Synthesis And Studies Of Zirconium Based Oxide/Zeolite Bifunctional Catalyst For Direct Conversion Of Syngas Into Aromatics

Aromatic hydrocarbons are one of the most important bulk chemicals and are currently mainly derived from petroleum catalytic reforming.With the depletion of petroleum resources,the use of non-petroleum carbon resource to produce aromatics from syngas is considered to be one of the feasible ways.Based on the idea of reaction coupling strategy,this thesis designs and synthesizes zirconium-based oxide/zeolite-bifunctional catalyst,and studies its catalytic performance in the direct synthesis of aromatics from syngas,and further reveals the structure-activity relationship of the catalyst.We firstly studied the oxide composition by testing different metal additives on Zr-Zn oxide and found that of Zr-Zn-Fe oxide was better for the synthesis of aromatics from syngas.The addition of Fe could increase the activity and aromatization ability of the catalyst.Then,the ratio between the metal components in the Zr-Zn-Fe oxide was futher optimized.It was found that the increase in the content of Zn or Fe was favorable for the hydrogenation of CO but was not conductive to the formation of aromatics,and the appropriate ratio of Zr/Zn/Fe was 50:1.1:0.1.We further studied the effect of silica-alumina ratio,F treatment and silanization treatment on H-ZSM-5 zeolite on the catalytic performance.The results showed that the increase in acidity of zeolite was beneficial to the CO hydrogenation and inhibition the formation of heavier hydrocarbon products.F treatment could increase the specific surface area and pore volume of the zeolite,and thus improve the selectivity of aromatics.The silanization treatment could passivate the external acid sites of the zeolite,suppress the formation of heavier aromatics,improve the selectivity of BTX and F treatment followed by silanization treatment combines the advantages of both,which is beneficial for the formation of aromatics and BTX.This thesis further investigated the reaction conditions and the matching of oxides and zeolite.and found that the increase of pressure is beneficial to the activity and aromatization ability of the catalyst.The increase in reaction temperature is beneficial for syngas to methanol,and the decrease in reaction temperature is beneficial for the further aromatization of methanol.The increase in mass ratio of oxide to zeolite in the catalyst is beneficial to the CO hydrogenation without favoring the formation of aromatics,thereby the suitable conditions for syngas to aromatics of 5 MPa,400? and 1:2 of mass ratio to oxide and zeolite were determined.The Zr-Zn-Fe(50:1.1:0.1)/H-ZSM-5(120)-F-0.36M-CLD3 bifunctional catalyst behaves excellent performance of direct conversion of syngas into aromatics,and the CO conversion could reach 16.7%,aromatic selectivity and BTX selectivity were 66.5%and 33.8%,respectively,while the CH4 selectivity was only 1.7%,and the stability was also good during reaction.