Formation of polycyclic aromatic hydrocarbons, benzofuran, and dibenzofuran in fuel-rich oxidation of toluene using a flow reactor

Recently, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) have been attracting considerable attention owing to their high toxicity. Understanding their formation mechanism during combustion processes is important to control their emission. However, there are few studies that have quantitatively investigated OPAH formation in the fuel-rich oxidation of hydrocarbons, despite the availability of several studies on PAH formation. In this study, benzofuran and dibenzofuran as OPAHs were quantified in the fuel-rich oxidation of toluene using a flow reactor at atmospheric pressure in a temperature range of 1050-1350 K at equivalence ratios from 3.0 to 12.0 and residence times from 0.2 to 1.5 s. In addition to benzofuran and dibenzofuran, 4 types of monocyclic aromatic hydrocarbons and 19 types of PAHs were also evaluated. The experimental data obtained in this study were compared with those of the ethylene oxidation performed in our previous study. The existing kinetic model for PAH growth was modified based on several theoretical studies to predict the behavior of OPAHs with furan structures. The modified model showed significant improvements in the prediction of benzofuran and dibenzofuran formation. Based on the rate of production and sensitivity analysis using the modified model, the dominant reaction pathways of benzofuran and dibenzofuran were investigated.

Driving proton transfer reactions in the 2-methylfuran ring with external forces

In this paper we investigate the proton transfer reactions in 2-methylfuran.

Isomerization and Decomposition of 2-Methylfuran with External Forces

The primary goal of this project was to evaluate the performance of the Standard and Enforced Geometry Optimization (SEGO) method which we have recently developed. The SEGO method has been designed for an automatic location of multiple minima on the molecular Potential Energy Surface (PES), and its usefulness has been demonstrated so far for three molecules only. In this project we applied the SEGO method to explore the 2-methylfuran (2MF) PES. Our choice was not accidental: this molecule recently gained a great deal of interest as a potential candidate for biofuel, and therefore its pyrolysis is extensively studied. To understand pyrolysis of 2MF a detailed knowledge about its PES is needed. In these studies we explored the 2MF PES and located a surprisingly large number of local minima corresponding to 2MF isomers and decomposition products. Some of the 2MF isomers and fragments have amazing structures which most likely were previously unknown. All structures presented in this paper were found in an automatic manner as a result of the enforced chemical reactions driven by the SEGO method. Thus, in these studies we have not only proven that the SEGO method is a very efficient tool for exploring molecular potential energy surfaces, but we also obtained very detailed knowledge about the 2MF PES.

Shock Tube Laser Schlieren Study of the Pyrolysis of Isopropyl Nitrate

The decomposition of isopropyl nitrate was measured behind incident shock waves using laser schlieren densitometry in a diaphragmless shock tube. Experiments were conducted over the temperature range of 700-1000 K and at pressures of 71, 126, and 240 Torr. Electronic structure theory and RRKM Master Equation methods were used to predict the decomposition kinetics. RRKM/ME parameters were optimized against the experimental data to provide an accurate prediction over a broader range of conditions. The initial decomposition i-C₃H₇ONO₂ ⇌ i-C₃H₇O + NO₂ has a high-pressure limit rate coefficient of 5.70 × 10²²T^-1.80 exp[-21287.5/T] s^-1. A new chemical kinetic mechanism was developed to model the chemistry after the initial dissociation. A new shock tube module was developed for Cantera, which allows for arbitrarily large mechanisms in the simulation of laser schlieren experiments. The present work is in good agreement with previous experimental studies.

A new era for combustion research

Current topics in combustion chemistry include aspects of a changing fuel spectrum with a focus on reducing emissions and increasing efficiency. This article is intended to provide an overview of selected recent work in combustion chemistry, especially addressing reaction pathways from fuel decomposition to emissions. The role of the molecular fuel structure will be emphasized for the formation of certain regulated and unregulated species from individual fuels and their mixtures, exemplarily including fuel compounds such as alkanes, alkenes, ethers, alcohols, ketones, esters, and furan derivatives. Depending on the combustion conditions, different temperature regimes are important and can lead to different reaction classes. Laboratory reactors and flames are prime sources and targets from which such detailed chemical information can be obtained and verified with a number of advanced diagnostic techniques, often supported by theoretical work and simulation with combustion models developed to transfer relevant details of chemical mechanisms into practical applications. Regarding the need for cleaner combustion processes, some related background and perspectives will be provided regarding the context for future chemistry research in combustion energy science.

Mechanistic investigation of CO generation by pyrolysis of furan and its main derivatives

A large amount of furan and its derivatives are contained in the biomass pyrolysis products, which mainly lead to the formation of combustible CO with an increase in the pyrolysis temperature; in this study, to illuminate the reaction mechanisms involved in the evolution of CO during the pyrolysis of furan and its main derivatives, quantum chemical theory has been adopted with the GGA-RPBE method, and nine possible reaction pathways have been investigated for the pyrolysis of furan, furfural (FF), furfuryl alcohol (FA) and 5-hydroxymethylfurfural (5-HMF) to generate CO. According to the calculation results, the optimal path for the pyrolysis of furan and its main derivatives to generate CO is as follows: at first, a ring opening reaction of furan occurs to form an aldehyde group, and then, decarbonylation occurs to form CO. Furthermore, the side chain functional groups on the furan ring can promote the ring opening reaction of the furan ring. In addition, the reaction energy barriers of the rate-determining step for the pyrolysis of furan, furfural, furfuryl alcohol and 5-hydroxymethylfurfural (5-HMF) to form CO have been determined as 343 kJ mol⁻¹, 330 kJ mol⁻¹, 317 kJ mol⁻¹ and 363 kJ mol⁻¹, respectively.

Quantum chemical theory has been used to study the furan and its derivatives pyrolysis reaction, nine possible reaction pathways has been studied. Results show that decarbonylation of CO after ring opening is easier than direct decarbonylation.