scholarly journals A High-Throughput Screening Approach to Identify New Active and Long-Term Stable Catalysts for Total Oxidation of Methane from Gas-Fueled Lean–Burn Engines

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 159
Author(s):  
Thomas Lenk ◽  
Adrian Gärtner ◽  
Klaus Stöwe ◽  
Thomas Schwarz ◽  
Christian Breuer ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Flow Reactor ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Plug Flow ◽  
Exhaust Gas ◽  
Lean Burn ◽  
Total Oxidation ◽  
Oxidation Of Methane

A unique high-throughput approach to identify new catalysts for total oxidation of methane from the exhaust gas of biogas-operated lean-burn engines is presented. The approach consists of three steps: (1) A primary screening using emission-corrected Infrared Thermography (ecIRT). (2) Validation in a conventional plug flow gas phase reactor using a model exhaust gas containing CH4, O2, CO, CO2, NO, NO2, N2O, SO2, H2O. (3) Ageing tests using a simplified exhaust gas (CH4, O2, CO2, SO2, H2O). To demonstrate the efficiency of this approach, one selected dataset with a sol-gel-based catalysts is presented. Compositions are 3 at.% precious metals (Pt, Rh) combined with different amounts of Al, Mn, and Ce in the form of mixed oxides. To find new promising materials for the abatement of methane, about two thousand different compositions were synthesized and ranked using ecIRT, and several hundred were characterized using a plug flow reactor and their ageing behaviour was determined.

High-Throughput Screening Approach to Identify New Catalysts for Total Oxidation of Methane from Gas Fueled Lean Burn Engines

2016 ◽  
Vol 59 (10-12) ◽  
pp. 1071-1075 ◽  
Author(s):  
Adrian Gärtner ◽  
Thomas Lenk ◽  
Rainer Kiemel ◽  
Santiago Casu ◽  
Christian Breuer ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Lean Burn ◽  
Total Oxidation ◽  
Oxidation Of Methane ◽  
Screening Approach ◽  
Gas Fueled

Design of a Flow Reactor for Testing Multi-Brick Catalyst Systems Using Rapid Exhaust Gas Composition Switches

2009 ◽  
Author(s):  
Stefan Klinkert ◽  
John W. Hoard ◽  
Sakthish R. Sathasivam ◽  
Dennis N. Assanis ◽  
Stanislav V. Bohac
Keyword(s):  
Flow Reactor ◽  
Combustion Engine ◽  
Synergistic Effects ◽  
Control Program ◽  
Exhaust Gas ◽  
Gas Composition ◽  
Lean Burn ◽  
Exhaust Gas Aftertreatment ◽  
Scr Catalysts ◽  
Catalyst Systems

In recent years, diesel exhaust gas aftertreatment has become a core combustion engine research subject because of both increasingly stringent emission regulations and incentives toward more fuel-efficient propulsion systems. Lean NOX traps (LNT) and selective catalytic reduction (SCR) catalysts represent two viable pathways for the challenging part of exhaust gas aftertreatment of lean burn engines: NOX abatement. It has been found that the combination of LNT and SCR catalysts can yield synergistic effects. Switches in the operation mode of the engine, temporarily enriching the mixture, are required to regenerate the LNT catalyst and produce ammonia for the SCR. This paper describes the design of a catalyst flow reactor that allows studying multi-brick catalyst systems using rapid exhaust gas composition switches and its initial validation. The flow reactor was designed primarily to study the potential of combining different aftertreatment components. It can accommodate two sample bricks at a time in two tube furnaces, which allows for independent temperature control. Moreover, the flow reactor allows for very flexible control of the composition and flow rate of the synthetic exhaust, which is blended using mass flow controllers. By using a two-branch design, very fast switches between two exhaust gas streams, as seen during the regeneration process of a LNT catalyst, are possible. The flow reactor utilizes a variety of gas analyzers, including a 5-Hz FTIR spectrometer, an emissions bench for oxygen and THC, a hydrogen mass spectrometer, and gas chromatographs for HC speciation. An in-house control program allows for data recording, flow reactor control, and highly flexible automation. Additionally, the hardware and software incorporate features to ensure safe testing. The design also has provisions for engine exhaust sampling.

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

Catalysts ◽  
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.

Modeling the Formation of Pollutant Emissions in Large-Bore, Lean-Burn Gas Engines

2017 ◽  
Author(s):  
Anamol Pundle ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
Joel D. Hiltner
Keyword(s):  
Partial Oxidation ◽  
Flow Reactor ◽  
Batch Reactor ◽  
Plug Flow ◽  
Chemical Reactor ◽  
Chemical Kinetic ◽  
Pollutant Emissions ◽  
Lean Burn ◽  
Reciprocating Engines ◽  
Stroke Engine

This paper discusses chemical kinetic modeling used to analyze the formation of pollutant emissions in large-bore, lean-burn gas reciprocating engines. Pollutants considered are NOx, CO, HCHO, and UHC. A quasi-dimensional model, built as a chemical reactor network (CRN), is described. In this model, the flame front is treated as a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR), and reaction in the burnt gas is modeled assuming a batch reactor of constant-pressure and fixed-mass for each crank angle increment. The model treats full chemical kinetics. Engine heat loss is treated by incorporating the Woschni model into the CRN. The mass burn rate is selected so that the modeled cylinder pressure matches the experiment pressure trace. Originally, the model was developed for large, low speed, two-stoke, lean-burn engines. However, recently, the model has been formatted for the four-stroke, open-chamber, lean-burn engine. The focus of this paper is the application of the model to a four-stroke engine. This is a single-cylinder non-production variant of a heavy duty lean-burn engine of about 5 liters cylinder displacement Engine speed is 1500 RPM. Key findings of this work are the following. 1) Modeled NOx and CO are found to agree closely with emission measurements for this engine over a range of relative air-fuel ratios tested. 2) This modeling shows the importance of including N2O chemistry in the NOx calculation. For λ = 1.7, the model indicates that about 30% of the NOx emitted is formed by the N2O mechanism, with the balance from the Zeldovich mechanism. 3) The modeling shows that the CO and HCHO emissions arise from partial oxidation late in the expansion stroke as unburned charge remaining mixes into the burnt gas. 4) Model generated plots of HCHO versus CH4 emission for the four-stroke engine are in agreement with field data for large-bore, lean-burn, gas reciprocating engines. Also, recent engine tests show the correlation of UHC and CO emissions to crevice volume. These tests suggest that HCHO emissions also are affected by crevice flows through partial oxidation of UHC late in the expansion stroke.

Encapsulated Biomolecules Using Sol-Gel Reaction for High-Throughput Screening

2012 ◽  
pp. 273-294
Author(s):  
Kumiko Sakai-Kato ◽  
Masaru Kato ◽  
Naoko Utsunomiya-Tate ◽  
Toshimasa Toyo'oka
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Sol Gel

The Role of Carbon Monoxide in NO2 Plume Formation

2000 ◽  
Vol 122 (2) ◽  
pp. 287-292 ◽  
Author(s):  
Alan S. Feitelberg ◽  
Sanjay M. Correa
Keyword(s):  
Carbon Monoxide ◽  
Chemical Reactions ◽  
Gas Turbines ◽  
Flow Reactor ◽  
Large Diameter ◽  
Plug Flow ◽  
No Oxidation ◽  
Exhaust Gas ◽  
Oxidation Of Co ◽  
Elementary Chemical

Through a series of computational studies, carbon monoxide has been identified as an important promoter of NO oxidation to NO2 in combustion turbine exhaust gas at intermediate temperatures (450 to 750°C). NO2 formation is accompanied by enhanced CO burnout at these temperatures. Perfectly stirred reactor and plug flow reactor calculations indicate that concentrations of CO as low as 50 ppmv in exhaust gas containing 25 ppmv NO can result in the conversion of 50 percent of the NO to NO2 in less than 1 s. NO2 concentrations as low as 15 ppmv can result in visible, yellow-brown plumes from large diameter exhaust stacks. If NO2 plumes are to be prevented, then designers of gas turbines and heat recovery steam generators need to be aware of the relationships between time, temperature, and composition which cause NO2 to form in exhaust gas. Reaction path analysis indicates that the mutually promoted oxidation of CO and NO occurs through a self-propagating, three-step chain reaction mechanism. CO is oxidized by OH CO+OH→CO2+H, while NO is oxidized by HO2:NO+HO2→NO2+OH. In a narrow temperature range, the H-atom produced by the first reaction can react with O2 in a three body reaction to yield the hydroperoxy radical needed in the second reaction: H+O2+M→HO2+M, where M is any third body. The observed net reaction is CO+O2+NO→CO2+NO2, which occurs stoichiometrically at temperatures below about 550°C. As the temperature increases, additional reaction pathways become available for H, HO2, and OH which remove these radicals from the chain and eventually completely decouple the oxidation of CO from NO. An abbreviated set of elementary chemical reactions, including 15 species and 33 reactions, has been developed to model CO-enhanced oxidation of NO to NO2. This reaction set was derived from a larger reaction set with more than 50 species and 230 elementary chemical reactions, and was validated by comparison of PSR and PFR calculations using the two sets. [S0742-4795(00)01402-2]

Combinatorial Search for Low-Temperature Combustion Catalysts

2003 ◽  
Vol 804 ◽  
Author(s):  
Tina Wolter ◽  
Wilhelm F. Maier
Keyword(s):  
Catalytic Activity ◽  
Flow Reactor ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Methane Combustion ◽  
Low Temperature Combustion ◽  
Combinatorial Search ◽  
Sol Gel Process ◽  
Temperature Combustion ◽  
Lean Conditions

ABSTRACTA sol-gel process was used to synthesize potential combustion catalysts based on mixed oxides on several libraries. As mixed oxides a variety of doped Zr-Al-oxides and Ce-oxides were prepared. The catalytic activity of the materials was tested with the combustion of i-octane, n-butane and methane in synthetic air. Several Pt- and Rh-containing sol-gel materials showed effective methane combustion already at 60 °C under rich conditions and at 200 °C under lean conditions. Several noble metal free doped CeO2 catalysts combusted methane already at 300 °C under lean conditions. Combustion of i-octane was catalysed already at 125 °C. The most active catalysts were synthesized conventionally, characterized and catalytic activity was confirmed in a regular gas phase flow reactor.

Oxidation of Natural Gas, Natural Gas/Syngas Mixtures, and Effect of Burnt Gas Recirculation: Experimental and Detailed Kinetic Modeling

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
T. Le Cong ◽  
P. Dagaut ◽  
G. Dayma
Keyword(s):  
Natural Gas ◽  
Kinetic Modeling ◽  
Flow Reactor ◽  
Plug Flow ◽  
Chemical Kinetic ◽  
Reaction Scheme ◽  
Fused Silica ◽  
Kinetic Reaction ◽  
Oxidation Of Methane ◽  
Wide Range

The oxidation of methane-based fuels was studied experimentally in a fused-silica jet-stirred reactor (JSR) operating at 1–10atm, over the temperature range of 900–1450K, from fuel-lean to fuel-rich conditions. Similar experiments were performed in the presence of carbon dioxide or syngas (CO∕H2). A previously proposed kinetic reaction mechanism updated for modeling the oxidation of hydrogen, CO, methane, methanol, formaldehyde, and natural gas over a wide range of conditions including JSR, flame, shock tube, and plug flow reactor was used. A detailed chemical kinetic modeling of the present experiments was performed yielding a good agreement between the modeling, the present data and literature burning velocities, and ignition data. Reaction path analyses were used to delineate the important reactions influencing the kinetic of oxidation of the fuels in the presence of variable amounts of CO2. The kinetic reaction scheme proposed helps understand the effect of the additives on the oxidation of methane.

Sign in / Sign up

Export Citation Format

Share Document