| Three types of membrane films that have been deposited on ceramic supports, carbon, cilica, and alumina films are evaluated for separation potential and durability of coal liquefaction products, including asphaltenes and preasphaltenes in xylenes and tetrahydrofuran. Silica and gamma-alumina films separate based on size exclusion principles and are subject to internal pore fouling asphaltenes and preasphaltenes do not have a specific hydraulic radius or molecular weight. Therefore, silica and gamma-alumina are of little use in separating coal liquefaction products that are typically divided based on solubility characteristics. Carbon films are known to have slit-shaped. Asphaltenes are often viewed as flat sheets of aromatic rings; these molecules may find it easier to permeate through the carbon film and hinder the bulkier preasphaltenes or coal molecules. Carbon films are found to allow for the transport of asphaltene molecules but do not allow for preasphaltenes to permeat. |
