Fumed oxides modified due to pyrolysis of cyclohexene

Mixed oxides such as fumed X/silica (X=Al2O3 (AS), TiO2 (TS)) and CVD-TiO2/fumed silica, initial and covered by carbon deposit formed on cyclohexene pyrolysis, were characterized by means of carbonization kinetics, nitrogen adsorption–desorption, water adsorption, and electrophoresis methods. Catalytic capability of AS (per gram of the adsorbent) in cyclohexene pyrolysis (973 K for 4 h) is greater at a low concentration of alumina, but for fumed TS, it is maximal at large CTiO2. Concentration of pyrocarbon formed on AS or TS is 2–4 times larger than that on silica under the same pyrolysis conditions, and fumed TS can stronger catalyze pyrolysis than CVD-titania/silica does. A marked impact of the nature of X/SiO2 on cyclohexene pyrolysis results in variations of the structural, adsorptive, and electrokinetic properties of C/X/SiO2. Alterations in the pore size distributions (main maxima at Rp between 0.5 and 7 nm) can be due to the availability of various channels between primary particles (5–50 nm) packed in relatively dense aggregates and between aggregates in more loose agglomerates of aggregates differently filled by grafted pyrocarbon. The dependencies of ζ potential of C/X/SiO2 particles on pH are closer to that of C/SiO2 than X/SiO2, i.e. carbon deposit covers mainly the X/SiO2 interface and X phase possessing catalytic activity in cyclohexene pyrolysis.