Papers by Keyword: Catalysis

Abstract: Chemical synthesis of nanocomposite particles based on titanium dioxide modified with iron and gold was carried out. It was shown that, depending on the mass content of the doping species, the phase transformation of titanium hydroxide at T = 700 °C proceeds with the formation of either anatase (2 wt.%) or anatase and rutile (8 wt.%). The doping species form a hematite phase and gold clusters on the metal-oxide surface. A weakly crystalline anatase obtained by the transformation of metatitanic acid (MTA), with a particle size of 8 nm and a sulfur content of 0.036%, was selected as the co-catalyst. The anatase co-catalyst exhibits photocatalytic activity in the destruction of organic dyes. Its introduction into the TiO₂&Fe₂O₃&Au nanocomposite suspension promotes the catalytic degradation of cationic and anionic dyes at temperatures ranging from 35 to 60 °C. It was observed that the degradation degree of the solutions after 150 min of catalytic process is the following: Methyl Orange (MO) – 72 %, Methylene Blue (MB) – 71.5 %, Rhodamine B (RhB) – 63.5 %, and Orange G (OG) – 47 %. The reaction rate constant depends on the composition of the dye, varying from 6.5·10^-4 min^-1 for OG to 2.56·10^-3 min^-1 for MB. The prospect of creating heterostructures based on TiO₂ modified with hematite and gold, and their further adaptation for photocatalytic hydrogen production, is considered.

Abstract: Supported 3wt%Pd/α-Al₂O₃ catalyst was tested in selective oxidation of 1,2-propanediol by molecular oxygen. It was found that the catalyst is active in an alkaline water solution. Lactic acid was obtained as the main product of the reaction. Influence of different reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. Partial kinetic orders of the reaction with respect to 1,2-propanediol, c₀(NaOH), p(O₂), n(1,2-PDO)/n(Pd)) were determined and an experimental kinetic model of the catalytic oxidation reaction was obtained. Activation energy of the process was calculated and was found to be about 53 ± 5 kJ/mol.

Abstract: This work is devoted to the study of the activity of 1% platinum catalysts containing rare earth element oxides (OREE) - Gd₂O₃, Ce₂O₃ and aluminum oxide as a carrier in the hydrogenation reactions of nitro compounds on the example of n-nitrotoluene. These catalytic systems in the conditions of liquid-phase hydrogenation provide high selectivity of the process and practically quantitative yield. The process was controlled by the potentiometric method, the reaction rate was judged by the amount of hydrogen absorbed per unit time. It is found that 20% and higher aqueous alcohol solutions can be used as a solvent during hydrogenation. It was found that the initial hydrogenation rate for 1% Pt/Gd₂O₃ is 3.2 times higher, and for 1% Pt/Ce₂O₃ Cerium it is 1.6 times higher relative to the 1% Pt/Al₂O₃ comparison catalyst.

Abstract: Fe-MIL-88B was prepared by a method that utilizes ferric nitrate and terephthalic acid (TPA or H₂BDC) as precursors. The catalyst was characterized by TEM, SEM, FTIR, XRD, BET, and TGA. The pyrolyzed MOF (Fe-MIL-88B/C) was then tested for FTS at 300 psi, 300/340°C and H₂/CO=1 after reduction under flow of hydrogen at 400°C for 4 hours. GC product results show promising FTS performance and stability compared to previously reported Fe-MOF derived catalysts with CO conversion of 96.90% at 340°C for 40 hours and 97.45% at 300°C for 26 hours.

Abstract: The paper studies the activity of 1 % palladium catalysts containing rare earth oxides (REOs) and alumina as a carrier in the hydrogenation of nitro compounds exemplified by nitrobenzene and o-nitro anisole. Under the liquid-phase hydrogenation conditions, these catalytic systems provide high selectivity of the process and a quantitative yield. It has been found that the partial replacement of Al₂O₃ with REO allows increasing the hydrogenation rate by 5–6 times, as compared with the reference catalyst and by 1.2–1.7 times as compared with the individual carrier. The oxide mixtures (REO and Al₂O₃) containing 20–40 % REO allow reaching the same hydrogenation rate with that over an REO-containing 1 % Pd catalyst.

Abstract: The use of various H₂O₂ based chemistries for TiW etch was studied on single wafer and wet bench tools. The focus of the investigation was put on the different behaviors of these chemicals on blanket and patterned wafers. The results of the etch rate tests showed much higher values on the wafers where copper was exposed, leading to the hypothesis that the etch rate on TiW should be driven by the catalysis effect of the transition metal on the H₂O₂ decomposition reaction. Additional optical inspections, ToF SIMS, SEM and TEM analyses were carried out to confirm this hypothesis and find the best conditions in terms of morphology for RDL applications. Finally, the collected data were also used to evaluate the process cycle time and cost of ownership.

Abstract: The efficient cleaning conversion of coal is more and more attracted due to resource exhaustion and environmental pollution. To improve the yield and quality of products of coal pyrolysis, the catalytic hydrogenated microwave pyrolysis was introduced, and the effects of metal sulfide on hydrogenated microwave pyrolysis were focused on discuss via the detection methods of proximate and ultimate analyses, SEM-EDS, FT-IR and GC-MS in this work. The results shown that because of the “hot-spot” effect and the characteristics of electromagnetic loss of metal sulfide, the temperature-rising rates with catalysts were obviously higher, but the final pyrolysis temperatures with or without catalyst were almost close. Higher temperature-rising rate with catalysts made the yield of liquid product more, which the yields of liquid product with MoS₂ and FeS₂ catalyst were 28.4 wt.% and 27.1 wt.%. The carbon distributions indicated that carbon in solid and gaseous products transferred into liquid product, when the catalysts added into pyrolysis reactions. The quality of tar with catalyst was improved, and the component content of light oil, intermedium oil and heavy oil were 67.55 wt.%, 27.98 wt.% and 4.47 wt.% for MoS₂ catalyst, in which the content of light oil increased by 10.30 times than that without catalyst. The thermal effect and catalysis of metal metal sulfide made complex aromatic compounds more thorough cracking, improved the amount and active of free hydrogen. Actived free hydrogen further enhanced cracking of heavy oil, resulting in the content of hydrogen in gaseous with catalysts decrease, and the content of light oil increased.

Abstract: 1.25 – 5wt%Pt/Al₂O₃, 1.25 – 5wt%Pd/Al₂O₃, 1wt%Pd/TiO₂, 1 – 5wt%Pd/TiO₂-NF, 1.25wt%Pt+1.25wt%Pd/Al₂O₃, 5wt%Pt/SiO₂, 5wt%Pt/C catalysts were synthesised and tested in the selective oxidation of 1,2-propanediol by molecular oxygen. It was found that all catalysts were active in alkaline water solutions; lactic acid was obtained as the main product of the reaction. The conversion of 1,2-propandiol and the yield of lactic acid depended on the content of active metal in the catalysts. The most active for the oxidation of 1,2-propandiol were palladium-containing catalysts supported on TiO₂ nanofibers (Pd/TiO₂-NF). The highest 1,2-propanediol conversion (100 %) and lactic acid yield (96 %) were obtained using the 5wt%Pd/TiO₂-NF catalyst at the following oxidation parameters: c₀(1,2-propanediol) = 0.3 mol/L, P(O₂) = 1 atm, n (1,2-propanediol)/n (Pd) = 500 mol/mol, t = 60 °C, c₀(NaOH) = 1.5 mol/L.

Abstract: This work demonstrates that 5wt% gold catalysts supported on Al₂O₃ and TiO₂ nanopowders as well as on TiO₂ nanofibers are active in the 1,2-propanediol (1,2-PDO) oxidation to lactic acid. The influence of catalysts different parameters and reaction conditions on 1,2-PDO conversion and oxidation process selectivity was studied. The best result was achieved using 5wt%Au/TiO₂ catalyst over the following oxidation parameters: c₀(1,2-PDO) = 0.3 mol/L, n (1,2-PDO)/n (Au) = 4000 mol/mol, p (O₂) = 6 bar, c₀(NaOH) = 2 mol/L, t = 60 °C: 1,2-propanediol conversion was 98 % and lactic acid selectivity 89 %.

Abstract: The Al₆₅Cu₂₀Fe₁₅ (in at.%) rapidly solidified ribbon in the form of brittle flakes was produced by melt-spinning technique. It consists the cell or dendrites of the icosahedral quasicrystalline I-phase surrounded by copper rich cubic τ-Al(Cu, Fe). The pulverized ribbon (fraction <32 μm) was subjected to NaBH₄ or 20% aqueous NaOH treatment, which led to the formation of oxide in the form of thin flakes at the outer layer of the powder particles. Test of the catalytic properties of the as spun ribbon and powder before and after treatment was made in the reaction of phenylacetylene hydrogenation. It was shown that for as received ribbon, even at very mild conditions (60 °C, H₂ pressure of 5 bar), 40% of phenylacetylene was converted to hydrogenation products with 0.7 styrene/ethylbenzene ratio. The use of pulverized ribbon resulted in improvement of activity, with the same ratio of reaction products. The effect of treatment with NaBH₄ led to improvement of the catalyst activity, while strongly alkaline solution of NaOH worsened significantly the catalytic activity, but improved selectivity to styrene (styrene/ethylbenzene=1.2).