Aromatic Fuels Research Articles

Cleavage of aryl-ether bonds in lignin model compounds using a Co-Zn-beta catalyst.

Efficient cleavage of aryl–ether linkages is a key strategy for generating aromatic chemicals and fuels from lignin. Currently, a popular method to depolymerize native/technical lignin employs a combination of Lewis acid and hydrogenation metal. However, a clear mechanistic understanding of the process is lacking. Thus, a more thorough understanding of the mechanism of lignin depolymerization in this system is essential. Herein, we propose a detailed mechanistic study conducted with lignin model compounds (LMC) via a synergistic Co–Zn/Off-Al H-beta catalyst that mirrors the hydrogenolysis process of lignin. The results suggest that the main reaction paths for the phenolic dimers exhibiting α-O-4 and β-O-4 ether linkages are the cleavage of aryl–ether linkages. Particularly, the conversion was readily completed using a Co–Zn/Off-Al H-beta catalyst, but 40% of α-O-4 was converted and β-O-4 did not react in the absence of a catalyst under the same conditions. In addition, it was found that the presence of hydroxyl groups on the side chain, commonly found in native lignin, greatly promotes the cleavage of aryl–ether linkages activated by Zn Lewis acid, which was attributed to the adsorption between Zn and the hydroxyl group. Followed by the cobalt catalyzed hydrogenation reaction, the phenolic dimers are degraded into monomers that maintain aromaticity.

Experimental and kinetic modeling study on 1,3-cyclopentadiene oxidation and pyrolysis

The oxidation of 1,3-cyclopentadiene (c-C5H6), a key intermediate formed in the combustion of aromatic and cyclic hydrocarbon fuels and formation of polycyclic aromatic hydrocarbons (PAHs), was studied in a jet-stirred reactor (JSR) under the pressure of 0.1 MPa and temperatures from 623 to 1073 K with three equivalence ratios (φ = 0.5, 1.0 and 1.8). The mole fraction profiles of 25 oxidation products including light hydrocarbons, oxygenated and aromatic species were identified and quantified using online synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) with uncertainties of C, H, and O molar balances about 24%, 20% and 14%, respectively. A detailed kinetic model with 245 species and 1638 reactions was constructed based on the theoretical calculation and reported models in literature and validated with the new JSR oxidation data in this work. The dominant consumption channels of 1,3-cyclopentadiene are through H-atom abstraction reactions by OH, HO2 and CH3 radicals to produce cyclopentadienyl radical (c-C5H5) under all equivalence ratios and the contribution of CH3 attacking increases from φ = 0.5 to 1.8. Subsequently, the c-C5H5 is consumed via the reactions with HO2 and O2 to form small molecule and the recombination reaction with c-C5H6 to yield PAHs. Furthermore, the current model was also validated with a wide range of experimental data in literature of 1,3-cyclopentadiene combustion, including the species concentration profiles in flow reactors pyrolysis and oxidation.

Numerical simulations of yield-based sooting tendencies of aromatic fuels using ReaxFF molecular dynamics

We present the first ReaxFF Molecular Dynamics (MD) simulations to quantitatively predict the sooting tendencies of various fuels. The specific sooting tendency metric used in this work is the Yield Sooting Index (YSI), which quantifies the effects of fuel molecular structure on soot yield. YSI has been experimentally measured and numerically simulated using computational fluid dynamics for a large range of fuels, but there is no existing reactive MD framework for YSI simulations. To adopt the experimental YSI concept, a multi-stage simulation procedure is designed using ReaxFF. As a proof-of-concept, toluene and phenol are selected as test fuels, since both have relatively well-understood reaction pathways. The ReaxFF YSI simulations are shown to capture key reaction events for both fuels selected that are consistent with existing chemical kinetic understanding. Toluene is shown to mostly retain its original aromatic ring structure and directly grow to larger aromatic compounds with multiple rings. On the other hand, the aromatic growth process from phenol is accompanied by carbon-loss reactions with CO release. In addition, a quantitative YSI formulation is also derived in ReaxFF and the ReaxFF-predicted YSI values are compared with measurement data and reasonably good agreement is achieved. The results reported in this work demonstrates that the ReaxFF-based framework can potentially be used to quantitatively predict the relative sooting tendencies, especially for fuels with unknown or poorly-known chemistry, to understand their sooting properties and in search for soot relevant reaction pathways from these fuels.

Experimental and modeling study of benzaldehyde oxidation

Benzaldehyde is an aromatic aldehyde commonly considered in bio-oil surrogate formulation, and an important intermediate in the oxidation of other aromatic reference fuels such as toluene. However, its oxidation has never been previously investigated experimentally and no product formation profiles were reported in the very limited pyrolysis studies available in the literature. In this study, the gas-phase oxidation of benzaldehyde was investigated in a jet-stirred reactor. 48 species were detected using gas chromatography, mainly CO, CO2 and phenol. The important formation of CO and phenol indicates a rapid formation of phenyl radicals. This was confirmed by a kinetic analysis performed using the current version of the CRECK kinetic model, in which the reactions of phenyl radicals and oxygenated aromatic compounds have been updated.

Experimental and kinetic modeling investigation on sec-butylbenzene combustion: Flow reactor pyrolysis and laminar flame propagation at various pressures

This work reports the investigation on pyrolysis and laminar flame propagation of sec-butylbenzene. The pyrolysis experiments were performed in a flow reactor using synchrotron vacuum ultraviolet photoionization mass spectrometry from 780 to 1166 K at 0.04 and 1 atm. The pyrolysis products were identified and their mole fraction profiles versus the heating temperature were evaluated. The laminar burning velocities of sec-butylbenzene/air mixtures were measured at the initial temperature of 423 K and initial pressures of 1–10 atm in a high-pressure constant-volume cylindrical combustion vessel with the equivalence ratio from 0.7 to 1.5. Furthermore, a kinetic model was developed to predict the pyrolysis and laminar flame propagation of sec‑butylbenzene. Validation of the present model was performed against the new experimental data in this work. Rate of production analysis and sensitivity analysis were performed to provide insight into the chemistry in fuel decomposition and polycyclic aromatic hydrocarbons (PAHs) formation. In the flow reactor pyrolysis, the consumption of sec‑butylbenzene is mainly controlled by the unimolecular decomposition reactions and H-atom abstraction reactions at both low and atmospheric pressures. Fuel specific pathways through propenylbenzene and α-methylstyrene become the dominant formation pathways of indene and naphthalene. In the laminar flame propagation, the laminar burning velocity of sec‑butylbenzene is sensitive to the reactions of both small species and fuel-relevant intermediates under all investigated conditions. In particular, the pyrolysis reactions in the fuel sub-mechanism play inhibition effects on the laminar flame propagation of sec‑butylbenzene under rich conditions. The laminar burning velocity of sec‑butylbenzene is also compared with benzene, toluene and ethylbenzene under same initial conditions. Both the thermodynamic and kinetic effects are responsible for the difference in laminar burning velocities of these aromatic fuels.

Impacts of gasoline aromatic and ethanol levels on the emissions from GDI vehicles: Part 2. Influence on particulate matter, black carbon, and nanoparticle emissions

Fuel composition plays an important role on the particulate matter (PM) emissions formation from gasoline direct injection (GDI) engines. In this study, the impacts of gasoline chemical structure and physical properties on the particulate emissions were assessed for a fleet of five Tier 3 compliant GDI vehicles. All vehicles were tested on eight fuels with varying aromatic and ethanol levels, as well as varying PM indices (PMIs) over the LA92 test cycle in at least duplicate on each of the test fuels. Our results showed strong, statistically significant fuel differences for the weighted PM mass emissions and all three phases of the LA92 cycle. The higher aromatic content fuels showed increases in PM mass and black carbon emissions that were statistically significant compared to the lower aromatic fuels. The fuels with higher PMIs showed an upward, but not statistically significant, trend for PM mass emissions with increasing ethanol content likely due to ethanol’s evaporative charge cooling effect. This observation does not hold true for the lower PMI fuels. Similar trends to the weighted PM mass emissions were also seen for the cold-start and hot-running PM mass emissions, as well as for the weighted black carbon emissions, indicating a possible ethanol reinforcing effect on PM formation for the high PMI fuels. Total and solid particle number emissions also showed increases with the higher aromatic fuels compared to the lower aromatic fuels. Similar to PM mass, both total and solid particle number emissions demonstrated an upward trend for the high PMI fuels with an increase in ethanol content. While the study is consistent with other studies showing that increasing aromatics and PMI values lead to higher PM emissions, the results also suggest that this relationship is complicated by the presence of varying levels of ethanol in high aromatic and PMI fuels, where increasing levels of ethanol in these fuels can also lead to PM increases. High molecular weight and low volatility hydrocarbon species (especially aromatics) also strongly impacted particulate emissions formation in GDI vehicles.

Relationship between Fuel Properties and Cetane Response of Cetane Improver for Non-Aromatic and Aromatic Fuels Used In A Single Cylinder Heavy Duty Diesel Engine

Ignition improver additives are used to improve the ignition quality, or reduce the ignition delay; i.e. the time between when fuel is injected and time when combustion start is different this difference in time is minimize by additive is called cetane improver (CN). The Cetane Number (CN) is the most widely accepted measure of ignition quality to get desired value of centane number some additive are used hence ignition improvers are usually characterized by the fact that at what extent they can increase CN. By increasing cetane number we have two benefits that it helps smoother combustion and lower emissions. Fuel properties are always considered as one of the main factors to diesel engines concerning performance of cetane improver. There are still challenges for researchers to identify the most correlating and non-correlating fuel properties and their effects on cetane improver .In this study to derive the most un-correlating and correlating properties. In parallel, sensitivity analysis was performed for the fuel properties as well as to effect on performance of cetane improver

Optimization of Lignin Extraction from Pine Wood for Fast Pyrolysis by Using a γ-Valerolactone-Based Binary Solvent System

Fast pyrolysis of lignin is a promising method to produce aromatic chemicals and fuels. Lignin structure and pyrolysis conditions determine the liquid yield and product selectivity. Extraction of p...

Role of Singlet Oxygen in Combustion Initiation of Aromatic Fuels

Application of singlet oxygen in oxy-fuel systems reduces the activation energy of the initiation reactions, accelerating the chain-branching mechanism and decreasing the overall ignition temperature. However, the underlining reaction mechanism of the surface-generated singlet oxygen O2 1Δg that reacts with fuel surrogates (i.e., toluene) in the gas media remains poorly explored. Herein, comprehensive mechanistic and thermo-kinetic accounts underpinning the reaction of the simplest alkylbenzene, namely, toluene, with singlet oxygen in the gas phase are reported. In analogy to reaction of singlet oxygen with benzene, the titled reaction branches into several opening channels. The 1,4 cycloaddition and ene type reactions of toluene with singlet oxygen affords p-quinonemethide (4-methylenecyclohexa-2,5-dienone) and o-quinonemethide (6-methylenecyclohexa-2,4-dienone), respectively (i.e., very reactive intermediates). The initiation of the para channel follows a concerted mechanism through an enthalpic barrier...

Effects of fuel-bound methyl groups and fuel flow rate in the diffusion flames of aromatic fuels on the formation of volatile PAHs

Aromatic hydrocarbons constitute a significant fraction of fossil-derived transportation fuels. They are also used as additives to suppress autoignition and to increase fuel energy density. However, they produce harmful polycyclic aromatic hydrocarbons (PAHs) and soot during combustion. In this work, the effects of methyl group(s) and the flow rate of aromatic fuels (benzene, toluene, and m-xylene) on the concentration of volatile PAHs bound to soot formed in diffusion flames are studied. Soxhlet extraction using dichloromethane as the solvent is used to extract PAHs from soot particles collected from the flames of aromatic fuels. The extracts are analyzed using a gas chromatograph coupled to a mass spectrometer. Among the sixteen priority PAHs, fifteen of them are detected on soot particles along with benzo(e)pyrene and other organic compounds such as oxygenated compounds and mono-aromatic hydrocarbons. The PAHs containing two to three aromatic rings were found to be in higher concentrations than those with four or more rings. The total amount of PAHs collected at different fuel flow rates from the three aromatic fuels increased marginally in the following order: benzene < toluene < m-xylene. With increasing fuel flow rate, while the soot emission increased drastically, the concentration of volatile PAHs increased nearly linearly at a very slow rate. The toxicity of soot particles from different flames with increasing fuel flow rate is also reported.

Soot Particle Size Distribution Measurements in Laminar Diffusion Flames of n-Heptane with Oxygenated Aromatic Fuel Additives by Time-Resolved Laser-Induced Incandescence

Soot particle size profiles of a laminar co-flow diffusion flame were determined using time-resolved laser-induced incandescence (TiRe-LII) for various fuels. In the fuel matrix, both the level (0–...

Modelling analysis of PAH and soot measured in a premixed toluene-doped methane flame

A detailed gas-phase kinetic model coupled with a multi-sectional approach for the particle phase was used for inferring the effect of toluene addition on the sooting structure of a fuel-rich laminar premixed methane flame. Premixed methane flames at different C/O ratios established the reference environments to gain insight on the influence of toluene addition.Experimental data derived from a detailed analysis of the combustion aerosol sampled along the methane flame and the toluene-doped flame, burning in similar temperature conditions, were compared with the predictions of the model to assess its sensitivity to small changes in the fed mixture composition.Modeling results predicted reasonably well the gas- and the particle-phase concentrations. Overall, the effect of small amounts of toluene on the sooting yield and structure of the methane flame strongly tending toward the sooting structure typical of aromatic fuels, was observed. Experimental evidences and modeling results suggest that the relative importance of soot inception and surface growth by C2H2 and PAH onto existing particles or aggregates is significantly affected by toluene addition.

Effect of Fe2O3 nanoparticles on combustion of coal surrogate (Anisole): Enhanced ignition and formation of persistent free radicals

This contribution explores the effect of nanoparticles of iron (III) oxide (Fe2O3) on the combustion of coal surrogate, i.e., anisole, identifying the changes in ignition features as well as the occurrence of persistent organic pollutants in the initiation channels. The method applies packed-bed reactor coupled with Fourier transform infrared (FTIR) spectroscopy to quantitate the ignition temperature under typical fuel-rich conditions, in-situ electron paramagnetic resonance (EPR) to elucidate the formation of environmentally-persistent free radicals (EPFR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to monitor the chemisorption of organic substrates on the nanoparticles, as well as X-ray diffraction for particles characterisation (PXRD). We employ cluster-based quantum mechanical calculation to map the reaction pathway within the scope of the density functional theory. The results of Fe2O3-mediated combustion of anisole depict an excessive reduction in ignition temperature from 500 °C around 220 °C at λ = 0.8. As confirmed both from EPR and DRIFTS measurements, the chemisorption of anisole on α-Fe2O3 surfaces follows the direct dissociation of the O–CH3 (and OCH2–H), leading to the formation of surface-bound phenoxy radicals at temperatures as low as 25 °C and incurring an estimated energy barrier of Ea = 18 kJ mol−1 and a preexponential factor of A = 2.7 × 1012 M−1 s−1. This insight applies to free-radical chain reactions that induce spontaneous fires of coal, as coal comprises ferric oxide nanoparticles, and equally to coexistence of aromatic fuels with thermodynamically reactive Fe2O3 surface, e.g., in fly ash, at the cooled-down tail of combustion stacks.

Developing detailed chemical kinetic mechanisms for fuel combustion

This paper discusses a brief history of chemical kinetic modeling, with some emphasis on the development of chemical kinetic mechanisms describing fuel oxidation. At high temperatures, the important reactions tend to be those associated with the H2/O2 and C1–C2 sub-mechanisms, particularly for non-aromatic fuels. At low temperatures, and for aromatic fuels, the reactions that dominate and control the reaction kinetics are those associated with the parent fuel and its daughter radicals. Strategies used to develop and optimize chemical kinetic mechanisms are discussed and some reference is made to lumped and reduced mechanisms. The importance of accurate thermodynamic parameters for the species involved is also highlighted, as is the little-studied importance of collider efficiencies of different third bodies involved in pressure-dependent reactions.

Surface pre-ignition measurements of fuel components and their mixtures

A closed loop temperature controlled glow-plug has been used to control the incidence of surface pre-ignition of n-pentane, iso-pentane, n-heptane, iso-octane, ethanol, cyclohexane, ethyl-benzene, toluene and xylene, and four representative mixtures of these components. Statistical data on the incidence of pre-ignition compared with spark ignition has been derived from the in-cylinder maximum pressure, and the glow-plug temperature has been characterised on a cycle-by-cycle basis.The alkanes and alcohols were found to be rather susceptible to surface pre-ignition, with the straight chained molecules having a higher pre-ignition tendency than branched chain molecules. The pre-ignition tendency of ring-structured components depends on the length of the attached chain, with shorter side-chain molecules (xylene, toluene) being less susceptible to pre-ignition than longer side-chain molecules like ethyl-benzene; cyclohexane was more susceptible to pre-ignition than any of the aromatic fuels. A higher glow-plug temperature was found to be needed for pre-igniting stoichiometric or rich mixtures, and this was attributed to the weaker mixture having a higher compression index and a lower specific heat capacity.

Catalytic co-liquefaction of lignin and lignite coal for aromatic liquid fuels and chemicals in mixed solvent of ethanol-water in the presence of a hematite ore

In this work, a raw hematite ore (Fe2O3) displayed to be a low-cost but effective catalyst for co-liquefaction of hydrolysis lignin (HL) and Xilinguole lignite (XL) in ethanol-water (50:50, v/v) mixed solvent under initial N2 atmosphere to produce heavy oil (HO) as a potential source of liquid fuel and aromatic chemicals. The liquefaction of HL and XL separately without catalyst resulted in a maximum of approx. 18 and 11 wt% yield of HO, respectively, while the co-liquefaction process resulted in up to approx. 26 wt% of HO, indicating synergy effect in co-liquefaction of lignin and lignite. The addition of the hematite ore in the co-liquefaction operation produced HO at a very high yield of about 40 wt% at 400 °C for a residence time of 2 h, nearly doubling that of the operation without catalyst. The Produced HO products from the co-liquefaction operations at 400 °C for2 h contain significant concentrations of low molecular weight aromatics at ∼14 mg/g-HO in the presence of non-reduced hematite or goethite, and ∼17 mg/g-HO in the presence of reduced hematite or goethite, compared with only <5 mg/g-HO without iron ore catalyst.

Effect of aromatic fuels and premixing on aromatic species and soot distributions in laminar, co-flow flames at atmospheric pressure

The aim of the present study is to investigate the effects of aromatic fuel structure on the aromatic species and the soot volume fraction in laminar, co-flow flames at atmospheric pressure. Both non-premixed and partially-premixed flames (jet equivalence ratios of 24 and 6) are studied. The four fuels consist of binary mixtures of n-dodecane with one of four aromatic species: n-propylbenzene, toluene, m-xylene, and 1,3,5-trimethylbenzene. For all flame conditions, the total carbon flow rate of the fuel mixture is kept constant. Furthermore, in each binary mixture, the carbon mole fraction from the n-dodecane and the aromatic component is kept constant. Laser-induced incandescence (LII) and laser extinction are used to obtain two-dimensional soot volume fraction in the flames. Laser-induced fluorescence (LIF) is used to obtain the two-dimensional aromatic species distribution in the flames. The experimental results indicate that the 1,3,5-trimethylbenzene/n-dodecane flame has the highest peak soot volume fraction amongst the four fuels; the other three fuel mixtures, within measurement uncertainty, have similar peak soot volume fraction. In addition, premixing changes the spatial distribution of polycyclic aromatic hydrocarbons and soot in the flames. In the non-premixed cases, the peak soot volume fraction is located in an annular region near the flame sheet, whereas the soot field is more uniform across the cross-section of the flame at a jet equivalence ratio of 6. A published aromatic fuel chemical mechanism is used to understand the differences in the pathways to soot precursors among the aromatic fuels. The combined 2D LIF and LII result provide a unique dataset to validate soot and chemical numerical models for the four aromatic fuels: n-propylbenzene, toluene, m-xylene, and 1,3,5-trimethylbenzene.

A wide-range experimental and modeling study of oxidation and combustion of n-propylbenzene

The oxidation of n-propylbenzene (NPB) was studied in a jet-stirred reactor (JSR) equipped with online GC and GC–MS for temperatures ranging between 700 and 1100 K, at φ = 0.4–2.0. In addition, laminar flame speeds were measured at p = 1, 3 and 6 bar at a preheat temperature of T = 473 K, and ignition delay times in a shock tube device behind reflected shock waves, for stoichiometric mixtures at around p = 16 bar. Mole fraction profiles of 25 intermediates including six species, namely 1-propenylbenzene, 2-propenylbenzene, α-methylstyrene, naphthalene, indene, and benzofuran were observed additionally. With φ increasing, NPB consumption shifts to higher temperatures, and the reaction temperature zone becomes broader. Based on the experimental measurements and on new calculations of the rate constants for the H-abstractions from NPB with OH, an updated kinetic model involving 292 species and 1919 reactions was developed with a reasonable agreement with the measured species profiles, flame speed values, and ignition delay times. Rate of production analysis reveals that NPB consumption is generally governed by CH bond cleavage to form three A1C3H6 radicals, which mostly transform to styrene under rich condition and to benzaldehyde under lean condition. Compared to the aromatics formed in the oxidation of two other aromatic C9 fuels, 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene, NPB exhibits to be the most reactive fuel with the least aldehyde intermediates. Moreover, the present model gives a reasonable agreement with the literature-reported ignition delay times and JSR data. These results can improve the understanding of the oxidation and combustion of NPB as a surrogate fuel constituent for kerosene and diesel.

Experimental and kinetic modeling investigation of rich premixed toluene flames doped with n-butanol.

n-Butanol is a promising renewable biofuel and has a lot of advantages as a gasoline additive compared with ethanol. Though the combustion of pure n-butanol has been extensively investigated, the chemical structures of large hydrocarbons doped with n-butanol, especially for aromatic fuels, are still insufficiently understood. In this work, rich premixed toluene/n-butanol/oxygen/argon flames were investigated at 30 Torr with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The blending ratio of n-butanol was varied from 0 to 50%, while the equivalence ratio was maintained at a quite rich value (1.75) for the purpose of studying the influence of n-butanol on the aromatic growth process. Flame species including radicals, reactive molecules, isomers and polycyclic aromatic hydrocarbons (PAHs) were identified and their mole fraction profiles were measured. A kinetic model of toluene/n-butanol combustion was developed from our recently reported toluene and n-butanol models. It is observed that the production of most toluene decomposition products and larger aromatics was suppressed as the blending ratio of n-butanol increases. Meanwhile, the addition of n-butanol generally enhanced the formation of most observed C2-C4 hydrocarbons and C1-C4 oxygenated species. The rate of production (ROP) analysis and experimental observations both indicate that the interaction between toluene and n-butanol in their decomposition processes mainly occurs at the formation of small intermediates, e.g. acetylene and methyl. In particular, the interaction between toluene and n-butanol in methyl formation influences the formation of large monocyclic aromatics such as ethylbenzene, styrene and phenylacetylene, making their maximum mole fractions decay slowly upon increasing the blending ratio of n-butanol compared with toluene and benzyl. The increase of the blending ratio of n-butanol reduces the formation of key PAH precursors such as benzyl, fulvenallenyl, benzene, phenyl and propargyl, which leads to a remarkable reduction in the formation of PAHs.

The impact of subsidized low aromatic fuel (LAF) on petrol (gasoline) sniffing in remote Australian indigenous communities

BackgroundSince 2005, the Australian Government has subsidized the production and distribution of Low Aromatic Fuel (LAF) as a deterrent against petrol (gasoline) sniffing in remote Indigenous communities. LAF is used in place of unleaded petrol as a fuel for vehicles and other engines. This paper reports findings from an independent evaluation of the LAF rollout.MethodsForty one Indigenous communities were surveyed between 2010 and 2014, with each community being visited twice at a two yearly interval. Quantitative data on prevalence of petrol sniffing were collected, as well as qualitative data on the acceptability of LAF, evidence of substitution for inhaled petrol with other drugs, and programs such as recreational, training and employment opportunities. Prevalence rates of sniffing per 1000 population for each survey year and community were calculated by dividing the total number of sniffers by the population aged 5–39 years and multiplying by 1000.ResultsBetween 2011–12 and 2013–14, the total estimated number of people sniffing petrol declined from 289 to 204, a fall of 29.4%. At both times, the median petrol sniffing prevalence rate was lower in communities with LAF than in communities without LAF. In 17 of the 41 communities, comparable data were available over a longer period, commencing in 2005–06. Fifteen of these communities stocked LAF over the entire period. In these communities, the median rate of petrol sniffing declined by 96%, from 141.6 per 1000 population in 2005–06 to 5.5 in 2013–14 (p < 0.05). LAF was widely accepted, although acceptance was often qualified by a belief that LAF harmed engines. Anecdotal reports suggest that the fall in petrol sniffing may have been offset by increased use of cannabis and other drugs, but the relationship is not one of simple cause-and-effect, with evidence that an increase in cannabis use in communities commenced before the LAF rollout began. Provision of services in communities has improved in recent years, but many programs continue to be inadequately resourced.ConclusionsThe rollout of LAF appears to have contributed to reducing petrol sniffing and associated harms in Australian Indigenous communities.