Reducing Emissions of Persistent Organic Pollutants from a Diesel

Apr 16, 2014 - Department of Civil Engineering and Geomatics, Cheng Shiu University, 840 Chengching Road, Kaohsiung 83347, Taiwan. ⊥. Department of ...
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Reducing Emissions of Persistent Organic Pollutants from a Diesel Engine by Fueling with Water-Containing Butanol Diesel Blends Yu-Cheng Chang,† Wen-Jhy Lee,*,† Hsi-Hsien Yang,‡ Lin-Chi Wang,*,§ Jau-Huai Lu,⊥ Ying I. Tsai,∥ Man-Ting Cheng,# Li-Hao Young,⊗ and Chia-Jui Chiang∇ †

Department of Environmental Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan Department of Environmental Engineering and Management, Chaoyang University of Technology, 168 Jifeng E. Road, Taichung 41349, Taiwan § Department of Civil Engineering and Geomatics, Cheng Shiu University, 840 Chengching Road, Kaohsiung 83347, Taiwan ⊥ Department of Mechanical Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 40254, Taiwan ∥ Department of Environmental Resources Management, Chia Nan University of Pharmacy and Science, 60 Erh-Jen Road Sec. 1, Tainan 71710, Taiwan # Department of Environmental Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 40254, Taiwan ⊗ Department of Occupational Safety and Health, China Medical University, 91 Hsueh-Shih Road, Taichung 40402, Taiwan ∇ Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43 Keelung Road Sec. 4, Taipei 10607, Taiwan ‡

S Supporting Information *

ABSTRACT: The manufacture of water-containing butanol diesel blends requires no excess dehydration and surfactant addition. Therefore, compared with the manufacture of conventional bio-alcohols, the energy consumption for the manufacture of water-containing butanol diesel blends is reduced, and the costs are lowered. In this study, we verified that using water-containing butanol diesel blends not only solves the tradeoff problem between nitrogen oxides (NOx) and particulate matter emissions from diesel engines, but it also reduces the emissions of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons, polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, polychlorinated diphenyl ethers, polybrominated dibenzo-p-dioxins and dibenzofurans, polybrominated biphenyls and polybrominated diphenyl ethers. After using blends of B2 with 10% and 20% water-containing butanol, the POP emission factors were decreased by amounts in the range of 22.6%−42.3% and 38.0%−65.5% on a mass basis, as well as 18.7%−78.1% and 51.0%−84.9% on a toxicity basis. The addition of water-containing butanol introduced a lower content of aromatic compounds and most importantly, lead to more complete combustion, thus resulting in a great reduction in the POP emissions. Not only did the self-provided oxygen of butanol promote complete oxidation but also the water content in butanol diesel blends could cause a microexplosion mechanism, which provided a better turbulence and well-mixed environment for complete combustion.

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INTRODUCTION An increasing energy demand and environmental pollution has motivated a search for bio-fuels, such as bio-diesels1,2 and bioalcohols,3,4 that can be used as alternative fuels for diesel engines. In general, both bio-diesel and bio-alcohols, such as ethanol and butanol, have the advantages of higher brake thermal efficiency (BTE) and lower emissions of particulate matter (PM), carbon monoxide (CO) and hydrocarbons (HC).5−7 However, bio-diesel produces greater amounts of nitrogen oxides (NOx) emissions than fossil diesel,6,8 whereas bio-alcohol has a greater potential to decrease NOx output because of its high vaporization heat.3,9 Butanol is preferable to ethanol for adoption in diesel engines because of its good solubility in diesel, its greater © 2014 American Chemical Society

heating value, its higher cetane number and miscibility and its lower vapor pressure.10−12 However, butanol is produced by the fermentation of biomass and has a high water content, which requires extra energy to dehydrate it for practical use. Furthermore, the energy demand for the dehydration process increases with the purity of the fuel. For example, in the production of bio-ethanol, increasing the purity of ethanol from 95% to 99.9% requires approximately 40% more energy than the total energy demand.13 Therefore, from the perspective of Received: Revised: Accepted: Published: 6010

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various water percentages (from 2.5% to 10%) of watercontaining butanols were prepared to blend with the commercial diesel in Taiwan, B2 (98% fossil diesel and 2% bio-diesel), as shown in Table S1 of the Supporting Information. The stability of the blend fuel is important both in this study and for future commercial applications. Therefore, watercontaining butanol diesel blends with different compositions were evaluated for their stability by both gravitational and centrifugal processes. The detailed procedure of the fuel blending and stability tests can be found in a previous study28 and is also described in the Supporting Information. After the stability test, the two stable fuel blends, which were WBT10 (0.25% water, 9.75% butanol and 90% B2) and WBT20 (0.5% water, 19.5% butanol and 80% B2), were selected to further evaluate the POP emissions from a diesel engine. The corresponding measurements were performed on B2 to determine the baseline emission. Diesel Engine and Test Cycle. The experiments were carried out with a six-cylinder, 6 L, naturally aspirated, watercooled, no EGR, direct-injection heavy-duty diesel engine (Hino W06E). The specifications of the diesel engine, including the engine compression ratio, type of fuel injection system and engine operating boundary conditions, are given in Table S2 (Supporting Information). An engine dynamometer (Schenck W230) was used to control the engine torque and speed. Diesel engine tests were monitored in four of the thirteen European Steady Cycle (ESC) modes: mode 1 (750 rpm, 0 Nm), mode 2 (1650 rpm, 360 Nm), mode 7 (1650 rpm, 90 Nm) and mode 11 (1950 rpm, 96.2 Nm). Mode 1 represents the idle condition, whereas the other three test modes represent 100%, 25% and 25% load, respectively. Sampling Procedures. To confirm the stability of the diesel engine, the fuels were tested in the following order: B2, WBT10, WBT20 and then repeated again. Before each sampling, the engine was warmed up for 30 min and for a minimum of 3 min between test modes. The engine was preconditioned for 30 min in mode 11 after each fuel change. The exhaust of the diesel engine was sampled directly and isokinetically during the entire testing cycle by a sampling system that consists of a glass fiber filter, a flow meter, a condenser, two-stage glass cartridges and a pump. Particulatephase pollutants were collected by a glass fiber filter. A condenser located before the two-stage glass cartridges was used to lower the exhaust temperature to < 5 °C and to remove the water content from the exhaust. The gaseous-phase pollutants were then collected by the two-stage glass cartridges. Specifically, the cartridges were packed with 5.0 cm (approximately 20 g) of XAD-2 resin sandwiched between two 2.5 cm polyurethane foam plugs. The samplings of the four ESC modes were combined into one exhaust sample to ensure that the pollutant contents were higher than the detection limit. The total sampling time was approximately 80 min (each ESC mode was approximately 20 min). Finally, the sampled flue gas volumes were normalized to the condition of 760 mmHg and 273 K and denoted as Nm3. Analytical Procedures. The sampled mass of PM was determined by weighing the filters on a Precisa XR 205SM-DR balance of sensitivity 0.01 mg. A Rosemount Model 951A NO/ NOx analyzer was used to monitor the NOx emissions in the exhaust. The detailed analytical procedures for NOx can be found in the Supporting Information, and the measurement

energy savings, leaving a small quantity of water in the biobutanol can reduce the energy consumption and CO2 emission. In addition, a small quantity of residual water in bio-butanol has been demonstrated to contribute to a higher energy efficiency and lower emissions of PM, NOx and polycyclic aromatic hydrocarbons (PAHs) than observed for pure butanol in a diesel engine test.14 The stability of fuel blends is an important issue that should be considered during fuel blend use. In a previous study, a mixture of fossil diesel and watercontaining butanol, which had 10% residual water in the butanol (that is, a purity of 90%), was found to be stable (onephase clear liquid) for 30 days, demonstrating that butanol is capable of stabilizing water in the lipophilic diesel.14 The pollutants emitted from diesel engines have been widely investigated for several decades.15,16 Compared to research on other pollutants, studies on the toxic and carcinogenic pollutants emitted from diesel engines are relatively few, even after their exhaust has been classified as Group 1, carcinogenic to humans, by the International Agency for Research on Cancer (IARC) in 2012. According to World Cancer Report 2014, the predicted number of cancer cases will be close to 24 million per year by 2035. Air pollution, as well as other environmental factors, is one of the major sources of preventable cancer.17 The toxic and carcinogenic persistent organic pollutants (POPs) found in the exhaust of diesel engines include PAHs,18,19 polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/ Fs),20,21 polychlorinated biphenyls (PCBs),21,22 polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs),23 and polybrominated diphenyl ethers (PBDEs).23,24 Among them, PBDE and PBDD/F emissions from diesel engines are still seldom investigated. Nevertheless, the reported relative mass concentrations in diesel engine exhaust were PBDEs ≫ PBDD/Fs > PCBs > PCDD/Fs.23 PBDEs are also brominated flame retardants (BFRs), used as the additives in electronic appliances, paints, textiles and furnishings and are commonly seen as pollutants released from the use of daily products. But the significant influence of combustion sources on atmospheric PBDEs has been uncovered.24−26 The mobile sources are identified as one of the major sources of atmospheric PBDEs, and the road transport sector contributed about 28% and 4.39% of the PBDE emission inventories from combustion sources in Taiwan and U.S., respectively.24 In this study, a water-containing butanol diesel blend was examined to evaluate its potential to decrease the POP emissions from diesel engines. Wenger et al. reported that PCDD/Fs and nine PAHs only contributed about 2% of the total agonist concentration obtained from aryl hydrocarbon receptor (AhR) mediated activity for exhaust emitted from a heavy-duty diesel engine.27 The other pollutants that also contribute the agonist concentration are not clarified. To gain a comprehensive view of the emissions of halogenated organic pollutants, an analytical method was developed in this study to simultaneously determine from a single exhaust sample the levels of several pollutants, including PAHs, PCDD/Fs, PCBs, polychlorinated diphenyl ethers (PCDEs), PBDD/Fs, polybrominated biphenyls (PBBs) and PBDEs. We are not aware of any study to date on the PCDEs and PBBs in the exhaust of diesel engines.

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METHODS AND MATERIALS Test Fuel. To simulate the butanol produced from a fermentation process without a complete dehydration process, 6011

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Table 1. Concentration of PM, NOx and POPs from the Diesel Engine Fueled with Water-Containing Butanol Diesel Blends B2

PM NOxa PAHs PCDD/Fs PCBs

PCDEs PBDD/Fs PBBs PBDEs a

mg/Nm3 ppm mass (μg/Nm3) total BaPeqb (μg/Nm3) mass(pg/Nm3) I-TEQc (pg I-TEQ/Nm3) mass (pg/Nm3) WHO-TEQd(pg WHOTEQ/Nm3) mass (pg/Nm3) mass (pg/Nm3) TEQe (pg TEQ/Nm3) mass (pg/Nm3) mass (ng/Nm3)

WBT10

WBT20

trail 1

trail 2

mean

RPD (%)

69.3 346 91.8 0.643 39.9 4.15 10.4 0.0802

71.8 357 99.8 0.549 46.6 4.81 14.7 0.0747

70.6 352 95.8 0.596 43.3 4.48 12.6 0.0775

3.54 3.12 8.35 15.8 15.5 14.8 34.3 7.10

29.3 287 56.7 0.152 27.1 2.31 8.34 0.0316

32.6 294 66.9 0.119 23.8 1.63 8.01 0.0406

31.0 291 61.8 0.136 25.5 1.97 8.18 0.0361

10.7 2.41 16.5 24.5 12.9 34.3 4.04 24.9

21.4 274 56.3 0.111 24.1 0.952 5.11 0.0127

20.1 281 57.2 0.0863 19.5 0.661 6.83 0.0106

20.8 278 56.8 0.0987 21.8 0.807 5.97 0.0117

6.27 2.52 1.59 25.1 21.1 36.1 28.8 18.4

ND 226 0.647 8.41 41.4

ND 192 0.484 10.9 37.3

ND 209 0.566 9.66 39.4

16.3 28.8 25.5 10.4

ND 152 0.537 6.17 35.0

ND 165 0.410 7.03 27.9

ND 159 0.474 6.60 31.5

8.20 26.8 13.0 22.6

ND 63.6 0.297 5.34 26.8

ND 78.5 0.252 6.57 21.7

ND 71.1 0.275 5.96 24.3

21.0 16.4 20.7 21.0

trail 1

trail 2

mean

RPD (%)

trail 1

trail 2

mean

RPD (%)

The measurement of NOx can be found in the Supporting Information. bTEF from Nisbet and LaGoy (1992).41 cTEF from I-TEFs (1988).42 TEF from WHO-TEFs (2005).43 eA tentative TEFs from I-TEFs of PCDD/Fs (WHO, 1998).44,45

d

for pure PAH standards. The PAHs were qualified by using the selected ion monitoring (SIM) mode. A high-resolution gas chromatography/high-resolution mass spectrometer (HRGC/HRMS) was used for the remaining persistent pollutant analyses. The HRGC (Hewlett-Packard 6970 Series gas, CA) was equipped with a silica capillary column (J&W Scientific, CA) and a splitless injector, while the HRMS (Micromass Autospec Ultima, Manchester, U.K.) was equipped with a positive electron impact (EI+) source. The SIM mode was used with a resolving power of 10 000. The electron energy and the source temperature were specified at 35 eV and 250 °C, respectively. Each analyte needs individual injection, i.e., one exhaust sample needs six injections for the analyses of PCDD/Fs, PCBs, PCDEs, PBDD/Fs, PBBs and PBDEs. The detailed instrumental analysis parameters are given in previous works.31−33 Quality Assurance and Quality Control (QA/QC). Prior to samplings, the glass fiber filters were placed in an oven at 450 °C for 8 h to burn off all organic pollutants. Field and laboratory blanks were carried out in this study. The mean total amounts of analytic POPs in the field and laboratory blank samples are given in Table S4 (Supporting Information). Compared with the corresponding exhaust samples, the POPs in these blank samples were all lesser than 0.5% of total POPs in the real samples, except for PBDEs, which were PCDD/Fs > PCBs > PBBs > PCDEs, which shares a similar trend with a previous study.23 PCDFs have been reported to form by the condensation of chlorophenols with chlorobenzenes via PCDEs;47 furthermore, PCDD/Fs can form from PCDEs by pyrolysis.48,49 Therefore, PCDEs should be an important precursor of PCDD/Fs. However, the concentrations of PCDEs are found to be significantly lower than those of PCDD/Fs in the exhaust of the diesel engine. Similar phenomena also have been reported in studies on simulated fly ash in a flow reactor system.50−52 The above phenomena should result from the competition between the formation of PCDEs and PCDD/Fs from their common precursors, such as chlorobenzenes, chlorophenol and surfaceassociate chlorophenoxyl.52 Another explanation is that during the reaction, PCDEs as intermediates are mostly converted into PCDD/Fs. De novo synthesis is one possible pathway to form PBDD/ Fs.53 However, the formation of PBDD/Fs from PBDE

B2

WBT10

WBT20

0.714 6.64 969 6.04 438 45.4 127 0.784 ND 2118 5.73 97.6 399

0.303 5.32 607 1.33 250 19.4 80.3 0.354 ND 1554 4.65 64.8 309

0.210 5.24 575 0.996 221 8.16 60.4 0.118 ND 720 2.78 60.2 245

precursors via elimination and debromination reactions, condensation or recombination of fragments is more important than that from de novo synthesis.54,55 In the current study, the PBDE concentrations were all much higher than those of the PBDFs and therefore, PBDEs could act as the available precursors for the formation of PBDFs in the diesel engine.54,55 Congener Profiles. Figure 1 shows the congener profiles of pollutants from the diesel engine fueled with B2, WBT10 and WBT20. The congener profiles of the B2 trial are consistent with those in a previous study,23 except for that of PAHs, which had lower fractions of the low molecular weight-PAHs (LMPAHs). For WBT10 and WBT20, the fractions of the LMPAHs were increased relative to B2 by 14.3% and 19.1%, respectively. As a result, the fractions of the middle and high molecular weight-PAHs (MM- and HM-PAHs) with greater toxicities were reduced. A similar result could be observed in the congener profiles of PCDD/Fs. The fractions of the lower chlorinated-substituted PCDFs, which were predominantly formed by de novo syntheses due to incomplete combustion, were decreased along with the increased quantities of watercontaining butanol in the blends. The results for PAHs and PCDD/Fs both revealed that the addition of water-containing butanol into diesel can enable a more complete combustion in the diesel engine. For other pollutants, however, there is no obvious influence on the congener profiles by adding watercontaining butanol diesel blends. The homologues of PCDEs (see Table S9, Supporting Information) clearly showed that only the tri-CDEs can be found in the exhaust of the diesel engine; this is contrary to the data for PCDD/Fs, which were dominated by highly chlorinated-substituted congeners. This distinction between the profiles of PCDEs and PCDD/Fs reveals that the PCDEs should be less related to the intermediates that are able to convert into PCDD/Fs. Therefore, the PCDE concentrations much lower than those of PCDD/Fs should be attributed to the results of competition for their common precursors, such as chlorobenzenes, chlorophenol and surface-associate chlorophenoxyl.52 On the other hand, the congener profiles of PCDEs and PBDEs are also completely different. The former is dominated by lower halogen-substituted homologues, whereas the latter consists of highly halogen-substituted homologues, revealing that different formation mechanisms occur between the PCDEs and the PBDEs. Contrary to the competition between the PCDEs and the PCDD/Fs, the much higher concentration of PBDEs and their assembling brominated patterns with PBDFs 6014

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indicate that the PBDEs are the precursors of PBDFs.23,25,55The reason that the close resemblance between the PBDD/Fs and the PBDEs is not observed for the PCDEs and PCDD/Fs is still not clear. Therefore, the relationships among the formation mechanisms of these four analogues require further investigation. It is also needed to mention that although PBDEs and PBDFs were abundant in highly brominated congeners in exhausts of diesel engine, the lower brominated congeners with higher toxicity and ability of bioaccumulation could be formed during the long-range transport due to that the properties of BDE-209 and OBDF lean to metabolically and photocatalytically debrominate to the lower substituted ones.56 Influence of Water-containing Butanol on the Emission Factors of Pollutants. Table 2 presents the mean emission factors (the individual emission factor of trail 1 and 2 are listed in Table S10, Supporting Information) of PM, NOx and the POPs from the diesel engine fueled separately with B2, WBT10 and WBT20. Our previous study also reported the emission factors of the same pollutants (except for PCDEs and PBBs) from the diesel engine fueled with B2 but with different test modes;23 except for PCBs, which were an order of magnitude lower, the other pollutants obtained from this study were higher, but still within an order of magnitude. Although in a different test mode, and although the fuel and the engine can affect the emission factors of pollutants,46 our values were at a similar level or within an order of magnitude of those of other studies, which reported the emission factors of PAHs,21,57−59 PCDD/Fs,20−22,60−62 and PCBs.21,60 However, the emission factors of PCBs from a turbo diesel engine (meeting the Euro III standard) that were 1−2 orders of magnitude higher22 and those of PBDEs from passenger vehicles that were 20 times lower24 have also been reported. To evaluate the effect of the percentage of water-containing butanol on the emissions of PM, NOx and POPs, the reduction rates of the emission factors of these pollutants were determined as follows:

Figure 2. Reduction rate of POPs based on (a) mass and (b) toxicity from the heavy-duty diesel engine by WBT10 and WBT20 relative to B2.

reduction rate (%) = (A − B)/A × 100%

where A are the emission factors of the PM, NOx and POPs from the heavy diesel engine fueled with B2, and B are those fueled with water-containing butanol diesel blends (WBT10 or WBT20). As shown in Figure 2, the PM and NOx emissions were simultaneously reduced by 57.5 ± 1.5% and 19.9 ± 0.3% after using WBT10 and were further reduced by 70.5 ± 1.4% and 21.1 ± 0.2% after using WBT20, respectively. The PM reductions obtained in this study (57.5%−70.5%) were higher or comparable to those in previous studies (20%−80%, as shown in Table S11, Supporting Information), which tested 10%−20% butanol diesel blends in diesel engines. For NOx, we find that water-containing butanol diesel blends can also reduce the NOx, while the NOx-PM tradeoff was observed for pure butanol diesel blends in previous studies,39,63 revealing that the small amount of water in the water-containing butanol diesel blends (0.25%−0.5%) may help to cool the combustion system, lower the locally high temperature and effectively inhibit thermal NOx formation.14 Regarding the POPs, the mass (or toxicity) emission factors were reduced by 37.5 ± 2.6% (toxicity: 78.1 ± 1.0%) for PAHs, 42.3 ± 8.2% (56.4 ± 10.5%) for PCDD/Fs, 34.4 ± 12.5% (54.6 ± 7.3%) for PCBs, 25.9 ± 9.0% (18.7 ± 0.83%) for PBDD/F, 33.0 ± 4.2% for PBBs and 22.6 ± 4.7% for PBDEs when the

diesel engine was fueled with WBT10. The levels of these pollutants were then further decreased by 40.7 ± 2.0% (toxicity: 83.6 ± 0.77%) for PAHs, 48.9 ± 9.3% (81.7 ± 4.6%) for PCDD/Fs, 52.0 ± 1.3% (84.9 ± 0.82%) for PCBs, 65.5 ± 6.37% (51.0 ± 3.1%) for PBDD/F, 38.0 ± 1.5% for PBBs and 38.6 ± 3.3% for PBDEs when the diesel engine was fueled with WBT20 instead of B2. The reductions in the POP emission factors were proportional to the percentage of watercontaining butanol in the blends. Altogether, using WBT10 and WBT20 as fuels can reduce these emission factors in the range of 22.6%−42.3% and 38.0%−65.5% on a mass basis, as well as 18.7%−78.1% and 51.0%−84.9% on a toxicity basis. In theory, the reduction of PAH emissions by blending water-containing butanol into diesel should be approximately 10%−20%, if the lower PAH emissions were resulted from a lower concentration of aromatic contents in the blends. Therefore, the much higher reduction in PAH emissions, especially for BaPeq, should result from the more complete combustion achieved by using water-containing butanol diesel blend. Taking PCDD/Fs for further discussion, the reduction of the lower chlorinated-substituted PCDFs (i.e., 2,3,7,8TeCDF, 1,2,3,7,8-PeCDF and 2,3,4,7,8-PeCDF) were 71% 6015

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and 86% by using the WBT10 and WBT20, whereas those of total PCDD/Fs were 42.3% and 48.9%. We know that the lower chlorinated-substituted PCDFs are predominantly formed by de novo syntheses due to incomplete combustion. Therefore, the higher reduction of the lower chlorinatedsubstituted PCDFs should be due to the more complete combustion by using water-containing butanol diesel blends. Furthermore, the POP reductions were all much greater than 10%−20%, and should be not due to POP reductions resulted from part of diesel replaced by water-containing butanol. Although we had not analyzed the POP contents in the diesel, the above results revealed that POP emissions from the diesel engine are really formed as a result of combustion instead of being already present as impurities in the fuel. The reasons that using water-containing butanol diesel blends could result in more complete combustion and inhibition of the de novo synthesis of these POPs, are related to the combination effect of butanol and the addition of 0.5% of water. Although the individual influence of butanol and water on leaning to complete combustion could not be evaluated in this study, we know that oxygenate fuel like butanol can promote complete oxidation because of the self-provided oxygen.64 Furthermore, both the relatively lower viscosity and cetane number of the butanol compared with the diesel fuel (see Table 3) could have better atomization65,66 and a longer ignition delay,3,10 respectively, improving the fuel-air mixing, which could also result in more complete combustion.

Our previous study found that even though the chlorine content in the waste cooking oil-based bio-diesel (WCO-based bio-diesel) was 5 times higher than that of fossil diesel, a significantly decline in PCDD/F and PCB emissions was observed after using WCO-based bio-diesel blends.23 Furthermore, the chlorine intake via ambient air could be much larger than that via fuel.67 As for bromine, it also presents in all fossil fuels, but in very minor content. The Br/Cl mass ratio in coal is normally about only 0.01−0.04.68 Therefore, bromine contents in the fuel should also not be a factor affecting the brominated POP emissions from diesel engines. In summary, the use of water-containing butanol diesel blends in a diesel engine can simultaneously reduce NOx and PM emissions, and further, it can solve the PM-NOx tradeoff issue for oxygenated fuels. Additionally, the addition of watercontaining butanol introduced a lower content of aromatic compounds and most importantly, leaded to more complete combustion, thus resulting in a great reduction in the POP emissions.

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S Supporting Information *

Analyses of the PM and NOx; tables showing stability tests of water-containing butanol blends, specifications of the tested engine, NOx concentrations in the exhaust of the diesel engine under different test modes, field and laboratory blank results, the internal standards used in this study, recovery of standards and their corresponding criteria, PM and NOx concentrations in the exhausts of diesel engines, POP concentrations in the exhaust of the diesel engine fueled with B2 under different test mode, PCDEs emissions and detection limit (n = 2) for each test class by chlorine-substituted congeners and homologues, the emission factors of PM, NOx and POPs from a diesel engine based on brake horse power, and PM and NOx reduction by using butanol diesel blends. This material is available free of charge via the Internet at http://pubs.acs.org.

Table 3. Properties of Regular Diesel and Butanol

a

properties

diesel

butanol

lower calorific value (MJ/kg) latent heat of vaporizationa (kJ/kg) cetane numbera kinematic viscosity at 40 °Ca (mm2/s) oxygen content (wt %) aromatic content (%)

43.5 250 50 2.70 0 27.1

32.2 585 ∼25 2.22 21.6 ND (