Modified Zeolites in Methanol to Hydrocarbons Transformation.

The work is devoted to the modification of H-ZSM-5 samples with sodium hydroxide and oxalic acid to provide the formation of the mesoporous structure of the zeolite and to obtain optimal Si/Al ratio. Moreover, zeolite active sites were modified with Co, Ni, Fe in order to decrease polyaromatic substances formation during methanol transformation into hydrocarbons. The testing of the samples was performed at 350 °C in a flow reactor, the methanol feed rate was maintained at 0.16 g(methanol)/(g(Cat)*h). Dimethyl ether transformation rate into hydrocarbons was found to be 0.055-0.1 kg(DME)/(kg(Cat)*h) for investigated catalysts. Alkali treatment of H-ZSM-5 samples results in the formation of a mesoporous structure with a mean pore diameter of 5 nm. Formation of additional mesopores results in some increase of dimethyl ether to hydrocarbons transformation rate up to 0.09 kg(DME)/(kg(Cat)*h). Zeolite treatment with oxalic acid results in decreasing of Si/Al ratio from 0.76 to 0.41 that case some decrease of dimethyl ether transformation rate from 0.07 kg(DME)/(kg(Cat)*h) to 0.05 kg(DME)/(kg(Cat)*h), however considerable decrease of polyaromatic hydrocarbons concentration in reaction media was achieved for sample with lowest Si/Al ratio. Modification of H-ZSM-5 with Co, Fe, Ni results in some increase of dimethyl ether transformation rate up to 0.07-0.1 kg(DME)/(kg(Cat)*h) and a considerable decrease of polyaromatic hydrocarbons concentration in reaction media due to active sites modification. The ZSM-5-Ni-0.001M sample showed highest activity 0.1 kg(DME)/(kg(Cat)*h). [ABSTRACT FROM AUTHOR]