The Effect Of PdCl₂-CuCl₂-KOAc/AC Catalysts Preparation On DMC Synthesis

Dimethyl carbonate(DMC) is an environmentally benign building block, and the development of clean technology to synthesis DMC is achieving increasing importance. This paper study preparation of catalysts and the synthesis of dimethyl carbonate by gas-phase oxidative carbonylation of methanol on the supported solid catalyst.The influence of different factors on the catalytic performance were studied in detail. Multiple techniques including BET, XRD, XPS, SEM and TG/DTA etc were used to characterize the morphological and electronic structure of the catalysts of the reaction.Preparation strategy of catalysts was another important factor for catalytic performance. Different catalytic performance was observed by varying the impregnating. We found the presence of a synergetic effect for the active component of palladium and copper on the catalytic performance in the present bimetallic catalyst system. The activity of catalyst made by two-step impreging is better than that one-step, and the stability is improved. The appropriate amount of promoter KOAc addition helps enhancing the performance of catalysts by forming intermediate species Cu₂Cl(OH)₃ in DMC synthesis reaction. This paper introduced four different dry methods for the catalysts preparation and the heterothermic dry is the best. Choose six kinds of active carbons made of different materials, and loaded active components on them to prepare catalyst. Through comparing the activity, we found the catalyst supported by high-performance coconut shell carbon is the best. Then we use methyl chloroacetate to pretreat catalysts and research the differences between them. We pretreated the carbon by hydrogen peroxide and nitric acid separately. The oxygenic groups increased on the surface of the former so that facilitate the Pd²⁺/Pd¹⁺ and Cu²⁺/Cu¹⁺ redox processes. Consequently, reduce the activation energy of the reaction. The later is not ideal.We studied the performance of regeneration on super active carbon, and the catalytic activityof the deactived catalyst which was regenerated eight times fell to 570 g/(L-cat?h) from primary 675 g/(L-cat?h),whereas, it is better than literature. Methyl chloroacetate can be replaced by dichloromethane, which can be used as disposal and regeneration. For the material of methanol and dichloromethane, which concentration is 5%, it was found that steady-state activity can be maintained for 150h as lone as the pressure was 0.3MPa.The reaction kinetics of direct methanol oxidation and carbonylation in vapor phase for DMC (dimethyl carbonate) production, using a continuous flow fixed bed reactor, has been investigated with the supported catalyst PdCk-CuCk-KOAc/Ac. The experiments suggest that: When the feedstock space velocity above 5771.456 h'1 and the size of catalyst smaller than 285 um, the effect of internal and external diffusion can be neglected. After kinetic experiments,which are under the conditions of different temperature, pressure and consistency, we get twenty-four data. Then a power linetic model and a hyperbola model, considering both DMC and CO2 productions, were derived by linear optimization(Powell program). The results of variance and residual error show that the error was in the range of kinetic toleration,and the experiment does not have any system error. The scale-up experiment of industry can be carried out base on the model.