Agolu Rangaswamy

An efficient noble metal-free Ce–Sm/SiO2 nano-oxide catalyst for oxidation of benzylamines under ecofriendly conditions

A nanosized Ce–Sm/SiO2 catalyst was found to show an outstanding performance in the oxidation of benzylamines into valuable dibenzylimine products with almost 100% selectivity with O2 as the green oxidant under solvent-free conditions, which is attributed to the presence of abundant strong acidic sites, enhanced oxygen vacancy concentration, and superior BET surface area.

Rare earth metal doped CeO2-based catalytic materials for diesel soot oxidation at lower temperatures

In this work, the influence of trivalent rare-earth dopants (Sm and La) on the structure-activity properties of CeO2 was thoroughly studied for diesel soot oxidation. For this, an optimized 40% of Sm and La was incorporated into the CeO2 using a facile coprecipitation method from ultra-high dilute aqueous solutions. A systematic physicochemical characterization was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), Brumauer-Emmett-teller method (BET) surface area, X-ray photoelectron spectroscopy (XPS), Raman, and H2-temperature programmed reduction (TPR) techniques. The soot oxidation efficiency of the catalysts was investigated using a thermogravimetric method. The XRD results suggested the formation of nanocrystalline single phase CeO2-Sm2O3 and CeO2-La2O3 solid solutions. The Sm- and La-doped CeO2 materials exhibited smaller crystallite size and higher BET surface area compared with the pure CeO2. Owing to the difference in the oxidation states of the dopants (Sm3+ and La3+) and the Ce4+, a number of oxygen vacancies were generated in CeO2-Sm2O3 and CeO2-La2O3 samples. The H2-TPR studies evidenced the improved reducible nature of the CeO2-Sm2O3 and CeO2-La2O3 samples compared with the CeO2. It was found that the addition of Sm and La to the CeO2 outstandingly enhanced its catalytic efficiency for the oxidation of diesel soot. The observed 50% soot conversion temperatures for the CeO2-Sm2O3, CeO2-La2O3 and CeO2 were ∼790, 843 and 864 K (loose contact), respectively, and similar activity order was also found under the tight contact condition. The high soot oxidation efficacy of the CeO2-Sm2O3 sample was attributed to numerous catalytically favourable properties, like smaller crystallite size, larger surface area, abundant oxygen vacancies, and superior reducible nature.

β-Cyclodextrin supported MoO3–CeO2 nanocomposite material as an efficient heterogeneous catalyst for degradation of phenol

With the aim of efficiently degrading organic pollutants through an easily operated procedure, a series of MoO3–CeO2 and β-cyclodextrin supported MoO3–CeO2 nano-composite materials were synthesized by using a co-precipitation method. A surfactant such as Cetyl Trimethyl Ammonium Bromide (CTAB) was used during the synthesis of this nano-composite material. These prepared catalysts are thoroughly characterized by various techniques such as XRD, BET, FT-IR, pyridine adsorbed FT-IR, Raman spectroscopy, SEM and TEM. The XRD study results suggested the formation of nanocrystalline materials which is also clearly observed from the SEM and TEM analysis. Raman measurements disclosed the presence of oxygen vacancies and lattice defects in all synthesized nano-composite samples. The catalytic activities of the synthesized materials were successfully tested for the degradation of phenol by using hydrogen peroxide at room temperature. It is surprising that the phenol degradation efficiency of the β-cyclodextrin supported MoO3–CeO2 nano-composite material is exhibited higher than that of other materials, which has been mainly attributed to the promoting effect of β-cyclodextrin. The degradation reaction is carried out at room temperature with continuous stirring and without light irradiation. Therefore, this degradation reaction is different from conventional heterogeneous catalysis or photocatalysis, in which the pollutants cannot be degraded completely, but it may transform from one phase to another phase. The gradual decrease in COD value shows the degradation of phenol that leads to the conversion of organic compounds into harmless gaseous CO2 and inorganic ions. Thus, this reported phenol degradation reaction is a quite promising green technology, which could be widely applied in practice.

Crucial role of titanium dioxide support in soot oxidation catalysis of manganese doped ceria

The influence of an anatase-TiO2 support on the diesel soot oxidation catalytic activity of manganese doped ceria is investigated. The soot conversion light-off temperature is significantly lowered with the application of anatase-TiO2 as the support in comparison to the unsupported and γ-Al2O3 supported CeO2–MnOx catalysts. Additionally, considerable enhancement in bulk and surface defects is observed for CeO2–MnOx/TiO2, which is attributed to the promotional role of the CeO2/TiO2 interface in the formation and stabilization of defect sites. The temperature programmed desorption of oxygen (O2-TPD) study of CeO2–MnOx/TiO2 indicates a sharp increase in oxygen desorption after a temperature of 500 K. In good correlation, the diesel soot conversion substantially increases after 550 K, but below this temperature the TiO2 supported catalyst exhibits comparable activity to that of the γ-Al2O3 supported catalyst. Increased oxygen mobility at elevated temperatures might play a key role in the performance of the TiO2 supported catalyst. Moreover, its structural stability and appreciable catalytic activity were retained even after high temperature annealing treatment.