Cu/Zn/Zr catalysts for the production of environmentally friendly solvents

New catalytic systems without chromium were investigated in the gamma-butyrolactone (GBL) synthesis by vapour phase hydrogenation of maleic anhydride (MA); in particular the activity and selectivity were studied by using Cu/Zn/Zr catalysts, thermally treated at different times and temperatures. It was found that for the dried samples the activity is directly connected to the catalytic composition, in particular it has been noted an increased activity with the samples with higher copper content due to the presence of higher amounts of Cu not strongly interacting with other phases. Moreover the thermal treatment may tune the activity, changing the surface area and the amount of extractable copper and, mainly, according to the formation of a brass-like phase (not detectable by XRD analysis and characterized by a greater reducibility) stabilized by the amorphous ZrO2. Using the proper catalyst composition and thermal treatment it is possible to achieve GEL yields close to 99% with optimum mechanical properties and carbon balance. Finally a technical-economical analysis of different processes to produce GEL (or N-methyl pyrrolidone) led to the conclusion that the direct vapor phase hydrogenation of MA is the most advantageous technology, also providing a good example of an environmentally friendly industrial process,