Biomass-derived Oxymethylene Ethers as Diesel Additives: A Thermodynamic Analysis

Conversion of biomass for production of liquid fuels can help in reducing the greenhouse gas (GHG) emissions which are predominantly generated by combustion of fossil fuels. Adding oxymethylene ethers (OMEs) in conventional diesel fuel has the potential to reduce soot formation during the combustion in a diesel engine. OMEs are downstream products of syngas, which can be generated by the gasification of biomass. In this research, a thermodynamic analysis has been conducted through development of data intensive process models of all the unit operations involved in production of OMEs from biomass. Based on the developed model, the key process parameters affecting the OMEs production including equivalence ratio, H2/CO ratio, and extra water flow rate were identified. This was followed by development of an optimal process design for high OMEs production. It was found that for a fluidized bed gasifier with heat capacity of 28 MW, the conditions for highest OMEs production are at an air amount of 317 tonne/day, at H2/CO ratio of 2.1, and without extra water injection. At this level, the total OMEs production is 55 tonne/day (13 tonne/day OME3 and 9 tonne/day OME4). This model would further be used in a techno-economic assessment study of the whole biomass conversion chain to determine the most attractive pathways.

Biomass-derived oxymethylene ethers as diesel additives: A techno-economic assessment

Conversion of agricultural biomass such as wood chips, wheat straw and forest residue for the production of fuels can help in reducing GHG emissions since they are considered as nearly carbon neutral. Around the world there is a significant amount of forest and agricultural-biomass available which could be used for the production of liquid fuels that can be blended with the petroleum-based diesel. Oxymethylene ethers (OMEs) can be derived from biomass via gasification, water-gas shift reaction and methanol production. The addition of OMEs to conventional diesel fuel has great potential to reduce soot formation during the combustion in diesel engines. Unlike methanol and dimethyl ether (DMM) which can also reduce soot formation, the physical properties of OMEs allow the use in modern diesel engines without significant change of the engines infrastructure. In this study, a detailed and data intensive process simulation model was developed to simulate all the unit operations involved in the production of OMEs from biomass. The unit operation considered include biomass drying, gasification, gas cleaning, water gas shift reaction, methanol production and OMEs synthesis. The simulation results were then utilized to conduct a detailed techno-economic assessment study of the whole biomass conversion chain to determine the most attractive pathways for OMEs production. Our recent study shows that the key parameters affecting the OMEs production are equivalence ratio, H2/CO ratio and optimal air flow. Overall, the cost of production ($/liter) of OMEs from different biomass feedstock in Alberta will be determined

An optimized process design for oxymethylene ether production from woody-biomass-derived syngas

The conversion of biomass for the production of liquid fuels can help reduce the greenhouse gas (GHG) emissions that are predominantly generated by the combustion of fossil fuels. Oxymethylene ethers (OMEs) are a series of liquid fuel additives that can be obtained from syngas, which is produced from the gasification of biomass. The blending of OMEs in conventional diesel fuel can reduce soot formation during combustion in a diesel engine. In this research, a process for the production of OMEs from woody biomass has been simulated. The process consists of several unit operations including biomass gasifi- cation, syngas cleanup, methanol production, and conversion of methanol to OMEs. The methodology involved the development of process models, the identification of the key process parameters affecting OME production based on the process model, and the development of an optimal process design for high OME yields. It was found that up to 9.02 tonnes day1 of OME3, OME4, and OME5 (which are suitable as diesel additives) can be produced from 277.3 tonnes day1 of wet woody biomass. Furthermore, an optimal combination of the parameters, which was generated from the developed model, can greatly enhance OME production and thermodynamic efficiency. This model can further be used in a techno- economic assessment of the whole biomass conversion chain to produce OMEs. The results of this study can be helpful for petroleum-based fuel producers and policy makers in determining the most attractive pathways of converting bio-resources into liquid fuels.

Concentrations of polybrominated diphenyl ethers (PBDEs) in matched samples of human milk, dust and indoor air

Polybrominated diphenyl ethers (PBDEs) are lipophilic, persistent pollutants found worldwide in environmental and human samples. Exposure pathways for PBDEs remain unclear but may include food, air and dust. The aim of this study was to conduct an integrated assessment of PBDE exposure and human body burden using 10 matched samples of human milk, indoor air and dust collected in 2007–2008 in Brisbane, Australia. In addition, temporal analysis was investigated comparing the results of the current study with PBDE concentrations in human milk collected in 2002–2003 from the same region. PBDEs were detected in all matrices and the median concentrations of BDEs -47 and -209 in human milk, air and dust were: 4.2 and 0.3 ng/g lipid; 25 and 7.8 pg/m3; and 56 and 291 ng/g dust, respectively. Significant correlations were observed between the concentrations of BDE-99 in air and human milk (r = 0.661, p = 0.038) and BDE-153 in dust and BDE-183 in human milk (r = 0.697, p = 0.025). These correlations do not suggest causal relationships — there is no hypothesis that can be offered to explain why BDE-153 in dust and BDE-183 in milk are correlated. The fact that so few correlations were found in the data could be a function of the small sample size, or because additional factors, such as sources of exposure not considered or measured in the study, might be important in explaining exposure to PBDEs. There was a slight decrease in PBDE concentrations from 2002–2003 to 2007–2008 but this may be due to sampling and analytical differences. Overall, average PBDE concentrations from these individual samples were similar to results from pooled human milk collected in Brisbane in 2002–2003 indicating that pooling may be an efficient, cost-effective strategy of assessing PBDE concentrations on a population basis. The results of this study were used to estimate an infant's daily PBDE intake via inhalation, dust ingestion and human milk consumption. Differences in PBDE intake of individual congeners from the different matrices were observed. Specifically, as the level of bromination increased, the contribution of PBDE intake decreased via human milk and increased via dust. As the impacts of the ban of the lower brominated (penta- and octa-BDE) products become evident, an increased use of the higher brominated deca-BDE product may result in dust making a greater contribution to infant exposure than it does currently. To better understand human body burden, further research is required into the sources and exposure pathways of PBDEs and metabolic differences influencing an individual's response to exposure. In addition, temporal trend analysis is necessary with continued monitoring of PBDEs in the human population as well as in the suggested exposure matrices of food, dust and air.

Higher accumulation of polybrominated diphenyl ethers in infants than in adults

Pooled serum samples collected from 8132 residents in 2002/03 and 2004/05 were analyzed to assess human polybrominated diphenyl ether (PBDE) concentrations from specified strata of the Australian population. The strata were defined by age (0−4 years, 5−15 years, < 16 years, 16−30 years, 31−45 years, 46−60 years, and >60 years); region; and gender. For both time periods, infants and older children had substantially higher PBDE concentrations than adults. For samples collected in 2004/05, the mean ± standard deviation ΣPBDE (sum of the homologue groups for the mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, and deca-BDEs) concentrations for 0−4 and 5−15 years were 73 ± 7 and 29 ± 7 ng g−1 lipid, respectively, while for all adults >16 years, the mean concentration was lower at 18 ± 5 ng g−1 lipid. A similar trend was observed for the samples collected in 2002/03, with the mean ΣPBDE concentration for children <16 years being 28 ± 8 ng g−1 lipid and for the adults >16 years, 15 ± 5 ng g−1 lipid. No regional or gender specific differences were observed. Measured data were compared with a model that we developed to incorporate the primary known exposure pathways (food, air, dust, breast milk) and clearance (half-life) data. The model was used to predict PBDE concentration trends and indicated that the elevated concentrations in infants were primarily due to maternal transfer and breast milk consumption with inhalation and ingestion of dust making a comparatively lower contribution.

Serum polybrominated diphenyl ethers (PBDE) in pooled serum are higher in children (2-5 years of age) than in infants and adults

Background: Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in many products and have been detected in human samples worldwide. Limited data show that concentrations are elevated in young children. Objectives: We investigated the association between PBDEs and age with an emphasis on young children from Australia in 2006–2007. Methods: We collected human blood serum samples (n = 2,420), which we stratified by age and sex and pooled for analysis of PBDEs. Results: The sum of BDE-47, -99, -100, and -153 concentrations (Σ4PBDE) increased from 0–0.5 years (mean ± SD, 14 ± 3.4 ng/g lipid) to peak at 2.6–3 years (51 ± 36 ng/g lipid; p < 0.001) and then decreased until 31–45 years (9.9 ± 1.6 ng/g lipid). We observed no further significant decrease among ages 31–45, 45–60 (p = 0.964), or > 60 years (p = 0.894). The mean Σ4PBDE concentration in cord blood (24 ± 14 ng/g lipid) did not differ significantly from that in adult serum at ages 15–30 (p = 0.198) or 31–45 years (p = 0.140). We found no temporal trend when we compared the present results with Australian PBDE data from 2002–2005. PBDE concentrations were higher in males than in females; however, this difference reached statistical significance only for BDE-153 (p = 0.05). Conclusions: The observed peak concentration at 2.6–3 years of age is later than the period when breast-feeding is typically ceased. This suggests that in addition to the exposure via human milk, young children have higher exposure to these chemicals and/or a lower capacity to eliminate them. Key words: Australia, children, cord blood, human blood serum, PBDEs, polybrominated diphenyl ethers. Environ Health Perspect 117:1461–1465 (2009). doi:10.1289/ehp.0900596

Assessing exposure to polybrominated diphenyl ethers (PBDEs) for workers in the vicinity of a large recycling facility

Increased levels of polybrominated diphenyl ethers (PBDEs) can occur particularly in dust and soil surrounding facilities that recycle products containing PBDEs. This may be the source of increased exposure for nearby workers and residents. To investigate, we measured PBDE levels in soil, office dust and blood of workers at the closest workplace (i.e. within 100m) to a large automotive shredding and metal recycling facility in Brisbane, Australia. The workplace investigated in this study was independent of the automotive shredding facility and was one of approximately 50 businesses of varying types within a relatively large commercial/industrial area surrounding the recycling facility. Concentrations of PBDEs in soils were at least an order of magnitude greater than background levels in the area. Congener profiles were dominated by larger molecular weight congeners; in particular BDE-209. This reflected the profile in outdoor air samples previously collected at this site. Biomonitoring data from blood serum indicated no differential exposure for workers near the recycling facility compared to a reference group of office workers, also in Brisbane. Unlike air, indoor dust and soil sample profiles, serum samples from both worker groups were dominated by congeners BDE-47, BDE-153, BDE-99, BDE-100 and BDE-183 and was similar to the profile previously reported in the general Australian population. Estimated exposures for workers near the industrial point source suggested indoor workers had significantly higher exposure than outdoor workers due to their exposure to indoor dust rather than soil. However, no relationship was observed between blood PBDE levels and different roles and activity patterns of workers on-site. These comparisons of PBDE levels in serum provide additional insight into the inter-individual variability within Australia. Results also indicate congener patterns in the workplace environment did not match blood profiles of workers. This was attributed to the relatively high background exposures for the general Australian population via dietary intake and the home environment.

Assessment of polybrominated diphenyl ethers (PBDEs) in samples collected from indoor environments in South East Queensland, Australia

Polybrominated diphenyl ethers (PBDEs) are compounds that are used as flame retardants. Human exposure is suggested to be via food, dust and air. An assessment of PBDE exposure via indoor environments using samples of air, dust and surface wipes from eight sites in South East Queensland, Australia was conducted. For indoor air, ΣPBDEs ranged from 0.5 -179 pg/m3 for homes and 15 - 487 pg/m3 for offices. In dust, ΣPBDEs ranged from 87 - 733 ng/g dust and 583 - 3070 ng/g dust in homes and offices, respectively. PBDEs were detected on 9 out of 10 surfaces sampled and ranged from non-detectable to 5985 pg/cm2. Overall, the congener profiles for air and dust were dominated by BDE-209. This study demonstrated that PBDEs are ubiquitous in the indoor environments of selected buildings in South East Queensland and suggest the need for detailed assessment of PBDE concentrations using more sites to further investigate the factors influencing PBDE exposure in Australia.

Polybrominated diphenyl ethers and age: analysis of pooled human blood serum from birth to over 60 years

Polybrominated diphenyl ethers (PBDEs) are considered to be a cost effective and efficient way to reduce flammability therefore reducing harm caused by fires. PBDEs are incorporated into a variety of manufactured products and are found worldwide in biological and environmental samples (e.g. Hites et al. 2004). Unlike other persistent organic pollutants there is limited data on PBDE concentrations by age and/or other population specific factors. Some studies have shown no variation in adult serum PBDE concentrations with age (e.g. Mazdai et al., 2003, Meironyte Guvenius et al., 2003) while Petreas et al. (2003) and Schecter et al. (2005) found results to be suggestive of an age trend in adult data but no statistically significant correlation was found. In addition to the data on adult concentrations there is limited data which investigates the levels of PBDEs in infants and young children. Fangström et al. (2005) showed that in seven year olds there was no difference in PBDE concentration when compared to adult concentrations. While Thomsen et al. (2002, 2005) found the concentration of PBDEs in pooled samples of blood serum from a 0-4 years age group to be higher than other age groups (4 to > 60 years). In addition, a family of four was studied in the U.S. and the concentrations were found to be greatest in the 18-month-old infant followed by the 5 year old child, then the mother and father (Fischer et al., 2006). The objectives of this study were to assess age, gender and regional trends of PBDE concentrations in a representative sample of the Australian population.

Organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) in the Australian population: Levels in human milk

This study arose out of the 2002 Review of the PCB Management Plan by the Scheduled Waste Management Network (SWMN) and the National Advisory Body (NAB). The Review indicated it would be beneficial to obtain some data on the levels of organochlorine pesticides (OCPs) in the Australian population. In 2002, the Environment Protection and Heritage Standing Committee (EPHSC) agreed and noted that the Australian Government Department of the Environment and Heritage (DEH) would commission a study using the same samples from the National Dioxins Program (NDP) breast milk study collected in 2002- 03. The study, however, was also broadened to include polybrominated diphenyl ethers (PBDEs).

Polybrominated diphenyl ethers (PBDEs) in dust from primary schools in South East Queensland, Australia

PBDE concentrations are higher in children compared to adults with exposure suggested to include dust ingestion. Besides the home environment, children spend a great deal of time in school classrooms which may be a source of exposure. As part of the “Ultrafine Particles from Traffic Emissions and Children's Health (UPTECH)” project, dust samples (n=28) were obtained in 2011/12 from 10 Brisbane, Australia metropolitan schools and analysed using GC and LC–MS for polybrominated diphenyl ethers (PBDEs) -17, -28, -47, -49, -66, -85, -99, -100, -154, -183, and -209. Σ11PBDEs ranged from 11–2163 ng/g dust; with a mean and median of 600 and 469 ng/g dust, respectively. BDE-209 (range n.d. −2034 ng/g dust; mean (median) 402 (217) ng/g dust) was the dominant congener in most classrooms. Frequencies of detection were 96%, 96%, 39% and 93% for BDE-47, -99, -100 and -209, respectively. No seasonal variations were apparent and from each of the two schools where XRF measurements were carried out, only two classroom items had detectable bromine. PBDE intake for 8–11 year olds can be estimated at 0.094 ng/day BDE-47; 0.187 ng/day BDE-99 and 0.522 ng/day BDE-209 as a result of ingestion of classroom dust, based on mean PBDE concentrations. The 97.5% percentile intake is estimated to be 0.62, 1.03 and 2.14 ng/day for BDEs-47, -99 and -209, respectively. These PBDE concentrations in dust from classrooms, which are higher than in Australian homes, may explain some of the higher body burden of PBDEs in children compared to adults when taking into consideration age-dependant behaviours which increase dust ingestion.

A New, Convenient Reductive Procedure For The Deprotection Of 4-Methoxybenzyl (Mpm) Ethers To Alcohols

Selective introduction and removal of protecting groups is of great significance in organic synthesis.l The benzyl ether function is one of the most common protecting groups for alcohols. Selective oxidative removal of the 4-methoxybenzyl (MPM) ethers in the presence of benzyl ethers made the MPM moiety an alternative protecting group, and its utility in carbohydrate chemistry is well established. Several procedures have been developed for the cleavage of the 4-methoxybenzyl moiety, e.g. DDQ oxidation (eq 1),2e lectrochemical ~xidationh,~om ogeneous electron t r a n~f e rp,~ho toinduced single electron t r an~f e rb,o~ro n trichloride-dimethyl sulfide,6e tc. However, in all these methods isolation of the alcohol from the inevitable byproduct, 4-methoxybenzaldehyde [also dichlorodicyanohydroquinone (DDHQ) in the most commonly used method employing DDQI can be troublesome. Recently Wallace and Hedgetts7 discovered that acetic acid at 90 "C cleaves the aromatic MPM ethers into the corresponding phenols and 4-methoxybenzyl acetate (eq 21, whereas the aliphatic MPM ethers generated, instead of alcohols, the corresponding acetates (eq 3). Complimentary to this methodology, herein we report that sodium cyanoborohydride and boron trifluoride etherate reductively cleaves, cleanly and efficiently, the aliphatic MPM ethers to an easily separable mixture of the corresponding alcohols and 4-methylanisole