Controllable Synthesis Of SAPO-34 Zeolite And Its Application In Synthesis Gas Conversion

With the increasing scarcity of petroleum resources and the increasing demand for lower olefins,the development of non-petroleum routes for the preparation of lower olefins via synthesis gas has attracted much attention.Based on the design idea of bifunctional catalyst,this paper combines ZrO2-ZnO metal oxide and SAPO-34 zeolite to produce lower olefins with high selectivity directly from synthesis gas.We mainly focused on the synthesis method of micro and nano SAPO-34 zeolite to study the effects of different synthesis methods and synthesis parameters on their size,acidity and catalytic properties.Firstly,this paper studied the effects of different templating agents on SAPO-34 zeolite by hydrothermal synthesis.The results showed that the SAPO-34 zeolite synthesized under the TEAOH template had a small size.The average length and width of SAPO-34-2TEAOH zeolite was 1.91 um,and the average thickness of it was 0.89 um.After that,we introduced the micro SAPO-34 as seed with TEAOH templete via hydro-therralmethod.Among them,SAPO-34-13%seed zeolite's average length and width was 1.19 um,the average thickness was 0.4 um.The catalytic performance showed that the CO conversion was 31.7%,and the deactivation rate of CO conversion decreased by 0.174%/h in 10-60 h,the selectivity of the low-carbon olefin remained substantially unchanged for conversion of synthesis gas over Zr02-Zn0/SAPO-34-13%seed catalyst.Based on the SAPO-34-2TEAOH zeolite,the inhibitor PEG was introduced and the nano SAPO-34 zeolite was successfully synthesized by adjusting the content of PEG and synthesis strategy.Among them,the average length and width of SAPO-34-nano-0.08PEG zeolite was 0.68 um,and the average thickness was 80 nm;the average length and width of SAPO-34-nano-Gel-0.2Si zeolite was 0.36 um,the average thickness was 79 nm.Through the results of SAPO-34-nano zeolite and SAPO-34-nano-Gel zeolite,we can found that the addition of PEG could reduce the size.However,when the synthesized SAPO-34 zeolite had reached the nanoparticle,the effect of PEG seemed to be negligible.The Zr02-ZnO/SAPO-34-nano-Gel catalyst was used for the reaction,and the CO conversion could reach 40%,and the selectivity of the lower olefins could reach?80%.Moreover,the stability for the catalytic performance was relative stable compared with that over micro SAPO-34 zeolite.