Hertanto Adidharma

A crossover equation of state for associating fluids

In this work we extend the crossover (CR) modification of the statistical-associating-fluid-theory (SAFT) equation of state (EOS), recently developed and applied for non-associating systems [Ind. Eng. Chem. Res. 38 (1999) 4993] to associating fluids. Unlike the previous crossover EOS that was based on the parametric linear model for the universal crossover function Y, the new CR SAFT EOS is based on Fisher’s recent parametric sine model. This model can be extended into the metastable region and gives analytically connected van der Waals loops in the two-phase region. We show that for associating fluids the new CR SAFT EOS not only yields a better description of the PVT and VLE properties of fluids in the critical region, but also improves the representation of the entire thermodynamic surface. A comparison is made with experimental data for pure normal methanol, ethanol, propanol, butanol, pentanol, and hexanol in the one- and two-phase regions. The CR SAFT EOS reproduces the saturated pressure and liquid density data with an average absolute deviation (AAD) of about 1%. In the one-phase region, the CR SAFT equation represents the experimental values of pressure with an AAD less than 1% in the critical and supercritical region and the liquid densities with an AAD of about 2%.

A study of square-well statistical associating fluid theory approximations

Six square-well (SW) statistical associating fluid theory (SAFT) models, fitted to the experimental saturated liquid volume and saturated vapor pressure for pure n-alkanes, are analyzed for predicting the coexisting densities, second virial coefficients, and binary phase equilibria. The models that result in low values of the segment energy and weak molecular weight dependence of the parameters are found to be more accurate for real fluids. The inclusion of the dimer structure in the SW chain term seems to produce no significant benefit for representing real substances.

Square-well SAFT equation of state for homopolymeric and heteropolymeric fluids

Abstract The square-well-fluid thermodynamics and liquid structure derived from Barker–Hendersons perturbation theory, including a truncation correction, are used within a SAFT (statistical associating fluid theory) framework to develop an equation of state for real chain fluids. The pure-alkane vapor pressure, liquid density, critical region, and heat capacity are found to be more accurate than those correlated with other equations of state, and the parameters are well behaved and, hence, easy to estimate. Also the mixture properties are found to be well represented without much fitting.

Prototype of an LJ solid equation of state applied to argon, krypton and methane

A prototype of an equation of state for Lennard-Jones solids is developed on the basis of modified Weeks-Chandler-Andersen perturbation theory. This prototype is found to represent the melting pressures and molar volumes of solid argon, krypton and methane.

Computation-predicted, stable, and inexpensive single-atom nanocatalyst Pt@Mo2C – an important advanced material for H2 production

The finding that transition metals on Mo2C-supported nanocatalysts are promising for water-gas shift (WGS) reactions at room temperature has generated much excitement. However, the progress achieved with computational chemistry in this area is far behind that of experimental studies. Accordingly, density functional theory (DFT) calculations have been used to design the catalytic activity center structure and study the stabilities and catalytic performances of transition metals doped on β-Mo2C(001) surfaces. A new catalyst that comprises atomically dispersed Pt over Mo2C was designed using DFT. The bimetallic Mo2C surfaces doped with single metal Pt exhibit catalytic activities similar to those of the Pt systems for WGS, while demonstrating the advantages of lower costs and higher thermal stabilities. Importantly, the Pt@Mo2C catalyst is more efficient than the pure Pt catalyst for H2 production under the same reaction conditions. Meanwhile, the density of active sites of Pt@Mo2C(001) for H2 production is considerably increased due to its highly dispersed Pt structure. Therefore, Mo and Pt can synergistically increase H2 production. These findings are significantly beneficial for establishing the relationship between the structure and characteristics of the catalyst, understanding the catalytic activities of single-atom catalysts, and gaining insight into the feasibility of developing substitutes for expensive noble metal catalysts.

Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30

Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T(∗) ≤ 1.20) and high densities (0.96 ≤ ρ(∗) ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

Study of thermodynamic properties of symmetric and asymmetric electrolyte systems in mixture with neutral components: Monte Carlo simulation results and integral equation predictions

Monte Carlo simulation is conducted to obtain the structure, excess internal energy and Helmholtz energy for systems containing charged and neutral hard spheres of comparable concentrations. The results are compared with the thermodynamic properties predicted by solving Ornstein–Zernike equation with hypernetted chain (HNC) and mean spherical approximation (MSA) closures. The HNC approximation is found to well represent the simulation results for both structure and excess energy, while the excess energy of MSA deviates from the simulation results in the intermediate- and high-density range. A simple modification of MSA, referred to as KMSA, is proposed to accurately predict the excess internal and Helmholtz energy in the studied density range. KMSA is proved to capture the effects of neutral component, size and charge asymmetry, system temperature and dielectric constant of the background solvent, on the excess energy of electrolyte systems.

Recovery of rare earth elements with ionic liquids

Rare earth elements (REEs) are in high demand as critical materials in modern green and other advanced technologies. This review focuses on the recovery of REEs from waste with ionic liquids (ILs) as green dilutants and extractants to tackle the REE supply challenge. Extraction mechanisms in different extraction systems, including pure ILs, non-functional ILs with extractants, and functional ILs, are discussed in depth. The IL-based extraction process is different from the traditional molecular solvent-based extraction process. In addition, stripping is crucial to recovering ILs, and supercritical CO2 (Sc-CO2) is introduced to recover REE complexes from the IL phase. Also, Sc-CO2 can accelerate the whole extraction process by enhancing mass transfer. The challenge is to understand the extraction mechanism of the IL/Sc-CO2 system to advance the green recovery of REEs from waste.

Recent progress in improving the stability of copper-based catalysts for hydrogenation of carbon–oxygen bonds

The quickly increasing demand for sustainable energy and materials requires researchers to develop highly efficient and stable catalytic materials for the hydrogenation of carbon–oxygen bonds into chemicals and fuels. Cu-based catalysts have been attracting tremendous attention in gas-phase catalytic reactions, such as the water-gas shift, CO oxidation and NOx reduction reactions. In particular, the C–O bond hydrogenation reaction is an economical and environmentally friendly way to produce alcohols. However, the instability of Cu-based catalysts has become a great challenge for industrial application. The majority of publications discuss the instability of Cu-based catalysts for reactions involving the hydrogenation of dimethyl oxalate, methyl acetate, furfural, or CO2 to alcohols. This review briefly summarizes the roots of Cu-based catalyst deactivation and introduces five strategies for improving their stability, as well as the evolution of copper species during preparation and reaction and a novel Cu-based catalyst technology.

Catalyst-TiO(OH)2 could drastically reduce the energy consumption of CO2 capture

Implementing Paris Climate Accord is inhibited by the high energy consumption of the state-of-the-art CO2 capture technologies due to the notoriously slow kinetics in CO2 desorption step of CO2 capture. To address the challenge, here we report that nanostructured TiO(OH)2 as a catalyst is capable of drastically increasing the rates of CO2 desorption from spent monoethanolamine (MEA) by over 4500%. This discovery makes CO2 capture successful at much lower temperatures, which not only dramatically reduces energy consumption but also amine losses and prevents emission of carcinogenic amine-decomposition byproducts. The catalytic effect of TiO(OH)2 is observed with Raman characterization. The stabilities of the catalyst and MEA are confirmed with 50 cyclic CO2 sorption and sorption. A possible mechanism is proposed for the TiO(OH)2-catalyzed CO2 capture. TiO(OH)2 could be a key to the future success of Paris Climat e Accord.The notoriously slow kinetics in CO2 desorption hinders the development of efficient CO2 capture technologies. Here, the authors discover that nanostructured TiO(OH)2 as a catalyst is capable of dramatically increasing the rates of CO2 desorption from spent monoethanolamine.