Centre de Recherche d'Albi en génie des Procédés, des SOlides Divisés, de l'Énergie et de l'Environnement

International audience

Solid char is a product of biomass pyrolysis. It contains a high proportion of carbon, and lower contents of H, O and minerals. This char can have different valorization pathways such as combustion for heat and power, gasification for Syngas production, activation for adsorption applications, or use as a soil amendment. The optimal recovery pathway of the char depends highly on its physical and chemical characteristics. In this study, different chars were prepared from beech wood particles under various pyrolysis operating conditions in an entrained flow reactor (500–1400 °C). Their structural, morphological, surface chemistry properties, as well as their chemical compositions, were determined using different analytical techniques, including elementary analysis, Scanning Electronic Microscopy (SEM) coupled with an energy dispersive X-ray spectrometer (EDX), Fourier Transform Infra-Red spectroscopy (FTIR), and Raman Spectroscopy. The biomass char reactivity was evaluated in air using thermogravimetric analysis (TGA). The yield, chemical composition, surface chemistry, structure, morphology and reactivity of the chars were highly affected by the pyrolysis temperature. In addition, some of these properties related to the char structure and chemical composition were found to be correlated to the char reactivity.

Considering typical spectra of a broad range of carbonaceous materials from gas-shale to nanotubes, various ways by which defects show up in Raman spectra are exampled and discussed. The position, resonance behavior, and linewidth of both the D and G bands are compared, even if in some cases obtaining accurate information on the materials from the fitting parameters is a difficult task. As a matter of fact, even if a full picture is unreachable, defining parameter trends is one acceptable option. Two ways to determine the linewidth, either graphically and or by fitting are proposed in order to be able to compare literature data. The relationship between the crystallite size obtained from the linewidth and from X-ray diffraction, which is complementary to the Tuinstra and Koenig law, is examined. We show that a single approach is not possible unless modeling is performed and therefore that analysis of Raman spectra should be adapted to the specificities of each sample series, i.e., a minimum of knowledge about the materials is always required.

Pyrolysis/gasification-based waste-to-energy (WtE) techniques, comprising partial oxidation of waste and subsequent syngas combustion, show potential benefits over direct incineration. To facilitate their development under the specific conditions of China, pyrolysis and gasification of typical municipal solid waste (MSW) are investigated in a fluidized bed reactor. The effect of the equivalence ratio (ER), reaction temperature, and moisture content on MSW conversion is studied. A rising ER increases the syngas yield but decreases the syngas heating value. The combustible gas yield is strengthened at lower ERs and later drops when the ER exceeds 0.4 as a result of the continuously enhanced oxidation reactions. A higher temperature favors pyrolysis reactions but causes an evident decrease in the syngas heating value during gasification. When the ER is at 0.4 and the temperature is at 650 °C, an optimum operating performance is obtained under the specific input simulated MSW (S-MSW) and test conditions, with an energy conversion efficiency of 68.5%. Under such a circumstance, the further increase of the MSW moisture content is effective for stimulating H 2 production; nevertheless, the quality of syngas degrades, and the energy conversion efficiency declines. The appropriate MSW moisture content is found to be lower than 20–25%. Besides, emiessions, such as heavy metals and dioxins, are also compared to conventional incineration to verify the environmental feasibility of gasification.

Gasification provides a mechanism to convert solids, such as biomass, coal, or waste, into fuels that can be easily integrated into current infrastructure. This paper discusses the use of residual char from a biomass gasifier as a catalyst for tar decomposition and presents an investigation of the catalytic properties of the char. Poplar wood was gasified in a fluidized bed reactor at temperatures ranging from 550 to 920 °C in reaction environments of 90% steam/10% N 2 and 90% N 2 /10% CO 2 . The properties of the char recovered from the process were analyzed, and the catalytic performance for hydrocarbon cracking reactions was tested. Brunauer–Emmett–Teller (BET) measurements showed that the surface area of the char was higher than conventional catalyst carriers. The surface area, which ranged from 429 to 687 m 2 g –1, increased with temperature and reaction time. The catalytic activity of the char was demonstrated through testing the catalytic decomposition of methane and propane to produce H 2 and solid carbon. Higher char surface area resulted in increased performance, but pore size distribution also affected the activity of the catalyst, and evidence of diffusion limitations in microporous char was observed. Clusters of iron were present on the surface of the char. After being used for catalytic applications, carbon deposition was observed on the iron cluster and on the pores of the char, indicating that these sites may influence the reaction. When the char was heated to 800 °C in an inert (N 2 ), atmosphere mass loss was observed, which varied based on the type of char and the time. ESEM/EDX showed that when char was heated to 1000 °C under N 2, oxygen and metals migrated to the surface of the char, which may impact its catalytic activity. Through investigating the properties and performance of biomass gasification char, this paper demonstrates its potential to replace expensive tar decomposition catalysts with char catalysts, which are continuously produced on-site in the gasification process.

Solar thermal energy storage is used in many applications, from building to concentrating solar power plants and industry. The temperature levels encountered range from ambient temperature to more than 1000 °C, and operating times range from a few hours to several months. This paper reviews different types of solar thermal energy storage (sensible heat, latent heat, and thermochemical storage) for low- (40–120 °C) and medium-to-high-temperature (120–1000 °C) applications.

Preparing sustainable and highly efficient biomass-based carbon materials (BBPM) as adsorbents remains a challenge for organic pollutant management. In this work, novel biobased carbon material has been synthesized via facile, sustainable, and different single-step pyrolysis chemical methods (KOH, ZnCl2, ZnSO4, and MgCl2) using a Norway spruce bark as suitable and efficient carbon precursor. The effects of each chemical activator on the physicochemical structure of synthesized were thoroughly investigated as well as its performance on the acetaminophen adsorption. The results showed that the use of different chemical activation provoked remarkable differences in the BBPM physicochemical characteristics. The KOH activation generated material with the highest specific surface area (2209 m2 g−1), followed by ZnCl2 (1019 m2 g−1), ZnSO4 (446 m2 g−1), and MgCl2 (98 m2 g−1). The chemical characterization of the carbon materials indicated that the activation of MgCl2 yielded a material around three times more hydrophobic when compared with the other activation methods. The acetaminophen removal showed to be ultrafast, not only due to the BBPM’s microstructure but also to the abundant active sites provided by the different chemical activation methods. The adsorption equilibrium times were reached at 1 min for BBPM-KOH and BBPM-MgCl2 and 15 min for BBPM-ZnSO4 and BBPM-ZnCl2. The adsorption process suggests that the pore-filling mechanism mainly dominates the acetaminophen removal but also some physical-chemical interactions such as hydrogen bonding between the amide group of acetaminophen and oxygenated or nitrogenated groups of biochar, π-π interactions between the aromatic ring of the pharmaceutical and the aromatics of biochar, n-π interaction, van der Waals interactions. The BBPM regeneration studies showed very good cyclability; in the 3rd cycle, the removal was approximately 70% for all four samples. The samples were also used to treat two synthetic effluents, which attained a removal percentage up to 91.9%.

As one of several types of pollutants in water, chlorinated compounds have been routinely subjected to sonochemical analysis to check the environmental applications of this technology. In this review, an extensive study of the influence of the initial concentration, ultrasonic intensity and frequency on the kinetics, degradation efficiency and mechanism has been analyzed. The sonochemical degradation follows a radical mechanism which yields a very wide range of chlorinated compounds in very low concentrations. Special attention has been paid to the mass balance comparing the results from several analytical techniques. As a conclusion, sonochemical degradation alone is not an efficient treatment to reduce the organic pollutant level in waste water.

Heavy metal emission is a great environmental concern for the development of municipal solid waste (MSW) thermal treatment techniques. In this study, both experimental investigations and theoretical simulations are carried out to identify the partitioning of heavy metals between the gaseous phase and solid fractions during pyrolysis, gasification, and incineration of simulated MSW. Two types of incinerators are used. A tubular furnace is applied to evaluate the evaporation of metals from residues, whereas the metal distribution among bottom ash, cyclone fly ash, and filter fly ash is further examined in a fluidized bed. Six target metals (Cd, Pb, Zn, Cu, Cr, and Ni) are studied. Results show that a reductive atmosphere favors the evaporation of Cd and Zn but refrains Cu, Ni, and Cr volatilization, because metals are mainly reduced to their elemental form or sulfide, according to thermodynamic equilibrium calculation. Oxides are the dominant species under oxidizing condition due to the abundance of alkalis. Pb behaved differently, most probably by forming stable metal-matrix compounds such as Pb 3 Ca 2 Si 3 O 11 and PbZnSiO 4 . The cyclone ash is then separated into different sizes. The metal concentrations recorded reveal that most of the vaporized metals are transferred to the cyclone at its working temperature of 350–600 °C by an evaporation and condensation process; however, entrainment is also a determining factor for the transfer of less-volatile metals. Overall, parameters determining the transfer of heavy metals during MSW thermal treatment can be summarized as (i) metal speciation affected by redox atmosphere, temperature, and the presence of alkalis, chloride, sulfur, and other mineral substances; (ii) system characteristics, such as furnace type and cyclone temperature; and (iii) mechanical entrainment of particles caused by gas velocity.

Support effects in heterogeneous catalysis are evolving as an important field of investigation to optimize catalyst properties. The cobalt-based Fischer–Tropsch (FT) catalysts usually consist of metallic cobalt nanocrystallites dispersed on a support material. The present review surveys the progress that has been made over the last couple of decades in the area of the effect of the support and its surface modifications in cobalt-based FT synthesis. Different catalyst supports such as alumina, silica, titania, niobia, zirconia, zeolite, ceria, carbon-based materials, silicon carbide, aluminum phosphate, hydrotalcite, metal–organic frameworks, and metal foams are discussed and compared with classical supports like alumina or silica wherever permitted. Properties such as metal–support interactions, the support-induced size and morphology of the cobalt nanocrystallites (textural properties of the support), changes in the electronic properties of the cobalt clusters, and the acid/base nature of the support are examined, and wherever possible the activity and/or selectivity in FT synthesis is discussed. This review also summarizes findings on new and promising supports for FT catalysts. Guidance for support modifications and choice of the support as functions of the product selectivity in the FT process is also proposed.

Algae pyrolytic bio-oil contains a large quantity of N-containing components (NCCs), which can be processed as valuable chemicals, while the harmful gases can also be released during bio-oil upgrading. However, the characteristics of NCCs in the bio-oil, especially the composition of heavy NCCs (molecular weight ≥200 Da), have not been fully studied due to the limitation of advanced analytical methods. In this study, three kinds of algae rich in lipids, proteins, and carbohydrates were rapidly pyrolyzed (10–25 °C/s) at different temperatures (300–700 °C). The bio-oil was analyzed using a Fourier transform ion cyclotron resonance mass spectrometer equipped with electrospray ionization, and the characteristics and evolution of nitrogen in heavy components were first obtained. The results indicated that the molecular weight of most heavy NCCs was distributed in the 200–400 Da range. N 1–3 compounds account for over 60% in lipid and protein-rich samples, while N 0 and N 4 components are prominent in carbohydrate-rich samples. As temperature increases, most NCCs become more aromatic and contain less O due to the strong Maillard and deoxygenation reactions. Moreover, the heavier NCCs were promoted to form lighter compounds with more nitrogen atoms through decomposition (mainly denitrogenation and deoxygenation). Finally, some strategies to deal with the NCCs for high-quality bio-oil production were proposed.

A series of isoniazid derivatives bearing a phenolic or heteroaromatic coupled frame were obtained by mechanochemical means. Their pH stability and their structural (conformer/isomer) analysis were checked. The activity of prepared derivatives against Mycobacterium tuberculosis cell growth was evaluated. Some compounds such as phenolic hydrazine 1a and almost all heteroaromatic ones, especially 2, 5 and 7, are more active than isoniazid, and their activity against some M. tuberculosis MDR clinical isolates was determined. Compounds 1a and 7 present a selectivity index >1400 evaluated on MRC5 human fibroblast cells. The mechanism of action of selected hydrazones was demonstrated to block mycolic acid synthesis due to InhA inhibition inside the mycobacterial cell.

Bio-oils obtained from hydrothermal liquefaction of biomass are black viscous fuels with good heating values. This paper presents results of physical and chemical characterization of bio-oils produced by hydrothermal liquefaction of blackcurrant pomace. The oils are analyzed with standard normalized tests and compared to specifications required by commercialized biofuels and conventional fuels. Iodine value and total acid number are determined, showing relatively high values. GC/MS analysis demonstrates that bio-oil recovery by solvent extraction followed by subsequent evaporation of the solvent leads to the loss of some volatile compounds in the bio-oil. Thermogravimetric analysis are performed to study the volatility of HTL bio-oils, as well as to evaluate the carbon residue after evaporation. The viscosity of a bio-oil recovered by ethyl-acetate extraction was measured with a rotational viscometer at 25 °C, leading to a viscosity of 1.7 Pa·s. The results show furthermore that adding sodium hydroxide to the reaction medium has a limited influence on the properties of bio-oils. The choice of extraction solvent has conversely a significant influence on the quality of the produced oil. We demonstrate in this paper how standardized tests can be applied to hydrothermal bio-oils, to compare them with commercial fuels and evaluate the need for upgrading.

For the last 40 years, praziquantel has been the standard treatment for schistosomiasis, a neglected parasitic disease affecting more than 250 million people worldwide. However, there is no suitable paediatric formulation on the market, leading to off-label use and the splitting of commercial tablets for adults. In this study, we use a recently available technology, direct powder extrusion (DPE) three-dimensional printing (3DP), to prepare paediatric Printlets™ (3D printed tablets) of amorphous solid dispersions of praziquantel with Kollidon® VA 64 and surfactants (Span™ 20 or Kolliphor® SLS). Printlets were successfully printed from both pellets and powders obtained from extrudates by hot melt extrusion (HME). In vitro dissolution studies showed a greater than four-fold increase in praziquantel release, due to the formation of amorphous solid dispersions. In vitro palatability data indicated that the printlets were in the range of praziquantel tolerability, highlighting the taste masking capabilities of this technology without the need for additional taste masking excipients. This work has demonstrated the possibility of 3D printing tablets using pellets or powder forms obtained by HME, avoiding the use of filaments in fused deposition modelling 3DP. Moreover, the main formulation hurdles of praziquantel, such as low drug solubility, inadequate taste, and high and variable dose requirements, can be overcome using this technology.

In this work, Norway spruce bark was used as a precursor to prepare activated biochars (BCs) via chemical activation with potassium hydroxide (KOH) as a chemical activator. A Box–Behnken design (BBD) was conducted to evaluate and identify the optimal conditions to reach high specific surface area and high mass yield of BC samples. The studied BC preparation parameters and their levels were as follows: pyrolysis temperature (700, 800, and 900 °C), holding time (1, 2, and 3 h), and ratio of the biomass: chemical activator of 1: 1, 1.5, and 2. The planned BBD yielded BC with extremely high SSA values, up to 2209 m2·g−1. In addition, the BCs were physiochemically characterized, and the results indicated that the BCs exhibited disordered carbon structures and presented a high quantity of O-bearing functional groups on their surfaces, which might improve their adsorption performance towards organic pollutant removal. The BC with the highest SSA value was then employed as an adsorbent to remove Evans blue dye (EB) and colorful effluents. The kinetic study followed a general-order (GO) model, as the most suitable model to describe the experimental data, while the Redlich–Peterson model fitted the equilibrium data better. The EB adsorption capacity was 396.1 mg·g−1. The employment of the BC in the treatment of synthetic effluents, with several dyes and other organic and inorganic compounds, returned a high percentage of removal degree up to 87.7%. Desorption and cyclability tests showed that the biochar can be efficiently regenerated, maintaining an adsorption capacity of 75% after 4 adsorption–desorption cycles. The results of this work pointed out that Norway spruce bark indeed is a promising precursor for producing biochars with very promising properties.

Tri-reforming of methane (TRM) allows the production of syngas with a low environmental impact, an optimal energetic consumption, and a modular H2/CO molar ratio. However, despite a large number of publications devoted to TRM reaction, this process is still in its infancy and faces technical issues due to the catalyst deactivation by the formation of solid carbon, thermal sintering, vapor-solid reactions, and poisoning. Moreover, TRM reaction is also highly dependent on the operational conditions. This article provides a critical analysis of the last achievements on the TRM reaction. First, the thermodynamic, kinetic and mechanism aspects are presented and commented. Then, the impact of the operational conditions is analyzed. Finally, the main reasons of catalyst deactivation and the associated methods for catalyst regeneration are discussed. In parallel, catalytic efficiency is tentatively linked to physico-chemical properties of the catalyst, and recommendations are proposed for the future work on TRM process.

Abstract Processes involving particles, are known to exhibit extremely unpredictable behaviour, mainly due to the mesoscopic nature of granular media. Understanding particulate processes, not only for intellectual satisfaction, but also for process design and operation, basically requires a systems approach in modelling. Because they combine simplicity and flexibility, the stochastic models based on the Markov chain theory are very valuable mathematical tools to this respect. However, they are still largely ignored by the whole core of chemical engineering researchers. This motivates the existence of this review paper, in which we examine the three traditional issues: mixing and transport, separation and transformation.

Abstract This paper discusses the effects of ultrasound on the production of particles by precipitation and crystallization. Examples are given from the formation of crystals of BaSO 4 , K 2 SO 4 , TiO 2 and sucrose. It is shown that ultrasound reduces the induction time, narrows the width of the metastable zone and leads to the production of more, finer, and more uniform crystals in some cases. The reasons for these effects of ultrasound on the nucleation of crystals are discussed and a possible mechanism is presented.

Efavirenz (EFV), a first-line anti-HIV drug largely used as part of antiretroviral therapies, is practically insoluble in water and belongs to BCS class II (low solubility/high permeability). The aim of this study was to improve the solubility and dissolution performances of EFV by formulating an amorphous solid dispersion of the drug in polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer (Soluplus®) using spray-drying technique. To this purpose, spray-dried dispersions of EFV in Soluplus® at different mass ratios (1:1.25, 1:7, 1:10) were prepared and characterized using particle size measurements, SEM, XRD, DSC, FTIR and Raman microscopy mapping. Solubility and dissolution were determined in different media. Stability was studied at accelerated conditions (40 °C/75% RH) and ambient conditions for 12 months. DSC and XRD analyses confirmed the EFV amorphous state. FTIR spectroscopy analyses revealed possible drug–polymer molecular interaction. Solubility and dissolution rate of EFV was enhanced remarkably in the developed spray-dried solid dispersions, as a function of the polymer concentration. Spray-drying was concluded to be a proper technique to formulate a physically stable dispersion of amorphous EFV in Soluplus®, when protected from moisture.

The growth or dissolution of small gas bubbles (R0<15 microm) by rectified diffusion in nearly saturated liquids, subject to low frequencies (20 kHz<f<100 kHz) and high driving acoustic fields (1 bar<p<5 bars), is investigated theoretically. It is shown that, in such conditions, the rectified diffusion threshold radius merges with the Blake threshold radius, which means that a growing bubble is also an inertially oscillating bubble. On the assumption that such a bubble keeps its integrity up to the shape instability threshold predicted by single-bubble theory, a numerical estimation and a fully analytical approximation of its growth rate are derived. On the one hand, the merging of the two thresholds raises the problem of the construction and self-sustainment of acoustic cavitation fields. On the other hand, the lifetime of the growing inertial bubbles calculated within the present theory is found to be much shorter than the time necessary to rectify argon. This allows an alternative interpretation of the absence of single-bubble sonoluminescence emission in multibubble fields, without resorting to the conventional picture of shape instabilities caused by the presence of other bubbles.