Abatement Of Methane Emissions Research Articles

Optimization of Non-thermal Plasma-Assisted Catalytic Oxidation for Methane Emissions Abatement as an Exhaust Aftertreatment Technology

While methane-powered vehicles produce fewer greenhouse gas emissions in comparison to conventional fuel vehicles, there is a significant amount of methane slip in their exhaust that needs to be treated. This study investigates non-thermal plasma (NTP) assisted catalytic methane oxidation as an alternative method for the low temperature methane slip abatement applicable to the exhaust of biogas methane-powered vehicles. It is concluded that high CH4 conversion and CO2 selectivity can be obtained using NTP-catalysis at low temperature with Pd/Al2O3 found to be the most promising candidate among all catalysts tested. In addition, it was found that CH4 conversion efficiency was dependent on the feed gas components and gas hourly space velocity as well as how the activation energy is introduced. For example, a combination of plasma and external heat supply provides advantages in terms of CH4 conversion along with lower plasma energy consumption. The presence of N2 and O2 in the feed gas during NTP-catalytic methane oxidation results in unfavourable NOX formation which linearly increases with CH4 conversion. These results conclude that the most suitable aftertreatment option involves the combination of an oxidation catalyst with plasma to target the hydrocarbon and CH4 oxidation, followed by an ammonia-SCR system to convert the NOX formed in plasma assisted zone.

New Insight into the Interplay of Method of Deposition, Chemical State of Pd, Oxygen Storage Capability and Catalytic Activity of Pd-Containing Perovskite Catalysts for Combustion of Methane

Elaboration of Pd-supported catalysts for catalytic combustion is, nowadays, considered as an imperative task to reduce the emissions of methane. This study provides new insight into the method of deposition, chemical state of Pd and oxygen storage capability of transition metal ions and their effects on the catalytic reactivity of supported catalysts for the combustion of methane. The catalyst with nominal composition La(Co0.8Ni0.1Fe0.1)0.85Pd0.15O3 was supported on SiO2-modified/γ-alumina using two synthetic procedures: (i) aerosol assisted chemical vapor deposition (U-AACVD) and (ii) wet impregnation (Imp). A comparative analysis shows that a higher catalytic activity is established for supported catalyst obtained by wet impregnation, where the PdO-like phase is well dispersed and the transition metal ions display a high oxygen storage capability. The reaction pathway over both catalysts proceeds most probably through Mars–van Krevelen mechanism. The supported catalysts are thermally stable when they are aged at 505 °C for 120 h in air containing 1.2 vol.% water vapor. Furthermore, the experimentally obtained data on La(Co0.8Ni0.1Fe0.1)0.85Pd0.15O3—based catalyst, supported on monolithic substrate VDM®Aluchrom Y Hf are simulated by using a two-dimensional heterogeneous model for monolithic reactor in order to predict the performance of an industrial catalytic reactor for abatement of methane emissions.

Design, characterization and evaluation of Ce-modified cobalt catalysts supported on alpha alumina in the abatement of methane emissions from natural gas engines

This work deals with the optimisation of Ce-promoted Co3O4 catalysts supported on alpha alumina for the oxidation of traces amounts of methane. Ten Co-Ce samples were synthesised by incipient wetness coimpregnation with the aim of analysing the influence of the Ce/Co molar ratio and the Co3O4 loading on the physico-chemical properties and resultant catalytic behaviour. Textural, structural, morphological and redox properties along with bulk/surface composition were thoroughly characterised. Lattice distortion provoked by insertion of controlled amounts of Ce increased the abundance of Co3+ and improved consequently the redox properties and the mobility of lattice oxygen species of the Co-Ce catalysts. Analysis of kinetic data in the 200−600 °C temperature range evidenced that the optimal catalyst formulation was 10 %Co3O4wt. with a Ce/Co molar ratio of 0.05. In addition, this sample showed a reasonable stability with time on stream under cycled dry/humid conditions.

Impacts of sulfanilamide and oxytetracycline on methane oxidation and methanotrophic community in freshwater sediment.

Methanotrophs are of great significance for the abatement of methane emission from anoxic environments. Antibiotics are ubiquitous in the environment and can affect microbial activity and community density and composition. However, information about the effect of antibiotics on methanotrophs is still lacking. The current study explored the influences of sulfonamides and tetracyclines on methane oxidation potential (MOP) and methanotrophic density and community structure in freshwater sediment microcosms. The addition of both sulfanilamide (SA) and oxytetracycline (OTC) could increase MOP and particulate methane monooxygenase subunit A (pmoA) gene density but decrease the number of pmoA transcripts. Both SA and OTC could also have impacts on sediment methanotrophic community structure. The antibiotic effects on MOP and methanotrophs were found to depend on the dosage and type of antibiotics. This work could provide some new insights towards the links between methane oxidation and antibiotics.

N-Doped Carbon–Silica Composite Confined Pd Nanoparticles for Abatement of Methane Emission From Automobiles

Natural gas vehicles, as well as some other engines in automobiles, emit methane, which is a potent greenhouse gas. Developing advanced catalysts that can oxidize methane with good and stable activity is required for new emission standards of automobiles. We report here a N-doped carbon–silica composite that can well disperse Pd nanoparticles and preserve part of active Pd nanoparticles (< 8 nm) under typical conditions of exhaust gas from a working engine. Comparative studies indicate a stronger metal-support interaction between Pd nanoparticle and N-doped carbon (NC) than none N-doped carbon. A facile silica coating is formed from SiCl4 in water vapor. The silica coating encapsulates Pd/NC and prevents extreme Pd sintering. The Pd catalyst with N-doped carbon–silica composite, i.e. (Pd/NC)@SiO2, performs stable and complete conversion of 5000 ppm CH4 to CO2 and H2O at 350 °C with a space velocity of 40,000 cm3 per gram of catalyst per hour. This research illustrates the advantage of using N-doped carbons supported catalyst for methane oxidation. Future optimization could be attempted by improving the thermal stability of carbons at the reaction conditions.

System-wide and Superemitter Policy Options for the Abatement of Methane Emissions from the U.S. Natural Gas System.

This work assesses trade-offs between system-wide and superemitter policy options for reducing methane emissions from compressor stations in the U.S. transmission and storage system. Leveraging recently collected national emissions and activity data sets, we developed a new process-based emissions model implemented in a Monte Carlo simulation framework to estimate emissions for each component and facility in the system. We find that approximately 83% of emissions, given the existing suite of technologies, have the potential to be abated, with only a few emission categories comprising a majority of emissions. We then formulate optimization models to determine optimal abatement strategies. Most emissions across the system (approximately 80%) are efficient to abate, resulting in net benefits ranging from $160M to $1.2B annually across the system. The private cost burden is minimal under standard and tax instruments, and if firms market the abated natural gas, private net benefits may be generated. Superemitter policies, namely, those that target the highest emitting facilities, may reduce the private cost burden and achieve high emission reductions, especially if emissions across facilities are highly skewed. However, detection across all facilities is necessary regardless of the policy option and there are nontrivial net benefits resulting from abatement of relatively low-emitting sources.

Modeling the impact of mitigation options on abatement of methane emission from livestock

Mitigation of methane emission from livestock sector is crucial to combat the menace of global warming. In the present paper, a nonlinear mathematical model is proposed to investigate the impact of mitigation options, for curtailing livestock methane emission, on the reduction of atmospheric concentration of methane. In modeling process, it is assumed that the mitigation options are applied at a rate proportion to the livestock population. The conditions for reduction and stabilization of atmospheric methane have been obtained. Numerical simulation has been performed to verify the analytical findings by taking the secondary data of atmospheric concentration of methane, human and livestock populations. Sensitivity analysis is carried out to explore the impact of the key parameters of the model system.

In situ regeneration of Rhodium in three-way catalysts by aqueous ethanol injection for sustained methane emissions abatement

We are reporting an initial feasibility study addressing the abatement of methane emissions from stoichiometric natural gas fueled vehicles. The injection of a small amount of aqueous ethanol or propane into the exhaust enables the catalytic abatement of methane by the Rh-containing three-way catalyst (TWC). The Rh component experiences oxidation to inactive Rh3+ when the engine operates during the fuel shutoff mode raising the catalyst temperature to over 1000°C. Upon returning to normal driving operation, under a slightly fuel rich condition, the methane will not reform leading to permanent deactivation of the Rh. Injecting an aqueous ethanol solution or gaseous propane catalytic steam reforming occurs and the H2 generated reduces the Rh3+ to its metallic and active state for CH4 steam reforming. This paper presents a laboratory feasibility study for in situ catalyst regeneration of Rh3+ to Rh metal using a secondary injected fuel (ethanol or propane), enabling sustained catalyst performance in methane emissions abatement.

Diffuse methane emissions abatement by organic and inorganic packed biofilters: Assessment of operational and environmental indicators

This paper aims at quantifying the most relevant technological and environmental indicators associated with the operation of organic and inorganic packed biofilters treating diffuse methane emissions. The use of different packing materials including a mixture of pine bark, perlite and compost for the organic biofilter and polyurethane foam for the inorganic one was evaluated. The influence of other major variables on the removal efficiency such as nutrient requirements, operational conditions and long-term stability were also assessed in both configurations. The analysis of the biofilters operation proved that both configurations provided a feasible and stable performance in the treatment of diffuse methane emissions.Once the operational feasibility of both systems was proved, the environmental assessment was performed. The main hotspots found in the analysis were attributed to the requirement of nutrients, infrastructure, waste disposal and direct emissions to the atmosphere. A sensitivity analysis was performed in terms of nutrient supply and infrastructure material which revealed that special attention needs to be paid to the formulation of the nutrient solution in terms of concentration and source of nitrogen.

English

English

Coal mine ventilation air methane combustion in a catalytic reverse flow reactor: Influence of emission humidity

The role of the humidity content on the performance of catalytic reverse flow reactors (RFRs) for the abatement of methane emissions from coal mines is studied in this manuscript. It has been demonstrated that this technique is very useful for the abatement, and even upgrading, of these emissions. However, the effect of humidity on the reactor performance has not been addressed yet, in spite of being well known that water is an inhibitor in catalytic combustion.Experimental studies in a lab-scale isothermal fixed bed reactor demonstrated that water decreases the activity of a palladium on alumina catalyst for the combustion of methane, but this inhibition is entirely reversible, results fitting well to a Langmuir–Hinshelwood kinetic model. Then, the influence of water was studied in a bench-scale RFR operating at near adiabatic conditions at different switching times (100–600s) and methane feed concentrations (2700–7200ppm). Finally, a mathematical model for the reverse flow reactor, including the kinetic model with water inhibition, has been validated using the experimental results. This model is of key importance for designing this type of reactors for the treatment of mine ventilation emissions.

Mitigation strategies for enteric methane emission with special emphasis on biological approaches: A review

Atmospheric concentration methane is almost 1782 ppb, which is 155% higher than its pre industrial concentration. Agricultural sector dispensing a consequential amount of methane (about 2/3rd of total anthropogenic); livestock rearing generates 7–12 Tg methane annually from the country. The methane generation from ruminants not only contributes significantly to global warming but also leads a loss of dietary energy (7–12% of GEI). This loss needs attention, where acute shortage of quality feeds prevails. Efforts were made in the past to control the enteric methane emission using customary feeding approaches including chemicals and methane analogues, but most of them dubitable with one or more critical limitations like few respond at high doses, toxicity to either host animal or inhabited synergistic microbes etc. Therefore, the search for suitable, effective and safe methane mitigating agent is still ongoing, and extensive screenings of newer strategies are on radar of animal nutritionist and microbiologists in association with biotechnologists for abatement of methane emission from ruminants. This review paper examines the biological approaches such as reductive acetogenesis, immunization, phage therapy, defaunation, disabling the protein bindings accountable for association of methanogens with other microorganisms in rumen. In conclusion, there is the foremost need to explore the potentialities of state-of-the-art biological approaches under in vivo and with topographical variations.

Some Prophylactic Options to Mitigate Methane Emission from Animal Agriculture in Japan

The abatement of methane emission from ruminants is an important global issue due to its contribution to greenhouse gas with carbon dioxide. Methane is generated in the rumen by methanogens (archaea) that utilize metabolic hydrogen () to reduce carbon dioxide, and is a significant electron sink in the rumen ecosystem. Therefore, the competition for hydrogen used for methanogenesis with alternative reductions of rumen microbes should be an effective option to reduce rumen methanogenesis. Some methanogens parasitically survive on the surface of ciliate protozoa, so that defaunation or decrease in protozoa number might contribute to abate methanogenesis. The most important issue for mitigation of rumen methanogenesis with manipulators is to secure safety for animals and their products and the environment. In this respect, prophylactic effects of probiotics, prebiotics and miscellaneous compounds to mitigate rumen methanogenesis have been developed instead of antibiotics, ionophores such as monensin, and lasalocid in Japan. Nitrate suppresses rumen methanogenesis by its reducing reaction in the rumen. However, excess intake of nitrate causes intoxication due to nitrite accumulation, which induces methemoglobinemia. The nitrite accumulation is attributed to a relatively higher rate of nitrate reduction to nitrite than nitrite to ammonia via nitroxyl and hydroxylamine. The in vitro and in vivo trials have been conducted to clarify the prophylactic effects of L-cysteine, some strains of lactic acid bacteria and yeast and/or 1-4 galactooligosaccharide on nitrate-nitrite intoxication and methanogenesis. The administration of nitrate with 1-4 galacto-oligosaccharide, Candida kefyr, and Lactococcus lactis subsp. lactis were suggested to possibly control rumen methanogenesis and prevent nitrite formation in the rumen. For prebiotics, nisin which is a bacteriocin produced by Lactococcus lactis subsp. lactis has been demonstrated to abate rumen methanogenesis in the same manner as monensin. A protein resistant anti-microbe (PRA) has been isolated from Lactobacillus plantarum as a manipulator to mitigate rumen methanogenesis. Recently, hydrogen peroxide was identified as a part of the manipulating effect of PRA on rumen methanogenesis. The suppressing effects of secondary metabolites from plants such as saponin and tannin on rumen methanogenesis have been examined. Especially, yucca schidigera extract, sarsaponin (steroidal glycosides), can suppress rumen methanogenesis thereby improving protein utilization efficiency. The cashew nutshell liquid (CNSL), or cashew shell oil, which is a natural resin found in the honeycomb structure of the cashew nutshell has been found to mitigate rumen methanogenesis. In an attempt to seek manipulators in the section on methane belching from ruminants, the arrangement of an inventory of mitigation technologies available for the Clean Development Mechanism (CDM) and Joint Implementation (JI) in the Kyoto mechanism has been advancing to target ruminant livestock in Asian and Pacific regions.

Methane Emissions Abatement by Multi-Ion-Exchanged Zeolite A Prepared from Both Commercial-Grade Zeolite and Coal Fly Ash

The performance of multimetal-(Cu, Cr, Zn, Ni, and Co)-ion-exchanged zeolite A prepared from both a commercial-grade sample and one produced from coal fly ash in methane emissions abatement was evaluated in this study. The ion-exchange process was used to load the metal ions in zeolite A samples. The methane conversion efficiency by the samples was studied under various parameters including the amount of metal loading (7.3-19.4 wt%), reaction temperature (25-500 degrees C), space velocity (8400-41 900 h(-1)), and methane concentration (0.5-3.2 vol %). At 500 degrees C, the original commercial-grade zeolite A catalyzed 3% of the methane only, whereas the addition of different percentages of metals in the sample enhanced the methane conversion efficiency by 40-85%. Greater methane conversion was observed by increasing the percentage of metals added to the zeolite even though the BET surface area of the zeolite consequently decreased. Higher percentage methane conversion over the multi-ion-exchanged samples was observed at lower space velocities indicating the importance of the mass diffusion of reactants and products in the zeolite. Compared to the multi-ion-exchanged zeolite A prepared from the commercial-grade zeolite, the one produced from coal fly ash demonstrated similar performances in methane emissions abatement, showing the potential use of this low cost recycled material in gaseous pollutant treatment.

Use of multi-transition-metal-ion-exchanged zeolite 13X catalysts in methane emissions abatement

Methane is a potent greenhouse gas. It has a global warming potential (GWP) 23 times greater than carbon dioxide. Reducing methane emissions would lead to substantial economic and environmental benefits. This study investigated the performance of multi-transition-metal-(Cu, Cr, Ni, and Co)-ion-exchanged zeolite 13X catalysts in methane emissions abatement. The catalytic activity in methane combustion using multi-ion-exchanged catalysts was studied with different parameters including the molar percentage of metal loading, the space velocity, and the inlet methane concentration under atmospheric pressure and at a relatively low reaction temperature of 500 °C. The performance of the catalysts was determined in terms of the apparent activation energy, the number of active sites of the catalyst, and the BET surface area of the catalyst. This study showed that multi-ion-exchanged catalysts outperformed single-ion-exchanged and acidified 13X catalysts and that lengthening the residence time led to a higher methane conversion percentage. The enhanced catalytic activity in the multi-ion-exchanged catalysts was attributed to the presence of exchanged transition ions instead of acid sites in the catalyst. The catalytic activity of the catalysts was influenced by the metal loading amount, which played an important role in affecting the apparent activation energy for methane combustion, the active sites, and the BET surface area of the catalyst. Increasing the amount of metal loading in the catalyst decreased the apparent activation energy for methane combustion and also the BET surface area of the catalyst. An optimized metal loading amount at which the highest catalytic activity was observed due to the combined effects of the various factors was determined.

Regeneration of S-poisoned Pd/Al 2O 3 catalysts for the combustion of methane

Regeneration of S-poisoned Pd/Al 2O 3 catalysts for the abatement of methane emissions from natural gas vehicles was addressed in this work. Investigations were devoted to determine the temperature threshold allowing for catalyst reactivation under different CH 4 containing atmospheres. Under lean combustion conditions in the presence of excess O 2, partial regeneration took place only above 750 °C after decomposition of stable sulphate species adsorbed on the support. Short CH 4-reducing, O 2-free pulses led to partial catalyst reactivation already at 550 °C and to practically complete regeneration at 600 °C. Also in this case reactivation was associated with SO 2 release due to the decomposition of stable support sulphates likely promoted by CH 4 activation onto the reduced metallic Pd surface. Rich combustion pulses with CH 4/O 2 = 2 were equally effective to CH 4-reducing pulses in catalyst regeneration. These results suggest that a regeneration strategy based on periodical natural gas pulses fed to the catalyst by a by-pass line might be efficient in limiting the effects of S-poisoning of palladium catalysts for the abatement of CH 4 emissions from natural gas engine.

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

Co3O4/CeO2 composite oxides with different cobalt loading (5, 15, 30, 50, 70wt.% as Co3O4) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co3O4 and CeO2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out.An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co3O4 in correspondence of Co3O4–CeO2 containing 30% by weight of Co3O4. The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co3O4 phase and promoting the efficiency of the Co3+–Co2+ redox couple. The presence in the sample Co3O4(30wt.%)–CeO2 of a high relative amount of Ce3+/(Ce4++Ce3+) as detected by XPS confirms the enhanced oxygen mobility.The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co3O4 phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750°C for 7h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co3O4 and Co3O4(30wt.%)–CeO2, performing the tests in the presence of 5vol.% H2O. A methane oxidation test upon hydrothermal ageing (flowing at 600°C for 16h a mixture 5vol.% H2O+5vol.%O2 in He) of the Co3O4(30wt.%)–CeO2 sample was also performed. All the results confirm the superiority of this composite oxide.

Palladium catalyst performance for methane emissions abatement from lean burn natural gas vehicles

As little as 1 ppm SO x present in the exhaust of a lean burn natural gas engine strongly inhibits the oxidation of CH 4 over a Pd containing catalyst. Non-methane emissions oxidation, such as C 2H 6, C 3H 8 and CO, are also inhibited by low SO x concentrations, but to a lesser extent than CH 4 emissions. The mechanism for SO x inhibition indicates a 1 : 1 selective adsorption of SO x on PdO for palladium on a non-sulfating support such as SiO 2. Deactivation is therefore very rapid. In contrast, palladium on sulfating supports, that is γ-Al 2O 3, deactivate more slowly and can tolerate more SO x because the SO x is also adsorbed onto the carrier. The activation energy for methane oxidation is dramatically increased after SO x poisoning for all Pd catalysts, while the Arrhenius pre-exponential term is relatively constant, indicating a transformation from very active PdO sites to less active PdO SO x sites. Platinum catalysts are considerably less active than Pd as evidenced by a much lower pre-exponential term, but are more resistant to deactivation by SO x . Non-methane hydrocarbon and particulate emissions standards for lean burn natural gas engines for the United States can be met with Pd catalysts. However, the non-enforced methane emissions standards are not met. For the European truck test cycle, methane emissions standards are met since the test cycle heavily weights the hotter modes where Pd SO x is sufficiently active.