Preparation And MTA Reaction Performance Study Of B-oriented [Zn,Al]HZSM-5/Coal Gangue Materials With Multiporous

As an important way to prepare high quality aromatics by non-petroleum route,Methanol conversion to aromatics?MTA?has attracted the attention of researchers in recent years.Based on the advantages of adsorption and diffusion of ZSM-5 zeolite in the b-oriented,this paper proposed a method of secondary synthesis to prepare the b-oriented ZSM-5 zeolite material on the surface of porous gangue substrate.After doping zinc and aluminum sources in secondary synthetic solution,the controllable preparation of porous materials with b-oriented[Zn,Al]HZSM-5/coal gangue porous material was studied.Finally,porous materials with b-oriented[Zn,Al]HZSM-5/coal gangue porous material prepared under the optimum synthesis conditions were applied to MTA reaction to explore their catalytic performance.Firstly,this paper studied the controllable adjustment of structure of coal gangue substrate.During the preparation of porous coal gangue,investigated the effect of different content of pore forming agent?NH₄?₂CO₃ on the structure of coal gangue substrate.The experimental results show that the pore size of the substrate increases about three times after adding pore forming agent to coal gangue,and the more pore forming agent content,the larger the pore size of the matrix.When the content of pore forming agent is 15%,the pore size,apparent porosity and compressive performance of porous gangue base are the best.The addition of pore forming agent has little effect on the phase composition of coal gangue substrate.Secondly,After the seed layer was grown on the porous coal gangue substrate by hydrothermal crystallization,the effects of Al source,Si/Al ratio and template dosage on the preparation of b-oriented Al-HZSM-5/coal gangue porous material were studied by means of secondary growth method.It was found that higher b-axis oriented Al-HZSM-5/gangue porous materials could be prepared by using sodium met aluminate as aluminum source,the ratio of secondary synthetic solution was Si/Al ratio of 100,template to silica ratio of 0.32.The results also show that the morphology of the molecular sieves prepared by doping Al in the synthesizing solution is typical hexagonal and the synthesizing solution needs some alkalinity.However,the excessive alkalinity of the synthesizing solution will inhibit the formation of the molecular sieves.The sample Si/Al ratio is about half of that in the synthesizing solution,the doped aluminium source successfully enters the inner part of the molecular sieve,providing certain acidity for the catalyst material.Thirdly,based on doping aluminum source,zinc source doped into the secondary synthetic solution.The effects of zinc source type,ratio of silicon to zinc and amount of alkali on the preparation of b-oriented[Zn,Al]HZSM-5/coal gangue porous material were investigated.The experimental results show that when zinc nitrate is used as zinc source in the secondary synthesis solution,the zeolite film is compact and has high b orientation and crystallinity when the Si/Zn ratio of 150,sodium hydroxide to zinc nitrate ratio of 9.Experiments also found that the addition of zinc source not only changed the morphology of zeolite from hexagonal to microspheres shape,but also reduced the crystallinity of zeolite as a whole.The ratio of Si/Zn in the samples was about half of the ratio of Si/Zn added into the secondary synthesis solution,that is,zinc successfully entered the framework of zeolite and provided a certain metal center for catalyst materials.Finally,the catalytic performances of conventional ZSM-5 catalyst,b-oriented[Zn,Al]/HZSM-5 powder?Secondary growth liquid crystallization?and b-oriented Zn/Al-HZSM-5powder,b-oriented[Zn,Al]/HZSM-5 membrane and b-oriented Zn/Al-HZSM-5 membrane in MTA reaction were compared.The results showed that the methanol conversion of the five catalysts increased first and then decreased with the increase of the catalytic temperature,and reached the highest level at 480 ^oC.The methanol conversion and aromatics yield of the five catalysts decreased with the increase of reaction time at 480 ^oC.Compared with conventional ZSM-5 catalyst,b-oriented membrane material and b-oriented powder material have higher activity,longer life and more carbon deposition resistance in MTA reaction.Zinc-doped b-oriented[Zn,Al]/HZSM-5 films and b-oriented[Zn,Al]/HZSM-5 powder catalysts exhibit higher activity,longer life and carbon deposition resistance than zinc-impregnated catalysts.