Coupling ATR-FTIR spectroscopy with multivariate analysis for polymers manufacturing and control of polymers’ molecular weight

Acrylate-based polymers are commonly used in the chemical industry. Consistent manufacturing of these polymers with the help of Process Analytical Technology (PAT) is very desirable. The capability of monitoring polymers’ molecular weight in real-time reduces operation time and eliminates the frequent samplings needed for quality control. Herein, molecular weight (Mw) of glycidyl methacrylate-co-methyl methacrylate (GMA-co- MMA) copolymer was monitored in real-time using mid-infrared ATR-FTIR spectroscopy. The Principal Component Analysis (PCA) and Partial Least Square (PLS) models were then utilized to examine, improve the latent space, and select high-quality spectra. We show that acquiring highly correlated spectra enhances the robustness of the regression model. The developed models demonstrate a satisfied R2 correlation up to ~87%. This study suggests the potential of robust data-driven techniques for the development of predictive Mw analytics tools

Accurate improvement of a mathematical correlation for estimating diffusion coefficient in gaseous hydrocarbons

Accuracy of Riazi-Whitson mathematical correlation for estimating the molecular diffusion coefficient in gaseous hydrocarbons has been improved, which decreases the absolute average deviation related to the experimental data using About 486 experimental data points that have been collected from latest existing researches. Likewise, re-optimizing, and statistical calculations have been done to synchronize data to avoid unexpected deviations. As shown in present work, deviation values for results of improved correlation from experimental data are less in compare to Riazi-Whitson original correlation. The absolute average deviations for obtained values of improved correlation are about 9.71%, which is about 14% for original mentioned correlation. The input parameters are molecular weight, critical properties, and acentric factors of components in the system; mixture molar density; low-pressure gas viscosity and actual viscosity. The last three properties are calculable by proper correlations in chemical handbooks

Surface Modification of a MXene by an Aminosilane Coupling Agent

MXenes, two-dimensional (2D) transition metal carbides and/or nitrides, possess surface termination groups such as hydroxyl, oxygen, and fluorine, which are available for surface functionalization. Their surface chemistry is critical in many applications. This article reports amine functionalization of Ti3C2Tx MXene surface with [3-(2-aminoethylamino)-propyl]trimethoxysilane (AEAPTMS). Characterization techniques such as X-ray photoelectron spectroscopy verify the success of the surface functionalization and confirm that the silane coupling agent bonds to Ti3C2Tx surface both physically and chemically. The functionalization changes the MXene surface charge from −35 to +25 mV at neutral pH, which allows for in situ preparation of self-assembled films. Further, surface charge measurements of the functionalized MXene at different pH values show that the functionalized MXene has an isoelectric point at a pH around 10.7, and the highest reported positive surface charge of +62 mV at a pH of 2.58. Furthermore, the existence of a mixture of different orientations of AEAPTMS and the simultaneous presence of protonated and free amine groups on the surface of Ti3C2Tx are demonstrated. The availability of free amine groups on the surface potentially permits the fabrication of crosslinked electrically conductive MXene/epoxy composites, dye adsorbents, high-performance membranes, and drug carriers. Surface modifications of this type are applicable to many other MXenes

Study of n-Butyl Acrylate Self-Initiation Reaction Experimentally and via Macroscopic Mechanistic Modeling

This paper presents an experimental study of the self-initiation reaction of n-butyl acrylate (n-BA) in free-radical polymerization. For the first time, the frequency factor and activation energy of the monomer self-initiation reaction are estimated from measurements of n-BA conversion in free-radical homo-polymerization initiated only by the monomer. The estimation was carried out using a macroscopic mechanistic mathematical model of the reactor. In addition to already-known reactions that contribute to the polymerization, the model considers a n-BA self-initiation reaction mechanism that is based on our previous electronic-level first-principles theoretical study of the self-initiation reaction. Reaction rate equations are derived using the method of moments. The reaction-rate parameter estimates obtained from conversion measurements agree well with estimates obtained via our purely-theoretical quantum chemical calculations

Mathematical Modeling of CO2/CH4 Separation by Hollow Fiber Membrane Module Using Finite Difference Method

Removal of CO2 in landfill gas recovery processes and fractured wells as well as its application in enhanced oil recovery and its environmental aspects are of interest. Also separation of CO2 from CH4 in Ethylene Oxide plant is an environmental policy of Marun Petrochemical Company. In the present work, a shell-fed hollow fiber module was modeled mathematically for CO2 separation from CH4. Finite difference method was used for solving the equations. Comparison between co-current and counter-current flow patterns showed that for all conditions, counter current pattern had better efficiency for CO2/CH4 separation. Influence of operating parameters such as feed pressure, permeate pressure, feed flow rate, fiber length and CO2 concentration of feed on separation efficiency of CO2/CH4 mixture was investigated. Also the effect of feed and permeate pressures on required membrane area showed that the membrane area increases by increasing permeate pressure and decreases by increasing feed pressure. The modeling offers valuable data about feasibility study and economical evaluation of a gas separation unit operation as a helpful unit in the industry

Method of Moments Applied to Most-Likely High-Temperature Free-Radical Polymerization Reactions

Many widely-used polymers are made via free-radical polymerization. Mathematical models of polymerization reactors have many applications such as reactor design, operation, and intensification. The method of moments has been utilized extensively for many decades to derive rate equations needed to predict polymer bulk properties. In this article, for a comprehensive list consisting of more than 40 different reactions that are most likely to occur in high-temperature free-radical homopolymerization, moment rate equations are derived methodically. Three types of radicals—secondary radicals, tertiary radicals formed through backbiting reactions, and tertiary radicals produced by intermolecular chain transfer to polymer reactions—are accounted for. The former tertiary radicals generate short-chain branches, while the latter ones produce long-chain branches. In addition, two types of dead polymer chains, saturated and unsaturated, are considered. Using a step-by-step approach based on the method of moments, this article guides the reader to determine the contributions of each reaction to the production or consumption of each species as well as to the zeroth, first and second moments of chain-length distributions of live and dead polymer chains, in order to derive the overall rate equation for each species, and to derive the rate equations for the leading moments of different chain-length distributions. The closure problems that arise are addressed by assuming chain-length distribution models. As a case study, β-scission and backbiting rate coefficients of methyl acrylate are estimated using the model, and the model is then applied to batch spontaneous thermal polymerization to predict polymer average molecular weights and monomer conversion. These predictions are compared with experimental measurements

Sustainable MXenes-based membranes for highly energy-efficient separations

The ease of producing two-dimensional (2D) structure, tunable surface chemistry, and interlayer spacing of MXenes have created innumerable opportunities for researchers to prepare such novel emergent materials as energy-efficient membranes in a variety of engineering separations. In this review, various methods used for the synthesis of MXenes, their functionalization and membrane fabrication are discussed with potential examples. The engineering as well as the design of atomically thin 2D MXene membranes developed over the past decade have played a major role in high-throughput separation areas. The fascinating features of MXenes in terms of ultrathin structure, tunable interlayer distance, versatile chemistry, and appealing physiochemical properties render themselves to be developed as membranes for use in numerous applications, such as in gas separation, liquid separation, and desalination. These applications are critically discussed in this review in terms of their current challenges and future directions as effective emergent membranes in industrial separation processe

Mitigation of Thin-Film Composite Membrane Biofouling via Immobilizing Nano-Sized Biocidal Reservoirs in the Membrane Active Layer

This work investigates the use of a silver-based metal–organic framework (MOF) for mitigating biofouling in forward-osmosis thin-film composite (TFC) membranes. This is the first study of the use of MOFs for biofouling control in membranes. MOF nanocrystals were immobilized in the active layer of the membranes via dispersion in the organic solution used for interfacial polymerization. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) characterization results showed the presence of the MOF nanocrystals in the active layer of the membranes. The immobilization improved the membrane active layer in terms of hydrophilicity and transport properties without adversely affecting the selectivity. It imparted antibacterial activity to the membranes; the number of live bacteria attached to the membrane surface was over 90% less than that of control membranes. Additionally, the MOF nanocrystals provided biocidal activity that lasted for 6 months. The immobilization improved biofouling resistance in the membranes, whose flux had a decline of 8% after 24 h of operation in biofouling experiments, while that of the control membranes had a greater decline of ∼21%. The better biofouling resistance is due to simultaneous improvement of antiadhesive and antimicrobial properties of the membranes. Fluorescence microscopy and FE-SEM indicated simultaneous improvement in antiadhesive and antimicrobial properties of the TFN membranes, resulting in limited biofilm formation

Clean water recycling through adsorption via heterogeneous nanocomposites: Silver-based metal-organic framework embellished with graphene oxide and MXene

Cationic methylene blue (MB) and anionic orange G (OG) dyes were adsorbed using the first-ever synthesized nanocomposite of MXene-AgMOF. At 200 mg/L and 0.01 g, GO-AgMOF, MXene-AgMOF, and AgMOF were able to adsorb 99.9%, 99.0%, and 98.0% of cationic MB dye, respectively, from water. The nanocomposites were characterized both before and after adsorption using different characterization techniques. These nanocomposites show promise as cationic contaminant adsorbents, with an adsorption capacity of 399.9 mg/g for GO-AgMOF. Also, the enhanced adsorption capacity of AgMOF for anionic and cationic dyes suggests its potential use in environmental remediation when combined with MXene