Micromeritics’ ASAP 2020® Accelerated Surface Area and Porosimetry analyzer uses the static volumetric technique to generate high-quality data for research and quality control applications. Available options include the micropore option, the high-vac option, and the hydrocarbon vapor option. The chemisorption version determines the percent metal dispersion, active metal surface area, size of active particles, and surface acidity of catalyst materials. Data obtained by an ASAP 2020 analyzer is used to achieve efficiency, safety, quality, and profitability in any modern materials-oriented work, and can be used by scientists with confidence and assurance.
Catalysts are used in a variety of applications from the production of consumer goods to the protection of the environment. Optimum design and efficient utilization of catalysts require a thorough understanding of the surface structure and surface chemistry of the active material.
Chemical adsorption (chemisorption) analysis techniques provide much of the information necessary to evaluate catalyst materials in the design and production phases, as well as after a period of use. Catalytic activity is evaluated by measuring the amounts and types of reactive gas adsorbed. This volume of gas, along with an understanding of the reaction stoichiometry, is used to calculate metal dispersion, active surface area, size of crystallites, and surface acidity.
Micromeritics instruments are specifically designed for the highly aggressive environment present during chemisorption analysis. Internal components are constructed of highest-quality stainless steel to prevent reactivity with most commonly used chemisorptives. Heated manifolds, gas lines, and detectors are provided to allow analysis with condensable vapors. Sample preparation occurs in situ to prevent contamination prior to analysis. Samples can be prepared at high temperatures (up to 1100 deg C) and at low pressures (<10 -5 mmHg).
- Two Independent vacuum systems that allow preparation and analysis to proceed concurrently,
- Oil-free “dry” vacuum option to prevent oil contamination
- Two-station intelligent degas system for fully automated degassing with controlled heating time profiles, an extra long duration cryogen system for unattended analyses,
- Twelve gas inlets that are automatically selectable to allow for automated selection of pretreatment, backfill, and analysis gases, and the ability to connect to a mass spectrometer.
The basics of the analytical technique are simple; a sample contained in an evacuated sample tube is cooled (typically) to cryogenic temperature, then is exposed to analysis gas at a series of precisely controlled pressures. With each incremental pressure increase, the number of gas molecules adsorbed on the surface increases. The pressure at which adsorption equilibrium occurs is measured and the universal gas law is applied to determine the quantity of gas adsorbed.
As adsorption proceeds, the thickness of the adsorbed film increases. Any micropores in the surface are quickly filled, then the free surface becomes completely covered, and finally larger pores are filled. The process may continue to the point of bulk condensation of the analysis gas. Then, the desorption process may begin in which pressure systematically is reduced resulting in liberation of the adsorbed molecules. As with the adsorption process, the changing quantity of gas on the solid surface is quantified. These two sets of data describe the adsorption and desorption isotherms. Analysis of the isotherms yields information about the surface characteristics of the material.