Hydrogenation reactions play a crucial role in chemicals production, as well as in purification processes. A notable example is the removal of alkadienes/alkynes impurities from alkene streams. This process poses important challenges since all the species in the gas mixture can potentially be hydrogenated, hence particularly selective catalysts are required. Supported copper nanoparticles are nowadays proposed as a promising alternative to supported noble metal hydrogenation catalysts. Nonetheless, little is known about their stability and selectivity to intermediate, unsaturated species. Herein, we discuss the catalytic behavior of nanosized Cu nanoparticles supported on silica for the selective hydrogenation of 1,3-butadiene in presence of a 100-fold excess of propene. We show that the use of silica as support guarantees high stability, while almost full selectivity to alkenes can be achieved by the fine tuning of the Cu nanoparticle size. Supported Cu catalysts were prepared via thermal decomposition of Cu(NO3)2-impregnated silica gel. The Cu particle size (2-10 nm) was varied by tuning the Cu weight loading (6-18%), decomposition temperature and gas atmosphere (H2, N2 or NO). The samples exhibited full conversion of 1,3-butadiene between 130 and 180 °C, with the preferential production of 1-butene (70%). The conversion of propene was as low as 0.01% (7 nm Cu/SiO2) and the selectivity to butenes was above 90% at full 1,3-butadiene consumption (up to 99% for 7 nm Cu). The rate of hydrogenation of 1,3-butadiene was found to be 0.25th and 1st order respectively in 1,3-butadiene and hydrogen partial pressure. Kinetic analysis revealed that the high selectivity can be ascribed to the competitive adsorption of alkadienes rather than alkenes on the surface of Cu. Furthermore, the catalysts can retain their initial particle size and activity for as long as 60 h on stream at 140 °C, showing that SiO2-supported Cu nanoparticles are highly selective and stable hydrogenation catalysts.

Supported Cu nanoparticles as selective and stable catalysts for the gas phase hydrogenation of 1,3-Butadiene in alkene-rich feeds

ACS Spring Meeting 2021

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