Aspen molecular weight

Before the raw data can be fitted to a thermodynamic model it must first be converted into mass or mole fractions. This operation can be accomplished quickly using a Microsoft Excel spreadsheet that is linked to the Aspen. aprbkp file in order to obtain the solvent molecular weights and temperature dependent densities. The molar volume of Form A Cimetidine is also required for this conversion, however, as is often the case it was not available so a density of 1 g/ml has been assumed. 

Molecular Weight Distribution of Aspen Lignins Estimated by Universal Calibration... 

This study describes the application of differential vis-cometry as a GPC detector to the problem of determining molecular weight distributions of acetylated hardwood lignins in tetrahydrofuran. Molecular weight distributions of ball-milled, organosolv, alkali-extracted/mild acid hydrolyzed, and alkali-extracted/steam exploded aspen lignins were estimated using universal calibration. 

Figure 2A. Dual chromatograms showing the elution of aspen AESE lignin from the HPSEC-DV system. A 250 fiL sample was injected from a freshly prepared 8 mg /mL stock solution. Viscotek A/D amplifier gain setting of 2 and RI detector setting of lx. Calculated molecular weights are also shown.

Table I illustrates the molecular weight averages found from universal calibration (narrow standards) for four aspen lignins and two quinonemethide-derived polymers using the Unical software. The poly-dispersities were the same within the experimental errors for all lignin samples. In contrast, the polydispersities found for the quinonemethide-derived polymers by universal calibration were near 1.1. The molecular weight averages found for the four acetylated lignins studied by universal calibration were substantially larger than those determined from previous work using conventional GPC (e.g., AESE and BM lignins from refs. 7 and 12 had approximately one-third those values found by HPSEC-DV in the present study).

The process simulation code Aspen-HYSYS 3.2 has been used for residential PEM fuel cell system calculations. Natural gas has been simulated as three different sources for hydrogen production. The chemical compositions of the natural gas fuel are summarized in Table 1. The average molecular weight of natural gas is around 16.6 kg/kmol. All simulation studies are performed based on this composition. 

Because ASPEN is to be used with coal conversion processes, its streams can be designated to carry an arbitrary number of solids or solid phases. This is done by specifying any number of substreams. In fact, the conventional vapor/liquid stream is normally assumed as a substream and solids can comprise other substreams. For the conventional vapor/liquid substream, process data is carried on component molar flows, total molar flow, temperature pressure, specific enthalpy, specific entropy, density, molar vapor fraction, molar liquid fraction, and molecular weight. For solid substreams, which are called "non-conventional substreams," the characterizing data is not as deterministic. The information associated with these substreams is called "attributes". Such attributes may be particle size distribution, ultimate and proximate analyses, or other material specific information. Another type of substream is an "informa-... 

Himmel ME, Tatsumoto K, Oh KK, Grohmann KG, Johnson DK, Chum HL (1989) Molecular weight distribution of aspen lignins estimated by universal calibration In Glasser WG, Sarkanen S (eds) Lignin, properties and materials ACS Symp Ser Vol 397, American Chemical Society, Washington, DC, 82-99... 

In Aspen Plus, solid components are identified as different types. Pure materials with measurable properties such as molecular weight, vapor pressure, and critical temperature and pressure are known as conventional solids and are present in the MIXED substream with other pure components. They can participate in any of the phase or reaction equilibria specified in any unit operation. If the solid phase participates only in reaction equilibrium but not in phase equilibrium (for example, when the solubility in the fluid phase is known to be very low), then it is called a conventional inert solid and is listed in a substream CISOLID. If a solid is not involved in either phase or reaction equilibrium, then it is a nonconventional solid and is assigned to substream NC. Nonconventional solids are defined by attributes rather than molecular properties and can be used for coal, cells, catalysts, bacteria, wood pulp, and other multicomponent solid materials. 

Carbohydrate analysis using enzymatic hydrolysis and subsequent capillary zone electrophoresis (ENZ/CZE) revealed the number of 4-0-methylglucuronic acid units to be approximately one unit per nineD-xylose residues (Table 4). No glucuronic acid units were detected. The carbohydrate composition of the polysaccharide isolated here from aspen wood is quite similar to that previously reported for typical hardwood xylans . SEC analysis indicated the molecular weight (Mw) to be 15000 g/mol. 

Table Molecular Weight Distributions of Acetylafed Aspen Lignin Derivatives in TliP... 

Himmel, M.E. Tatsumoto, K. Grohmann, K. Johnson, D.K. Chum, H.L. Molecular weight distribution of aspen hgnins from conventional gel permeation chromatography, universal cahhration and sedimentation equilibrium. J. Chromatogr. 1990, 498, 93-104. 

For demonstration purposes, other physical properties of this component are entered into Aspen Plus molecular weight, normal boiling point, and Antoine coefficients in the vapor pressure calculation. The molecular weight of EMC can be found from the NIST Chemistry WebBook (see Fig. 3.66). The normal boiling point of 107.9°C is taken from Mueller et al. and the Antoine coefficents are obtained fiom Luo et al. ... 

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