Two-step Consecutive Reaction Model Research Articles

Investigating the Phase Transition Kinetics of 1-Octadecanol/Sorbitol Derivative/Expanded Graphite Composite Phase Change Material with Isoconversional and Multivariate Non-Linear Regression Methods.

Organic composite phase change materials (PCMs) have been extensively studied, and it is important to investigate the effect of added components on the phase change process of the organic matrix. Herein, the phase transition process of the composite PCM with 1-octadecanol (OD) as the matrix adsorbed by a network framework composed of 1,3:2,4-di-(3,4-dimethyl) benzylidene sorbitol (DMDBS) and expanded graphite (EG) was measured using differential scanning calorimetry (DSC) at several linear heating rates. Using isoconversional and multivariate non-linear regression methods, a two-step consecutive reaction model for the composite PCM was established, while the apparent activation energies and pre-exponential factors were determined. The reaction mechanism of the first step was altered compared to pure OD, while the activation energies significantly decreased at the initial stage of the phase transition process and increased at the later stage. Combined with microscopic morphology analysis, the main reasons were the size and nanoconfinement effect. The predictions of the composite PCM under various conditions suggested that the composite PCM had a wider available temperature range compared to pure OD. This research provided a new idea for the in-depth study of the phase transition process of organic composite PCMs, which was helpful for the evaluation of organic composite PCMs.

Kinetic study on pyrolysis of waste phenolic fibre-reinforced plastic

Pyrolysis is considered to be a promising method to recycle waste plastics for fuel or chemical feedstock. In order to provide guidance for reactor design and pyrolysis process management for recycling waste phenolic fibre-reinforced plastic (FRP), the pyrolysis behaviors of waste phenolic FRP is studied employing thermogravimetric analysis (TGA) over a wide heating rate range from 10 K/min to 70 K/min in nitrogen. A two-step consecutive reaction model is proposed to characterize the pyrolysis process. A global optimization algorithm called genetic algorithm (GA) coupled with the two-step consecutive reaction model is used to obtain all the kinetic parameters simultaneously based upon the experimental thermogravimetric data at heating rates of 10, 20 and 30 K/min. The predicted MLR and conversion curves using the optimized kinetic parameters and the two-step consecutive reaction model fit well with the experimental results not only at heating rates of 10, 20 and 30 K/min, but also at heating rates of 50, 60 and 70 K/min which are not used to obtain the kinetic parameters. The optimized kinetic parameters and the two-step consecutive reaction model may be applicable to the pyrolysis of waste phenolic FRP under more practical and complex thermal conditions that can be characterized by various heating rates.

Kinetic Modeling of Indian Rice Husk Pyrolysis

Abstract:To efficiently utilize agricultural biomass waste, kinetic modeling of the pyrolysis of rice husk, including both physical (mainly heat transfer) and chemical (reactions) terms, was conducted at different heating rates from (10 to 20 K min−1) to develop a transport model. For chemical kinetics, the parameters were estimated using different kinetic models, namely the single- or parallel-reaction kinetic model with higher orders and the two-step consecutive reaction model. The two-step model could adequately explain the pyrolysis reaction of multiple reactions with different reaction orders i. e., first step is of the first order (m = 1) with respect to the mass of biomass, and the second step is of the second order (n = 2) with respect to the mass of the intermediate to char. The intrinsic kinetics at different heating rates in the absence of oxygen was derived through thermogravimetric analysis. The kinetics of the evolution of non-condensable gases was studied in a self-designed reactor, and an appropriate kinetic model of rice husk biomass pyrolysis that showed excellent agreement with experimental data was established.

Kinetic Modeling of Coal Thermal Decomposition under Air Atmosphere

The paper aims at establishing kinetic model to predict the thermal decomposition of coal in air. Three different rank coals, meager lean coal, fat coal, and gas coal, are investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). By analyzing the experimental TG curves with a model-fitting method, a two separate stages model is presented to describe the mass variation with temperature and the reaction mechanism. The two stages are found to abide by the first-order mechanism and the contracting-sphere mechanism, respectively. The two separate stages model is validated by comparing experimental and simulated conversion curves and TG curves. By analyzing experimental DSC results with an isoconversional method, a two-step consecutive reactions model is developed. Kinetic parameters of each step are ascertained with a multivariate nonlinear regression method. The two-step consecutive reaction model is validated by comparison of experimental and simulated DSC curves. The two separate...

Kinetic studies of two-stage sulphuric acid hydrolysis of sugarcane bagasse

The present paper reports the two-stage hydrolysis of sugarcane bagasse to produce monomer sugars by using dilute and concentrated sulphuric acid. About 88% of the sugars present in bagasse could be recovered with a little formation of toxic compounds such as furfural/HMF. The sugar concentration in the first-stage of hydrolysis was obtained as xylose-rich solution of 49.7 g l−1 using 8% acid concentration at 100 °C and a solid to liquid ratio of 1:4, whereas, with the same solid to liquid ratio of 1:4, 73.4 g l−1 glucose-rich solution was obtained in the second-stage of hydrolysis by using 40% acid concentration at 80 °C. The acid hydrolysis of bagasse could be described by a first-order, two-step consecutive reaction model, where the polysaccharides first decompose into monomers through hydrolysis, and thereafter, decompose into various products in the second step. The proposed kinetic model correlates the experimental data satisfactorily.

DME Dissociation Reaction on Platinum Electrode Surface: A Quantitative Kinetic Analysis by In Situ IR Spectroscopy

The kinetics of electrocatalytic dissociation reaction of dimethyl ether (DME) on a platinum (Pt) polycrystalline electrode in an acidic solution yielding carbon monoxide (CO) has been quantitatively analyzed by in situ IR spectroscopy in the potential region between 100 and 500 mV (vs reversible hydrogen electrode). A two-step consecutive reaction model, an initial dehydrogenation step followed by a CO formation step, is proposed for the dissociation process of the DME molecule. The mechanism of the DME dissociation on the Pt electrode surface is discussed based on the kinetic analysis.

Consecutive Nucleation Events During Divetrification of Zr52.5Cu17.9Ni14.6Al10Ti5 Bulk Metallic Glass

Differential scanning calorimetry, x-ray, and in-situ synchrotron diffraction were used to study the divitrification of Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass. Two consecutive exothermal peaks were identified by differential scanning calorimetry during both isochronal and isothermal scans. Examination of the X-ray and in-situ synchrotron diffraction patterns at various stages of annealing confirms that the exothermal peaks correspond to two nucleation events, with different local atomic structures. Modeling of the calorimetry data indicates that the devitrification in this alloy is adequately described by Johnson CMehl CAvrami theory with a two-step consecutive reaction model.

Consecutive Reaction Model for the Pyrolysis of Corn Cob

Detailed information on the pyrolysis characteristics of corn cob was obtained. A thermogravimetric analysis including determination of kinetic parameters was performed over the temperature range of 373 to 1073 K at controlled heating rates of 10 to 30 K min-1 and with various particle sizes. Under the conditions studied, the heating rate has a significant effect on the pyrolysis process, while the particle size has little effect. A one-step global model and a two-step consecutive-reaction model were developed to simulate this pyrolysis of corn cob and to determine the kinetic parameters. Although various chemicals are released during pyrolysis, global kinetics are looked to as offering a clue to the key mechanistic steps in the overall degradation process. The model predictions are in agreement with the thermal degradation over a wide range of chosen temperatures and particle sizes.

Study on pyrolysis kinetics of walnut shell

Slow pyrolysis of walnut shell which is a cheap and abundantly available solid waste was carried out using thermogravimetric analysis. The effects of raw material heating rate on the pyrolysis properties and kinetic parameters were investigated. A two-step consecutive reaction model were used to simulate the pyrolysis process. The kinetic parameters were established by using the pattern search method. Comparison between experimental data and the model prediction indicated that the two-step consecutive reaction model can better describe the slow pyrolysis of walnut shell as the formation of an intermediate during the pyrolysis process was taken into account.

Two-step Consecutive Reaction Model of Biomass Thermal Decomposition by DSC

The thermal decomposition of one kind of biomass in air has been investigated by differential scanning calorimetry (DSC) analyzer. The results indicate that the heating process of samples from ambient temperature to 923 K at low heating rates shows two obvious exothermic peaks. According to the decomposition mechanism, the first exothermic step is attributed to oxidative degradation of hemicellulose and cellulose, and the second exothermic step is attributed to lignin degradation and char oxidation. The reaction model of the studied biomass thermal decomposition has been studied by iso-conversional methods and optimization computation. The results suggest that the two-step consecutive reaction model is suitable to describe the exotherm of biomass thermal decomposition in air.

Kinetic study on pyrolytic process of oil-palm solid waste using two-step consecutive reaction model

Kinetic study on pyrolytic process of oil-palm solid waste using two-step consecutive reaction model

Kinetic study on pyrolytic process of oil-palm solid waste using two-step consecutive reaction model

Pyrolysis of oil-palm ( Elaeis guineensis Jacq.) shell, a cheap and abundantly available solid waste from palm oil producing process, was carried out using thermogravimetric analysis. The effects of raw material particle size and heating rate on the pyrolytic properties and kinetic parameters (activation energy, frequency factor and reaction order) were investigated. A one-step global model and a two-step consecutive reaction model were used to simulate the pyrolytic process and predict the weight loss during pyrolysis. The two-step model fitted the experimental data much better than the one-step model as the softening effect and formation of an intermediate during the pyrolytic process were taken into account. This two-stage reaction characteristic was confirmed by two obvious maxima in the derivative thermogram for pyrolysis of palm shells under different heating rates. The pyrolytic reactions at the low- and high-temperature regimes were found to be based on a first-order reaction mechanism and a contracting volume mechanism, respectively.

A test of three fitting criteria for multiresponse non‐linear modeling

AbstractThis work evaluates objective functions for multiresponse non‐linear modeling using computer simulations. Tests are performed under a variety of signal‐to‐noise ratios and noise variance–covariance structures. The standard error of prediction for the model parameters, computed from 50 trials, is used for performance comparisons. The full rank and rank‐deficient problems are considered. For the full rank problem one model was investigated, a first‐order two‐step consecutive reaction model, and two objective functions were considered, the total sum of squares and the determinant criterion. No distinction could be made between the two objective functions for this model.For the rank‐deficient case two models were investigated, a first‐order two‐step consecutive reaction as in the full rank case, and a pH titration model described by the Henderson–Hasselbalch equation. Three objective functions were investigated for the rank‐deficient case, the total sum of squares, a weighted total sum of squares and the determinant criterion. The total sum of squares was found to perform poorly under all conditions tested compared to the weighted total sum of squares and the determinant criterion. The determinant criterion was found to perform much better than the other two criteria when the data have a combination of a low signal‐to‐noise ratio and high variance–covariance noise structure.