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Non-toxic DAlCs, especially lighter dimethyl- and diethyl-carbonate, are regarded as very greenalkylating reagents, particularly when coupled with metal-exchanged Y- and X-faujasites ascatalysts. These reactions are selective, free from wastes or byproducts, and often require noadditional solvent other than the carbonate. Nonetheless, this paper demonstrates that theoperating temperature and the nature of the faujasite must be carefully chosen in order to avoidDAlC decomposition. In fact, at temperatures ranging from 150 to 240 ◦C, faujasites can promotedecarboxylation of light DAlCs to the corresponding ethers CH3OCH3 and CH3CH2OCH2CH3plus CO2. Heavier DAlCs (dipropyl- and dioctyl-carbonate) undergo a similar decompositionpathway, followed by further reactions to the corresponding alcohols (n-propanol and n-octanol)and alkenes [propylene and octene(s)]. These transformations not only consume DAlCs, but alsogive rise to dangerously ammable ethers, as well as undesirable alcohols, alkenes and CO2.Thepresent work reports an original investigation of the decarboxylation of DAlCs on faujasites withthe aim of providing operative boundaries to the experimental conditions to minimise unwanteddecomposition. The reaction is strongly affected by the nature of the catalyst: the more basiczeolites, NaX and CsY, are by far more active systems than NaY and LiY. However, solid K2CO3proves to be rather inefcient. The temperature also plays a crucial role: for example, the onset ofthe decarboxylation of DMC requires a temperature of ~30 ◦C lower than that for DEC andDPrC. Overall, awareness that certain zeolites cause decomposition of DAlCs under conditionssimilar to the ones used for DAlC-promoted alkylations allows determination of the correctexperimental boundaries for a safer and more productive use of DAlCs as alkylating agent

Decarboxylation of dialkyl carbonates to dialkyl ethers over alkali metal-exchanged faujasites