Investigation of non-isothermal pyrolysis kinetics of waste industrial hemp stem by three-parallel-reaction model

Comprehensive investigation of activator influence on pyrolysis kinetics, thermodynamics, and product characteristics in one-step activated carbon preparation from spirulina

The thermodynamics and kinetics effects of activators on the simultaneous activation pyrolysis of microalgae remain unclear. This study addresses this gap by investigating the effects of activators (KOH, KHCO3, CH3COOK, K2CO3) on Spirulina platensis (SP) pyrolysis using thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR) and isoconversion methods. The results showed that all activators reduced the initial decomposition temperature of SP, leading to the earlier release of volatile pyrolysis products. Kinetics analysis further revealed that the addition of activators lowered the apparent activation energy (Eα) in the initial pyrolysis stage of SP. However, as the devolatilization process transitioned to the charring stage, the Eα gradually increased, surpassing that of SP pyrolyzed alone. Thermodynamic analysis indicated that the carbonization process of microalgae in the presence of activators required higher energy absorption. These findings reveal the mechanisms of activators in microalgae pyrolysis and provide insights into biochar production.

Co-pyrolysis Behavior of Coal and Biomass: Synergistic Effect and Kinetic Analysis

Co-pyrolysis of coal and biomass is an efficient way to utilize resources. This study investigates the co-pyrolysis behavior and kinetics of coal and biomass using thermogravimetric analysis (TGA) and TG-FTIR. Co-pyrolysis of coal and biomass exhibits a synergistic effect. When the biomass is 25%, the weight loss increases, showing a positive synergistic effect. When the biomass is 50%, it exhibits a negative synergistic effect. Increasing the heating rate can promote the generation of a synergistic effect. Co-pyrolysis involves two central pyrolysis stages: stage III (250-380 °C) and stage IV (380-550 °C). Friedman, FWO, KAS, and STA methods are used to calculate the activation energy for stages III and IV. The activation energy (E α) for co-pyrolysis is higher than that for coal or biomass pyrolysis alone. A positive synergistic effect is observed in stage III, while a negative synergistic effect is noted in stage IV. The master curve method determines an accurate reaction order (n) and pre-exponential factor (A) value of Coal75-Bio25. In stage III, E α = 238.81 kJ/mol, n = 2.4, A = 1.30 × 1021 s-1. In stage IV, E α = 37 8.01 kJ/mol, n = 4.0, A = 1.10 × 1027 s-1. The kinetic parameters in stage IV are significantly higher than those in stage III. TG-FTIR is used to analyze the synergistic effect of co-pyrolysis. Compared with coal and biomass pyrolysis separately, the Coal75-Bio25 pyrolysis process releases less CO2 and more CH4. These findings support the synergistic effect of coal and biomass during co-pyrolysis.

Insight into the pyrolysis of bamboo flour, polylactic acid and their composite: Pyrolysis behavior, kinetic triplets, and thermodynamic parameters based on Fraser-Suzuki deconvolution procedure

Kinetic triplets and thermodynamics are important in the design of pyrolysis processing. In this study, the non-isothermal kinetics and thermodynamics of pseudo components of bamboo flour (BF), Polylactic acid (PLA), and the resulting BF/PLA composite were investigated using Fraser-Suzuki deconvolution. Fourier-transform infrared spectra (FTIR) was used to characterize the gaseous products. Results showed the Fraser-Suzuki deconvolution curves fitted well to the experimental data. For pseudo hemicellulose and pseudo components in PLA, common kinetic models were applied. The pyrolysis of pseudo cellulose met the random scission model and pseudo lignin need to be described with empirical model. The Kinetic models were verified and shown to be in good agreement with the experimental results FTIR results indicated that more radical reactions occur in PLA during co-pyrolysis with BF.Thermodynamic results indicated the pyrolysis of pseudo components were non-spontaneous reactions except lignin. These results will contribute to reactor design and scale-up in future.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

Particleboard Creation from Agricultural Waste Residue of Seed Hemp

In this research, agricultural residue of seed hemp variety "Adzelvieši" was used to create hemp particleboard samples. Hemp was grown in three experimental fields where it was observed that after seed harvesting, 3.5 tonnes of hemp stems per hectare remained. The plants were processed with milling, cutting, and sieving equipment. Moisture content and particle size distribution were observed throughout raw material processing. Hemp boards were produced using the cold pressing method with 10% urea formaldehyde resin as the binder. The boards were made as 20 mm thick single-layer parts with a density range of 220 ± 30 kg/m3 and porosity of 86%. Board structural analysis was performed using optical microscopy and scanning electron microscopy methods. Mechanical strength was determined by performing bending strength, internal bond strength, and screw withdrawal tests. The thermal conductivity reached 0.047 ± 0.008 W/(mK). The results were compared with industrially produced hemp shive boards and materials in the developmental or production stage. The feasibility for the experimental production cycle proposed in the study is discussed.

A novel pseudo-multicomponent isoconversional approach for the estimation of kinetic and thermodynamic parameters of potato stalk thermal degradation

This study examined the thermal degradation kinetics of potato stalk (PS) using a unique isoconversional technique. The kinetic analysis was assessed based on mathematical deconvolution approach with model-free method. The thermogravimetric analyzer (TGA) was used for the non-isothermal pyrolysis of PS at different heating rates. The Gaussian function was then used to extract three pseudo-components (PC) from the TGA findings. The average activation energy value for PS (125.99, 122.79, and 122.85 kJ/mol), PC1 (106.78, 103.83, and 103.92 kJ/mol), PC2 (120.26, 116.31, and 116.55 kJ/mol), and PC3 (373.12, 379.40, and 378.93 kJ/mol) based on OFW, KAS, and VZN model respectively. Furthermore, an artificial neural network (ANN) was used to forecast the thermal degradation data. The findings demonstrated a significant correlation between real and anticipated values. The kinetic and thermodynamic results, along with ANN are critical for constructing pyrolysis reactors that might use waste biomass as a potential feedstock for bioenergy production.

Understanding the reaction kinetics of diesel exhaust soot during oxidation process

The purpose of the present study is to better understand the reaction kinetics of diesel exhaust soot during oxidation process. A thermogravimetric analyzer was used to oxidize real diesel exhaust soot generated from a Euro VI diesel engine under non-isothermal conditions. The Friedman-Reich-Levi method and the Sestak-Berggren model were used to determine the oxidation kinetics. Raman spectroscopy and high-resolution transmission electron microscopy were employed to follow the changes of the soot structure during oxidation. The activation energy gradually increased with increasing conversion level during soot oxidation. The oxidation process of diesel exhaust soot could be described as three-step kinetics, and the calculated conversions fitted the experimental results very well. The kinetic predictions of diesel soot oxidation that were obtained using the proposed kinetic models were more accurate and precise than those with the common first-order model. The structural order increased as oxidation progressed, which was responsible for the increased activation energy. The structural ordering was principally caused by the preferential oxidation of the disordered fraction in the diesel soot, especially for the amorphous carbon, which was oxidized in the initial stage of the oxidation reaction.

Predicting Pyrolysis of a Wide Variety of Petroleum Coke Using an Independent Parallel Reaction Model and a Backpropagation Neural Network

In this work, the pyrolysis behavior and gaseous products of petroleum coke were investigated by nonisothermal thermogravimetric analysis (TGA) and thermogravimetry-mass spectrometry (TG-MS). Then, the pyrolysis kinetics of six kinds of petroleum coke (Fushun (FS), Fuyu (FY), Wuhan (WH), Zhenhai (ZH), Qilu (QL), and Shijiazhuang (SJZ)) were determined by an independent parallel reaction (IPR) model, and the kinetic parameters (activation energy and preexponential factor) were obtained. In addition, an efficient backpropagation neural network (BPNN) was developed to predict the thermal data of six kinds of petroleum coke. The BPNN-predicted thermal data were used to calculate the kinetic parameters based on the IPR model, and the results were compared with the ones calculated using experimental data. The results showed that the pyrolysis process of six kinds of petroleum coke was divided into three stages, of which stage II (250-900 °C) had the significant mass loss, corresponding to the devolatilization of petroleum coke. MS fragmented ion intensity analysis indicated that the main pyrolysis products were methane CH _x (m/z = 13, 14, 15, and 16), aliphatic hydrocarbon C₃H₅, H₂, CO, CO₂, and H₂O. The thermal data predicted by the IPR, BPNN, and BPNN-IPR (BPNN combined with IPR) models were in good agreement with the experimental data. Most importantly, it was concluded that the BPNN-predicted data can be further applied to calculate the kinetic parameters using the IPR kinetic model.

Microwave catalytic co-pyrolysis of chlorella vulgaris and oily sludge: Characteristics and bio-oil analysis

Co-pyrolysis of Chlorella vulgaris (CV) and Oily sludge (OS) under different mixing ratios were investigated by microwave furnace. NiO, activated carbon (AC) and their 1:1 compound (N1A1) with different additions (5%, 10%, 15% and 20%) were selected as microwave additives to study the effects on optimum mixing ratio of co-pyrolysis. The results indicated that mixing ratio of CV/OS = 1:1 (C1O1) was optimum for co-pyrolysis. Besides, 10% AC was optimal on improving pyrolysis characteristics of the C1O1 group. The most significant synergistic interaction of NiO and AC occurred in the 10% N1A1 group. Moreover, hydrocarbons in bio-oil of the C1O1 group increased by 31.84% compared with theoretical values, while nitrogenous, oxygenated compounds decreased by 74.18% and 19.01%. Addition of 10% N1A1 in the C1O1 group increased aliphatic hydrocarbons by 22.44%, and decreased nitrogenous, oxygenated compounds by 41.79% and 36.58%. Overall, 10% N1A1 was conducive for the C1O1 group to obtain high-quality bio-oil.

Thermogravimetric pyrolysis kinetics study of tobacco stem via multicomponent kinetic modeling, Asym2sig deconvolution and combined kinetics

Tobacco stems (TS) are tobacco residues produced, whereby the assessment of the pyrolysis kinetics of TS is critical to realize high-value utilization of agricultural residues. Firstly, a thermogravimetric analyzer was employed to perform the non-isothermal pyrolysis of TS at various heating rates. Then, the deconvolution function by Asym2sig showed that the pyrolysis of TS can be accurately modeled for three parallel decomposition fractions. Furthermore, the pyrolysis product was analyzed using fourier transform infrared spectrometer (FTIR). The results showed that the average activation energy evaluated by the isoconversion methods exhibited the highest average activation energy of 191.762 kJ·mol-1 for lignin (LG), followed by 189.268 kJ·mol-1 for cellulose (CL) and then 176.357 kJ·mol-1 for hemicellulose (HC). Based on the experimental results, the pre-exponential factors and reaction models for HC, CL and LG were also calculated and developed separately. From thermodynamic standpoint, raw materials for bioenergy generation can be derived from TS.

Investigation of product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Iron-Nickel/ZSM-5 catalyst

Py-GC/MS and thermogravimetric analysis were carried out to systematically explore product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Fe-Ni/ZSM-5. The results showed that the Fe-Ni/ZSM-5 exhibited an additive effect on the production of monocyclic aromatic hydrocarbons compared to mono-metallic catalysts (Fe/ZSM-5 or Ni/ZSM-5). Fe-Ni/ZSM-5 further increased the yield of toluene (17.28 mg g^-1), which was 41.4% and 80.9% higher than Fe/ZSM-5 and Ni/ZSM-5, respectively. According to the kinetic analysis, the average activation energy obtained from catalytic pyrolysis with Fe-Ni/ZSM-5 using the methods of Friedman, Starink, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose was 156.19, 152.39, 154.30, and 152.11 kJ mol^-1, respectively. Fe-Ni/ZSM-5 addition lowered the activation energy compared to non-catalytic pyrolysis at the conversion rate of 0.15-0.75. The overall catalytic pyrolysis process of poplar sawdust follows the diffusion and nucleation models. The thermodynamic parameters (enthalpy and entropy) showed positive and negative values, respectively, indicating non-spontaneous reactions during the catalytic pyrolysis process.