What is Chemisorption?

Chemisorption is a chemical adsorption process, caused by a reaction on an exposed surface, which creates an electronic bond between the surface and the adsorbate. During the chemical reaction, a distinct chemical species is created on the adsorbent surface, which causes the bond to be created.

Chemisorption is used in development, monitoring and measuring of corrosion inhibitors and is used for measuring surface active sites on a substrate.

During the chemisorption process the adsorbing gas or vapor molecule splits into atoms, radicals, ions that form a chemical bond with the adsorption site. This interaction involves the sharing of electrons between the gas and the solid surface and may be regarded as the formation of a surface compound.

Chemisorption Instruments

We offer two instrumental techniques for chemisorption analysis, the static volumetric technique and the dynamic (flowing gas) technique. The static chemisorption technique is performed by both the Micromeritics 3Flex, and the ASAP 2020 Plus, which operates over a range of pressures.

The dynamic chemisorption technique is utilized by the 3Flex, ChemiSorb, and AutoChem series of instruments. These three instruments utilize pulse chemisorption in a dynamic flow system to titrate the active surface.

Static Chemisorption

In static adsorption, generally two adsorption ‘isotherms’ (quantity of gas adsorbed as a function of pressure at constant temperature) are collected at sub-atmospheric pressures: the first representing total adsorption, the second representing reversible adsorption, and the difference between the two representing the irreversible adsorption (i.e. ‘chemisorption’).
This technique provides information on the quantity of adsorption sites, from which subsequent calculations may be done. When the active surface area analysis is performed at one specific temperature, it is called isothermal chemisorption.

Dynamic Chemisorption

In dynamic chemisorption, the identity, quantity, and strength of active sites can be quantified by adsorption, desorption, or reaction under isothermal or temperature programmed conditions. Dynamic chemisorption utilizes a variety of techniques such as temperature programmed reduction (TPR), oxidation (TPO), desorption (PTD), and pulse chemisorption to characterize active sites in materials.

For the dynamic system, depending on the experiment, a lower concentration of active gas may be in contact with the sample for only a few seconds. Depending on the sample, equilibration and access of the active gas to the adsorption sites of interest may be faster in the static system.

Micromeritics Chemisorption Instruments

3flex chemisorption

3 Flex Chemisorption Option / 3 Flex TCD

The 3Flex TCD is our newest addition to the expanding capabilities of the 3Flex instrument family. Dynamic chemisorption analyses are available to the user with the addition of an integral thermal conductivity detector. This new feature allows the user to perform temperature programmed reduction (TPR), oxidation (TPO), desorption (TPD), and reduction reactions (TPRx). The 3Flex TCD also has an option for pulse chemisorption analyses which can be performed with manual injections or automatically with the optional injection loop.

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AutoChem II 2920

The AutoChem II 2920 is a fully automated chemisorption analyzer that can provide your laboratory with the ability to conduct a comprehensive array of highly precise studies of chemical adsorption and temperature-programmed reactions. With this single instrument, you can acquire valuable information about the physical properties of your catalyst, catalyst support, or other materials.

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The Micromeritics ASAP 2020 Plus integrates a variety of automated gas sorption techniques into a single, but powerful, table-top instrument. The system is designed to provide high-quality surface area, porosity, chemisorption and physisorption isotherm data to materials analysis laboratories with ever-expanding analytical requirements. The ASAP 2020 Plus provides maximum versatility over a remarkable range of applications to meet your specific needs.

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FR / MR Reactor Systems

This series of Micromeritics Flow Reactors (FR) features highly advanced modular laboratory screening units for measuring the activity and selectivity of catalysts. The Micromeritics FR-50, FR-100 and FR-200 have been developed to help save time and resources during catalyst development and screening. The Micromeritics Multi Reactor series features highly productive evaluation units for the laboratory that enable scientists to comprehensively measure the activity and selectivity of catalysts for screening and kinetic studies.

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Chemisorb HTP – High Throughput Chemi Analyzer

Optimum design and efficient utilization of catalysts require a thorough understanding of the surface structure and surface chemistry of the catalytic material. Chemical adsorption analyses can provide much of the information needed to evaluate catalyst materials in the design and production phases, as well as after a period of use.

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PTA Testing Options:

Chemisorption Tests:

  • Volumetric Chemisorption analysis
  • Dynamic or pulse Chemisorption analysis
  • Pulse Chemisorption using liquid vapors

Temperature-Programmed Studies:

  • Temperature-Programmed Reduction (TPR)
  • Temperature-Programmed Desorption (TPD)
  • Temperature-Programmed Oxidation (TPO)
  • Mass Spectrometry analysis*

Other Chemisorption Experiments:

  • Heat of Desorption, first order Kinetics
  • Isosteric Heat of Adsorption

* Must be combined with Temperature Program study or TGA

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