Maceral Separation Laboratory:

John C. Crelling - Department of Geology - Southern Illinois University, Carbondale

Purpose and Scope: In 1984 a Maceral Separation Laboratory based on the DGC technique was started at SIUC with the help of grants from the Illinois Coal Research Board and the U.S. Department of Energy. The facility is now well established and maceral separations are being made on a daily basis. Macerals separated in this facility have been a significant part of over thirty-five research projects supported by over 2 million dollars worth of outside research funding in the last few years. The Maceral Separation Laboratory has two primary purposes:

The first is to serve as a teaching and research laboratory where both undergraduate and graduate students are trained in the various techniques of density gradient centrifugation and other methods of maceral separation.
The other primary purpose is to serve as a research laboratory for faculty members who are engaged in coal research.
A secondary purpose is to provide assistance in the form of consultation and specialized sample separation to faculty members within the university and other scientists outside the university who are engaged in coal and carbon research.

Support: The Coal Characterization Laboratory is supported by the Department of Geology, the Coal Research Center, and external research funding which has exceeded two million dollars over the last twenty years. Collaboration: The research has been conducted by scientists from the Geology Department as well as the departments of Physics, Chemistry, Physiology, and various departments in the College of Engineering. A strong and expanding effort in both national and international collaboration on coal research has always been central to the scope of the Laboratory. This research collaboration has led to publications with colleagues from the following institutions:

NATIONAL:
University of Utah
University of Kentucky
Texas Technical University
Wyoming Geological Survey
Argonne National Laboratory

INTERNATIONAL:
University of Newcastle-upon-Tyne, England
Imperial College, London, England
University of Bath, England
Delft Technical University, Netherlands
Kyushu University, Fukuoka, Japan
Instituto Nacional del Carbon, Oviedo, Spain

Laboratory Facilities - Because macerals vary in their chemistry and structure, they also vary in their density, and it is this variation that allows them to be separated. However, normal sink-float techniques have had only limited success in separating single macerals. This is mainly because the small particle size (10 microns) needed to liberate single macerals and minimize multiple-phase particles is not efficiently separated in the sink-float process. Centrifugation is needed and centrifugation at a large number of densities for a single sample is not practical. A solution to this problem is the use of density gradient centrifugation (DGC) in which a sample is centrifuged through a density continuum and then fractionated (see Figure 1).

Fig. 1
View of Maceral Separation Lab at SIUC

Sample Preparation:
Fluid Energy Mill
Jet Mill
Density Gradient Centrifugation:
2 Beckman J2-21M centrifuges
2 automated fraction collectors
2 Mettler/Parr DMA46 density meters.
Single Density Centrifugation: 1 CEPA Carl Padberg GMBH Semi-continuous centrifuge

Density Gradient Centrifugation:

In this technique the coal sample is reduced to micron size in a fluid energy mill or jet mill and then demineralized with HF and HCl. The sample is then put into a vessel that is filled with an aqueous CsCl density gradient commonly ranging from 1 to 1.6 gms/mL. Gradients up to a density of 2.90 g/ml. can be The vessel is then centrifuged and the particles move to the appropriate density level. At this time the largest vessel in use has a two liter capacity which can process a maximum sample size of two grams of coal. After centrifugation the vessel is fractionated by pumping, then filtered, weighted, and dried. The density and weight of each fraction are measured and plotted. The resulting density profile accurately reflects the maceral composition of the sample (see Figure 2).

Fig. 2
Maceral Separation Process

Types of Materials That Have Been Separated in the DGC Laboratory:
Coal Macerals
Kerogen
Macerals and Matrix from Cannel and Boghead Coals
Carbon Fibers and Carbon Matrix from Carbon-Carbon Composites
Various Components from Automobile Brakes
Various Components from Light Aircraft Brakes
Quinoline Insoluble Components
Fly Ash
Bottom Ash
Carbon Components from Foam Rubber Shoe Inserts
Fullerenes from Soot
Various Components from Chars and Charcoal
Various Components from Carbon Blacks
Various Components from Brake Wear Debris

Typical Applications of Maceral Separation Laboratory Analysis:

Characterization of Pure Maceral Fractions - pure cutinite (see Figure 3 and 4), resinite, sporinite, vitrinite, pseudovitrinite, semifusinite, and fusinite have been separated and characterized both petrographically and chemically (see Figure 5 and 6).

Fig. 3 Separated cutinite maceral in white light (width of the field is 300 micrometers).	Fig. 4 SEM image of separated cutinite macerals.
Fig. 5 Density profile of liptinite macerals in an Illinois Basin coal. The three density peaks from left to right(low to hight density) are respectively cutinite, resinite, and sporinite.	Fig. 6 Results of chemical analysis of maceral fractions separated from the same coal.

Characterization of the Composition of Carbon-Carbon Composites - Analysis of the various components separated from C-C composites allows the composition of the original material to be calculated.
Analysis of the Distribution of Trace Elements in Fly Ash - Trace element analysis of separated density fractions to reveal variations in trace element distribution with density.
Correlation of Density Profiles with Pertographic Composition - Analysis of density distributions profiles shows an excellent correlation to actual petrographic composition (see Figure 7, 8, and 9).

Fig. 7
Density profile of a typical humic coal.
Fig. 8
Density profile of a typical boghead coal.
Fig. 9
Density profile of a typical cannel coal.

Research Services Available:

Custom Separation Research on Coals, Cokes, Carbons, Graphites, and other materials
Petrographic Characterization of Separated Materials

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