Rapid Reaction Rate Research Articles

Understanding the synergistic blending octane behavior of 2-methylfuran

The autoignition kinetics of hydrocarbons is an important criterion for selecting fuels for piston reciprocating engines, and it can be determined by relative performance to mixtures of alkanes, n-heptane and iso-octane, under certain standardized operating conditions. 2-methylfuran is a potential biofuel candidate, whose autoignition chemistry is markedly different from alkanes. Its octane behavior when blended with paraffins also shows a marked difference. The blending octane behavior of a fuel is characterized by its Blending Octane Number (BON). The BON of 2-methylfuran was extensively characterized in this work. 2-methylfuran's BON was mapped from experimental ignition delay times measured in a constant volume combustion chamber using established correlations. The effect on BON was studied depending on the RON of the base fuel into which 2-methylfuran was blended, as well as the quantity of 2-methylfuran blended. BON of 2-methyfuran was greater than its RON by a factor of four or more for some blends studied. BON reduced with increasing RON of the base fuel, as well as with increasing quantity of 2-methylfuran blended. A chemical kinetic model was created by integration of well validated sub-models for the blend components, and then used to explain the chemical kinetics leading to the extremely high BON values of 2-methylfuran. The synergetic anti-knock blending effect of 2-methylfuran is partially due to its physical properties leading to a greater molar fraction per volume fraction in the blend compared to iso-octane. Analysis using chemical kinetic model revealed that the chemical action behind 2-methylfuran's blending octane behavior was due to its ability to quench OH radicals which are important to the low-temperature oxidation chemistry of alkanes. This quenching effect is achieved due to the more rapid reaction rate of 2-methylfuran with OH radical compared to iso-octane, followed by the immediate conversion of the adduct shifting the equilibrium towards the product.

Nucleophilic substitution reaction mechanisms: An atomic-molecular perspective on chemical speciation and transport properties in silicate melts

There has been no systematic attempt to determine if nucleophilic substitution (SN) reactions proceed in silicate melts, even though they commonly occur in gaseous and liquid phases containing C, Si, P, and Ge centered tetrahedra. The oversight is here rectified by providing such an analysis. Conditions required for nucleophilic substitution reactions to occur are: (1) the presence of nucleophiles (Lewis bases) which in silicate melts are bridging oxygen (BO), non-bridging oxygen (NBO−) and free oxygen (O2−); (2) the presence of tetrahedra (Q species) with strongly electrophilic centers (i.e., Si atoms); (3) the presence of Si transition species containing pentahedrally coordinated Si (i.e., VSi species); (4) rapid reaction rates among tetrahedral species. All conditions are met for silicate melts. For example, the strong nucleophile, NBO− exists at high temperatures in binary alkali and alkaline earths silicate melts due primarily to thermal agitation whereby some Si-NBO-M bonds are ruptured to produce the nucleophilic Si-NBO− moiety. This nucleophile attacks the Si center of an adjacent tetrahedron to form a SiO bond thereby producing a VSi transition species. The transition species decomposes by rupture of another SiO bond located on the polar opposite side of the transition species. Three types of SN reaction are recognized and all involve VSi transition species. They are NBO-BO exchange reactions (e.g., Q3 + Q4 → Q4 + Q3), disproportionation reactions (e.g., 2Q3 → Q4 + Q2) and polymerization reactions (e.g., Q3 → Q4 + 1/2O2−). H2O and OH− are also nucleophiles and their reaction with Q species proceeds via SN reaction mechanisms, and may cause depolymerization of melts. Hydrogen bonding of H2O to BO and NBO may also occur, as in ice and water, thereby enhancing H2O solubilities in melts. These latter reactions should neither depolymerize melts nor affect NBO/T values.The diffusivity of Si and O in melts, anionic conductivity and chemical speciation (e.g. Q species abundances) proceed via one or other SN reaction, with the transition species assuming a critical role in diffusivity, conductivity and viscosity. The SN reaction mechanism, coupled with transition state theory, provides explanations for: (1) the formation of pentahedrally coordinated Si (VSi) and its apparent restriction to highly siliceous glasses; (2) the remarkably similar diffusivities of Si and O in silicate melts; (3) the ‘jump distance’ (α) of the Eyring equation, which by the SN mechanism is ~3.5 Å (i.e., diameter of the VSi transition species); (4) the minimum number of monomeric units (i.e., Q species) involved in the ‘cooperative region’ of the Adam-Gibbs equation; and (5) the quantitative distribution of Q species in Na silicate glasses up to ~50 mol% Na2O.

Defect-rich porous carbon with anti-interference capability for adsorption of bisphenol A via long-range hydrophobic interaction synergized with short-range dispersion force

Wastewater features-directed design of an adsorbent is promising but challenging strategy for sustainable remediation of actual bisphenol A (BPA)-polluted water. Herein, we report that the discarded cigarette butt-derived porous carbon (AC-800) exhibit high capacity (865 mg/g), rapid reaction rate (186.9 mg/g/min) and outstanding durability for adsorption of BPA. Different from the most reported carbon-based adsorbents, quantitative structure-activity relationship studies unveil that graphitic defect plays a crucial role in the improvement of adsorptivity. Further studies illuminate that π-π interactions, electrostatic attraction and hydrogen-bond interaction play a negligible role whereas long-range hydrophobic interaction synergized with short-range dispersion force make a substantial contribution to BPA adsorption on AC-800. Benefited from this unique adsorption mechanism, AC-800 features a remarkable anti-interference capability and realizes the efficient clean-up of BPA from actual wastewater with complex backgrounds. This work sheds new light on mechanistic insight into the BPA adsorption on carbon-based materials and develops a fit-for-purpose designed adsorbent toward green remediation of practical wastewater.

Levulinic acid production through two-step acidic and thermal treatment of food waste using dilute hydrochloric acid

This research investigated the concept of a two-step acidic and thermal treatment for glucose extraction and levulinic acid (LA) production from food waste using dilute hydrochloric acid (DHA) as a catalyst, and subsequently analyzed the properties of the resulting humins. Glucose extraction was performed under various reaction conditions (reaction temperature range: 120-190 °C, DHA concentration range: 0.2-0.5% v/v); the glucose extraction yield of the acidic treatment step reached 83.17% under the optimal conditions (150 °C in 0.5% DHA). LA production was achieved during the thermal treatment step, which was investigated using two independent experiments to determine the influence of the reaction conditions (reaction time: 5-140min, concentration factor: 1.5-3.0, reaction temperature: 160-190 °C). The LA production process was affected by the concentration factor and the reaction temperature due to the low pH of solution and the rapid reaction rate, respectively. The thermal stability of the humins was highest at a concentration factor of 3.0 because of the 13.07 C/H ratio of the humins.

Subcritical Water Extraction of Valuable Metals from Spent Lithium-Ion Batteries

The leaching of valuable metals (Co, Li, and Mn) from spent lithium-ion batteries (LIBs) was studied using subcritical water extraction (SWE). Two types of leaching agents, hydrochloric acid (HCl) and ascorbic acid, were used, and the effects of acid concentration and temperature were investigated. Leaching efficiency of metals increased with increasing acid concentration and temperature. Ascorbic acid performed better than HCl, which was attributed to ascorbic acid’s dual functions as an acidic leaching agent and a reducing agent that facilitates leaching reactions, while HCl mainly provides acidity. The chemical analysis of leaching residue by X-ray photoelectron spectroscopy (XPS) revealed that Co(III) oxide could be totally leached out in ascorbic acid but not in HCl. More than 95% of Co, Li, and Mn were leached out from spent LIBs’ cathode powder by SWE using 0.2 M of ascorbic acid within 30 min at 100 °C, initial pressure of 10 bar, and solid-to-liquid ratio of 10 g/L. The application of SWE with a mild concentration of ascorbic acid at 100 °C could be an alternative process for the recovery of valuable metal in spent LIBs. The process has the advantages of rapid reaction rate and energy efficiency that may benefit development of a circular economy.

Single atomic cobalt catalyst significantly accelerates lithium ion diffusion in high mass loading Li2S cathode

It is widely accepted that catalysts in batteries can decrease the energy barriers of conversion reactions. However, little attention has been paid to their influence on ionic diffusion in the electrode or across the interface. Herein, we report that lithium ion diffusivity can be significantly accelerated in an intrinsically electrode by atomically-distributed metal catalyst. Electrochemical measurements have found single atomic cobalt catalyst embedded in a nanocarbon network is capable of increasing the kinetics of lithium ion, providing rapid conversion reaction rate in an ultrahigh-rate Li2S battery. Meanwhile, density functional theory simulations have revealed that the lithium ion diffusion barrier on a nanocarbon surface is highly sensitive to the dopant atoms and can be decreased by introduction of cobalt atoms. The synergetic effects of the well-known Li2S decomposition catalysis and the lithium ion diffusion acceleration allow us to achieve a high Li2S mass loading cathode with superior rate performance and reversibility. The as-prepared Li2S electrode converted from cheap Li2SO4 precursors can deliver a high rate capacity (441 ​mA ​h ​g-1 based on Li2S at 10 ​C) and long lifespan for 1500 cycles at 2 ​C with average capacity fading of 0.04% per cycle. Impressively, the high areal mass loading cells display a specific capacity of 340 ​mA ​h ​g-1 based on Li2S mass at 23.4 ​mA ​cm-2 (5 ​C) and a long cycle life (2.26 ​mA ​h ​cm-2 at 6.77 ​mA ​cm-2 after 200 cycles), which have not been reported for Li2S cathodes.

Multimachine Communication Network That Mimics the Adaptive Immune Response.

Biological organisms capable of controlling and performing a wide variety of functions have inspired attempts to mimic biological systems with designable intelligence. Here we develop a multimachine communication network (MMCN) to mimic the operation and function of adaptive immune response (AIR) via connecting three kinds of DNA machines built from module-functionalized gold nanoparticles. These machines simulate three critical immune cells, dendritic cells, T and B lymphocytes, and their differentiation and coordinated interaction upon exposure and response to an invading pathogen. MMCN is composed of standard modules with track, movement, and fuel components that allow for the (1) integration and adaptability of a single machine, (2) convenient spatiotemporal control of the sequential activation of a single machine, and (3) rapid reaction rate and high efficiency owing to an enhanced local concentration of interacting species. We show that the proposed network can sense and clear the corresponding pathogen via consecutive activation and connection of the machines, simultaneously forming a memory to respond more rapidly and effectively upon the second invasion of the pathogen. This system may be extended to construct powerful networks to execute more sophisticated tasks and accomplish diverse functions.

Solid-solid reaction of CuFe2O4 with C in chemical looping system: A comprehensive study

Oxygen carriers are critical in chemical-looping system to transfer oxygen and heat. Spinel CuFe2O4 is a promising oxygen carrier due to its low decomposition temperature, good resistance to sintering and oxygen deficiency. In this study, a comprehensive investigation of solid-solid reaction of CuFe2O4 with C was conducted on a fixed-bed reactor. The XRD, Raman and SEM proved the primary structure of CuFe2O4 with uniform external morphology in size and shape. The weight loss of CuFe2O4 in TG showed that it could release O2 at about 700 °C. The XRD and Raman results of solid products for various time intervals showed that CuFe2O4 was mainly transformed into CuFeO2 and Fe3O4 with a rapid reaction rate at the initial stage, and then CuFeO2 was reduced to Cu and Fe3O4, Fe3O4 was slowly reduced to FeO eventually. The DFT results indicated that C was in favor of adsorbing on O-terminated surface, and CuFe2O4 transformed into CuFeO2 and Fe3O4 accompanied by the formation of COx.

Design of carbonic anhydrase with improved thermostability for CO2 capture via molecular simulations

Chemical absorption of CO2 is the most widely used method to capture CO2. However, high cost and slow CO2 absorption rate severely hinder its commercial utilization. Human carbonic anhydrase II (hCA II) having rapid hydratase reaction rate can potentially overcome these obstacles but being highly unstable against harsh process conditions. To enhance thermostability, a novel CA was developed based on molecular simulations. Substituting residue Leu204 with Lys has a comparable hydratase activity as the wild type (WT) hCA II, 1.98 × 106 s−1 for kcat and 2.36 × 108 M−1s−1 for kcat/Km. Importantly, the replacement of L204 K results in higher temperature resistance with 100 % retention at 45 °C and around 50 % at 55 °C while WT totally inactivates at 45 °C. Furthermore, L204 K is able to maintain its activity in the presence of anions and EDTA. The robustness and efficiency of this novel CA make it a competitive candidate for CO2 capture.

Fabrication of injectable hydrogelsviabio-orthogonal chemistry for tissue engineering

Injectable hydrogelsviabio-orthogonal chemistry.

Iron(II)/Persulfate Mediated Newman–Kwart Rearrangement

Herein, we report that iron(II)/ammonium persulfate in aqueous acetonitrile mediates the Newman–Kwart rearrangement of O-aryl carbamothioates. Electron-rich substrates react rapidly under moderate heating to afford the rearranged products in excellent yields. The mild conditions, rapid reaction rates, and suitability for scale up offers immediate practical benefits to access functionalized thiophenols.

Iodine-Catalyzed Functionalization of Primary Aliphatic Amines to Oxazoles, 1,4-Oxazines, and Oxazinones.

Unprecedented I2-catalyzed α,α-C(sp3)-H, decarboxylative α-C(sp3)-H, lactonized α-C(sp3)-H, and α,β-C(sp3)-H functionalized 5- and 6-annulation as well as α-C(sp3)-H activated 6-lactonization of primary aliphatic amines are devised under aerobic conditions. The metal-free sustainable strategy was employed for the diverse construction of valuable five-and six-membered polycyclic N,O-heteroaromatics such as oxazoles, 1,4-oxazines, and oxazin-2-one with a rapid reaction rate and high yield. The viability of this mild nonmetallic catalysis is successfully verified through syntheses of labile chiral heterocyclic analogues. In contrast to the common practice, this method is not limited to use of prefunctionalized amines, directing groups (DGs) and/or transient DGs, metal catalysts, and traditional oxidants. The possible mechanistic pathway of the annulation reaction is investigated by control experiments and ESI-MS data collected for a reaction mixture of the ongoing reaction. The synthesized new compounds are potent organic nanobuilding blocks to achieve valuable organic nanomaterials of different sizes, shapes, and dimensions, which are under investigation for the discovery of high-tech devices of innovative organic nanoelectronics and photophysical properties.

Dense Na0.5K0.5NbO3 ceramics produced by reactive flash sintering of NaNbO3-KNbO3 mixed powders

Dense Na0.5K0.5NbO3 ceramics are successfully produced by reactive flash sintering of the NaNbO3-KNbO3 mixed powders, which enables the chemical reaction and sintering to take place simultaneously, skipping the preparation process of Na0.5K0.5NbO3 powders that is required in conventional production. The as-prepared Na0.5K0.5NbO3 ceramics exhibit the high piezoelectric coefficient d33. Besides the Joule heating, generation of high concentration of defects is proposed to explain the rapid reaction and sintering rates during the reactive flash sintering. This study presents a cost-effective way to prepare dense and pure ceramic materials from their basic constituents in one step at low temperature in short time.

Thermal decomposition behavior and kinetics for nitrolysis solution from the nitration of hexamethylenetetramine

In order to understand better thermal safety of the nitrolysis solution from the nitration of hexamethylenetetramine, its decomposition behavior was studied. The nitrolysis solution prepared was analyzed using isoperibolic experiments, differential scanning calorimetry (DSC), differential thermal analysis-thermogravimetry, and fourier transform infrared spectroscopy. An accurate kinetic model was proposed to describe the decomposition in the nitrolysis solution by applying an ordinary differential equation fitting method to isothermal DSC data and non-isothermal DTA data. We found that the thermal decomposition in the mixed solution is attributed to pyrolysis of organic nitrates in acid solution. The process is coupled with rapid reaction rate, great heat release, and huge amounts of reddish-brown gas produced. The decomposition in the nitrolysis solution follows a 1.162th Prout-Tompkins equation with autocatalysis, with a differential kinetic mechanism function of f(α) = (1 − α)1.162·α0.4189. The thermal safety evaluation and safety parameters were finally studied based on four criteria and isoperibolic experiment data. The thermal safety margin is less than 164.57 K and the bursting point of pyrolysis is 338.43 K at 5 min of delay time. These results show that the nitrolysis solution is hazardous and the thermal sensitivity is higher than that of 2-ethylhexyl nitrate and hexogen.

Magnetic polyelectrolyte complex (PEC)-stabilized Fe/Pd bimetallic particles for removal of organic pollutants in aqueous solution

Magnetic polyelectrolyte complex (PEC) based on chitosan and sodium ligninsulfonate as the support to stabilize Fe/Pd bimetallic particles (mPEC-Fe/Pd) were synthesized for the degradation and decolorization of organic pollutants in aqueous solution. The morphologies and structures of the as-obtained composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Various factors potentially influencing the decolorization performance of methyl blue (MB) and malachite green (MG) from aqueous solution (i.e., mPEC-Fe/Pd dosage, solution pH, initial dye concentration and reaction temperature) were investigated. mPEC-Fe/Pd exhibited higher catalytic activity towards the removal of MB and MG, which involved both adsorption of dye molecules on mPEC surface and reduction reaction by Fe/Pd particles. Nearly 99% and 91% of MB and MG were removed at initial dye concentration of 100 mg l−1 with 1.0 g l−1 of mPEC-Fe/Pd, respectively. The decolorization efficiency of MB and MG increased with the increase of solution pH and mPEC-Fe/Pd dosage but decreased with the increase of initial dye concentrations. mPEC-Fe/Pd could be recycled effectively, and the removal percentage of MB reached as high as 83.5% even at the eighth reuse. Furthermore, the catalytic performances were further investigated to remove other organic pollutants, in which 92.4% of oxytetracycline, 85.1% of Tetrabromobisphenol A, and 34.7% of norfloxacin were removed at 50 mg l−1 of aqueous solution using 1.0 g l−1 of mPEC-Fe/Pd. Due to high removal efficiency, rapid reaction rate, easy separation and good reusability, mPEC-Fe/Pd had the potential to become an environmental remediation material for the treatment of wastewater containing organic compounds.

Morphology tuning of inorganic nanomaterials grown by precipitation through control of electrolytic dissociation and supersaturation

The precise control of the morphology of inorganic materials during their synthesis is important yet challenging. Here we report that the morphology of a wide range of inorganic materials, grown by rapid precipitation from a metal cation solution, can be tuned during their crystallization from one- to three-dimensional (1D to 3D) structures without the need for capping agents or templates. This control is achieved by adjusting the balance between the electrolytic dissociation (α) of the reactants and the supersaturation (S) of the solutions. Low-α, weak electrolytes promoted the growth of anisotropic (1D and 2D) samples, with 1D materials favoured in particular at low S. In contrast, isotropic 3D polyhedral structures could only be prepared in the presence of strong electrolyte reactants (α ≈ 1) with low S. Using this strategy, a wide range of materials were prepared, including metal oxides, hydroxides, carbonates, molybdates, oxalates, phosphates, fluorides and iodate with a variety of morphologies.

Metal Oxides Applied to Thermochemical Water-Splitting for Hydrogen Production Using Concentrated Solar Energy

Solar thermochemical processes have the potential to efficiently convert high-temperature solar heat into storable and transportable chemical fuels such as hydrogen. In such processes, the thermal energy required for the endothermic reaction is supplied by concentrated solar energy and the hydrogen production routes differ as a function of the feedstock resource. While hydrogen production should still rely on carbonaceous feedstocks in a transition period, thermochemical water-splitting using metal oxide redox reactions is considered to date as one of the most attractive methods in the long-term to produce renewable H2 for direct use in fuel cells or further conversion to synthetic liquid hydrocarbon fuels. The two-step redox cycles generally consist of the endothermic solar thermal reduction of a metal oxide releasing oxygen with concentrated solar energy used as the high-temperature heat source for providing reaction enthalpy; and the exothermic oxidation of the reduced oxide with H2O to generate H2. This approach requires the development of redox-active and thermally-stable oxide materials able to split water with both high fuel productivities and chemical conversion rates. The main relevant two-step metal oxide systems are commonly based on volatile (ZnO/Zn, SnO2/SnO) and non-volatile redox pairs (Fe3O4/FeO, ferrites, CeO2/CeO2−δ, perovskites). These promising hydrogen production cycles are described by providing an overview of the best performing redox systems, with special focus on their capabilities to produce solar hydrogen with high yields, rapid reaction rates, and thermochemical performance stability, and on the solar reactor technologies developed to operate the solid–gas reaction systems.

Microfluidic Chip Injection Photo Solidification Molding Study on Reaction Kinetics

Microfluidic chip injection photocuring is a new method for microfluidic chip fabrication. The accuracy of microfluidic chip photocuring has an important impact on the reliability of microfluidic chip. The reaction rate of photocuring system directly affects the final quality and efficiency of microfluidic chip. The rapid reaction rate of photocuring system will lead to poor feeding effect of the reaction system. The forming accuracy is affected, and the reaction rate is too slow, which will increase the forming time and affect the forming efficiency. In this paper, the conversion rate and reaction rate of different active monomers and oligomers used in the formulation system of microfluidic chips were measured on-line. The photocuring reaction kinetics of microfluidic chips was studied, and the influence of the formulation system on the photocuring reaction was explored, which laid a foundation for optimizing the formulation of microfluidic chips.

Fenton Reaction-Modified Corn Stover To Produce Value-Added Chemicals by Ultralow Enzyme Hydrolysis and Maleic Acid and Aluminum Chloride Catalytic Conversion

Fenton reaction has been widely used for pretreatment of lignocellulose with the advantages of simple operation, a rapid reaction rate, and less pollution. In this study, batch and fed-batch Fenton...

Investigating the Effectiveness of Emulsified Acid on Sandstone Formation under High Temperature Conditions

Acid stimulation supports the oil and gas industry as a versatile mean in enhanced oil recovery to fulfil the world energy demand. Although hydrochloric acid can significantly improve the reservoir permeability, its rapid reaction rate at high temperature has created a barrier for acid penetration. Subsequently, emulsified acid has slowly gain its popularity due to its retardation effect which allows deeper penetration of acid into the formation and achieves minimal corrosion issues. Nonetheless, emulsified acid has rarely applied on sandstone formation. Since a large portion of reservoirs are made up of sandstone, the effects of emulsified acid on sandstone under high temperature conditions should be studied to unlock the effective usage of emulsified acid in restoring the hydrocarbon recovery from the potential sandstone reservoirs. Besides, it is also crucial to explore cheaper and greener substitute to formulate innovative emulsified acid in minimizing the high acidizing budget along with environmental concerns. In this project, 10 different emulsified acid combinations are prepared using hydrofluoric acid, hydrochloric acid, phosphoric acid, formic acid, acetic acid, cationic surfactant, diesel and waste oil. The pre-flush treatment (5 % CH3COOH: 10 % HCl) is followed by the main flush (emulsified acids) saturation for 3 days. The thermal stability of emulsified acids and their effect on the Berea sandstone properties are evaluated. Major outcome is that the emulsified acids have the capability to remain stable at 275 °F up to 6 hours with uniform and fine droplet size. It is also proven that most of the emulsified acids can improve the porosity and permeability of Berea sandstone core samples except for HF: H3PO4. Regardless of the types of oil used for emulsified acid formulation, HF: HCl acid combination shows the best performance enhancement for both diesel-based and waste oil-based emulsified acids. In sandstone acidizing, emulsified acid dissolves the minerals and create acid transport pathway with close connectivity between pore spaces, causing the formation of large and conductive channels within the rock. Hence, these positive results clearly reflect on the feasibility of emulsified acid application in sandstone matrix acidizing and the effectiveness of waste oil as a replacement fluid for diesel.