindlar preparation. Various modifier types were tested: sulphur and tin compounds, organic or inorganic species and sulphides with different counter ions. Furthermore diphenyl sulphide was tested as a reaction additive. Catalysts were investigated using CO-FTIR, DRIFTS, CO adsorption and tested in hexyne hydrogenation. The CO-FTIR spectra of Na2S and diphenyl sulphide (Ph2S) contact treated catalysts showed selective deposition of modifiers on terraces and terrace edges, while impregnation was less selective. Tin acetate deposited preferentially on Pd(111) terraces. Contact treatments with Na2S, diphenyl sulphide and tin acetate reduced the cis-2-hexene, but not the 2-hexyne reaction rates while impregnation reduced both rates. For 1-hexyne hydrogenations both hexyne and hexene reaction rates were diminished. Repeated tin acetate contact treatment increased the cis:trans ratio during cis-2-hexene hydrogenation. The tin-lindlar catalyst increased product selectivity in 1- and 2-hexyne hydrogenation but reduced reaction rates. Contact treatment with (NH4)2S reduced both hexyne and hexene reaction rates, signifying the influence of ammonium. Ph2S was successfully used as a reaction modifier to increased cis-2-hexene selectivity.
Supervisor: Not available Sponsor: Scottish Funding Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Hydrocarbons ; Hydrogenation ; Heterogeneous catalysis