Reaction Calorimetry Research Articles

Hazard evaluation for chlorination and amination reactions of fluorocytosine production process

Reaction thermal runaway is one of the most important reasons leading to chemical accidents. With the rapid development of the chemical industry in the world, especially the fine chemical industry, various safety accidents also occur frequently. Therefore, it is necessary to study the exothermic behavior of the reaction process. In this study, reaction calorimeter was used to study the exothermic phenomena during the chlorination reaction and amination reaction. Differential scanning calorimetry was performed on the reactants, and thermogravimetric experiments were performed on the products. In addition, adiabatic experiment was performed to study the thermal runaway behavior of amination products under adiabatic conditions. The results showed that the target reactions generated a large amount of heat in the initial stage. The maximum temperature of amination reaction is higher than the initial decomposition temperature of the amination product under adiabatic condition. The pyrolysis of amination product was divided into three stages. The product had a high apparent activation energy at the beginning of decomposition, and the apparent activation energy decreased as the decomposition progressed.

Reaction Calorimetry in Continuous Flow Mode: A New Approach for the Thermal Characterization of High Energetic and Fast Reactions

A new method for the calorimetric characterization of high-energetic, fast reactions in flow mode has been developed. The use of an engineered flow reactor in combination with a process modelling software allowed the deconvolution of the reaction enthalpy from space-resolved temperature profiles. The new procedure was verified in a comparison with a conventional batch calorimeter and subsequently implemented for the thermal characterization of an organolithium flow process. The information collected for this reaction successfully supported a scale-up to the pilot plant. Overall, the new approach resulted to be superior when compared with established procedures, enabling the generation of precise calorimetric data in an accurate scale-down flow device.

Heat of absorption of CO2 in aqueous solutions of DEEA and DEEA + MAPA blends—A new approach to measurement methodology

The heat of absorption is an important parameter that affects the CO2 absorption and stripping performance of amine-based CO2 capture. The present paper aims at development of the experimental method of determining the heat of absorption using a batch reaction calorimetry. A prospective high‐capacity CO2‐capturing solvent based on an aqueous solution of N,N-diethylethanolamine (DEEA) blended with small concentrations of 3-(methyloamino)propylamine (MAPA) is therefore studied. The differential and integral heat of absorption of CO2 was measured at 40 °C and 60 °C using single DEEA and amine blends. Experiments show that the heat of absorption in DEEA and DEEA + MAPA blends depends both on loading and temperature, though the temperature dependency is not as high as reported earlier. Increasing the MAPA/DEEA concentration ratio increased the heat of absorption in the amine blends.

Graphene Oxide Synthesis: Reaction Calorimetry and Safety

While several studies have been published to optimize the oxidation–exfoliation process of modified Hummers’ method to make graphite oxide (GO), relatively few studies have explored the effects of ...

Thermal safety study on the synthesis of HMX by nitrourea method

HMX is one of the best high-energy explosives in military applications. In this paper, the reaction calorimeter (RC1e) was used to monitor the reaction process of HMX synthesis by the nitrourea method. The research results show that the heat release rate is large on the reaction feeding stage, the feed rate should be controlled. The thermal parameters, such as adiabatic temperature rise(ΔTad,r) and maximum temperature of the synthesis reaction (MTSR), were calculated for assessing the thermal hazard of HMX synthesis. Although the urea nitrification stage is safer, the operating conditions of other reaction processes also need to be redesigned to improve the process safety level. These studies have potential applications in inherently safer operating measures and safer storage and transportation.

Synthesis of 5-fluoro-2-nitrobenzotrifluoride in a continuous-flow millireactor with a safe and efficient protocol

A synthesis process of 5-fluoro-2-nitrobenzotrifluoride was achieved in a continuous-flow millireactor system through the nitration of 3-fluorobenzotrifluoride using the mixed acid as a nitrating agent. The process safety was evaluated based on the temperature rise with the use of Reaction Calorimeter and Differential Scanning Calorimetry. The mass transfer limitation for this nitration process in the millireactor was evaluated. Effects of the composition of the mixed acid, the molar ratio of nitric acid to the substrate, the residence time, and the temperature on the reaction performance in the millireactor were studied in order to obtain optimal operational conditions. A heat transfer assessment was made to discuss the effects of the residence time and the inner diameter on the temperature distribution and the substrate conversion. Compared with the traditional batch reactor, the flow reactor could achieve better control over impurity and higher process efficiency because of its enhanced mass and heat transfer rates under the optimized conditions. This continuous-flow synthesis strategy would be beneficial for the commercial manufacturing of fine chemicals and pharmaceutical intermediates with the involvement of nitration.

Thermodynamic characteristics of Li2MoO4, Li2W0.85Mo0.15O4 single crystals and stability direction for alkali molybdates

Single crystals of Li2MoO4 and Li2W0.85Mo0.15O4, as perspective materials to search for neutrino-less double beta decay, have been grown by low-temperature-gradient Czochralski technique (LTG CZ). The standard formation enthalpies for single crystals of Li2MoO4 and Li2W0.85Mo0.15O4 have been determined by two methods: (i) solution calorimetry in KOH (ΔfH0 (Li2MoO4, s, 298.15 K) = −(1521.9 ± 1.9) kJ mol−1) and (ii) high-temperature reaction calorimetry in sodium molybdate melt (3Na2O · 4MoO3) (ΔfH0 (Li2MoO4, s, 298.15 K) = −(1529.1 ± 7.3) kJ mol−1; ΔfH0 (Li2W0.85Mo0.15O4, s, 298.15 K) = −(1597.8 ± 4.3) kJ mol−1). The measured solution enthalpies of Li2CO3, MoO3, WO3, Li2MoO4, Li2W0.85Mo0.15O4 in 3Na2O · 4MoO3 melt and solution enthalpies of Li2CO3, MoO3, Li2MoO4 in KOH have been used to calculateΔfH0. The thermodynamic stability of A2MoO4 (A = Li, Na, K, Rb, Cs) with respect to simple oxides mixture has been determined. It has been found that the relative thermodynamic stability is increased from Li2MoO4 up to Cs2MoO4. This fact seems to be important from practical point of view. The lattice enthalpies for A2MoO4 compounds have been calculated using the Born-Haber cycle. The dependences of lattice enthalpies for A2MoO4 on structural parameters have been constructed, which allow one to predict the thermodynamics for compounds not investigated.

Mathematical modelling and simulation for decomposition of agro-herbicide in accelerated reaction calorimeter to avoid water pollution

Mathematical modelling and simulation for decomposition of agro-herbicide in accelerated reaction calorimeter to avoid water pollution

A modular 3D printed isothermal heat flow calorimeter for reaction calorimetry in continuous flow

The presented continuous flow calorimeter enables process understanding of novel flow syntheses and the use of highly reactive compounds. Adaptation of the calorimeter is possible via 3D printing and due to its modular and expandable design.

Integrated thermodynamic and kinetic model of homogeneous catalytic N‐oxidation processes

AbstractThe homogeneous phosphotungstic acid catalyzed N‐oxidation of alkylpyridines by hydrogen peroxide has important applications in pharmaceutical and fine chemical industries. Current industry practice is to employ a semibatch reactor with gradual dosing of hydrogen peroxide into an alkylpyridine/catalyst solution under isothermal conditions. However, due to lack of understanding of reaction mechanism and thermodynamic behavior, this system is subject to significant risk of flammability, fires and explosions due to hydrogen peroxide decomposition. In this study, we conducted semibatch N‐oxidation process in an isothermal reaction calorimeter (RC1) over a wide range of temperature, catalyst amount and oxidizer dosing rates. Reactor pressure, reaction heat generation rate and in situ FTIR spectra of liquid phase species were recorded in real‐time during experiments, and final product was quantified using HPLC and GC–MS analytical tools. We developed an integrated thermodynamic and kinetics model of homogeneous N‐oxidation reaction based on experimental results and past literature findings. More specifically, Wilson excess Gibbs model was employed to estimate activity coefficients of highly nonideal liquid mixture. We found ideal gas law was satisfactory in calculating incondensable oxygen pressure. First principle reaction mechanism and kinetics parameters of (a) catalytic N‐oxidation reaction; (b) catalytic hydrogen peroxide decomposition reaction; (c) noncatalytic N‐oxidation reaction; (d) noncatalytic hydrogen peroxide decomposition reaction was derived based on experimental findings of this study and past literature. The proposed integrated thermodynamic model and kinetics model successfully predicted highly nonlinear reactor pressure, species concentration and reaction enthalpy generation rate profile of homogenous catalytic N‐oxidation and H2O2 decomposition reaction. The optimal reactions conditions with maximum N‐oxide product yield and minimum reactor pressure and catalyst usage was theoretically identified and further verified by experiments. The obtained model can be used for inherently safer reactor design and applied to other homogeneous tungstic acid catalytic hydrogen peroxide oxidation processes.

Kinetic study of CO2 absorption in aqueous solutions of 2‐((2‐aminoethyl)amino)‐ethanol using a stirred cell reaction calorimeter

AbstractIn the literature, aqueous 2‐((2‐aminoethyl)amino) ethanol (AEEA) is identified as a promising solvent for postcombustion CO2 capture. In this work, the kinetics of CO2 absorption in the aqueous AEEA, containing a primary and a secondary amino group, is studied over a wide temperature range of 303.15‐343.15 K and the amine concentration in the range of 0.47‐2.89 M using the fall‐in‐pressure technique in a stirred cell reaction calorimeter setup with a horizontal gas‐liquid interface. The overall rate constants for (AEEA + H2O + CO2) reaction system are estimated in the pseudo–first‐order reaction regime. The kinetic models based on zwitterion and the termolecular reaction mechanisms are used to predict kinetic rate constants. The experimental kinetic data are better correlated using the zwitterion mechanism (AAD 9.18%) than that of the termolecular mechanism (AAD 10.4%). The density, viscosity, and physical solubility of pure components and aqueous binary mixtures of AEEA are also measured at the similar temperature and concentration ranges of rate kinetics. Empirical models are proposed to predict pure component density and viscosity data with AAD of 0.02% and 7.17%, respectively. The Redlich‐Kister model, the Grunberg‐Nissan model, and the O'Connell's model are used to correlate experimental density, viscosity, and physical solubility data of the binary mixtures with AAD of 0.034%, 4.92%, and 6.5%, respectively. The reaction activation energy (Ea ∼ 32 kJ/mol) of the (AEEA + H2O + CO2) system is calculated from the Arrhenius power‐law model using the zwitterion mechanism, which indicates lower energy barrier than that of the reported value for monoethanolamine (∼44 kJ/mol) in the literature.

Inherent safer design for chemical process of 1,4-dioldiacetate-2-butene oxidized by ozone

Oxidation reaction is the typical thermal runaway reaction, and the reaction of 1, 4-dioldiacetate-2-Butene oxidized by ozone was investigated in this study. Firstly, the thermal hazards of the oxidative exothermic reactions were identified and evaluated combined process risk assessment method. The Qualitative Assessment for Inherently Safer Design (QAISD) was used to identify the risk of the reaction process. Meanwhile, the Reaction Calorimeter (RC1e) was used to obtain the thermal properties of the oxidation reaction. Then the inherent safer designs (ISD) were proposed according to the risk assessment results to increase the level of safety of chemical industry technique. 1) ISD I: reaction temperature was improved to –5 °C, and ventilation rate was improved to 200 L•h−1. 2) ISDII: using a tubular reactor as reaction vessel. The results indicated that the severity of the reaction hazard was reduced by 43%, and safety was improved significantly via two ISDs. Moreover, the inherent safety level of the reaction was increased by 63% and 43.4% via ISD Iand II, respectively. The reaction process get closer to inherent safety theories of “minimize,” “substitute,” and “moderate”.

Synthesis, Antitumor and Cytotoxic Activity of New Adamantyl O‐Acylamidoximes and 3‐Aryl‐5‐Adamantane‐1,2,4‐Oxadiazole Derivatives

AbstractO‐Acylamidoxime and 1,2,4‐oxadiazole derivatives were synthesized from adamantanecarbonyl chloride 1 and a diversity of arylamidoximes 2 a‐k. First, O‐acylamidoximes intermediates 3 a‐k were synthesized and subsequent cyclization under microwave irradiation afforded 1,2,4‐oxadiazol derivatives 4 a‐k. Molar Heat of Reaction Calorimetry studies performed from O‐acylamidoximes revealed influence of the substituent groups. A one‐pot two‐step methodology was also developed proving to be a viable protocol. Compounds were characterized by 1H and 13C Nuclear Magnetic Resonance (NMR) Spectroscopy, Elemental Analysis or High Resolution Mass Spectral Analysis, and subjected to cytotoxic studies in non‐tumoral Vero cells and antiproliferative activity tests in six malignant cell lines. Our findings suggest that compounds 3 derivatives presented a concentration‐dependent profile for chronic myeloid leukemia (K562) and acute promyelocytic leukemia (HL‐60) cell.

Synthesis of Poly(N-vinylcaprolactam)-Based Microgels by Precipitation Polymerization: Pseudo-Bulk Model for Particle Growth and Size Distribution.

Particle size distribution and in particular the mean particle size are key properties of microgels, which are determined by synthesis conditions. To describe particle growth and particle size distribution over the progress of synthesis of poly(N-vinylcaprolactam)-based microgels, a pseudo-bulk model for precipitation copolymerization with cross-linking is formulated. The model is fitted and compared to experimental data from reaction calorimetry and dynamic light scattering, showing good agreement with polymerization progress, final particle size, and narrow particle size distribution. Predictions of particle growth and reaction progress for different experimental setups are compared to the corresponding experimental data, demonstrating the predictive capability and limitations of the model. The comparison to reaction calorimetry measurements shows the strength in the prediction of the overall polymerization progress. The results for the prediction of the particle radii reveal significant deviations and highlight the demand for further investigation, including additional data.

BBDFA: A Practical Reagent for Trifluoromethylation of Allylic and Benzylic Alcohols on Preparative Scale

We report a safe and readily prepared reagent [1,1′-biphenyl]-4-yl 2-bromo-2,2-difluoroacetate (BBDFA) for Cu-catalyzed trifluoromethylation of allylic or benzylic alcohols. An operationally simple and column-chromatography-free process to prepare BBDFA was developed and demonstrated on >100 g scale. Detailed reaction calorimetry and thermal analysis of the deoxytrifluoromethylation were performed using cinnamyl alcohol as a model substrate, demonstrating that the reactions could be safely implemented on preparative scale.

Heat of Absorption of CO2 and Heat Capacity Measurements in Aqueous Solutions of Benzylamine, N-(2-Aminoethyl)-ethanolamine, and Their Blends Using a Reaction Calorimeter

In this study, the heats of absorption of CO2 in aqueous benzylamine (BZA), N-(2-aminoethanolamine) (AEEA), and their blends were measured using an automated reaction calorimeter in the temperature range of 303.15–343.15 K. The experimental concentrations of aqueous amine solutions were in the range of (0.49–4.0) mol BZA·kg–1 water, (0.51–4.11) mol AEEA·kg–1 water, (2.03 mol BZA + 2.09 mol AEEA)·kg–1 water, and (2.71 mol BZA + 1.39 mol AEEA)·kg–1 water. The heat capacities of the unloaded aqueous solutions of BZA, AEEA, and (BZA + AEEA) were also measured in similar temperature and concentration ranges to those for heat of absorption. The experimental heat of absorption of CO2 was presented as a function of CO2 loading, temperature, and amine concentration.

Process hazard evaluation for catalytic oxidation of 2-octanol with hydrogen peroxide using calorimetry techniques

In this work, various calorimetric and analytical techniques were implemented to identify reaction pathways and safety issues associated with the 2-octanol to 2-octanone two liquid phase catalytic reaction oxidative using aqueous hydrogen peroxide as oxidant, sodium tungstate (Na2WO4) as catalyst and methyltri-n-octylammonium hydrogen sulfate [CH3(n-C8H17)3N+HSO4−] as phase transfer catalyst. Differential scanning calorimetry (DSC) was employed to measure the temperature and heat flux of the reactant mixtures under dynamic scanning. Phi-TEC II adiabatic calorimeter was used to track temperature and pressure under worst runaway scenario. Isothermal reaction calorimeter (RC1e) was used to assess conditions relevant to normal process operations. Gas chromatography-mass spectrometry (GC–MS) was utilized to analyze final products of all measurements qualitatively and quantitatively. Data from both DSC and Phi-TEC II show that two highly exothermic reactions were detected with “onset” temperature at ~50 and ~220 °C, respectively. In all cases, only 2-octanol and 2-octanone were the identifiable compounds via GC–MS. 2-Octanol conversion was in the range of 15–50% and it reveals a linear correlation with overall heat generation. Data obtained verify that both exothermic peaks result from alcohol oxidation, thus indicating that in the conditions of the reaction and with the employed catalysts, hydrogen peroxide did not fully decompose at lower temperatures. Non-condensable gas generation measurements validated this argument. Based on those results, possible macroscopic reaction pathway was proposed. Furthermore, pressure and temperature profiles by PHI-TEC II indicated a potential transition to a homogeneous liquid phase at higher temperatures. The RC1e results verified that 2-octanol conversion was higher at higher stirring rates, while evaporative cooling of solvents tempered the reaction by removing the heat generated, thus improving safety. These findings can be further used to propose safer operating measures for design and scale-up of this reaction process to avert a potential runaway and to probe in the reaction pathways so as to increase inherently safer conditions for its performance.

Thermal hazard analysis of a biomass pretreatment process using ionic liquids

Ionic liquids (ILs) may have various applications as less hazardous solvents because of their thermal stabilities and low vapor pressures. However, it is challenging to remove heat from large amount because of IL’s high viscosity and low vapor pressure when cooling failure or abnormal reaction occurs. Because chemical processes using ILs on an industrial scale are still in the early phase of development, it is important to assess the associated thermal hazards of chemical process using ILs. This work proposes a systematic approach of analyzing thermal hazards of chemical process using ILs, based on the approach proposed by Stoessel and analyze the cellulose dissolution process using ILs containing impurities as a test case. Copper oxide, which might be contaminated from wood chips, was chosen as a model impurity. To analyze the thermal hazards of cellulose dissolution process using ILs, thermal analysis using small-scale reaction calorimeter, differential scanning calorimeter and thermogravimetry–differential thermal analysis–mass spectrometry were performed. From these results, reaction heat and heat value of ILs and its mixture were low, while CuO lowers the decomposition temperature of ILs and produces flammable gases. From these trials, exothermal reaction was not observed, while flammable gaseous products might be produced in vapor phase in the reactor.

Study of the risks of the graphene oxide preparation process by reaction calorimetry

The improved Hummers method uses graphite powder as the raw material to produce graphene oxide, whose preparation releases a large amount of heat. This heat release increases the risks associated with the process as it contributes to combustion and explosion accidents. Based on reaction calorimetry, differential scanning calorimetry, scanning electron microscopy, and energy-dispersive spectrometry, the mechanisms underlying such heat release and related hazards are discussed. According to the conditions influencing the heat release, an orthogonal experimental design was applied to quantify the amount of heat released and the oxidation degree during the preparation process. The optimum working conditions were determined in terms of the stirring speed (250 rpm), feeding time (60 min), feeding temperature (0 °C), and temperature of the intermediate-temperature stage (20 °C). These conditions effectively reduce the risks of the overall manufacturing process.

Customizable 3D-printed stirrers for investigation, optimization and scale-up processes of batch emulsion copolymerizations

Diverse and cost-effective polyamide stirrers, printed by fused deposition modeling, were used in a 0.5L reaction calorimeter (Mettler Toledo RC1e) to principally investigate the suitability and performance of 3D-printed stirrers. Thermal-initiated batch emulsion copolymerizations of styrene and butyl acrylate were successfully carried out with monomer contents between 20 and 40 wt% and temperatures in the range of 60 to 85 °C. Further, precisely adjusted stirrers were designed and fabricated based on a constant volume related power input for scale-up processes in a 10L batch reactor. This scale-manufacturing concept enables a time-effective and inexpensive access to versatile and tailor-made 3D-printed stirrers, even for the implementation in already existing reaction systems. Inline turbidity was used as online monitoring tool to detect the mixing characteristics and control the course of emulsion polymerization processes. Analytical results of the 10 L resembled those of the 0.5 L scale and proved our main objective to produce comparable droplet dispersions (±2 nm). The resulting emulsions from 0.5 and 10 L scale were stable with Zeta potential values down to –90 mV. Neither product adhesion on nor deformation of the 3D-printed stirrers were found even at higher temperatures, monomer contents or scale-up processes.