Transesterification of Methyl Acetate with <i>n</i>‑Propanol: Reaction Kinetics and Simulation in Reactive Distillation Process

The reaction kinetics of the transesterification of methyl acetate with <i>n</i>-propanol is described by pseudohomogeneous (PH) kinetic model, which can successfully correlate with the experimental data. The influence of temperature as well as catalyst loading and initial molar ratio of n-propanol to methyl acetate on this reaction is studied under the condition of eliminating both internal and external mass transfer resistances. On the basis of the PH kinetic model, the influences of design parameters are studied, such as recycle flow rate, the number of stages of the reactive distillation column (RD), and theoretical stages of the conventional distillation column. These parameters are further optimized to minimize total annual cost in the RD process

Supplementary Materials from Quasi-steady-state modelling and characterization of diffusion-controlled dissolution from polydisperse spheroidal particles, II: characterization

Some supplementary materials to support the analysis in the main document

Isobaric Vapor–Liquid Equilibrium for the Binary Systems of Diethyl Carbonate with Xylene Isomers and Ethylbenzene at 101.33 kPa

Isobaric binary vapor–liquid equilibrium (VLE) data for diethyl carbonate with ethylbenzene and xylene isomers are measured at 101.33 kPa by using a modified Rose still. The binary VLE data are tested to be thermodynamically consistent by the Herington method and the point-to-point test of the Fredenslund method. Taking account of the nonideality of the vapor phase, the activity coefficients of the components are calculated. All systems present a positive deviation from ideality. The experimental VLE data are well correlated by the nonrandom two-liquid (NRTL), universal quasichemical activity coefficient (UNIQUAC), and Wilson equations. The calculated vapor-phase compositions and temperature agree well with the experimental values. These experimental data can provide basic thermodynamic data for practical application in developing the distillation simulation of diethyl carbonate with ethylbenzene and xylene isomers

Biodiesel Production by Esterification of Oleic Acid over Brønsted Acidic Ionic Liquid Supported onto Fe-Incorporated SBA-15

The esterification of oleic acid with short-chain alcohols using Brønsted acidic ionic liquid supported onto Fe-incorporated SBA-15 (Fe-SBA-15) was studied to develop a green method for biodiesel production. This catalyst was prepared by immobilization of Brønsted acidic ionic liquid 1-(propyl-3-sulfonate)-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate ([SO₃H-PIm-CPMS]­[HSO₄]) onto Fe-SBA-15 (IL/Fe-SBA-15). The structure of the catalyst was characterized by XRD, N₂ adsorption–desorption measurement, FT-IR and TEM. The results demonstrated that Fe was incorporated into the framework of SBA-15, bringing Lewis acidic site. After the ionic liquid was successfully immobilized onto the surface of Fe-SBA-15, the structure of the catalyst remained intact. This catalyst displayed relatively high catalytic activity in esterification of oleic acid with short-chain alcohols because of the synergistic effect of Lewis and Brønsted acidic sites. Under the optimum reaction conditions (reaction temperature 363 K, molar ratio of methanol to oleic acid 6: 1, catalyst amount 5 wt %, and reaction time 3 h), the conversion of oleic acid reached to 87.7% when methanol was used as reactant

Insight of the State for Deliberately Introduced A‑Site Defect in Nanofibrous LaFeO₃ for Boosting Artificial Photosynthesis of CH₃OH

Perovskite-type LaFeO3 is regarded as a potentially efficient visible-light photocatalyst owing to its narrow bandgap energy and unique photovoltaic properties. However, the insufficient active sites and the unsatisfactory utilization of photogenerated carriers severely restrict the realistic application of pure LaFeO3. Herein, we fabricated a series of LaxFeO3−δ nanofibers (x = 1.0, 0.95, 0.9, 0.85, 0.8) with an A-site defect via sol–gel combined with the electrospinning technique. Wherein, the nonstoichiometric La0.9FeO3−δ possessed the highest CH3OH yield of 5.30 μmol·g–1·h–1 with good chemical stability. A series of advanced characterizations were applied to investigate the physicochemical properties and charge-carrier behaviors of the samples. The results illustrated that the one-dimensional (1D) nanostructures combined with the appropriate concentration of vacancy defects on the surface contributed to the radial migration of photogenerated carriers, inhibited the recombination of carriers, and provided more CO2 adsorption-activation sites. Furthermore, density functional theory (DFT) calculations were employed to reveal the influence mechanism of vacancy defects on LaFeO3. This work provides a strategy to enhance the performance of photocatalytic CO2 reduction by modulating the induced oxygen vacancies caused by the A-site defect in perovskite oxides

Altered Inter-Subregion Connectivity of the Default Mode Network in Relapsing Remitting Multiple Sclerosis: A Functional and Structural Connectivity Study

<div><p>Background and Purpose</p><p>Little is known about the interactions between the default mode network (DMN) subregions in relapsing-remitting multiple sclerosis (RRMS). This study used diffusion tensor imaging (DTI) and resting-state functional MRI (rs-fMRI) to examine alterations of long white matter tracts in paired DMN subregions and their functional connectivity in RRMS patients.</p><p>Methods</p><p>Twenty-four RRMS patients and 24 healthy subjects participated in this study. The fiber connections derived from DTI tractography and the temporal correlation coefficient derived from rs-fMRI were combined to examine the inter-subregion structural-functional connectivity (SC-FC) within the DMN and its correlations with clinical markers.</p><p>Results</p><p>Compared with healthy subjects, the RRMS patients showed the following: 1) significantly decreased SC and increased FC in the pair-wise subregions; 2) two significant correlations in SC-FC coupling patterns, including the positive correlation between slightly increased FC value and long white matter tract damage in the PCC/PCUN-MPFC connection, and the negative correlations between significantly increased FC values and long white matter tract damage in the PCC/PCUN-bilateral mTL connections; 3) SC alterations [log(N track) of the PCC/PCUN-left IPL, RD value of the MPFC-left IPL, FA value of the PCC/PCUN-left mTL connections] correlated with EDSS, increases in the RD value of MPFC-left IPL connection was positively correlated to the MFIS; and decreases in the FA value of PCC/PCUN-right IPL connection was negatively correlated with the PASAT; 4) decreased SC (FA value of the MPFC-left IPL, track volume of the PCC/PCUN-MPFC, and log(N track) of PCC/PCUN-left mTL connections) was positively correlated with brain atrophy.</p><p>Conclusions</p><p>In the connections of paired DMN subregions, we observed decreased SC and increased FC in RRMS patients. The relationship between MS-related structural abnormalities and clinical markers suggests that the disruption of this long-distance “inter-subregion” connectivity (white matter) may significantly impact the integrity of the network's function.</p></div

A flowchart of calculating the correlation between structural connectivity and functional connectivity within the default mode network (DMN) subregions.

<p>(1) DMN extraction was performed by ICA. (2) The subregions were extracted as regions of interest (ROIs) within the DMN. (3) The time series in each ROI was extracted with the DMN. (4) The temporal correlation coefficients between each ROI pair were quantified within the DMN. (5) Preprocessed motion and eddy current distortion correction of the model distributions of the relevant parameter (Monte Carlo sampling) was performed using FMRIB's diffusion toolbox (FDT v2.0). (6) Pair-wise ROI (AND logic) probabilistic tractography was used to calculated the distribution of fiber orientations. (7) Features of the long white matter tracts (above threshold 0.2) remaining fiber bundles connecting each pair of ROIs were compared between the two groups, including the strength of a pathway and the above-threshold standard DTI parameters.</p

An example of the long white matter fibers of pair-wise subregions within the default mode network detected by probabilistic tractography in one control subject (a) and one RRMS patient (c) in the native space.

<p>Figures (b) and (d) correspond to 3-dimensional probabilistic tractography. (red: fiber tract, blue: mask of subregions, Sup = Superior, Inf = Inferior, Ant = Anterior, Pos = Posterior).</p

The union of the DMN mask identified and extracted with independent component analysis from RRMS and healthy control groups (LH: left hemisphere; RH: right hemisphere).

<p>The union of the DMN mask identified and extracted with independent component analysis from RRMS and healthy control groups (LH: left hemisphere; RH: right hemisphere).</p

A set of matrices of functional and structural analyses of pair-wise default mode network subregions in the RRMS patient and healthy control (HC) groups.

<p>The figure (a) is a correlation matrix of average time series of subregions (ROIs) in the network (subregion labels are on the left and bottom). The figures (b–s) show the strength of the structural connectivity matrix [of average log (N track) and volumes] of each pair-wise connection. The figures (d–g) are above-threshold (0.2) standard DTI parameters: including the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) of each pair-wise connection. The black arrow indicates increased and the white arrow decreased alteration in the patients with RRMS. Notably, structural connectivity was only compared without the dashed boxes.</p