Industrial Reactor Research Articles

Dynamic modeling and optimization of methanol partial oxidation to formaldehyde over Mo–Fe catalyst in an industrial isothermal reactor

Abstract In this research, a one-dimensional heterogeneous model is developed to simulate the partial oxidation of methanol to formaldehyde over a molybdenum-iron catalyst in an industrial isothermal reactor at dynamic condition. The considered isothermal reactor is modelled based on the mass and energy balance equations considering catalyst deactivation. Based on the simulation results, decline in the catalyst activity from 1.0 to 0.73 decreases the rate of formaldehyde production rate from 94.9 kmol h−1 to 89.63 kmol h−1 during process run time. Subsequently, a multi-objective optimization problem is programmed to enhance formaldehyde productivity and minimize the production decline during process run time. To select the effective decision variables, a sensitivity analysis is performed based on the developed dynamic model. Then, the programmed multi-objective optimization problem is replaced with a single objective by the weighted sum method, and the problem is handled by the genetic algorithm method to determine the optimal trajectory of coolant temperature. The simulation results showed that the average formaldehyde production rate increases from 92.11 kmol h−1 to 95.22 kmol h−1 when the optimal conditions are applied to the reactor.

A Discussion on the Critical Electric Rayleigh Number for AC Electrokinetic Flow of Binary Fluids in a Divergent Microchannel.

Electrokinetic (EK) flow is a type of flow driven or manipulated by electric body forces, influenced by various factors such as electric field intensity, electric field form, frequency, electric permittivity/conductivity, fluid viscosity, etc. The diversity of dimensionless parameters, such as the electric Rayleigh number, complicates the comparison of the EK flow stability. Consequently, comparing the performance and cost of micromixers or reactors based on EK flow is challenging, posing an obstacle to their industrial and engineering applications. In this investigation, we theoretically derived a new electric Rayleigh number (Rae) that quantifies the relationship among electric body forces, fluid viscosity, and ion diffusivity, based on a tanh model of electric conductivity distribution. The calculation results indicate that the new Rae exhibits richer variation with the control parameters and better consistency with previous experimental reports. We further conducted experimental studies on the critical electric Rayleigh number (Raec) of the AC EK flow of binary fluids in a divergent microchannel. The experimental variations align well with the theoretical predictions, particularly the existence of an optimal AC frequency and electric conductivity ratio, demonstrating that the tanh model can better elucidate the underlying physics of EK flow. With the new electric Rayleigh number, we found that EK flow in the designed divergent microchannel has a much smaller Raec than previously reported, indicating that EK flow is more unstable and thus more suitable for applications in micromixers or reactors in industry and engineering.

Advances and Challenges in Speciation Measurement and Microkinetic Modeling for Gas-Solid Heterogeneous Catalysis.

Microkinetic modeling of heterogeneous catalysis serves as an efficient tool bridging atom-scale first-principles calculations and macroscale industrial reactor simulations. Fundamental understanding of the microkinetic mechanism relies on a combination of experimental and theoretical studies. This Perspective presents an overview of the latest progress of experimental and microkinetic modeling approaches applied to gas-solid catalytic kinetics. Then, opportunities and challenges are presented based on recent research progress in gas-solid catalysis and combustion chemistry. For experimental approaches, the importance of ideal catalytic reactors, structured catalysts, and precise elementary rate measurements is emphasized. Additionally, integrating spatiotemporally resolved operando gas-phase diagnostics with surface-adsorbed species characterization methods offers new opportunities for gaining deeper insights into gas-surface reactions. In microkinetic modeling, a hybrid rate parameter evaluation approach that combines first-principles calculations with semiempirical methods, followed by automated mechanism generation and data-driven optimization, opens new avenues for efficiently constructing surface mechanisms. Furthermore, extending microkinetic modeling beyond mean-field approximations allows simulations under realistic catalyst operating conditions. Finally, the critical role of gas-phase mechanisms and comprehensive microkinetic modeling analyses in advancing our fundamental understanding of gas-solid catalytic processes is highlighted.

Digital strategies to improve the product quality and production efficiency of fluorinated polymers: 2. Heat removal performance of reactor with internal and external cooling systems

A reactor's heat transfer efficiency can be significantly enhanced and the fluid temperature uniformity can be controlled through introducing cooling water in the agitator and regulating the flow ratio of cooling water in the agitator and jacket.

FLOW RESISTANCE STUDY OF POROUS MEDIA BASED ON FIVE SPHERE MODEL

Flow resistance in porous media has been a challenging research topic. It has extremely important applications in many fields, such as energy, chemical industry, metallurgy, petroleum, materials, and nuclear reactors. However, it is difficult and hot to calculate the flow resistance. This paper presents the innovative five-sphere model by employing the capillary flow, pore-throat, and flowing-around models. The flow resistance of the five-sphere model incorporates capillary flow resistance, local resistance caused by the changes of pore-throat, and flowing-around resistance of fluids around the filling material, which is summarized to derive a formula for the flow resistance of porous media without empirical parameters. On the basis of 42 sets of experimental data obtained from the literature, this paper compares and validates the proposed model. When Re<sub>p</sub> < 30, the five-sphere model is compared with the Carman equation and the Ergun and WuJinsui equation; when Re<sub>p</sub> > 30, the comparison is made with the Ergun and WuJinsui equation. Of the 22 data sets with deviations in the range of 0% to 30%, the five-sphere model equation for particles had an average diameter of 0.2 to 56.8 mm, porosity ranging from 0.32 to 0.4174, superficial velocities ranging from 0.000038 to 0.5342 m/s, and Reynolds number ranging from 0.124 to 10,730. Through further analysis of viscous and inertial resistance, it was found that viscous resistance losses from capillary flow and flowing around contribute the most; when Re<sub>p</sub> is < 30, inertial resistance losses from diameter change, and flowing around contribute the most when Re<sub>p</sub> > 150. This further confirms that flowing around occupies an important position in the flow resistance of porous media.

Multiscale analysis of the M1 MoVNbTeO catalyst for ethylene production via selective ethane oxidation: From atomistic calculations to the industrial reactor

Multiscale analysis of the M1 MoVNbTeO catalyst for ethylene production via selective ethane oxidation: From atomistic calculations to the industrial reactor

Design and modelling of a novel dual-type reactor for ammonia production

The ammonia production is one of the most essential petrochemical processes. This article focuses on the heart of this process, the ammonia synthesis reactor. First, an industrial fixed bed reactor for ammonia production, designed by Kellogg's company, is modeled and simulated. Next, a dual-type reactor is proposed to overcome the equilibrium limitations of the exothermic ammonia synthesis reaction. The rules of similar industrial reactor design methodology and the Particle Swarm Optimization (PSO)- Differential evolution (DE) optimization method are used to obtain the reactors' best design parameters and operational conditions. The length of the reactors, the number of tubes in each reactor, the diameter of the gas-cooled reactor, and the cooling water temperature are considered decision variables for the optimization. These variables are optimized to maximize the ammonia yield. Furthermore, the effect of co-current and countercurrent flow patterns on the efficiency of the proposed reactor is investigated. A one-dimensional pseudo-heterogeneous model is applied to simulate the reactor at steady-state conditions. The governing differential equations form a boundary value problem and are solved by the shooting method. The results show that the developed dual-type reactor satisfies all the design limitations. Furthermore, this novel reactor increases the ammonia production capacity by 574 tons per day compared to the conventional Kellogg reactor.

Selective Epitaxy of Tensile, Highly Doped SiP for Planar NMOS FD-SOI Devices

Fabricating advanced Fully Depleted SOI (FD-SOI) Complementary Metal Oxide Semiconductor Field Effect Transistors (CMOS) require numerous material and process improvements. Junctions between metal contacts and the channel are considered to be of major importance as they have a direct impact on device performances. A well-controlled increase of the active dopant concentration in the sources and drains regions close to the channel is indeed required to lower the contact resistance. The Selective Epitaxial Growth of tens of nm thick heavily in-situ doped SiGe:B or Si:P Raised Sources and Drains (RSDs) on each side of pMOS or nMOS devices will lower that contact resistance, inject some uniaxial compressive or tensile strain in the channel and yield enough material for (gemano-)silicidation.We study here the impact of process conditions on (i) the incorporation of phosphorus, (ii) the Si:P lattice deformation and (iii) the electrical resistivity of blanket, highly doped Si:P films (>1×10²¹ atoms.cm-3) grown at relatively high temperatures. We then evaluate Si:P growth selectivity on patterned structures.Layers were deposited in an industrial RP-CVD epitaxy reactor at relatively high temperatures (600-750°C) with conventional Si, P and Cl gaseous precursors. Reactor pressures were high (above 100 Torr). The Si:P layers were characterized thanks to XRD, Spectroscopic Ellipsometry, AFM, 4 point probe, Tof-SIMS and Haze measurements.A SiH2Cl2 + PH3 + HCl + H2 chemistry was first of all used to grow those Si:P layers on blanket Si(001) wafers. The partial pressure of phosphine P(PH3) was increased to enhance the phosphorous content [P] in films. Figure 1 shows XRD scans for such layers. Even if [P] increased as P(PH3) increased, the resulting P concentrations were not that high ([P] increased from 0.3% up to 1.6% for a 4-fold increase of P(PH3). Layer resistivities are provided in Figure 2. As expected, there is a resistivity drop from 0.507 mOhm.cm down to 0.405 mOhm.cm whenP(PH3) increases from 8 up to 32Torr. Above 32Torr, there is a plateau close to 0.4 mOhm.cm. This plateau is most likely due to the formation of electrically inactive PxV clusters above a given P concentration.Looking for highly doped SiP layers, we evaluated other solutions to increase [P]. Figure 3 shows HRXRD scans for films grown with a fixed PH3 flow and various SiH2Cl2 partial pressures. Increasing the SiH2Cl2 partial pressure resulted, for a given PH3 flow, in higher Si:P growth rates and P concentrations, as shown in Figure 4 (data coming from Fig. 3 HRXRD profiles). An increase of the PH3 partial pressure with a weak silicon flow indeed ended up in P surface saturation and P desorption.In Figure 5, we show a HRXRD scan typical of a highly tensile-strained, good crystalline quality Si:P film with a phosphorus concentration of 4.35×10²¹ atoms.cm-3. The electrical resistivity of that layer is 0.82 mΩ.cm. Above a P concentration threshold, the electrical resistivity indeed re-increases as [P] increases and reaches really high values (formation of huge numbers of electrically inactive PxV clusters). A Tof-SIMS depth profile of [P] in that sample is provided in Figure 6. TheP concentration from HRXRD is close to the one from Tof-SIMS (4.62×10²¹ cm-3), which is steady as a function of depth. Increasing too much the P content in the Si:P lattice to, ideally, obtain ultra-highly doped and really tensile-strained layers (to increase electron mobility in the channel nearby) is at first sight a no-go, as it results in electrical resistivity degradation. A significant fraction of electrically inactive PxV clusters can however be dissolved with the right annealing scheme to simultaneously have low resistivity and high tensile strain.In order to prepare the integration of such layers into FD-SOI devices, we then investigated selectivity on blanket oxide wafers (not shown here). Finally, we evaluated selectivity for mid P content Si:P layers ([P] = 3.6%) on actual FD-SOI devices. Figure 7 top-view SEM images show 2D Si:P RSDswithout any poly-nuclei on SiO2 isolation, SiN hard mask and spacers of gates. We thus succeeded in introducing highly doped tensile-strained SiP layers into FD-SOI devices. Figure 8 micro-Reciprocal Space Map around the (113) Bragg reflection used to to extract [P] in a 50×100 µm2 measurement box. It was 3.2%, a value slightly lower than on bulk, blanket Si, possibly because of loading effects. Figure 1

Surface Kinetics and Uniformity Issues in Low-Temperature Epitaxy of Sige and Si:P Layers

Fabrication of the modern Si/SiGe-based devices normally necessitates the application of reduced temperatures (in the range about 550-750 °C) during the growth, which imposes significant kinetic limitations. As a result, the growth rate, layer composition, and dopant incorporation show high sensitivity to the process parameters and even small temperature non-uniformities over the wafer may result in considerable variation of the SiGe layer thickness and composition.In the growth of Si:P layers, the intrinsic Si growth kinetics is supplemented with the influence of the P concentration on the Si:P growth rate that may differ significantly as compared to the undoped Si despite P incorporation in concentrations of 0.1 % and even lower. In addition, the trend of the growth rate variation (increase or decrease) is different at the atmospheric and reduced operating pressures.Under all these inputs, control of the thickness and composition uniformity over the 300 mm wafer becomes challenging and should involve the adjustment of both temperature distribution and process parameters, including zonal distribution of the gas flow rates.To approach the solution of this problem, we have developed models of SiGe growth from SiH4/SiH2Cl2 (DCS) and GeH4 as well as Si:P growth from DCS and PH3 in the atmosphere of hydrogen with possible addition of HCl. The models account for high coverages of the surface with the adsorbed H2 and HCl, resulting in the growth limitation by low density of the free adsorption sites (kinetically limited growth mode). In case of SiGe, the model accounts also for the dependencies of surface kinetic parameters on the Ge concentration in the layer.The models were carefully verified using numerous experimental data on the layer growth rate and composition versus temperature and precursor flow rates. Calculations with the developed models reproduce the effect and facilitate interpretation of the following experimentally observed trends: higher growth rate and lower Ge concentration at elevated temperatures and the opposite tendency at a higher HCl supply. This behavior is explained in terms of stronger kinetic limitations for the Si part of the alloy that weaken with the temperature increase and contribution of the added HCl to the surface site blocking.The strong and non-monotonic dependence of Si:P growth rate on the PH3 supply is attributed to the competition between the adsorbed HCl and P-containing species. Addition of PH3 to the reactive gas mixture results, on the one hand, in additional coverage of the surface with these species but, on the other hand, in removal of the adsorbed HCl from the surface due to its interaction with these species, followed by the formation of volatile products.Next, the developed approaches have been applied to the detailed modeling of the process in widely used industrial reactors to address the uniformity issue in dependence of the operating parameters and reactor settings. In particular, variation of the uniformity for different temperature distributions over the wafer and gas injection parameters will be discussed. Also, conclusions are made on the relative sensitivity of the thickness and composition to possible non-uniformities of the wafer temperature and details of species transport inside the reactor. Figure 1

Novel sparging strategies to enhance dissolved carbon dioxide stripping in industrial scale stirred tank reactors

Aerated stirred tank reactors are widely used in bio-process engineering and pharmaceutical industries. To supply the organisms with oxygen and control the pH value, oxygen is transferred from air bubbles into the liquid phase, and, at the same time, carbon dioxide is stripped from the liquid phase with the same gas bubbles. The volumetric mass transfer coefficients for oxygen and carbon dioxide are, therefore, of crucial importance for the design and scale-up of aerated stirred tank reactors. In this experimental work, the volumetric mass transfer coefficients for oxygen and carbon dioxide are investigated simultaneously to study their mutual influence. The mass transfer performance for oxygen and carbon dioxide is conducted in stirred tank reactors on the 3 L laboratory scale, 30 L pilot scale, and 15,000 L production scale. First, the influence of dissolved carbon dioxide on the oxygen mass transfer performance is investigated in a 30 L pilot scale stirred tank reactor. The results show that the volumetric mass transfer coefficient of oxygen is not affected by the concentration of dissolved carbon dioxide, but the total mass flux of oxygen decreases with increasing carbon dioxide concentration due to the decreasing partial pressure difference. With rising gassing rate and volumetric power input, both mass transfer coefficients for oxygen and carbon dioxide show the same increasing trend. Although this trend can also be observed when scaling down to the 3 L laboratory scale reactor, a significantly different effect must be considered for the scale-up to the 15,000 L industrial scale reactor. The limited absorption capacity for carbon dioxide of the gas bubbles during the long residence time in the industrial scale reactor is noticeable here, which is why the specific interfacial area is of negligible importance. This effect is used to develop a method for independent control of oxygen and carbon dioxide mass transfer performance on an industrial scale and to increase the mass transfer performance for carbon dioxide by up to 25%.

Theoretical study of particle and energy balance equations in locally bounded plasmas

In this study, new particle and energy balance equations have been developed to predict the electron temperature and density in locally bounded plasmas. Classical particle and energy balance equations assume that all plasma within a reactor is completely confined only by the reactor walls. However, in industrial plasma reactors for semiconductor manufacturing, the plasma is partially confined by internal reactor structures. We predict the effect of the open boundary area ( ) and ion escape velocity ( ) on electron temperature and density by developing new particle and energy balance equations. Theoretically, we found a low ion escape velocity ( / ) and high open boundary area ( ) to result in an approximately 38% increase in electron density and an 8% decrease in electron temperature compared to values in a fully bounded reactor. Additionally, we suggest that the velocity of ions passing through the open boundary should exceed under the condition .

Multi-Objective Optimization and Design for Industrial Vinyl Chloride Reactor by Hybrid Model

The acetylene conversion rate and vinyl chloride production capacity are the main economic indexes for vinyl chloride synthesis, and the reaction temperature is an important operating parameter to prevent the Hg active component from being loss. These three factors have not been taken into consideration simultaneously in the traditional optimization process, making it difficult to achieve optimization targets perfectly for industrial application. To overcome this problem, an efficient strategy framework was proposed based on a hybrid model. Compared with conventional paradigms, the proposed framework could not only reduce computational expense but optimize these two economic indexes with a constrained reaction temperature simultaneously. In addition, a machine learning method was used to conduct a feature analysis, which can reveal the potential interaction between different variables so key variables of this reactor could be identified. To demonstrate and verify this framework, multi-objective optimization involving multiple variables with constrained conditions for the industrial reactor was conducted from design and operation perspectives, respectively. The proposed strategy could provide optimal operational direction for the industrial reactor from these design and operation aspects, which contribute to the sustainable and highly efficient process development in this field. For the first section of an industrial vinyl chloride reactor, this strategy could realize significant improvement in the acetylene conversion rate from 81.34% to over 95.00% and in the vinyl chloride production capacity from 2.60 to above 3.40 mol/h in the operation scenarios, which can meet production requirements. So, the second section of the traditional reactor system is not needed at all.

Catalytic purification of helium concentrate from hydrogen: catalysts, conditions and features of the process

The paper presents the results of a study of Pt and Pd catalysts deposited on porous aluminum oxide in the reaction of hydrogen oxidation reaction for use the process of helium concentrate purification. The properties of the prepared catalysts were compared with the properties of a foreign reference catalyst. In a laboratory reactor using a mixture simulating helium concentrate, we studied the “ignition” and deactivation of catalysts at room temperature, which simulates the conditions at the inlet section of an industrial adiabatic reactor. The properties of catalysts were also studied at temperatures of 200, 250 and 300 °C under conditions simulating the middle part and the outlet of an industrial reactor. The secondary process of hydrogen formation at 250-300 °C was studied, which is explained by methane and ethane steam reforming which present in the model mixture simulating helium concentrate. The results of the work can be used in the development of domestic catalysts for the purification of helium obtained from natural gas.

A modeling analysis on industrial radial-flow packed-bed reactors for the catalytic dehydrogenation of long-chain normal paraffins: Appraisal of the modeling approach

Catalytic dehydrogenation of long-chain normal paraffins is the most attractive route for producing of linear alkyl benzene. To make this happen, the radial-flow packed-bed reactors are employed as one of the most efficient currently available technologies. Simplifying assumptions that are sometimes imposed on reactor models to reduce the computational cost may also significantly decrease the accuracy of simulations. Here, it is decided to shed light on this matter by assessing the effect of typical model-simplifying assumptions on simulation results. To this end, one- and two-dimensional semi-homogeneous models are used to simulate an industrial-scale radial-flow packed-bed dehydrogenation reactor under isothermal and adiabatic conditions. Simulations are designed in four 1D isothermal, 1D adiabatic, 2D isothermal, and 2D adiabatic modes to compare different modeling strategies and investigate the effect of flow distribution on the reactor performance. An appropriate LHHW kinetics model is considered for paraffin dehydrogenation and the main associated side reactions over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst. The model equations are solved numerically using the finite element method by COMSOL Multiphysics CFD software. The results show a 1–3 % discrepancy between the predictions of one- and two-dimensional models for feed conversion under isothermal and adiabatic conditions. In contrast, the comparison of isothermal and adiabatic results for each one- and two-dimensional models indicate a discrepancy of 33–36 %. Furthermore, the two-dimensional model shows a low non-uniformity in flow distribution under reaction conditions (∼ 0.175), which has a trivial negative effect on paraffin conversion.

Creating pyrolysis reactor for disposal of municipal solid waste

In order to utilize municipal solid waste (MSW), a prototype reactor for thermal processing was created using materials developed at the National Research Center “Kurchatov Institute” – Central Research Institute of Structural materials “Prometey”, the technology for decomposing MSW in the reactor was developed, and its tests were carried out. The test results allowed us to conclude that the use of pyrolysis reactors for recycling ensures the environmental safety of the process and produces high-temperature gas (1000–1200°C) suitable for further use in power plants. Technical requirements were determined for the development of an industrial reactor for the disposal of solid waste with a productivity of up to 10 t/h, taking into account the shortcomings identified during testing of the prototype.

Enhancing selectivity through forced dynamic operation with intraparticle diffusion limitations: Ethane oxidative dehydrogenation

During steady state operation (SSO) of industrial fixed-bed reactors, diffusion limitations are often present. Well-known impacts include the reduced rate of a positive order reaction and reduced selectivity of the desired intermediate product in a sequential reaction system. This work presents an approach for circumventing diffusion limitations through forced dynamic operation (FDO) of metal oxide catalyzed partial oxidation reactions. Through coupled experiments and modeling, we examine the use of FDO to mitigate selectivity losses of the intermediate product in a parallel-consecutive reaction. With the oxidative dehydrogenation (ODH) of ethane (C2H6) to ethylene (C2H4) over an Al2O3 supported VOx catalyst as the model reaction system, FDO is shown to curtail undesired C2H4 overoxidation to COx that predominates in steady state diffusion-limited pellets, resulting in C2H4 selectivities that are 15 % (absolute) higher compared to SSO in 2.6 mm catalyst pellets. A kinetic model reveals that FDO beneficially alters the distribution of chemisorbed (O*) and lattice (OL) oxygen, which respectively primarily participate in reactions consuming C2H4 and C2H6. FDO is shown to lead to less detrimental impact of diffusion on the ethylene selectivity and yield compared to SSO. During FDO, generated C2H4 reacts with unselective O*, leaving behind selective OL. The reduced bulk phase O2 in the reductive half cycle leads to accumulation of OL, suppressing C2H4 overoxidation. This effect is amplified via C2H4 trapping in the catalyst pellet. Thus, larger catalyst pellets exhibit selectivities that more rapidly increase with reduction time, inducing higher FDO cycle averages compared to SSO. The findings raise the prospect of applying FDO through feed switching or chemical looping as a way to increase intermediate yield in the class of partial oxidation reactions.

Dynamic mixing characteristics of a soft elastic tubular reactor (SETR): Experimental investigation and numerical simulation

In an innovative effort to mitigate material damage and enhance overall mixing performance, the use of a soft elastic tubular reactor (SETR) was explored. In this study, the mixing of tracer in SETR was observed with the help of non-invasive method. The effect of different parameters such as pusher squeezing frequency (F), distance between pushers (D) and pusher squeezing mode (M) on the flow field inside the SETR was also analyzed with the help of numerical simulations. The study also further optimized the operating parameters of the reactor. The experimental results proved the accuracy of the subsequent simulation model. Through the combination of response surface design and numerical simulation methods, it was found that all three factors have a significant effect on the mixing time. The results of this work add to our understanding of the mixing mechanism within SETR and present new opportunities for designing highly efficient industrial reactors.

Monitoring of volatile fatty acids during anaerobic digestion of olive pomace by means of a hand held near infrared spectrometer

The accumulation of volatile fatty acids (VFAs) over anaerobic digestion (AD) leads to malfunctioning of industrial reactors, hence decreasing biogas production. Real-time monitoring of VFAs is a challenge due to the complexity and high cost of current methods for their quantification. For this reason, this research evaluated the application of near infrared (NIR) spectroscopy to quantify volatile fatty acids as a tool for AD reactors monitoring. To do that, 129 samples from various AD reactors fed with olive oil pomace were taken and their NIR spectra were acquired with a hand-held spectrometer. After performing grid search, three spectral variable selection methods, namely competitive adaptive reweighted sampling, uninformative variable elimination (UVE) and successive projections algorithm, were assayed before developing PLRS models to correlate the NIR light transmittance through the samples at the wavelengths selected by those methods with their VFAs concentrations. UVE led to the best performance for all the VFAs assayed. Thus, R2 of validation of UVE-PLSR models for acetic, propionic, butyric, valeric and total VFAs were 0.895, 0.622, 0.866, 0.898 and 0.871, respectively. The predictive model for total VFAs achieved the highest accuracy (RMSEV = 539.5 mg/L), explained by the correlation between the light absorption at the wavelengths selected by UVE and the chemical characteristics of VFAs. All in all, the prediction errors achieved suggest that a portable near infrared spectrometer can be used for monitoring VFAs in AD processes.

Optimizing H2 production from biomass: A machine learning-enhanced model of supercritical water gasification dynamics

Supercritical water gasification (SCWG) is recognized as an efficient technology for biomass conversion, demonstrating substantial potential in the sustainable energy sector. This paper focuses on the H2 production by SCWG of biomass. The objective is to develop an accurate gasification kinetic model that can facilitate the optimization of industrial reactor designs. A series of SCWG experiments is conducted in a batch reactor system under temperature of 500–600 °C and residence time of 1–20 min. Based on the experimental results, a hybrid-driven model for SCWG reaction is established. Firstly, experimental data is utilized to delineate SCWG reaction mechanistic model and forecast gas yields with an acceptable error margin. Subsequently, a Wasserstein Generative Adversarial Network Gradient Boosting Regression Grid Search (WGAN-GBR-GRID) model is applied to acquire knowledge of the predictive errors from the mechanistic model and to develop a hybrid model. The hybrid-driven model significantly enhances the average relative prediction error from 15.56 % to 0.02 % when compared to the mechanistic model. This result underscores the potential of the hybrid model in optimizing SCWG technology and the Shapley Additive exPlanations (SHAP) values in feature analysis shows the possible shortcomings of mechanistic model, thereby providing a new perspective for SCWG reaction dynamics modeling.

Reaction Thermodynamic and Kinetics for Esterification of 1-Methoxy-2-Propanol and Acetic Acid over Ion-Exchange Resin.

The esterification of 1-methoxy-2-propanol (PM) and acetic acid (AA) is an important reaction for the production of 1-methoxy-2-propyl acetate (PMA). Herein, we used the macroporous ion-exchange resin Amberlyst-35 as a catalyst to explore the effects of reaction conditions on the reaction rate and equilibrium yield of PMA. Under the optimized conditions of a reaction temperature of 353 K, using the initial reactant PM/AA with a molar ratio of 1:3, and a catalyst loading of 10 wt%, the PMA equilibrium yield reached 78%, which is the highest equilibrium yield so far. The reaction equilibrium constants and activity coefficients were estimated to obtain reaction thermodynamic properties, indicating the exothermicity of the reaction. Furthermore, pseudo-homogeneous (PH), Eley-Rideal (ER), and Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic models were fitted based on experimental reaction kinetic data. The results demonstrate that the LHHW model is the most consistent with experimental data, indicating a surface reaction-controlled process and exhibiting an apparent activation energy of 62.0 ± 0.2 kJ/mol. This work represents a valuable example of calculating reaction thermodynamics and kinetics, which are particularly essential for promising industrial reactor designs.