Influence of Solvents on the Oxidation Kinetics of Aldehydic Group Compounds by Diethylammonium Chloro-chromate

The redox studies of some compounds containing aldehydic functional groups by diethyl ammonium chloro-chromate (DEACC) in dimethyl sulfoxide leading a product forming to acid of correspondimg order. Reactions are found to be in unit order with oxidant while a fractional order (less than unity) was found w.r.t. reductants. The redox reactions are influenced with acid, the acid dependence is governed by this equation: kobs = a + b[H+].. When isomeric form of aldehyde, that is Me-CDO is oxidised with the same oxidant it was observed a considerable K.I.E. (Deuterium effect; kH/kD = 05.69 at 298 K). The reaction of Acetaldehyde was done in various non aqueous medium, soluble or miscible in DMSO. The effect of solvent is studied fitting our data in the solvent model of Taft's and Swain's applied for this purpose.. Rate constants are correlating very well with already reported Taft’s values of *; further the reaction constants are negative in nature. Suitable mechanism involving are proposed with transfer of hydride ion..

Reactivity-Selectivity Principle: Phenyl Group in Indazole Makes It More Lucid

Linear free energy relationship (LFER) plots are constructed for the deprotonation equilibriums (pKaH+) of pyrazolium and indazolium (benzopyrazolium) cations. The reaction constants Taft * and Hammett  are found to be 2.75 and 1.32 for deprotonation (pKaH+) of pyrazolium and indazolium cations respectively. Higher value of Taft * than the Hammett  is explained in terms of extra stability of the indazolium cation due to its greater number of resonance structures. This article is an exercise to undergraduate students for writing different resonance structures of indazolium cation.

Measurement and Thermodynamic Modeling for CO2 Solubility in the N-(2-Hydroxyethyl) Piperazine + Water System

Amine scrubbing is the most important technique for capturing CO2. The cyclic diamine N-(2-Hydroxyethyl)-piperazine (HEPZ), a derivative of piperazine, with good mutual solubility in aqueous solution, a low melting point, and a high boiling point, has the potential to replace PZ as an activator added in the mixed amine system to capture CO2. In this study, the solubility of CO2 in aqueous HEPZ solutions was determined for three HEPZ concentrations and four temperatures. The VLE data for HEPZ-H2O were obtained using a gas–liquid double circulation kettle at pressure 30–100 kPa, and the thermodynamic model for the HEPZ-H2O-CO2 system was built in Aspen Plus based on the electrolytic non-random two-liquid (ENRTL) activity model. The physical parameters for HEPZ and the interaction parameters for ENRTL, along with reaction constants of carbamate reactions, were regressed. Using the thermodynamic model, the CO2 cyclic capacity, speciation with loading, and heat of reaction for the CO2 capture system by the aqueous HEPZ solution are predicted and analyzed.

Correlation analysis of reactivity in oxidation of some aliphatic aldehydes by 2-picolinium chlorochromate: A kinetic study

The oxidation of six aliphatic aldehydes by 2- picolinium chlorochromate (PICC) in dimethyl sulfoxide (DMSO) leads to the formation of corresponding carboxylic acids. The reaction is of first order each in PICC. A Michaelis-Menten type of kinetics is observed with respect to the aldehydes. The reaction is catalysed by hydrogen ions. The hydrogen-ion dependence has the form: kobs = a + b[H+]. The oxidation of deuteriated acetaldehyde MeCDO exhibited a substantial primary kinetic isotope effect (kH/kD = 5.69 at 298 K). The oxidation of acetaldehyde has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The rate constants correlate well with Taft’s * values, reaction constants being negative. A mechanism involving transfer of hydride ion has been suggested.

Removal Of Arsenic, Cadmium And Lead From Synthetic Stormwater By Two Low-Cost Adsorbents: A Kinetic And Equilibrium Study

The adsorption isotherms and kinetics of two low cost adsorbents, Ladybug Sand and Greensand, were determined from multi-solute batch experiments using prepared synthetic stormwater containing arsenic, cadmium and lead. The adsorption equilibrium data were fit to the Langmuir, Freundlich and Henry isotherms using both nonlinear and linear regression techniques. Kinetic data were obtained at two different stormwater concentrations. The kinetic curves were fit to the pseudo-first-order, pseudo-second-order and homogenous surface diffusion model (HSDM). A solution to the HSDM was achieved using the user-oriented numeric solution proposed by Zhang et al. (2009). From the fitted kinetic models the reaction constants, k1 and k2, as well as the surface diffusion coefficient (Ds) were determined. The maximum service lives of adsorbent columns comprised of Ladybug Sand or Greensand were calculated using the equilibrium column model (ECM) to evaluate the feasibility of the adsorbents for use in advanced stormwater treatment.

Removal Of Arsenic, Cadmium And Lead From Synthetic Stormwater By Two Low-Cost Adsorbents: A Kinetic And Equilibrium Study

The adsorption isotherms and kinetics of two low cost adsorbents, Ladybug Sand and Greensand, were determined from multi-solute batch experiments using prepared synthetic stormwater containing arsenic, cadmium and lead. The adsorption equilibrium data were fit to the Langmuir, Freundlich and Henry isotherms using both nonlinear and linear regression techniques. Kinetic data were obtained at two different stormwater concentrations. The kinetic curves were fit to the pseudo-first-order, pseudo-second-order and homogenous surface diffusion model (HSDM). A solution to the HSDM was achieved using the user-oriented numeric solution proposed by Zhang et al. (2009). From the fitted kinetic models the reaction constants, k1 and k2, as well as the surface diffusion coefficient (Ds) were determined. The maximum service lives of adsorbent columns comprised of Ladybug Sand or Greensand were calculated using the equilibrium column model (ECM) to evaluate the feasibility of the adsorbents for use in advanced stormwater treatment.

On Modeling of Synthesis Process of Boron Carbide Based Nanocomposites

Nanocomposites based on boron carbide B4C are hard materials with wide field of applications in modern technologies. A system of first-order ordinary differential equations that simulates the process of chemical synthesis of nanopowders of B4C–TiB2 compositions containing titanium diboride (TiB2) as an additional phase is suggested and resolved numerically for a typical ratio of reaction constants. Reagents and products concentrations are found as time-functions. In this way, the optimal route of production technology of boron carbide-based nanomaterials can be identified.

Learning and meta-learning of stochastic advection–diffusion–reaction systems from sparse measurements

Physics-informed neural networks (PINNs) were recently proposed in [18] as an alternative way to solve partial differential equations (PDEs). A neural network (NN) represents the solution, while a PDE-induced NN is coupled to the solution NN, and all differential operators are treated using automatic differentiation. Here, we first employ the standard PINN and a stochastic version, sPINN, to solve forward and inverse problems governed by a non-linear advection–diffusion–reaction (ADR) equation, assuming we have some sparse measurements of the concentration field at random or pre-selected locations. Subsequently, we attempt to optimise the hyper-parameters of sPINN by using the Bayesian optimisation method (meta-learning) and compare the results with the empirically selected hyper-parameters of sPINN. In particular, for the first part in solving the inverse deterministic ADR, we assume that we only have a few high-fidelity measurements, whereas the rest of the data is of lower fidelity. Hence, the PINN is trained using a composite multi-fidelity network, first introduced in [12], that learns the correlations between the multi-fidelity data and predicts the unknown values of diffusivity, transport velocity and two reaction constants as well as the concentration field. For the stochastic ADR, we employ a Karhunen–Loève (KL) expansion to represent the stochastic diffusivity, and arbitrary polynomial chaos (aPC) to represent the stochastic solution. Correspondingly, we design multiple NNs to represent the mean of the solution and learn each aPC mode separately, whereas we employ a separate NN to represent the mean of diffusivity and another NN to learn all modes of the KL expansion. For the inverse problem, in addition to stochastic diffusivity and concentration fields, we also aim to obtain the (unknown) deterministic values of transport velocity and reaction constants. The available data correspond to 7 spatial points for the diffusivity and 20 space–time points for the solution, both sampled 2000 times. We obtain good accuracy for the deterministic parameters of the order of 1–2% and excellent accuracy for the mean and variance of the stochastic fields, better than three digits of accuracy. In the second part, we consider the previous stochastic inverse problem, and we use Bayesian optimisation to find five hyper-parameters of sPINN, namely the width, depth and learning rate of two NNs for learning the modes. We obtain much deeper and wider optimal NNs compared to the manual tuning, leading to even better accuracy, i.e., errors less than 1% for the deterministic values, and about an order of magnitude less for the stochastic fields.

Application of Wastewater Reuse with Photocatalyst Prepared by Sol-Gel Method and Its Kinetics on the Decomposition of Low Molecular Weight Pollutants

The development of immobilized photocatalyst as a strategy for problematic electronics wastewater reuse is described in this study. The strategy was to perform separate rinsing, mostly consisting of low molecular weight compounds, and to decompose them with a simple process, based on the advanced oxidation process (AOP). Extensive studies were performed on the preparation conditions of immobilized photocatalysts by sol-gel method under various amount of precursor and support, water to precursor ratio, pH, aging time, and calcination conditions. The optimized preparation conditions were chosen by measuring removal efficiencies of isopropyl alcohol as a representative target compound with supportive SEM and XRD analyses. Removal efficiencies with photocatalyst and UV irradiation in synthetic wastewater simulating electronics wastewater were evaluated over time. Removal efficiencies of alcohol, acetone, ethanol, and acetaldehyde reached 97.2%, 71.2%, 99.0%, and 99.0%, respectively, in 2 h. Reaction constants of each compound were determined by fitting experimental data to the first order kinetic equation and the trial and error method with consecutive reaction pathway. As analysis results of reaction constants, UV with prepared photocatalyst was found to be effective and the decomposition of acetone was found to be the rate-determining step. The immobilized photocatalyst developed in this study would be useful for application of wastewater reuse with high removal efficiencies, mild preparation conditions, and mechanical stability.