Study On The Catalytic Synthesis Of Diethyl Carbonate From Carbon Monoxide And Ethyl Nitrite

Diethyl carbonate (DEC) is a versatile compound that represents an attractiveeco-friendly alternative to both ethyl halides and phosgene for ethylation andcarbonylation processes, respectively. In recent years, diethyl carbonate is found tosubstitute for methyl tert-butyl ether (MTBE), which is used as an oxygen-containingfuel additive. In this paper, supported Pd catalysts and the reaction conditions for thevapor phase synthesis of DEC from carbon monoxide and ethyl nitrite were studied ina continuous flow micro fixed-bed reactor at atmospheric pressure.The products in diethyl carbonate synthesis from CO and ethyl nitrite in thegaseous phase at atmospheric pressure were analyzed by gas chromatography-massspectrometry. Diethyl carbonate, ethanol, ethyl chloroformate, ethyl acetate,1,1-diethoxyethane were separated and qualitatively analyzed respectively, andexplained the formation of the by-products from the reaction mechanism.Supported Pd catalysts for DEC synthesis in vapor phase were investigated atatmospheric pressure. PdCl2-CuCl2/AC binary catalyst exhibited excellent catalyticperformance for DEC production, the STY of DEC was 490 g/(lcat?h). The catalyticactivity of the catalyst can be effectively improved by chemical pretreatment with H2,the optimum Pd/Cu mole ratio is 1:2, the suitable Pd-loading was 2.5 wt.%, someadditives (such as CeCl3 and PrCl3) are benefit for the DEC yield and selectivity.PdCl2 and CuCl2 dissolved in methanol were benefit for the catalytic activity andcatalysts made by drip dipping method had better catalytic activity.Influences of various reaction parameters on the DEC yield and selectivity weretested. The optimum reaction temperature lies in 378~388 K and the suitable gashourly space velocity (GHSV) range is 2500~3000 hr-1 considering both factors ofDEC production and CO conversion. An optimum CO/C2H5ONO mole ratio existsfor catalytic activity, which is about 1/1. The stability of PdCl2-CuCl2/AC catalyst andPdCl2-CuCl2-CeCl3/AC catalyst was also investigated.The morphological analysis by X-ray diffraction and XPS showed that thechange of Palladium species from high oxidation state to low oxidation state and theloss of chlorine were correlative to the deactivation behavior of PdCl2-CuCl2/ACcatalyst. During the process of catalysts deactivation, the active elements in thesurface of catalysts were conglomerated.