Partial hydrogenation of 3-hexyne over Pd, PdW and PdNi

M. JULIANA MACCARRONE; CECILIA R. LEDERHOS; CAROLINA BETTI; FERNANDO COLOMA-PASCUAL; Á. MASTALIR; JUAN C. YORI; MÓNICA E. QUIROGA

Lyon

Congreso; XI EUROPACAT; 2013

The design of highly selective catalytic systems for which there is no need to remove undesirable productsclearly falls within the postulates of the so-called ?Green Chemistry?. The stereoselective hydrogenation of nonterminal alkynes to give alkenes without the occurrence of geometric isomerization is very useful in these processes.When the isomerization reaction is not carried out, the (Z)-alkene (desired product) is mainly formed. There is scarce reports that deal with the selective hydrogenation of long chain non terminal alkynes. In particular, partial hydrogenation reaction of 3-hexyne has been relatively little studied in the literature and generally using supported monometallic or complexes as catalysts . The objectives of this work are: to evaluate the activity and selectivity of catalysts of low Pd content, both monometallic and bimetallic (W?Pd and Pd?Ni) catalysts during 3-hexyne partial hydrogenation; to evaluate the effect of reaction temperature; and to compare the catalytic performance of these catalysts with commercial Lindlar catalyst.All the catalysts are active in the range of temperatures studied, 273?323 K, even at the lowest temperature. In all the cases the (Z)-alkene stereoisomer is obtained as the main product with a very high selectivity comparable to that obtained with the commercial Lindlar catalyst, besides, the selectivities remained approximately constant with temperature. Activity results indicate that higher throughput of the desired product are obtained for WPd/A (firstly), PdNi/A (secondly) and Pd/A (thirdly) than with commercial Lindlar catalyst. Nickel and tungsten proved to be good promoters for the palladium monometallic catalyst as it caused an increment in the activity without modifying the high selectivity to (Z)-3-hexene characteristic of Pd monometallic catalysts. Besides, the prepared catalysts present the advantages of low Pd loading and low cost of nickel or tungstenprecursors, which leads to cheaper and highly active and selective catalysts.