SYNGAS PRODUCTION BY CO2 REFORMING OF CH4 OVER Ni-CONTAINING XEROGEL Al2O3-ZrO2(Yb2O3) WITH POLYVINYLPYRROLIDON
The dry reforming of methane (DRM) reaction CO2 + CH4 ↔ 2CO + 2H2 shows great potential in conversion two greenhouse gases into high-purity syngas as feedstock for synthesis of higher hydrocarbons and oxygenates (Fischer-Tropsch process). Ni-based supported alumina or silica systems are good cost-effective catalysts but their practical applications restrict high temperatures of reaction that leads to catalyst deactivation by carbon deposits, sintering, phase transformation.
In our study supported 5% wt. Ni catalysts with hybrid mixed oxides support Ni/AZ(Yb)PVP (sol-gel technique with polymer addition) were prepared and tested in DRM reaction in compare with Ni/Al2O3. Catalysts were examined using BET XRD, XPS, ESR, SEM, TEM methods. and «worked» DRM tests were performed at atmospheric pressure in U-shape quartz reactor (flow rate of 20 ml/min, molar ratio CO2-CН4, gas chromatograph Crystal-2000 on line, Ar gas carrier). For only calcinated Ni/AZ(Yb)PVP samples catalytic tests were with heating-cooling 723 1023 723 K cycles. The different type of temperature hysteresis ("clockwise" for CH4 and «anti-clockwise» for CO2) with different apparent activation energy of product`s formation was found. In reducing Ni+2 in situ by DRM reaction products we can obtain active and stable to carbon formation surface for Ni catalyst with composite support. For stationary activity molar ratio H2/CO1 in heating mode, but H2/CO<1 when 5%Ni/AZ(Yb)PVP catalyst is cooling. Increasing Ni loading doesn't augment sufficiently the values of CO2 and CH4 conversion or CO, H2 yields.