Dynamic study of methane interaction with active sites involved in the total oxidation of methane over Pd/Al2O3 catalyst.

Water, which is an intrinsic part of the exhaust gas of combustion engines, strongly inhibits the methane oxidation reaction over palladium oxide-based catalysts under lean conditions and leads to severe catalyst deactivation. In this combined experimental and modeling work, we approach this challenge with kinetic measurements in flow reactors and a microkinetic model, respectively. We propose a mechanism that takes the instantaneous impact of water on the noble metal particles into account. The dual site microkinetic model is based on the mean-field approximation and consists of 39 reversible surface reactions among 23 surface species, 15 related to Pd-sites, and eight associated with the oxide. A variable number of available catalytically active sites is used to describe light-off activity tests as well as spatially resolved concentration profiles. The total oxidation of methane is studied at atmospheric pressure, with space velocities of 160,000 h−1 in the temperature range of 500–800 K for mixtures of methane in the presence of excess oxygen and up to 15% water, which are typical conditions occurring in the exhaust of lean-operated natural gas engines. The new approach presented is also of interest for modeling catalytic reactors showing a dynamic behavior of the catalytically active particles in general.

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Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Catalysts ◽

10.3390/catal10060613 ◽

2020 ◽

Vol 10 (6) ◽

pp. 613

Author(s):

Hussein Mahdi S. Al-Aani ◽

Mihaela M. Trandafir ◽

Ioana Fechete ◽

Lucia N. Leonat ◽

Mihaela Badea ◽

...

Keyword(s):

Electron Microscopy ◽

Transition Metal ◽

Mixed Oxide ◽

Mixed Oxides ◽

Catalytic Performance ◽

Atomic Ratio ◽

Total Oxidation ◽

X Ray ◽

Oxidation Of Methane ◽

Al2o3 Catalyst

To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 °C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides with x = 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at −196 °C, temperature-programmed reduction under hydrogen (H2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al2O3 catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T50) of 438 °C, which was only 19 °C higher than that of a reference Pd/Al2O3 catalyst. On the other hand, this T50 value was ca. 25 °C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

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Catalytic Neutralization of Naphthenic Acid from Petroleum Crude Oil by Using Cerium Oxide Catalyst and 2- Methylimidazole in Polyethylene Glycol

Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) ◽

10.2174/2405520413999200819171315 ◽

2020 ◽

Vol 13 ◽

Author(s):

Norshahidatul Akmar Mohd Shohaimi ◽

Norfakhriah Jelani ◽

Ahmad Zamani Ab Halim ◽

Nor Hakimin Abdullah ◽

Nurasmat Mohd Shukri

Keyword(s):

Polyethylene Glycol ◽

Crude Oil ◽

Cerium Oxide ◽

Active Sites ◽

Naphthenic Acid ◽

Naphthenic Acids ◽

Catalyst Loading ◽

High Concentration ◽

Oil Refineries ◽

Al2o3 Catalyst

: The presence of relatively high naphthenic acid in crude oil may contribute to the major corrosion in oil pipelines and distillation units in crude oil refineries. Thus, high concentration Naphthenic Acids crude oil is considered tobe of low quality and is marketed at lower prices. In order to overcome this problem, neutralization method had been developed to reduce the TAN value in crude oil. In this study, crude oil from Petronas Penapisan Melaka was investigated. The parameters studied were reagent concentration, catalyst loading, calcination temperature and reusability of the potential catalyst. Basic chemical used were 2- methylimidazole in polyethylene glycol (PEG 600) with concentration 100, 500 and 1000 ppm. Cerium oxide-based catalysts supported onto alumina prepared with different calcination temperatures. The catalyst was characterized by using Brunauer-Emmett-Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry Analysis-Differential Thermal Gravity (TGA-DTG) to study physical properties of the catalyst. The Ce/Al2O3 catalyst calcined at 1000°C was the best catalyst due to larger surface area formation which lead to increment of active sites thus will boost the catalytic activity. The result showed that the Ce/Al2O3 catalyst meet Petronas requirement as the TAN value reduced to 0.6 mgKOH/g from original TAN value of 4.22 mgKOH/g. The best reduction of TAN was achieved by using catalyst loading of 0.39% and reagent of 1000 ppm.

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Oscillatory Behaviour of Ni Supported on ZrO2 in the Catalytic Partial Oxidation of Methane as Determined by Activation Procedure

Materials ◽

10.3390/ma14102495 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2495

Author(s):

Daniela Pietrogiacomi ◽

Maria Cristina Campa ◽

Ida Pettiti ◽

Simonetta Tuti ◽

Giulia Luccisano ◽

...

Keyword(s):

Catalytic Activity ◽

Partial Oxidation ◽

Active Sites ◽

Direct Reduction ◽

Partial Oxidation Of Methane ◽

Catalytic Partial Oxidation ◽

Oxidation Of Methane ◽

Short Contact Time ◽

Oxidation Reduction ◽

Ni Species

Ni/ZrO2 catalysts, active and selective for the catalytic partial oxidation of methane to syngas (CH4-CPO), were prepared by the dry impregnation of zirconium oxyhydroxide (Zhy) or monoclinic ZrO2 (Zm), calcination at 1173 K and activation by different procedures: oxidation-reduction (ox-red) or direct reduction (red). The characterization included XRD, FESEM, in situ FTIR and Raman spectroscopies, TPR, and specific surface area measurements. Catalytic activity experiments were carried out in a flow apparatus with a mixture of CH4:O2 = 2:1 in a short contact time. Compared to Zm, Zhy favoured the formation of smaller NiO particles, implying a higher number of Ni sites strongly interacting with the support. In all the activated Ni/ZrO2 catalysts, the Ni–ZrO2 interaction was strong enough to limit Ni aggregation during the catalytic runs. The catalytic activity depended on the activation procedures; the ox-red treatment yielded very active and stable catalysts, whereas the red treatment yielded catalysts with oscillating activity, ascribed to the formation of Niδ+ carbide-like species. The results suggested that Ni dispersion was not the main factor affecting the activity, and that active sites for CH4-CPO could be Ni species at the boundary of the metal particles in a specific configuration and nuclearity.

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Partial Oxidation of Methane to Syngas over Monolithic Ni/γ-Al2O3 Catalyst——Effects of Rare Earths and Other Basic Promoters

Journal of Rare Earths ◽

10.1016/s1002-0721(06)60142-7 ◽

2006 ◽

Vol 24 (4) ◽

pp. 451-455 ◽

Cited By ~ 22

Author(s):

Di Ma ◽

Dajiang Mei ◽

Xuan Li ◽

Maochu Gong ◽

Yaoqiang Chen

Keyword(s):

Partial Oxidation ◽

Rare Earths ◽

Partial Oxidation Of Methane ◽

Oxidation Of Methane ◽

Al2o3 Catalyst

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Heterogeneous Catalytic Synthesis of 2-Methylbenzimidazole from 2-Nitroaniline and Ethanol Over Mg Modified Cu-Pd/γ-Al2O3

Catalysts ◽

10.3390/catal9010008 ◽

2018 ◽

Vol 9 (1) ◽

pp. 8 ◽

Cited By ~ 4

Author(s):

Feng Feng ◽

Yaqin Deng ◽

Zheng Cheng ◽

Xiaoliang Xu ◽

Qunfeng Zhang ◽

...

Keyword(s):

Active Sites ◽

Hydrogen Transfer ◽

High Efficiency ◽

Simple Procedure ◽

Direct Synthesis ◽

Reaction System ◽

Simple Method ◽

Heterogeneous Catalytic ◽

Coupled Reaction ◽

Al2o3 Catalyst

The direct synthesis of benzimidazoles from 2-nitroaniline and ethanol over Cu-Pd/γ-Al2O3 catalysts has the advantages of requiring easily available starting materials, having high efficiency, and a simple procedure. The modification by Mg of the Cu-Pd/γ-Al2O3 catalyst could improve the catalytic activity significantly. The addition of Mg to the Cu-Pd/γ-Al2O3 catalyst could maintain and promote the formation of CuPd alloy active sites. Meanwhile, the basicity of the support was enhanced appropriately by Mg, which generated more basic sites (Al-Oδ−) to accelerate the dehydrogenation of alcohol and increased the rate of the whole coupled reaction. The 2-nitroaniline was completely converted over Cu-Pd/(Mg)γ-Al2O3 after reacting for six hours, and the yield of 2-methylbenzimidazole was 98.8%. The results of this work provide a simple method to develop a more efficient catalyst for the “alcohol-dehydrogenation, hydrogen transfer and hydrogenation” coupled reaction system.

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Influence of incorporating a small amount of silica on the catalytic performance of a MoO3/Al2O3 catalyst in ethanol oxidative dehydrogenation

Journal of Applied Research and Technology ◽

10.22201/icat.16656423.2018.16.6.746 ◽

2018 ◽

Vol 16 (6) ◽

Cited By ~ 1

Author(s):

Aline Villarreal ◽

Gabriella Garbarino ◽

Paola Riani ◽

Aida Gutiérrez Alejandre ◽

Jorge Ramírez ◽

...

Keyword(s):

Oxidative Dehydrogenation ◽

Active Sites ◽

Catalytic Performance ◽

Redox Behavior ◽

Acid Base ◽

Pure Alumina ◽

Molybdenum Catalyst ◽

Al2o3 Catalyst ◽

Dehydrogenation Of Ethanol

The influence of incorporating a small amount of silica on the catalytic performance of MoO3/Al2O3 catalyst was studied. Molybdenum supported on pure alumina and 5% SiO2-Al2O3 supports were synthesized. The catalysts were characterized by XRD, Raman, UV-Vis and IR spectroscopies, FE-SEM microscopy, and their activity was evaluated in the oxidative dehydrogenation of ethanol to acetaldehyde. Molybdenum supported on pure alumina gives a 74% yield to acetaldehyde (at 573 K) due to the generation of oxy-dehydrogenation active sites by molybdenum and to the decrement of the alumina dehydration sites. For the molybdenum catalyst supported on silica-containing alumina, the molybdenum species were displaced from the strongest alumina’s acid-base couples, located on nanoparticles edges, corners and defects, to weaker ones located on plane faces causing the rise of weakly bonded species with less active redox behavior.

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