Kinetic study of the selective hydrogenation of 3-hexyne over W–Pd/alumina catalysts
- 13 Downloads
Low loaded W–Pd/alumina are relatively novel catalysts for performing the selective hydrogenation of alkynes, but there is scarce information on the working mechanism. This work studies the kinetics of the selective hydrogenation of 3-hexyne to (Z)-3-hexene over a low loaded W–Pd/alumina catalyst. Runs at different mild reaction conditions were used for fitting a set of Langmuir–Hinshelwood models. Semihydrogenation was the prevailing reaction path, leading selectively to (Z)-3-hexene > 95%, as with classical Lindlar catalysts. Smaller amounts of (E)-3-hexene and negligible of n-hexane were detected. When considering a pseudo-homogeneous model, approximate orders in 3-hexyne and hydrogen were (2.5) and (− 2.2), respectively. The latter value pointed to an important role of hydrogen chemisorption. Twelve kinetic models were fitted to the experimental data. A normal dissociative adsorption of hydrogen could not account for the high order in hydrogen, hence the adsorption of non-dissociated molecular hydrogen was also taken into account. Best fit model was the one considering adsorption of 3-hexyne as rate-limiting step, with molecular hydrogen acting as a competitor over Pdn+ sites, and with hydrogen being dissociated over other different sites: Pdδ−.
KeywordsBimetallic catalyst Alkyne Selective hydrogenation Kinetics Tungsten Palladium
This work was performed with the financial support of CONICET (Grant PIP 11220130100457CO), ANPCyT (Grant PICT 2016 1453) and Universidad Nacional del Litoral (Grants CAI + D 50420150100074LI and 50420150100028LI).
- 17.Maccarrone MJ, Torres G, Lederhos C, Betti C, Badano JM, Quiroga M, Yori J (2012) Kinetic study of the partial hydrogenation of 1-heptyne over Ni and Pd supported on alumina. In: Karamé I (ed) Hydrogenation, chap 7. InTech, Rijeka, pp 159–184Google Scholar
- 19.Hu SC, Chen YW (1998) Partial hydrogenation of benzene: a review. J Chin Inst Chem Eng, 29:387–396Google Scholar
- 26.NIST X-ray photoelectron spectroscopy database NIST standard reference database 20, Version 3.5 (Web version), National Institute of Standards and Technology, USA, 2007Google Scholar
- 28.Shriver DF, Atkins PW, Langford CH (1994) Inorganic chemistry, 3rd edn. WH Freeman and Co, New York, p 258Google Scholar
- 36.Gva LZ, Kho KE (1988) Kinetics of acetylene hydrogenation on palladium deposited on alumina. Kinet Catal 29:381–386Google Scholar
- 37.Bond G (2005) Metal-catalysed reactions of hydrocarbons. Springer, Berlin. ISBN 978-0-387-24141-8Google Scholar
- 42.Ibhadon A, Kansal S (2018) the reduction of alkynes over pd-based catalyst materials—a pathway to chemical synthesis. J Chem Eng Process Technol 9(2):1000376Google Scholar