International Journal of Chemical Kinetics最新文献

In the original article published in 2009, Equation (3) after correction was used to determine values of β_n; hence, there are no corrections to values of β_n in Table V.

We apologize for this error.

We present ReactionMechanismSimulator.jl (RMS), a modern differentiable software for the simulation and analysis of chemical kinetic mechanisms, including multiphase systems. RMS has already been applied to problems in combustion, pyrolysis, polymers, pharmaceuticals, catalysis, and electrocatalysis. RMS is written in Julia, making it easy to develop and allowing it to take advantage of Julia's extensive numerical computing ecosystem. In addition to its extensive library of optimized analytic Jacobians, RMS can generate and use Jacobians computed using automatic differentiation and symbolically generated analytic Jacobians. RMS is demonstrated to be faster than Cantera and Chemkin in several benchmarks. RMS also implements an extensive set of features for analyzing chemical mechanisms, including a library of easy-to-call plotting functions, molecular structure resolved flux diagram generation, crash analysis, traditional sensitivity analysis, transitory sensitivity analysis, and an automatic mechanism analysis toolkit. RMS implements efficient adjoint and parallel forward sensitivity analyses. We also demonstrate the ease of adding new features to RMS.

This research investigates the kinetics of methylene blue (MB) discoloration using ambient air cold plasma, with a focus on the impact of agitation speed (100 and 750 rpm). The study revealed pseudo-first-order kinetics for MB discoloration, pinpointing optimal conditions at 35.00°C and 100 rpm. These parameters minimized half-life times, correlated with observed k_obs values. A decreasing pH trend, more pronounced at 750 rpm, was attributed to increased acidic nitrogen species (HNO₃ and HNO₂) production, adversely affecting dye discoloration. Concurrently, enhanced electrolyte concentration was noted from rising conductivity due to plasma production of reactive species followed by solubilization in the aqueous phase. The calculated thermodynamic activation parameters comprised: E_a = 7.96 kJ mol⁻¹, ΔH^‡ = +5.53 kJ mol⁻¹, ΔS^‡ = −253.23 J K⁻¹ mol⁻¹, and ΔG^‡ = +79.77 kJ mol⁻¹ (100 rpm); and E_a = 12.94 kJ mol⁻¹, ΔH^‡ = +13.78 kJ mol⁻¹, ΔS^‡ = −239.06 J K⁻¹ mol⁻¹, and ΔG^‡ = +80.58 kJ mol⁻¹, (750 rpm). The lowest E_a and ΔG^‡ values at 100 rpm reinforced lower agitation favoring the reaction. The study demonstrated a linear decay of the reaction rate constant with the square root of ionic strength. This result, besides the negative activation entropy and moderate activation enthalpy led to a proposition to the determinant step for the transition state formation, involving an associative step between a solvated electron and the protonated substrate. The optimal dye discoloration rate and energy yield were observed at 35.00°C and 100 rpm, with values of 97.2% and 3.371 × 10⁻² g kW⁻¹ h⁻¹, respectively.

Given its role as a primary side product and a potential soft oxidant in the oxidative coupling of methane (OCM), understanding the effect of CO₂ co-feeding on OCM emerges as a key milestone to optimize the process. To grasp the molecular impact of CO₂, a mechanistic investigation over a La-Sr/CaO catalyst was carried out via microkinetic modeling. Seven catalyst descriptors with a precise physico-chemical meaning were regressed for both pure O₂ and CO₂ co-feeding in order to assess eventual structural changes induced in the catalyst by the presence of CO₂ in the feed. Global significance was achieved in both regressions and experimental trends were successfully reproduced by the specifically determined catalyst descriptors. CO₂ co-feeding is deemed responsible for generating a new active phase, for example, by converting metal oxides into (oxy-)carbonates, among others, resulting in a decrease in active site density (D₁₆) from 10 × 10⁻⁵ mol/m² to 7 × 10⁻⁵ mol/m². In the presence of the CO₂-induced phase, the catalyst exhibits higher attraction for unsaturated hydrocarbons as indicated by the higher initial sticking probabilities of CH₃• (D₁₁) and C₂H₄ (D₁₅), which increase from 4.9 × 10⁻⁴ to 8 × 10⁻² and from 2.1 × 10⁻² to 3 × 10⁻², respectively. Additionally, there are also lower the overall energy barriers for the activation of hydrocarbons on the catalyst, stemming from the decrease in the H abstraction enthalpy from CH₄ (D₁) from 14 to 6 kJ/mol. The operating conditions, in particular the O₂ content, are critical in distinguishing the effect of CO₂ co-feeding. While at typical operating conditions, CO₂ promotes the total oxidation of methane, in the prerequisite of reduced amount of O₂, it may also act as an additional oxygen donor. This work provides molecular details on the CO₂ induced changes in catalyst properties but also provides unprecedent quantified insights of the reaction mechanism underlying experimental observations.

Aqueous-phase reforming (APR) is an interesting technique for generating hydrogen (H₂) from biofeeds. In this work, APR of model compounds of wet biomass for H₂ production was investigated. Glycerol, sorbitol, and glycine were the chosen model compounds. They represent polyols and amino acids in wet biomass such as waste sludge and microalgal biomass. The Pt/Al₂O₃ catalyst was preferred and it was characterized using nitrogen adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) techniques. APR trials were performed in a continuous fixed-bed reactor. The reaction conditions chosen for this work were: temperature (T) 453–498 K, pressure (P) 1.2–2.4 MPa, feed concentration 5–15 wt%, and weight hourly space velocity (WHSV) 0.15–0.6 g reactant/(g catalyst h). The best conditions for H₂ production by the APR process were found to be T = 498 K, P = 2.4 MPa, and feed concentration = 15 wt%. Among the chosen model compounds, glycerol exhibited the highest H₂ selectivity (82.7%) and H₂ yield (21.6%) at 498 K. The analysis of kinetic data suggested first-order reaction kinetics for all the model compounds. The values of activation energy for the reactions with glycerol (55.4 kJ/mol), sorbitol (51.6 kJ/mol), and glycine (45.7 kJ/mol) were determined. Thus, APR is a promising route for effectively producing H₂-bearing gaseous products with high heating value from wet biomass.