Hollow Silicalite Zeolite Supported Ruthenium Phosphide Catalyzed Preparation Of Agent And Hydrodepolymerization Of Diphenyl Ether

The bond modes of oxygen-containing bridge bonds in organic macromolecules of medium and low rank coal are mainlyα–O–4,β–O–4,α–O–γand 4–O–5,among which the reactivity of ether bonds of the 4–O–5 type is very weak and it is not easy to depolymerize.Diphenyl ether is the simplest compound containing 4–O–5 ether bond.It is of great significance to study the hydrogen dissociation reaction conditions of its C–O ether bond and the use of catalysts for the utilization of low and middle coal rank resources.A silicalite-1（S-1）zeolite with hollow and morphology has been synthesized as a support for the synthesis of highly active and stable ruthenium phosphating catalysts.The catalytic performance of supported Ruthenium phosphating catalysts has been compared with that of gas-phase silica（Q-SiO₂）catalysts.The catalysts were characterized by XRD,XPS and SEM,and systematically studied the reaction path of hydrodepolymerization of diphenyl ether as the model compound of medium and low rank coal:（1）Hollow S-1 molecular sieves were prepared according to the mechanism of"dissolved silicon-recrystallization".When NaOH is added to organic alkali solution TPAOH,the original solid S-1 molecular sieve synthesized by hydrothermal crystallization method is post-treated,the electrolyte Na⁺introduced in the solution will compete with TPA⁺on the surface of the molecular sieve grain,which makes the partial surface of the grain lose the protective effect of TPA⁺.Under the action of OH^-,the skeleton silicon species of the molecular sieve grain fall off.Furthermore,the mesoporous S-1 molecular sieves were re-crystallized under the action of TPA⁺,resulting in the formation of hollow S-1 molecular sieves.The optimal experimental conditions were determined,namely,the mass ratio of C_TPA⁺/Na⁺=0.2 mixed base solution to the pre-treated solid S-1 molecular sieves at 1:50.（2）"Step heat treatment method is used to"completely in inert gas nitrogen displacement with the aid of vacuum tube after the air technical control synthesis temperature,different phosphating ruthenium catalyst was prepared and through the"first dip post-processing"strategy for the preparation of the gas phase silica（Q-SiO₂）load different phosphating ruthenium catalyst and catalytic properties of different catalysts was evaluated.Compared with Ru P-600 and Ru₂P/Q-SiO₂ catalysts,the conversion rate of hydrodepolymerization of diphenyl ether and the yield of key aromatics are improved in Ru P/Q-SiO₂,which is 97.59%and 58.18%,showing a certain pore limit effect.However,due to the calcination of carrier at high temperature during the preparation process,part of the pores collapsed,resulting in unstable catalytic performance.（3）Hollow S-1 zeolite supported Ruthenium phosphating Ru P/S-1 was prepared by"impregnation before treatment"strategy and"one-step heat treatment"method after inert nitrogen completely replaced the air and controlled the synthesis temperature by vacuum tube sealing technology.Compared with Ru P/S-1 and Ru P/Q-SiO₂,the conversion of p-diphenyl ether is more than 95%stable,but the yield of benzene is increased to 63.03%.Compared with Q-SiO₂,the hollow S-1 molecular sieve has a larger pore size distribution（80 nm）,which makes it easier for the reactants to enter the pore,and at the same time,it is easier to separate from the products in the reaction transformation process,so as to better play the confined effect of the pore.In addition,it has better hydrothermal stability and can solve the problems of Q-SiO₂ pore collapse at high temperature to a certain extent in hydrodepolymerization of diphenyl ether.（4）Diphenyl ether（DPE）with high dissociation enthalpy of C–O bond was used as a probe molecular compound to catalyze hydrodepolymerization reaction.The effects of load than,reaction temperature,hydrogen pressure and reaction time on the conversion rate and product yield of Diphenyl ether hydrodepolymerization reaction were systematically investigated,and the optimal catalyst and conditions were screened out.That is 2 wt%-Ru P/S-1 catalyst,reaction temperature 250 ^oC,0.6 MPa hydrogen,0.4 MPa nitrogen and reaction time 1 h.The possible reaction path of hydrodepolymerization of diphenyl ether was deduced.