Martin Staš
@vscht.cz
Department of Petroleum Technology and Alternative Fuels
University of Chemistry and Technology Prague
Scopus Publications
Scopus Publications
Lukáš Matějovský, Martin Staš, Luděk Jelínek, Marie Kudrnová, Petr Baroš, Alena Michalcová, Olga Pleyer, and Jan Macák
Elsevier BV
Petr Baroš, Lukáš Matějovský, Martin Staš, Jan Macák, Jan Vysloužil, and Milan Pospíšil
American Chemical Society (ACS)
Petr Baroš, Lukáš Matějovský, Jan Macák, Martin Staš, and Milan Pospíšil
American Chemical Society (ACS)
Martin Staš, Jiří Kroufek, Tomáš Hlinčík, and Pavel Šimáček
University of Chemistry and Technology - Faculty of Environmental Technology
The importance of alternative energy sources is constantly growing, especially due to the ever-increasing energy consumption of mankind and due to the effort to replace existing sources with more environmentally friendly ones. This article is another in a series of articles focused on an overview of technical requirements and testing methods for alternative gaseous, liquid, and solid fuels. This series of articles aims to provide an overview of the required properties of individual alternative fuels, the possibilities of their analysis, and the significance of individual analyzes. This article provides an overview of the technical requirements prescribed by legislation and relevant standards for automotive fuels based on natural gas (fossil methane) and biomethane. Furthermore, prescribed analytical tests are presented, which have been used to monitor the quality of these fuels. To a lesser extent, the importance of selected analytical tests is also discussed. Natural gas can be compressed or liquefied for use in automobile transport. In the first case, CNG fuel is obtained, and in the second, LNG. As a source of renewable methane or biomethane, biogas can be used, which is produced by anaerobic fermentation of agricultural waste or other raw materials in biogas plants. The obtained biogas can be used for the combined production of heat and energy. Alternatively, it can be purified into biomethane, which can be injected into the natural gas distribution network or used in automobile transport in the form of bio-CNG and bio-LNG. In general, it can be stated that the analysis of fuels based on natural gas and biomethane is well managed. Instrumental equipment and analytical methods used for natural gas analysis can be used to analyze these fuels. The properties of fuels based on natural gas and biomethane are closely related to their composition. In terms of proper operation and performance of the combustion engine, the lower heating value, Wobbe number, and methane number are critical parameters. An important parameter is also the sulfane content, increased content of which can lead to corrosion of engine components. In terms of emissions, the total sulfur content is an important parameter also. Sulfur compounds are undesirable in emissions for environmental reasons. At the same time, they are also catalytic poisons. Other critical parameters of fuels based on natural gas and bio-methane are the water content or dew point of water.
Martin Staš, Zlata Mužíková, and Pavel Šimáček
University of Chemistry and Technology - Faculty of Environmental Technology
The importance of alternative fuels is constantly growing due to environmental reasons, saving fossil fuels and reducing the dependence of the world countries on the supply of fossil raw materials from politically unstable regions. This article is further in a series of review articles focused on an overview of technical requirements and testing methods for selected alternative fuels. It is also the first in a series of papers focused on liquid alternative fuels. The aim of this series of articles is to provide an overview of the required properties of individual alternative fuels, the possibilities of their analysis and the importance of the individual analyzes. This article focuses on fuels containing fatty acid esters.Biodiesel can be burned in diesel engines either in a mixture with conventional diesel or as an individual fuel. Unlike conventional diesel, which is composed of hydrocarbons of petroleum origin, biodiesel contains fatty acid methyl esters. In addition to this main component, glycerol (by-product of transesterification), methanol, free fatty acids, glycerides (mono-, di- and tri-), catalyst residues, water, and possibly other components can be present also. These contaminants can, in certain concentrations, cause some undesirable properties both in pure biodiesel and in biodiesel/diesel blends. Compared to conventional diesel, biodiesel has a higher density and viscosity, but a slightly lower higher heating value, and considerably worse oxidation stability. In terms of pollutant emissions, the combustion of biodiesel produces less hydrocarbons, carbon monoxide and solid particles, but slightly more nitrogen oxides than the combustion of mineral diesel. Gas chromatography, infrared spectroscopy, titration methods, and atomic spectroscopy methods have typically been used for the evaluation of these fuels. In addition to the properties monitored by these methods, conventional fuel parameters such as density, viscosity, low-temperature properties, oxidation stability, corrosion properties, flash point, cetane number, and others are monitored for biodiesel and biodiesel/diesel blends. In general, it can be stated that the analysis of fuels containing biodiesel is well managed. Instrumental equipment and (modified) analytical methods used for the analysis of conventional liquid fuels can be used to analyze these fuels.
Martin Staš, Jiří Kroufek, Tomáš Hlinčík, and Pavel Šimáček
University of Chemistry and Technology - Faculty of Environmental Technology
The importance of alternative fuels has increased significantly and continues to grow due to gradually lowering fossil fuel sources as well as environmental reasons. This article is the first in a series of articles focused on gaseous, liquid, and solid alternative fuels. The aim of the articles is to provide an overview of the required properties and testing methods for individual alternative fuels prescribed by the relevant standards. This first article in the forthcoming series focuses on gaseous alternative fuels based on hydrogen and liquefied petroleum gases.
Lukáš Matějovský, Petr Baroš, Martin Staš, Milan Pospíšil, and Jan Macák
American Chemical Society (ACS)
Josef Blažek, Daria Toullis, Petr Straka, Martin Staš, and Pavel Šimáček
MDPI AG
This study describes the co-hydrotreating of mixtures of rapeseed oil (0–20 wt%) with a petroleum feedstock consisting of 90 wt% of straight run gas oil and 10 wt% of light cycle oil. The hydrotreating was carried out in a laboratory flow reactor using a sulfided NiMo/Al2O3 catalyst at a temperature of 345 °C, the pressure of 4.0 and 8.0 MPa, a weight hourly space velocity of 1.0 h−1 and hydrogen to feedstock ratio of 230 m3∙m−3. All the liquid products met the EU diesel fuel specifications for the sulfur content (<10 mg∙kg−1). The content of aromatics in the products was very low due to the high hydrogenation activity of the catalyst and the total conversion of the rapeseed oil into saturated hydrocarbons. The addition of a depressant did not affect the cold filter plugging point of the products. The larger content of n-C17 than n-C18 alkanes suggested that the hydrodecarboxylation and hydrodecarbonylation reactions were preferred over the hydrodeoxygenation of the rapeseed oil. The hydrogen consumption increased with increasing pressure and the hydrogen consumption for the rapeseed oil conversion was higher when compared to the hydrotreating of the petroleum feedstock.
Lukáš Matějovský, Martin Staš, and Jan Macák
American Chemical Society (ACS)
Ethanol-based E5 and E10 fuels have extensively been used as automotive fuels in gasoline engines. However, especially when contaminated, these fuels can exhibit corrosion effects on some engine construction parts such as mild steel. Thus, the study of mild steel corrosion resistance has become of the utmost importance. Electrochemical methods such as electrochemical impedance spectroscopy (EIS) and polarization characteristics measurements (Tafel scan—TS) were proven to be very valuable in studying the mild steel corrosion behavior in ethanol–gasoline blends (EGBs). However, the use of these methods was, so far, very limited for low-ethanol-content EGBs such as E5 and E10 due to their low conductivity. In this study, we present modified EIS and TS corrosion measurements based on the use of tetrabutylammonium tetrafluoroborate (TBATFB) at 500 mg/L as a supporting electrolyte. This modification led to an increase in the contaminated E5 and E10 fuels’ conductivity, which allowed us to successfully perform the electrochemical corrosion tests. The corrosion current densities were determined to be 1.5 × 10–3 and 1.5 × 10–2 μA/cm2 for the tested E5 and E10 fuels, respectively. These modified methods present a significant extension of an electrochemical testing apparatus for steel corrosion studies in EGBs. They can allow one to obtain instantaneous information about the occurring corrosion process and, thus, estimate the materials’ lifetime in corrosive environments and potentially help to prevent corrosion.
Martin Staš, Miloš Auersvald, and Petr Vozka
American Chemical Society (ACS)
Miloš Auersvald, Martin Staš, and Pavel Šimáček
Elsevier BV
Abstract Bio-oils after hydrotreatment can still contain significant amount of phenols and cyclic olefins as the products of an incomplete deoxygenation. The removal of these compounds would be necessary to produce suitable components for automotive fuels. However, no routine method currently exists for the reliable determination of these groups in hydrotreated bio-oils (HBOs). In this paper, we analyzed 140 different pure oxygenates as model compounds using the bromine number method (ASTM D1159) observing that most compounds present in HBOs react with one equivalent of bromine. The determination of phenols using bromine number method in crude bio-oil is complicated especially by the presence of guaiacols and syringols that react with more than one equivalent of bromine and, thus, the obtained result is significantly overestimated. Further we optimized the chromatographic separation of hydrocarbons from HBOs for the selective determination of olefins content. As no other reactive compounds under the conditions of the method, besides phenols and olefins, were observed in HBOs, the difference between HBO bromine number (before hydrocarbons separation) and olefins content correspond to the total amount of phenols. The method was finally applied to 11 HBOs with different content of oxygen, providing a good correlation between phenols and oxygen content.
Lukáš Matějovský, Martin Staš, Karolina Dumská, Milan Pospíšil, and Jan Macák
Elsevier BV
Abstract Bioethanol is a promising biofuel that can be used in the pure form or in the form of ethanol-gasoline blends (EGBs) as a transportation fuel. The combustion of bioethanol in petrol engines is associated with several problems, with bioethanol corrosion effects on metallic construction engine parts being one of the most serious ones. Electrochemical methods, such as electrochemical impedance spectroscopy, measurement of polarization characteristics (Tafel scan), etc., have been found to be efficient in studying corrosion effects in metal-EGB systems. However, a fuel environment with a low ethanol content (such as E10 and lower) has low conductivity, which can be a limiting factor for electrochemical corrosion studies. Supporting electrolytes can be used to increase the conductivity of such environments. These supporting electrolytes must be inert against the occurring corrosion reactions in order not to negatively affect the obtained corrosion data. In this work, we tested four potential supporting electrolytes (lithium perchlorate, tetrabutylammonium tetrafluoroborate, potassium hexafluorophosphate, and tetrabutylammonium bromide) to be used for the electrochemical corrosion tests on mild steel in the environment of an E85 fuel. In our study, we demonstrated that tetrabutylammonium tetrafluoroborate (TBATFB) can successfully be used for short-term corrosion studies as it exhibited minimum effects on the obtained electrochemical data even at a relatively high concentration of about 500 mg/L. The use of this supporting electrolyte can substantially facilitate electrochemical corrosion studies in less conductive media such as EGBs with a low content of ethanol.
Miloš Auersvald, Tomáš Macek, Tim Schulzke, Martin Staš, and Pavel Šimáček
Elsevier BV
Abstract One of the easiest ways to minimize the overall costs of bio-oil production is to minimize biomass transportation and, thus, pyrolysis should be performed at or close to the biomass original location. Thus, we applied ablative fast pyrolysis (AFP), as the only potentially mobile pyrolysis unit, to convert residual lignocellulosic biomass into bio-oil. Four different biomass types were converted to bio-oils: beech and poplar wood, straw and miscanthus. To study reliably the influence of biomass type on bio-oil yields, physicochemical properties and composition, pyrolysis was carried out at a constant temperature of 550 °C. Titrations and spectroscopic methods were used for the characterization of the main oxygenate groups. GC-MS was used for the quantification of more than 120 volatile compounds. Such a thorough analytical study of AFP bio-oils, heretofore missing in scientific literature, allowed us to reliably discuss the differences in bio-oils´ relative to the knowledge of biomass composition. Significant differences between the bio-oils were observed, with the lowest content of carboxylic and carbonyl groups in the straw bio-oil. The amount of carboxylic and phenolic groups in all the bio-oils was in the typical range observed for bio-oils unlike the carbonyls´ and levoglucosan content, which was lower than typical for bio-oils from other pyrolysis units.
Veronika Váchová, Daria Toullis, Petr Straka, Pavel Šimáček, Martin Staš, Andrej Gdovin, Zdeněk Beňo, and Josef Blažek
American Chemical Society (ACS)
Currently, there is an effort to achieve a more widespread use of biofuels, which are an alternative to conventional, petroleum-based fuels in mobile and stationary applications. The conversion of ...
Martin Staš, Miloš Auersvald, Lukáš Kejla, Dan Vrtiška, Jiří Kroufek, and David Kubička
Elsevier BV
Abstract Pyrolysis bio-oils are liquid products of lignocellulosic biomass pyrolysis. They have a highly promising potential to be widely used, after an appropriate upgrade, as advanced biofuels, or as a source of valuable oxygen-containing chemicals. The chemical composition of bio-oils is very complicated as they contain thousands of different, mostly oxygen-containing, compounds with a wide distribution of physical and chemical properties, and concentrations. Detailed knowledge of the bio-oil composition is crucial in order to optimize the pyrolysis processes and/or the subsequent bio-oil upgrading processes. The main challenge in bio-oil analytics is the identification and quantification of the individual compounds as well as the quantification of the total content of the compounds with the characteristic functional groups. In this review, we will discuss a state-of-the-art quantitative analysis of bio-oils and formulate strategies for obtaining in-depth information on the composition of the bio-oils and/or the products of their upgrading. Thermic, non-catalytic fast pyrolysis bio-oils and their hydrotreated analogues are of interest of this review. The emphasis will be placed on the quantification of the compounds with the key oxygen-containing functional groups present in the bio-oils including aldehydes, ketones, carboxylic acids, phenols, carbohydrates, etc. Also, methods for the quantification of the individual compounds will be presented. Hence, this overview and critical assessment of the quantitative methods can help the researchers to better understand the results obtained by these methods and formulate strategies and goals for further research. In addition, the knowledge presented in this review will serve as a reference to any scientist working with complex mixtures of oxygenates.
Lukáš Matějovský, Jan Macák, and Martin Staš
American Chemical Society (ACS)
Nowadays, there is an effort to increase the more widespread use of biofuels that are a renewable energy source in transportation and an alternative to conventional, petroleum-based fuels. These biofuels include alcohols such as biomethanol, bioethanol, and biobutanol that have a high octane number, but generally different physical and chemical properties than petroleum fuels. The different properties of alcohols may cause low material compatibility with carbon steel. Here, we used cyclic potentiodynamic polarization (CPP) to study the behavior of carbon steel in an environment of alcohols and alcohol–gasoline blends (AGBs). Using CPP, we proved that the corrosion of mild steel can be significantly influenced by alcohol properties, such as the chain length, pKa, and solubility of oxygen and water. In the environment of pure alcohols (not blended by gasoline), a very good passivation ability of steel was proven, especially for n-butanol. In AGBs, steel corrosion can also be influenced by the gasoline amount. When these pure alcohols or their gasoline blends are contaminated by water-containing chlorides and organic acids, the corrosion rate of carbon steel can increase by up to 4 orders of magnitude. In an anhydrous environment of alcohols, the CPP can give results with a very good informative value.
Lukáš Matějovský, Jan Macák, Olga Pleyer, Petr Straka, and Martin Staš
American Chemical Society (ACS)
Ethanol produced from renewable sources (i.e., bioethanol) is a first-generation biofuel that is currently being added as a biocomponent into gasolines. Mixtures of ethanol and gasoline are designated as ethanol–gasoline blends (EGBs). Ethanol has high polarity and moisture affinity, which considerably influence the properties of the resulting EGBs including their aggressiveness to many metallic and nonmetallic materials. The corrosion aggressiveness of EGBs can be minimized by suitable corrosion inhibitors. In this study, we tested three different corrosion inhibitors on mild steel in the environment of aggressive E10, E25, E60, and E85 fuels. The inhibitors tested were diethylene triamine (DETA) and two mixed inhibitors containing propargyl alcohol, dibenzyl sulfoxide, and octadecyl amine. To study the efficiency of the corrosion inhibitors, we used static and dynamic corrosion tests and electrochemical measurements including impedance spectroscopy and potentiodynamic polarization. The highest corrosion aggressiveness on mild steel was observed for the E60 fuel. The highest inhibitory efficiency was, for all the fuels tested, observed for the DETA inhibitor. For the DETA concentration of 100 mg·L–1, the inhibitory efficiency in the E60 fuel was determined to be around 98%.
Miloš Auersvald, Bogdan Shumeiko, Martin Staš, David Kubička, Josef Chudoba, and Pavel Šimáček
American Chemical Society (ACS)
Bio-oil upgrading through its hydrodeoxygenation (HDO) using sulfided catalysts has attracted significant attention because of its potential to provide advanced biofuels. Although many studies have been undertaken, a detailed understanding of the changes in the chemical composition on the molecular level that would allow the better design of catalysts for bio-oil upgrading is still insufficient. Therefore, we have subjected straw bio-oil and products obtained from its hydrotreatment over a broad range of experimental conditions to a detailed quantitative chemical analysis. Most of the volatile compounds were quantified by GC-MS. Among them, 115 compounds were quantified directly (i.e., using the appropriate standards) and more than 100 indirectly (i.e., based on their structural similarity with corresponding standards). Moreover, the total concentrations of carboxylic acids, carbonyls and phenols were quantified by the carboxylic acid number (CAN), Faix, and Folin–Ciocalteu methods, respectively, to obtai...
Miloš Auersvald, Bogdan Shumeiko, Dan Vrtiška, Petr Straka, Martin Staš, Pavel Šimáček, Josef Blažek, and David Kubička
Elsevier BV
Abstract To meet the expected requirements of the proposed EU Renewable Energy Directive for the next decade (RED II), it is necessary to increase the availability of second-generation biofuels. One promising way of doing this involves using ablative fast pyrolysis units to transform an agricultural by-product, for example straw, into bio-oil. To obtain straw bio-oil suitable for processing in a typical refinery, we optimized the key parameters of its hydrotreatment. For the upgrading, a continuous flow reactor with a fixed bed of a commercial sulphide NiMo/Al 2 O 3 catalyst was used. The reaction temperature and pressure were tested at 240–360 °C and 2–8 MPa, respectively. The reaction off-gas was analysed by GC-FID/TCD. A detailed physicochemical analysis of the products was carried out. Under most conditions tested, the product was separated into an aqueous and an organic phase. For the best products, >85% of the feed energy content remained in the organic phase and a significant decrease in viscosity and acidity was achieved. The product prepared at 360 °C and 8 MPa was the only one completely miscible with straight-run gas oil and, thus, appears to be the most suitable for co-processing in a refinery.
Petr Straka, Daniel Maxa, and Martin Staš
Elsevier BV
Abstract The precise chromatographic isolation of saturates is a common problem of the characterization of highly paraffinic petroleum based samples. Incomplete elution of high-molecular-weight saturates (HMWS) or contamination of saturates by aromatics can occur when alumina or silica gel are used to separate highly paraffinic samples. Here, we present a precise, fast and simple method for the quantitative isolation of HMWS from samples of highly paraffinic crude oils, crude oil deposits, high-boiling petroleum distillates, distillation residues and waxes. The method is based on a direct chromatographic elution of HMWS with n-heptane at 80 °C on a column packed with silica gel modified with silver nitrate. The pre-separation of asphaltenes from samples is not necessary. This allowed for a quantitative elution of all present HMWS (up to C100) with no contamination by aromatics. As an example of a practical application to benefit from this efficient hydrocarbon fractionation procedure, is the analysis of crude oils and deposits. A detailed knowledge of the content of high-molecular-weight n-alkanes in these samples can help to prevent problems during crude oil transport and storage.