Mass transfer in continuous mixtures with Maxwell–Stefan diffusion using the adaptive characterization method

The adaptive pseudocomponent characterization method for continuous mixtures was extended to mass transfer problems using the Maxwell–Stefan diffusion model. It is based on the direct quadrature method of moments (DQMoM), using a quadrature rule to discretize the molar fraction distribution of the continuous mixture. The solution method was applied to two one-dimensional mass transfer problems: the transient diffusion in a Loschmidt tube and the steady-state diffusion in a thin film. In the latter, it was showed that the DQMoM equations reduce to an equivalent problem with a fixed characterization and solution methods for linearized theory problems can be employed. For these two problems, the proposed method was verified against the discrete component model (DCM), whose implementation was also verified against existing solutions. Results showed that the adaptive method with five pseudocomponents predicts the mixture properties with maximum relative deviation smaller than 1% when compared to the DCM with 57 components.     

Phase equilibria calculations for ill-defined mixtures using the prsv equation of state

A method for the calculation of vapor-liquid equilibria (VLE) for multicomponent systems using continuous thermodynamics is presented. The Extended Spline Fit Technique (ESFT) is used to represent the molar distribution curve of petroleum fluids. A continuous version of the Peng-Robinson-Stryjek-Vera (PRSV) equation of state (EOS) with Generalized Single Carbon Number Properties (GSCNP) is utilized. For continuously distributed components, following the suggestion of Hendriks (1987), the number of equations solved is reduced through integration over the range of the distributing variable using Legendre-Gauss quadrature. Integrated equations are solved using accelerated successive substitution. Flash, dew and bubble point calculations for an imaginary and a real system yield satisfactory results.     

CONTINUOUS THERMODYNAMICS FOR POLYMER SOLUTIONS II.LATTICE-FLUID MODEL

Using lattice-fluid model,a continuous thermodynamic framework is presented forphase-equilibrium calculations for binary solutions with a polydisperse polymer solute.A two-stepprocess is deslgned to form a real polymer solution containing a solvent and a polydisperse polymersolute occupying a volume at fixed temperature and pressure.In the first step,close-packed purecomponents including solvent and polymers with different molar masses or different chain lengths aremixed to form a closed-packed polymer solution.In the second step,the close-packed mixture,con-sidered to be a pseudo-pure substance is mixed with holes to form a real polymer solution with a vol-ume dependent on temperature and pressure.Revised Freed's model developed previously is adoptedfor both steps.Besides pure-component parameters,a binary size parameter c_r and a binary energyparameter ε_(12) are used.They are all temperature dependent.The discrete-multicomponent approach isadopted to derive expressions for chemical potentials,spinoda     

The use of coal liquefaction catalysts for coal/oil coprocessing and heavy oil upgrading

The catalytic hydrogenation of heavy oil and mixed coal-heavy oil (coprocessing) systems has been the focus of a recent study at the Federal Energy Technology Center (FETC). The intent of this effort was to extend the use of coal liquefaction technologies to heavy oil upgrading and coprocessing systems. Specifically, new dispersed molybdenum-based catalysts developed at FETC and a novel silica-doped hydrous titanium oxide (HTO : Si)-supported NiMo catalyst developed at Sandia National Laboratories (SNL) were tested in these systems. The results indicate the potential of coal liquefaction catalysts for use in coprocessing and heavy oil upgrading. High conversions of coal–oil mixtures were observed with dispersed catalyst loadings as low as 100 ppm Mo. Similar results were observed in heavy oil systems. Also, the novel NiMo/HTO : Si catalyst was at least as effective as commercially-available supported catalysts (e.g. Amocat 1C) for conversion of high boiling point material to distillable products and aromatics removal.     

Uptake of fluids by boreal wood chips: Implications for bioenergy

As part of a long term study of pipeline transport of wood chips for bioenergy applications, we have determined the uptake of two fluids by hardwood and softwood chips from the boreal forest. Water or oil would be the likely carrier fluids in pipelining wood chips for ultimate use as bioenergy (e.g. any of combustion, gasification, pyrolysis to form bio-oil, or fermentation to ethanol). Uptake of water and a heavy gas oil by spruce and aspen poplar wood chips has been measured as a function of immersion time. One unit (mass) of spruce wood chips with an initial moisture level of 53% (wet basis, all percentages expressed as mass %) immersed in water for 48 h absorbs an additional 0.52 units of water to reach a moisture level of 69%, initial water uptake is rapid, with a subsequent very slow increase with time; equilibrium does not appear to have been reached. One unit of spruce chips immersed in heavy gas oil for 48 h absorbs 0.41 units of heavy gas oil to reach an oil content of 29%; uptake of oil is slower than water, and has not reached an equilibrium. Similar figures for aspen poplar are an initial moisture level of 45%, an uptake of an additional 0.57 units of water to reach a moisture level of 65%, and an uptake of 0.51 units of oil to reach an oil content of 34%. For both oil and water, draining in excess of one hour does not reduce the measured uptake of water or oil. The moisture level in wood chips after immersion is not affected by the initial moisture level in the chip; lost water due to drying is quickly reabsorbed. Oil uptake is significantly higher in wood chips that have a lower initial moisture content.     

A COMPARISON OF DISTRIBUTION FUNCTIONS FOR CALCULATION OF PHASE EQUILIBRIA OF CONTINUOUS MIXTURES

Ill-defined fluid mixtures containing too many components for complete analysis are often described in terms of continuous distribution functions of boiling point or molecular weight or in terms of pseudo-components. For many systems, the choice of the pseudo-component method or one of the standard distribution-function approaches can significantly affect the calculated phase equilibria.

For three sample systems, a comparison is made of the pseudo-component method, the method of moments, the Lobatto quadrature method, and our new method in which cubic-spline approximations are incorporated. The accuracy of representation of the composition distribution function is compared, as well as the calculated phase equilibria and CPU times.

Although each method has advantages for specific types of systems and calculations, the cubic-spline method was found, in general, to be most accurate and adaptive, with only slight increases in computation times     

A COMPARISON OF DISTRIBUTION FUNCTIONS FOR CALCULATION OF PHASE EQUILIBRIA OF CONTINUOUS MIXTURES

Ill-defined fluid mixtures containing too many components for complete analysis are often described in terms of continuous distribution functions of boiling point or molecular weight or in terms of pseudo-components. For many systems, the choice of the pseudo-component method or one of the standard distribution-function approaches can significantly affect the calculated phase equilibria.

For three sample systems, a comparison is made of the pseudo-component method, the method of moments, the Lobatto quadrature method, and our new method in which cubic-spline approximations are incorporated. The accuracy of representation of the composition distribution function is compared, as well as the calculated phase equilibria and CPU times.

Although each method has advantages for specific types of systems and calculations, the cubic-spline method was found, in general, to be most accurate and adaptive, with only slight increases in computation times     

Soil burial degradation of new bio‐based additives. Part I. Rigid poly(vinyl chloride) films

Commercial sunflower oil was epoxidized, and the epoxidized sunflower oil (ESO) was used as a thermal stabilizer for poly(vinyl chloride) (PVC). Rigid formulations stabilized with ESO as a new stabilizer and epoxidized soybean oil (ESBO) as a commercial stabilizer for comparison were prepared. The aging of the PVC samples was investigated in landfill soil for 24 months. The structure modifications of the polymer were followed by Fourier transform infrared spectroscopy (FTIR). Furthermore, the variations of density and mechanical properties (tensile and Shore D hardness) were considered. The variations of the mass of the samples, the glass transition temperature (T_g), the molar mass distribution, and the weight loss were followed as a function of time of soil burial. The soil burial test showed the loss of additives by migration and biodegradation that led to the modification of density, mechanical properties, molar mass distribution, and weight loss of the PVC samples. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Multiple steady states in ideal two-product distillation

Simple distillation columns with ideal vapor-liquid equilibrium may display multiple steady-state solutions. Two fundamentally different sources for the multiplicity are presented. Both bring about the unexpected result that increasing reflux makes separation worse in the top part of the column. It corresponds to an unstable operating point. The first type of multiplicity is found for columns with mass or volume inputs (e.g., mass reflux and molar boilup). Even for constant molar flows, the transformation from the actual input units to molar units may become singular (corresponding to a pitchfork bifurcation point), resulting in multiple steady-state solutions. The results are highly relevant in practice, as industrial columns usually have inputs on a mass or volume basis. The second type for specifications on a molar basis (e.g., molar reflux and molar boilup) depends on the presence of an energy balance in the model. The multiplicity is caused by interactions between flows and compositions in the column.     

Enzymatic glycerolysis of soybean oil

Enzymatic glycerolysis of soybean oil was studied. Of the nine lipases that were tested in the initial screening, Pseudomonas sp. resulted in the highest yield of monoglycerides. Lipase from Pseudomonas sp. was further studied for the influence of temperature, thermal stability, enzyme/oil ratio, and glycerol/oil ratio. A full factorial optimization approach was performed. The following conditions were tested over the specified ranges: temperature (30–70°C), thermal stability (30–70°C), enzyme/oil ratio (0.05–0.2 g enzyme/10 g oil), glycerol/oil ratio (1:1–3:1 glycerol/oil molar ratio) and 1 h reaction time. The stability of the enzyme at the reaction temperature was also incorporated as a separate variable. At temperatures above 40°C enzyme denaturation offset the higher activity. The optimal conditions were selected to be the basis for a continuous process: 40°C, a glycerol/oil molar ratio of 2:1, and an enzyme/oil ratio of 0.1 g enzyme/10 g oil. A definition for glycerolysis activity was adopted. The glycerolysis activity (1 GU) was defined as the amount of enzyme necessary to consume 1 μmol of substrate (glycerol and oil) per minute. This research is intended to explore the reaction parameters that are important in a continuous enzymatic glycerolysis process.     

Extraction of free fatty acids from soybean oil using ionic liquids or poly(ethyleneglycol)s

The alternative solvents poly(ethyleneglycol)s (PEGs) with various molar masses and room temperature ionic liquids (RTILs) AMMOENG100 and 1‐butyl‐3‐methylimidazolium dicyanamide (bmimDCA) were studied for the purpose of extraction of linoleic acid from soybean oil. Liquid‐liquid phase equilibrium was measured for binary (PEG + soybean oil), (RTIL + soybean oil) as well as ternary (PEG + soybean oil + linoleic acid), (RTIL + soybean oil + linoleic acid) mixtures, as a function of temperature and composition. The influence on distribution coefficients and separation factor of temperature, initial acid content of the oil and solvent to oil ratio were studied. The effect of molar mass in the case of the PEGs was also examined. The experimental results were modeled using the Peng‐Robinson cubic equation of state coupled with the Mathias‐Klotz‐Prausnitz mixing rule, with good results. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Predicting pressure gradients in heavy oil—water pipelines

Experimental investigations of the flow of water‐heavy oil mixtures at velocities typical of oil‐field gathering systems show that continuous water assisted flow at very low pressure gradients can be achieved. The principal criterion to be satisfied in establishing this desirable flow regime appears to be use of sufficient water, with the velocity also playing a role. It also appears that oil viscosity and water fraction effects on pressure gradient are small provided the beneficial flow regime is established. The flows resemble core‐annular flow, which has been observed previously in Bitumen froth and water‐heavy oil flows, with an oil layer on the pipe wall. However, the correlation for pressure gradient is somewhat different from that reported previously for Bitumen froth flows.     

Sweet potato amylose and amylopectin with narrower distribution of molar mass and chain length obtained by a repeated retrogradation–hydrolysis procedure

The wide molar mass distribution of native starch creates obstacles in investigating the physicochemical characteristics of starch, such as retrogradation, because samples thought to be the same are actually compounds containing many chains with different molar masses. In this paper, the sweet potato amylose and amylopectin isolated from retrograded starch were treated with the retrogradation–hydrolysis method three times, and their physicochemical changes in this process were determined by absorbance of the starch–iodine complex, light microscopy, and molar mass and chain length distributions. The results showed that repeated retrogradation and hydrolysis caused the molar mass distribution of sweet potato amylose and amylopectin to reduce from 4.2 × 10⁷–205 and 7971–223 to 6.0 × 10⁴–730 and 4533–211 g mol⁻¹, respectively. This retrogradation–hydrolysis cut the chain length distribution of sweet potato amylose from DP 9–35 to DP 3–13, but that of amylopectin remained unchanged. The double helix in sweet potato amylopectin will not form if the percentage of chain length with DP ≥ 4 is less than 25%. Repeated retrogradation and hydrolysis was an appropriate method to obtain amylose or amylopectin with a narrower molar mass distribution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43849.     

Polymeric colorants

Polymeric colorants are a group of intermediate or high molar mass compounds that may also be thought of as being intrinsically coloured. As such, they fall into the broader class of inherently useful polymers. Often part of this usefulness arises from the presence of some other attribute than those of colour and high molar mass, e.g. liquid-crystalline character, required hydrophilic/lipophilic balance, ionomer character and so on. In this review the attribute that is emphasised is that of colour within the context of practical applications, synthesis and characterisation. The various classifications are discussed and the relevant background information assessed. The coverage is designed to be reasonably comprehensive and informative. Nevertheless, readers are strongly encouraged to consult the references quoted for further details of specific systems or applications. This review concentrates on the period since 1984, except for its coverage of safety data, which extends over a longer timescale.     

催化裂化油浆的加工工艺及进展

随着原油变重和炼厂掺炼渣油比例的增加，使重油催化裂化装置加工难度增加，并影响了其产品质量及分布。为了提高重油催化裂化装置的加工能力和轻油收率，外甩油浆是改善催化裂化操作的有效手段。油浆作为劣质的重油，催化裂化加工困难。目前油浆用于调和燃料油，但经济效益低。油浆中有相当数量的具有较好裂化性能的烃类，是催化裂化的理想原料，同时富含的稠环芳烃是生产针状焦、增塑剂等高附加值化工产品的原料。本文阐述了催化裂化油浆净化、加氢处理、溶剂脱沥青、溶剂精制、延迟焦化等工艺技术及其发展。     

Eigenschaften thermoplastischer Polyurethanelastomerer in Lösung

Fundamental correlations between the molar mass and the solution viscosity (dimethylformamide (DMF)/1% di-n-butylamine (DBA)) are acquired and discussed on selected polyesterurethanes (PUR-Es) and polyetherurethanes (PUR-Et) with NCO/OH ratios ranging from 955 to 1 030. Static light scattering measurements reveal mass average molar masses in the range 20 000–95 000 g mol^–1; membrane osmometry reveals number average molar masses in the range 15 000–50 000 g mol^–1. Comparative tests with the analytical ultracentrifuge reveal the agreement with respect to the molar mass and the A₂-values; additionally this measurements confirm unimodal Schulz-Zimm molar mass distributions with an average sedimentation constant of S = 1.1 sved (1 sved = 10^–13 s). The results of light scattering und ultracentrifuge measurements show that the solvent mixture DMF/1 wt.-% DBA is well suitable for molar mass measurements and solution viscosity measurements. The linear light scattering Zimm diagram and the sedimentation run exclude microgels and higher molecular associates (for example allophanate and biuret crosslinkage). Because of the good correlation between the determined molar masses and the intrinsic viscosities [η] and the viscosities of the concentrated solutions it was possible to establish a calibration function [η] = K M^a. The exponent a = 0.6–0.9 of the Mark-Houwink-relation indicates that the polymer chains, in diluted solution, are isolated coiled molecules. In concentrated solutions the chains are partly crosslinked, depending on the molar mass. The correlation between the molar mass and the viscosity (Fox-relation) shows an unsteadiness at M_w = 55 000 g mol^–1 (critical molar mass). Above the critical molar mass the solution viscosity increases with the molar mass with an exponent of ϵ = 3.4. Below the critical molar mass of M_w = 55 000 g mol^–1 the solution viscosity increases straight proportional with the molar mass (ϵ = 1).     

中低温煤焦油蒸馏过程中金属元素的迁移规律

以中低温煤焦油轻油和重油为实验原料,采用常压蒸馏获得170~200℃、200~240℃、240~270℃、270~300℃、300~320℃、320~340℃、340~360℃和360~390℃煤焦油馏分油;利用配有油品加氧制冷进样系统的ICP-OES测定了21种微量元素在馏分油中的含量,考察了不同馏分油中元素的分布情况。研究表明：在原煤焦油中,未发现Ag、Mg、Mo、Na、Ni、Fe、Mn、Cr及Ti元素,含量较高的元素有Sn、P、Al、Pb、Si,其中Sn元素在轻油和重油中的含量分别为11.78μg/g和14.04μg/g;在所有馏分油中,未发现Al、Mo、Fe、Mn、Cr及Ti元素,含量比较高的元素有Si、Sn、Na、Zn、Pb,特别是Si、Na、Sn、Zn、Ni、Pb及B元素可以有效富集于馏分油中。可能的原因是Ca、Fe、Mg、Al等金属以不同的盐类形态存在,在煤焦油脱水及<170℃蒸馏过程中,这些金属盐类会被部分带出,导致其在馏分油中的含量未富集或未检出;通过关联金属元素在馏分油中的分布与其组成的关系,馏分油中元素的分布可能与酚类化合物、杂环化合物和蒸馏温度等相关。酚类化合物及杂环化合物可能与Ag、B、Cu、Mo、Sn、Na、Zn、Ca、Pb等金属形成络合物或卟啉配合物,蒸馏温度一方面可以破坏Sn、Cd、Pb、Zn、Cu、Ca、Pb等元素在馏分油中的结合力,另一方面也可以促进这些元素与馏分油中的含氧、含氮等化合物更好地发生化合反应,进而影响金属元素在馏分油中的含量分布。     

Cost-efficient modeling of distributed molar mass and topological variations in graft copolymer synthesis by upgrading the method of moments

Cost-efficient deterministic method of moments solvers, as widely used to calculate average characteristics of chemical processes driven by population variations (e.g., average chain lengths), can be a posteriori extended with approximated solutions delivering distributed properties (e.g., chain length distributions). However, these solutions are rarely verified, specifically for complex systems with many population members and strong coupling, as is the case for industrially relevant free-radical-induced grafting (FRIG) toward graft copolymer (GC) synthesis with monomer unit dependent reactions. FRIG, as studied in the present work with polybutadiene at low styrene conversions, is an important chemical process, for example, the production of compatibilizers and high-impact materials. Deterministic model validation is uniquely performed by benchmarking the low to medium molar mass (MM) results (29 topologies) in the log-molar mass distribution with detailed matrix-based kinetic Monte Carlo simulation output, inherently capable of mapping distributions. The GC product is identified to be a heterogeneous mixture in MM, chemical composition, and molecular topology at any styrene conversion. The molecular structural evolution during GC synthesis is further theoretically related to both one-dimensional size-exclusion chromatography (1D-SEC) and two-dimensional liquid chromatography (2D-LC) analysis. It is shown that conventional SEC—even in the absence of broadening—is insufficient for GC separation, mainly due to the unavoidable coelution of topologically different GC species. In any case, the parallel running of advanced modeling tools allows for detailed molecular interpretation.     

Continuous production of soybean biodiesel with compressed ethanol in a microtube reactor using carbon dioxide as co-solvent

This work investigates the production of fatty acid ethyl esters (FAEE) from the transesterification of soybean oil in supercritical ethanol in a continuous catalyst-free process using carbon dioxide as co-solvent. The experiments were performed in a microtube reactor in the temperature range of 523 K to 598 K, from 10 MPa to 20 MPa, oil to ethanol molar ratio from 1:20 to 1:40, and co-solvent to substrates mass ratio from 0.05:1 to 0.2:1. Results showed that ethyl esters yield obtained increased with increasing addition of carbon dioxide to the system. Considerable reaction yields were achieved at 598 K, 20 MPa, oil to ethanol molar ratio of 1:20 and using a CO₂ to substrate mass ratio of 0.2:1.     

Evaluation of the 1-point quadrature approximation in QMOM for combined aerosol growth laws

This work examines the applicability of various assumptions in implementation of the quadrature method of moments (QMOM) for solving problems in aerosol science involving simultaneous nucleation, surface growth and coagulation. The problem of aerosol growth and coagulation in a box and the problem of vapor condensation in a nozzle are reworked using quadrature method of moments. QMOM uses Gaussian quadrature to evaluate integrals appearing in the moment equations and therefore does not require any assumptions on the form of the size distribution function, the growth laws and coagulation kernels. Results are compared with calculations which assume a lognormal size distribution. The conditions for which one, two and higher quadrature points can be used in the quadrature formula and the issues regarding the accuracy are considered for combined aerosol nucleation, growth and coagulation processes. Results show that for these problems, the simplest 1-point quadrature scheme gives accuracy comparable with the lognormal calculations while using two and higher point quadrature gives highly accurate results. Some difficulties associated with the QMOM are discussed and some insights are provided.