Thermal degradation studies and kinetic modeling of cardoon (Cynara cardunculus) pyrolysis using thermogravimetric analysis (TGA)

A key element in the design of sustainable pyrolysis processes is the thermal degradation kinetics of biomass. In this work, pyrolysis tests for cardoon (Cynara carduculus) stems and leaves were performed in a non-isothermal thermogravimetric analyzer (TGA) in order to determine the thermal degradation behavior of both stems and leaves. The kinetic parameters of the process were evaluated using three different kinetic models, the independent parallel reaction model, KAS and OFW iso-conversional model. Good agreement with the experimental TGA data was observed for all models, the best being with the independent parallel reaction model. A variance in the activation energy with conversion was observed when the KAS and OFW models were employed, which reveals that the pyrolysis of cardoon progresses through more complex and multi-step kinetics.     

A sequential method to analyze the kinetics of biomass pyrolysis

The kinetics of biomass pyrolysis was studied via a sequential method including two stages. Stage one is to analyze the kinetics of biomass pyrolysis and starts with the determination of unreacted fraction of sample at the maximum reaction rate, (1-α)(m). Stage two provides a way to simulate the reaction rate profile and to verify the appropriateness of kinetic parameters calculated in the previous stage. Filter paper, xylan, and alkali lignin were used as representatives of cellulose, hemicellulose, and lignin whose pyrolysis was analyzed with the assumption of the orders of reaction being 1, 2, and 3, respectively. For most of the biomass pyrolysis, kinetic parameters were properly determined and reaction rate profiles were adequately simulated by regarding the order of reaction as 1. This new method should be applicable to most of the biomass pyrolysis and similar reactions whose (1-α)(m) is acquirable, representative, and reliable.     

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 °C min⁻¹ from room temperature to 750 °C. Gaseous emissions as CO₂, CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 °C) comparatively to wood samples and was finished at 350 °C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 °C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol⁻¹ and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.     

Pyrolysis of biomass by thermal analysis-mass spectrometry (TA-MS)

The kinetic parameters such as pre-exponential factor and activation energy of hemicellulose, cellulose, and lignin were well determined by the linear regressions of selected, sufficient thermogravimetric data, and close to literature values. The pyrolysis of biomass can be divided into four stages. There was only drying in the zeroth stage (<150°C). In the first stage (150-250°C), some light hydrocarbons were produced with the early pyrolysis of biomass. The biomass was mainly pyrolyzed in the second stage (250-500°C) with higher reaction rates than those of other stages. The productions of H(2) and CO(2) in the third stage (>500°C) may be able to be the evidence of self-gasification of char existing at higher temperatures.     

Modelling of pyrolysis of coal-biomass blends using thermogravimetric analysis

The primary objective of this work was to develop an appropriate model to explain the co-pyrolysis behaviour of lignite coal-biomass blends with different proportions using a thermogravimetric analyzer. A new parallel-series kinetic model was proposed to predict the pyrolysis behaviour of biomass over the entire pyrolysis regime, while a kinetic model similar to that of Anthony and Howard [Anthony, D.B., Howard, J.B., 1976. Coal devolatilization and hydrogasification. AIChE Journal 22(4), 625-656] was used for pyrolysis of coal. Analysis of mass loss history of blends showed an absence of synergistic effect between coal and biomass. Co-pyrolysis mass-loss profiles of the blends were predicted using the estimated kinetic parameters of coal and biomass. Excellent agreement was found between the predicted and the experimental results.     

Kinetics of the pyrolytic and hydrothermal decomposition of water hyacinth

The kinetics of water hyacinth decomposition using pyrolysis and hydrothermal treatment was compared. With pyrolysis, initial vaporization occurred at 453 K as determined by thermogravimetric analysis, while initial solubilisation occurred at 433 K with subcritical hydrothermal treatment. The “kinetic triplet” was determined for the ranges of 423-483 K (range I) and 473-553 K (range II) using the Coats-Redfern method for both treatments. The calculated activation energies for ranges I and II were 110 and 116 kJ/mol for conventional pyrolysis and 145 and 90 kJ/mol for hydrothermal treatment. The similar activation energies for the two temperature ranges observed for pyrolysis implied that only hemicellulose decomposition occurred. For hydrothermal treatment, both hemicellulose and cellulose decomposition occurred in temperature range II, in which a notable lower activation energy was observed. This implied hydrothermal treatment was more suitable for conversion lignocellulosic biomass under these conditions.     

Chemical reaction- and particle diffusion-based kinetic modeling of metal biosorption by a Phormidium sp.-dominated cyanobacterial mat

The present study explores the suitability of chemical reaction-based and diffusion-based kinetic models for defining the biosorption of Cu(II), Cd(II) and Pb(II) by Phormidium sp.-dominated mat. The time-course data of metal sorption by the test mat significantly (r² = 0.932-0.999) fitted to the chemical reaction-based models namely pseudo-first-order, -second-order, and the general rate law. However, these models fail to accurately describe the kinetics of metal biosorption due either to prefixed order or unjustifiable change in rate constant and reaction order with varying concentrations of metal and biomass in the solution. The diffusion-based models, namely, the intra-particle diffusion model and the external mass transfer model fitted well to the time-course metal sorption data, thus suggesting involvement of both external and intra-particle diffusion processes in sorption of test metals by mat biomass. However, the Boyd kinetic expression clearly showed that the external mass transfer is the dominant process.     

Impact of Harvest Time and Cultivar on Conversion of Switchgrass to Bio-oils Via Fast Pyrolysis

The study of the effects of harvest time on switchgrass (Panicum virgatum L.) biomass and bioenergy production reported herein encompasses a large study evaluating the harvest of six switchgrass cultivars grown at three northern US locations over 3 years, harvested at upland peak crop (anthesis), post-frost, and post-winter. Delaying harvest of switchgrass until after frost and until after winter has resulted in decreased yields of switchgrass and reduced amounts of minerals in the biomass. This report examines how changes in biomass composition as a result of varying harvest time and other factors affect the distribution of products formed via fast pyrolysis. A subset (50) of the population (n = 864) was analyzed for fast pyrolysis and catalytic pyrolysis (zeolite catalyst) product yields using a pyrolysis-GC/MS system. The subset was used to build calibrations that were successful in predicting the pyrolysis product yield using near-infrared reflectance spectroscopy (NIRS), and partial least squares predictive models were applied to the entire sample set. The pyrolysis product yield was significantly affected by the field trial location, year of harvest, cultivar, and harvest time. Delaying harvest time of the switchgrass crop led to greater production of deoxygenated aromatics improving the efficiency of the catalytic fast pyrolysis and bio-oil quality. The changes in the pyrolysis product yield were related to biomass compositional changes, and key relationships between cell wall polymers, potassium concentration in the biomass, and pyrolysis products were identified. The findings show that the loss of minerals in the biomass as harvest time is delayed combined with the greater proportion in cellulose and lignin in the biomass has significant positive influences on conversion through fast pyrolysis.     

Effect of transition metal ions on the fluorescence and Taq-catalyzed polymerase chain reaction of tricyclic cytidine analogs

We describe a simple method for real-time monitoring of matrix metalloproteinase-9 (MMP-9) collagenolytic activity for native triple helical collagen IV with a surface plasmon resonance (SPR) biosensor. The proteolytic activity of MMP-9 is measured as a decrease in the SPR signal resulting from the cleavage of collagen IV immobilized on the sensor surface. The kinetic parameters of full-length MMP-9 and its catalytic domain—catalytic constant (k_cat), association rate constant (k_a), and dissociation rate constant (k_d)—were estimated by the SPR method. The presence of sodium chloride and a nonionic detergent Brij-35 in a reaction solution led to the lower collagenolytic activity of MMP-9, whereas they suppressed the nonspecific interaction between MMP-9 and a cysteamine-modified chip. The comparison of kinetic parameters between MMP-9 and its catalytic domain revealed that the association constant of MMP-9 is much larger than that of the catalytic domain, suggesting that the interplay among hemopexin-like domain, fibronectin type II repeats motif, and linker region (O-glycosylated domain) plays an important role in recognizing collagen IV.     

Analysis of the lifetime and spatial localization of hydrogen peroxide generated in the cytosol using a reduced kinetic model

Hydrogen peroxide (H₂O₂) acts as a signaling molecule via its reactions with particular cysteine residues of certain proteins. Determining the roles of direct oxidation by H₂O₂ versus disulfide exchange reactions (i.e. relay reactions) between oxidized and reduced proteins of different identities is a current focus. Here, we use kinetic modeling to estimate the spatial and temporal localization of H₂O₂ and its most likely oxidation targets during a sudden increase in H₂O₂ above the basal level in the cytosol. We updated a previous redox kinetic model with recently measured parameters for HeLa cells and used the model to estimate the length and time scales of H₂O₂ diffusion through the cytosol before it is consumed by reaction. These estimates were on the order of one micron and one millisecond, respectively. We found oxidation of peroxiredoxin by H₂O₂ to be the dominant reaction in the network and that the overall concentration of reduced peroxiredoxin is not significantly affected by physiological increases in intracellular H₂O₂ concentration. We used this information to reduce the model from 22 parameters and reactions and 21 species to a single analytical equation with only one dependent variable, i.e. the concentration of H₂O₂, and reproduced results from the complete model. The reduced kinetic model will facilitate future efforts to progress beyond estimates and precisely quantify how reactions and diffusion jointly influence the distribution of H₂O₂ within cells.     

棉花秸秆催化热解特性及动力学的研究

通过热重分析实验观察K2CO3、KOH、KCl、NaCl、MgCl2和ZnCl26种无机催化剂对棉花秸秆热解催化效果的影响。K2CO,、KOH处理过的棉花秆与纯棉花秆相比热解发生在较低的温度范围,而KCl、NaCl、MgCl,和ZnCl2处理过的棉花秆热解发生在较高的温度范围。碱性催化剂K2C03、KOH降低了棉花秸秆的最大质量损失率,而KCl、NaCl、MgCl2和ZnCl2却增大了棉花秸秆的最大质量损失率。应用Ozawa动力学模型得到动力学参数,棉花秸秆在热解主要阶段可由一段一级反应过程描述,升温速率10K／min时活化能值EA的范围是35～66kJ／mol,频率因子自然对数的范围是4～12。     

生物质热裂解生产生物燃料的研究进展

生物质能源是一种绿色的可以替代化石能源的一种可再生的能源。尽管高温分解生物质处于发展阶段,但在目前水平,高温裂解因其可以在氧存在下热分解将生物材料直接转化为固态,液态和气态能源产品而受到广泛关注。本文介绍了生物质的热裂解,包括慢速热裂解、快速热裂解、闪解、催化热裂解等过程,重点讨论了在各种生物质材料的热裂解过程中各种操作参数如温度和生物粒子大小等对生物燃料收率的影响。     

Suicide-Peroxide inactivation of microperoxidase-11: A kinetic study

The kinetics of microperoxidase-11 (MP-11) in the oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H₂O₂. Concentrations of substrates were so selected that: 1) the reaction was first-order in relation to benign substrate, AH and 2) high ratio of suicide substrate to the benign substrate, [H₂O₂]>>[AH]. Validation and reliability of the obtained kinetic equations were evaluated in various nonlinear and linear forms. Fitting of experimental data into the obtained integrated equation showed a close match between the kinetic model and the experimental results. Indeed, a similar mechanism to horseradish peroxidase was found for the suicide-peroxide inactivation of MP-11. Kinetic parameters of inactivation including the intact activity of MP-11, α_i, and the apparent inactivation rate constant, k_i, were obtained as 0.282 ± 0.006 min^{? 1} and 0.497 ± 0.013 min^{? 1} at [H₂O₂] = 1.0 mM, 27°C, phosphate buffer 5.0 mM, pH = 7.0. Results showed that inactivation of microperoxidase as a peroxidase model enzyme can occur even at low concentrations of hydrogen peroxide (0.4 mM).     

Use of autocatalytic kinetics to obtain composition of lignocellulosic materials

Non-isothermal thermogravimetric analysis (TGA) data of biomasses and pulps originating from non-wood and alternatives materials (i.e., Tagasaste or rice straw) have been fitted with refined models, which include autocatalytic kinetics. Data sets were obtained for different experimental conditions, such as variations of heating rate and atmosphere, i.e., inert (pyrolysis) versus oxidative atmosphere (combustion). Besides the access to classical kinetic parameters (pre-exponential factor, activation energy, and reaction order), the improved data analysis enabled the determination of the chemical composition of the samples (cellulose, hemicellulose, extractives, lignin). The latter compared very well with those obtained by conventional methods (chemical analysis, HPLC). Given the reduced environmental impact and rapidness of the method, potential applications for research related to new biomasses and industrial processes can be foreseen.     

Thermogravimetric kinetics of crude glycerol

The pyrolysis of the crude glycerol from a biodiesel production plant was investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy. The main gaseous products are discussed, and the thermogravimetric kinetics derived. There were four distinct phases in the pyrolysis process of the crude glycerol. The presence of water and methanol in the crude glycerol and responsible for the first decomposition phase, were shown to catalyse glycerol decomposition (second phase). Unlike the pure compound, crude glycerol decomposition below 500 K leaves behind a large mass fraction of pyrolysis residues (ca. 15%), which eventually partially eliminate in two phases upon reaching significantly higher temperatures (700 and 970 K, respectively). An improved iterative Coats–Redfern method was used to evaluate non-isothermal kinetic parameters in each phase. The latter were then utilised to model the decomposition behaviour in non-isothermal conditions. The power law model (first order) predicted accurately the main (second) and third phases in the pyrolysis of the crude glycerol. Differences of 10–30 kJ/mol in activation energies between crude and pure glycerol in their main decomposition phase corroborated the catalytic effect of water and methanol in the crude pyrolysis. The 3-D diffusion model more accurately reproduced the fourth (last) phase, whereas the short initial decomposition phase was poorly simulated despite correlation coefficients ca. 0.95–0.96. The kinetics of the 3rd and 4th decomposition phases, attributed to fatty acid methyl esters cracking and pyrolysis tarry residues, were sensitive to the heating rate.     

Determination of aerobic biodegradation kinetics of olive oil mill wastewater

Aerobic biological treatment was conducted for the treatment of high strength olive oil mill wastewater (OMW). Two different approaches were used for kinetic modeling of OMW biodegradation. TOC removal and CO₂–C evolution were monitored in an open and a closed bioreactor systems, respectively. Gompertz, Refractory organics plus first-order (RFO) and Chen–Hashimoto equations were applied to estimate the kinetic parameters by using the data from bioreactors. Furthermore, change in oxidation stage of carbon was monitored and temperature dependency of OMW biodegradation was investigated based on activation energy. At room temperature, 64% of TOC was removed in the open bioreactor while cumulative CO₂–C evolution was 6.32 g L⁻¹ in closed the bioreactor. Higher biodegradation efficiency and kinetic parameters were obtained at 25 °C rather than 10 °C. Gompertz and RFO equations provided better fitting with CO₂–C and TOC data, respectively. Experimental and kinetic estimations indicated that OMW constituted of approximately 30% refractory organics. The comparison of two different modeling approaches showed that kinetic modeling based on CO₂–C provided better correlation with the experimental data. Temperature coefficient indicated that biological degradation of OMW is slightly dependent on temperature.     

Kinetic study of a substrate cycle involving a chemical step: highly amplified determination of phenolic compounds

A kinetic analysis of a substrate cycle in which one of the two steps was substituted by a chemical reaction has been made. The model is illustrated by the amplified determination, in a continuous assay, of phenolic compounds at low concentrations using the enzyme tyrosinase and β-NADH to reduce the o-quinone product of catalytic activity. Progress curves corresponding to β-NADH disappearance were not linear and followed first-order kinetics. Knowledge of the kinetics of the reaction has allowed us to achieve detection limits as low as 50 nM in a simple 10-min assay. There is no analytical solution to the non-linear differential equation system that describes the kinetics of the reaction, therefore, computer simulations of its dynamic behaviour are also presented, good agreement with the experimental results being obtained. The method is applicable to the measurement of any other metabolite, and its amplification capacity as well as the simplicity of determining kinetic parameters enable it to be implemented in a bioreactor for automation purposes.     

Characteristics of rice husk gasification in an entrained flow reactor

Experiments were performed in an entrained flow reactor to better understand the characteristics of biomass gasification. Rice husk was used in this study. Effects of the gasification temperature (700, 800, 900 and 1000 °C) and the equivalence ratio in the range of 0.220.34 on the biomass gasification and the axial gas distribution in the reactor were studied. The results showed that reactions of CnHm were less important in the gasification process except cracking reactions which occurred at higher temperature. In the oxidization zone, reactions between char and oxygen had a more prevailing role. The optimal gasification temperature of the rice husk could be above 900 °C, and the optimal value of ER was 0.25. The gasification process was finished in 1.42 s when the gasification temperature was above 800 °C. A first order kinetic model was developed for describing rice husk air gasification characteristics and the relevant kinetic parameters were determined.     

Esterification of acidified oil with methanol by SPES/PES catalytic membrane

A sulfonated polyethersulfone (SPES)/polyethersulfone (PES) blend catalytic membrane was prepared and used as a heterogeneous catalyst in the esterification of the acidified oil (acid value 153 mg KOH/g) with methanol for producing biodiesel. The results showed that the free fatty acids conversion reached 97.6% using SPES/PES catalytic membrane under the optimal esterification conditions. Meanwhile, the SPES/PES membrane with 20.3% degree of sulfonation showed a good catalytic stability. A pseudo-homogeneous kinetic model was established. The results indicated that the reaction rate constant increased with increasing methanol/acidified oil molar ratio, the loading of catalytic membrane and reaction temperature. The reaction order was 2 and the activation energy decreased from 74.65 to 21.07 kJ/mol with increasing catalytic membrane loading from 0 to 0.135 meq/g(oil). It implies that the esterification is not diffusively controlled but kinetically controlled. The predicted results were in good agreement with the experimental data.     

Kinetic analysis of simultaneously occurring proton-sorbose symport and passive sorbose transport in Saccharomyces fragilis

Sorbose transport in Saccharomyces fragilis takes place both via an active sugar-H⁺ symport system and via facilitated diffusion.To establish whether the two modes of transport proceed via the same transporter or via two different carriers, the kinetic consequences of both models were investigated. The kinetic equations for initial transport were derived for three possible reaction sequences with respect to sugar and H⁺ binding to the symport carrier: random binding and obligatory ordered binding with either sugar or H⁺ binding first, yielding six sets of kinetic parameters.Analysis of experimental data of sorbose transport in S. fragilis showed the existence of separate carriers for active, sorbose-H⁺ symport and facilitated diffusion. Furthermore, it could be concluded that the symport carrier shows random binding of sugar and H⁺.In recent literature, a similar combination of active and passive sugar transport in Rhodotorula gracilis and Chlorella vulgaris was interpreted as two modes of action of the same carrier, viz., active symport via the protonated, and facilitated diffusion via the unprotonated carrier. Analysis of the experimental data according to the criteria presented in this paper showed, however, that this supposition is untenable and that two different carriers must also be involved in these micro-organisms.