Methanol To Gasoline Reaction Over Modified ZSM-5 And ZSM-11

Methanol to gasoline technology uses methanol,which comes from numerous coal resource,as raw materials.The obtained gasoline with no sulfur,no chlorine and low nitrogen oxide,thus it is friendly to environment.Catalyst is the key factor of MTG technology.ZSM-11 and ZSM-5 have been the most studied catalysts.Developing catalysts that have high catalytic activity,long catalytic lifetime and high gasoline yield is the main task of MTG technology.To solve these problems,this article conducted the following researches.ZSM-5 with heterogeneous aluminum distribution was applied as parent zeolite,using NaOH,treated the ZSM-5 zeolite.The results showed that after NaOH treatment,mesoporous were introduced into zeolite that led to full conversion of methanol,high selectivity of toluene,xylene and trimethylbenzene,and catalytic lifetime extended to 396 h from 228 h.Parent ZSM-11 zeolite and nickel doped,steam treatment,and steam and nickel co-modified ZSM-11 zeolite catalysts were tested in the methanol to gasoline reaction.Slight catalytic stability improvement was achieved over single modified zeolites,while,the co-modification catalysts(2Ni-HT500-ZSM-11)gained excellent lifespan with 708 h.XRD,NH3-TPD,H2-TPR,XPS et al.characterizations were used to gain detailed information of catalysts.The results showed reduction of acid sites might contribute to the slower deactivation rate,and the strong interaction between NiO and steam treating ZSM-11 may decelerate the coke formation in that less ethylene was produced to further polymerize to larger molecules that block pores.Also,The effect of nickel content(0.5%-2%))of co-modified catalysts were investigated,and the result showed decrease of nickel amounts(< 2%)leaded to less methane and lower lifetime.6Si-2Ni-HT500-ZSM-11 were tested under atmospheric pressure,0.2MPa and 0.5MPa to study changes of catalytic lifetime and yield of gasoline by pressure impact.The results showed that catalytic longvity were 31,17.5,16.5days,respectively.While,yield of gasoline were 23%,33%,36%.The TG-DTA and GC-MS etc were adopted to obtain catalyst information.It reveals that raising reaction pressure leads to retention time of the feed extended,secondary reaction deeper.Thus,the yield of gasoline was improved.On the other hand,raising reaction pressure,the reaction tends to produce macromolecules like diphenyl rings species that blocks zeolite pores so that makes the catalyst deactivation rapidly.Also the effect of WHSV(Weight Hourly Space Velocity)on catalyst lifetime was investigated.The results showed that doubling WHSV got the catalyst lifespan halved and the methanol conversion capacity on catalyst decreased.