Dehydrogenation of Ethylbenzene in the Presence of CO2 over V Catalysts Supported on Nano-sized Alumina

Carbon-covered alumina (CCA) were synthesized from mesoporous alumina and a series of carbon sources (including sucrose, furfuryl alcohol, and benzene). They had structural properties of alumina and surface characteristics of carbon. When they were used as supports for molybdenum carbide, nitride, and phosphide catalysts, significantly higher activities were obtained in hydrazine decomposition as compared to those supported on the conventional alumina. The difference in the interactions of catalytic active sites with the CCA and with the alumina supports was preliminarily deemed to be the main cause of the better performance of CCA supported catalysts. Carbon contents on alumina and carbon sources were found to be important for CCA to be a good support. Carbon deposited on alumina in a near monolayer form showed the best activities. In contrast with sucrose and furfuryl alcohol, benzene as the carbon source readily yielded CCA supports with a hydrophobic surface, which resulted in relatively low dispersions of metal and, in turn, decreased activity of the supported catalysts.     

负载型NiO-La2O3催化剂在CO2甲烷化反应中的研究

将二氧化碳转化为易于储存和运输的高热值燃料——甲烷,不仅可以缓解温室效应,也是解决能源短缺的有效途径。本文采用柠檬酸络合的等体积超声浸渍法制备一系列NiO-La₂O₃/SiO₂催化剂,其中镍和镧的摩尔比为1:1,并采用XRD、H₂-TPR表征技术对NiO-La₂O₃/SiO₂催化剂的结构和物化性质进行了研究。考察了NiO-La₂O₃的负载量对CO₂甲烷化反应性能的影响。结果表明,10%NiO-La₂O₃/SiO₂催化剂表现出最优的CO₂甲烷化反应性能,且在450℃时表现出最佳的反应活性,CO₂转化率和CH₄选择性分别为59.3%和60.8%。     

CO2 Methanation on Nickel Catalysts Supported on Mesoporous High‐Surface‐Area MgSiO3

Nickel catalysts prepared on high‐surface‐area mesoporous MgSiO₃ were synthesized and applied in methanation of CO₂. N₂ adsorption analysis confirmed the presence of the mesoporous structure on the synthesized samples and revealed that the increase in nickel content resulted in a shift of the pore size distributions to smaller pore sizes. Temperature‐programmed reduction analysis illustrated an improvement in reducibility of the catalysts by a higher nickel content. Catalytic results indicated enhanced CO₂ conversion with the increase in nickel percentage up to 15 wt %. The catalysts with higher percentage of nickel provided lower CO₂ conversion and CH₄ selectivity. The %15Ni/MgSiO₃ catalyst exhibited high catalytic stability under optimized conditions.     

Physicochemical Characterization and H2-TPD Study of Alumina Supported Ruthenium Catalysts

A series of alumina supported ruthenium catalysts, which prepared by hydrogen treatment or hydrazine reduction, were characterized by N₂ adsorption, X-ray diffraction (XRD), X-ray fluorescence (XRF), CO chemisorption, and Temperature-programmed desorption of hydrogen (H₂-TPD). In contrast to the samples with conventional hydrogen reduction, there was almost no residual chlorine in the samples using RuCl₃ as precursor with hydrazine treatment. Furthermore, the dissolved aluminum could be removed much more easily in basic solution, which led to the higher BET surface and pore volume of hydrazine-reduction catalysts. Therefore, the active phase (Ru metal) would not be contaminated. Three main peaks, which occurred at about 150, 375, and 650 °C, respectively, were observed in the H₂-TPD profiles of Ru/Al₂O₃ catalysts with a high amount of residual chlorine. A new peak of desorption hydrogen centering at 240 °C, which was completely suppressed by the high amount of residual chlorine, might appear in the profiles of the samples with the washing procedure following hydrogen reduction or hydrazine treatment. The peaks with the desorption temperature lower than 500 °C were relative with dissociatively adsorbed hydrogen and spillover hydrogen simultaneity, and the peak at above 500 °C was caused by spillover hydrogen and would be stabilized by hydroxyl groups on alumina surface.     

Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

Catalysis Letters - We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the...     

Deactivation of Supported Copper Catalysts for Methanol Synthesis

Binary Cu/ZnO and Cu/Al₂O₃ as well as ternary Cu/ZnO/Al₂O₃ catalysts were investigated with respect to their catalytic activity and stability in methanol synthesis. In a rapid aging test, activity measurements were carried out in combination with the determination of the specific Cu surface area. A close correlation between the loss of catalytic activity and the decrease in specific Cu surface area was found due to sintering of the Cu particles. Differences in the deactivation behavior and the area-activity relationship of each catalyst system imply that the catalysts should be grouped in different classes.     

Performance of Ni/Nano-ZrO2catalysts for CO preferential methanation简

Large surface areas nano-scale zirconia was prepared by the self-assembly route and was employed as support in nickel catalysts for the CO selective methanation. The effects of Ni loading and the catalyst calcination temperature on the performance of the catalyst for CO selective methanation reaction were investigated. The cata- lysts were characterized by Brunauer-Emmett-Teller （BET）, transmission electron microscope （TEM）, X-ray dif- fraction （XRD） and temperature-programmed reduction （TPR）. The results showed that the as-synthesized Ni/nano-ZrO2 catalysts presented high activity for CO methanation due to the interaction between Ni active particle and nano zir- conia support. The selectivity for the CO methanation influenced significantly by the particle size of the active Ni species. The exorbitant calcination resulted in the conglomeration of dispersive Ni particles and led to the decrease of CO methanation selectivity. Among the catalysts studied, the 7.5% （by mass） Ni/ZrO2 catalyst calcinated at 500℃ was the most effective for the CO selective methanation. It can preferentially catalyze the CO methanation with a higher 99% conversion in the CO/CO2 competitive methanation system over the temperature range of 260-280℃, while keeping the CO2 conversion relatively low.     

Methane Transformation in Presence of Carbon Dioxide on Activated Carbon Supported Nickel–calcium Catalysts

The objective of the present work was to study the catalytic reformation of methane in presence of carbon dioxide on activated carbon-supported nickel and calcium catalysts. Results are very promising ones because they suggests that it is possible to transform methane on these catalysts by using mild reaction conditions.     

Dehydrogenation of Propane in the Presence and Absence of CO2 Over β-Ga2O3 Supported Chromium Oxide Catalysts

The dehydrogenation of propane to propene in the presence and absence of CO₂ over β-Ga₂O₃ supported chromium oxide catalysts has been studied. The effect of chromium content and feed composition on the dehydrogenation of propane has been investigated. It has been found that deposition of chromium oxide enhances the dehydrogenation activity and resistance to coke deposition. Moreover, it has been shown that CO₂ promotes the dehydrogenation of propane above 848 K. At that temperature in the presence of CO₂ both the yield of propene and conversion of propane were higher than in the inert gas atmosphere.     

镍基非晶态催化剂上氯代硝基苯选择性加氢合成氯代苯胺

分别以碳纳米管(CNTs),γ-Al2O3,Si O2,Ti O2为载体,Ni、B为活性组分,采用浸渍-化学还原法制备了一系列负载型Ni-B非晶态合金催化剂,并将其用于三种氯代硝基苯液相加氢反应。采用电感耦合等离子体光谱、X-射线衍射、透射电子显微镜、差示扫描量热等手段研究了催化剂的非晶性质、Ni的担载量及催化剂的热稳定性。结果表明,负载型Ni-B非晶态合金催化剂在氯代硝基苯液相加氢反应中表现出较高的活性和良好的选择性,其中以CNTs为载体的非晶态合金Ni-B催化剂可使三种氯代硝基苯的转化率均达到了99.9%,加氢脱氯率小于2.5%。讨论了CNTs和Ni-B非晶态合金之间的相互作用与催化剂的催化性能的关系。     

Nickel Oxide Based Supported Catalysts for the In-situ Reactions of Methanation and Desulfurization in the Removal of Sour Gases from Simulated Natural Gas

Supported nickel oxide based catalysts were prepared by wetness impregnation method for the in-situ reactions of H₂S desulfurization and CO₂ methanation from ambient temperature up to 300 °C. Fe/Co/Ni (10:30:60)–Al₂O₃ and Pr/Co/Ni (5:35:60)–Al₂O₃ catalysts were revealed as the most potential catalysts, which yielded 2.9% and 6.1% of CH₄ at reaction temperature of 300 °C, respectively. From XPS, Ni₂O₃ and Fe₃O₄ were suggested as the surface active components on the Fe/Co/Ni (10:30:60)–Al₂O₃ catalyst, while Ni₂O₃ and Co₃O₄ on the Pr/Co/Ni (5:35:60)–Al₂O₃ catalyst.     

A Short Review on Ni-Catalyzed Methanation of CO2: Reaction Mechanism,Catalyst Deactivation,Dynamic Operation

Today, the use of renewable energies and recycling of climate-changing gases are increasingly important. In this context, coupling of methanation with small, decentralized CO₂ sources such as biogas plants provides one possibility. However, fluctuating availability of renewables for hydrogen production in combination with small storage volumes result in an enhanced demand for dynamic process operation. This leads to new research challenges with respect to the required catalysts and the overall process design. To draw reliable conclusions about the catalytic performance under dynamic process operation, the mechanism of the methanation reaction as well as typical deactivation procedures of the catalyst applied under steady-state conditions have to be reviewed thoroughly.     

Supported Vanadia Catalysts for Dehydrogenation of Ethylbenzene with CO2

Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO₂ were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated, it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO₂ was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity were acquired when V₂K/Al catalyst was used.     

Preferential CO Oxidation in the Presence of H2, H2O and CO2 at Short Contact-times

High selectivities and conversions in the preferential oxidation of CO in the presence of large quantities of H₂, H₂O and CO₂ are demonstrated on noble metal catalysts at millisecond contact times (~10–15 ms) for temperatures between 150 and 500 °C. With a simulated water-gas shift product stream containing 0.5% CO and varying amounts of H₂, H₂O and CO₂, we are able to achieve ~90% CO conversions on a Ru catalyst at temperatures of ~300 °C using a stoichiometric amount of O₂ (0.25%). Experiments with and without O₂ and with varying H₂O reveal that significant water-gas shift occurs on Pt and Pt-ceria catalysts at temperatures between 250 and 400 °C, while significant CH₄ is formed on Ru and Rh catalysts at temperatures greater than 250 and 350 °C, respectively. The presence of H₂O blocks H₂ adsorption and allows preferential CO oxidation at higher temperatures where rates are high. We propose that a multistage preferential oxidation reactor using these catalysts can be used to bring down CO content from 5000 ppm at the reactor entrance to less than 100 ppm at very short contact-times.     

Deactivation by Coking of Platinum/Alumina Catalysts: Effects of Operating Temperature and Pressure

Coke deposition is a complex reaction that results from the production of coke precursors and from their destruction. At low temperatures, when the destruction reaction (high apparent activation energy) is negligible, the coking rate is increased owing to increasing metal accessibility. In contrast, at high temperatures the coking reaction is hindered by an increasing metal loading. A change in the coking temperature does not alter the chemical nature of the carbonaceous deposits and their distribution between the metallic and acidic phases of a bifunctional catalyst. On the other hand, an increase in coking pressure (with a constant hydrogen:hydrocarbon molar ratio) promotes the graphitization of coke on the support, protecting the catalytic activity of the metallic phase.     

Selective Hydrogenation of Cinnamaldehyde to Hydrocinnamaldehyde over SiO2 Supported Nickel Phosphide Catalysts

The heterogeneous mercury reaction mechanism, reactions among elemental mercury (Hg⁰) and simulated flue gas across laboratory-scale selective catalytic reduction (SCR) reactor system was studied. The surface of SCR catalysts used in this study was analyzed to verify the proposed reaction pathways using transmission electron microscopy with energy dispersive X-ray analyses (TEM-EDX) and X-ray photoelectron spectroscopy (XPS). The Langmuir–Hinshelwood mechanism was proven to be most suitable explaining first-layer reaction of Hg⁰ and HCl on the SCR catalyst. Once the first layer is formed, successive layers of oxidized mercury (HgCl₂) are formed, making a multi-layer structure.     

Deactivation of Gold Catalysts Supported on Sulfated TiO2-ZrO2 Mixed Oxides for CO Oxidation During Catalytic Decomposition of Chlorodifluoromethane (HCFC-22)

Gold deposited on sulfated TiO₂-ZrO₂ with sodium hydroxide existed in the form of isotropic particles of 11 nm or less in diameter, whereas deposition with aqueous ammonia yielded larger anisotropic crystallites. The gold on sulfated TiO₂-ZrO₂ catalyst prepared by deposition with sodium hydroxide was active for the oxidation of carbon monoxide at room temperature in the presence of water vapor. However, the selectivity of the catalysts to carbon dioxide during the decomposition of chlorodifluoromethane in the presence of water vapor was increased by only a small extent compared to those without gold nanoparticles. The gold nanoparticles were deactivated for CO oxidation by HF and HCl formed during the hydrolysis of HCFC-22.