Temperature Dependence Of Reaction Research Articles

Optimization of catalytic properties of Mucor racemosus lipase through immobilization in a biocompatible alginate gelatin hydrogel matrix for free fatty acid production: a sustainable robust biocatalyst for ultrasound-assisted olive oil hydrolysis

Immobilization is a key technology that improves the operational stability of enzymes. In this study, alginate-gelatin (Alg-Gel) hydrogel matrix was synthesized and used as immobilization support for Mucor racemosus lipase (Lip). Enzyme catalyzed ultrasound-assisted hydrolysis of olive oil was also investigated. Alg-Gel matrix exhibited high entrapment efficiency (94.5%) with a degradation rate of 42% after 30 days. The hydrolysis of olive oil using Alg-Gel-Lip increased significantly (P < 0.05) as compared to free Lip. Optimum pH and temperature were determined as pH 5.0 and 40 °C, respectively. The Vmax values for free and immobilized Lip were determined to be 5.5 mM and 5.8 mM oleic acid/min/ml, respectively, and the Km values were 2.2 and 2.58 mM/ml respectively. Thermal stability was highly improved for Alg-Gel-Lip (t1/2 650 min and Ed 87.96 kJ/mol) over free Lip (t1/2 150 min and Ed 23.36 kJ/mol). The enzymatic activity of Alg-Gel-Lip was preserved at 96% after four consecutive cycles and 90% of the initial activity after storage for 60 days at 4 °C. Alg-Gel-Lip catalyzed olive oil hydrolysis using ultrasound showed a significant (P < 0.05) increase in hydrolysis rate compared to free Lip (from 0.0 to 58.2%, within the first 2 h). In contrast to traditional methodology, using ultrasonic improved temperature-dependent enzymatic catalyzed reactions and delivered greater reaction yields. Results suggest that Alg-Gel-Lip biocatalyst has great industrial application potential, particularly for free fatty acid production. In addition, the combined use of enzyme and ultrasound has the potential of eco-friendly technology.

Non‐similar modelling of Williamson Fluid over a non‐linear stretching sheet with temperature dependent thermal conductivity and Chemical Reactions

AbstractIn this paper we investigate the mixed convection flow of a Williamson fluid under the effects of temperature dependent thermal conductivity and chemical reaction. The mathematical model for this phenomenon is described in a set of partial differential equations (PDEs) and further this set is reduced to a dimensionless system of nonlinear partial differential equations (PDEs) using a non‐similarity method. The non‐similarity method has an advantage over similarity methods for handling non‐similar problems. The method first uses transformations to reduce governing equations into dimensionless systems of PDEs. The effects of Grashof number of heat and mass transfer Weissenberg number, Prandtl number, Schmidt number and reaction rate parameters on velocity, temperature, and concentration profiles are given in forms of graphs.

Thermodynamic Studies on the Hydrolysis of Trivalent Plutonium and Solubility of Pu(OH)3(am).

The temperature-dependent reaction properties of actinide elements are of particular interest in the safety assessment of high-level radioactive waste (HLRW) disposal systems. In this study, the hydrolysis of Pu(III) and the solubility of Pu(OH)3(am) were investigated at various temperatures (10-40 °C) in 0.1 M NaClO4. A strong reducing condition for maintaining the oxidation state of Pu(III) while slowly increasing the pH of the solution was realized by electrolysis. The formation constants of the first hydrolysis species, log *β1', and the solubility products of Pu(OH)3(am), log *Ks,0', at 10, 17, and 40 °C were experimentally determined using spectrophotometry, laser-induced breakdown detection, and radiometry. The enthalpy and entropy changes for these reactions were estimated using the van't Hoff equation. The first hydrolysis of Pu(III) is endothermic (ΔrHm° = 34.10 ± 4.48 kJ mol-1), and the dissolution of Pu(OH)3(am) is exothermic (ΔrHm° = -294.29 ± 23.05 kJ mol-1) with negative entropy changes. These thermodynamic data will contribute to improving the reliability of the safety assessment of HLRW disposal facilities and understanding the geochemical behavior of Pu under reducing or anoxic aqueous conditions at elevated temperatures.

Advances in Thermo-Electrochemical (TEC) Cell Performances for Harvesting Low-Grade Heat Energy: A Review

Thermo-electrochemical cells (also known as thermocells, TECs) represent a promising technology for harvesting and exploiting low-grade waste heat (&lt;100–150 °C) ubiquitous in the modern environment. Based on temperature-dependent redox reactions and ion diffusion, emerging liquid-state thermocells convert waste heat energy into electrical energy, generating power at low costs, with minimal material consumption and negligible carbon footprint. Recent developments in thermocell performances are reviewed in this article with specific focus on new redox couples, electrolyte optimisation towards enhancing power output and operating temperature regime and the use of carbon and other nanomaterials for producing electrodes with high surface area for increasing current density and device performance. The highest values of output power and cell potentials have been achieved for the redox ferri/ferrocyanide system and Co2+/3+, with great opportunities for further development in both aqueous and non-aqueous solvents. New thermoelectric applications in the field include wearable and portable electronic devices in the health and performance-monitoring sectors; using body heat as a continuous energy source, thermoelectrics are being employed for long-term, continuous powering of these devices. Energy storage in the form of micro supercapacitors and in lithium ion batteries is another emerging application. Current thermocells still face challenges of low power density, conversion efficiency and stability issues. For waste-heat conversion (WHC) to partially replace fossil fuels as an alternative energy source, power generation needs to be commercially viable and cost-effective. Achieving greater power density and operations at higher temperatures will require extensive research and significant developments in the field.

Transfer Learning Approach to Multitarget Temperature-Dependent Reaction Rate Prediction.

Accurate prediction of temperature-dependent reaction rate constants of organic compounds is of great importance to both atmospheric chemistry and combustion science. Extensive work has been done on developing automated mechanism generation systems but the lack of quality reaction rate data remains a huge bottleneck in the application of highly detailed mechanisms. Machine learning prediction models have been recently adopted to alleviate the data gap in thermochemistry and have great potential to do the same for kinetic data with the recent release of quality reaction rate data compilations. The ultimate goal is to formulate easily accessible, general-purpose, temperature-dependent, and multitarget models for the prediction of reaction rates. To that end, we propose a model that depends on the well-known Morgan fingerprints as well as learned representations transferred from the QM9 data set. We propose the use of an Arrhenius-based loss where predictions of the three modified-Arrhenius parameters (A, n, and B = Ea/R) are given instead of the direct prediction of reaction rate constants. Our model is >35% more accurate compared to a baseline model of feed forward network (FFN) on Morgan fingerprints.

Solution processed 2D SnSe nanosheets catalysts: Temperature dependent oxygen reduction reaction performance in alkaline media

• Single phase SnSe synthesis with non-toxic Se precursor, the monetary synthetic route is employed. • The SnSe catalysts 4-electron pathway for oxygen reduction. • The current density and charge transfer number of SnSe-500 catalysts are 4.50 mA/cm 2 and 3.62. One of the most effective synthesis routes is the simple solution process, which is an inexpensive way to make single phase 2-Dimensional (2D) Tin Selenide (SnSe) nanosheets. X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), and Field Emission Scanning Electron Microscope (FESEM) were used to confirm the structural and topographical investigations. 2D SnSe served for Oxygen Reduction Reaction (ORR) electrochemical performance in KOH solution. Later, 2D SnSe is annealed at 300, 400 and 500 °C later termed as SnSe-300, SnSe-400 and SnSe-500 respectively to investigate the electrochemical behavior of catalyst. As the temperature increases ORR performance improved. For the first time, 2- and 4-electron transfer pathway mechanism of SnSe catalysts is discussed. As enhancement in the performance of as prepared 2D SnSe catalysts ensured with various parameters like current density, electron charge transfer number and half-wave potential. SnSe-500 has a half-wave potential of −0.75 V, which is lower than other catalysts in this case. In addition, a current density of 4.50 mA/cm 2 was recorded, which is superior to other catalysts in this case.

Practicality assessment: Temperature-governed performance of CO2-containing Li–O2 batteries

Practical lithium–oxygen batteries require a shift from pure O2 to air. CO2 traces, however, fundamentally alter the O2 electrochemistry towards Li2CO3 formation via peroxocarbonate intermediates in highly-solvating electrolytes e.g., tetraethylene glycol dimethyl ether (G4). Here, we reveal that operating temperatures (0∼70 °C) critically dictate Li2CO3-associated cell overcharges (4.60∼3.77 V), by determining temperature-dependent reaction kinetics and evolving species mobility, as analogously witnessed under pure O2-conditions. Against what is observed for Li2O2 formation in the Li–O2 cell, however, cell temperatures do not govern the crystallinity of the Li2CO3 discharge product. In agreement with experimental observations, comprehensive density functional theory calculations also uncover the effect of the temperature on the Li2CO3 precipitation mechanism and shed light on the dwindling stabilization of metastable peroxocarbonate intermediates during discharge at increasing cycling temperatures. On the other hand, during extended operation, the temperature-dependent reactants mobility in the viscous G4 electrolyte and remnant Li-deficient carbonate surfaces from precedent recharge steps play equally prominent roles on the Li2CO3 precipitation mechanism and the resulting cell capacity. Our study highlights the complexity of practical Li–O2 cells with temperature-dependent performances.

A mathematical model to predict the color change of fresh dough sheets under fluctuation temperatures

The objective of this work was to establish a mathematical model to predict the color change of fresh dough sheets under fluctuation temperatures. The changes of color expressed in the parameters (L*, a*, b* and TCD) of green tea and turmeric dough sheets were measured at 5, 10, 20, 30 and 40 °C, respectively, and then the change models were established by zero- and first-order reaction kinetics model. The results showed that the first-order reaction kinetics model (all R2 > 0.9) fitted well the change of color parameter L* while the other parameters were not well fitted by zero- and first-order reaction kinetics model. Furthermore, the temperature-dependent reaction rate was assessed by the Arrhenius equation and showed better performance. Finally, a dynamic prediction model of parameter L* combining the first-order reaction kinetics model with the Arrhenius equation was established under fluctuation temperatures. The validation results showed that changes of parameter L* under fluctuation temperatures could be predicted accurately by the model. This study will may be useful to determine consumption time and shelf life under the dynamic product distribution channel by providing real-time indication of quality of fresh noodle products.

Colloidal Polydopamine Beads: A Photothermally Active Support for Noble Metal Nanocatalysts

Polydopamine (PDA) is a unique bioinspired synthetic polymer that integrates broadband light absorption, efficient photothermal transduction, and versatile surface-adhesion functions in a single material entity. Here, we utilize colloidal PDA beads in the submicron particle size regime as an easily processable and photothermally active support for sub-10 nm Pd nanocatalysts to construct a multifunctional material system that allows us to kinetically boost thermal catalytic reactions through visible and near-infrared light illuminations. Choosing the Pd-catalyzed nitrophenol reduction by ammonium formate as a model transfer hydrogenation reaction exhibiting temperature-dependent reaction rates, we demonstrate that interfacial molecule-transforming processes on metal nanocatalyst surfaces can be kinetically modulated by harnessing the thermal energy produced through photothermal transduction in the PDA supports.

Quantification of solid-phase chemical reactions using the temperature-dependent terahertz pulsed spectroscopy, sum rule, and Arrhenius theory: thermal decomposition of α-lactose monohydrate

Transformations of the low-energy vibrational spectra are associated with structural changes in an analyte and closely related to the instability of weak chemical bounds. Terahertz (THz)/far-infrared optical spectroscopy is commonly used to probe such transformation, aimed at characterization of the underlying solid-phase chemical reactions in organic compounds. However, such studies usually provide quite qualitative information about the temperature- and time-dependent parameters of absorption peaks in dielectric spectra of an analyte. In this paper, an approach for quantitative analyses of the solid-phased chemical reactions based on the THz pulsed spectroscopy was developed. It involves studying an evolution of the sample optical properties, as a function of the analyte temperature and reaction time, and relies on the classical oscillator model, the sum rule, and the Arrhenius theory. The method allows one to determine the temperature-dependent reaction rate V1(T) and activation energy Ea. To demonstrate the practical utility of this method, it was applied to study α-lactose monohydrate during its temperature-induced molecular decomposition. Analysis of the measured THz spectra revealed the increase of the reaction rate in the range of V1 ≃ ~9 × 10-4-10-2 min-1, when the analyte temperature rises from 313 to 393 K, while the Arrhenius activation energy is Ea ≃ ~45.4 kJ/mol. Thanks to a large number of obtained physical and chemical parameters, the developed approach expands capabilities of THz spectroscopy in chemical physics, analytical chemistry, and pharmaceutical industry.

New developments in premise plumbing: Integrative hydraulic and water quality modeling

AbstractSignificant seasonal changes in chemical and microbiological water quality can occur in buildings at different fixture locations due to temperature and time dependent reaction rates. Here, a series of calibrated plumbing hydraulic‐water quality models were developed for the extensively monitored Retrofitted Net‐zero Energy, Water &amp; Waste (ReNEWW) house in West Lafayette, Indiana, USA. The eight new models predict the absolute level of free chlorine, total trihalomethanes, copper, iron, lead, NO3− (nitrate‐nitrogen), heterotrophic plate count (HPC), and Legionella spp. concentration at each fixture for plumbing use, operational characteristics, and design layouts of the plumbing system. Model development revealed that the carrying capacity to describe Legionella spp. growth (and other organisms) under water usage and plumbing design conditions is lacking in the literature. Reducing simulated building water use by 25% prompted increased absolute concentrations of HPC and Legionella spp., each increasing by a factor of about 105. When the simulated service line length was increased, Legionella spp. concentrations increased by up to 106 gene copies /L in the Summer season. The proposed modeling framework can be used to support better planning, design, analysis, and operational decision‐making.

Transverse Initiation

The name transverse initiation was given to a situation where two explosives have a common interface, a detonation wave moves in the stronger explosive of the two perpendicular to that common interface, and the stronger explosive initiates the weaker explosive through the interface. In [1] they report on three configurations of transverse initiation tests, and on computer modeling of those tests. One feature of transverse initiation is the formation of an initiation layer in the weaker explosive along the common interface. Here we model those same tests using our reactive flow model TDRR (= reactant Temperature Dependent Reaction Rate). We get an initiation layer for the first two configurations but not for the third one. Also, there are some differences between our modeling results and those presented in [1], but there’s not enough information from the tests to conclude in favor of one of them.

Modeling Differential Enthalpy of Absorption of CO2 with Piperazine as a Function of Temperature.

Temperature-dependent correlations for equilibrium constants (ln K) and heat of absorption (ΔHabs) of different reactions (i.e., deprotonation, double deprotonation, carbamate formation, protonated carbamate formation, dicarbamate formation) involved in the piperazine (PZ)/CO2/H2O system have been calculated using computational chemistry based ln K values input to the Gibbs–Helmholtz equation. This work also presents an extensive study of gaseous phase free energy and enthalpy for different reactions using composite (G3MP2B3, G3MP2, CBS-QB3, and G4MP2) and density functional theory [B3LYP/6-311++G(d,p)] methods. The explicit solvation shell (ESS) model and SM8T solvation free energy coupled with gaseous phase density functional theory calculations give temperature-dependent reaction equilibrium constants for different reactions. Calculated individual and overall reaction equilibrium constants and enthalpies of different reactions involved in CO2 absorption in piperazine solution are compared against experimental data, where available, in the temperature range 273.15–373 K. Postcombustion CO2 capture (PCC) is a temperature swing absorption–desorption process. The enthalpy of the solution directly correlates with the steam requirement of the amine regeneration step. Temperature-dependent correlations for ln K and ΔHabs calculated using computational chemistry tools can help evaluate potential PCC solvents’ thermodynamics and cost-efficiency. These correlations can also be employed in thermodynamic models (e.g., e-UNIQUAC, e-NRTL) to better understand postcombustion CO2 capture solvent chemistry.

Detailed temperature‐dependent study of linoleic acid oxidative decomposition into volatile compounds in the heating process

In order to better understand the impact of heating temperature on volatiles forming during linoleic acid heating process, volatile profiling was investigated by using thermal-desorption cryo-trapping combined with gas chromatography–mass spectrometry. As a result, a total of 42 volatile compounds were detected and identified during this process, including aldehydes (12), ketones (6), alcohols (5), furans (6) acids (10), and aromatic compounds (3). The forming temperature of each volatile was determined. It reveals most volatiles with shorter carbon chains were generated at lower temperatures, while volatiles with longer carbon chains were generated at higher temperatures. Simultaneously, principal component analysis was used to analyze the volatile composition characteristics of linoleic acid at each temperature points. Results show volatile characteristics of linoleic acid had a big difference among different temperatures. One conclusion was drawn the volatile compound formation from linoleic acid is a temperature-dependent reaction rather than a time-dependent one during heating. Novelty impact statement Thermal desorption combined with GC–MS could be an effective method for studying the volatile compounds forming mechanism of linoleic acid during heating. Temperature plays a crucial role in the heating process. Volatile compound formation from linoleic acid is a temperature-dependent reaction rather than a time-dependent one during heating.

Temperature Regulates Stability, Ligand Binding (Mg2+ and ATP), and Stoichiometry of GroEL-GroES Complexes.

Chaperonins are nanomachines that harness ATP hydrolysis to power and catalyze protein folding, a chemical action that is directly linked to the maintenance of cell function through protein folding/refolding and assembly. GroEL and the GroEL-GroES complex are archetypal examples of such protein folding machines. Here, variable-temperature electrospray ionization (vT-ESI) native mass spectrometry is used to delineate the effects of solution temperature and ATP concentrations on the stabilities of GroEL and GroEL-GroES complexes. The results show clear evidence for destabilization of both GroEL14 and GroES7 at temperatures of 50 and 45 °C, respectively, substantially below the previously reported melting temperature (Tm ∼ 70 °C). This destabilization is accompanied by temperature-dependent reaction products that have previously unreported stoichiometries, viz. GroEL14-GroESy-ATPn, where y = 1, 2, 8 and n = 0, 1, 2, 8, that are also dependent on Mg2+ and ATP concentrations. Variable-temperature native mass spectrometry reveals new insights about the stability of GroEL in response to temperature effects: (i) temperature-dependent ATP binding to GroEL; (ii) effects of temperature as well as Mg2+ and ATP concentrations on the stoichiometry of the GroEL-GroES complex, with Mg2+ showing greater effects compared to ATP; and (iii) a change in the temperature-dependent stoichiometries of the GroEL-GroES complex (GroEL14-GroES7 vs GroEL14-GroES8) between 24 and 40 °C. The similarities between results obtained by using native MS and cryo-EM [Clare et al. An expanded protein folding cage in the GroEL-gp31 complex. J. Mol. Biol. 2006, 358, 905-911; Ranson et al. Allosteric signaling of ATP hydrolysis in GroEL-GroES complexes.Nat. Struct. Mol. Biol. 2006, 13, 147-152] underscore the utility of native MS for investigations of molecular machines as well as identification of key intermediates involved in the chaperonin-assisted protein folding cycle.

Solution Processed 2d Snse Nanosheets Catalysts: Temperature Dependent Oxygen Reduction Reaction Performance in Alkaline Media

Solution Processed 2d Snse Nanosheets Catalysts: Temperature Dependent Oxygen Reduction Reaction Performance in Alkaline Media

Nitrogen reduction reaction on single cluster catalysts of defective PC6-trimeric or tetrameric transition metal

The traditional Haber–Bosch method of ammonia (NH3) synthesis has low production efficiency and can lead to greenhouse gas emission due to high temperature and pressure dependent reactions.

In situ SERS monitoring of plasmon-driven catalytic reaction on gap-controlled Ag nanoparticle arrays under 785 nm irradiation

Plasmon-enhanced photocatalysis has attracted considerable attention due to its low energy consumption and high energy throughput. Surface-enhanced Raman scattering (SERS) is a highly sensitive and label-free nondestructive tool to investigate plasmon-driven photocatalytic reactions. Herein, we present a facile method to fabricate gap-controlled Ag nanoparticle (NP) arrays with uniform and high-density distribution of hot spots, which can be employed as both efficient plasmonic photocatalysts and stable SERS platforms. The plasmon-driven catalytic reaction of 4-nitrobenzenethiol (4NBT), which transforms it into p, p′-dimercaptoazobenzene (DMAB), is detected by using an in situ SERS technique at the excited wavelength of 785 nm. According to the temperature and laser power density dependent photocatalytic reaction rates observed on the Ag NP arrays, we quantitatively determined that the reductive coupling of 4NBT is more likely to occur as the gap decreases. The finite-difference time-domain (FDTD) simulation results demonstrate that the plasmonic hot spots are significantly enhanced with a decrease in gap, which in turn reduces activation energy. The gap-controlled Ag NP arrays are efficient for both promotion and detection of plasmon-driven catalytic reactions, and may pave a pathway for implementing efficient plasmonic photocatalytic platforms.

Glycosyl Triazole Ligand for Temperature-Dependent Competitive Reactions of Cu-Catalyzed Sonogashira Coupling and Glaser Coupling

Glycosyl triazoles have been introduced as efficient ligands for the Cu-catalyzed Sonogashira reaction to overcome the challenges of sideways homocoupling reactions in Cu catalysis in this reaction. The atmospheric oxygen in a sealed tube did not affect the coupling, and no need of complete exclusion of oxygen was experienced in the presence of glycohybrid triazole ligand L3. High product yields were obtained at 130 °C for a variety of substrates including aliphatic and aromatic terminal alkynes and differently substituted aromatic halides including 9-bromo noscapine. In contrast, at room temperature, a very low loading of the L3-Cu catalytic system could produce excellent yields in Glaser coupling including homocoupling and heterocoupling of a variety of aliphatic and aromatic alkynes.

Lithium Storage and Release From Lacustrine Sediments: Implications for Lithium Enrichment and Sustainability in Continental Brines

AbstractDespite current and projected future reliance on lithium (Li) as a resource, deficiencies remain in genesis models of closed‐basin Li brines. Subsurface geochemical interactions between water and bulk solid phases from lacustrine sediments, are shown here to be the most important process for brine genesis and sustainability of the Clayton Valley, NV brine deposit. A new subsurface basin model was developed and used to select Li‐bearing solids to test the release mechanisms for Li. Ash (20–350 ppm Li) and bulk sediments (1,000–1,700 ppm Li) samples across depths in the basin represent the majority of the subsurface Li‐bearing materials. Temperature dependent (25°C–95°C) batch reaction experiments using low‐salinity groundwater from the basin indicate a positive relationship between the amount of Li released and temperature. Four‐step sequential extractions on a subset of bulk sediments indicate most Li is released from water and weak acid‐soluble portions with approximately 30% of the total Li contained in the sediments released overall. We conceptualize that Li is released from these samples via three mechanisms: (a) release of adsorbed Li; (b) cation exchange of Li and Mg and; (c) possible minor release from the silicate structure at elevated temperatures. Based on these results and the abundance of Li‐bearing sediments in the subsurface we estimate the mean Li mass in the basin materials to be between 24.4 and 58.0 Mt which provides a continuous supply from water‐rock interactions. This is now the largest known accumulation of Li in a basin‐fill continental setting on a global scale.