Synthesis Of Mcroporous And Mesoporous Composite Molecular Sieve And Its Application On Hydroisomerization

There are several basic reaction mesoporous materials such as MCM-41,their application on the FCC,isomerization and alkylation reactions in the petrochemical industry is very broad.However,these reactions often require a strong acid catalyst,hydrothermal stability and strength,in these areas mesoporous materials showed significant deficiencies.Studies have shown that acidity and hydrothermal stability of the mesoporous composite materials will be improved,because the nano-porous zeolite material is introduced into them.Based on this,the experiment uses the Beta zeolite which is alkali-processed as the raw material to synthesis the micropores and mesopores composite zeolite.Firstly,according to conventional methods Beta zeolite is prepared.Then simply it is dissolved by NaOH.Treated zeolite Beta has roughly surface cracks.With the harsh processing conditions,more and deeper cracks are appeard.And it even causes the collapse of the cellular structure.There are some some dissolved Beta's primary,secondary and even cell structure ultrafine nano-porous structure grains in the Alkali treatment slurry.The slurry can be used as a molecular sieve precursor slurry for making microporous and mesoporous composite zeolite.Crystallizing in the condition of alkali-treated slurry and surfactant,a microporous structure containing mesoporous structure of composite materials can be made.Its main channel likes the channel of regular hexagonal structure of MCM-41,and there are microporous material on the surface of it.Different characterization methods investigated morphology and hydrothermal stability of the composite zeolite.It found that synthetic composite material has good acidity and hydrothermal stability,and diffusion properties which is similar as the mesoporous materials.It was also found that by varying the concentration of NaOH,the proportion of synthesized mesoporous structure and pore structure can be controlled.Base on the above research,this paper use n-heptane as raw materials to make hydroisomerization reactions on the Beta,alkali-treated Beta and the composite zeolite.It was found that,due to the introduction of mesoporous,it improves the reaction mass transfer rate,reduces the raw material on the catalyst reaction time,greatly inhibits the occurrence of cracking reaction.Thereby selectivity of isomerization has been greatly improved.