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To meet the increasing demand for efficient and durable catalysts for exhaust aftertreatment system, a mesoporous SiO2‐encapsulated nano‐Co3O4 catalyst was synthesized, which possesses a unique pitaya‐like structure with high CO oxidation activity and thermal stability. Though the silica matrix is inert, the encapsulated Co3O4 exhibits increased oxygen storage capacity, enhanced CO2 desorption behavior and high lattice oxygen reactivity. Additionally, the SiO2‐encapsulated Co3O4 catalyst can be effectively regenerated rather than the supported Co3O4/SiO2 and pure Co3O4. The kinetic results demonstrate that the L−H mechanism is followed over the pure Co3O4 nanoparticles catalyst, while the CO oxidation over the silica‐supported Co3O4 catalysts obey to both L−H and MVK mechanism. The encapsulation structure of the as‐prepared catalyst can effectively restrain the aggregation of Co3O4 during high temperature operations and improves the utilization efficiency of cobalt resources, as well, which would be suitable for practical applications. [ABSTRACT FROM AUTHOR]

• The active oxygen on Pd/Sn 1−x Ce x O 2 (Ce-rich) is mainly lattice oxygen. • The active oxygen on Pd/Sn 1−x Ce x O 2 (Sn-rich) is mainly chemisorbed oxygen. • The active oxygen on Sn-rich oxide has better mobility than that on Ce-rich oxide. The properties of Sn-Ce solid solution have a significant effect on the CO oxidation performance of the Pd/Sn 1-x Ce x O 2 catalyst. Herein, we compared the effects of Sn-rich and Ce-rich supports on the catalytic performance of the Pd/Sn 1-x Ce x O 2 catalysts. Our results show that the active oxygen species on the Ce-rich and Sn-rich supports are mainly the lattice oxygen species and the chemisorbed oxygen species, respectively. Although the active oxygen species on the Ce-rich supports have higher intrinsic activity, the active oxygen species on the Sn-rich supports have better mobility. It leads to an interesting phenomenon that the change trend of the activity of the Pd/Sn 1-x Ce x O 2 catalysts with temperature is consistent with that of their supports. Compared with the Ce-rich supports and the corresponding supported Pd catalysts, the catalytic activity of the Sn-rich supports and the corresponding supported Pd catalysts increased faster with the increase of temperature. [ABSTRACT FROM AUTHOR]

Improving the reactant mass transfer on the catalyst surface is a feasible approach to fabricate a robust solid catalyst for efficiently promoting the biomass macromolecules-involving reactions, specifically for biodiesel production by using non-edible acidic oils as feedstocks. In this premise, to reduce the mass transfer resistance, the hierarchical porous SOM-ZIF-8 was firstly synthesized using polystyrene spheres (PS) as templates and then employed as catalyst supports for loading of Keplerate-type polyoxomolybdates {Mo 132 } to prepare a novel {Mo 132 }@SOM-ZIF-8 solid acid catalyst. The catalyst characterization results revealed that the active species of {Mo 132 } clusters were well-dispersed on the SOM-ZIF-8 support and the primary framework of the SOM-ZIF-8 support remained nearly unaltered after the preparation processes. This prepared catalyst featured three-dimensional ordered hierarchical porous structure and dual Bronsted-Lewis acid sites, with a large surface area of 736.26 m2/g and high acidity of 903 μmol/g, presenting high activities for concurrent triglyceride transesterification and free fatty acids (FFAs) esterification. With the acidic soybean oils as feedstocks, 93.9 % of oil conversion and full FFA conversion to biodiesel were achieved over this solid catalyst at 130 °C for 8 h with a catalyst loading of 2 wt%, thus imparting the great potential for a one-pot efficient biodiesel manufacture from the acidic oils to comply with the demand of green and clean production. The synergy between the hierarchical porous structure and the strong acidity emerged, thus boosting the catalytic performance of this solid catalyst for the heterogeneous biodiesel production. The good FFA and moisture-resistance capacity was shown for this catalyst even in the case of moisture content of 3 % and FFA content of 25 %. Further, this catalyst showed excellent reusability without significantly losing its catalytic performance even after five runs, providing a deeper insight into constructing efficient solid catalysts with hierarchical porous structure that are utilized for cost-effective production of biodiesel from the non-edible acidic oils. [Display omitted] [ABSTRACT FROM AUTHOR]

The exploration of efficient and recyclable catalysts is highly desirable for catalytic biodiesel manufacture from low-grade acidic oils, in response to the demand of clean production and environmental concerns. For this aim, phosphotungstic acid (HPW) was firstly modified by tin metal, and then embedded on ZIF-8 metal-organic formworks (MOFs) to synthesize the SnPW@ZIF-8 catalyst. Catalyst characterization results revealed that the active species of Sn-doped HPW with Keggin-type anion structure were well-dispersed on the ZIF-8 support, and this catalyst featured high surface area with dual Brönsted-Lewis acid sites, posing enhanced catalytic performances to the oil transesterification and esterification of free fatty acids (FFAs) presented in oils. By applying this catalyst, 92.8 % of oil conversion and 97.4 % of FFAs conversion were concurrently achieved under the optimized conditions, rendering one-pot conversion of low-grade acidic oils to biodiesel and minimizing the complex and tedious separation processes. Moreover, the higher water and FFA-resistance capacity was shown for this catalyst, imparting its more suitable for the efficient biodiesel production particularly with the acidic oils as feedstocks. Further, this catalyst could still remained high catalytic efficiency after five cycle reuses due to the strong interactions of the SnPW with the imidazole groups in the ZIF-8, making it to have the potential of cost-effective and efficient production of biodiesel from the low-grade acidic oils. [Display omitted] • SnPW@ZIF-8 solid catalyst with duai Brönsted-Lewis acid site were prepared. • This catalyst was effective for one-pot biodiesel production from low-grade oils. • Oil transesterification and FFA esterification can be achieved simultaneously. • This catalyst has good recyclability and high resistance to acid and moisture. [ABSTRACT FROM AUTHOR]

For the purpose of fabricating an efficient solid acid catalyst for biodiesel production from low-grade acidic oils, bimetallic silica mesoporous composites with different Zr/Al molar ratios were initially synthesized via a facile one-step hydrothermal method, and then sulfated with sulfuric acid at different concentrations to get a series of sulfated Zr x -Al y -KIT-6 catalysts (denoted as SZA-K, where x/y represents the molar ratio of Zr to Al). The sulfated bimetallic solid catalysts were fully characterized by using XRD, FT-IR, TEM, SEM, EDS, NH 3 -TPD, and nitrogen porosimetry measurements. Results showed that the remarkable amount of acidic sites in the catalysts was derived from the Zr and Al incorporation and further sulfation, and specifically, the Zr4+ and Al3+ could afford abundant weak acid sites while the inductive effect of SO 4 2− species greatly influences the acidic strength of this solid catalyst. In combination with the enhancement in mass transfer resulting from the inherent interconnected mesoporous structure, the SZA-K catalyst could facilitate the transesterification reaction to take place efficiently. The sulfated Zr 5 –Al 1 -KIT-6 catalyst (Zr/Al molar ratio of 5/1, treated using 0.75 mol/L sulfuric acid for 12 h) exhibited enhanced acid strength with larger number of acidic sites (7.81 mmol/g), resulting in a high catalytic performance to the oil transesterification reaction. An oil conversion of 96.3% was attained for the transesterification reaction performed at 120 °C for 7 h by using a methanol/oil molar ratio of 20:1 and a catalyst dosage of 6 wt%. Further, this solid catalyst exhibited better acid and water-resistance capacity with above 80% of oil conversion even with 10% of free fatty acid (FFA) and 2% of moisture present in the low-grade acidic oils. Meanwhile, the good reusability was shown for this catalyst with 80.1% conversion even after reusing for three cycles. The good stability of the solid catalyst was resulted from the strong interactions between the acidic species and the bimetallic composite support. Bimetallic Zr x -Al y -KIT-6 modified with sulfate as acidic catalyst for biodiesel production from low-grade acidic oils. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The BaFeO3−x perovskite catalyst was prepared by sol–gel method for NO x storage under lean-burn conditions. During the catalyst precursor calcination, a series of complex solid reactions happened, and the BaCO3, formed during citric acid combustion, played a key role to react with the spinel species achieving the aimed perovskite. On the Ba–Fe–750F catalyst, the perovskite phase and the small amount of spinel phase were evidenced by XRD, and some well dispersed carbonate was also detected by FT-IR. Under lean-burn conditions, the NO x was easily stored on the Ba–Fe–750F catalyst, and its optimized NO x storage capacity (NSC), i.e. 333.5μmolg−1, was obtained at 400°C. At above 400°C, the stored nitrate became unstable and decomposed, resulting in the sharp decrease of NSC. Two kinds of the NO x storage sites were identified by in situ DRIFTS experiments that the carbonate remaining on the catalyst could transform to monodentate nitrate, and the A site Ba in the perovskite structure could directly bind with NO x to form N-bounded nitrate. This BaFeO3−x perovskite catalyst was a potential NO x storage material with noble metal free. [ABSTRACT FROM AUTHOR]