Abstract
The physicochemical properties and catalytic activity of pure and sulfated titanium oxide (TiO2 and ) is described in this work. Titanium hydroxide synthesized by the sol-gel method was impregnated with a 1 N H2SO4 solution, varying amount of sulfate ions () in the range from 10 to 20 wt%. Pure and modified hydroxides were calcined at 500°C for 3 h and then characterized by TGA-DTG, XRD, BET, FT-IR, potentiometric titration with n-butylamine and 2-propanol dehydration. Catalytic activity of materials was tested in the n-hexane isomerization at 350°C. The results showed that TiO2 and mainly developed anatase phase. All have acceptable specific surface area (95-105 m2/g). Potentiometric titration with n-butylamine revealed that showed higher acidity (430-530 mV) than compared to pure TiO2 (﹣15 mV), indicating that this oxide only has weak acidity. The results showed good relationship between acidity determined by potentiometric titration with n-butylamine and the catalytic activity evaluated by 2-propanol dehydration and n-hexane isomerization. Titanium oxide with 20 wt% ofions was the material that demonstrated the highest catalytic activity for both reactions.
Highlights
Solid acid catalysts have assumed a great importance due to their huge application potential in chemical industry, in the oil refining industry [1,2,3,4]
The results showed good relationship between acidity determined by potentiometric titration with n-butylamine and the catalytic activity evaluated by 2-propanol dehydration and n-hexane isomerization
Four different weight loss stages were identified during thermal analysis of the as-prepared titanium oxide and sulfated titanium oxide materials (Figures 2 and 3)
Summary
Solid acid catalysts have assumed a great importance due to their huge application potential in chemical industry, in the oil refining industry [1,2,3,4]. The substitution of oxygen atoms in the titania lattice with sulfur and other anionic species [18] are reported to show photocatalytic activity enhancement in visible light [19,20] due to the existence of oxygen vacancies, greater surface area [21,22,23,24,25], and larger fraction of the anatase phase These physicochemical properties can be controlled from the synthesis process [26]. In the search for new solid acid catalysts with improved properties, this work focuses on the synthesis and characterization of a sulfated titanium oxide by sol-gel method, and presents a preliminary evaluation of its catalytic properties for the n-hexane isomerization reaction
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