Mikhail Vlaskin

Hydrothermal liquefaction of microalgae to produce biofuels: state of the art and future prospects

The article presents a review of the state of the art and lines of research on hydrothermal liquefaction (HTL) of microalgae (MA). The main advantages of this technology for production of biofuel are that it does not require predrying of the feedstock and ensures a relatively high product yield—the ratio of the end product weight to the feedstock weight—owing to the fact that all the microalgal components, viz., lipids, proteins, and carbohydrates, are converted into biofuel. MA hydrothermal liquefaction is considered to be a promising technology for conversion of biomass and is a subject of a series of research studies and, judging by the available publications, the scope of research in this field is expanding currently. However, many significant problems remain unsolved. In particular, an active searched is being conducted for suitable strains that will ensure not only a high lipid yield—necessary to convert microalgae into biodiesel—but also higher biomass productivity and a higher biofuel yield; the chemical reactions that occur during the hydrothermal treatment are being studied; and the effect of significant process variables, such as temperature, heating rate, holdup time at the maximum temperature, biomass concentration in the water suspension, biochemical and elemental compositions of the microalgae, use of catalysts, etc., on the liquefaction processes is being studied. One of the urgent tasks is also the reduction of the nitrogen content in the resulting biofuel. Studies aimed at the development of a continuous process and rational heat-processing plants for thermal microalgal conversion are being conducted to increase the energy efficiency of the HTL process, in particular, to provide the heat recovery and separation of the end product.

The investigation of the bio-oil produced by hydrothermal liquefaction of Spirulina platensis using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry

We report the investigation of the hydrothermal liquefaction products of the Spirulina platensis microalgae by using the Fourier transform ion cyclotron resonance mass spectrometry. The hydrothermal liquefaction produced two fractions: one with boiling temperature below 300℃ and the dense residue that remained in the reactor. It was observed that N2 and N classes of compounds that dominate in the positive ESI Fourier transform ion cyclotron resonance spectra for both fractions, and that the light fraction is considerably more saturated then the heavy one. The performed hydrogen/deuterium exchange reaction indicated the presence of the onium compounds in the bio-oil.

Investigation of bio-oil produced by hydrothermal liquefaction of food waste using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry:

Recent research has revealed that more than 1.3 billion tons of food is wasted globally every year. The disposal of such huge biomass has become a challenge. In the present paper, we report the production of the bio-oil by hydrothermal liquefaction of three classes of food waste: meat, cheese and fruits. The highest yield of the bio-oil was observed for meat (∼60%) and cheese (∼75%), while for fruits, it was considerably low (∼10%). The molecular composition of the obtained bio-oil was investigated using ultrahigh resolution Fourier Transform Ion Cyclotron Resonance mass spectrometry and was found to be similar to that obtained from algae. Several thousand heteroatom compounds (N, N2, ON2, etc. classes) were reliably identified from each sample. It was found that bio-oils produced from meat and cheese have many compounds (∼90%) with common molecular formulas, while bio-oil produced from fruits differs considerably (∼30% of compounds are unique).

Investigation of the ozonation products of natural complex mixtures using Fourier transform ion cyclotron resonance mass spectrometry

Natural complex mixtures such as oil and dissolved organic matter play an important role in the economy and in the global carbon cycle. One of the most promising approaches for the investigation of the chemical structure of such substances is the combination of the high-resolution mass spectrometry and selective chemical reactions. Here, we report the investigation of the ozonation products of natural complex mixtures using Fourier transform ion cyclotron resonance mass spectrometry. Ozonation of crude oil results in the appearance of the new compounds with high content (up to 9 atom) of oxygen. Isotopic exchange reaction showed that those oxygen stem from the carbonyl groups. Ozonation of the dissolved organic matter leads to the destruction of the substance and shift towards the region of the saturated compounds.

The combined system for fuel supply of fuel cells on the basis of the aluminum-water hydrogen generator and the metal hybride hydrogen storage

The system for fuel supply of a hydrogen-air fuel cell on the basis of the aluminum-water hydrogen generator and hydride-forming alloy as an intermediate gas storage has been developed. For a series of general composition alloys LaNi4.5 − xAlxCO0.5 service life evaluation tests with the use of highly wet hydrogen were carried out. The possibility of absorption and release of hydrogen by hydride-forming alloys with the rate that corresponds to technical parameters of the system has been shown, and it was found that hydrogen storage capacity is unaffected by high wetness of hydrogen.

Municipal solid waste as an alternative energy source

One of the main objectives in the field of waste management today is the implementation of waste-to-energy concept, because it decreases the amount of municipal solid waste landfilled and economizes the traditional hydrocarbon fuels. One of the main objectives of this study was to assess the global energetic potential of municipal solid waste and its potential contribution in energy balance. This evaluation was based on the analysis of main municipal solid waste properties such as component and chemical compositions, and heating value. The comparison of municipal solid waste properties and energetic potential with those for traditional solid fuels was also discussed. For comparison, the biomass samples and coals collected from Russian coal basins were considered. Study of municipal solid waste properties showed that municipal solid waste represents a well-flammable fuel with high carbon content (up to 50–60% for dry ash-free basis), and relatively high O/C atomic ratio. Total world energetic potential of municipal solid waste was estimated as 20 billion GJ that is 12.6% from energetic potential of coal mined. It was shown that by municipal solid waste incineration it is possible to produce 800 billion kWh of electrical energy that is about 3.5% of total world electricity generation. It was shown that in 2035 energetic potential of municipal solid waste may share up to 21.7% from energetic potential of coal. Executed estimations confirmed the urgency of municipal solid waste waste-to-energy implementation.

Chemical and fractional composition of bio-oil obtained from Arthrospira platensis by hydrothermal liquefaction

This work is devoted to the study of chemical and fractional composition of the bio-oil obtained from Arthrospira platensis by hydrothermal liquefaction in the temperature range of 240-330 °C. For bio-oil analysis standard elemental analysis, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT ICR MS) and thermogravimetric analysis were used. It was shown that the yield of bio-oil was increased from 12.4% at 240 °C to 37.2% at 330 °C. With temperature increasing the spectrum of compounds found in bio-oil using FT ICR MS narrowes and moves to the region of low-molecular compounds. It was found that among the components containing nitrogen and oxygen, compounds containing 1 and 2 nitrogen atoms, as well as ON and O2N3 classes, dominate in the bio-oil. With the increase in the temperature of the liquefaction process, classes of compounds containing several oxygen atoms ON, O2N3, O3N2, ON2, transforms into the classes N and N2. By thermogravimetric analysis it was shown that the gasoline fraction (with boiling temperatures up to 200 °C) in bio-oil samples obtained from Arthrospira platensis at 240-330 °C was in the range of 20-22%. The fraction of light-boiling components in bio-oil was slightly decreased when the temperature of hydrothermal process was increased.

Influence of solvent on the yield and chemical composition of liquid products of hydrothermal liquefaction of Arthrospira platensis as revealed by Fourier transform ion cyclotron resonance mass spectrometry

Yields of liquid products (bio-oil and residual organics in aqueous solution) of hydrothermal liquefaction (at 300℃ and 60 min) of own cultivated Arthrospira platensis using different solvents have been determined. Nonpolar hexane, moderately polar dichloromethane, and relatively more polar acetonitrile have been used. High-resolution mass spectrometry based on linear quadrupole ion trap and Fourier transform mass spectrometer (LTQ FT) has been used for liquid sample characterization. Concentration of bio-oil in a unit of solvent volume after solvent extraction took the following arrangement: acetonitrile > dichloromethane > hexane. Concentration of residual organics in a unit of aqueous solution after solvent extraction took the following arrangement: hexane >dichloromethane > acetonitrile. Yield of total organics was arranged as follows: hexane > dichloromethane > acetonitrile. Content of carbon in bio-oil was increased and the content of oxygen was decreased with the increasing of solvent polarity. From mass spectrometric analysis it was established that in the positive electrospray ionization (ESI) mode the compounds containing two nitrogen atoms dominate and the considerable portion of the compounds containing single nitrogen atom are also presented for both bio-oil and residual organics samples. In the negative ESI mode the compounds containing four oxygen atoms dominated except bio-oil obtained using hexane where the compounds containing two oxygen atoms dominated. Bio-oil fraction had highly saturated compounds with low double bond equivalent values while the compounds of the residual organics fraction had large double bond equivalent values.

Hydrothermal liquefaction of microalgae after different pre-treatments

Hydrothermal liquefaction of different microalgae samples (Arthrospira platensis cultivated by our research group) – fresh (directly after harvesting), dried and frozen – have been performed. In hydrothermal liquefaction process, the samples were heated up to 300°C for 30 min and kept at a constant temperature for 60 min. Then dichloromethane was added to the samples to extract the oil fraction. The products obtained after aqueous and dichloromethane solutions evaporation are referred to as water soluble organics and bio-oil correspondingly. The experiments on hydrothermal liquefaction of microalgae pre-treated in different ways were conducted for three independent harvest samples. The average values of bio-oil yield in the experiments with fresh, dried and frozen microalgae were equal to 44.07%, 39.97% and 39.65%, respectively. The average yields of water soluble organics were equal to 19.34%, 29.00% and 21.43% respectively. In all the experiments, the highest yield of bio-oil was reached for fresh microalgae. From this point of view, direct hydrothermal liquefaction processing of fresh microalgae seems to be more preferable that further enhances the advantage of hydrothermal liquefaction in comparison with other biomass-to-biofuel conversion methods.

Microprobe for the Thermal Analysis of Crude Oil Coupled to Photoionization Fourier Transform Mass Spectrometry

We present the simple microprobe for the investigation of crude oil by a thermal desorption photoionization coupled to Orbitrap mass spectrometry. The droplet of crude oil was placed on the heating element with controllable temperature. The temperature was linearly increased, and crude oil vapors were ionized by a vacuum ultraviolet (VUV) lamp and detected by Orbitrap mass spectrometer. Use of modified Orbitrap allowed introduction of the heating element and VUV lamp directly into the ion funnel and performing experiment not only at atmosphere pressure but also at 20, 10, and 5 torr. We observed that at high pressure protonated CHN compounds dominate in the spectrum, while at the low pressure CH compounds dominate. Similar to previously reported thermogravimetry coupled to photoionization or chemical ionization mass spectrometry systems we were able to separate compounds with different desorption energy and reliably detect low-abundant compounds. Also, we were able to determine the desorption temperature for each compound of the crude oil. We found that temperature of desorption increases linearly with m/ z for compounds that belong to the same homology series (same Kendrick mass defect). This may serve as indirect evidence that such compounds differ only by the length of aliphatic chains attached to some basic structure.