Reaction Calorimetry Research Articles

Study on the Thermal Safety of 3,7‐Dinitro‐1,3,5,7‐Tetraazabicyclo[3.3.1]nonane Synthesized by Nitrolysis of Hexamine

AbstractThe thermal flow curves of the nitrolysis for the synthesis of 3,7‐dinitro‐1,3,5,7‐tetraazabicyclo[3.3.1]nonane (DPT) from hexamine in the presence of different amounts of acetic anhydride were obtained using reaction calorimetry. The maximum heat release rates during the feeding process, the corresponding maximum adiabatic temperature rises, and the Maximum Temperature of the Synthesis Reaction (MTSR) were determined, respectively. The thermal stability of the reaction product DPT and the reaction mixture was analyzed, and data on their thermal decomposition characteristics were obtained. The thermal decomposition kinetic model was utilized to simulate the stability under adiabatic conditions. TD24 (The temperature corresponding to the time required to reach the maximum reaction rate under adiabatic conditions for 24 hours) of the reaction mixture was calculated as 69.65°C. According to the thermal hazard parameters of the reaction, the process's hazard level under various acetic anhydride addition conditions was determined to be level 5 using the cooling failure scenario method.

Thermodynamic Modeling of an Aqueous N,N-Dimethyldipropylenetriamine and Benzylamine Blend for Efficient CO2 Capture.

This study evaluates the carbon dioxide (CO2) capture capabilities of a novel aqueous blend of N,N-dimethyldipropylenetriamine (DMDPTA) and benzylamine (BA). The solvent properties such density, vapor- liquid equilibrium (VLE) of CO2 in the solvent, CO2 absorption enthalpy are evaluated experimentally for solvent composition of (5 mass% DMDPTA + 25 mass% BA), (10 mass% DMDPTA + 20 mass% BA), and (15 mass% DMDPTA + 15 mass% BA). Solvent density were measured in the temperature range of 303.15K-333.15K and correlated using Redlich-Kister excess molar volume model, with a low average absolute relative deviation (AARD) of 0.014. VLE data was measured using a custom-made stirred VLE cell, within CO2 partial pressure range of 2-200 kPa and at temperatures 313.15K, 323.15K and 333.15K. Equilibrium CO2 solubility data were correlated using a modified Kent-Eisenberg model, achieving an AARD of 1.5%. Enthalpy of CO2 absorption was measured at 313.15 K using a Meter Toledo reaction calorimeter. Results indicated that under similar process conditions and solvent composition, (DMDPTA+BA) blends exhibited significantly higher CO2 loading and low absorption enthalpy compared to aqueous BA and monoethanolamine (MEA) solvent alone indicating the potential of (DMDPTA+BA) blend as efficient CO2 capture solvent.

Study on the reaction selectivity and hazard of m-xylene nitration catalyzed by SO3H-functionalized ionic liquids with different anions: Experimental and theoretical approaches

Five imidazole based SO3H-functionalized ionic liquids (SFILs) with different anions were selected as catalysts to achieve efficient m-xylene nitration. The acidity and thermal stability of the ILs were characterized by UV–vis and thermogravimetry. The reaction selectivity of the m-xylene nitration catalyzed by five ILs was compared. [MIMBs]HSO4 had the best catalytic activity with the maximum yield of 98.1 %. The effect of ILs on the exothermic behavior of m-xylene nitration was explored by reaction calorimeter. The reaction enthalpy (ΔH) and adiabatic temperature rise (ΔTad) were calculated to evaluate process hazards. The reaction order for the decomposition of different nitration products under adiabatic conditions was essentially close to 1. The process risk level for m-xylene nitration with the introduction of selected ILs was essentially downgraded from conditionally acceptable to acceptable, and the criticality was reduced from class 3 to 1. Furthermore, the acidic active sites of the ILs were predicted by the electrostatic potential. The solubility of m-xylene in the IL was investigated through the calculation of interaction energy. The roles of ILs as solvents and catalysts in nitration were resolved by density functional theory calculations. These findings could contribute to the understanding of the effect of ILs in modulating the process hazards and improving the selectivity of m-xylene nitration, and provide theoretical guidance for elucidating the catalytic mechanism of ILs in nitration.

Mechanistic Studies and Reaction Calorimetry Enable Safe Scale-up of a Reduction with NaBH4 and TFA

Mechanistic Studies and Reaction Calorimetry Enable Safe Scale-up of a Reduction with NaBH4 and TFA

Calorimetric investigation on heat release during the disintegration process of pharmaceutical tablets

The compendial USP〈701〉 disintegration test method offers a crucial pass/fail assessment for immediate release tablet disintegration. However, its single end-point approach provides limited insight into underlying mechanisms. This study introduces a novel calorimetric approach, aimed at providing comprehensive process profiles beyond binary outcomes. We developed a novel disintegration reaction calorimeter to monitor the heat release throughout the disintegration process and successfully obtained enthalpy change profiles of placebo tablets with various porosities. The formulation comprised microcrystalline cellulose (MCC), anhydrous lactose, croscarmellose sodium (CCS), and magnesium stearate (MgSt). An abrupt temperature rise was observed after introducing the disintegration medium to tablets, and the relationship between the heat rise time and the tablet’s porosity was investigated. The calorimeter’s sensitivity was sufficient to discern distinct heat changes among individual tablets, and the analysis revealed a direct correlation between the two. Higher porosity corresponded to shorter heat rise time, indicating faster disintegration rates. Additionally, the analysis identified a concurrent endothermic process alongside the anticipated exothermic phenomenon, potentially associated with the dissolution of anhydrous lactose. Since lactose is the only soluble excipient within the blend composition, the endothermic process can be attributed to the absorption of heat as lactose molecules dissolve in water. The findings from this study underscore the potential of utilising calorimetric methods to quantify the wettability of complex compounds and, ultimately, optimise tablet formulations.

Effects of twelve organic solvents on process hazards and reaction selectivity of m-xylene nitration: Combined calorimetric technique and DFT calculations

Selection of appropriate solvents is of great significance for achieving efficient and safe m-xylene nitration. In this study, the exothermic behavior of m-xylene nitration under twelve organic solvents were studied by reaction calorimetry. The process hazards were assessed by calculation of thermal safety parameters. The reaction selectivity was quantified. The anhydrides exhibited the prominent promotion as water absorbent and active reagent in nitration, followed by selected aliphatic hydrocarbons, chlorinated hydrocarbons. While acetic acid, propionic acid and ethyl acetate had negative effects. The maximum yield of 95.6 % was achieved in nitric acid-acetic anhydride (HNO3-Ac2O) system. The thermal weight loss of the products appeared at around 150−230 °C by thermogravimetry experiments. The activation energy was determined to be 192.9 kJ/mol through adiabatic kinetic calculations. Furthermore, the solvent effects were analyzed by calculating the solvent polarity and its interaction energy with HNO3. The different action mechanisms of Ac2O and Pc2O on NO2+ generation were revealed. The density functional theory calculations were in agreement with the experimental results. These findings can provide guidance for understanding of the solvent effect on the reaction hazards and selectivity of m-xylene nitration, and provide experimental and theoretical basis for solvent screening for the nitration of similar aromatic compounds.

Machine-Learning-Based Kinetic-Free Hybrid Gray-Box Model to Predict Sulfuric-Acid-Catalyzed Esterification Reaction.

The sulfuric-acid-catalyzed esterification reaction of 2-butanol and propionic anhydride is a vital industrial process. In this paper, several experiments are conducted via reaction calorimetry to validate that both sulfuric and propionic acids have discernible catalytic effects on the reaction. This finding complicates the accurate description of the reaction kinetics through traditional methods. So this paper turns to a kinetic-free black-box model, Gaussian process regression (GPR) model via 24 experiments, as a more adaptable approach. Besides, the best GPR model is combined with traditional heat balance model to generate a hybrid gray-box model, which can give complete knowledge of reaction process. The hybrid gray-box model finally achieves maximum root-mean-square error (RMSE) of 0.0069 for conversion, 0.6535 for temperature, and 10.6087 for heat flow rate, underscoring its pretty good predictive ability.

Reaction calorimetry and structural crystal properties of non-ideal binary rhabdophane solid solutions (Ce1−xREExPO4·nH2O)

Rhabdophane is a hydrous phosphate that commonly replaces monazite as a weathering product in critical mineral deposits during the alteration of rare earth elements (REE) bearing carbonatites and alkaline igneous complexes. It is an important host to the light (L)REE (i.e., La to Gd) but the stability and structure of binary solid solutions between the Ce and the other LREE endmembers have not yet been determined experimentally. Here we present room temperature calorimetric experiments that were used to measure the enthalpy of precipitation of rhabdophane (Ce1−xREExPO4·nH2O; REE = La, Pr, Nd, Sm, Eu, and Gd). The solids were characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and the role of water in the rhabdophane structure was further determined using thermogravimetric analysis coupled with differential scanning calorimetry. The calorimetric experiments indicate a non-ideal behavior for all of the binary solid solutions investigated with an excess enthalpy of mixing (ΔHex) described by a 2- to 3-term Guggenheim parameters equation. The solid solutions were categorized into three groups: 1) binary Ce-La and Ce-Pr which display positive ΔHex values with a slight asymmetry; 2) binary Ce-Nd and Ce-Sm which display negative ΔHex values with a nearly symmetric shape; 3) Ce-Eu and Ce-Gd which display both negative and positive ΔHex values with nearly symmetric shape. The excess Gibbs energy (ΔGex) of the solid solutions was further investigated using a thermodynamic analysis approach of aqueous-solid solution equilibria and the optimization programs GEMS and GEMSFITS. The resulting ΔGex values combined with the calorimetric ΔHex values indicate that there is likely an excess entropy contribution implying important short-range structural modifications in the solid solutions dependent on the deviation of the REE ionic radii from the size of Ce3+. These observations corroborate with the trends in the Raman v1 stretching bands of the PO4-site. The excess molar volumes determined from X-ray diffraction analysis further indicate an overall asymmetric behavior in all of the studied binary solid solutions, which becomes increasingly important from La to Gd. The pronounced short-range order–disorder occurring in groups 2 and 3 solid solutions mimics some of the behavior observed from previous studies in anhydrous monazite solid solutions. This study highlights the potential to use the chemistry and the structural modifications of rhabdophane as potential indicators of formation conditions in geologic systems and permits improving our modeling capabilities of REE partitioning in critical minerals systems.

Fundamental effects of using power ultrasound to accelerate C3S hydration

Activation of cement hydration accelerates hardening of concrete, enables faster production rates or production at similar frequency but significantly reduced CO2 emissions. The present study sheds light at the reason for accelerated cement hydration when power ultrasound (PUS) is applied during mixing.The investigations analysed the effect of PUS on dissolution of tricalcium silicate (C3S), homogeneous precipitation of C-S-H as well its effect on C3S-hydration. A combination of analytical techniques such as electric conductivity, optical emission spectroscopy, thermogravimetry, conduction reaction calorimetry, scanning electron microscopy and specific surface analysis were applied. It was revealed that PUS has a significant effect on paste hydration, which is induced by heterogenous nucleation of C-S-H and CH immediately after sonication. These hydrates were formed and dispersed by sonication thus acting as in-situ formed crystal seeds which shorten the induction period of C3S hydration.

Continuous Synthesis of Diazo Acetonitrile: From Experiments to Physical and Grey‐Box Modeling

AbstractDiazo compounds are gathering interest for their potential in promoting greener synthesis routes. We investigate, at a lab‐scale, the continuous synthesis of diazo acetonitrile (DAN) using a micro‐structured flow reactor and a flow reaction calorimeter. Data concerning DAN formation in the former, and relative to reaction heat and gas flow rate in the latter, are collected. We present a physical and a grey‐box model, both of which are calibrated to our data. Compared to the physical model, the grey‐box approach allows to better incorporate the complex chemical reaction pathways of DAN.

Investigation of an optimization method for time constants to calibrate reaction calorimeters

In exothermic reactions, scale-up sometimes endangers the chemical process because of the risk of runaway reactions. Reaction calorimeters are used in a laboratory to design a safe chemical process by collecting thermal and kinetic parameters for scale-up. Because scale-up can magnify the errors obtained in laboratory experiments, the cooling capacity can be improperly calculated based on the underestimated heat generation due to thermal lag. Therefore, reaction calorimeters are required to provide accurate heat flow despite thermal delays inherent in the reaction calorimeters.This study validates the time-constant search method for a reaction calorimeter that employs a function of smoothness S(τ) in the presence of noise. The degree of noise was determined by measuring the actual value using a reaction calorimeter. The simulation conducted using spreadsheets demonstrated that even in the presence of noise, it is possible to achieve high accuracy in the search for time-constants when there is a small thermal lag and a large intensity of calibration heat. Moreover, the use of a third-order polynomial approximation to calculate the derivative value proved to be suitable for determining the time constant accurately.

Investigation of soybean oil epoxidation process with phase transfer catalyst: Risk of thermal runaway

This paper explores an efficient and eco-friendly epoxidation process using the phase transfer catalyst ([(C18H37)2(CH3)2N]3{PO4[W(O)(O2)2]4}), which offers more advantages over the use of carboxylic and inorganic acids as catalysts in the Prileschajew epoxidation process. Consequently, a study of the process's thermal hazards is imperative. The paper conducts a comprehensive analysis of the process, employing a combination of calorimetric techniques. The critical runaway temperature, stabilization temperature, and required heat dissipation rate to prevent thermal runaway reactions were calculated using the Semenov model. On-line Fourier transform infrared spectroscopy and reaction calorimetry were used to relate the reaction mechanism and exothermic behavior of the actual production process, and a reliable model was developed for the calculation of reaction enthalpy. The findings indicate that the thermal risk depends on the rate of double bond epoxidation, which provides offering valuable insights for safe industrial-scale ESO production.

GET 133-2023 State Primary Special Standard for the unit of heat in the field of solution and reaction calorimetry

GET 133-2023 State Primary Special Standard for the unit of heat in the field of solution and reaction calorimetry

Multiresponsive Core-Shell Microgels Functionalized by Nitrilotriacetic Acid.

Stimuli-responsive microgels with ionizable functional groups offer versatile applications, e.g., by the uptake of oppositely charged metal ions or guest molecules such as drugs, dyes, or proteins. Furthermore, the incorporation of carboxylic groups enhances mucoadhesive properties, crucial for various drug delivery applications. In this work, we successfully synthesized poly{N-vinylcaprolactam-2,2'-[(5-acrylamido-1-carboxypentyl)azanediyl]diacetic acid} [p(VCL/NTAaa)] microgels containing varying amounts of nitrilotriacetic acid (NTA) using precipitation polymerization. We performed fundamental characterization by infrared (IR) spectroscopy and dynamic and electrophoretic light scattering. Despite their potential multiresponsiveness, prior studies on NTA-functionalized microgels lack in-depth analysis of their stimuli-responsive behavior. This work addresses this gap by assessing the microgel responsiveness to temperature, ionic strength, and pH. Morphological investigations were performed via NMR relaxometry, nanoscale imaging (AFM and SEM), and reaction calorimetry. Finally, we explored the potential application of the microgels by conducting cytocompatibility experiments and demonstrating the immobilization of the model protein cytochromec in the microgels.

Challenges of Scaling-up the Wet-Chemical Synthesis of β-Li3PS4

All-solid-state batteries are considered the next generation in battery technology due to increased energy and power density as well as freedom of design, e.g. by constructing batteries in bipolar stacks. Solid-state electrolytes offer advantages over conventional liquid electrolytes, such as greater thermal safety, because of high melting points, and higher mechanical strength. This is believed to suppress growth of lithium dendrites and, therefore, opens up the possibility of using a lithium metal anode. One promising material group is sulfides, because they are ductile and have a good intrinsic ionic conductivity. Some sulfide solid electrolytes can be synthesized wet-chemically. This offers advantages like tailoring the particle size, working at ambient temperatures, short synthesis durations, stabilizing meta-stable phases by using new synthesis routes and the possibility of transferring the routine to a continuous process. The particle size and morphology are important factors regarding the suitability to produce all-solid-state batteries wherefore small (< 10 µm) and homogeneous particles are preferred. The present research mainly focusses on finding and improving new materials and their usage in battery production, but there is little progress on mass-production of sulfide solid electrolytes. To scale-up a synthesis, multiple aspects have to be considered since they often influence both product and process. Therefore, an analysis and optimization of the synthesis process is necessary to support the development and to increase the economic attractiveness of new materials.In this presentation, the reaction enthalpy and the influences of concentration and solvent variation of synthesizing the sulfide solid electrolyte β-Li3PS4 are examined and discussed. β-Li3PS4 is synthesized by mixing lithium sulfide and phosphorus pentasulfide in a solvent, e.g. THF, at ambient conditions. After removing the solvent, heat treatment is used to obtain the crystalline product. We found that the mixing step contains a highly exothermic reaction and determined the reaction enthalpies using a reaction calorimeter. To handle the heat development, two options were investigated: First, the solvent amount was increased and second, the synthesis was performed using alternative solvents with different thermal properties. The examined solvents are THF, ethyl acetate and ethyl propionate. The reaction enthalpies of the synthesis in different solvents are compared. A strong influence on the particle size and morphology caused by the amount and choice of solvent could be detected by SEM. While the particle size increases with increasing amount of solvent, the shape of the particles alters under solvent variation. With low solvent amount the smallest particle sizes (< 10 µm) are synthesized. Finally, suggestions regarding the scale-up will be given based on the findings of these examinations.

Nitration of biodiesel by acetyl nitrate: Kinetic study and chemical safety parameters

The aim of this study was to synthesize a bio-sourced substitute to the 2-Ethyl Hexyl Nitrate (EHN) by nitrating a biodiesel. EHN is commonly used to improve the auto-ignition properties of diesel fuels. The biodiesel was obtained by trans-esterification of canola oil. The nitration reaction of biodiesel by acetyl nitrate was carried out in a reaction calorimeter RC1 with semi-batch mode to study its kinetic and exothermic behavior and acetyl nitrate as nitrating agent. The impact of the synthesis temperature on the thermal behavior and on the reaction medium composition was investigated. The final product was analyzed by using several analytical techniques such as iodine value, infrared spectrometry, GC–MS. Three nitrated products have been identified: Methyl-8-nitro oleate, Methyl-10-nitrate-9-nitrostearate and 10-acetoxy-methyl-9-nitrostearate, whose selectivity depends on the synthesis temperature. A chemical model for nitration is proposed and the thermal power profiles released by the reaction mixture are used to estimate the energy and chemical kinetic parameters. Safety parameters, maximum temperature of the synthesis reaction (MTSR) and TD24 were also determined. In addition, a Cooperative Fuel Research (CFR) engine was used to analyze the cetane number of diesel fuel mixed with our additive. The results showed an increase in cetane number by 6 points.

The Optimization of the Synthesis Process and the Identification of Levobupivacaine Hydrochloride.

In this study, we not only optimized and improved the synthesis process of levobupivacaine hydrochloride (21) but also conducted a comprehensive exploration of critical industrial-scale production details, and a novel high-performance liquid chromatography (HPLC) analysis method was developed. Starting with the readily available and cost-effective (R,S)-N-(2,6-dimethylphenyl)piperidine-2-carboxamide (28) as the initial material and utilizing l-(-)-dibenzoyl tartaric acid (29) for chiral separation, and then through substitution and a salting reaction, levobupivacaine hydrochloride (21) was obtained with high purity (chemical purity of 99.90% and enantiomeric excess (ee) values of 99.30%). The total yield of the three steps was 45%. Structures of intermediates and the final product were confirmed using nuclear magnetic resonance (NMR) (1H NMR, 13C NMR), mass spectrometry (MS), and elemental analysis. The crystal structure of the final product was determined through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Furthermore, we evaluated the risk of the substitution reaction using a reaction calorimeter and accelerating rate calorimetry (ARC). This process offers the advantages of simple operation, greenness, safety, controllable quality, and cost-effectiveness. It provides reliable technical support for the industrial-scale production of levobupivacaine hydrochloride (21), which is of significant importance in meeting clinical demands. Pilot-scale production has already been successfully completed by China National Medicines Guorui Pharmaceutical Co., Ltd., with a production scale of 20 kg.

Use of isoperibolic reaction calorimeter for the study of reaction kinetics of acetic anhydride hydrolysis reaction: Effect of acetic anhydride and water ratio

Use of isoperibolic reaction calorimeter for the study of reaction kinetics of acetic anhydride hydrolysis reaction: Effect of acetic anhydride and water ratio

Thermal safety and overall kinetics for methyl methacrylate solution polymerization via on-line process analytical technology

Polymethyl methacrylate (PMMA) is widely used, but its polymerization process is highly hazardous and the relevant thermal hazards have not been adequately investigated. Herein, the thermal safety and kinetic mechanisms of methyl methacrylate (MMA) polymerization are explored. The effect of monomer concentration on the exothermic characteristics is first investigated using a reaction calorimeter. The results indicate that the exothermic behavior of this reaction is significantly influenced by the monomer concentration. Meanwhile, a quantitative relationship between the specific enthalpy and monomer concentration is determined. Moreover, overall rate expression is developed by a rapid quantitative method to further elucidate the quantitative dependence of reaction rate on the process conditions. Subsequently, adiabatic experiment is performed to reveal the thermal controllability of this reaction. Finally, risk level is ascertained to propose constructive countermeasures. This work provides guidance for the safe operation of MMA polymerization, and the methodology also furnishes universal solutions for analogous reactions.

State primary special standard of the unit of heat quantity in the fi eld of solution and reaction calorimetry GET 133-2023

The article shows the need to develop methods and tools for realization and transferring a unit of heat quantity in the fi eld of measuring small thermal effects of physical and chemical interactions by the method of isothermal titration calorimetry. The relevance of the work is due to the wide application of measuring instruments implementing this method and the lack of standardized metrological procedures and tools. To solve the problem of ensuring unity and traceability of measurements in this fi eld, VNIIM calorimetry laboratory conducted research to expand the functional and measuring capabilities of the State primary special standard of the unit of heat quantity in the fi eld of solution and reaction calorimetry GET 133-2012. In the course of work a reference titration microcalorimeter MKT was developed, investigated, and included in the GET 133-2012. Microcalorimeter MKT was designed to realize, store, and transfer a unit of heat quantity in the fi eld of measuring small thermal effects in liquid media. As a result of microcalorimeter studies, the capability of realizing and transferring a unit of heat quantity in a new range was confi rmed: from 100 to 5000 μJ with an expanded uncertainty from 1.2 to 8.6 %. The improved GET 133-2012 with an updated composition and new metrological characteristics was approved as the State primary special standard of the unit of heat quantity in the fi eld of solution and reaction calorimetry GET 133-2023. This lays the foundations for the creation of new metrological tools and procedures for transferring the unit of heat quantity in the fi eld of solution and reaction calorimetry.