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  • 1.
    Ahmed, Trifa Mohammad
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Emissions of particulate associated oxygenated and native polycyclic aromatic hydrocarbons from vehicles powered by ethanol/gasoline fuel blends2018In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 214, p. 381-385Article in journal (Refereed)
    Abstract [en]

    Emission factors for oxygenated polycyclic aromatic hydrocarbons (OPAHs) and PAHs have been determined from two different fuel flexible light duty vehicles operated at -7 degrees C in the New European Driving Cycle (NEDC) and at +22 degrees C in the Artemis Driving Cycle (ADC). Three different gasoline/ethanol blends, commercially available in Sweden, were tested i.e., gasoline E5, with 5% v/v ethanol and ethanol fuel E85 with 85% v/v ethanol and winter time quality E70 with 70% v/v ethanol, respectively. The results showed greatly increased emissions of both OPAHs and PAHs at cold engine start conditions (-7 degrees C in the NEDC) compared to warm engine start (+ 22 degrees C in the ADC). For the OPAHs, higher average total emission factors were obtained when running on E85 compared to E5 at both cold 2.72 mu g/km vs 1.11 mu g/km and warm 0.19 mu g/km vs 0.11 mu g/km starting conditions with the highest emissions when using E70 at -7 degrees C 4.12 mu g/km. The same trend was found for the PAHs at cold engine start with higher average total emission factors when using ethanol fuel 71.5 mu g/km and 60.0 mu g/km for E70 and E85, respectively compared to gasoline E5 (20.2 mu g/km). Slightly higher average total PAH emissions were obtained when operating at + 22 degrees C with E5 compared to with E85 1.23 mu g/km vs 0.72 mu g/km.

  • 2. Azuara, Manuel
    et al.
    Baguer, Barbara
    Villacampa, Jose I.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Manya, Joan J.
    Influence of pressure and temperature on key physicochemical properties of corn stover-derived biochar2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 186, p. 525-533Article in journal (Refereed)
    Abstract [en]

    This study focuses on analyzing the effect of both the peak temperature and pressure on the properties of biochar produced through slow pyrolysis of corn stover, which is a common agricultural waste that currently has little or no value. The pyrolysis experiments were carried out in a fixed-bed reactor at different peak temperatures (400, 525 and 650 degrees C) and absolute pressures (0.1, 0.85 and 1.6 MPa). The inert mass flow rate (at NTP conditions) was adjusted in each test to keep the gas residence time constant within the reactor. The as-received corn stover was pyrolyzed into a biochar without any physical pre-treatment as a way to reduce the operating costs. The properties of biochars showed that high peak temperature led to high fixed-carbon contents, high aromaticity and low molar H:C and O:C ratios; whereas a high pressure only resulted in a further decrease in the O:C ratio and a further increase in the fixed-carbon content. Increasing the operating pressure also resulted in a higher production of pyrolysis gas at the expense of water formation.

  • 3. Cladek, Bernadette R.
    et al.
    Ramirez-Cuesta, A. J.
    Everett, S. Michelle
    McDonnell, Marshall T.
    Daemen, Luke
    Cheng, Yongqiang
    B. Brant Carvalho, Paulo H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tulk, Christopher
    Tucker, Matthew G.
    Keffer, David J.
    Rawn, Claudia J.
    In situ inelastic neutron scattering of mixed CH4–CO2 hydrates2022In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 327, article id 125197Article in journal (Refereed)
    Abstract [en]

    An abundant source of CH4 can be found in natural hydrate deposits. Recent demonstration of CH4 recovery from hydrates via CO2 exchange has revealed the potential as a fuel source that also provides a medium for carbon sequestration. It is vital to understand the structural and dynamic impacts of guest variation in CH4, CO2, and mixed hydrates and link the results to the stability of various deposits in nature, harvesting methane, and sequestering CO2. Molecular vibrations are examined in CH4, CO2, and mixed CH4-CO2 hydrates at 5 and 190 K and Xe hydrates for comparison. Inelastic neutron scattering (INS) is an ideal spectroscopy technique to observe the dynamic modes in the hydrate structure and enclathrated CH4, as it is extremely sensitive to 1H. The presence of CO2 in hydrates tightens the lattice. It introduces more active librational modes to the host lattice, while hindering the motion of CH4 in mixed CH4-CO2 hydrate at 5 K. At 190 K, a large broadening of the CH4 librational modes indicates disorder in the structure leading to dissociation.

  • 4. Nyström, Robin
    et al.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmed, Trifa Mohammad
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Koegler, Johannes H.
    Blomberg, Anders
    Sandström, Thomas
    Boman, Christoffer
    Physical and chemical properties of RME biodiesel exhaust particles without engine modifications2016In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 186, p. 102p. 261-269Article in journal (Refereed)
    Abstract [en]

    A major contributor to ambient particulate air pollution is exhaust from diesel engines and other vehicles,which can be linked to different adverse health effects. During the last decades, a global drive towardsfinding sustainable and clean bio-based alternative fuels for the transport sector has taken place and biodieselis one of the most established alternatives today. To better assess the overall effects on a publichealth level when introducing biodiesel and other renewable fuels, a better understanding of the detailedexhaust particle properties, is needed. In this work, the physical and chemical properties of biodieselexhaust particles were studied in comparison to standard diesel exhaust emissions, in an existing enginewithout modifications, focusing on particulate carbonaceous matter and PAH/Oxy-PAH as well as fineparticle size distribution. An older off-road engine, produced between 1996 and 2004, was used withthree different fuels/fuel blends; (1) 100 wt% low-sulfur standard petro diesel (SD), (2) 100 wt% rapeseedmethyl ester biodiesel (B100) and (3) a blended fuel – B30 consisting of 30 wt% RME and 70 wt% SD. Thestudy focused mainly on emissions from transient engine operation, but includes also idling conditions.The gaseous emissions measured for the biodiesel fuel were in general in accordance with previousreported data in the literature, and compared to the standard petro diesel the emissions of CO was lowerwhile NOx emissions increased. The particulate mass concentration during transient operation wasalmost halved compared to when petro diesel was used and this was associated with a decrease in averageparticle size. The shift in particle mass and size was associated with a higher fraction of organic matterin general, considerable less PAH’s but a relative higher fraction of Oxy-PAH’s, when shifting frompetro diesel to biodiesel.

  • 5.
    Olenius, Tinja
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science. Swedish Meteorological and Hydrological Institute, Sweden.
    Heitto, Arto
    Roldin, Pontus
    Yli-Juuti, Taina
    Duwig, Christophe
    Modeling of exhaust gas cleaning by acid pollutant conversion to aerosol particles2021In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 290, article id 120044Article in journal (Refereed)
    Abstract [en]

    Sulfur and nitrogen oxides (SOx and NOx) are harmful pollutants emitted into the atmosphere by industry and transport sectors. In addition to being hazardous gases, SOx and NOx form sulfuric and nitric acids which contribute to the formation of airborne particulate matter through nucleation and condensation, hence magnifying the environmental impact of these species. In this work, we build a modeling framework for utilizing this phenomenon for low-temperature exhaust gas cleaning. It has been reported that ammonia gas can be used to facilitate particle formation from the aforementioned acids, and thus remove these gaseous pollutants by converting them into ammonium sulfate and nitrate particles. Here we provide comprehensive modeling tools for applying this idea to exhaust gas cleaning by combining detailed models for nucleation, gas-particle mass exchange and particle population dynamics. We demonstrate how these models can be used to find advantageous operating conditions for a cleaning unit. In particular, the full model is computationally cheap and enables optimization of the particle formation efficiency and particle growth, hence ensuring sufficient conversion of gaseous pollutants into collectable particulate matter. This constitutes a ground for future engineering tools for designing next-generation sustainable exhaust gas cleaners.

  • 6.
    Sadiktsis, Ioannis
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Koegler, Johannes H.
    Benham, Timothy
    Bergvall, Christoffer
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Particulate associated polycyclic aromatic hydrocarbon exhaust emissions from a portable power generator fueled with three different fuels – A comparison between petroleum diesel and two biodiesels2014In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 115, p. 573-580Article in journal (Refereed)
    Abstract [en]

    The fuel impact on the emission of more than 40 particulate associated polycyclic aromatic hydrocarbons (PAHs) in the molecular weight range 178–302 Da were investigated. The fuels; neat diesel (EN 590), rape seed methyl ester (B100) and a 30% w/w blend thereof (B30) were tested on a portable power generator without any exhaust aftertreatment. Gaseous emissions of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) were measured along with particulate emissions and its size distribution for the different fuels. Collected diesel particles were extracted using pressurized fluid extraction and analyzed using an online hyphenated liquid chromatography–gas chromatography–mass spectrometry system.

    The neat B100 and the B30 fuel produced less CO and total PAHs while the emissions of NOx and particulate matter increased compared with petroleum diesel fuel per kW h. The reduction of PAH emissions of the alternative diesel fuels were 36% and 70% for B30 and B100 respectively. While the PAH profiles for the neat diesel fuel and B30 were similar, the profile of B100 differed in the sense that the emission contained a higher percentage of PAHs with higher molecular weights. The emission of these PAHs was however larger using the neat diesel fuel with the exception for some of these higher molecular weight PAHs of which there was an increased emission using B100. Thermogravimetric analysis revealed that the collected particles from B100 contained a substantial amount of volatile components. A mass spectrometric full scan analysis suggests that these volatile components are in fact unburned or partially-burned fuel constituents.

    It is concluded that the particles originating from biodiesel combustion might be very different from those originating from petroleum diesel combustion which places new demands on the development of measurement methodologies originally developed for particulate emissions from petroleum-based fuels.

  • 7. Ullah, Latif
    et al.
    Zhao, Guoying
    Ma, Jian-Xin
    Usman, Muhammad
    Khan, Rashid
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Chinese Academy of Sciences, PR China.
    Pd-promoted heteropolyacid on mesoporous zirconia as a stable and bifunctional catalyst for oxidation of thiophenes2022In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 310, article id 122462Article in journal (Refereed)
    Abstract [en]

    Sulfur-containing compounds are undesirable in fossil fuels, thus stringent regulations are in place to curb their atmospheric emissions. In this context, we hypothesized and showed that acid catalysis promoted by metal particles could be used to oxidize dibenzothiophene (DBT) and benzothiophene (BT) into sulfones that, in principle, can be subsequently removed. In specific, we studied the oxidative step of catalytic oxidative desulfurization (CODS) processes using a new bifunctional catalyst based on Pd-promoted molybdovanadophosphoric acid (Pd-PMV) supported on mesoporous zirconia (Pd-PMV/mZrO2). The PMV was supported on zirconia using a one-pot sol–gel method, and the Pd nanoparticles were deposited in a subsequent step. The activity of catalyst was excellent, with high conversions >99% and a turnover frequency (TOF) value of 384 h−1 for DBT, using catalyst Pd-15PMV/mZrO2, which had 15-wt% loading of PMV. tert-butyl hydrogen peroxide (tBHP) was used as an oxidant under relatively mild reaction conditions. The catalyst had both Brønsted and Lewis acid sites, and the Pd nanoparticles enhanced its synergistic catalytic performance. Up to a threshold level loading of PMV, the thermal stability of the catalysts was higher than the underlying mZrO2 support. A high catalytic activity was maintained with only a minor loss over 10 cycles, making the catalyst promising for oxidative deep-desulfurization of liquid hydrocarbon fuels.

1 - 7 of 7
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