Pyrolysis Of Tobacco Research Articles

Patterns and kinetics of pyrolysis of tobacco under inert and oxidative conditions

The present work is part of a more extensive research carried out in Naples on cigarette combustion. Theoretical and modelling work highlighted the existence of a misdistribution of the gas flow across the cigarette cross-section, which results into locally variable conditions. As a consequence, oxygen-starving versus oxygen-rich conditions do establish in the pre-heat zone of the cigarette, where pyrolysis of cigarette components takes place. More specifically, oxygen-starving conditions should characterize the process of reaction front propagation in the inner part of the cigarette, close to its axis, while oxygen-rich conditions should establish at the cigarette periphery, close to the paper burn line. The present paper addresses the pattern and the kinetics of pyrolysis under inert and under oxidative conditions of three types of tobacco. The experimental work consists of non-isothermal thermogravimetric analysis at heating rates comprised between 5 and 20 °C/min and with different He–oxygen mixtures. Kinetic expressions for the rate of pyrolysis under inert and under oxidative conditions have been obtained for each ingredient investigated. Results, albeit obtained at sample heating rates smaller than those relevant to actual cigarette burning, highlight the profound differences arising under purely pyrolytic or oxy-pyrolytic conditions as regards the number of reaction steps, the rate, the temperature ranges and yields in solid versus gaseous products of thermal decomposition. The effect of inert/oxidative conditions on the chemical composition of the gaseous products of pyrolysis is discussed in a companion paper [O. Senneca, S. Ciaravolo, A. Nunziata, J. Anal. Appl. Pyrol. 78 (2007) 452].

Composition of the gaseous products of pyrolysis of tobacco under inert and oxidative conditions

Theoretical and modeling work on the process of cigarette combustion showed that in the puffing stage of the burning cycle thermal decomposition of cigarette components in the pre-heat zone of the cigarette may take place under oxygen-starving (in the inner part of the cigarette) versus oxygen-rich conditions (at the cigarette periphery). A companion paper [O. Senneca, R. Chirone, P. Salatino, L. Nappi, A. Nunziata, J. Anal. Appl. Pyrolysis, submitted for publication. [1]] addressed the pattern and the kinetics of pyrolysis under inert versus oxidative conditions of several tobaccos and reported profound differences as regards the number of reaction steps, the rate, the temperature ranges and the yield in solid and gaseous products. The present paper investigates the effects of inert versus oxidative conditions on the composition of the gas produced. The experimental work consists of non-isothermal thermogravimetric experiments in connection with MS analysis. Experiments have been carried out in a Netzsch TG Skimmer apparatus that minimizes secondary reactions of primary decomposition products in the gas phase. MS profiles have been analyzed to underline the differences in the evolution of gaseous products under inert versus oxidizing conditions. Three different tobaccos have been tested, including omogenized and Kentucky tobaccos. A first analysis regarded the temperature at which chemical species are released. Results showed that most species of interest in tobacco smoke, in particular nitrogen containing species, are produced over quite broad temperature ranges under inert conditions and over much more limited ranges under oxidizing conditions. A second comparison regarded the cumulative amount of the species released. Also with this respect large differences have been observed when tobaccos are heated under inert or oxidative conditions. Some species, like CO, CO 2, NO x and H 2O, appear to be strongly favoured by oxidative conditions. Other species such as amines, H 2, aldehydes, aromatics and poliaromatics are instead favoured by inert conditions. Acrolein, HCN, butanone and nicotine are favoured by inert conditions for omogenized tobaccos and by oxidative conditions for Kentucky tobacco.

The vaporization of semi-volatile compounds during tobacco pyrolysis

Pyrolysis of tobacco, a complex biomass matrix, was investigated to further understand thermal decomposition processes that are accompanied by evaporation of relatively stable non-polymeric endogenous compounds. Pyrolysis of two types of tobacco, bright and burley were studied using thermo-gravimetry mass spectrometry (TG–MS) and field ionization mass spectrometry (FIMS) analyses. Tobacco contains biopolymers and many non-polymeric compounds. Unlike many biomass pyrolysis tars derived from wood or cellulose, tobacco pyrolysis tars can contain significant amounts of high molecular weight endogenous constituents such as waxes and terpenes that are transferred intact. The phenomenon of evaporation of high molecular weight non-polymeric compounds is illustrated by tobacco micro-sample pyrolysis in FIMS under vacuum (at a pressure of 10 −4 Torr). These experiments indicate that the evaporation of relatively stable high molecular weight species occurs below about 220 °C generating 300 Da and higher molecular weight products; and, decomposition of tobacco biopolymers such as starch, cellulose, hemicellulose, lignin, and pectin occurs mostly at temperatures higher than 220 °C producing species mostly with molecular weight below 300 Da. Some of the high molecular weight compounds, such as stigmasterol (412 Da), α-tocopherol (430 Da), and solanesol (630 Da), were tentatively identified using the FIMS spectra.

Effect of manganese-based pigment catalyst on CO removal during biomass pyrolysis

A commercially available black pigment was evaluated for its potential as a CO oxidation catalyst during the pyrolysis of biomass. Characterization by X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that the pigment consisted of a mixed oxide system (Cu 1.5Mn 1.5O 4–Mn 3O 4–Fe 2O 3) with an average particle size of 30–300 nm. The as received pigment catalyst was able to completely oxidize CO to CO 2 in a 4% CO–21% O 2–He gas mixture. In this study, the effect of catalyst on CO removal was evaluated during the pyrolysis of tobacco in inert and oxidizing conditions. The experiments were carried out in a flow tube reactor, which was connected to a multi-channel gas analyzer capable of measuring CO, CO 2 and O 2 concentrations. The catalyst was able to decrease the amount of CO production by 56% during the pyrolysis of biomass (tobacco) in the presence of oxygen (21% O 2–He). Oxidation of the biomass/catalyst mixture started at a lower temperature of 260 °C as opposed to a higher temperature of 300 °C in the absence of catalyst. Experiments in thermo gravimetric analyzer and differential scanning calorimeter (TG/DSC) mass spectrometer showed evidence of two-stage oxygen consumption during the pyrolysis of biomass/catalyst mixture while pure biomass pyrolized in single-stage oxygen consumption. Based on the experimental findings, a mechanism of reaction is proposed. The results show that the manganese-based mixed oxide pigment is a promising CO oxidation catalyst for biomass pyrolysis.

In Situ High-Temperature EPR Investigation of the Charring of Tobacco and the O2-Induced and H2O-Induced Behavior of the Char

In situ high-temperature EPR has been used to study the 350 and 500 °C pyrolysis (under a He atmosphere) of tobacco, as well as the EPR-signaled changes in the resulting char under exposure to O 2 and H 2 O after quenching to room temperature. Exposure of a char to O 2 leads to a large increase in free radical concentration, especially for the 350 °C char. Exposure of the char to both O 2 and H 2 O yields an additional increase in free radical content (followed by a decrease after a maximum is reached), the magnitude of this increase being roughly half that of the initial O 2 -generated increase. The observed patterns result from a complicated chemical interplay involving the creation and destruction of carbon-centered and oxygen-centered free radicals.

Radicals from the Pyrolysis of Tobacco

The fractional pyrolysis of Bright tobacco was studied in an inert nitrogen environment at atmospheric pressure over a temperature range of 200−700 °C, using a continuous-flow reactor system. The effect of pyrolysis conditions on the generation of free radicals and their distribution among total particulate matter (TPM), char residue, and the gas phase was characterized using electron paramagnetic resonance (EPR) and EPR spin-trapping techniques. It was found that the fractional pyrolysis of tobacco led to the generation of free radicals with g-factors of 2.0035−2.0040. They were formed during pyrolysis at temperatures of >380 °C and were present in both char and TPM. The concentration of these radicals in TPM varied from 0 spins/g at 240 °C to 11 × 1016 spins/g of TPM at 620 °C. The concentration of these radicals in the char residue increased as the pyrolysis temperature increased; a maximum concentration of 1.2 × 1019 spins/g of char at 480 °C was obtained, and then the value declined. The g-values of ...

Application of time-of-flight mass spectrometry with laser-based photoionization methods for analytical pyrolysis of PVC and tobacco

PVC and tobacco samples were pyrolyzed in a rotary furnace at different temperatures and reaction gas compositions. Released gaseous products were analyzed using single photon ionization (SPI)/resonance enhanced multiphoton ionization (REMPI)–time-of-flight mass spectrometry (TOFMS). These soft and selective ionization techniques allow fast and comprehensive on-line monitoring of a large variety of aliphatic and aromatic substances without fragmentation of the molecular ions. The thermal decomposition of PVC led to the appearance of chlorinated aromatic compounds at trace levels, which could be detected with SPI–TOFMS. Polycyclic aromatic hydrocarbons (PAH) were simultaneously accessible by REMPI–TOFMS. Different tobacco types can be distinguished by photoionization mass spectrometry of their gaseous pyrolysis products. In addition, pyrolysis products can be classified in three groups depending on their behaviour at different pyrolysis temperatures, which might help to unravel formation mechanisms and chemical pathways of hazardous substances.

Study on tobacco components involved in the pyrolytic generation of selected smoke constituents

The aim of this study was to investigate the contribution of various tobacco components to the generation of smoke constituents using a tobacco pyrolysis model. We analyzed the amounts of primary tobacco components (sugars, protein, polyphenols, alkaloids, organic acids, inorganics etc.) in flue-cured and burley tobacco leaves. Each of the components was added to the tobacco leaves at the 0.5-fold and 1.0-fold amount naturally present in the leaves. The treated tobacco samples were pyrolyzed at 800 °C in a nitrogen atmosphere with an infrared image furnace, and the selected smoke constituents (benzo[ a]pyrene, hydrogen cyanide, carbonyl compounds, aromatic amines, volatile organic compounds and phenolics) were quantitatively analyzed by several methods, including high performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC–MS). The contribution of each tobacco component to the generation of selected smoke constituents was estimated from a regression line determined by the three yields (no addition, 0.5-fold addition, and 1.0-fold addition). The results of this study can provide useful and comprehensive information on the relationship between tobacco components and selected smoke constituents during pyrolysis.

Numerical simulation of a burning cigarette during puffing

The mathematical modeling of biomass smoldering requires an accurate knowledge of pyrolysis and combustion kinetics of biomass materials and access to reasonably reliable experimental data. In this work, the kinetic parameters of tobacco pyrolysis and combustion were obtained from the existing literature; the temperature–time history of tobacco in a puffing cigarette was obtained from the existing experimental data of temperature distribution in a cigarette. A three-dimensional model for a cigarette was constructed using the principles of the conservation of mass and momentum. The numerical simulation of a puffing cigarette was performed using the existing kinetics data for tobacco pyrolysis and combustion and the time-temperature history in a cigarette. The numerical results show a good agreement with the experimental data for the evolution rates and yields of CO, CO 2, and O 2 in the mainstream smoke for individual puffs.

Effects of temperature, atmosphere and pH on the generation of smoke compounds during tobacco pyrolysis

The pyrolysis of tobacco under a variety of conditions was performed to examine the generation profiles of 29 known toxic compounds in tobacco smoke (hydrogen cyanide, benzo[ a]pyrene, aldehydes, volatile organic compounds, phenolics, aromatic amines, etc.). The generation profiles of smoke compounds varied according to three conditions: the pyrolysis temperature (300–1000 °C), the pyrolysis atmosphere (in nitrogen and air) and pH of the tobacco leaf (2.89–7.07). Most of the smoke compounds (28 compounds) were generated primarily at temperatures less than 800 °C. More than half of the smoke compounds (17 compounds) were unaffected by the type of atmosphere, and seven compounds were significantly affected by pH. These results can provide basic and useful information to further study on the formation mechanisms and the technology involved in the control of smoke generation.

Synchronous fluorescence for simultaneous determination of hydroquinone and resorcinol in air samples.

Several phenolic compounds are present in tobacco smoke. They are formed from the pyrolysis of tobacco during the smoking process and all of them are toxic. Therefore, the determination of these compounds in air samples is important. A rapid, simple, and sensitive method using a synchronous spectrofluorimetry technique was developed to quantify hydroquinone and resorcinol simultaneously. One of the advantages of this method is the simple and rapid sampling technique, which uses water as the absorption solution of the analytes in the air sample. The precision of the method (%RSD) was 1.8% and the detection limits were 0.125 mg m(-3) and 0.292 mg m(-3) for hydroquinone and resorcinol, respectively.

Physico-chemical processes occurring inside a pyrolyzing two-dimensional tobacco particle

A two-dimensional, variable property, mathematical model of the transient pyrolysis of tobacco particle, in response to the smoldering (low heating rate) and puffing (fast heating rate) conditions in a burning cigarette, is presented. The model considers pyrolysis of tobacco obeying four-step Arrhenius kinetics, evaporation of water from tobacco following a mass-transfer and rate-determined process, and the formation of carbonaceous residue. From the physical point of view, the model describes convective, conductive and radiative heat transfer, and velocity and pressure variations interior to the porous tobacco particle (Darcy’s law). Furthermore, porosity, permeability and thermal conductivity vary with the composition of the reacting medium. Time and space evolution of the main variables, and reaction product distribution, are simulated by varying the tobacco heating rates.

Modeling the evolution of volatile species during tobacco pyrolysis

A great need exists for comprehensive biomass-pyrolysis models that could predict yields and evolution patterns of selected volatile products as a function of feedstock characteristics and process conditions. Low heating rate data obtained from a thermogravimetric analyzer (TGA), coupled with Fourier transform infrared analysis of evolving products (TG-FTIR), were used to perform kinetic analysis of tobacco pyrolysis. The results were utilized to create input to a biomass-pyrolysis model based on first-order kinetic expressions with a Gaussian distribution of activation energies. Pyrolysis simulations were carried out for high heating rate conditions, and predicted product yields were compared with literature data.

Product distribution from the pyrolysis modeling of tobacco particles

A mathematical model of tobacco pyrolysis accounting for the transport and chemical processes is presented. Pyrolysis products are formed via a kinetic scheme based on the functional groups (FG) and prescribed with a single-step multi-reaction model. Transport processes include heat transfer (conduction, convection, and radiation), mass transfer (diffusion and convection), pressure and velocity within a tobacco shred. The pressure and velocity variations within a tobacco shred are described according to the Darcy's law. The variation of physical properties such as porosity, conductivity, permeability, and mass diffusivity of a shred is monitored with the extend of pyrolysis. The finite difference formulation of the mathematical model is based on the hybrid scheme and a two-step splitting procedure is used for the treatment of chemical processes and transport phenomena. Time and space evolution of the main variables, and the pyrolysis product distribution, are simulated for both smoldering and puffing conditions. The simulation results show a reasonable agreement with the available experimental data of the yields of selected species for smoldering and puffing.

A Mathematical Model of Cigarette Smoldering Process

Abstract A mathematical model for a smoldering cigarette has been proposed. In the analysis of the cigarette combustion and pyrolysis processes, a receding burning front is defined, which has a constant temperature (~450 °C) and divides the cigarette into two zones, the burning zone and the pyrolysis zone. The char combustion processes in the burning zone and the pyrolysis of virgin tobacco and evaporation of water in the pyrolysis zone are included in the model. The hot gases flow from the burning zone, are assumed to go out as sidestream smoke during smoldering. The internal heat transport is characterized by effective thermal conductivities in each zone. Thermal conduction of cigarette paper and convective and radiative heat transfer at the outer surface were also considered. The governing partial differential equations were solved using an integral method. Model predictions of smoldering speed as well as temperature and density profiles in the pyrolysis zone for different kinds of cigarettes were found to agree with the experimental data. The model also predicts the coal length and the maximum coal temperatures during smoldering conditions. The model provides a relatively fast and efficient way to simulate the cigarette burning processes. It offers a practical tool for exploring important parameters for cigarette smoldering processes, such as tobacco components, properties of cigarette paper, and heat generation in the burning zone and its dependence on the mass burn rate.

Vapor pressure measurements of tobacco pyrolysis tar by a non-isothermal Knudsen effusion method

Vapor pressures of thermal decomposition products of tobacco were measured using a molecular effusion/thermogravimetric technique based on a non-isothermal Knudsen effusion method. Molecular weight distributions of the tobacco tar and its fractions were obtained by Field Ionization Mass Spectroscopy. The preliminary tobacco tar study showed that the heat of vaporization and boiling point at 760 Torr of the initial 24% mass loss fraction were about 129 kJ mol −1 and 568 K, respectively. In the case of the hexane phase partitioned tar, the heat of vaporization and boiling point at 760 Torr of the initial 15% mass loss fraction were about 118 kJ mol −1 and 544 K, respectively.

Characterization of char from the pyrolysis of tobacco.

Pyrolysis of tobacco was studied in oxidative and nonoxidative (inert) environments at atmospheric pressure and temperatures ranging from 150 to 750 degrees C. The objective was to study the effect of pyrolysis conditions on the characteristics of the solid residue, i.e., char. The char was characterized using cross-polarization (13)C nuclear magnetic resonance (CPMAS NMR), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), the Brunauer-Emmett-Teller (BET) surface area, and the elemental composition. The char yield from pyrolysis (i.e., nonoxidative) decreased sharply with an increase in temperature to ca. 22% (dry, ash-free basis) at high temperatures. In oxidative pyrolysis, i.e., in 5% oxygen, the char was completely oxidized above 600 degrees C. The gaseous product from pyrolysis at high temperatures contained a significant concentration of hydrogen. The surface area of the char was low, with a maximum of 8 m(2)/g at 400 degrees C. SEM analysis indicated that pyrolysis of the tobacco led to a gradual accumulation of inorganic crystals on the exposed surfaces, and some constituents also melted, resulting in the formation of vesicles by evolving gas. NMR analysis showed significant changes in pectin and sugar constituents of the tobacco and breaking of glycosidic bonds of cellulose at 300-500 degrees C before the char became predominantly aromatic at high temperatures. FTIR results showed a continuous decrease in the intensity of the OH stretch with temperature and the aromatic character to be at maximum at 550-650 degrees C. The H/C ratio of the char decreased continuously with temperature, while the O/C ratio became constant above 300 degrees C due to the presence of oxides and carbonates in the char. The results are consistent with the analysis of the evolved gases.

Chemical and biological studies of a new cigarette that primarily heats tobacco.: Part 1. Chemical composition of mainstream smoke

A new-technology cigarette has been developed. While the new cigarette burns some tobacco, it does not use tobacco as the fuel to sustain combustion and provide heat to the cigarette. Rather, the new cigarette primarily heats tobacco thereby reducing products of smoke formation mechanisms such as tobacco combustion, tobacco pyrolysis and pyrosynthesis. The mainstream smoke composition from a cigarette based on the new design (TOB-HT) has been characterized in comparative chemical testing with two reference cigarettes using the FTC puffing regimen. Thermal properties, UV absorption characteristics, elemental composition and materials balance studies all suggest a simplified smoke aerosol. Twenty-five smoke constituents (“target compounds”) identified by the scientific community as compounds that may contribute to the diseases statistically associated with smoking have also been measured. Mainstream smoke concentrations of most target compounds are significantly lower with the TOB-HT cigarette when compared with reference cigarettes in the ultra-light “tar” and light “tar” categories. Taken together, chemical analysis results suggest simplified TOB-HT smoke chemistry with marked reductions in specific chemicals reported to be biologically active.

Pyrolysis of Cherry Red Tobacco and 1-Deoxy-1-[(S)-2-(3-pyridyl)-1-pyrrolidinyl]-.beta.-D-fructose (Pyranose and Furanose Isomers) Amadori Products of Cherry Red Tobacco

Nornicotine (NN) reacted with glucose and malic acid as a catalyst in dry methanol produced two NN Amadori rearrangement isomers (NDF). 1-Deoxy-1-[(S)-2-(3-pyridyl)-1-pyrrolidinyl]-beta D-(fructopyranose) was the major isomer and -(fructofuranose) the minor isomer. Pyrolysis of NDF at 500 degrees C produced nicotine, NN, myosmine, pyridine, beta-picoline, 3-vinylpyridine, substituted NN, and compounds that produced pleasant and sweet aromas. Eleven percent of the NN content from cherry red (CR) tobacco in this study was in NDF form. CR tobacco pyrolyzed at 500 degrees C produced 10 of the same pyrolytic products as the NDF isomers. This suggests that NDF in CR tobacco possibly contributes the same pyrolytic products as the synthetic NDF. Pyrazines, lactones, furan derivatives, and short-chain carboxylic acids were also produced from pyrolysis of CR tobacco.

Experiences with grade assessment by “condensate predictions” from tobacco pyrolysis

In order to predict the particulate matter yield (PMY) of different tobacco grades, pyrolysis studies have been carried out for several years. All these investigations were made with ground material. Thus differences in physical properties, which influence the condensate delivery of a cigarette, have been disregarded. This paper shows that the package density is the main influence on the PMY values in the pyrolysis experiment. The relationship between PMY and package density is unique for each tobacco grade, which results in a delivery of tobacco mixtures that in the low-density region (260–200 mg/ml), is non-linear. The package density has a direct influence on the thermal decomposition. PMY values and cigarette deliveries can, therefore, only be correlated when the tar yield per cigarette is related to the the amount of tobacco burned during the puffs. Only by incorporating the effect of cigarette design (which can be done economically using computer models) it is possible to calculate this amount of tobacco.