Effects of Al,Ti or Zr modification on performances of embedded Ni@SiO2 catalysts for partial oxidation of methane to syngas
The embedded catalysts can effectively prevent the sintering behavior,and realize the high activity in partial oxidation of methane(POM)reaction.The embedded Ni@SiO2 catalysts were prepared by Stöber method,and the Al,Ti or Zr were used to modify them.Various characterizations,such as X-ray diffraction(XRD),transmission electron microscope(TEM)and N2 adsorption/desorption,were employed to the characterizations of crystalline phase structures,morphologies and texture parameters of catalysts.The effects of modification of catalysts on the catalytic POM performance were further investigated under the feed gases compositions of V(CH4)∶V(O2)∶V(N2)of 2∶1∶3,gas flow rate of 60 mL/min,pressure of 0.1 MPa,space velocity of 7.2 L/(g·h)and reaction time of 22 h.The results show that compared with Ni@SiO2 catalyst,the Ni@Al-SiO2 catalyst can promote the activation of methane and its catalytic performance is improved.However,the Ni@Ti-SiO2 and Ni@Zr-SiO2 catalysts show the decreased catalytic performances because of the obstruction of active sites.At 700 ℃,the CH4 conversation rates of Ni@Al-SiO2 and Ni@SiO2 are 86％and 80％,the CO selectivities are both about 90％,and the H2 selectivities are 93％and 88％,respectively.However,compared with Ni@SiO2catalyst,the CH4 conversion rates,CO selectivities and H2 selectivities of Ni@Ti-SiO2 and Ni@Zr-SiO2 are significantly reduced.It reveals that the catalyst deactivation can be mainly ascribed to the loss of active sites and carbon deposit.But the active sites are not completely covered by deposited carbon,and the catalyst still maintain robust catalytic POM performance.
Ni@SiO2 catalystsembedded structurecatalyst modificationpartial oxidation of methanecarbon deposit
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