Biomass is a renewable energy source with great potential. One of the promising ways for the conversion of biomass into more suitable forms of energy is its pyrolysis. Liquid products of the biomass pyrolysispyrolysis oils (or bio-oils) could be used in the future as biofuel or as feedstock for valuable chemicals. Detailed knowledge about their chemical composition is crucial, as it can facilitate the design of processes for the necessary upgrading of bio-oils. This paper outlines current knowledge about the composition of bio-oils and presents an overview of the commonly used analytical methods and procedures for the characterization of the liquid pyrolysis products of biomass. The capabilities and limitations of these methods are discussed as well.

Ethanol–gasoline blends (EGBs) can easily absorb large amounts of water because of the presence of ethanol. Acidic compounds and ions can be dissolved in water, and these substances can have corrosive effects on metallic construction materials. With the increasing content of ethanol in fuels, the conductivity and ability of fuel to absorb water increases, and the resulting fuel is becoming more corrosive. In this work, we tested E10, E40, E60, E85, and E100 fuels that were prepared in the laboratory. These fuels were purposely contaminated with water and trace amounts of ions and acidic substances. The aim of the contamination was to simulate the pollution of fuels, which can arise from the raw materials or from the failure to comply with good manufacturing, storage, and transportation conditions. The corrosion properties of these fuels were tested on steel, copper, aluminum, and brass using electrochemical impedance spectroscopy and Tafel curve analysis. For comparison, static immersion tests on steel were also performed. The main parameters for the comparison of the corrosion effects of the tested fuels were the instantaneous corrosion rate; the polarization resistance; and the corrosion rate, which was obtained from the weight loss occurring during the static tests. In most cases, E60 fuel showed the highest corrosion activity.

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Pyrolysis bio-oils could be used in the future as biofuels or as a source of valuable oxygen-containing chemicals. To facilitate efficient exploitation of bio-oils, a detailed understanding of their structure is necessary. Over the past decade, petroleomic analysis has been widely applied to characterize pyrolysis bio-oils from the lignocellulosic biomass. Typically, a petroleomic analysis has been performed using high-resolution mass spectrometry (HRMS). HRMS has enabled the researchers to determine the molecular weights and molecular formulas of thousands of less volatile and nonvolatile, high-molecular-weight bio-oil compounds to obtain structural information that cannot be obtained using any other method. Here, we discuss the theoretical principles of HRMS and present an overview of the investigations regarding the petroleomic characterization of pyrolysis bio-oils and their key findings. In addition, this review outlines the current knowledge of the structure of bio-oil compounds detectable by HRMS. This could help us to understand the chemical composition of bio-oils in more detail and facilitate the design of processes for bio-oil upgrading and further utilization.

Bioethanol added into gasolines significantly changes the physical and chemical properties of the resulting fuels and can have a considerable influence on their overall thermo-oxidative stability. During fuel oxidation, different oxidation products such as water, acidic substances, and peroxides are formed and these can have corrosive effects on metallic construction materials of the storage and transportation equipment, engines, and fuel lines of automobiles, etc. In this work, we tested the laboratory prepared ethanol−gasoline blends (EGBs) E10, E25, E40, E60, and E85, which were artificially oxidized depending on their induction period. The oxidized fuels were used to study their corrosion aggressiveness after their thermal load in the presence of oxygen or after the expiry of their shelf life. The corrosion properties of these fuels were tested on steel, copper, aluminum, and brass using electrochemical methods such as electrochemical impedance spectroscopy and Tafel curve analysis. For comparison, static immersion tests on copper and brass were performed. The main parameters for the comparison of the corrosive effects were the instantaneous corrosion rate, the polarization resistance, and the corrosion rates of copper and brass, which were obtained from the weight losses which occurred during the static tests. The highest corrosion aggressiveness was observed, in most cases, for the oxidized E60 fuel; in this environment, the lowest resistance was observed for brass, at a peroxide content of 250 mg•kg −1 already.

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This work deals with studying mild steel corrosion resistance in ethanol–gasoline and butanol–gasoline blends (EGBs and BGBs, respectively) with an alcohol content of 10–100 vol %. These fuels were tested in two forms: pure (noncontaminated) and purposely contaminated with water and trace amounts of acids, chlorides, and sulfate ions. Electrochemical methods, such as open circuit potential, electrochemical impedance spectroscopy, and polarization characteristics measurements in three-electrode arrangements were used for the study. A three-month-long static immersion test was performed as a supplementary method. The obtained results showed that the contamination led to an increase in aggressiveness of the tested fuels against the mild steel. This effect was surprisingly more noticeable for the BGBs, in which the corrosion rate increased by up to 3 orders of magnitude compared with their noncontaminated form. For the EGBs with an ethanol content of 60 vol % or more (E60 and higher), an initial quasi-passive state was observed, which was not persistent. Pitting corrosion was observed especially in the E100 fuel and in the fuels containing 40 vol % or more of butanol (B40 and higher). The E10 and B10 fuels showed very low corrosion aggressiveness even after the contamination. In the B10 fuel, the lowest mild steel corrosion rates were measured, which corresponded to the lowest corrosion current densities (3.6 × 10–3 μA cm–2) and the highest polarization resistance (13.7 MΩ cm2).

Pyrolysis bio-oils have great potential for the future use as biofuels and source of oxygenated chemicals. To optimize a pyrolysis process, detailed knowledge about the chemical composition of bio-oils is necessary. In recent years, high-resolution mass spectrometry (HRMS) has successfully been used to the characterization of pyrolysis bio-oils from lignocellulosic biomass. This method enabled to detect thousands of semivolatile and nonvolatile, high-molecular-weight bio-oil compounds and provided partial information about their structure. In this work, we used high-resolution orbitrap mass spectrometry to characterize semivolatile and nonvolatile, high-molecular-weight compounds of four bio-oils obtained from the ablative flash pyrolysis of different biomass sources. Before the analyses of these bio-oils, we analyzed model bio-oil compounds and commercially available bio-oil from fast pyrolysis of wood using positive-ion and negative-ion electrospray (ESI) and positive-ion and negative-ion atmospheric pressure chemical ionization (APCI) orbitrap mass spectrometry and compared the results. Based on this comparison, a combination of negative-ion ESI and APCI was found to be well suited for the characterization of pyrolysis bio-oils; these techniques were thus used for the study of bio-oils from different biomass sources and the obtained results were compared. In the studied bio-oils, mostly compounds with 1–8 oxygen atoms per molecule were detected and their degree of unsaturation (DBE) was about 1–10 (negative-ion ESI) and 1–17 (negative-ion APCI), respectively. Among the studied bio-oils, the differences were observed mostly in abundances of their major compounds (compound classes). The analyses of model bio-oil compounds brought valuable information about their behavior during the HRMS characterization of bio-oils. The presented results could help to improve the understanding of bio-oil composition and HRMS characterization of bio-oils and facilitate their further utilization