Catalytic Oxygen Removal from Synthetic Coke Oven Gas: A Comparison of Sulfided CoMo/γ-Al2O3 and NiMo/γ-Al2O3 Catalysts with Pt/γ-Al2O3 as Benchmark Catalyst

For the oxygen removal from coke oven gas (COG) the catalytic activity of commercial catalysts CoMo/γ-Al₂O₃ and NiMo/γ-Al₂O₃ was evaluated after a sulfidation pretreatment and compared to the Pt/γ-Al₂O₃ reference catalyst. Elemental analysis and temperature-programmed desorption showed that the oxidation reaction and the associated oxidation of active sulfidic centers is the main cause of deactivation despite the presence of other reductants, such as hydrogen. This approach could allow an appropriate sulfide catalyst to be designed for oxygen removal corresponding to the typical COG composition in the presence of H₂S.     

Conversion of natural gas to C2 product,hydrogen and carbon black using a catalytic plasma reaction

In the microwave and RF plasma catalytic reaction at room temperature, the decomposition of natural gas over Pd–NiO/γ-Al₂O₃ was carried out. The decomposition of methane is caused by collision by excitation of unstable electronic state. Measuring the flow rate and plasma power can represent kinetic data and mechanism. The conversion of C₂ hydrocarbons was increased from 47% to 63.7% in the microwave plasma catalytic reaction within electric field. Comparing the activities of catalysts, Pd–NiO/γ-Al₂O₃ bimetallic catalyst was more active than Pt–Sn/γ-Al₂O₃ catalyst because of modifying the surface of catalysts by carbon formation. In RF plasma catalytic reaction, we obtained high C₂ yield of 72%, in which the conversion and selectivity of C₂ hydrocarbons were related to the applied power and feed rate of natural gas.     

Catalytic performance of Co-Mo-Ce-K/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for the shift reaction of CO in coke oven gas

The catalytic performance of Co-Mo-Ce-K/γ-Al₂O₃ catalyst for the shift reaction of CO in coke oven gas is investigated using X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results indicate that Ce and K have a synergistic effect on promoting the catalytic activity, and the Co-Mo-Ce-K/γ-Al₂O₃ catalyst with 3.0 wt-% CeO₂ and 6.0 wt-% K₂O exhibits the highest activity. CeO₂ favors Co dispersion and mainly produces an electronic effect. TPR characterization results indicate that the addition of CeO₂-K₂O in the Co-Mo-Ce-K/γ-Al₂O₃ catalyst decreases the reduction temperature of active components, and part of octahedrally coordinated Mo⁶⁺ transforms into tetrahedrally coordinated Mo⁶⁺, which has a close relationship with the catalytic activity.     

Strong improvement on CH4 oxidation over Pt/γ-Al2O3 catalysts

A very strong promotion effect of the presence of 1000 ppmV C₃H₈ in the reaction feed on CH₄–O₂ reaction was found over unsulfated 1%Pt/γ-Al₂O₃ catalyst. This promotion was further increased on pre-sulfated 1%Pt/γ-Al₂O₃. The promoting effect of pre-sulfation on the activity of 1%Pt/γ-Al₂O₃ for propane combustion results in a further improvement on methane combustion due to propane combustion heat which is generated at lower temperatures, activating methane combustion over pre-sulfated 1%Pt/γ-Al₂O₃ at even lower temperatures relative to unsulfated 1%Pt/γ-Al₂O₃. These results suggest that small amounts of propane in the gas feed during CH₄–O₂ reaction over a pre-sulfated Pt/γ-Al₂O₃ catalyst may eliminate methane emissions at low temperatures from lean-burn NGV exhausts without being deactivated by sulfur poisoning as Pd supported catalysts.     

Enhancement of VOCs removal using a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor

We developed a novel double-tube packed bed catalytic dielectric barrier discharge (DPDBD) reactor to degrade toluene. The DPDBD reactor contains four discharge cells with one power supply, namely, A–D. NiO/γ-Al₂O₃ is packed in cell A to effectively destroy the branched chains in toluene. TiO₂/γ-Al₂O₃ is packed in cell B owing to its high catalytic oxidation activity to weaken the benzene rings and mineralize the generated partial aromatic compounds. Cell C is a pure DBD process without any catalyst packed to thoroughly mineralize all the generated aromatic compounds and convert CO into CO₂ and NO into NO₂. γ-Al₂O₃ is packed in cell D to reduce the concentrations of byproducts, including O₃ and NO generated by air through oxidation. The combinations of the four discharge cells are optimized by the treatment of −3000 mg m⁻³ of toluene at 11 kV. In comparison with a double-tube dielectric barrier discharge (DDBD) reactor without catalyst packing and with a total discharge length of 6 cm, the selectivity of CO₂ was significantly improved from 45% to 57% when the discharge lengths of A, B, C, and D are 2, 4, 4, and 2 cm, respectively. Furthermore, the concentrations of O₃ and NO in the outlet can also be effectively reduced from 2.80 and 210 mg m⁻³ to 1.30 and 60 mg m⁻³, respectively. We also investigated the effects of applied voltage and styrene initial concentration.     

Direct dehydrogenation of n-butane over Pt/Sn/M/γ-Al2O3 catalysts: Effect of third metal (M) addition

A series of Pt/Sn/M/γ-Al₂O₃ catalysts with different third metal (M = Zn, In, Y, Bi, and Ga) were prepared by a sequential impregnation method for use in the direct dehydrogenation of n-butane to n-butene and 1,3-butadiene. In the direct dehydrogenation of n-butane, Pt/Sn/Zn/γ-Al₂O₃ catalyst showed the best catalytic performance. Catalytic performance decreased in the order of Pt/Sn/Zn/γ-Al₂O₃ > Pt/Sn/In/γ-Al₂O₃ > Pt/Sn/γ-Al₂O₃ > Pt/Sn/Y/γ-Al₂O₃ > Pt/Sn/Bi/γ-Al₂O₃ > Pt/Sn/Ga/γ-Al₂O₃. The catalytic performance increased with increasing metal–support interaction and Pt surface area of the catalyst.     

Catalytic wood liquefaction using a hydrogen donor solvent

Direct wood liquefaction of pine sawdust (Pinus radiata) in a hydrogen donor solvent (tetralin), was studied in a 0.5 L autoclave using Co-Mo/γ-Al₂O₃ and Pt/γ-Al₂O₃ supported catalysts. Uncatalyzed as well as Raney Nickel catalyzed runs were also performed for comparison purposes. Reaction temperature was kept at 673 K and total system pressure at 10 MPa in all cases. Weight ratio of solvent to solid loaded was 2:1, the gas phase being either H₂ or N₂. Independent runs were also performed with cellulose and lignin which are the main wood constituents. Reaction products were characterized by means of gas chromatography and solvent fractionation using specific solvents.     

Enhanced catalytic activity of Pt/Al2O3 on the CH4 SCR

In this study, we investigated the effect of mixing α-Al₂O₃ and γ-Al₂O₃ with a Pt catalyst on CH₄ selective catalytic reduction (SCR). Among the prepared catalysts, the Pt/α-Al₂O₃ catalyst was found to have the lowest catalytic activity, but the best adsorption characteristics for CH₄, which was used as the reductant. In contrast, the Pt/γ-Al₂O₃ catalyst was found to exhibit relatively high catalytic activity and moderate adsorption characteristics. To simultaneously enhance the catalytic activity and CH₄ adsorption characteristics, we developed a new catalyst, Pt/γ-Al₂O₃ + Pt/α-Al₂O₃, by mixing α-Al₂O₃ and γ-Al₂O₃ with a Pt catalyst. The catalytic activity test confirmed that mixing these catalysts led to enhanced catalytic activity.     

Steam reforming of liquid petroleum gas over Mn-promoted Ni/γ-Al2O3 catalysts

Three different Mn-promoted Ni/γ-Al₂O₃ catalysts, Mn/Ni/γ-Al₂O₃, Mn-Ni/γ-Al₂O₃ and Ni/Mn/γ-Al₂O₃, were prepared and applied to the steam reforming of liquid petroleum gas (LPG) mainly composed of propane and butane. For comparison, Ni/γ-Al₂O₃ catalysts containing different amount of Ni were also examined. In the case of the Ni/γ-Al₂O₃ catalysts, 4.1 wt% Ni/γ-Al₂O₃ showed the stable catalytic activity with the least amount of coke formation. Among the various Mn-promoted Ni/γ-Al₂O₃ catalysts, Mn/Ni/γ-Al₂O₃ showed the stable catalytic activity with the least amount of coke formation. It also exhibited a similar H₂ formation rate compared with Ni/γ-Al₂O₃. Several characterization techniques—N₂ adsorption/desorption, X-ray diffraction (XRD), CO chemisorptions, temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and CHNS analysis—were employed to characterize the catalysts. The catalytic activity increased with increasing amount of chemisorbed CO for the Mn-promoted Ni/γ-Al₂O₃ catalysts. The highest proportion of Mn⁴⁺ species was observed for the most stable catalyst.     

Deactivation and coke formation on palladium and platinum catalysts in vegetable oil hydrogenation

Deactivation of palladium and platinum catalysts due to coke formation was studied during hydrogenation of methyl esters of sunflower oil. The supported metal catalysts were prepared by impregnating γ-alumina with either palladium or platinum salts, and by impregnating α-alumina with palladium salt. The catalysts were reused for several batch experiments. The Pd/γ-Al₂O₃ catalyst lost more than 50% of its initial activity after four batch experiments, while the other catalysts did not deactivate. Samples of used catalysts were cleaned from remaining oil by repeated extractions with methanol, and the amount of coke formed on the catalysts was studied by temperature-programmed oxidation. The deactivation of the catalyst is a function of both the metal and the support. The amount of coke increased on the Pd/γ-Al₂O₃ catalyst with repeated use, but the amount of coke remained approximately constant for the Pt/γ-Al₂O₃ catalyst. Virtually no coke was detected on the Pd/α-Al₂O₃ catalyst. The formation of coke on Pd/α-Al₂O₃ may be slower than on the Pd/γ-Al₂O₃ owing to the carrier’s smaller surface area and less acidic character. The absence of deactivation for the Pt/γ-Al₂O₃ catalyst may be explained by slower formation of coke precursors on platinum compared to palladium.     

Preferential Oxidation of CO in H2-Rich Gases over Co-Promoted Pt-γ-Al2O3 Catalyst

Carbon monoxide is a poison to the Pt anode in proton exchange membrane fuel cell (PEMFC). Preferential oxidation (PROX) is an effective method to reduce CO in hydrogen-rich gas streams to a tolerant level. In the present work, the effect of adding cobalt to Pt/γ-Al₂O₃ on the PROX of CO was investigated. Our results showed that the addition of Co to Pt/γ-Al₂O₃ could not only improve the low-temperature activity but also reduce significantly the loading of Pt in the catalysts. Over the catalyst 3%Co/1%Pt/γ-Al₂O₃ the conversion of CO was close to 100% at 90 °C and space velocity of 8000 mL g^?1 h^?1. In addition, the Co-promoted Pt/γ-Al₂O₃ catalyst showed good resistance to H₂O and CO₂ and could be operated in a wide range of space velocity. At temperatures above 90 °C, the existence of H₂O in the feed increased the conversion and broadened the operating temperature range without worsening the selectivity. When space velocity was changed from 8000 to 80,000 mL g^?1 h^?1 and temperatures was kept between 120 and 160 °C, the conversion of CO was always over 99% and the decrease in O₂ selectivity did not exceed 10%. Furthermore, a strong opposite effect of the ratio of O₂ to CO on the conversion of CO and the selectivity of O₂ was observed. However, at the O₂/CO ratio of 1.0 and temperatures between 120 and 160 °C, a satisfied balance between conversion and selectivity could be obtained.     

Methane conversion to higher hydrocarbons in a dielectric-barrier discharge reactor with Pt/γ-Al2O3 catalyst

Plasma catalytic reactions were applied to the conversion of methane to C₂, C₃ or higher hydrocarbons in a dielectric-barrier discharge (DBD) reactor at atmospheric pressure. Methane conversion was increased with the increase of Pt loading on γ-Al₂O₃. The highest C₂H₆ selectivity was 50.3% when 3 wt% Pt/γ-Al₂O₃ catalyst was calcined at 573 K. Methane conversion was increased with the increase of the catalyst weight in DBD reactor. The major products were C₂H₆ and C₃H₈, which were independent of catalyst weight in the presence of catalyst.     

Tuning product selectivity of CO2 hydrogenation by OH groups on Pt/γ-AlOOH and Pt/γ-Al2O3 catalysts

Herein, we explore how OH groups on Pt/γ-AlOOH and Pt/γ-Al₂O₃ catalysts affect CO₂ hydrogenation with H₂ at temperatures from 250°C to 400°C. OH groups are abundant on γ-AlOOH, but rare at Pt-(γ-AlOOH) interface which is the most favorable site for CO₂ conversion on Pt/γ-AlOOH. This makes CO₂ hydrogenation on Pt/γ-AlOOH form CO weakly bonding to γ-AlOOH, which prefers to desorption from Pt/γ-AlOOH rather than further conversion, thus enhancing CO production on Pt/γ-AlOOH. Different from Pt/γ-AlOOH, OH groups are abundant at Pt-(γ-Al₂O₃) interface which is the most favorable site for CO₂ conversion on Pt/γ-Al₂O₃. This promotes CO₂ hydrogenation on Pt/γ-Al₂O₃ to form CO strongly bonding to Pt, which prefers to further hydrogenation to CH₄, and thereby increases CH₄ selectivity on Pt/γ-Al₂O₃. Therefore, the OH groups at metal-support interface are crucial factor influencing product distribution, and must be considered seriously when fabricating catalysts.     

Non-Catalyzed and Pt/γ-Al2O3 Catalyzed Hydrothermal Cellulose Dissolution-Conversion: Influence of the Reaction Parameters

The dissolution of cellulose under 5 MPa of H₂ in the absence of catalyst is temperature and time dependant. The presence of Pt/γ-Al₂O₃ increases the initial rate of dissolution. The presence of H₂/Pt is essential although its exact role has not been well elucidated.     

Methane conversion over nanostructured Pt/γAl2O3 catalysts in dielectric-barrier discharge

Spherical nanostructured γ-Al₂O₃ granules were prepared by combining the modified Yoldas process and oil-drop method, followed by the Pt impregnation inside mesopores of the granules by incipient wetness method. Prepared Pt/γ-Al₂O₃ catalysts were reduced by novel method using plasma, which was named plasma assisted reduction (PAR), and then used for methane conversion in dielectric-barrier discharge (DBD). The effect of Pt loading, calcination temperature on methane conversion, and selectivities and yields of products were investigated. Prepared Pt/γ-Al₂O₃ catalysts were successfully reduced by PAR. The main products of methane conversion were the light alkanes such as C₂H₆, C₃H₈ and C₄H₁₀ when the catalytic plasma reaction was carried out with Pt/γ-Al₂O₃ catalyst. Methane conversion was in the range of 38–40% depending on Pt loading and calcination temperature. The highest yield of C₂H₆ was 12.7% with 1 wt% Pt/γ-Al₂O₃ catalysts after calcinations at 500 ‡C.     

Development and Application of Sintering Dynamics Simulation for Automotive Catalyst

Sintering behavior of Pt/γ-Al₂O₃, Pt/ZrO₂ and Pt/CeO₂ catalyst was studied using an originally developed 3D sintering simulator. Experimental results were well reproduced. While Pt on the γ-Al₂O₃ sintered significantly, Pt on CeO₂ presented the highest stability against sintering. On the other hand, grain growth of supports was significant in the order; ZrO₂ > CeO₂ > γ-Al₂O₃.     

Enhanced Low Temperature NO x Reduction Performance Over Bimetallic Pt/Rh–BaO Lean NO x Trap Catalysts

The overall NSR operation was tested over a bimetallic Pt/Rh–BaO lean NO _x trap (LNT) catalyst in the range of 473–673 K with simulated diesel exhausts and compared to monometallic 1 wt% Pt/BaO/γ-Al₂O₃ and 0.5 wt% Rh/BaO/γ-Al₂O₃ samples. The results showed the beneficial effect of the simultaneous presence of 0.5 wt% Pt and 0.25 wt% Rh on the catalytic performance under lean-burn conditions at low temperatures. It was observed that both Pt/BaO/γ-Al₂O₃ and Rh/BaO/γ-Al₂O₃, which both were mildly aged, have limited NO _x reduction capacity at 473 K. However, combining Pt and Rh in the NO _x storage catalyst assisted the NO _x reduction process to occur at lower temperatures (473 K). One possible reason could be that the combined Pt and Rh sample was more resistant to aging. In addition, the NO₂-TPD data showed that the presence of Rh into the Pt/BaO/γ-Al₂O₃ system has a considerable effect on the spill-over process of NO _x , accelerating the release of NO _x at lower temperatures. These results were in a good agreement with the observed higher rate of oxygen release of the bimetallic Pt/Rh catalyst, leaving a significant number of noble metal sites available for adsorption at lower temperatures than that of the monometallic Pt sample. The superior NSR performance of the bimetallic Pt/Rh/BaO/γ-Al₂O₃ catalyst under lean-burn conditions suggested the existence of synergetic promotion effect between the Pt and Rh components, increasing the NO _x reduction efficiency in comparison with that of the monometallic Pt and Rh–BaO LNT catalysts.     

Promoting and inhibiting effect of SO2 on propane oxidation over Pt/Al2O3

SO₂ adsorption, SO₂ oxidation and oxidation of propane with oxygen in the absence and the respective presence of SO₂ in the feed gas were studied over unsulfated and sulfated 1% Pt/γ-Al₂O₃.Results showed that the promoting effect of SO₂ in the reaction flux on C₃H₈ oxidation over 1% Pt/γ-Al₂O₃ depends on the presulfating temperature. Catalytic activity measurements and FTIR absorption spectra showed that during propane oxidation, Pt/support interfacial adsorbed species were formed at temperatures 25–300 °C, inhibiting C₃H₈ oxidation. However, at higher temperatures these Pt/support interfacial adsorbed species were oxidized, leading to Pt/support interfacial sulfate species, which strongly promote propane oxidation.     

Differences in coke burning-off from Pt–Sn/Al2O3 catalyst with oxygen or ozone

Pt–Sn/γ-Al₂O₃ catalysts with different Sn loadings were prepared by incipient wetness coimpregnation of γ-Al₂O₃ with H₂PtCl₆ and SnCl₂. The Pt–Sn interaction was tested by temperature-programmed reduction and the catalytic activity was measured by cyclohexane dehydrogenation. The catalysts were coked by cyclopentane at 500 °C and totally or partially decoked with O₂ at 450 °C or O₃ at 125 °C. Coke deposits were studied by TPO and the catalytic activity of coked catalysts, partially or totally regenerated, by cyclohexane dehydrogenation.The TPO with O₃ shows that coke combustion with O₃ starts at a low temperature and has a maximum at 150 °C, that is a compensation between the increase of the burning rate and the rate of O₃ decomposition when increasing the temperature. Meanwhile O₂ burns coke with a maximum at 500 °C. When performing partial decoking with O₃ (125 °C) the remaining coke is more oxygenated and easier to burn than the coke that remains after decoking with O₂ (450 °C).After burning with O₃ the dehydrogenation activity of the fresh catalyst is recovered, while after burning with O₂ the activity is higher than that of the fresh catalyst. The burning with O₃ practically does not change the original Pt–Sn interaction while the burning with O₂ produces a decrease in the interaction, producing free Pt sites with higher dehydrogenation capacity.The differences in coke combustion with O₃ and O₂ are due to the different form of generation of activated oxygen, the species that oxidizes the coke. O₃ is activated by the γ-Al₂O₃ support at low temperatures firstly eliminating coke from the support while O₂ is activated by Pt at temperatures higher than 450 °C and the coke removal starts on the metal. Then, the recovery of the Pt catalytic activity as a function of coke elimination is faster with O₂ than with O₃.     

Effect of Cu promoter and alumina phases on Pt/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for propane dehydrogenation

We investigated the effects of different Cu weight ratio on θ or γ-Al₂O₃ which were impregnated with platinum in terms of catalytic activity for propane dehydrogenation and physicochemical properties. 1.5 wt% Pt, 0-10 wt% Cu catalyst supported on θ-Al₂O₃ or γ-Al₂O₃ was prepared by incipient wetness co-impregnation. Enhanced Pt dispersion by increasing Cu contents in γ-Al₂O₃ supported catalyst was confirmed via XRD and XPS. Pt and CuO was separated in Pt-Cu/θ-Al₂O₃, but Pt-Cu alloy was identified after reduction treatment. Also, adding Cu in Pt/Al₂O₃ makes catalyst’s acidity lower and this property led to increased propylene yield in propane dehydrogenation. However, Pt₃Cu was not good for yield of PDH, which was confirmed in Pt-10Cu/θ-Al₂O₃ through XRD.