Modeling of liquid hydrocarbon products from syngas

International Journal of Coal Science & Technology - The modeling of hydrocarbon selectivity and CO conversion of the Fischer–Tropsch synthesis over Fe–Ni/Al2O3 catalyst by using...     

Future directions in physiochemical modeling of the thermodynamics of polyelectrolyte coacervates

We review theories of polyelectrolyte (PE) coacervation, which is the spontaneous association of oppositely charged units of PEs and phase separation into a polymer-dense phase in aqueous solution. The simplest theories can be divided into “physics-based” and “chemistry-based” approaches. In the former, PEs are treated as charged, long-chain, molecules, defined by charge level, chain length, and chain flexibility, but otherwise lacking chemical identity, with electrostatic interactions driving coacervation. The “chemistry-based” approaches focus on the local interactions between the species for which chemical identity is critical, and describe coacervation as the result of competitive local binding interactions of monomers and salts. In this article, we show how these approaches complement each other by presenting recent approaches that take both physical and chemical effects into account. Finally, we suggest future directions toward producing theories that are made quantitatively predictive by accounting for both long range electrostatic and local chemically specific interactions.     

Synergistic effect of salt ions and water-soluble amphiphilic compounds of acidic crude oil on surface and interfacial tension

This study investigated the effect of solubility of amphiphilic compounds of acidic crude oil in water on the surface and interfacial tension (IFT) with NaCl, MgCl₂, CaCl₂, and Na₂SO₄ salts. Accordingly, distilled water, along with the salts mentioned in zero ionic strength up to 2 mol were put in contact with crude oil to become saturated with amphiphilic compounds. The effects of these compounds were investigated on the properties of contact water by pH, total organic carbon (TOC), FTIR (Fourier transform infrared spectroscopy), water-air surface tension (ST), and water-n-decane IFT tests. The results showed that some of the organic components of crude oil, especially acidic and basic compounds, are present or soluble in water, which have a significant effect on reducing the surface and IFT. The IFT reduction of water-n-decane was greater than the water-air ST system. Also, the observations showed that for both NaCl and Na₂SO₄ salt water, with increasing ionic strength of water, there was an optimum salinity within the range of 0.1-0.25 mol/L for both salts with the amount of surface and IFT minimized at this point. In the other two salts, this point was delayed upon elevation of ionic strength and was observed at high salinity. In this case, divalent cations reduce tension rate compared to monovalent cations. Due to solubility of acidic and basic groups in water, pH of salt water illustrates an acidic trend. Results of the FTIR test confirmed solubility of these compounds as well.     

Direct synthesis of bi-modal porous structure MCM-41 and its application in CO2 capturing through amine-grafting

A bi-modal porous structure MCM-41 (BPS-MCM-41) was synthesized and functionalized by 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TRI); also, its performance in amine grafting and CO₂ capturing was compared with that of pore-expanded MCM-41 [1]. To create larger pores beside the mesoporous structure of MCM-41, carbon black nanoparticles were used as the solid template. Characterizing the BPS-MCM-41 using the BET and BJH techniques resulted in the surface reduction of 29.3 percent and volume increase of 68.46 percent. The pore size distribution showed two peaks: a narrow peak at 2.24 nm diameter, which belonged to micelles, and a wide one at about 50 nm due to the presence of used nanoparticles. The functionalization confirmed that BPS-MCM-41 is capable of accommodating a large quantity of amine groups. The CO₂ adsorption measurement indicated that internal volume of the adsorbent was a critical factor affecting the adsorption capacity of the amine grafted adsorbents.     

Cell Membrane-Cloaked Nanotherapeutics for Targeted Drug Delivery

Cell membrane cloaking technique is bioinspired nanotechnology that takes advantage of naturally derived design cues for surface modification of nanoparticles. Unlike modification with synthetic materials, cell membranes can replicate complex physicochemical properties and biomimetic functions of the parent cell source. This technique indeed has the potential to greatly augment existing nanotherapeutic platforms. Here, we provide a comprehensive overview of engineered cell membrane-based nanotherapeutics for targeted drug delivery and biomedical applications and discuss the challenges and opportunities of cell membrane cloaking techniques for clinical translation.     

Bioactive Peptides: Synthesis,Sources, Applications,and Proposed Mechanisms of Action

Bioactive peptides are a group of biological molecules that are normally buried in the structure of parent proteins and become active after the cleavage of the proteins. Another group of peptides is actively produced and found in many microorganisms and the body of organisms. Today, many groups of bioactive peptides have been marketed chemically or recombinantly. This article reviews the various production methods and sources of these important/ubiquitous and useful biomolecules. Their applications, such as antimicrobial, antihypertensive, antioxidant activities, blood-lipid-lowering effect, opioid role, antiobesity, ability to bind minerals, antidiabetic, and antiaging effects, will be explored. The types of pathways proposed for bioactive applications will be in the next part of the article, and at the end, the future perspectives of bioactive peptides will be reviewed. Reading this article is recommended for researchers interested in various fields of physiology, microbiology, biochemistry, and nanotechnology and food industry professionals.     

Hydrodynamic and heat transfer properties of magnetic fluid in porous medium considering nanoparticle shapes and magnetic field-dependent viscosity

The purpose of this paper is to study the characteristics of the combined convection heat transfer and a micropolar nanofluid flow passing through an impermeable stretching sheet in a porous medium. The nanofluid flow field is affected by a magnetic field perpendicular to the sheet. The dynamic viscosity of the micropolar nanofluid changes under the influence of the magnetic field. The continuity, linear momentum, angular momentum, and energy equations are first simplified using the order of magnitude technique that, along with the applied boundary conditions and the definition of the appropriate parameters, are transferred to the similarity space using the similarity analysis. Then the resulting equations are solved using the Runge–Kutta method.The distinction of the macroscale and microscale flow fields and temperature fields resulting from different nanoparticle shapes was clarified. Increasing the Hartmann number, the vortex viscosity parameter, the magnetic parameter, the nanoparticle volume fraction, and the permeability parameter of the porous media increased the surface friction on the sheet. Increasing the vortex viscosity parameter, the magnetic parameter, and the volume fraction of the nanoparticles increases the Nusselt number.     

CFD study of non-premixed swirling burners: Effect of turbulence models

This research investigates a numerical simulation of swirling turbulent non-premixed combustion. The effects on the combustion characteristics are examined with three turbulence models: namely as the Reynolds stress model, spectral turbulence analysis and Re-Normalization Group. In addition, the P-1 and discrete ordinate (DO) models are used to simulate the radiative heat transfer in this model. The governing equations associated with the required boundary conditions are solved using the numerical model. The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities. Among different models proposed in this research, the Reynolds stress model with the Probability Density Function (PDF) approach is more accurate (nearly up to 50%) than other turbulent models for a swirling flow field. Regarding the effect of radiative heat transfer model, it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior. This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion.     

Effects of porous material on transient natural convection heat transfer of nano-fluids inside a triangular chamber

This study numerically investigates the impact of porous materials, nano-particle types, and their concentrations on transient natural convection heat transfer of nano-fluid inside a porous chamber with a triangular section. The governing equations of the two-phase mixture model are separated on the computational domain and solved using the Finite Volume Method, taking into account the Darcy–Brinkman model for porous medium. It was observed that convection heat transfer inside the triangular chamber consists of three stages named initial, transient, and semi-steady. The features of each step are provided in detail. The results suggested that the use of a hybrid nano-fluid(water/aluminum oxide-cooper) inside a porous glass material and an increase in volume fraction of nano-particles have adverse effects on heat transfer rate. In contrast, as the nano-particle volume fraction of the single nano-fluid(water/aluminum oxide) inside the chamber increased, convection heat transfer rate improved. At the same time, it was observed that the use of both nano-fluids(single and hybrid) in the porous environment of the aluminum foam could improve convection.