Impacts of ethanol blended fuels and cold temperature on VOC emissions from gasoline vehicles in China.

The Chinese central government has initiated pilot projects to promote the adoption of gasoline containing 10%v ethanol (E10). Vehicle emissions using ethanol blended fuels require investigation to estimate the environmental impacts of the initiative. Five fuel formulations were created using two blending methods (splash blending and match blending) to evaluate the impacts of formulations on speciated volatile organic compounds (VOCs) from exhaust emissions. Seven in-use vehicles covering China 4 to China 6 emission standards were recruited. Vehicle tests were conducted using the Worldwide Harmonized Test Cycle (WLTC) in a temperature-controlled chamber at 23 °C and -7 °C. Splash blended E10 fuels led to significant reductions in VOC emissions by 12%-75%. E10 fuels had a better performance of reducing VOC emissions in older model vehicles than in newer model vehicles. These results suggested that E10 fuel could be an option to mitigate the VOC emissions. Although replacing methyl tert-butyl ether (MTBE) with ethanol in regular gasoline had no significant effects on VOC emissions, the replacement led to lower aromatic emissions by 40%-60%. Alkanes and aromatics dominated approximately 90% of VOC emissions for all vehicle-fuel combinations. Cold temperature increased VOC emissions significantly, by 3-26 folds for all vehicle/fuel combinations at -7 °C. Aromatic emissions were increased by cold temperature, from 2 to 26 mg/km at 23 °C to 33-238 mg/km at -7 °C. OVOC emissions were not significantly affected by E10 fuel or cold temperature. The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of splash blended E10 fuels decreased by up to 76% and 81%, respectively, compared with those of E0 fuels. The results are useful to update VOC emission profiles of Chinese vehicles using ethanol blended gasoline and under low-temperature conditions.

Large Decreases in Tailpipe Criteria Pollutant Emissions from the U.S. Light-Duty Vehicle Fleet Expected in 2020-2040.

The U.S. EPA MOVES3 model was used to assess the impact of the large-scale introduction of electric vehicles on emissions of criteria pollutants (CO, hydrocarbons [HC], NOx, and particulate matter [PM]) and CO2 from the U.S. light-duty vehicle fleet. Large reductions in emissions of these criteria pollutants occurred in 2000-2020. These trends are expected to continue through 2040 driven by turnover of the conventional fleet with old vehicles being replaced by battery electric vehicles (BEVs) and by new internal combustion engine vehicles (ICEVs) with modern emission control systems. Without the introduction of BEVs, the absolute emissions of CO, NOx, HC, and PM2.5 from the U.S. light-duty vehicle fleet are expected to decrease by approximately 61, 88, 55, and 20% from 2020 to 2040. Introduction of BEVs with market share increasing linearly to 100% in 2040 provides additional benefits, which, combined with ICEV fleet turnover, would lead to decreases of absolute emissions of CO, NOx, HC, and PM2.5 of approximately 77, 94, 71, and 37% from 2020 to 2040. Reductions in CO2 emissions follow a similar pattern. Large decreases in criteria pollutant and CO2 emissions from light duty vehicles lie ahead.

Prediction of heel build-up on activated carbon using machine learning.

Determining the long-term performance of adsorbents is crucial for the design of air treatment systems. Heel buildup i.e., the accumulation of non-desorbed/ non-desorbable adsorbates and their reaction byproducts, on the surface/pores of the adsorbent is a primary cause of adsorption performance deterioration. However, due to the complexity of heel buildup mechanisms, theoretical models have yet to be developed to map the extent of heel buildup to the adsorption/desorption parameters. In this work, two machine learning (ML) algorithms (XGBoost and neural network (NN)) were applied to predict volatile organic compounds (VOCs) cyclic heel buildup on activated carbons (ACs) by considering the adsorbent characteristics, adsorbate properties and regeneration conditions. The NN algorithm showed better performance in prediction of cyclic heel buildup (R2 = 0.94) than XGBoost (R2 = 0.81). To analyze interaction between heel buildup and adsorbent characteristics, adsorbate properties, and regeneration conditions, partial dependency plots were generated. The proposed ML-based heel prediction methods can be ultimately used to: (i) optimize adsorption/desorption operating conditions to minimize heel buildup on activated carbon in cyclic adsorption/desorption processes and (ii) quickly screen various adsorbents for efficient adsorption/desorption of a particular family of VOCs by excluding adsorbents prone to high heel formation.

Porous carbon black-polymer composites for volatile organic compound adsorption and efficient microwave-assisted desorption.

Adsorbents with high surface area, thermal stability and microwave absorption ability are highly desired for cyclic adsorption and microwave regeneration processes. However, most polymeric adsorbents are transparent to microwaves. Herein, porous hyper-crosslinked polymers (HCP) of (4,4'-bis((chloromethyl)-1,1'-biphenyl-benzyl chloride)) with different carbon black (CB) contents were synthesized via the Friedel-Crafts reaction. CB was selected as the filler due to its low cost and high dielectric loss and was embedded inside the polymer structure during polymerization. CB-containing composites showed enhanced thermal stability at elevated temperatures, and more than a 90-times increase in the dielectric loss factor, which is favorable for microwave regeneration. Nitrogen physisorption analysis by the Bruner-Emmett-Teller isotherms demonstrated that CB presence in the polymer structure nonlinearly decreases the surface area and total pore volume (by 38% and 26%, respectively at the highest CB load). Based on the characterization testing, 4 wt% of CB was found to be an optimum filler content, having the highest MW absorption and minimal effect on the adsorbent porosity. HCP with 4 wt% CB allowed a substantial increase in the desorption temperature and yielded more than a 450% enhancement in the desorption efficiency compared to HCP without CB.

Mathematical correlations in two-phase modeling of fluidized bed adsorbers.

Choosing proper formulas for estimating different variables is imperative when modeling a fluidized bed using two-phase theory. In this study, a two-phase model was used to model the adsorption of volatile organic compounds (VOC) in a multistage fluidized bed adsorber. Two different approaches were used to describe gas flow and mixing in the emulsion phase, perfectly mixed (EGPM: Emulsion Gas - Perfectly Mixed) and plug flow (EGPF: Emulsion Gas - Plug flow). The impact of different formulas for estimating bubble size, bed porosity at minimum fluidization velocity, adsorption and interphase mass transfer coefficients, as well as tortuosity on the performance of the model was determined by comparing the model outcomes with experimental data. Finally, using a large dataset obtained from fluidized bed adsorption systems with different adsorbents, adsorbates, bed sizes, and operating conditions, a broadly-applicable set of formulas was suggested which could be used to describe the behavior of different countercurrent fluidized bed adsorbers. From the results, the two-phase model could successfully predict the experimental data, with EGPF showing better performance than EGPM. Proper use of formulas, especially those describing bed voidage and interphase mass transfer coefficient, could markedly improve the performance of the two-phase model. The two-phase model using the set of formulas proposed here was able to accurately replicate a large dataset of fluidized bed adsorption experiments over a wide range of operating conditions.

Carbon implications of marginal oils from market-derived demand shocks.

Expanded use of novel oil extraction technologies has increased the variability of petroleum resources and diversified the carbon footprint of the global oil supply1. Past life-cycle assessment (LCA) studies overlooked upstream emission heterogeneity by assuming that a decline in oil demand will displace average crude oil2. We explore the life-cycle greenhouse gas emissions impacts of marginal crude sources, identifying the upstream carbon intensity (CI) of the producers most sensitive to an oil demand decline (for example, due to a shift to alternative vehicles). We link econometric models of production profitability of 1,933 oilfields (~90% of the 2015 world supply) with their production CI. Then, we examine their response to a decline in demand under three oil market structures. According to our estimates, small demand shocks have different upstream CI implications than large shocks. Irrespective of the market structure, small shocks (-2.5% demand) displace mostly heavy crudes with ~25-54% higher CI than that of the global average. However, this imbalance diminishes as the shocks become bigger and if producers with market power coordinate their response to a demand decline. The carbon emissions benefits of reduction in oil demand are systematically dependent on the magnitude of demand drop and the global oil market structure.

Modeling VOC adsorption in lab- and industrial-scale fluidized bed adsorbers: Effect of operating parameters and heel build-up.

Scale-up and optimization of fluidized beds are challenging due to the difficulty in accounting for the interrelated effect of various phenomena, which are typically described by empirical and/or semi-empirical equations. In this study, a two-phase model was introduced to simulate the adsorption of VOCs on beaded activated carbon (BAC) in a lab-scale fluidized bed adsorber. The model assumes the presence of a bubble phase free from adsorbent particles, and an emulsion phase composed of the adsorbent particles and interstitial gas. The versatility of the proposed model was then evaluated using data from an industrial scale adsorber with different operating conditions, adsorbent properties, and bed geometry. The response of the model to the operating conditions (adsorbent feed rate, air flow rate and initial concentration) showed better agreement with the experimental lab-scale data when the emulsion gas in two-phase model was considered in plug flow than in perfectly-mixed flow (R2 = 0.96 compared to 0.91). To simulate the performance of BACs with different service lifetimes (degree of exhaustion as a result of heel developed inside their pores), the main characteristics of the BACs (pore diameter, porosity, and adsorption capacity) were first correlated to their apparent densities. The model could accurately predict the experimental lab-scale VOC concentrations in each stage (R2 = 0.92) as well as overall removal efficiencies (R2 = 0.99) for BACs ranging from virgin to fully-spent. Finally, the model was used to predict the performance of an industrial-scale fluidized bed adsorber for VOC removal at different operating conditions and apparent densities. Predicted and measured VOC removal efficiencies were in good agreement (R2 = 0.94). Although the model was verified for adsorption of VOCs on BAC, the modeling approach presented in this study could be used for describing adsorption in different adsorbate-adsorbent systems in multistage counter-current fluidized bed adsorbers.

Investigation of polymers and alcohols produced in oxidized soybean oil at frying temperatures.

Although significant amounts of polymers associated with adverse health effects in oils are produced during frying, the chemical bonds forming these polymers are not well understood. This study revealed that ester bonds are responsible for the polymerization of soybean oil during frying and heating at 175 °C. The ester value of soybean oil increased during frying up to day 3 of the experiment and slightly decreased on day 4 of the experiment indicating that esterification and hydrolysis concomitantly occurred. The 13C NMR spectra showed further evidence of the formation of ester bonds. This study also examined unidentified chemical bonds in the polymer products, other than ester bonds, with NMR spectroscopy. No NMR signals indicating ether bonds were observed. The NMR study after the reaction of oxidized soybean oil with acetyl chloride clarified assignments of proton signals, confirming some previous assignments, and assigning a new proton signal as an alcohol.

Modeling the Effect of Relative Humidity on Adsorption Dynamics of Volatile Organic Compound onto Activated Carbon.

A two-dimensional heterogeneous mathematical model was developed and validated to study the effect of relative humidity on volatile organic compound (VOC) adsorption onto activated carbon. The dynamic adsorption model consists of the macroscopic mass, momentum, and energy conservation equations and includes a multicomponent adsorption isotherm to predict the competitive adsorption equilibria between VOC and water vapor, which is described by an extended Manes method. Experimental verifications show that the model predicted the breakthrough profiles during competitive adsorption of the studied VOCs (2-propanol, acetone, n-butanol, toluene, 1,2,4-trimethylbenzene) at relative humidity range 0-95% with an overall mean relative absolute error (MRAE) of 11.8% for dry (0% RH) conditions and 17.2% for humid (55 and 95% RH) conditions, and normalized root-mean-square error (NRMSE) of 5.5 and 8.4% for dry and humid conditions, respectively. Sensitivity analysis was also conducted to test the robustness of the model in accounting for the impact of relative humidity on VOC adsorption by varying the adsorption temperature. Good agreement was observed between the experimental and simulated results with an overall MRAE of 12.4 and 7.1% for the breakthrough profiles and adsorption capacity, respectively. The model can be used to quantify the impact of carrier gas relative humidity during adsorption of contaminants from gas streams, which is useful when optimizing adsorber design and operating conditions.

Properly folded and functional PorB from Neisseria gonorrhoeae inhibits dendritic cell stimulation of CD4+ T cell proliferation.

Neisseria gonorrhoeae is an exclusive human pathogen that evades the host immune system through multiple mechanisms. We have shown that N. gonorrhoeae suppresses the capacity of antigen-presenting cells to induce CD4+ T cell proliferation. In this study, we sought to determine the gonococcal factors involved in this adaptive immune suppression. We show that suppression of the capacity of antigen-pulsed dendritic cells to induce T cell proliferation is recapitulated by administration of a high-molecular-weight fraction of conditioned medium from N. gonorrhoeae cultures, which includes outer membrane vesicles that are shed during growth of the bacteria. N. gonorrhoeae PorB is the most abundant protein in N. gonorrhoeae-derived vesicles, and treatment of dendritic cells with purified recombinant PorB inhibited the capacity of the cells to stimulate T cell proliferation. This immunosuppressive feature of purified PorB depended on proper folding of the protein. PorB from N. gonorrhoeae, as well as other Neisseria species and other Gram-negative bacterial species, are known to activate host Toll-like receptor 2 (TLR2) signaling. Published studies have demonstrated that purified Neisseria PorB forms proteinacious nanoparticles, termed proteosomes, when detergent micelles are removed. Unlike folded, detergent-solubilized PorB, PorB proteosomes stimulate immune responses. We now demonstrate that the formation of PorB proteosomes from structurally intact PorB eliminates the immunosuppressive property of the protein while enhancing TLR2 stimulation. These findings suggest that gonococcal PorB present in shed outer membrane vesicles plays a role in suppression of adaptive immune responses to this immune-evasive pathogen.

Neisseria gonorrhoeae Lytic Transglycosylases LtgA and LtgD Reduce Host Innate Immune Signaling through TLR2 and NOD2.

Neisseria gonorrhoeae releases anhydro peptidoglycan monomers during growth through the action of two lytic transglycosylases encoded in the N. gonorrhoeae genome, LtgA and LtgD. Because peptidoglycan and peptidoglycan components activate innate immune signaling, we hypothesized that the activity of LtgA and LtgD would influence the host responses to gonococcal infection. N. gonorrhoeae lacking LtgA and LtgD caused increased host production of inflammatory cytokines IL-1ß and TNF-α. Culture supernatants from ΔltgA/ΔltgD N. gonorrhoeae contain more shed outer membrane-associated proteins and multimeric peptidoglycan fragments rather than monomers. These culture supernatants were more potent activators of host TLR2 and NOD2 signaling when compared to supernatants from the isogenic parental N. gonorrhoeae strain. Purified peptidoglycan monomers containing anhydro muramic acid produced by LtgA were poor stimulators of NOD2, whereas peptidoglycan monomers containing reducing muramic acid produced by host lysozyme were potent stimulators of NOD2. These data indicate that LtgA and LtgD reduce recognition of N. gonorrhoeae by TLR2 and NOD2.

The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors.

The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials.

The role of beaded activated carbon's pore size distribution on heel formation during cyclic adsorption/desorption of organic vapors.

The effect of activated carbon's pore size distribution (PSD) on heel formation during adsorption of organic vapors was investigated. Five commercially available beaded activated carbons (BAC) with varying PSDs (30-88% microporous) were investigated. Virgin samples had similar elemental compositions but different PSDs, which allowed for isolating the contribution of carbon's microporosity to heel formation. Heel formation was linearly correlated (R(2)=0.91) with BAC micropore volume; heel for the BAC with the lowest micropore volume was 20% lower than the BAC with the highest micropore volume. Meanwhile, first cycle adsorption capacities and breakthrough times correlated linearly (R(2)=0.87 and 0.93, respectively) with BAC total pore volume. Micropore volume reduction for all BACs confirmed that heel accumulation takes place in the highest energy pores. Overall, these results show that a greater portion of adsorbed species are converted into heel on highly microporous adsorbents due to higher share of high energy adsorption sites in their structure. This differs from mesoporous adsorbents (low microporosity) in which large pores contribute to adsorption but not to heel formation, resulting in longer adsorbent lifetime. Thus, activated carbon with high adsorption capacity and high mesopore fraction is particularly desirable for organic vapor application involving extended adsorption/regeneration cycling.

Biofuels, vehicle emissions, and urban air quality.

Increased biofuel content in automotive fuels impacts vehicle tailpipe emissions via two mechanisms: fuel chemistry and engine calibration. Fuel chemistry effects are generally well recognized, while engine calibration effects are not. It is important that investigations of the impact of biofuels on vehicle emissions consider the impact of engine calibration effects and are conducted using vehicles designed to operate using such fuels. We report the results of emission measurements from a Ford F-350 fueled with either fossil diesel or a biodiesel surrogate (butyl nonanoate) and demonstrate the critical influence of engine calibration on NOx emissions. Using the production calibration the emissions of NOx were higher with the biodiesel fuel. Using an adjusted calibration (maintaining equivalent exhaust oxygen concentration to that of the fossil diesel at the same conditions by adjusting injected fuel quantities) the emissions of NOx were unchanged, or lower, with biodiesel fuel. For ethanol, a review of the literature data addressing the impact of ethanol blend levels (E0-E85) on emissions from gasoline light-duty vehicles in the U.S. is presented. The available data suggest that emissions of NOx, non-methane hydrocarbons, particulate matter (PM), and mobile source air toxics (compounds known, or suspected, to cause serious health impacts) from modern gasoline and diesel vehicles are not adversely affected by increased biofuel content over the range for which the vehicles are designed to operate. Future increases in biofuel content when accomplished in concert with changes in engine design and calibration for new vehicles should not result in problematic increases in emissions impacting urban air quality and may in fact facilitate future required emissions reductions. A systems perspective (fuel and vehicle) is needed to fully understand, and optimize, the benefits of biofuels when blended into gasoline and diesel.

When Do DCD Donors Die?: Outcomes and Implications of DCD at a High-volume, Single-center OPO in the United States.

OBJECTIVE: The objective of this study was to determine the fate of patients who attempted to donate organs after circulatory death (DCD) using a standardized DCD protocol. BACKGROUND: Successful donation is not always possible after attempted DCD. METHODS: Data were collected for all DCD donors between 1/2011 and 9/2014. DCDs were carried out using a uniform protocol at a single-center organ procurement organization. RESULTS: During the timeframe considered, DCD donation was attempted in 169 patients. In 46 patients (27.2%), no organs were recovered because the patients did not die within 2 hours. Successful donation was more likely if withdrawal of support occurred in the operating room versus the intensive care unit (P = 0.006). Time from extubation to death was available for 161/169 donors (95.3%). Of 161 donors, 111 (66.9%) died in under 1 hour. The mean time from withdrawal of support to patient death for unsuccessful donations was 33 hours, 37 minutes (range, 24 minutes-242 hours) versus 29 minutes (range, 5 minutes-2 hours, 4 minutes) for successful donations. Twenty-seven patients who unsuccessfully donated (67.5%) died within 24 hours. Were unsuccessful donations converted to successful donations, as many as 837 abdominal transplants could have been carried out in the United States, during the study period. CONCLUSIONS: DCD is an important form of organ donation. A large number of abdominal transplants are not possible due to unsuccessful DCD organ donation. It may be useful to explore DCD donor family satisfaction to identify other options for improving DCD donation.

The Effect of Compression Ratio, Fuel Octane Rating, and Ethanol Content on Spark-Ignition Engine Efficiency.

Light-duty vehicles (LDVs) in the United States and elsewhere are required to meet increasingly challenging regulations on fuel economy and greenhouse gas (GHG) emissions as well as criteria pollutant emissions. New vehicle trends to improve efficiency include higher compression ratio, downsizing, turbocharging, downspeeding, and hybridization, each involving greater operation of spark-ignited (SI) engines under higher-load, knock-limited conditions. Higher octane ratings for regular-grade gasoline (with greater knock resistance) are an enabler for these technologies. This literature review discusses both fuel and engine factors affecting knock resistance and their contribution to higher engine efficiency and lower tailpipe CO2 emissions. Increasing compression ratios for future SI engines would be the primary response to a significant increase in fuel octane ratings. Existing LDVs would see more advanced spark timing and more efficient combustion phasing. Higher ethanol content is one available option for increasing the octane ratings of gasoline and would provide additional engine efficiency benefits for part and full load operation. An empirical calculation method is provided that allows estimation of expected vehicle efficiency, volumetric fuel economy, and CO2 emission benefits for future LDVs through higher compression ratios for different assumptions on fuel properties and engine types. Accurate "tank-to-wheel" estimates of this type are necessary for "well-to-wheel" analyses of increased gasoline octane ratings in the context of light duty vehicle transportation.

Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon.

Incomplete regeneration of activated carbon loaded with organic compounds results in heel build-up that reduces the useful life of the adsorbent. In this study, microwave heating was tested as a regeneration method for beaded activated carbon (BAC) loaded with n-dodecane, a high molecular weight volatile organic compound. Energy consumption and desorption efficiency for microwave-heating regeneration were compared with conductive-heating regeneration. The minimum energy needed to completely regenerate the adsorbent (100% desorption efficiency) using microwave regeneration was 6% of that needed with conductive heating regeneration, owing to more rapid heating rates and lower heat loss. Analyses of adsorbent pore size distribution and surface chemistry confirmed that neither heating method altered the physical/chemical properties of the BAC. Additionally, gas chromatography (with flame ionization detector) confirmed that neither regeneration method detectably altered the adsorbate composition during desorption. By demonstrating improvements in energy consumption and desorption efficiency and showing stable adsorbate and adsorbent properties, this paper suggests that microwave heating is an attractive method for activated carbon regeneration particularly when high-affinity VOC adsorbates are present.

Lack of Sexual Minorities' Rights as a Barrier to HIV Prevention Among Men Who Have Sex with Men and Transgender Women in Asia: A Systematic Review.

This study set out to assess the relationship between variation in human rights for sexual minorities in Asian countries and indicators of HIV prevention among men who have sex with men (MSM) and transgender women. To quantitatively measure the relationship between variation in HIV prevention and variation in human rights for sexual minorities, this study developed the Sexual Orientation and Gender Identity (SOGI) Human Rights Index (an original index with scores ranging from 0.0 to 1.0). Subsequently, this study collected 237 epidemiological and behavioral studies from 22 Asian countries and performed a series of meta-analyses in order to calculate national averages for five indicators of HIV prevention: HIV prevalence, inconsistent condom use, recent HIV testing, adequate HIV knowledge, and exposure to HIV prevention services. A change of human rights for sexual minorities from a score of 0.0 to 1.0 as measured by the SOGI Human Rights Index was correlated with a decrease in unprotected anal intercourse by 25.5% (p=0.075), and increases in recent HIV testing by 42.9% (p=0.011), HIV knowledge by 29.5% (p=0.032), and exposure to HIV prevention services by 37.9% (p=0.119). The relationship between HIV prevalence and variation in human rights for sexual minorities was not statistically significant. Our study found correlations between human rights and indicators of HIV prevention, further supporting the need for increased rights among marginalized populations. The paucity of studies from many Asian countries as well as the disparity in how indicators of HIV prevention are measured reveals a need for increased coverage and standardization of MSM serological and behavioral data in order to better inform evidence-based policymaking.