High Carbon Monoxide Research Articles

Suppression of Methane Formation by Regulating the Hydrogenation Capability of Metal Oxides in Alkylation of Benzene with Syngas

In alkylation of benzene with syngas, the inevitable converting of syngas into methane, as a side reaction, severely hinders the effective utilization of carbon monoxide (CO), which is a major challenge to circumvent. In this work, a series of bifunctional catalysts composed of various zinc/zirconium/cerium metal oxides and HZSM-5 zeolite were prepared in order to explore the key factor of methane formation and achieve high CO efficiency. The results show that methane selectivity mostly depends on the hydrogenation capability, which can be regulated via altering compositions of the metal oxides. Combined with density functional theory calculation and characterizations, it is found that the hydrogenation capability of metal oxide is related to the energy barrier of hydrogen (H2) heterolysis. Compared to CeO2, the addition of zinc favors a lower energy barrier and a stronger ability toward H2 heterolysis, while the addition of zirconium makes this ability weaker. Too strong heterolysis capability consequently leads to excessive hydrogenation, which further causes high methane selectivity; however, too weak heterolysis capability will lead to low catalytic activity. Hence, proper hydrogenation capability is an important element for low methane selectivity and high catalytic activity. Our findings reveal the formation mechanism of methane and provide a new strategy to reduce methane content.

Pd-Nanoparticles Embedded Metal-Organic Framework-Derived Hierarchical Porous Carbon Nanosheets as Efficient Electrocatalysts for Carbon Monoxide Oxidation in Different Electrolytes.

Rational synthesis of Co-ZIF-67 metal-organic framework (MOF)-derived carbon-supported metal nanoparticles is essential for various energy and environmental applications; however, their catalytic activity toward carbon monoxide (CO) oxidation in various electrolytes is not yet emphasized. Co-ZIF-67-derived hierarchical porous carbon nanosheet-supported Pd nanocrystals (Pd/ZIF-67/C) were prepared using a simple microwave-irradiation approach followed by carbonization and etching. Mechanistically, during microwave irradiation, triethyleneamine provides abundant reducing gases that promote the formation of Pd nanoparticles/Co-Nx in porous carbon nanosheets with the assistance of ethylene glycol and also form a multimodal pore size. The electrocatalytic CO oxidation activity and stability of Pd/ZIF-67/C outperformed those of commercial Pd/C and Pt/C catalysts by (4.2 and 4.4, 4.0 and 2.7, 3.59 and 2.7) times in 0.1 M HClO4, 0.1 M KOH, and 0.1 M NaHCO3, respectively, due to the catalytic properties of Pd besides the conductivity of Co-Nx active sites and delicate porous structures of ZIF-67. Notably, using Pd/ZIF-67/C results in a higher CO oxidation activity than Pd/C and Pt/C. This study may pave the way for using MOF-supported multi-metallic nanoparticles for CO oxidation electrocatalysis.

High Resolution On-Road Air Pollution Using a Large Taxi-Based Mobile Sensor Network.

Traffic-related air pollution (TRAP) was monitored using a mobile sensor network on 125 urban taxis in Shanghai (November 2019/December 2020), which provide real-time patterns of air pollution at high spatial resolution. Each device determined concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), and PM2.5, which characterised spatial and temporal patterns of on-road pollutants. A total of 80% road coverage (motorways, trunk, primary, and secondary roads) required 80–100 taxis, but only 25 on trunk roads. Higher CO concentrations were observed in the urban centre, NO2 higher in motorway concentrations, and PM2.5 lower in the west away from the city centre. During the COVID-19 lockdown, concentrations of CO, NO2, and PM2.5 in Shanghai decreased by 32, 31 and 41%, compared with the previous period. Local contribution related to traffic emissions changed slightly before and after COVID-19 restrictions, while changing background contributions relate to seasonal variation. Mobile networks are a real-time tool for air quality monitoring, with high spatial resolution (~200 m) and robust against the loss of individual devices.

Analysis of source distribution of high carbon monoxide events using airborne and surface observations in Korea

Carbon monoxide (CO) is a key tracer of anthropogenic pollution, and it indirectly affects climate change. Anmyeon-do (AMY, 36.54° N, 126.33° E), a World Meteorological Organization/Global Atmosphere Watch Program (WMO/GAW) regional background station in Korea, provides continuous observations of CO mole fractions at the surface and vertical profiles within 0.5–9 km that are also collected by aircraft campaigns. The vertical profiles collected in 2019 were analyzed using meteorological parameters such as vertical velocity and boundary layer height (BLH), and a strong relationship was observed among them; however, the vertical distribution, which was influenced by unexpected strong pollution plumes, did not exhibit a strong relationship with vertical velocity and BLH. On November 16, we captured a strong CO signal within the boundary layer and at approximately 2 km above the BLH, where vertical profiles of the aerosol scattering coefficient at 550 nm were simultaneously observed with the same vertical structure. To identify the origins and source types of the stratification of the pollution plume for CO and aerosol, we also analyzed surface in situ observations of particle size distributions and reactive gases (NOx, O3, and SO2) as well as the column averaged dry-air mole fraction of carbon monoxide (XCO) and measurements of aerosol optical depth obtained from the tropospheric monitoring instrument (TROPOMI) and moderate resolution imaging spectroradiometer (MODIS) satellite, respectively. The high CO event within the BLH, including observations at the surface site, was attributed to domestic burning sources. Convective uplifting of industrial fossil fuel emissions from eastern China was responsible for the high CO dry mole fraction in the low free troposphere (FT) and the elevated aerosol scattering coefficient. Statistical analyses of one-year surface in situ observations of CO reveal that CO-emission sources from eastern China contributed to extremely high CO spikes (≥80th percentile of CO or ≥ 350 ppb, approximately) in 2019. Therefore, we concluded that emissions from eastern China have a potentially leading role in the observed high pollution events at the surface and the lower FT over the AMY station in 2019. The increase in ground temperature, with the acceleration of the global warming process, can intensify the convective uplifting of pollution plumes from emission source regions to FT over East Asian regions. In addition, such an occurrence of the stratification of the atmospheric pollution plume in the troposphere should be considered in future studies on radiative forcing to improve air-quality forecasting in this region.

Cover Feature: Theory‐Guided Machine Learning to Predict the Performance of Noble Metal Catalysts in the Water‐Gas Shift Reaction (ChemCatChem 16/2022)

The Cover Feature illustrates a theory-guided machine learning framework for water-gas shift reaction optimization. In their Research Article, J. Chattoraj, T. L. Tan and co-workers showed that purely data-driven models could violate the thermodynamic equilibrium principle as well as the models could predict non-physical carbon monoxide conversion percentage. They proposed a theory-guided machine learning model with a unique thermodynamic loss function to resolve these two problems. The proposed model showed promising reaction conditions, which could result in high carbon monoxide conversion rates. All the authors thank Zicong Marvin Wong for helping to design the cover picture. More information can be found in the Research Article by J. Chattoraj, T. L. Tan and co-workers.

Characteristics of atmospheric black carbon and other aerosol particles over the Arctic Ocean in early autumn 2016: Influence from biomass burning as assessed with observed microphysical properties and model simulations

We conducted ship-based measurements of marine aerosol particles (number concentration, size distribution, black carbon (BC), autofluorescence property, and PM2.5 composition) and trace gases (ozone (O3) and carbon monoxide (CO)) during a cruise of the R/V Mirai (23 August to 4 October 2016) over the Arctic Ocean, Northwest Pacific Ocean, and Bering Sea. Over the Arctic Ocean at latitudes >70°N, the averaged BC mass concentration was 0.7 ± 1.8 ng/m3, confirming the validity of our previously-reported observations (~1 ng/m3) over the same region during September 2014 and September 2015. The observed levels over the Arctic Ocean need to be used as a benchmark when testing the atmospheric transport models over the ocean, while they are substantially lower than those reported at Barrow (Utqiaġvik), a nearby ground-based station. We identified events with elevated BC mass concentrations and CO mixing ratios over the Arctic Ocean and Bering Sea as influenced by biomass burnings, with evidences from elevated levoglucosan levels, mixing states of BC particles, and particle size distributions. With WRF-Chem model simulations, we confirmed Siberian Forest fire plumes traveled over thousands of kilometers and produced substantially high BC and CO levels over the Bering Sea. The ΔBC/ΔCO ratios during these periods were estimated as ~1 ng/m3/ppbv, which are lower than those values reported, indicating that the results might have been affected by the wet removal process during transportation and/or by emission in smoldering conditions.

High-performance amperometric carbon monoxide sensor based on a xerogel-modified PtCr/C microelectrode

An amperometric biosensor based on a xerogel-modified PtCr/C microelectrode was developed for direct carbon monoxide (CO) detection. The effects of elemental Cr on the structural and electronic characteristics of the binary PtCr/C catalyst were characterized using various analytical techniques. Differential pulse voltammetry and amperometric measurements were performed to evaluate the electrocatalytic performance of the fabricated electrodes with respect to CO oxidation. The modified PtCr/C catalyst showed significantly improved electrocatalytic activity for CO oxidation, including a low applied potential of 0.3 V (vs. Ag/AgCl, high sensitivity of 12.5 nA μM−1 (standard deviation [SD] 0.52 nA μM−1)), excellent surface sensitivity of 726.6 nA μM−1 cm−2 (SD 30.4 nA μM−1 cm−2), and sufficiently high CO selectivity in the presence of other common metabolites. Modification of the PtCr/C-alloy catalyst surface with a fluorinated xerogel membrane minimized the effects of interfering species. Under optimal conditions, the xerogel-modified PtCr/C microelectrode exhibited a CO sensitivity of 8.82 nA μM−1 (SD 0.08 nA μM−1) and corresponding selectivity (logKCO,iamp) of < −5, −2.82 (SD 0.38), −3.16 (SD 0.03), − 2.57 (SD 0.05), −0.99 (SD 0.01), −2.02 (SD 0.01), and −1.79 (SD 0.05) for nitrite, ascorbic acid, uric acid, acetaminophen, dopamine, hydrogen peroxide, and nitric oxide. The xerogel-modified PtCr/C sensor was used to measure the CO directly generated on the surface of a living kidney in real time, and a CO concentration of 0.74 μM was estimated. Thus, our sensor can serve as a novel platform for developing high-performance electrochemical sensors suitable for practical applications.

Development of CO gas conversion system using high CO tolerance biocatalyst

Acetogenic bacteria (acetogens) are microorganisms with high potential as biocatalysts that can convert C1 gas, such as carbon dioxide (CO2) or carbon monoxide (CO), into biomass or biochemicals; however, high CO concentrations cause growth retardation in these microorganisms. In this study, we performed adaptive evolution of Eubacterium limosum, an acetogen, for approximately 400 generations under high CO synthetic gas (syngas) conditions to obtain E. limosum ECO2, which can rapidly proliferate even under high CO conditions. A mutation was revealed in H636R in the Acetyl-CoA synthase (ACS) protein of the ECO2 strain through whole-genome re-sequencing, and the mutation increased the CO gas conversion rate. By analyzing the transcript profiling of the ECO2 strain under high CO syngas conditions, the transcript levels of the methyl branch in the Wood–Ljungdahl pathway and the energy conservation system increased at high CO concentration conditions. Finally, to convert CO into value-added biochemicals, 2,3-BDO (2,3-butanediol) biosynthesis pathways were constructed and transformed into the E. limosum ECO2 strain. This strain showed capability to produce 2.60 mg L-1h−1 of 2,3-BDO through CO 66% syngas fed-batch fermentation. This was 6.5-fold higher than that of the wild type. We developed a microorganism with high CO tolerance, and this strain showed high application potential as a biocatalyst that can efficiently convert CO gas into value-added chemicals.

Improved the Methanol Electro-Oxidation and Carbon Monoxide Tolerance for Direct Methanol Fuel Cells Using Strontium Molybdate

A high methanol electro-oxidation (MOR) and carbon monoxide (CO) tolerance satisfied the electrochemical requirements of direct methanol fuel cells (DMFCs). The study investigated strontium molybdate (SrMoO4) mixed with Vulcan XC-72, carbon-loaded with 20% Pt. The electrochemical performance was confirmed by MOR and CO tolerance activities measured via cyclic voltammetry (CV). The synergistic effect between Pt and SrMoO4 is essential to affect the electrochemical characteristic. SrMoO4 can help remove CO-like intermediate products on the Pt surface, enhancing electrochemical performance for DMFCs. In addition, HxMoO3/HyMoO3 existence in Sr0.5Mo0.5O4−δ can quickly remove intermediates from Pt surfaces and accelerate the transformation of adsorbed intermediates to CO2. The results obtained showed that 20%-Pt/uncalcined Sr0.5Mo0.5O4−δ-C electrocatalyst has higher MOR and CO tolerance ability in DMFCs. Furthermore, the fabricated DMFC shows excellent long-term electrochemical stability after 1000 cycles and a maximum power density (1.42 mW/cm2) higher than commercial 20%-Pt/C (1.27 mW/cm2).

Analysis of The Injection Pressure Effect on Single Cylinder Diesel Engine Power with Diesel Fuel-Methanol Blend

The use of fossil diesel fuels still produces carbon dioxide emissions (CO 2 ), sulphur dioxide (SO 2 ), hydrocarbon emissions (HC), nitrogen oxide (NO x ), and high total particles and carbon monoxide (CO). Moreover, the need for transportation of motor vehicles will always increase every year. The emission of exhaust gases resulting from the combustion process can essentially be reduced by improving fuel quality, the homogeneity of the fuel mixture, and regulating proper combustion. There are several ways to reduce exhaust emissions from diesel engines by providing precise injection pressures. This is done to get the perfect combustion. In addition, improving fuel quality is a way to reduce emissions of exhaust gases. Another one is by adding methanol to the diesel. The addition of methanol can reduce the emission of exhaust gas produced. The process of mixing the solar and methanol takes the addition of surfactants to obtain good homogeneity. Testing was conducted using simulation software with engine modeling. The result can be seen in the reduction and the addition of standard pressure 200 bar, that the emulsion fuel in SFOC (specific fuel oil consumption) suffered a decrease and increased by 0.2% and 0.3% at pressure 160 bar and pressure 240 bar. The fuel solution on SFOC suffered a decrease and an increase of 0.3% and 0.25% was produced by pressure 160 bar and pressure 240 bar. The highest NO x is produced by 240 bar injection pressures with Dexlite fuel while the lowest NO x is produced by 160 bar injection pressure with emulsion fuel.

Differences in Fine Particle Exposure and Estimated Pulmonary Ventilation Rate with Respect to Work Tasks of Wildland Firefighters at Prescribed Burns: A Repeated Measures Study.

Wildland firefighters (WLFFs) are exposed to a mixture of chemicals found in wildland fire smoke and emissions from nonwildland-fuel smoke sources such as diesel. We investigated compositional differences in exposure to particulate matter and explored differences in ventilation rate and potential inhaled dose relative to the work tasks of WLFFs. Repeated measures on ten professional and two volunteer firefighters were collected on prescribed burn and nonburn days. Personal monitoring consisted of real-time and gravimetric fine particulate matter (PM2.5), carbon monoxide (CO), and accelerometer measurements to estimate ventilation rate and potential dose of PM2.5. The fine particulate matter was analyzed for levoglucosan (LG) and light absorbing carbon as a surrogate for black carbon (BC). Breathing zone personal exposure concentrations of PM2.5, LG, BC, and CO were higher on burn days (P &lt; 0.05). Differences in exposure concentrations were observed between burn day tasks (P &lt; 0.05) with firefighters managing fire boundaries (holders) being exposed to higher CO and LG concentrations and less BC concentrations than those conducting lighting (lighters). While no statistical difference in PM2.5 exposure measures was observed between the two tasks, holders in the study tended to be exposed to higher PM2.5 concentrations (~1.4×), while lighters tended to have more inhaled amounts of PM2.5 (~1.3×). Our findings demonstrate possible diversity in the sources of particulate matter exposure at the fireline and suggest the potential importance of using dose as a metric of inhalation exposure in occupational or other settings.

Ambient carbon monoxide correlates with mortality risk of hemodialysis patients: comparing results of control selection in the case-crossover designs.

BackgroundGrowing evidence suggests that environmental air pollution adversely affects kidney health. To date, the association between carbon monoxide (CO) and mortality in patients with end-stage renal disease (ESRD) has not been examined.MethodsAmong 134,478 dialysis patients in the Korean ESRD cohort between 2001 and 2014, 8,130 deceased hemodialysis patients were enrolled, and data were analyzed using bidirectional, unidirectional, and time-stratified case-crossover design. We examined the association between short-term CO concentration and mortality in patients with ESRD. We used a two-pollutant model, adjusted for temperature as a climate factor and for nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and particulate matter less than 10 μm in diameter as air pollution variables other than CO. ResultsCharacteristics of the study population included age (66.2 ± 12.1 years), sex (male, 59.1%; female, 40.9%), and comorbidities (diabetes, 55.6%; hypertension, 14.4%). Concentration of CO was significantly associated with all-cause mortality in the three case-crossover designs using the two-pollutant model adjusted for SO2. Patients with diabetes or age older than 75 years had a higher risk of mortality than patients without diabetes or those younger than 75 years.ConclusionFindings presented here suggest that higher CO concentration is correlated with increased all-cause mortality in hemodialysis patients, especially in older high-risk patients.

Minimizing Heat Transfer Resistance in an Integrated Methanol Steam Reformer Designed Using Space-Filling Curves

Conventional packed bed methanol steam reformers producing hydrogen for PEM fuel cells have an inherent trade-off problem between simultaneously attaining high methanol conversion and low carbon monoxide production, owing to high thermal resistance in the packed bed. A sophisticated reformer design using Hilbert’s space-filling curves is proposed and demonstrated using CFD modeling and simulation. The reactor comprises a flow-through domain divided into two interdigitating but nonmixing continua that are separated by a thin wall, providing high interfacial area for heat transfer and surface reactions. The interfacial wall is modeled as coated with catalyst for performing reforming on one side and fuel cell anode exhaust hydrogen combustion on the other side. About 84% methanol conversion and CO production less than 2% was achieved due to remarkable reduction in heat transfer resistance. External mass transfer controlled the reactor operation, while reaction kinetics exhibited nontrivial influence on reactor performance.

An overview of indoor air pollution in the Malaysian kindergarten environment

Abstract The components of indoor air determine the quality of the indoor environment, which affects the health and well-being of inhabitants. Exposure to high levels of indoor air pollution in a kindergarten environment has a detrimental influence on children’s learning performance and increases the risk of respiratory problems that could lead to absenteeism. This paper explores and summarises the literature on indoor air pollution in kindergartens in the Malaysian environment. A review was done by analyzing papers taken from four electronic databases: Scopus, Science Direct, PubMed and Google Scholar. Information on indoor pollution levels and determinants sources were extracted from 17 studies. The most investigated pollutants were carbon dioxide (CO2), particulate matter (PM2.5 and PM10), volatile organic compounds (VOCs), carbon monoxide (CO), fungi and bacteria. Inadequate ventilation systems and overcrowded classrooms all contributed to excessive CO2 levels. Indoor PM2.5 sources are generated from cooking activities while cleaning, opening windows and movement activities of children were the primary sources of coarse particles. High concentrations of VOCs are emitted from a wide variety of indoor sources. Mobile vehicles and the proximity of kindergartens to busy roads were key contributors to higher CO concentrations. The findings highlight the importance of interventions to improve indoor air pollution in kindergarten premises in various settings.

Dendrimer-encapsulated PtSn bimetallic ultrafine nanoparticles supported on graphitic mesoporous carbon as efficient electrocatalysts for methanol oxidation

Catalytic performance of Pt based nanocatalysts significantly depends on their morphologies, compositions and structures. In this work, the generation-4 phenylazomethine-tetraphenylmethane dendrimer (TPMG4)-encapsulated PtSn bimetallic ultrafine nanoparticles with tunable ratio of Pt and Sn (PtnSn60-n@TPMG4/GMC, n = 56, 48, 32) supported on graphitic mesoporous carbon (GMC) were fabricated through co-reduction method by using the phenylazomethine dendrimer as a template. The morphologies, compositions, and structures of resulting PtnSn60-n@TPMG4/GMC were detected by UV–vis absorption spectra (UV–vis), inductively coupled plasma-optical emission spectroscopy (ICP-OES), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) measurements. These physical characterizations show that dendrimer-encapsulated PtnSn60-n nanoparticles are anchored on the surface of graphitic mesoporous carbon with highly dispersion and uniformly ultrafine size of ∼1 nm, The atomic ratio of Pt and Sn in PtnSn60-n bimetallic nanoparticles can be accurately controlled. The electrochemical characterizations demonstrate that all PtnSn60-n@TPMG4/GMC samples exhibit more excellent electrocatalytic performance for methanol oxidation than single metal Ptm@TPMG4/GMC and commercial carbon supported platinum catalyst (Pt/C). Especially, the Pt56Sn4@TPMG4/GMC displays the highest catalytic activity with 1.6 times higher than Pt60/GMC and 1.9 times higher than Pt/C. Also, the Pt56Sn4@TPMG4/GMC exhibits the high carbon monoxide (CO) tolerance and superior catalytic stability towards methanol oxidation. Consequently, constructing Pt based bimetallic nanoparticles with controllable compositions and structures is an effective way to improve the catalytic performance and reduce the amount of Pt used in the catalysts, which will be widely concerned in the field of direct methanol fuel cells.

Exploring Health Impacts of Occupational Exposure to Carbon Monoxide in the Labour Community of Hattar Industrial Estate

This study was designed to assess the health impacts related to noninvasive carbon monoxide saturation (SPCO %) in the blood of respondents. For this purpose, 150 respondents from the labour community of Hattar Industrial Estate (testing site) and 100 respondents from Sultan Pur (control site) were selected. To achieve this objective, a Rad-57 Pulse CO-Oximeter was used for noninvasive carboxyhemoglobin measurement. Carbon monoxide saturation (SPCO%) in the blood of respondents from Hattar Industrial Estate, Haripur, Pakistan has been compared with the WHO’s standard concentration of SPCO% (5%). High saturation of carbon monoxide (carboxyhemoglobin SPCO) in the blood of respondents and disease association have been interpreted in graphs formed on the basis of statistical analysis in terms of frequencies, using statistical software (SPSS), based on demographic entries as well as exposure time of the employees in the processing, food and steel industries. The highest SPCO% measured was 17% in the steel industry and the lowest measured level was 4.2%. Frequencies and percentages of respiratory inflammation, dermatosis, asthma, breathing issues and eye inflammation among respondents were 29%, 35%, 16.7%, 23.5% and 9%, respectively. Prevalence of disease in three different groups of respondents (from three testing sites) was also analyzed on the basis of exposure time (hrs.) to carbon monoxide emissions. Prevalence of disease among the exposed and non-exposed groups was analyzed and showed comparatively lower disease prevalence in the group of respondents who were not exposed to high carbon monoxide emissions. The data of the current study was also subjected to statistical modelling to find the health risk of air pollutants (carbon monoxide) on population health by calculating attributable risk (AR) or attributable proportion (AP). Results indicated that attributable risk of carbon monoxide exposure for respiratory diseases, dermatosis and eye inflammation were 61.12%, 65.77% and 24.95% respectively. Findings of statistical modelling indicated that dermatosis and respiratory diseases were more prevalent in laborers of industrial units than those at control site.

Comparison of efficiency and emission characteristics in a direct-injection compression ignition engine fuelled with iso-octane and methanol under low temperature combustion conditions

Gasoline and methanol are highly recommended for low temperature combustion (LTC) engines due to their high research octane number. However, engines fuelled with these fuels suffer from high unburned hydrocarbon (UHC) and carbon monoxide (CO) emissions at low loads, which can be improved by controlling the level of mixture stratification. This paper reports on the experimental and numerical comparison of the emission characteristics and engine performance of methanol and iso-octane in a heavy-duty direct-injection compression ignition engine operating in HCCI and PPC regimes. Overall, methanol requires a higher intake temperature, compared with iso-octane, to counter the high heat of vaporization. The onset of ignition is from the relatively fuel-lean regions resulting in lower CO emissions. This is due to the methanol ignition delay times being less sensitive to the fuel/air mixture and the larger temperature gradient of the equivalence ratio. Methanol achieves lower charge stratification because of its low stoichiometric A/F ratio, which extends the SOI window with ultra-low NOx emissions. However, methanol suffers from higher UHC emissions in the HCCI regime due to fuel trapped in the crevice region. Three cases include HCCI, PPC with low and high mixture stratification were detailed investigated. Of these cases, PPC with low mixture stratification case shows the highest engine thermal efficiency and the lowest emissions. Methanol has more advantages operating in the PPC regime in the aspect of emissions.

Does air pollution modify temperature-related mortality? A systematic review and meta-analysis

IntroductionThere is an increasing interest in understanding whether air pollutants modify the quantitative relationships between temperature and health outcomes. The results of available studies were, however, inconsistent. This study aims to sum up the current evidence and provide a comprehensive understanding of this topic. MethodsWe conducted an electronic search in PubMed (MEDLINE), EMBASE, Web of Science Core Collection, and ProQuest Dissertations and Theses. The modified Navigation Guide was applied to evaluate the quality and strength of evidence. We calculated pooled temperature-related mortality at low and high pollutant levels respectively, using the random-effects model. ResultsWe identified 22 eligible studies, eleven of which were included in the meta-analysis. Significant effect modification was observed on heat effects for all-cause and non-accidental mortality by particulate matter with an aerodynamic diameter of <10 μm (PM10) and ozone (O3) (p < 0.05). The excess risks (ERs) for all-cause and non-accidental mortality were 5.4% (4.4%, 6.4%) and 6.3% (4.8%, 7.8%) at the low PM10 level, 8.8% (7.5%, 10.1%) and 11.4% (8.7%, 14.2%) at the high PM10 level, respectively. As for O3, the ERs for all-cause and non-accidental mortality were 5.1% (3.9%, 6.3%) and 3.6% (0.1%, 7.2%) at the low O3 level, 7.6% (6.3%, 9.0%) and 12.5% (4.7%, 20.9%) at the high O3 level, respectively. Surprisingly, the heat effects on cardiovascular mortality were found to be lower at high carbon monoxide (CO) levels [ERs = 5.4% (3.9%, 6.9%)] than that at low levels [ERs = 9.4% (7.0%, 11.9%)]. The heterogeneity varied, but the results of sensitivity analyses were generally robust. Significant effect modification by air pollutants was not observed for heatwave or cold effects. ConclusionsPM10 and O3 modify the heat-related all-cause and non-accidental mortality, indicating that policymakers should consider air pollutants when establishing heat-health warning systems. Future studies with comparable designs and settings are needed.

Novel strategies to extend the operating load range of a premixed charge compression ignited light-duty diesel engine

Low-temperature combustion (LTC) is an alternative combustion mode to conventional diesel combustion (CDC) that offers a simultaneous reduction in oxides of nitrogen (NOx) and particulate matter (PM) emissions while retaining higher thermal efficiency. Premixed charge compression ignition (PCCI) is a promising LTC strategy that utilizes the early direct injection of diesel and exhaust gas recirculation (EGR) to reduce NOx and PM emissions simultaneously. A limited operating load range and high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are the significant shortcomings to be addressed to realize PCCI as a commercially viable option. The present work aims to address these limitations based on experimental investigations carried out in a production light-duty diesel engine. An existing mechanical fuel injection system is replaced with a flexible common rail direct injection (CRDI) system to implement PCCI in the test engine. Based on initial parametric investigations, it was found that a combination of early direct injection, lower injection pressures, and EGR was deemed necessary to achieve PCCI mode in the test engine. However, the achievable load range was limited to 40% of the rated load, along with high HC and CO emissions. Novel approaches are attempted to address these limitations, including replacing diesel with diesel-gasoline blends with 30% gasoline by volume and utilizing a dual charge dilution strategy with water vapour induction and EGR. The start of fuel injection (SOI) sweeps from 30 to 70 deg. CA bTDC were performed to find optimal timing at each load condition to maximize the thermal efficiency within a stable combustion regime between a misfire and knocking. For loads above 40%, EGR in the range of 14% to 26.5% was used to bring the combustion within knock limits. By combining the proposed novel strategies, the engine operating load range could be extended from 40% to 80% of the rated load in PCCI. The NOx and soot emissions were significantly reduced up to 98.5% and 99.1%, respectively, compared to CDC. The engine brake thermal efficiency is increased by up to 1.6%. However, there was a significant penalty regarding HC and CO emissions.

Exhaust Emissions Measurement of a Vehicle with Retrofitted LPG System

The aim of this study was to compare and evaluate the production of exhaust emissions from a vehicle with a petrol engine with the Euro 4 emission standard and powered by petrol and LPG (liquefied petroleum gas). The paper presents new possibilities for monitoring exhaust emissions using an exhaust gas analyzer. At the same time, it points out the topicality and significance of the issue in the monitored area. It examines the impact of a change in fuel on emissions. This change is monitored in various areas of vehicle operation. Measurements were performed during real operation, which means that the results are fully usable and applicable in practice. The driving simulation as well as the test conditions correspond to the RDE (Real Driving Emissions) test standard. A commercially available car was first selected to perform the tests, which was first measured in the original configuration (petrol drive). Based on real-time RDE driving tests, it is possible to determine the number of exhaust emissions. Subsequently, the same measurements were performed with the same vehicle, but the vehicle’s propulsion was changed to LPG. The vehicle was equipped with an additional system that allowed the vehicle to be powered by LPG. The results from the individual driving tests allowed the determination of the exhaust emissions. Emissions of CO (carbon monoxide), CO2 (carbon dioxide), HC (hydrocarbons), and NOx (nitrogen oxides) were monitored as a matter of priority. Through the driving tests, it was found that the gasoline combustion produced higher CO (1.926 g/km) and CO2 (217.693 g/km) emissions compared to the combustion of liquefied gas, where the concentration of the CO emissions was 1.892 g/km and that of the CO2 emissions was 213.966 g/km. In contrast, the HC (0.00397 g/km) and NOx (0.03107 g/km) emissions were lower when petrol was burned. During LPG combustion, the HC emissions reached 0.00430 g/km, and the NOx emissions reached 0.05134 g/km. At the end of the research, the authors compared the emissions determined by real driving (in g/km) with the emission values produced by the emission standard EURO 4 and the certificate of conformity (COC). Practical measurements showed that the vehicle produced excessive amounts of CO when burning gasoline. This production is 0.926 g/km higher and 0.892 g/km higher when burning LPG compared to the limit set by the Euro 4 Emission Standard. The difference is even greater than the limit value stated in the COC document. For other substances, the monitored values are in the norm and are even far below the permitted value