Process Optimization for a Sustainable and Selective Conversion of Fumaric Acid into γ-Butyrolactone Over Pd-Re/SiO2

Rhenium – A Tuneable Player in Tailored Hydrogenation Catalysis

“…An important area of research in nanotechnology is the synthesis of nanoparticles (NPs) using water as the solvent [38] . Aqueous impregnation of the support with rhenium precursors can be easily achieved due to the high water‐solubility of Re +7 compounds, such as NH 4 ReO 4 and Re 2 O 7 , which makes this methodology one of the most commonly used in the rhenium‐based catalysts field [26,27,30–34,39,40] . This process usually leads to very small nanoclusters of ReOx (<2 nm), which are usually not observable on x‐ray diffraction (XRD) patterns due to their small size, and a mixture of different stable oxidation states of Re, according to x‐ray photoelectron spectroscopy (XPS), [26,27,41] as illustrated by Figure 1.…”

“…More recently, Figueredo et al [39] . also studied a bimetallic PdRe/SiO 2 catalyst in the hydrogenation of fumaric acid in aqueous media.…”

“…As seen on the previous sections, rhenium, in the form of ReO x , is often used as a dopant for other noble metals that are more commonly known for dissociating H 2 , such as Au, Pd, Pt, Ir or Rh [39,134] . Nevertheless, rhenium can also be the single active metal in certain hydrogenation reactions, even in its oxide form, [27,134] where it is most often found in a mixture of oxidation states as evidenced by XPS analyses [27] .…”

“…In reactions where rhenium is the single active metal, the product is often only partially hydrogenated – for instance, CH 3 OH instead of CH 4 in the hydrogenation of CO 2 , [26,27] or gamma‐butyrolactone instead of butanol when starting from succinic acid [39,112] . Interestingly, Liu et al.…”

“…Fumaric acid was converted entirely into GBL with a selectivity to GBL as high as 91 %. Using statistical analysis, the authors have predicted that temperature and pressure have a non‐linear effect on reaction selectivity [39] …”