The Influence of Residual Sodium on the Catalytic Oxidation of Propane and Toluene over Co3O4 Catalysts

Abstract

A series of Co3O4 catalysts with different contents of residual sodium were prepared using a precipitation method with sodium carbonate as a precipitant and tested for the catalytic oxidation of 1000 ppm propane and toluene at a weight hourly space velocity of 40,000 mL g−1 h−1, respectively. Several techniques were used to characterize the physicochemical properties of the catalysts. Results showed that residual sodium could be partially inserted into the Co3O4 spinel lattice, inducing distortions and helping to increase the specific surface area of the Co3O4 catalysts. Meanwhile, it could negatively affect the reducibility and the oxygen mobility of the catalysts. Moreover, residual sodium had a significant influence on the catalytic activity of propane and toluene oxidation over the synthesized Co3O4 catalysts. The catalyst derived from the precursor washed three times presented the best activity for the catalytic oxidation of propane. The origin was traced to its better reducibility and higher oxygen mobility, which were responsible for the formation of active oxygen species. On the other hand, the catalyst obtained from the precursor washed two times exhibited better performance in toluene oxidation, benefitting from its more defective structure and larger specific surface area. Furthermore, the most active catalysts maintained constant performance in cycling and long-term stability tests of propane and toluene oxidation, being potentially applicable for practical applications.

The Influence of Precursor on the Preparation of CeO2 Catalysts for the Total Oxidation of the Volatile Organic Compound Propane

“…It was proposed that Na negatively impacts oxygen mobility by supressing oxygen desorption at lower temperatures, in addition to accumulating high amounts of surface carbonate species at higher temperatures. The impact of poor oxygen mobility from Na poisoning is consistent with extended studies for the oxidation of propane [55]. The impact of increased Na content on the catalyst surface did not impact the oxidation of propane in this work.…”

Comparison between hydrothermal and a facile sonochemical synthesis of Mn1‐XCeXOY, at different Ce loading, towards the catalytic oxidation of toluene

“…In order to ensure a homogeneous temperature distribution over the catalyst, the activation energy (Ea) was calculated below the 10 % of CO 2 conversion as previously reported by Chai et al [36] . The Weisz‐Prater parameter (N W‐P ) was calculated as reported by Zhu et al [37] .…”

“…It was determined that Mn 1-0.3 Ce 0.3 O y À H displayed the lowest Ea value (97.2 kJ mol À 1 ), which is similar to those reported in the literature. [30,36] The presence of oxygen vacancies (Figure 5), as well as the high O ads /O lat and low Mn 3 + /Mn 4 + ratios (Table 2) indicated a better Mn 4 + dispersion on the surface of the catalyst. This is important since Mn 4 + are considered the active sites.…”

“…Similar results have been reported by. [23,27] In order to ensure a homogeneous temperature distribution over the catalyst, the activation energy (Ea) was calculated below the 10 % of CO 2 conversion as previously reported by Chai et al [36] The Weisz-Prater parameter (N W-P ) was calculated as reported by Zhu et al [37] obtaining values around 3:16x10 À 9 which is lower than 3 indicating that the diffusion influence can be neglected in the calculation of the Ea. Figure 9 shows the Ea value for each catalyst.…”

“…In order to evaluate the Ea values as reported by Chai et al, [36] the Weisz-Prater parameter (N w-P ) was calculated as Chu et al [37] in order to determine the influence of the heat transfer or mass transport limitations. For our data the calculation of N w-P was carried out as follow:…”