A highly pure mixture of carbon and silica was obtained on pyrolysis rice husk leached with acid at high temperature in a nonoxidizing atmosphere. The product was suitable for use as a starting material in the the manufacture of silicon nitride powder. The effect of treatment including the kind and concentration of acid and the pyrolysis temperature on the constituents of the specimen was presented. Kinetic tests on pyrolysis of rice husk in a nitrogen atmosphere were carried out with a thermal gravimetric analysis (TGA) technique at heating rates 2, 3, and 5 K/min. The results indicated that thermal degradation of rice husk consisted of two distinct pyrolysis stages. The corresponding kinetic parameters including the activation energy were determined. A reasonable pyrolysis mechanism was proposed, which agreed satisfactorily with the experimental results.

No abstract

No abstract

No abstract

The rice husk ash supported nickel catalysts was prepared by deposition−precipitation and used for hydrogenation of CO2 from a H2/CO2 (4/1) mixture. The reaction exhibited high selectivity (80%) for CH4 formation when carried out at 673−873 K with the supported nickel. The effects of nickel loading, deposition−precipitation time, calcination, and reduction of temperature on the catalytic performance were also extensively studied. These results show that nickel loading increases with an increase in the deposition−precipitation time up to 24 h, while metal dispersion increases with a decrease in nickel loading. The conversion of CO2 and the yield of CH4 were found to be independent of the calcination temperature and time. Furthermore, the conversion and yield increase with an increasing reaction temperature up to 723 K, but decrease with a further increase in the reaction temperature. Moreover, rice husk ash has been found to be preferable over silica gel as a catalyst support as revealed by the temperature-programmed desorption techniques and the reaction test.