Michael Ioelovich | Weizmann Institute of Science (original) (raw)

Papers by Michael Ioelovich

In this study, a thermodynamic analysis of methane synthesis by hydrogenation of carbon dioxide w... more In this study, a thermodynamic analysis of methane synthesis by hydrogenation of carbon dioxide was performed.
Although the standard Gibbs potential of this reaction, known as the Sabatier reaction, is negative, methane synthesis
under standard conditions does not occur due to kinetic limitations. To overcome these kinetic limitations, a significant
increase in temperature and pressure is necessary along with a catalyst additive. Therefore, further thermodynamic
analysis of the Sabatier reaction was carried out for the real conditions of this reaction, temperature Tr = 673.15 K and
pressure Pr = 3 MPa. The calculations showed that under real conditions the Sabatier reaction has exothermic enthalpy
ΔrH = -181 kJ/ mol, and negative Gibbs potential ΔrG = -84 kJ/mol. Thus, methane synthesis reaction from carbon dioxide
and hydrogen at elevated temperature Tr and pressure Pr is energetically and thermodynamically favorable. In addition,
the equilibrium constant of this reaction Keq is 3.24 x 106. This great value of the Keq indicates that under real conditions
the Sabatier reaction is strongly shifted to the methane synthesis

WJARR, 2024

This article provides a review of the research on the chemical thermodynamics and thermochemistry... more This article provides a review of the research on the chemical thermodynamics and thermochemistry of biomass, cellulose, and its derivatives such as ethers, esters, and oxycelluloses. For diverse biomass types, gross and net heating values were studied. It has been established that these energetical characteristics of biomass can be calculated using a superposition of the energetical characteristics of the main components of biomass such as cellulose, hemicelluloses, lignin, lipids, proteins, etc. The pelletization of biomass improves its fuel performance. It was shown that, if the ultimate goal is to generate the maximum amount of thermal energy, then it is more profitable to directly burn the initial biomass in the form of pellets than to burn the amount of solid or liquid biofuel that can be extracted from this biomass. After the cellulose study, the direct and exact thermochemical method for determining the crystallinity degree of this biopolymer was proposed. In addition, the standard combustion and formation enthalpies of various cellulose samples were studied. As a result, the thermodynamic characteristics of four crystalline allomorphs of cellulose, CI, CII, CIII, and CIV, were obtained and their thermodynamic stability was evaluated. The thermochemistry of enzymatic hydrolysis of cellulose was studied. In addition. The thermodynamical characteristics of various cellulose derivatives were determined, and the thermochemistry of the reactions of cellulose alkalization, etherification, esterification, and oxidation was studied.

WJARR, 2024

This research studies the forces acting in an electron pair with antiparallel spins participating... more This research studies the forces acting in an electron pair with antiparallel spins participating in forming a covalent
chemical bond between atoms. The first is the force of electrostatic repulsion of electrons. The second is the
gravitational attraction of these electrons. The third is the force of electromagnetic attraction between the electron pair.
From calculations it follows, that the force of gravitational attraction is negligible, and therefore it is not able to
withstand the force of electrostatic repulsion between electrons. However, the force of electromagnetic attraction
between a pair of electrons with antiparallel spins turned out to be much greater than the force of their electrostatic
repulsion. As a result, the formation of stable electron pairs in molecular orbitals becomes possible. Thus, the valence
electrons of neighboring atoms interact with each other like femto-electromagnets, which leads to the formation of a
strong interelectronic bond and ensures the integrity of the molecule. To form covalent bonds, the force of electrostatic
attraction between the nuclei and paired electrons of the molecular orbitals must exceed the forces of electrostatic
repulsion between both the positively charged nuclei and the negatively charged electrons of the atomic orbitals of
different atoms

Biomass, Jul 8, 2024

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

World Journal Of Advanced Research and Reviews, Apr 30, 2024

World Journal Of Advanced Research and Reviews, Feb 28, 2023

World Journal Of Advanced Research and Reviews, Dec 29, 2023

This paper describes the preparation methods of crystalline and amorphous nanocellulose particles... more This paper describes the preparation methods of crystalline and amorphous nanocellulose particles having specific functional groups used as biocarriers of various therapeutically active substances (TAS). To prepare crystalline nanoparticles chemical grade cellulose is treated with 60 wt. % sulfuric acid (SA) at 45 °C with the following washing and disintegration in aqueous medium. Amorphous nanoparticles are prepared by solution of cellulose in 66 wt. % SA at room temperature with the following precipitation, washing and disintegration in aqueous medium. The obtained nanocarriers contain sulfonic groups, which can attach various basic TAS to use them in biomedicine, cosmetics and personal care.

Альтернативная энергетика и экология, 2013

Academic journal of polymer science, Oct 9, 2018

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Mar 3, 2017

World Journal Of Advanced Research and Reviews, Jun 30, 2023

Известия вузов, Mar 1, 2017

Bioresources, Jul 26, 2009

WJARR, 2024

Biomass, Jul 8, 2024

World Journal Of Advanced Research and Reviews, Apr 30, 2024

World Journal Of Advanced Research and Reviews, Feb 28, 2023

World Journal Of Advanced Research and Reviews, Dec 29, 2023

Альтернативная энергетика и экология, 2013

Academic journal of polymer science, Oct 9, 2018

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Mar 3, 2017

World Journal Of Advanced Research and Reviews, Jun 30, 2023

Известия вузов, Mar 1, 2017

Bioresources, Jul 26, 2009

In this chapter, preparation, characterization and applications of chitin and chitosan have been ... more In this chapter, preparation, characterization and applications of chitin and chitosan have been described and discussed. These nitrogenated polysaccharides occupy second place prevalence in the nature after cellulose. Diverse physical, physicochemical and chemical methods are applied to characterize structure and properties of these biopolymers. Being nanostructured, chitin and chitosan can be isolated from natural sources in a form of nanoscale particles, fibrils and filaments having unique features such as small dimensions, variety shapes, enhanced specific surface, high sorption and absorption ability, and other specific characteristic in combination with biocompatibility, biodegradability and complex of unique therapeutic properties. In addition, these biopolymers serve as a basis for the production of some therapeutically active substances. Therefore, chitin and chitosan find a great commercial interest in biomedicine, pharmaceutics, cosmetics, personal care and some other areas. Small particles and fibrils made of the biopolymers can be used as fillers for biocomposites and thickeners imparting to liquid systems an increased viscosity and gel consistence. The nanocarriers of nitrogenated polysaccharides can bind various therapeutic active substances, which expand application areas of these biopolymers. Antibacterial non-woven materials made of nanofilaments have an increased absorption ability and accelerate healing process. Some other application areas of the nitrogenated polysaccharides are also described

Cellulose is a widespread renewable natural polymer, which is the most appropriate for preparatio... more Cellulose is a widespread renewable natural polymer, which is the most appropriate for preparation of various types of nanomaterials. Being typical nanostructured polymer, cellulose contains nanofibrils, nanocrystallites, paracrystalline nanolayers and amorphous nanodomains, which allow produce various kinds of the nanomaterials: cellulose nanofibrils, cellulose nanocrystals, particles o f amorphous nanocellulose and cellulose nanoyarn. Besides bacterial nanocellulose is a natural source of biosynthesized cellulose nanofibrils. In this chapter, the modern methods of structural investigations of various nanocellulose kinds are described. To characterize the structure of nanocellulose (NC), the main structural characteristics should be determined such as dimensions, shape, aspect ratio, specific surface area, charge, parameters of crystalline structure, purity, DP, etc. Effect of structural characteristics of NC of various kinds on their chemical, physico-chemical and physico-mechanical properties is discussed. Furthermore, specific structural features and properties of the nanocellulose kinds are shown.

Methods, 2022

Cellulose and its derivatives are abundant and the most widespread polymers having of great scien... more Cellulose and its derivatives are abundant and the most widespread polymers having of great scientific and practical importance [1]. The study of the structure and properties of these polymers was carried out for many years by various methods. As a result, it became possible to calculate their various physicochemical properties using correlation equations, knowing several structural parameters, such as the degree of crystallinity (X) and amorphicity (Y), lateral size of crystallites (L), partial volumes of atoms and atom groups, etc.

Sorbents & Sorption Conf., 2021

This calculating method is based on the thermodynamics of binary systems in combination with the ... more This calculating method is based on the thermodynamics of binary systems in combination with the Van Krevelen algorithm of polar group contributions to the sorption of WV. It was shown that the mechanism of WV sorption by various hydrophilic polymers is the absorption of water molecules in the volume of amorphous domains of these polymers. As a result, a universal physicochemical equation was proposed, which makes it possible to adequately describe the sorption isotherms of amorphous hydrophilic polymers knowing only the chemical formulas of repeating units of these polymers. To calculate the sorption isotherms for semicrystalline samples, it is necessary to use an additional parameter, namely the degree of amorphicity (Y). The adequacy of the derived equation was verified for samples of cellulose and other natural polysaccharides, as well as for samples of synthetic hydrophilic polymers having various Y-values. The verification showed that the experimental isotherms are almost identical to the isotherms calculated by the universal equation.

Textile Conf., 2021

In this paper, about twenty varieties of Acala cotton fibers and eighteen varieties of Pima cotto... more In this paper, about twenty varieties of Acala cotton fibers and eighteen varieties of Pima cotton fibers with various features have been selected to spin threads with metric counts (Nm) from 20 to 60. It was shown that if the yarns are made from the same variety of cotton fibers by the same spinning method on the same equipment, then the mechanical properties of the threads are practically independent of the metric counts. Therefore, to find correlations between the features of the cotton fibers Acala and Pima of different varieties, on the one hand, and the mechanical properties of the threads, on the other hand, the yarns with Nm = 40 were used. It was found that knowing such features of cotton fibers as UHM length (X1), fineness (X2), and strength (X3), it is possible to calculate the tensile strength and Young's modulus of the threads with high correlation coefficients if the argument Xo = X1X3/X2 is used. Elongation at the break of the threads also was predicted.

Polymer Conference, 2020

In this research, the dependence of glass transition temperature (Tg) and melting point (Tm) on t... more In this research, the dependence of glass transition temperature (Tg) and melting point (Tm) on the specific cohesive energy was studied for various non-& low polar and polar polymers. It was found that the studied thermo-physical features of polymers correlate much better with the volume cohesive energy (Ev) than with the molar cohesive energy (Em). When using polymers belonging to a certain group, only non-& low polar or only polar, a linear dependence Tg = f(Ev) was obtained with relative small deviation. However, when studying this dependence for all studied polymers of different groups, the linear correlation is highly disturbed. This disturbance can be explained by the fact that the concept of cohesive energy was developed only for non-& low polar polymers. In order to adapt this theory to polar polymers, it is necessary to introduce a special correction to eliminate the contribution associated with polar interactions and hydrogen bonds to the cohesive energy. After calculating the corrected volume cohesive energy (Ev,c) the linear regression equations, Tx = aEv,c + b, with high correlation coefficients were derived for all polymers of different classes, where Tx is Tg or Tm; and a, b are coefficients. The relationship between Tm and Tg was also obtained.

Methods of Polymers Analysis, 2020

In this research, some thermo-physical (glass transition temperature, Tg; melting point, Tm) and ... more In this research, some thermo-physical (glass transition temperature, Tg; melting point, Tm) and mechanical properties (tensile strength, TS; Young’s modulus, Y) of hydrophobic polymers were studied. The linear dependences between these properties and the specific cohesive energy were obtained. It was found that the studied properties of polymer materials correlate much better with the volume cohesive energy (Ev) than with the molar cohesive energy. The linear regression equations, Z = k Ev + C, with high correlation coefficients were calculated, where Z is property, k and C are coefficients. The dependences of various properties of polymers on Tg were also studied. It was shown that the obtained relationships allow to predict some properties of polymer materials with a sufficiently good reliability.

Biomass Conference, 2020

Designer Energy Ltd (DE) developed two improved methods for the quantitative chemical analysis of... more Designer Energy Ltd (DE) developed two improved methods for the quantitative chemical analysis of biomass samples. The fists DE method for determination of chemical composition of biomass is the modified and improved NREL method. The second DE method is based on the isolation of lignin and holocellulose, containing both cellulose and hemicelluloses, from biomass. After acid hydrolysis of holocellulose under mild conditions hemicelluloses were removed, and as a result the content of cellulose can be determined. The content of acid-insoluble lignin was measured by improved method after two-stage acidic hydrolysis of the biomass. In order to prevent loss of the components, a centrifugation technique was used for isolation of final products. The developed methods were used for analysis of chemical composition of crude and pretreated samples of switchgrass and sugarcane bagasse. It has been shown that DE methods provide more reliable results than conventional methods of chemical analysis.

The problem of accumulation and decomposition of solid and liquid wastes is discussed. It is show... more The problem of accumulation and decomposition of solid and liquid wastes is discussed. It is shown that modern incineration technologies of solid waste allow to reduce the amount of landfilled refuses, and also to obtain a significant amount of thermal energy. Liquid waste, such as sewage, is a source to produce the methane, whereas disinfected solid residue can be used for production of compost. An additional source of methane is livestock waste. Combustion of solid wastes and methane allows the generation of additional amounts of heat energy used to generate electricity or heat.

The wide angle X-ray scattering (WAXS) is widely used method to evaluate sizes of cellulose cryst... more The wide angle X-ray scattering (WAXS) is widely used method to evaluate sizes of cellulose crystallites by means of the Scherrer's equation. However, the Scherrer's methodology has a limitation, since a width of X-ray diffraction peaks depends not only on the size of crystallites but also on other factors, such as instrumental effect, second-order distortion degree of crystalline lattice, δ, and factor Δ=4δ tg. The method of measuring the instrumental factor (b) is well known, but δ and Δ factors are ignored that leads to understated sizes of crystallites. In this research a simple procedure was proposed to determine δ and Δ factors, as well as actual sizes of CIβ crystallites. Values of δ were calculated using average deviation of interplanar spacing in the distorted lattice from its value in undistorted crystalline lattice. It was also shown that δ and Δ factors are linear functions of interplanar spacings (d) of crystalline lattice. After finding the δ and Δ factors, the correction for broadening of diffraction peaks was calculated, which allows to determine the actual width (Da) and actual length (La) of crystallites. Study of various samples of CIβ showed that tunicate cellulose has the largest crystallites: Da = 13 nm and La = 400 nm. Actual sizes of crystallites in isolated celluloses of other origin (herbaceous plants, wood, bast fibers, cotton fibers, etc.) were smaller: Da was in the range of 4.2 to 10 nm, whereas La in the range of 48 to 116 nm.

A green technology of plant biomass for isolation of cellulose and production of micro- and nanop... more A green technology of plant biomass for isolation of cellulose and production of micro- and nanoparticles was proposed in this project

Increased content of cellulose, its reduced crystallinity, as well as decreased content of lignin... more Increased content of cellulose, its reduced crystallinity, as well as decreased content of lignin and hemicelluloses in the pretreated biomass, promote enzymatic saccharification. In this paper, the correlation equations between yield of glucose (Y) and chemical composition of biomass, as well as cellulose crystallinity were derived: Y= 1.92 C (1-X) – 0.48 (LHC) + 5 or more preferable Y= 0.98 (C-L) + 0.6; where X is crystallinity degree of cellulose, C is percentage of cellulose, L is percentage of lignin and LHC is percentage of lignin & hemicelluloses in the biomass sample.
These correlations permit the prediction the saccharification degree of the pretreated biomass, which can be used for choice the best pretreatment method.

PROBLEM As is known, natural cellulose of various origin is a semi-crystalline polysaccharide, wh... more PROBLEM As is known, natural cellulose of various origin is a semi-crystalline polysaccharide, which contains 50-80% of crystalline phase in a form of rod-like crystallites of different sizes. Knowledge of sizes of crystallites is very important because it allows clarify the supramolecular organization of cellulose fibers and structure of cellulosic products such as micro-and nanocrystalline particles, nanofibrils, etc. There are several methods for measuring the size of the crystallites: electron microscopy (EM), atomic force microscopy (AFM), wide-angle X-ray scattering (WAXS), etc. Besides the average length of crystallites can be estimated from level-off degree of polymerization (P) of the hydrolyzed cellulose samples. The results of EM, AFM, P and other methods showed that crystallites of natural cellulose have rod-like shape, 3-15 nm in transverse direction and 100-500 nm in longitudinal direction. However, the EM, AFM and P methods require prior isolation of the free crystallites, for example by acid hydrolysis. On the other hand, WAXS is considered as a non-destructive method that is widely used to estimate the sizes of crystallites by means of the Scherrer equation. This equation was proposed as early as the beginning of the 20th century, and it continues to be widely used at present, despite significant limitation, and namely: width of the X-ray diffraction peaks depends not only on the size of crystallites but also on other factors, such as instrumental effect and second-order distortions of crystalline lattice caused by paracrystallinity, dislocations, twinning, internal stresses, boundaries of crystallites, etc. This limitation of the Scherrer equation is often ignored, which leads to unreliable results. For example, study of pulp, bast fibers and cotton cellulose by approximate WAXS-Scherrer method gave low Scherrer's length of crystallites, 20-35 nm, instead of their actual length of 100-200 nm. This discrepancy may be due to neglect of such factors as lattice distortions, instrumental factor, incorrect orientation of the sample during recording, overlapping of reflection (004) by other reflexes, etc. When measuring the transverse sizes of cellulose crystallites, the difference between the results obtained by WAXS-Scherrer method and independent methods is smaller than in the case of determination the length of crystallites. The method of measuring the correction for the instrumental factor is well known. However, the methodology for determining the contribution of lattice distortions to the width of diffraction peaks is complex, and therefore it was used in a minor extent. The purpose of this research was elaboration of simple algorithm for determining the contribution of lattice distortions to broadening of diffraction peaks, which allows to find the actual sizes of crystallites by means of non-destructive WAXS method.

The simple procedure for estimating the parameter of volume distortion of crystalline lattice, δv... more The simple procedure for estimating the parameter of volume distortion of crystalline lattice, δv, for cellulose samples was proposed. This procedure includes determination of interplanar spacing, d, using the sharp diffraction peak of cellulose at the 2 between 22 and 23o, and then calculating the δv value by the correlation equations: δv = 3.084 d (nm) - 1.184 for CIβ samples and δv = 4.163 d (nm) - 1.598 for CIα samples.

The cost of thermal energy was calculated for various types of fossil fuels and biofuels. As it f... more The cost of thermal energy was calculated for various types of fossil fuels and biofuels. As it follows from calculations, the cheapest thermal energy can be obtained by burning a waste of plant biomass, whereas the burning of charcoal, bioethanol or biodiesel gave the most expensive energy. It was shown, the most advantageous is to use the co-combustion of coal and waste of plant biomass. This allows to reduce the cost of thermal energy, decrease the emissions of carbon dioxide, save non-renewable fossil fuel and release the environment from biomass waste. Currently, over 90% of the world's energy or about 540 EJ is produced by burning of various types of fuels. About 80% of them are fossil fuels (natural gas, hydrocarbons of oil, coal, oil shale, etc.), and about 10% are biofuels (biomass, bioethanol, biodiesel, etc.). Resources of fossil fuels are non-renewable and they are gradually depleted. In contrast to them, resources of biofuels can be replenished due to the fact that the plant biomass is constantly renewed in the nature by photosynthesis. However, the production of biofuels is limited by the rate of photosynthesis, the technical capabilities of modern technologies and the requirement of ecological balance. With the purpose of the rational use of energy resources, it is important to know which types of fuels give a cheap and which an expensive thermal energy. For this purpose, the cost of thermal energy (CE) was calculated using data on cost of the fuel (CF) and its net heating value (HV). The cost of thermal energy was calculated by the formula: CE = CF/HV The results of calculation are shown in Table. As it follows from the results, the cheapest thermal energy (about 3/GJ)canbeobtainedbyburningofplantbiomass(sawdustandshavingsofwood,straw,wastepaperandcardboard,etc.);whichisaccumulatedintheworldinamountofabout10billiontonsperyear.Thecostofthermalenergygeneratedfromburningofwoodchipsandpelletsishigher,3/GJ) can be obtained by burning of plant biomass (sawdust and shavings of wood, straw, waste paper and cardboard, etc.); which is accumulated in the world in amount of about 10 billion tons per year. The cost of thermal energy generated from burning of wood chips and pellets is higher, 3/GJ)canbeobtainedbyburningofplantbiomass(sawdustandshavingsofwood,straw,wastepaperandcardboard,etc.);whichisaccumulatedintheworldinamountofabout10billiontonsperyear.Thecostofthermalenergygeneratedfromburningofwoodchipsandpelletsishigher,6-8/GJ, whereas production volume of these types of biofuel are still small and does not exceed 20 million tons per year.

During isolation, purification, modification and application, cellulose undergoes the action of v... more During isolation, purification, modification and application, cellulose undergoes the action of various liquids. As a result of interaction, cellulose sorbs a liquid that is accompanied by diverse changes in structure and properties of this biopolymer depending on nature of the liquid. Negligible sorption of non-and low polar liquids (e.g. hydrocarbons, higher alcohols) has a small effect on mechanical properties [1] and reactivity [2] of cellulose. On the other hand, increased sorption of water and other highly polar liquids by cellulose reduces mechanical properties [2, 3], lowers glass temperature and increases reactivity of the biopolymer [4]. As is known, sorption process of various liquids by cellulose samples is accompanied by an exothermic heat effect, i.e. enthalpy of interaction, which depends on the structure of cellulose and nature of the liquid [5-8]. It is also found that for the same sample the enthalpy of interaction depends on nature of the liquid, and increases in the following order of the liquids: hydrocarbons < higher alcohols < lower alcohols < water < polar organic solvents [8]. Since the sorption is caused by the enthalpy of interaction, these two physicochemical characteristics should be correlated with each other. Unfortunately, a relationship between sorption value and heat of interaction has been investigated in a very limited extent, mainly for cellulose-water system [8, 9]. Therefore, the purpose of this research was to study the dependence of maximum equilibrium sorption on the enthalpy of interaction using liquids of various nature and cellulose samples with different structural features. Another purpose was to use the obtained relationship to predict the sorption value and its impact on various properties of cellulose and other polysaccharides.

The existence and further development of the present civilization requires the expanded generatio... more The existence and further development of the present civilization requires the expanded generation and consumption of energy, chemicals, and materials. Currently, the main energy sources are fossil fuels, namely coal, shale, crude petroleum and gas [1]. Liquid hydrocarbon fuels – gasoline, kerosene, diesel and fuel oil are produced by distillation of crude petroleum and shale oil. Propane and butane fractions of natural gas, oil gas and shale gas after liquefaction also are used as a motor fuel. A small part of thermal energy is produced by burning of plastic waste, synthesized from hydrocarbons. As is known, over 80% of the world's energy demands are met by the combustion of fossil sources [2]. However, these sources are not renewable in the nature, and their reserves are gradually being depleted. In recent years, to reduce the energy deficit and ensure the sustainable development of civilization a considerable attention is paid to the production of biofuels-solid (firewood, wood and paper waste, charcoal, fuel briquettes and pellets, etc.), liquid (bioethanol, biodiesel, etc.) and gaseous (biogas). A significant advantage of biofuels is that the raw materials for their production is a plant biomass, which is continuously renewed in the nature through photo-biosynthesis. Currently, the share of biofuels in the global energy sector reaches 10-12%, and 8-10% only are the other energy sources such as hydro, solar, wind and nuclear power plants [3]. Since over 90% of world energy is thermal energy, the question is how to determine the energy potential of various fuels. The experimental measurement of thermal energy is carried out by burning of small sample of dehydrated fuels or combustible substances in a special device-bomb calorimeter filled with oxygen under pressure [4]. The bomb calorimeter is a complex, expensive and not always available device. In addition, the measurement of combustion heat is lengthy and requires multiple repetitions to obtain a reliable result. Therefore, numerous studies were performed to develop express methods for calculating the combustion heat of various combustible organic fuels, substances and materials. The recent calculation method is based on the simple and attractive hypothesis that partial energetic parameter Eq per1 mole of O2 released during the combustion of 1 mole of organic substance is constant [5, 6]. Thus, the net combustion heat (qe) will be directly proportional to Eq: qe = Eq NO2 /M (1) where NO2 is consumption of oxygen, i.e. number of moles of oxygen required for the complete combustion of 1 mole of organic sample; M is molecular weight of low-molecular compound or repeat link of polymer. The main purpose of this paper was verification of the hypothesis about constancy of Eq – parameter in order to provide a calculation of the value of combustion heat with sufficiently high accuracy.

The existence and further development of the present civilization requires the expanded generatio... more The existence and further development of the present civilization requires the expanded generation and consumption of energy, chemicals, and materials. Currently, the main energy sources are fossil fuels, namely coal, shale, crude petroleum and gas [1]. Liquid hydrocarbon fuels – gasoline, kerosene, diesel and fuel oil are produced by distillation of crude petroleum and shale oil. Propane and butane fractions of natural gas, oil gas and shale gas after liquefaction also are used as a motor fuel. A small part of thermal energy is produced by burning of plastic waste, synthesized from hydrocarbons. As is known, over 80% of the world's energy demands are met by the combustion of fossil sources [2]. However, these sources are not renewable in the nature, and their reserves are gradually being depleted. In recent years, to reduce the energy deficit and ensure the sustainable development of civilization a considerable attention is paid to the production of biofuels-solid (firewood, wood and paper waste, charcoal, fuel briquettes and pellets, etc.), liquid (bioethanol, biodiesel, etc.) and gaseous (biogas). A significant advantage of biofuels is that the raw materials for their production is a plant biomass, which is continuously renewed in the nature through photo-biosynthesis. Currently, the share of biofuels in the global energy sector reaches 10-12%, and 8-10% only are the other energy sources such as hydro, solar, wind and nuclear power plants [3]. Since over 90% of world energy is thermal energy, the question is how to determine the energy potential of various fuels. The experimental measurement of thermal energy is carried out by burning of small sample of dehydrated fuels or combustible substances in a special device-bomb calorimeter filled with oxygen under pressure [4]. The low temperature rise (ΔT) with an accuracy of 0.001 degrees is measured after burning. Using the specific heat of the bomb (cp), an effective energy of combustion is calculated according to equation: U = cp ΔT (1) Three main corrections are introduced in the experimentally obtained U-value and namely, for the contribution of the heat of ignition (c1), for the enthalpy of formation of acids (c2)-nitric acid from residual nitrogen in oxygen and nitrogen of the sample; sulfuric acid from sulfur of the sample, etc., as well as for the heat of dissolution of the acids (c3). Besides, burnt part of the sample is found from the amount of formed CO2. Conventional procedure was used to adjust the experimental combustion energy to standard conditions: T=298.15 K and p= 0.1 MPa. The enthalpy or gross heat of combustion (Q) was calculated by the equation: Q = [U o-(c1 + c2 + c3)]/mo (2) where U o is effective energy of combustion at standard conditions; mo is burnt mass of the sample.

Eliva, 2023

In this research, a new structural model of cellulose and its derivatives was proposed, which inc... more In this research, a new structural model of cellulose and its derivatives was proposed, which includes amorphous-mesomorphous non-crystalline domains and imperfect crystallites with paracrystalline layers on their surface. In this model, the crystallites and non-crystalline domains are located along the fibril and their alternation has a random character. Crystallites are stable and inaccessible to most reagents, typical organic solvents, water, and diluted solutions of acids and bases. Vice versa, non-crystalline domains represent weak and accessible places of cellulose fibrils. As a result, these domains can absorb water vapor, swell in polar liquids, and react; they are easily esterified and etherified, oxidized, and split during thermolysis, hydrolysis, alcoholysis, acetolysis, etc. To characterize the supramolecular structure, it is necessary to know the sizes of crystallites, the type of crystalline allomorph, the degree of crystallinity, interplanar distances, parameters of the crystalline unit cell, and degree of lattice distortion, as well as the content, size, and packing density of paracrystalline and non-crystalline domains. Along with the supramolecular structure of cellulose, it is also important to know the structural characteristics of various esters of cellulose and aliphatic acids with different degrees of substitution such as parameters of crystallites, molar, Van-der-Waals, and free volumes of non-crystalline domains, index of hydrophobicity, etc. Despite a large number of studies, many details of the structural organization of cellulose and its esters are still not sufficiently clear. This paper discusses models of supramolecular structure and improved methods of structural studies that provide new reliable results on the structural organization of cellulose and its esters. It is also shown that the obtained structural characteristics can be used to predict many important properties of these biopolymers.