To establish the structure activity relationship between a catalyst and its activity in different gas phase or liquid phase reactions, a common laboratory provides different techniques to identify the structural properties of catalytic support or active catalysts.
Structural properties are influenced by many factors, including by the choice of the three major catalyst constituents: support, active component (metal, oxides) and promoters. Eventual catalytic activity depends on the interaction between the major catalyst constituents when exposed to different temperatures in the presence or absence of different gases and/or liquids.
Gas Adsorption
Supports and active catalyst properties such as surface area, pore size distribution and pore volume have a major influence on the eventual catalytic activity. To establish these properties, we have at our disposal an Accelerated Surface Area and Porosity Analyzer (ASAP 2420) from Micromeritics that is dedicated to physisorption, a gas adsorption analysis technique. ASAP 2420 allows for the determination of abovementioned properties by incremental addition of a non-reactive adsorptives (N2, Ar, Kr, CO2) at liquid nitrogen or argon temperatures to a previously degassed porous solid material.
Properties of active components of a catalyst (usually metal) are identified utilizing Accelerated Surface Area and Porosimetry Analyzer (ASAP 2020) from Micromeritics, which is dedicated to Chemisorption. This gas adsorption analysis technique allows determination of properties such as metal dispersion, metal surface area, heat of chemical adsorption, strong and weak chemisorption, and the crystallite size of a catalyst. These properties are accessed by high vacuum-high temperature pretreatment of a solid sample and measurement of the pressure above the sample when submitting to incremental gas (H2, CO) additions.
Thermal Analysis
During the preparation of support, active catalysts (as well as during the catalytic reaction)—these inorganic materials are exposed to different temperature profiles in the presence or absence of different gases or liquids. To establish the change of properties of inorganic materials when exposed to high temperatures, Thermal Analysis techniques such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) are utilized. Thermogravimetric Analysis (TGA) is used to study mass change of solids and liquids while exposed to variable temperature and gas environment. During TGA Analysis, a sample can be exposed to temperatures up to 1600 °C in the presence of inert (N2, Ar,…), oxidizing (Air, O2,..) as well as diluted hydrogen (4% H2 in for example Argon). Differential Scanning Calorimetry (DSC) is used to study properties such as thermal capacity, enthalpy and glass transition temperature can be accessed, differential heat of adsorption. Materials can be studied from -150 °C up to 500 °C under inert (N2, Ar..) or oxidizing (Air, O2,..) gases.
Dynamic Light Scattering (DLS) and Static Light Scattering (SLS)
Dynamic Light Scattering and Static Light Scattering techniques are utilized to determine the particle size distribution, zetapotential, point of zero charge, as well as molecular weight distribution. Malvern ZEN 3600 instruments measure particle size (hydrodynamic diameter) between 0.6 nm up to 6 μm, molecular weight in the range of 1000 to 2*107 Da and zetapotential for particles in the size range of 5 nm to 10μm. A Mastersizer 2000 that is solely dedicated to particle size analysis extends the measuring range from 0.02 μm up to 2000 μm.