Photocatalytic semi-hydrogenation of acetylene into ethylene with a thiomolybdate cluster [Mo3S13]2- catalyst.

This thesis describes the synthesis, characterization, and employment of a non-noble metal cluster [Mo3S13]2- as catalyst for the semi-hydrogenation of acetylene to ethylene. Ethylene, one of the world’s most important commodity chemicals, is an important starting material for the production of roughly 60% of all plastics. Nearly 200 million tons of crude ethylene are generated globally each year via steam cracking, a process that inevitably yields 0.5–2 vol% acetylene as an impurity. Because acetylene poisons the catalysts used in ethylene polymerization, it must be removed to obtain polymer-grade ethylene. The current state-of-the-art method for purifying crude ethylene is the thermocatalytic hydrogenation of acetylene to ethylene. Although this is a well-established industrial technology, it presents several drawbacks, including the requirement for (i) an external H2 feed, (ii) elevated temperature and pressure, and (iii) a noble-metal catalyst susceptible to overhydrogenation to ethane. This thesis aims to extend the use of the thiomolybdate nanocluster [Mo3S13]2- to the photocatalytic semi-hydrogenation of acetylene to ethylene, not only to the consolidated HER, through a preliminary screening of the homogeneous phase reaction conditions and an initial study on their influence on the reaction mechanism. The system used has the advantage of operating at room temperature, with UV-vis light and without the use of noble metals, offering a sustainable and cost-effective route for this industrially relevant reaction, with substantial advantages over current energy-intensive hydrogenation technology.