2O3 Nanocatalyst Research Articles

Hydrogen production via supercritical water gasification of bagasse using unpromoted and zinc promoted Ru/γ-Al2O3 nanocatalysts

Supercritical water gasification (SCWG) of bagasse was performed in the presence of unpromoted and zinc promoted Ru/γ-Al2O3 nanocatalysts prepared with impregnation and microemulsion techniques. Nanocatalysts were characterized by ICP, BET, XRD, H2 chemisorption, and TEM techniques. The microemulsion technique decreased the catalyst average particle size to 3.9nm and increased the percentage dispersion and reduction to 89.6% and 90% respectively. Using the microemulsion technique for preparation of Ru/γ-Al2O3 increased the hydrogen yield to 15.6 (mmol of H2/g of bagasse) and CO yield to 7.5 (mmol of CO/g of bagasse). Promotion of Ru/γ-Al2O3 with 1.5wt.% zinc increased the total gas yield by 6.6%. The yields of hydrogen and carbon monoxide increased by 16.67% and 7.25%. The yield of methane decreased by 32.7%.

A nanostructured CeO2 promoted Pd/α-alumina diethyl oxalate catalyst with high activity and stability

A Pd–CeO2/α-Al2O3 nanocatalyst was used as a catalyst for CO oxidative coupling to diethyl oxalate with the CO conversion significantly increased.

Shape-Dependent Catalytic Oxidation of 2-Butanol over Pt Nanoparticles Supported on γ-Al2O3

This study illustrates the effect of nanoparticle (NP) shape on the reactivity of size-selected Pt/γ-Al2O3 nanocatalysts for 2-butanol oxidation. Nanoparticles similar in size [transmission electron microscopy (TEM) diameter of ∼1 nm] but with different shapes were prepared via encapsulation in inverse micelles. The NP shape was resolved by combining information extracted from extended X-ray absorption fine structure spectroscopy (EXAFS) data, TEM, and modeling. A correlation was observed between the average first nearest neighbor coordination number of atoms at the NP surface and their catalytic activity. In particular, the NPs with the largest number of weakly coordinated surface atoms (i.e., edges and corners) were found to be the least active for the total oxidation of 2-butanol. This result highlights that not only size but also shape control must be achieved to tailor the catalytic properties of nanoscale materials.

Photodegradation of Chlorophenoxyacetic Acids by ZnO/r-Fe2O3 Nanocatalysts: A Comparative Study

ZnO/r-Fe2O3 nanocomposite was synthesized via simple precipitation. The synthesized nanocatalysts underwent heat treatment at 450 oC for an hour. The characteristics of the nanocomposite were investigated by XRD, TEM, and BET surface area measurement. Zeta potential analysis was used to examine the surface charge properties of the nanocatalysts. The synthesized nanocomposite has an average particle size of 11 nm and a surface area of 20 m2 g-1. The potential of ZnO/r-Fe2O3 as a photocatalyst was evaluated by photodegrading chlorophenoxyacetic acids (PAA, 2,4-D, 2,4,5-T and 4CA). The decomposition of chlorophenoxyacetic acids by ZnO/r-Fe2O3 followed 4CA > 2,4,5-T = 2,4-D > PAA. The result indicates the applicability of ZnO/r-Fe2O3 nanocomposite as a photocatalyst in removing organic pollutants in wastewater.

An ultra-low Pd loading nanocatalyst with high activity and stability for CO oxidative coupling to dimethyl oxalate

A Pd/α-Al2O3 nanocatalyst with ultra-low Pd loading exhibits high activity and stability for CO oxidative coupling to dimethyl oxalate, which was prepared by a Cu(2+)-assisted in situ reduction method at room temperature. The small size and high dispersion of Pd nanoparticles facilitated by Cu(2+) ions are responsible for the excellent catalytic activity.

Benzene hydrogenation over highly active monodisperse Ru/γ-Al2O3 nanocatalyst synthesized by (w/o) reverse microemulsion

Ruthenium nanoparticles (10–40 nm) were synthesized by the reduction of aqueous ruthenium trichloride in aqueous sodium borohydride by the water-in-oil (w/o) reverse microemulsion method at atmospheric temperature. The synthesized Ru nanoparticles (Ru content 1–5 wt%) were dispersed on γ-alumina of high surface area by a high speed mechanical stirrer. The nanocatalysts (Ru/γ-Al2O3) were characterized by transmission electron microscopy, X-ray diffraction, N2-physisorption, BET surface area, hydrogen chemisorption and thermogravimetric analysis (TG/DTA). The activity of the nanocatalyst was tested in the gas–liquid phase hydrogenation reaction of benzene to cyclohexane at 40–100 °C and 20 bar hydrogen pressure. The activities of the catalysts were studied by varying different parameters such as Ru loading (wt% of Ru), reaction temperatures, catalyst recycling, thiophene (catalyst poison) concentration, stirring speed and metal nanoparticles size etc. The results showed that maximum activity (100 % conversion of benzene) was obtained at 80 °C and 20 bar pressure with 4 wt% (Ru content) catalyst. The activation energy and TOF were found to be 27.9 kJ mol −1 and 1416.8 h−1, respectively, which indicated higher activity of Ru/γ-Al2O3 catalyst than conventional catalyst for the hydrogenation of benzene to cyclohexane.

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al2O3 nano catalysts in Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch (FT) synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes (CNTs) catalysts is reported. 20 wt% of cobalt is loaded on the supports by impregnation method. The deactivation of the two catalysts was studied at 220°C, 2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor. The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified. Formation of cobalt-support mixed oxides in the form of xCoO·yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation. However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation. In the case of the CO/γ-Al2O3 catalyst, after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm, whereas, under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm. Although, the initial FT activity of the Co/CNTs was 26% higher than that of the CO/γ-Al2O3, the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the CO/γ-Al2O3 by 32%. For the CO/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step. It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support, but the Co/CNTs catalyst is more susceptible for deactivation.

Innovative Process for the Synthesis of Nanostructured Ruthenium Catalysts and their Catalytic Performance

An efficient, reproducible process for the solvothermal synthesis of Ru/γ-Al2O3 nanocatalysts has been developed. This synthesis employs a low boiling point alcohol acting as solvent and reducing agent. The reaction is performed in autoclave under nitrogen overpressure, by heating the solution of metal precursor and stabilizing agent in the presence of the support. These systems show very promising performances, also with an application perspective, in the selective hydrogenation of phenol to cyclohexanone carried out at 160 °C under 5 MPa of hydrogen: a selectivity to cyclohexanone as high as 83% has been reached at a phenol conversion value of 88%.