Comparative study on pyrolysis characteristics and kinetics of oleaginous yeast and algae

The pyrolysis processes of oleaginous yeast and algae were studied and compared using a non-isothermal thermogravimetric analyzer at heating rates of 10–50 °C/min, and the most probable mechanism function and kinetic analyses of the main stage of pyrolysis were carried out by the Popuse method, Starink method, and Fridemen method. The main pyrolysis stage of the samples could be described by the Jander equation and Z–L–T equation and the activation energy of the three biomass was 108–117, 107–121 and 93–108 kJ/mol, respectively. For the three kinds of biomass, the DTG curves were divided based on the four pseudo-components by performing Gaussian fitting which are carbohydrates, proteins, lipids, others, and the weight coefficients of them could be identified. The activation energy of each pseudo-component was obtained in the range of 58.36–140.44 kJ/mol by the Kissinger method. The four-pseudo-component model based on Gaussian fitting provides effective data for the design of oleaginous yeast and algae thermal decomposition systems and the kinetic analysis of the pyrolysis process.     

The evaluation of Ni–Co/Al2O3 via olive pomace pyrolysis to generate hydrogen-rich gas: Experimental and kinetic study

The aim of this study is to evaluate olive pomace (OP) as a fuel potential and to examine the effect of Ni–Co/Al₂O₃ catalyst on the pyrolysis of OP by experimental and thermogravimetric analysis (TGA). Pyrolysis studies and kinetic studies were performed in a fixed-bed reactor and a TG analyzer, respectively. The kinetic study was compared with the Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods and their thermodynamic properties were determined. The average activation energy of the OP and OP-20% catalyst was found to be 142.59 and 132.83 kJ/mol, respectively. In addition, the H₂ yield increased from 1.76 mol H₂/kg biomass to 6.08 mol H₂/kg biomass in the presence of 20 wt% catalyst. Based on the results obtained, the pyrolysis of OP can be considered as a suitable alternative for biofuel production.     

Physicochemical structure characteristics and intrinsic reactivity of demineralized coal char rapidly pyrolyzed at elevated pressure

This study aims to investigate the effect of pyrolysis pressure on the physical and chemical structure characteristics and reactivity of subbituminous demineralized coal char. The pyrolysis experiments were studied under different pressures using a pressurized drop tube reactor (PDTR). Structural properties of coal chars were investigated by the application of scanning electron microscopy (SEM), nitrogen adsorption analyzer, automatic mercury porosimeter, and Raman spectroscopy, respectively. The Random Pore Model was used to determine kinetic parameters and intrinsic reactivity of chars. The specific pore volume of chars pyrolyzed at 900–1000 °C increased first and then decreased with pyrolysis pressure increasing, and the maximum value of the specific pore volume of chars occurred at 1.0 MPa. The degree of graphitization of chars deepened with the increase of temperature or pressure. Intrinsic activation energy of char-O₂ was within the range of 126–134 kJ/mol. The intrinsic reactivity of char-O₂ reaction showed strong correlation the Raman parameters with the change of pyrolysis conditions, and it suggested that the intrinsic reactivity of char-O₂ reaction was mainly affected by aromatic ring structures rather than pore structures.     

A modified temperature integral approximation formula and its application in pyrolysis kinetic parameters of waste tire

A modified temperature integral approximation formula was proposed to calculate the kinetic parameters of tire pyrolysis. The relative error percentage of our formula was less than 0.02% at the range of 5 ≤ u ≤ 80. In order to validate our formula, the kinetic parameters of waste tire pyrolysis in a Thermogravimetric Analyzer (TG) were calculated according to different temperature integral approximation formula. The results demonstrated that the coefficient of the experimental TG and simulated TG from our formula was higher than that from Coats-Redfern method. The active energies of tire pyrolysis were 33.03 (120–300°C), 72.30 (300–420°C), and 50.83 kJ/mol (420–500°C).     

Modeling the kinetic behavior of the Li-RHC system for energy-hydrogen storage: (I) absorption

The Lithium–Boron Reactive Hydride Composite System (Li-RHC) (2 LiH + MgB₂/2 LiBH₄ + MgH₂) is a high-temperature hydrogen storage material suitable for energy storage applications. Herein, a comprehensive gas-solid kinetic model for hydrogenation is developed. Based on thermodynamic measurements under absorption conditions, the system's enthalpy ΔH and entropy ΔS are determined to amount to −34 ± 2 kJ∙mol H₂⁻¹ and −70 ± 3 J∙K⁻¹∙mol H₂⁻¹, respectively. Based on the thermodynamic behavior assessment, the kinetic measurements' conditions are set in the range between 325 °C and 412 °C, as well as between 15 bar and 50 bar. The kinetic analysis shows that the hydrogenation rate-limiting-step is related to a one-dimensional interface-controlled reaction with a driving-force-corrected apparent activation energy of 146 ± 3 kJ∙mol H₂⁻¹. Applying the kinetic model, the dependence of the reaction rate constant as a function of pressure and temperature is calculated, allowing the design of optimized hydrogen/energy storage vessels via finite element method (FEM) simulations.     

Kinetics of ethanol steam reforming over Ni/Olivine catalyst

Olivine, a natural mineral consisting of different metal oxides (mainly Mg, Si and Fe oxides) was used as a support for nickel catalyst used in steam reforming of ethanol. Catalyst containing different wt% of Ni on olivine were prepared by conventional wet-impregnation method and characterized by BET, XRD, SEM (coupled with EDS) and H₂-TPR. The reaction was carried out in a tubular fixed bed reactor. Among all the catalysts, 5% Ni on olivine catalyst gave highest hydrogen yield as well as ethanol conversion through ethanol steam reforming reaction. The catalyst activity was analyzed by varying three important process parameters (temperature, ethanol to water molar ratio and space-time). The reaction was performed in the temperature range of 450 °C to 550 °C with 1:6 to 1:12 M feed ratio of ethanol to water at a space-time range 7.21–15.87 kg cat h/kmol ethanol. A maximum yield of 4.62 mol of hydrogen per mole of ethanol reacted was obtained at 550 °C with ethanol to steam molar ratio of 1:10 and space-time of 7.94 kg cat h/kmol ethanol with the ethanol conversion level of 97%. CHNS analysis of the spent catalyst was performed to find the coke deposited over the catalyst surface during the reaction. The power law and LHHW type kinetic models were developed. The power law model predicts the activation energy as 29.07 kJ/mol, whereas the LHHW type model gives the activation energy as 27.4 kJ/mol.     

Kinetic,thermodynamic, FT-IR,and primary constitution analysis of Sargassum spp from Mexico: Potential for hydrogen generation

Pyrolyzed sargassum can be processed to produce important chemical products and hydrogen gas (H₂) from its residual fractions. This article reports the results of a study of the kinetics of the thermogravimetric process (TGA) of sargassum using pyrolysis. Pyrolysis was performed in a temperature interval of 25–900 °C in N₂ atmosphere at several heating velocities: 10, 15, 20, 25, 30, 35, and 40 °C/min. Considering a conversion range of 10–90%, the kinetics of this non-isothermal process were evaluated using six models: Friedman, FWO, KAS, Starink, Popescu, and Kissinger. Following this order, the average activation energies for the six methods were 213.92, 203.35, 203.55, 203.81, 206.25, and 178.63 kJ/mol. The sargassum's thermodynamic behavior was determined by four analyses: A, ΔH, ΔG, and ΔS. Observations of the thermal behavior revealed a pyrolytic process that occurred through a multi-stage reaction. Using an algorithm obtained with SciLab software, deconvolution of DTG was performed to compare the results of the proximal and compositional analyses of the sargassum. Results of the kinetic and thermodynamic analyses, the higher heating value (HHV) close to 17 MJ/kg, low ash content of 12.77%, and high volatile matter content, 82.93%, constitute excellent conditions for generating a pyrolytic design based on sargassum as a raw material for generating green hydrogen as a form of bioenergy. According to the results, it is feasible to expect the production of hydrogen from the pyrolysis of sargassum.     

Hydrogen storage characteristics of magnesium impregnated on the porous channels of activated charcoal scaffold

Ball milled (30 h) MgH₂ is impregnated on the pores/grooves of activated charcoal scaffold using a programmed heat treatment at 550 °C under 5 bar pure hydrogen ambient. The result obtained by this approach is better and more consistent than the materials prepared by metal infiltration at 650 °C or vacuum heated samples under 550 °C. The activation energy value (88 kJ/mol) obtained in the case of impregnated catalyst free material is far better than the activation energy value of the unconfined material (149 kJ/mol). The impregnated material can absorb hydrogen almost closer to its actual capacity at ∼1 bar under 170 °C. The low temperature desorption characteristics and ab/desorption behaviors are extensively analyzed and described.     

Influence of reaction conditions on bio-oil production from pyrolysis of construction waste wood

The pyrolysis characteristics of construction waste wood were investigated for conversion into renewable liquid fuels. The activation energy of pyrolysis derived from thermogravimetric analysis increased gradually with temperature, from 149.41 kJ/mol to 590.22 kJ/mol, as the decomposition of cellulose and hemicellulose was completed and only lignin remained to be decomposed slowly. The yield and properties of pyrolysis oil were studied using two types of reactors, a batch reactor and a fluidized-bed reactor, for a temperature range of 400–550 °C. While both reactors revealed the maximum oil yield at 500 °C, the fluidized-bed reactor consistently gave larger and less temperature-dependent oil yields than the batch reactor. This type of reactor also reduced the moisture content of the oil and improved the oil quality by minimizing the secondary condensation and dehydration. The oil from the fluidized-bed reactor resulted in a larger phenolic content than from the batch reactor, indicating more effective decomposition of lignin. The catalytic pyrolysis over HZSM-5 in the batch reactor increased the proportion of light phenolics and aromatics, which was helpful in upgrading the oil quality.     

Kinetic improvement of H2 absorption and desorption properties in Mg/MgH2 by using niobium ethoxide as additive

The hydrogen absorption and desorption properties of a MgH₂ – 1 mol.% Nb(V) ethoxide mixture are reported. The material was prepared by hand mixing the additive with previously ball-milled MgH₂. Nb ethoxide reacts with MgH₂ during heating, releasing C₂H₆ and H₂, and producing MgO and Nb or Nb hydride. Hydriding and dehydriding are greatly enhanced by the use of the alkoxide. At 250 °C the material with Nb takes up 1.8 wt% in 30 s compared with 0.1 wt% of pure Mg, and releases 4.2 wt% in 30 min, whereas MgH₂ without Nb does not appreciably desorb hydrogen. The absorption and desorption activation energies are reduced from 153 kJ/mol H₂ to 94 kJ/mol H₂, and from 176 kJ/mol H₂ to 75 kJ/mol H₂, respectively. The hydrogen sorption properties remain stable after 10 cycles at 300 °C. The kinetic improvement is attributed to the fine distribution of amorphous/nanometric NbH_x achieved by the dispersion of the liquid additive.     

Co-pyrolysis of lignin and polyethylene with the addition of transition metals - Part I: Thermal behavior and kinetics analysis

In order to realize a promissing disposal of solid wastes, especially for biomass and plastics, and the recovery of high value-added products, lignin (LG) and polyethylene (PE) were co-pyrolyzed with the addition of transition metals. Thermal behavior and kinetics of the mixtures affected by the type of transition metals (0.5 mmol/g Ni, Co, Fe and Mn), the concentration of Ni (0–1 mmol/g Ni), the ratio of LG to PE (4:1-1:4) and heating rate (10–40 °C/min) were investigated according to thermogravimetric analysis (TGA). It is found that the treatment of LG/PE with 0.5 mmol/g Ni, Co, Fe or Mn results in the decrease of the initial decomposition temperature of LG and PE in the mixture by 10–53 °C and 9–18 °C, respectively. According to the difference of weight loss (ΔW), the introduction of Fe and Mn has slight influences on the interaction between LG and PE while a negative effect of PE on the devolatilization of LG in LG/PE can be largely diminished with the involvement of Ni and Co. Kinetic analysis reveals that the pyrolysis of LG and PE can be well fitted by a single first order model reaction while two consecutive first order model reactions are needed to exactly describe the co-pyrolysis of LG/PE with or without transition metals. The E value of LG and PE in the mixture is reduced by 6.11–21.62 kJ/mol and 7.67–50.11 kJ/mol, respectively, when 0.5 mmol/g Ni, Co, Fe or Mn was involved. Moreover, the concentration of Ni, the ratio of LG to PE and the heating rate play important roles on the thermal behavior and kinetics of the co-pyrolysis of LG/PE.     

TGA and kinetic study of different torrefaction conditions of wood biomass under air and oxy-fuel combustion atmospheres

Combustion and oxy-fuel combustion characteristics of torrefied pine wood chips were investigated by Thermogravimetric Analysis (TGA). Three torrefaction temperatures (250, 300, and 350 °C) and two residence times (15 and 30 min) were considered. Experiments were carried out at three heating rates of 10, 20, and 40 °C/min. The isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate the activation energies. The assessment of uncertainty in obtaining the activation energy values was also considered. The obtained results indicated that due to torrefaction, the O/C and H/C atomic ratios decreased, resulting the 300ºC-30 min and 350ºC-15 min torrefied biomass to be completely embedded in lignite region in van-Krevelen's diagram. Oxy-fuel combustion affected the decomposition of cellulose and lignin components of biomass while the impact on the hemicellulose component was negligible. The kinetic analysis revealed that with the evolution of conversion degree, the activation energy values increased during hemicellulose degradation, remained approximately constant during cellulose decomposition and showed a sharp decrease for lignin decomposition. The activation energy trends were comparable in both air and oxy-fuel combustion conditions, however slight changes in activation energy values were noticed. The highest activation energy value was obtained for 250ºC-30 min torrefied biomass at 183.40 kJ/mol and the lowest value was 72.93 kJ/mol for 350ºC-15 min biomass. The uncertainty values related to FWO method were lower than KAS and Friedman methods. The uncertainty values for FWO and KAS methods were at the range of 5–15%.     

Effect of sintering aids on sintering kinetic behavior of praseodymium doped ceria based electrolyte material for solid oxide cells

The present study investigates the effect of sintering additives (Li, Co, Fe, and Mg) on the sintering kinetic behavior of the praseodymium-doped-ceria (PDC) electrolyte of solid oxide electrolyzer cell. 3Li-PDC, 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets were obtained from the synthesis of PDC nano-powder by microwave-assisted co-precipitation method using isopropyl alcohol as a solvent and followed by sintering additive wetness impregnation method. Linear shrinkage and shrinkage rate data suggest a positive sintering effect for 3Li-PDC and 3Co-PDC pellets and a negative sintering effect for 3 Mg-PDC and 3Fe-PDC pellets than compared to PDC pellets alone. The addition of lithium as a sintering additive (3Li-PDC) had reduced the sintering temperature of PDC from 1100 °C to 850 °C. For PDC, 3Li-PDC, 3Co-PDC, 3Fe-PDC and 3 Mg-PDC pellets sintered at 1100 °C, 850 °C, 1000 °C, 1200 °C, 1100 °C for 2 h resulted in a relative density of 93.6 ± 0.25, 95.8 ± 0.45, 95.0 ± 0.20, 92.7 ± 0.10, and 94.5 ± 0.10%, respectively. The XRD patterns of the sintered PDC pellets suggested a secondary phase formation (PrO₂) in 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets indicating that the addition of these sintering aids results in poor solubility limit of Pr in CeO₂. On the other hand, XRD patterns of PDC and Li-PDC sintered pellets displayed no secondary peak indicating good solid-solution formation. The activation energy of the 3Li-PDC pellet is obtained from CHR and Dorn methods and was found to be 182 kJ/mol and 196 kJ/mol. From the CHR method, for the 3Li-PDC pellet, the initial sintering behavior is by the grain boundary diffusion mechanism (m = ~2).     

Effect of water on the thermal stability of alpha-aluminum hydride

Water can significantly enhance the thermal spontaneous combustion and explosion hazard of alpha-aluminum hydride (α-AlH₃). Thermal analysis suggested that, as the water content increased from 10% to 40%, the total reaction heat was increased by 68.3%. α-AlH₃ with different water contents (10%–40%) underwent hydrolysis reaction and oxidation reaction with the activation energy of 57.9–68.7 kJ/mol and 88.3–107.6 kJ/mol, respectively. As the heating rate increased from 0.2 to 2 °C/min, the onset temperature, the peak temperature, and the maximum heat flow of the exothermic reaction were increased. As the storage temperature increased from 45 to 65 °C, the time to maximum reaction rate decreased from 5.16 to 0.84 h. Combining the results of SEM, XRD, XPS and thermal analysis, the reaction mechanism of α-AlH₃ and water under isothermal and non-isothermal conditions was revealed.     

Hydrogen-rich syngas production by gasification of Urea-formaldehyde plastics in supercritical water

Supercritical water is a promising medium to convert plastics into hydrogen and other recyclable products efficiently. In previous research, supercritical water gasification characteristics investigations focus on thermoplastics instead of thermoset plastics due to its chemical, thermal and mechanical stability. Urea-formaldehyde (UF) plastics were selected as a typical kind of thermoset plastics for investigation in this paper and quartz tubes were used as the reactor in order to avoid the potential catalytic effect of metal reactor wall. Conversion characteristic were studied and the influence of different operating parameters such as temperature, reaction time, feedstock mass fraction and pressure were investigated respectively. The molar fraction of hydrogen could reach about 70% in 700 °C. Products in gas phase and solid phase were analyzed, and properties, chemical structures and inhibition mechanism of thermoset plastics was analyzed after comparing with polystyrene (PS) plastics. The result showed that increase of high temperature and long reaction time could promote gasification process, meanwhile the increase in the feedstock mass fraction would result in suppression of the gasification process. Finally, kinetic study of UF was carried out and the activation energy and pre-exponential factor of the Arrhenius equation were calculated as 30.09 ± 1.62 kJ/mol and 0.1199 ± 0.0049 min⁻¹, respectively.     

Desorption properties of LiAlH4 doped with LaFeO3 catalyst

The addition of a catalyst and ball milling process was found to be one of the efficient method to reduce the decomposition temperature and improve the desorption kinetics of lithium aluminium hydride (LiAlH₄). In this paper, a transition metal oxide, LaFeO₃ was used as a catalyst. Decomposition temperature of the 10 wt% of LaFeO₃-doped LiAlH₄ system was found to be lowered from 143 °C to 103 °C (first step) and from 175 °C to 153 °C (second step), respectively. In isothermal desorption kinetics, the amount of hydrogen released of the doped sample was improved to 3.9 wt% in 2.5 h at 90 °C. Meanwhile, the undoped sample had released less than 1.0 wt% of hydrogen under the same condition. The activation energy of the LaFeO₃-doped LiAlH₄ sample was measured to be 73 kJ/mol and 90 kJ/mol for the first two dehydrogenation reactions compared to 107 kJ/mol and 119 kJ/mol for the undoped sample. The improvements of desorption properties were the results from the formation of LiFeO₂, Fe and La or La-containing phase during the heating process.     

Hydro-catalytic treatment of organoamine boranes for efficient thermal dehydrogenation for hydrogen production

This study aims to present the hydro-catalytic treatment of organoamine boranes for efficient thermal dehydrogenation for hydrogen production. Organoamine boranes, methylamine borane (MeAB), and ethane 1,2 diamine borane (EDAB), known as ammonia borane (AB) carbon derivatives, are synthesized to be used as a solid-state hydrogen storage medium. Thermal dehydrogenation of MeAB and EDAB is performed at 80 °C, 100 °C, and 120 °C under different conditions (self, catalytic, and hydro-catalytic) for hydrogen production and compared with AB. For this purpose, a cobalt-doped activated carbon (Co-AC) catalyst is fabricated. The physicochemical properties of Co-AC catalyst is investigated by well-known techniques such as ATR/FT-IR, XRD, XPS, ICP-MS, BET, and TEM. The synthesized Co-AC catalyst obtained in nano CoOOH structure (20 nm, 12% Co wt) is formed and well-dispersed on the activated carbon support. It has indicated that Co-AC exhibits efficient catalytic activity towards organoamine boranes thermal dehydrogenation. Hydrogen release tests show that hydro-catalytic treatment improves the thermal dehydrogenation kinetics of neat MeAB, EDAB, and AB. Co-AC catalyzed hydro-treatment for thermal dehydrogenation of MeAB and EDAB acceleras the hydrogen release from 0.13 mL H₂/min to 46.12 mL H₂/min, from 0.16 mL H₂/min to 38.06 mL H₂/min, respectively at 80 °C. Moreover, hydro-catalytic treatment significantly lowers the H₂ release barrier of organoamine boranes thermal dehydrogenation, from 110 kJ/mol to 19 kJ/mol for MeAB and 130 kJ/mol to 21 kJ/mol for EDAB. In conclusion, hydro and catalytic treatment presents remarkable synergistic effect in thermal dehydrogenation and improves the hydrogen release kinetics.     

Pyrolysis kinetics of invasive coastal plant Spartina anglica using thermogravimetric analysis

The pyrolysis kinetics of invasive plant Spartina anglica biomass was investigated via a thermogravimetric (TG) analyzer from 50 to 800°C in an inert argon atmosphere at different heating rates of 5–30°C/min, and the kinetic parameters were deduced by Starink and master-plots methods. The results showed that three stages appeared in the thermal degradation process, and the mean value of activation energy was calculated to be 291.57 kJ/mol by the Starink method. It suggested that the most probable pyrolysis kinetic model was g(α) = [?ln(1-α)]⁴ deduced by the master-plots method, which meant a random nucleation and nuclei growth mechanism. These results provided fundamental useful information for describing the pyrolysis process, and the subsequent designing and running of a pyrolytic processing system using S. anglica as feedstock.     

The mechanism and kinetics study of Fischer‒Tropsch reaction over iron-nickel-cerium nano-structure catalyst

The kinetic of Fischer‒Tropsch reaction was investigated using the iron‒nickel‒cerium nano-structure catalyst synthesized by the hydrothermal method in the fixed-bed micro reactor for the first time. The kinetic tests carried out under operating conditions including the pressure of 2–10 bar, temperature of 230–250 °C, molar ratio H₂/CO of 1, and the gas space velocity of 3000 h⁻¹. Twenty-two set of reaction mechanisms were proposed on the basis of the adsorption nature of carbon monoxide, and hydrogen using the Langmuir‒Hinshelwood‒Hougen‒Watson, and Eley Rideal adsorption theories for the FT reaction. The rate equations of CO consumption were obtained based on the proposed reaction mechanisms. The best kinetic model was chosen by non-linear regression analysis and its kinetic parameters including activation energy, adsorption enthalpies of H₂, and CO were estimated 60.4, −3.24, and −65.7 kJ/mol respectively. The nanocatalyst was characterized by various techniques such as XRD, FESEM, and Brunauer–Emmett–Teller surface area measurements.     

Hydrogen generation from sodium borohydride hydrolysis by multi-walled carbon nanotube supported platinum catalyst: A kinetic study

In this study, it is aimed to investigate hydrogen (H₂) generation from sodium borohydride (NaBH₄) hydrolysis by multi-walled carbon nanotube supported platinum catalyst (Pt/MWCNT) under various conditions (0–0.03 g Pt amount catalyst, 2.58–5.03 wt % NaBH₄, and 27–67 °C) in detail. For comparison, carbon supported platinum (Pt/C) commercial catalyst was used for H₂ generation experiments under the same conditions. The reaction rate of the experiments was described by a power law model which depends on the temperature of the reaction and concentrations of NaBH₄. Kinetic studies of both Pt/MWCNT and Pt/C catalysts were done and activation energies, which is the required minimum energy to overcome the energy barrier, were found as 27 kJ/mol and 36 kJ/mol, respectively. Pt/MWCNT catalyst is accelerated the reaction less than Pt/C catalyst while Pt/MWCNT is more efficient than Pt/C catalyst, they are approximately 98% and 95%, respectively. According to the results of experiments and the kinetic study, the reaction system based on NaBH₄ in the presence of Pt/MWCNT catalyst can be a potential hydrogen generation system for portable applications of proton exchange membrane fuel cell (PEMFC).