Zeolites catalysts, hydrogen production from water

Metal carbonyl dusters (e.g. of Rh) can be used as precursors to form catalysts for reactions involving CO, induding the water gas shift reaction, alkene hy o-formylation, and CO hydrogenation. Although the catalysts exhibit some unusual selectivities, such as in the hydrogenation of CO to give non Schulz-Flory distributions in their hydrocarbon products, they are not highly active relative to some of the more conventional catalysts. The spedes in the zeolites that are formed from the cluster precursors and which are the actual catalytically active spedes have not yet been eluddated. 

Supported liquid-phase (water-ethylene glycol) catalyst containing Pd complexes was used for hydrogenation of stilbene in toluene [57]. It was found that zeolite CaY acted, in the presence of Bronsted acid sites, either as a reagent for reducing stilbenes to 1,2-diarylethanes or as a catalyst for isomerizing cis-stilbenes to the more stable trans form [58]. In contrast, the Lewis add sites generated by the activation process yield radical cations from stilbenes, but these did not yield any stable products. 

The CL monomer is obtained by the traditional Baeyer-Villiger reaction, starting from cyclohexanone as substrate. However, this synthetic route is not environmentally friendly, which has involved the development of two greener routes (1) use of a peroxycarboxylic acid (such as 3-chloroperbenzoic acid or peracetic acid) in dichloromethane at 40 ° C, and (2) use of hydrogen peroxide as oxidizer and zeolite/tin catalysis.The second process is considered the greenest because the main by-product is exclusively water and the tin-impregnated zeolite is an environmentally friendly catalyst. Nowadays, CL is produced by several manufacturers like BASF (USA), Perstorp (UK), and Daicel Chemical Industries Ltd. (Japan). 

---