Future Problems
Adsorption of fluid at above-critical temperatures and elevated pressures is a field growing importance in both science and engineering. It is the physicochemical basis of many engineering processes and potential industrial applications. For example, separation or purification of light hydrocarbons, storage of fuel gases in microporous solids, adsorption from supercritical gases in extraction processes and chromatography. Besides, knowledge of gas/solid interface phenomenon at high pressures is fundamental to heterogeneous catalysis. However, the limited number of reliable high-pressure adsorption data hampered the progress of the theoretical study.
At least two problems have to be solved before a consistent system of theories for supercritical adsorption becomes sophisticated: first, how to set up a thermodynamically standard state for the supercritical adsorbed phase, so that the adsorption potential for supercritical adsorption can be evaluated? Second, how to determine the total amount in the adsorbed phase based on experimentally measured equilibrium data. Determination of the absolute adsorption is needed for establishing thermodynamic theory because as a reflection of statistical behavior of molecules, thermodynamic rules must rely on the total, not part of, material confined in the system studied.
From recent studies of supercritical adsorption, there seems to be an end in the high-pressure direction for supercritical adsorption. However, adsorbed-phase density is the decisive factor for the existence of this end. The state of adsorbate at the “end” provides the standard state of the supercritical adsorbed phase just like the saturated liquid, which is the end state of adsorbate in the subcritical adsorption. So the “end state” has to be precisely defined. To establish a definite relationship for the adsorbed phase density at the end state, abundant and reliable experimental data are still required.
Read more about this topic: Supercritical Adsorption
Famous quotes containing the words future and/or problems:
“Our system of government, in spite of Vietnam, Cambodia, CIA, Watergate, is still the best system of government on earth. And the greatest resource of all are the 215 million Americans who still have within us the strength, the character, the intelligence, the experience, the patriotism, the idealism, the compassion, the sense of brotherhood on which we can rely in the future to restore the greatness to our country.”
—Jimmy Carter (James Earl Carter, Jr.)
“Grandparents can be role models about areas that may not be significant to young children directly but that can teach them about patience and courage when we are ill, or handicapped by problems of aging. Our attitudes toward retirement, marriage, recreation, even our feelings about death and dying may make much more of an impression than we realize.”
—Eda Le Shan (20th century)