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Microcalorimetry and measurements of the contact angle of water were performed to investigate the hydrophilic/hydrophobic properties of silica surfaces modified with metal oxides and polydimethylsiloxane (PDMS) at 20-500°C. Fumed silicas whose surfaces contained grafted oxygen compounds of metals were used as adsorbents, with VOCl 3 , CrO 2 Cl 2 , TiCl 4 , SnCl 4 , AlCl 3 and Zn(acac) 2 vapours being applied as modifiers. It was found that the hydrophobic coating of silicas modified with metal oxides and PDMS (8-40 wt%) was stable over the temperature range 100-350°C. With a titania coating, the hydrophobic properties were retained at temperatures up to 500°C for an adsorbed polymer content of 20-40 wt%.

Here, we report, for the first time, on the catalytic hydrogenation of CO2 to methane at atmospheric pressure. For the preparation of hydrogenation catalysts based on Ni and Fe metals, a convenient method is developed. According to this method, low-temperature reduction of the co-precipitated Ni and Fe oxides with hydrogen gives the effective and selective bimetallic Ni[Formula: see text]Fe[Formula: see text], Ni[Formula: see text]Fe[Formula: see text] and Ni[Formula: see text]Fe[Formula: see text] catalysts. At the temperature range of 300–400[Formula: see text]C, they exhibit a high efficiency of CH4 production with respect to monometallic Ni and Fe catalysts. The results imply a synergistic effect between Ni and Fe which caused the superior activity of the Ni[Formula: see text]Fe[Formula: see text] catalyst conversing [Formula: see text]% of CO2 into CH4 at 350[Formula: see text]C. To adapt the Ni–Fe catalysts in the industry, the effect of two different carriers on the efficiency of the alumina-supported Ni[Formula: see text]Fe[Formula: see text] catalyst was investigated. It is found that the Ni[Formula: see text]Fe[Formula: see text]/[Formula: see text]-Al2O3 catalyst effectively conversed CO2 giving 100% methane yield already at 275[Formula: see text]C.