The goal of Heated Tobacco products (HTPs) is to devolatilize nicotine from the tobacco by a controlled electrical heating without inducing combustion and to thereby reduce the formation of harmful and potentially harmful compounds typically related to self-sustained combustion of tobacco as in conventional cigarettes. Here, we have instrumented a commercial puffing machine and an HTP with a micro-positioning system of a thin thermocouple (0.25 mm). The puffing was conducted under N2 or air. We provide the evolution of temperature as a function of time during standard puffing cycles and along the radial position within the tobacco plugs of tobacco sticks used as part of an electrically heated tobacco system (EHTS) during operation. The temperature profiles are nearly the same for the two atmospheres showing only minor influences of oxygen (maximum temperatures: 318 degrees C in air, 308 degrees C in N2, at the end of the puffing cycle). The thermal degradation of the tobacco remains always globally endothermic due to the high flow rate of the cold air flowing the tobacco during the puffing. To better understand the differences between air or N2 puffing, we have imaged the solid residues collected in the tobacco plugs by FTIR spectroscopy. The residues are clearly differentiated whatever their radial positions between air or N2 by principal component analysis of the FTIR spectra. This result highlights similar surface oxidation phenomena of the solid residue independent of the positions. Moreover, analysis of the FTIR spectra indicates that the heating of the tobacco in the EHTS is relatively uniform along the electrically-controlled heater without signs of local hot spots. These experiments were also completed by calorimetry of tobacco upon pyrolysis or oxidation, in a 3D sensor and under a fixed bed configuration (not in the EHTS). We evidence significant exothermic phenomena from about 230 degrees C mainly due to gas-phase oxidation of primary volatiles in the hot gas stream. During the operation of the EHTS, such potential exothermicity is counter-balanced by strong heat losses and the high flow rate of cold air flowing through the tobacco bed during the puffing. This leads to the observed net endothermic degradation of tobacco during EHTS operation.

Catalyst deactivation and shape selectivity in evolved products and retained coke are studied on medium, large and extra-large pore zeolites with varying Si/Al ratios in the disproportionation of anisole. Deactivation modelling as a function of time on stream highlights the key role of the catalyst pore volume. Changes in selectivity between the primary (methylanisole) and secondary (cresol) products are due to the overtaking of one path over a second for the production of cresol. The nature of the products (methyl phenols) inhibits the formation of “usual” polyaromatic and non-oxygenated coke via the Sullivan mechanism, leaving only adsorbed oxygenated monoaromatics, available for transalkylation reactions with the feed, having adsorbed and fouled most of the available surface in the catalyst channels.

The understanding of tobacco pyrolysis and oxidation mechanisms is an important topic for tobacco science in order to reduce the emissions of toxic species and to better control the conversion of tobacco in electrically heated tobacco products (EHTPs) by avoiding combustion. In this work, we have instrumented experimental Tobacco Heating Devices (expTHD) with a micro-positioning system of a thin thermocouple. Each expTHD has a pre-programmed set temperature (between 250 and 550 degrees C) to be able to investigate the influence of temperature on tobacco conversion characteristics and emissions. Puffing cycles were conducted under air or N2 in order to understand the effect of oxygen on tobacco conversion and the resulting emissions. Electrically Heated Tobacco Products (EHTPs) were heated by the expTHD to the different final set temperatures, and puffs were drawn according to the specified puffing cycles. The conversion of tobacco becomes clearly exothermic with air from 400 degrees C after 8 puffs, indicating that combustion was triggered. Below a set temperature of 400 degrees C, the tobacco conversion is always net endothermic, which includes the tobacco temperatures of commercially available Tobacco Heating Systems (THS) during operation (typically lower than 325 degrees C). Furthermore, the volatiles emitted during the puffing cycles were sampled in cold impingers. PAHs (naphthalene, phenanthrene, pyrene, and benzo [a]pyrene) were quantified by HPLC-UV Fluorescence. Benzene and toluene were quantified by GC/MS. Gases (CO, CO2, CH4, H2) were quantified by FTIR and mu GC. The mass yields of all these species are presented as a function of the final set temperature of the expTHD and of the carrier gas used during the puffs (air or N2). CO2 yields are higher for air than for N2 even at 250 degrees C, highlighting some low temperature oxidation reactions, but they did not lead to a detectable exothermic regime. A jump in CO formation is observed from 400 degrees C under air, indicating combustion of the tobacco. Benzene and PAHs are promoted by air (compared to N2) from 400 degrees C (heater set temperature). Therefore, air does not promote the formation of these species during the operation of the commercially available THS.

The conversion of anisole has been studied at 773 K on HZSM-5 zeolites with nine Si/Al ratios ranging from 9 to 201. The influence of the distribution of Bronsted Acid Sites on catalytic activity and reaction products selectivity has been studied experimentally. The adsorption energies for reactant and products on isolated and paired aluminium have been modelled by DFT. The Si/Al ratio does not affect any selectivity. Higher concentration of Bronsted acid sites leads to higher activity from Si/Al= 201 to 29. The shift from mostly isolated to increasingly paired Al strongly inhibits the conversion and initial activity. This is attributed to product desorption becoming the limiting step in the Sabatier volcano plot. This finding is consistent with the significant increase in adsorption energies between isolated and paired sites. When the adsorption energy of gaseous anisole becomes similar to that of its products, an auto -inhibition effect takes place as already known for liquid-phase processes.

Anisole conversion on an MFI zeolite (SiAl = 43) at atmospheric pressure and 673 K is a model for the upgrading of bio-oils produced by catalytic fast pyrolysis (CFP) of biomass. Catalyst activity and selectivity are measured experimentally, while deactivation is studied experimentally and by DFT calculations. Anisole dismutation is a Friedel-Crafts-type alkylation between two anisole molecules. Consecutive reactions produce phenol and methyl anisoles, cresols and xylenols, as primary, secondary, and tertiary products respectively. The resonance effect of the hydroxyl and methoxy groups, combined with the "product shape selectivity" of the zeolite, results in a high selectivity for p-methyl-anisole, o-cresol and 2,4 xylenol. Coke deposition consists exclusively of methyl phenols with 0-4 methyl groups. Their retention is due to steric hindrance for the larger ones and strong adsorption on stronger acid sites for the smaller ones, as confirmed by DFT calculations. Catalyst deactivation occurs by progressive fouling of the micropores rather than by poisoning.

The coupling of thermochemical and biological conversion of biomass is a promising strategy to produce chemicals in future integrated biorefineries. Indeed, thermochemical conversion such as pyrolysis is a fast process without any solvent or enzyme for the depolymerisation of biomass. In this work, cellulose was pyrolyzed to produce sugars which have been then fermented by bacteria (Clostridium acetobutylicum) to produce acetone and butanol. This type of bacteria presents an interesting biological platform: it is resilient, easily up-scalable and Clostridium can be genetically engineered to target various other chemicals. Pyrolysis of cellulose was performed in a continuous fluidized bed reactor equipped with a staged condensation system, including a warm electrostatic precipitator. Different bio-oil fractions rich in levoglucosan (LVG) and with different concentrations in inhibitors for the fermentation stage were produced. LVG was found to be non-fermentable by C. acetobutylicum. Therefore, the bio-oil fractions were hydrolysed to obtain fermentable glucose. The mechanisms of acid hydrolysis (with diluted H2SO4) of LVG and cellobiosan have been revealed by high resolution mass spectrometry. The microorganisms were not able to grow with all hydrolysed bio-oil fractions depending on the concentration in inhibitors (aldehydes and organic acids). The fractions rich in LVG (and then glucose) lead to normal bacterial growth and normal fermentation products pattern without the need of detoxification. These results show the importance of a pyrolysis process with a staged condensation as a preliminary step for fermentation. It opens the road to production of various cellulose-derived chemicals by bacteria.

Guaiacol or 2-methoxy phenol is one of the main primary tars produced during lignin pyrolysis. Tar conversion in the gas phase influences the production of gaseous and condensable products, and is also responsible for PAH and soot formation during biomass and bio-oil gasification or combustion. Guaiacol pyrolysis and oxidation under stoichiometric conditions were studied in a jet stirred reactor between 623 and 923 K for a residence time of 2 s and under a pressure of 800 Torr (106.7 kPa). Speciation was obtained thanks to online gas chromatography using flame ionization detection and mass spectrometry and allowed the quantification of 22 species in pyrolysis and 42 species in oxidation. Decomposition of guaiacol starts at 650 K, and a conversion degree of 50% is obtained at about 785 K in pyrolysis and 765 K in oxidation. The main products of reaction are pyrocatechol o-HOC6H4OH, o-hydroxybenzaldehyde, methylcatechols, and light products, such as methane, carbon monoxide, ethylene, and hydrogen. A detailed kinetic model based on a combustion model for light aromatics and anisole has been extended to guaiacol. Thermochemical data of guaiacol and main products were calculated theoretically at the CBS-QB3 level of theory. The model predicts well the conversion of guaiacol and the formation of the main products. Guaiacol decomposes mainly through a unimolecular O-C bond breaking to hydroxy phenoxy and methyl radicals in both pyrolysis and oxidation, but H atom abstractions are also of importance in the low temperature range of the study. The unimolecular mechanism leads mainly to pyrocatechol and methylcatechols, whereas the chain radical mechanism is responsible for the formation of hydroxybenzaldehyde. As for anisole but in a much lower extent, an early formation of benzene and soot precursors is observed.

Among alternative techniques to overcome the difficulties associated with thermal regeneration of coked zeolite, non-thermal plasma can be considered as one of the most promising technology. A complete regeneration of zeolite can be achieved at room temperature with a low energy consumption. The active species responsible for catalyst regeneration are the short-lived oxygenated species and not ozone. Based on EPR analysis, which allows the mapping of radicals, the active species generated by NTP are able to diffuse within zeolite eliminating coke molecules. The efficiency of regeneration is directly related to the number of active species present in gas phase. A simple way to increase their concentration consists to substitute N-2 by a noble gas as He. In this case, coke is totally oxidized into CO2, 6 times faster than under air. (C) 2017 Elsevier B.V. All rights reserved.

Mesopores are “highways” for mass transfer inside zeolite crystals and enhance the formation of mono-aromatic hydrocarbons from biomass pyrolysis.

In this work, several models have been coupled in order to represent the whole forest-to-energy production chain: the growth phase, the primary transformation, and the ultimate conversion to heat and/or electricity. Combined with literature data for wood transportation, they gave a complete balance of emissions to compare with fossil-based alternatives. An economic analysis completes the work. The results show that wood-based scenarios do perform better than their fossil counterparts, but also that the primary transformation and transportation items can greatly diminish this advantage. Further work will focus on determining the best metric to assess the climate change impact of forestry scenarios based on the timing of carbo dioxide emissions as well as geophysical effects such as albedo and evapotranspiration.

CH4 decomposition over a wood char was investigated as an alternative green catalyst.to produce hydrogen from hydrocarbons. Pyrolytic carbon (pyrocarbon) deposition leads to apparent deactivation of the catalyst by pore-mouth plugging. The activity of the carbon bed and its available surface area are easily restored by H2O gasification. The used char with pyrocarbon deposition was even found to be more reactive to gasification than the fresh char used in our conditions. This finding was highlighted by: (i) determination of gasification reaction extents by steam, (ii) temperature-programmed oxidation (TPO) of the fresh, used and reactivated chars and (iii) TPO under differential scanning calorimetry of these chars and demineralised chars. High-resolution transmission electron microscope (HRTEM) analysis of the chars showed different multiscale organisation of the carbon materials (disordered and graphitic mesoporous nanostructures). The fast regeneration of the used char could be attributed to the catalytic effect of the minerals present in the char that are reduced under our conditions of CH4 conversion. The predominant oxidation of the pyrocarbon compared to the char during its regeneration is evidenced through differential annealing (at 1800 degrees C) followed by XRD analysis. The oxidation of pyrocarbon is faster than the oxidation of the weakly reactive mesoporous carbon in char as shown by the HRTEM analysis. Consequently, wood char is an effective, easy to regenerate and cheap catalyst for converting hydrocarbons (CH4 or tar) into syngas. (C) 2014 Elsevier B.V. All rights reserved.

The aim of this work was to identify and quantify the chemical and structural modifications occurring during the pyrolysis of Miscanthus x giganteus. Miscanthus was pyrolyzed at slow heating rate (5 K/min) in the temperature range 200-400 degrees C. The biochars were then characterized by combining diffuse reflectance infrared Fourier transform spectrometry (DRIFTs) and Ultraviolet Raman spectrometry (UV Raman). In addition, the quantification of the functional groups remained on the biochars was conducted by temperature programmed desorption-mass spectrometer (TPD-MS) analysis.DRIFT analysis showed that the decrease in the hydroxyl and C-H stretching bands and the evolution of the carboxyl vibration peak mainly occur between 300 and 350 degrees C. The evolution of the main markers (H2O, CO, CO2, CH4, and H-2) of the functional groups presents in the biochars as analyzed by TPD-MS is consistent with the spectroscopic analysis. It shows two peaks. The first one in the temperature range of 200-380 degrees C was explained by the loss of the main O- and H- containing groups and to the main primary volatile compounds. The second step (above 380 degrees C) can be interpreted by the rearrangement of the aromatic rings in the polycyclic structure. (C) 2015 Elsevier B.V. All rights reserved.

The main purpose of this work was to understand property modifications during lignocellulosic biomass pyrolysis by using different experimental techniques (thermal analysis methods, x-ray diffraction and diffuse reflectance infrared Fourier transform (DRIFT)). Miscanthus x Giganteus as energy crop and its components (cellulose, holocellulose and lignin) were used as feedstock in this investigation. Pyrolysis tests were carried out in laboratory scale reactors with a slow hating rate of 5 °C/min at three different temperatures 280, 300, 350 °C. The initial samples and their biochar products were investigated with the objective of their effective valorization. X-ray diffraction analysis demonstrated the presence of mineral classes in the biochars like silicate. Analysis of functional groups showed the progressive decrease of carboxyl groups and the increase of carbonyl during pyrolysis. The greatest change in surface functionality was identified at 300-350 °C.

Biosourced aromatics (BTX (benzene, toluene, xylene) and phenols) could be produced by lignin pyrolysis coupled with catalytic hydrodeoxygenation (HDO) of uncondensed pyrolysis vapors. Guaiacol is used as a model compound to study the catalytic HDO over Fe/SiO2 catalyst. Experiments were conducted in a fixed bed reactor operated at 673 K (1 atm) with a gas mixture (guaiacol, H-upsilon, H2O, CO, CO2) that mimics the real gas composition from lignin pyrolysis. Fe/SiO2 catalyst was shown to be selective for guaiacol HDO into benzene and phenols because it does not catalyze the aromatic ring hydrogenation. Major and minor products are modeled by a semidetailed kinetic mechanism. A deactivation law is also determined. The kinetic model is then included in an Aspen Plus model of lignin to BTX process. Aspen Plus model handles (1) pyrolysis of lignin, including char, oligomers, gases and aromatic yields, (2) catalytic conversion of aromatics by the kinetic model, (3) heat exchangers, and (4) BTX vapors recovery by scrubbing with 1-methyl-naphthalene. Mass and carbon balances, heat demand, and selectivity in desired products are given for the overall process. The effect of gas dilution from pyrolysis reactor on BTX losses, heat demand, and scrubbing solvent flow rate is highlighted. High carrier gas flow rates (as required for biomass pyrolysis in fluidized bed) lead to the entrainment of fines and oligomers, dilute the products, and impact considerably the process intensification.

We provide the first process simulation able to depict a complete life cycle inventory of a biomass gasification combined heat and power (CHP) plant. The model predicts the detailed mass and energy balances, minor compounds emissions (such as NOx, SOx, aromatics, etc.). It is based on a phenomenological approach for dryer, reactors (gasification and combustion) and scrubber modeling. Process units are modeled with Aspen Plus® models completed with dedicated Fortran sub-models when more details are required. The gasifier is a Dual Fluidized Bed (DFB). It is decomposed in three sections, describing the three main mechanisms occurring in the reactor: wood pyrolysis, secondary reactions and char combustion. At the outlet of the gasifier, the complete composition of the syngas is predicted, which includes water, permanent gases, inorganics, particles and tars (phenol, benzene, toluene, styrene, indene, naphthalene, acenaphthylene, anthracene, phenanthrene, pyrene). Simulation results were validated against measurements from a pilot plant and other literature data. A wet conventional syngas cleaning system for gasification plant, including cyclone, catalytic tar cracker, syngas cooler, bag filters, water scrubber and wastewater treatment was considered and modeled. The complexity of tar composition allows a reliable determination of tar dew point. At the outlet of the cleaning system, syngas is burned in gas engines. Gaseous emissions (NOx, SOx, etc.) of the gas engines and the DFB combustor are also handled by the model as well as ashes and liquid waste. The predicted electrical and thermal efficiencies are 27 and 39% respectively.

The modeling of biomass gasification processes by simulators such as Aspen Plus is a powerful tool to assess mass and energy balances and to optimize process designs. A detailed model of the gasification reactor is one of the key points to achieve an accurate process description. A model for biomass gasification in dual fluidized bed (DFB) reactors by coupling Aspen Plus and dedicated Fortran files is presented. The DFB is divided into three modules according to the main chemical phenomena: biomass pyrolysis, secondary reactions, and char combustion. Mass yields of permanent gases, water, 10 tar species, and char are modeled with respect to the reactor temperature by a pyrolysis correlation. The secondary reactions are modeled by a semidetailed kinetic mechanism that handles gas-phase and catalytic conversions over char of CH4 and lumped tar species (phenol, naphthalene, benzene, and toluene), gas-phase water gas shift reaction (WGSR), char, and soot steam gasification. The calculated compositions of permanent gases and tars, flow rates, and lower heating values are compared with experimental data for two DFB technologies (Tunzini Nessi Equipment Companies (TNEE) and Battelle High Throughput Gasification Process (FERCO)). The syngas composition and flow rate are very sensitive to the WGSR kinetic. The rate laws for WGSR are reviewed. An optimized kinetic law for WGSR is given.

Fe/SiO2 is shown to be a selective catalyst for guaiacol hydrodeoxygenation (HDO). Guaiacol is used as a model compound to study the conversion of lignin pyrolysis vapours into aromatics (benzene, phenols). The effect of each individual gas present in a pyrolysis gas (H2, CO, CO2, H2O, CH4) on the selectivity of a 10wt% Fe/SiO2 catalyst is studied (673K, atmospheric pressure, 50mol% H2, 1/WHSV=0.6gcath/ggua). The speciation of the iron phase (metallic (α-Fe), carbide (Fe5C2), oxide (Fe3O4), and super-paramagnetic) in spent catalysts is revealed by XRD and Mössbauer spectroscopy as a function of gases composition. At least 3 types of carbonaceous deposit were evidenced by TPO analysis. TEM observations showed that iron particles size is not markedly affected by the reaction and that carbon deposit mainly occurs in the vicinity of iron particles. When all the gases except methane (Guaiacol+H2+CO+CO2+H2O) are simultaneously in the feed stream, the conditions are still sufficiently reducing to maintain the activity of the catalyst (66% of benzene and toluene carbon yield, 7.5gcath/ggua). The effects of support (silica or activated carbon-AC) and iron loading (5, 10, 15wt% Fe/SiO2) were also studied. 10wt% Fe/AC has a higher selectivity in phenol and cresols production than Fe/SiO2. Active sites and reaction mechanisms are discussed.

Tar reduction and monitoring is the major stake for gasification processes. Pyrolysis is the precursor mechanism of the gasification of solid fuels and tar production. The evolution of gas and tar composition produced from wood chips pyrolysis was investigated in a tubular reactor as a function of its wall temperature (700-1000 degrees C, with gas mean residence times of 1.1-2.7 s). High thermal severities lead to the "gasification" regime, promoting gas production from tar conversion. Tar (benzene, toluene, o- and m-xylenes, phenol, indene, o-, m-, and p-cresols, naphthalene, 1- and 2-methylnaphthalenes, acenaphthylene, and phenanthrene) were quantified by gas chromatography/mass spectrometry (GC/MS) analysis using deuterated internal standards. Closed mass balances were obtained. A simplified chemical scheme of secondary tar conversion is proposed. Under the investigated range of thermal severity, CH4 production is mainly controlled by aromatic tar demethylation. Linear relations were observed between the molar production of benzene and CH4 and between all quantified tars and C2H4 (ethene). CH4 and C2H4 could thus be analyzed by direct online methods and used as indicators of the tar content and speciation for gasifier monitoring. The validity of these relations depends upon the thermal conditions of reactors and biomass composition. These relations could be suitable for dual-fluidized-bed gasifiers because H2O has very few chemical effects on hydrocarbon thermal conversion.

Lignin could be an important green source for aromatic hydrocarbon production (benzene, toluene and xylenes, BTX). Catalytic hydrodeoxygenation (HDO) of guaiacol was studied over Fe/SiO2 as a model reaction of lignin pyrolysis vapours hydrotreatment. The catalytic conditions were chosen to match with the temperature of never-condensed lignin pyrolysis vapours. The catalyst was characterised by XRD, Mössbauer spectroscopy, N2 sorption and temperature programmed oxidation. A comparison is made with a commercial cobalt-based catalyst. Cobalt-based catalyst shows a too high production of methane. Fe/SiO2 exhibits a good selectivity for BT production. It does not catalyse the aromatic ring hydrogenation. Temperature (623–723K) and space time (0.1–1.5gcath/gGUA) influence the aromatic carbon–oxygen bond hydrogenolysis reaction whereas H2 partial pressure (0.2–0.9bar) has a minor influence. 38% of BT yield was achieved under the best investigated conditions. Reaction mechanisms for guaiacol conversion over Fe/SiO2 are discussed.