Effect of preparation parameters on SrTiO3±δ catalyst for the flameless combustion of methane

Abstract

Three SrTiO 3±δ catalysts have been compared. One of them (T3) was prepared by the traditional sol-gel procedure, the other two through the flame hydrolysis (FH) technique, in the presence of either 1.5 mol excess of citric acid (sample T2) or 3 mol excess of tartaric acid (sample T1) as complexing agent in the precursor solution. All the catalysts possessed the perovskite-like structure, with some SrCO 3 as impurity. T1 was more crystalline than the other two samples and showed the most active as catalyst for the flameless combustion of methane. Isolated Ti 3+ ions were found in T3 by EPR analysis, while different EPR features were noticed with T1 and T2 and attributed to Ti 4+ /O 3 − . A high concentration of isolated Ti 3+ ions was observed with T1, accompanied by Ti 4+ /O 3 − and by other paramagnetic species, probably Ti 4+ /O − and Sr 2+ /O − , not observed with the other samples. This difference between the samples T1 and T2, likely connected with the different temperature attained during the FH preparation process with the two different complexing agents, can explain the higher oxidising activity of the T1 sample.

Effect of M ion oxidation state in Sr1−xMxTiO3±δ perovskites in methane catalytic flameless combustion

“…As shown in Fig. 8, this pattern was characterised by intensity (but not shape) comparable to that observed with pure SrTiO 3±δ prepared by the same FH procedure (Sample T2 of [3]). By contrast, this inten- sity was by far lower than that of the broad features above reported with GFH and GSG; therefore, we cannot exclude its presence also with those samples, masked by their main spectral feature.…”

“…9 reduced to about 1/10 after sample oxidation in air at 600 • C for 1 h, while its maximum moved by about 490 G towards higher field values. The only titanate sample showing this kind of spectrum was the undoped SrTiO 3±δ prepared by the sol-gel (SG) method (Sample T3 of [3]) after use as catalyst for CFC of methane (spectrum here not shown).…”

“…An innovative preparation method of this kind has been recently proposed [2], based on flame-hydrolysis (FH) of aqueous solutions of precursor salts. In a previous work [3], three samples of SrTiO 3±δ have been compared as catalysts for the CFC of methane, to investigate the influence of the different preparation parameters on their catalytic properties. It was found that the presence of paramagnetic species like M + /O − (M + = Ti 4+ or Sr 2+ ) and Ti 4+ is crucial for a good catalytic performance.…”

Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review

“…The performance does not only depend on the phase composition of the mixed oxide but also on the preparation procedure and its parameters, as these affect the crystallinity, texture and morphology of the final material [34][35][36][37][38][39]. For example, the TWC activity of La 0.7 Sr 0.3 Mn 0.7 Cu 0.3 O 3−δ prepared by complexation of nitrate salts in the presence of citric acid and ammonia is strongly affected by the acid-to-ammonia ratio employed for the synthesis [40] since it affects the polymerization of the precursor molecules.…”

Some nanograined ferrites and perovskites for catalytic combustion of acetone at low temperature

“…Nanograined ceramic materials present new opportunities for enhancing the performance of solid catalysts because of the much higher surface to bulk ratio compared to the coarse micrograined materials. Various methods have been proposed [33][34][35][36][37] to obtain catalyst materials with superior microstructure. In the present work we applied a nonconventional procedure, sol-gel coupled with self-combustion described in our previous papers [38,39].…”