Liquid Alkanes Research Articles

Production of renewable petroleum refinery diesel and jet fuel feedstocks from hemicellulose sugar streams

We demonstrate how hemicellulose-derived C5 sugars can be converted into a high-quality petroleum refinery feedstock by a four-step catalytic process. The substitute petroleum consists of normal, branched and cyclic alkanes up to 31 carbons in length and is similar in composition to feedstocks produced in a petroleum refinery today from crude oil. This process can be tuned to adjust the size of the liquid alkanes. In the first step furfural is produced from the acid-catalyzed dehydration of hemicellulose-derived sugar streams in a biphasic reactor. The second step is the aldol condensation of furfural with acetone in a THF solvent and using a NaOH catalyst to produce highly conjugated C13 compounds along with some oligomeric adducts formed through Michael addition reactions. These compounds are then hydrogenated with a Ru/Al2O3 catalyst forming both the fully hydrogenated form of the C13 oligomers and also forming larger oligomers by Diels–Alder reactions. The extent of Diels–Alder reactions can be tuned by changing the temperature and feed concentration, thereby adjusting the distribution of liquid alkanes that can be produced. The final step in this process is hydrodeoxygenation using a Pt/SiO2–Al2O3 bifunctional catalyst to produce the liquid alkanes. A simple biorefinery model has shown that about 55% of a furfural–acetone mixture (10 : 3 wt ratio) can be converted into cycle oils while also producing other refinery products such as gasoline and natural gas.

Long perfluoroalkyl chains are not required for dynamically oleophobic surfaces

Dynamically oleophobic surfaces for alkane liquids, such as n-decane, n-dodecane and n-hexadecane, were successfully prepared using a simple sol–gel mixture containing 3,3,3-trifluoropropyltrimethoxysilane (FAS3) and tetramethoxysilane (TMOS). Due to the enhancement of the motion of functional groups by addition of TMOS as a molecular spacer, small volume alkane droplets (3 μL) could be easily set in motion to move across and off our hybrid surfaces without pinning at low tilt angles (∼10°), and without relying on conventional surface roughening and long-chain perfluoroalkylsilanes.

Novel Transparent Zirconium-Based Hybrid Material With Multilayered Nanostructures: Studies of Surface Dewettability Toward Alkane Liquids

We have successfully prepared unique inorganic-organic hybrid materials that demonstrate excellent transparency and dewettability toward various alkane liquids (n-hexadecane, n-dodecane and n-decane) without relying on conventional surface roughening and perfluorination. Such coatings were made using a novel family of hybrid materials generated by substituting carboxylic acids, with a range of alkyl chain lengths (CH(3)(CH(2))(x-2)COOH where x = total carbon number, i.e., 10, 12, 14, 16, 18, 22, or 24, into zirconium (Zr) tetra-propoxide complexes. This precursor was then mixed with acetic acid and spincast to produce transparent thin Zr-carboxylic acid (ZrCA(x)) hybrid films using a nonhydrolytic sol-gel process. Fourier transform infrared spectroscopy provided proof of Zr-O-Zr network formation in the films upon casting and also followed changes to the physical nature (liquid-like or solid-like) of the alkyl chain assemblies depending upon alkyl chain length. X-ray diffractometry revealed that the hybrid films prepared using the longer chain carboxylic acids (ZrCA(x≥18)) spontaneously self-assembled into lamella structures with d-spacings ranging from 29.5 to 32.7 Angstroms, depending on the length of the alkyl chain. On the other hand the remaining films (ZrCA(x<18)) showed no such ordering. Moreover, the dynamic dewetting behavior of our hybrid films with alkane liquids was also strongly affected by alkyl chain length. ZrCA(x) films with x = 12, 14, and 16 showed the best dynamic oleophobicity among the seven hybrid films. In particular, small volume alkane droplets (5 μL) could be easily set in motion to move across and off ZrCA(14) film surfaces without pinning at low tilt angles (~6°).

How To Reduce Resistance to Movement of Alkane Liquid Drops Across Tilted Surfaces Without Relying on Surface Roughening and Perfluorination

Alkylsilane-derived monolayer-covered surfaces generally display a reasonably good level of hydrophobicity but poor oleophobicity. Here, we demonstrate that the physical attributes of alkylsilane-derived surfaces (liquid-like or solid-like) are dependent on the alkyl chain length and density, and these factors subsequently have significant influence upon the dynamic dewetting behavior toward alkanes (C(n)H(2n+2), where n = 7-16). In this study, we prepared and characterized hybrid films through a simple sol-gel process based on the cohydrolysis and co-condensation of a mixture of a range of alkyltriethoxysilanes (C(n)H(2n+1)Si(OEt)(3), where n = 3, 6, 8, 10, 12, 14, 16, and 18) and tetramethoxysilane (TMOS). Surprisingly, when the carbon number (C(n)) of alkyl chain was 10 and below, the produced hybrid films were all smooth, highly transparent, and showed negligible contact angle (CA) hysteresis. On these hybrid surfaces, 5 μL drops of alkanes (n-hexadecane, n-dodecane, and n-decane) could move easily at low tilt angles (<5°) without pinning. On the other hand, when the C(n) exceeded 12, both transparency and mobility of probe liquids significantly worsened. In the former case, TMOS molecules played key roles in both forming continuous films (as a binder) and improving flexibility of alkyl chains (as a molecular spacer), resulting in the smooth liquid-like surfaces. Silylation of the hybrid film and subsequent dynamic CA measurements proved the presence of silanol groups on the outermost surfaces and demonstrated that the dynamic dewettability of hybrid films worsened as packing densities increased. Additionally, solvent effects (high affinity) between the alkyl chains and alkane liquids imparted a more liquid-like character to the surface. Thanks to these simple physical effects, the resistance to the alkane droplet motion across tilted surfaces was markedly reduced. With the longer carbon chains, the chain mobility was strictly inhibited by mutual interactions between neighboring alkyl chains even in the presence of TMOS molecules. The achieved surfaces displayed a solid-like nature along with surface defects, leading to inferior dynamic oleophobicity. Therefore, the critical C(n) of alkyl chain used for determining final dynamic dewetting behavior against alkane liquids was 12. Furthermore, our hybrid surfaces exhibited excellent antifingerprint properties, particularly demonstrating low adhesion and easy removal from the surface.

The Hydrogen Perturbation in Molecular Connectivity Indices and their Application to a QSPR Study

Although chemical graphs do not show the difference between various atoms and electron lone pairs, the use of pseudo-graphs is a remedy. Modified molecular connectivity indices (mMCIs) have been suggested as showing the role of hydrogen atoms that are also useful in distinguishing isomers. A new algorithm for the δv number, the basic parameter of molecular connectivity indices (MCIs), has recently been proposed. This algorithm, which is centered on graph concepts such as complete graphs and general graphs, encodes the information of the bonded hydrogen atom on different atoms through a perturbation parameter that requires no new graph concepts. In this study, hydrogen perturbations in valence molecular connectivity indices were applied as structural descriptors for organic compounds in quantitative structure property relationship studies on the molar volume and molar refraction of liquid alkanes, alkenes and alcohols. The results show that, in most cases, these indices give improved correlations compared with the original MCIs.

Direct formation of gasoline hydrocarbons from cellulose by hydrothermal conversion with in situ hydrogen

A new process based on aqueous-phase dehydration/hydrogenation (APD/H) has been developed to directly produce liquid alkanes (C7–9), which are the main components of fossil gasoline, from cellulose in one single batch reactor without the consumption of external hydrogen (H2). In this new process, part of the cellulose is first converted to in situ H2 by steam reforming (SR) in the steam gas phase mainly; and, in the liquid water phase, cellulose is converted to an alkane precursor, such as 5-(hydroxymethyl)furfural (HMF). In the final reaction step, in situ H2 reacts with HMF to form liquid alkanes through APD/H. Accordingly, this new process has been named SR(H2)-APD/H. Experimental results show that the volumetric ratio of the reactor headspace to the reactor (H/R) and an initial weakly alkaline condition are the two key parameters for SR(H2)-APD/H. With proper H/R ratios (e.g., 0.84) and initial weakly alkaline conditions (e.g., pH = 7.5), liquid alkanes are directly formed from the SR(H2)-APD/H of cellulose using in situ H2 instead of external H2. In this study, compared with pyrolysis and hydrothermal liquefaction of cellulose at the same temperatures with same retetion time, SR(H2)-APD/H greatly increased the liquid alkane yields, by approximately 700 times and 35 times, respectively. Based on this process, direct formation of fossil gasoline from renewable biomass resources without using external H2 becomes possible.

Positronium bubble in liquid alkanes and alcohols

Ortho-positronium (o-Ps) lifetime in alkanes and alcohols was measured in a broad range of temperatures and the results were compared with calculations in the framework of a standard bubble model. The lifetimes as a function of temperature above the melting point are almost identical for all alkanes. Assuming the potential well depth of 1eV, the best fit of a model curve to the experimental data is obtained for surface tension increased by factor of about 1.4–1.6 comparing to flat surface. If the well depth is larger, this correcting coefficient should be larger too. The difference of decay constants in alcohol and alkane of the same chain length at a given surface tension is small; it can be ascribed to the traces of radiation chemical reactions, or to nonequal potential well depths.

A Physical Approach To Specifically Improve the Mobility of Alkane Liquid Drops

Seamless control of resistance to liquid drop movement for polar (water) and nonpolar alkane (n-hexadecane, n-dodecane, and n-decane) probe liquids on substrate surfaces was successfully demonstrated using molten linear poly(dimethylsiloxane) (PDMS) brush films with a range of different molecular weights (MWs). The ease of movement of liquid drops critically depended on polymer chain mobility as it relates to both polymer MW and solvent swelling on these chemically- and topographically identical surfaces. Our brush films therefore displayed lower resistances to liquid drop movement with decreasing polymer MW and surface tension of probe liquid as measured by contact angle (CA) hysteresis and tilt angle measurements. Subsequently, while mobility of water drops was inferior and became worse at higher MWs, n-decane drops were found to experience little resistance to movement on these polymer brush films. Calculating CA hysteresis as Δθ(cos) = cos θ(R) - cos θ(A) (θ(A) and θ(R) are the advancing and receding CAs, respectively) rather than the standard Δθ = θ(A) - θ(R) was found to be advantageous for estimation of the actual dynamic dewetting behavior of various probe liquids on an inclined substrate.

Quantitative study of diffusion jumps in atomistic simulations of model gas–polymer systems

Microscopic mechanisms underlying the diffusion of particles in polymeric and other systems include ‘jumps’ that are said to provide for a substantial contribution to the overall particle displacement. Such jumps have been observed in molecular simulations and experimentally, leading to important qualitative conclusions. An efficient method has been proposed for the identification and quantitative processing of jumps, and successfully employed in simulations of gas–liquid alkane systems. In the present work, the same method is applied in equilibrium Molecular Dynamics simulations of methane-like molecules dispersed in polymer-like alkanes, at atmospheric pressure and temperature well above the polymer melting point. The systems studied were prepared and equilibrated and a linear diffusion regime was confirmed by means of various criteria. The occurrence of distinct jump events was clearly revealed and their average length and frequency were calculated. In this way, a random-walk-type diffusion coefficient, D s, jumps, of the penetrants, was obtained and found to be lower than the overall diffusion coefficient D s, MSD calculated by the mean square displacement method. This is a strong indication that the overall diffusion is a combination of longer jumps with other microscopic mechanisms such as smoother and more gradual displacements effected upon the diffusing particle by its surroundings.

Theoretical studies for the formation of γ-valero-lactone from levulinic acid and formic acid by homogeneous catalysis

The γ-valero-lactone (GVL), a potential ‘green’ candidate for the production of liquid alkanes for transportation fuels, can be obtained by the hydrogenation of levulinic acid, a primary decomposition product of hexoses. On the search for the application of a bifunctional catalyst, we have identified that the versatile Shvo catalyst can be used to transfer the hydrogen required for the reduction of levulinic acid to GVL through a 2-hydroxy-pentanoic acid (2HP) intermediate. Density functional studies (DFT) have been employed here to compute the energetics for the conversion of levulinic acid to GVL. Additionally, we have investigated the potential application of an iron-based congener to replace the conventional Shvo catalyst due to its natural abundance and cost effectiveness.

Gas-liquid transfer data used to analyze hydrophobic hydration and find the nature of the Kauzmann-Tanford hydrophobic factor

Hydrophobic free energy for protein folding is currently measured by liquid-liquid transfer, based on an analogy between the folding process and the transfer of a nonpolar solute from water into a reference solvent. The second part of the analogy (transfer into a nonaqueous solvent) is dubious and has been justified by arguing that transfer out of water probably contributes the major part of the free energy change. This assumption is wrong: transfer out of water contributes no more than half the total, often less. Liquid-liquid transfer of the solute from water to liquid alkane is written here as the sum of 2 gas-liquid transfers: (i) out of water into vapor, and (ii) from vapor into liquid alkane. Both gas-liquid transfers have known free energy values for several alkane solutes. The comparable values of the two different transfer reactions are explained by the values, determined in 1991 for three alkane solutes, of the cavity work and the solute-solvent interaction energy. The transfer free energy is the difference between the positive cavity work and the negative solute-solvent interaction energy. The interaction energy has similar values in water and liquid alkane that are intermediate in magnitude between the cavity work in water and in liquid alkane. These properties explain why the transfer free energy has comparable values (with opposite signs) in the two transfers. The current hydrophobic free energy is puzzling and poorly defined and needs a new definition and method of measurement.

On the Spontaneous Formation of Clathrate Hydrates at Water–Guest Interfaces

The formation of hydrates, cage-like water-gas structures, is of tremendous importance both in industries and research. Although of major significance, the formation process is not completely understood so far. We present a comprehensive study of hydrate formation at liquid–liquid interfaces between water and isobutane, propane, carbon dioxide, and at the liquid–gas interface between water and xenon. We investigated the structure of these interfaces under quiescent conditions in situ by means of X-ray reflectivity measurements both inside and outside the zone of hydrate stability. At the interfaces between water and liquid alkanes, no evidence for a structural change was found. In contrast, the accumulation of guest molecules inside nanothick interfacial layers was observed at the water–xenon and liquid–liquid water–CO2 interfaces. We show that only those systems initially exhibiting such guest-enriched interfacial layers developed into macroscopic gas hydrates within our observation times (∼12 h). Therefore, these layers act as triggers for the spontaneous formation of macroscopic hydrates.

Derivation and systematic validation of a refined all-atom force field for phosphatidylcholine lipids.

An all-atomistic force field (FF) has been developed for fully saturated phospholipids. The parametrization has been largely based on high-level ab initio calculations in order to keep the empirical input to a minimum. Parameters for the lipid chains have been developed based on knowledge about bulk alkane liquids, for which thermodynamic and dynamic data are excellently reproduced. The FFs ability to simulate lipid bilayers in the liquid crystalline phase in a tensionless ensemble was tested in simulations of three lipids: 1,2-diauroyl-sn-glycero-3-phospocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dipalmitoyl-sn-glycero-3-phospcholine (DPPC). Computed areas and volumes per lipid, and three different kinds of bilayer thicknesses, have been investigated. Most importantly NMR order parameters and scattering form factors agree in an excellent manner with experimental data under a range of temperatures. Further, the compatibility with the AMBER FF for biomolecules as well as the ability to simulate bilayers in gel phase was demonstrated. Overall, the FF presented here provides the important balance between the hydrophilic and hydrophobic forces present in lipid bilayers and therefore can be used for more complicated studies of realistic biological membranes with protein insertions.

Turning on the triplet state channel in the excess electron scavenging by nitroxyl radicals in liquid alkanes

It has been found that the effective radius of the reaction of excess electrons capture by 4-phenyl-2,2,3,5,5-pentamethyl-imidazolidin-1-oxyl in n-dodecane, n-decane, and n-hexane increases steeply by a factor of about four, reaching values typical for molecular acceptors, when the temperature is reduced below 290, 280, and 250, respectively. A kinetic model of the capture that is based on the assumption of equilibrium between electron detachment and intersystem crossing in the triplet state of the diradical anion is suggested and briefly discussed.

Hydrodeoxygenation of vegetable oils to liquid alkane fuels over Ni/HZSM-5 catalysts: Methyl hexadecanoate as the model compound

Abstract Ni/HZSM-5 catalysts with different Ni loadings were prepared by impregnation method, and their catalytic performance was evaluated in the hydrodeoxygenation (HDO) upgrading of the model reactant methyl hexadecanoate (MHD) to liquid alkane fuels. The physicochemical properties of the catalysts were characterized by XRD, SEM, NH3-TPD, and BET. Ni loadings were obviously influenced by the acidity, and thus significantly affected their catalytic performance. Over 7 wt.% Ni/HZSM-5 catalyst, MHD conversion of more than 90% and total liquid C5–C16 hydrocarbon selectivity of 83% were obtained under the optimum reaction condition, possibly due to the synergistic effect of metal Ni and acid HZSM-5.

Correlation of Pt–Re surface properties with reaction pathways for the aqueous-phase reforming of glycerol

The surface properties of Pt–Re catalytic nanoparticles supported on carbon following exposure to a hydrogen reducing environment and subsequent hydrothermal conditions have been studied using in situ X-ray photoelectron spectroscopy (XPS) and ammonia temperature-programmed desorption (TPD). These properties have been correlated with the catalyst selectivity for the aqueous-phase reforming of glycerol. We show that Pt in reduced Pt–Re/C becomes electron deficient, and a fraction of the Re becomes oxidized when the catalyst is subsequently exposed to hydrothermal reaction conditions. Oxidation of Pt–Re generates surface acidity, which drastically affects the reaction pathways. The acid site concentration, but not acid site strength, increases with Re loading. This acidity increase with Re addition favors C–O over C–C cleavage, which results in higher selectivity to liquid products and alkanes at the expense of hydrogen selectivity. We propose a model for the Pt–Re active site and the origin of acidity enhanced by the addition of Re.

Study of the products of benzene transformation in the presence of argon, hydrogen, and propane-butane mixture in barrier discharge

The conversion of benzene in a medium of Ar, H2, and propane-butane mixture in a dielectric-barrier discharge reactor, accompanied by polymerization yielding liquid and solid compounds, has been investigated. The amount of polymerization products reaches 79.7 wt %. Addition of H2 to benzene reduces the amount of benzene-soluble polymer-like compounds in the products to ∼61 wt % and precludes the formation of solid polymerization products. The transformation of benzene with a propane-butane mixture yields alkylbenzenes (up to 38.5 wt %) and liquid alkanes (to 20.5 wt %, mainly with a branched structure). It has been found that an increase in benzene flow rate from 0.08 to 0.4 cm3/min in the case of benzene conversion with the propane-butane mixture can significantly reduce the amount of polymerization products from 56.7 to 9.1 wt %.

Coarse Grained Ion-Ion and Ion-Water Interactions

A detailed knowledge of ion transfer mechanisms between water and low-polarity media is crucial for many areas of chemistry and biochemistry such as phase transfer catalysis, separations, and biomembranes. [1,2] It has become clear from experiments [3] and simulations[4] that the transfer of small hydrophilic ions from water to an immiscible organic liquid is typically accompanied by the co-transfer of several water molecules. As a result, the ion exists in the organic phase as a hydrated cluster. To properly simulate biological phenomena at the coarse grained (CG) level, a proper treatment of the hydrated ions and solvent is crucial and is nontrivial. We have recently parameterized an uncharged and 4:1 mapped CG water with 3 interaction sites based on a generalized Morse -like potential which has greater flexibility in tuning the landscapes of CG effective pairwise potentials. [5] This new CG water becomes polarizable when it interacts with ions (Na+, Cl-) and or any other charged sites but not among its own species. The Morse interaction parameters for the CG ion-ion, ion-water, and ion-alkane are to be parameterized against the free energy of transfer of ions between water and liquid alkanes as well as radial distributions of ion-ion and ion-water. The target data are to be derived from atomic simulations.

J053034 直鎖アルカン飽和液中の熱エネルギー伝搬機構に関するAll-Atom分子動力学シミュレーション

This report mentions non-equilibrium molecular dynamics (MD) simulation of heat conduction in alkane liquids. In the previous study, the authors have analyzed the molecular mechanism of heat conduction in liquid n-alkanes ofvarious molecular lengths by utilizing the united-atom model. Although the results were satisfactorily reasonable, the influence of C-H bonds was not clarified because the bonds were ignored in the united atom model. To analyze the influence, a non-equilibrium MD simulation was performed in the present study for heat conduction in liquid n-alkanes applying an all-atom model. The influence of the presence of H sites and the contributions of the C-H bond were examined.

Modeling of DNA thermophoresis in dilute solutions using the non-equilibrium thermodynamics approach

Our previous approach on thermodiffusion modeling of dilute polymer solutions is extended to dilute DNA solutions. The model is based on linear non-equilibrium thermodynamics and the concept of Eyring's activation energy of viscous flow to estimate the Soret coefficient in thermophoresis of macromolecules that are not in liquid phase. The net heat of transport of single- and double-stranded DNA molecules, which are in solid state, are replaced by the activation energy of viscous flow of liquid alkanes with comparable molecular weights. The proposed formula is tested against available experimental data and qualitative agreement is observed. For double-stranded DNA molecules, the experimental data are scattered and the model can qualitatively predict the data, whereas for single-stranded DNA experiments in the infinite dilution model, for which the model is prescribed, a very good agreement is observed.