Particle analysis makes solid progress

Plants benefit from real-time online measurements

By Seán Ottewell, editor at large

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A substantial part of this demand is now “green-driven,” he adds, for example from companies involved in carbon dioxide sequestration. Sometimes the gas is used as a feedstock to grow algae or else stored in old coal mines and oil fields. “The technological challenge for us is to measure very specific gas/solid interactions,” he explains. It’s a similar story with the synthetic porous materials currently being designed for both carbon dioxide sequestration and hydrogen storage.

Thomas credits Quantachrome’s success to its ability to nimbly adapt its existing technologies to changing demands. This means not just dealing with different feedstocks but also with different temperature ranges and more downstream applications — “hybridizing, or hyphenating techniques,” he says.

One important role is in analyzing catalysts. The active surface of many catalysts is often found deep within pores of individual particles. This has a tremendous impact on catalyst performance because, even for a single solid, not all surfaces are created equal. Real surfaces are heterogeneous and their properties vary from exterior to interior as well as from one surface site to another. Thomas maintains that textural (surface area, pore size and pore volume) properties and surface reactivity/heterogeneity can most fully be quantified and qualified via a complete gas sorption analyzer such as the Autosorb-1-C with its optional thermal conductivity detector (TCD).

That unit integrates catalyst characterization with flow and vacuum volumetric techniques to provide information such as meso- and micropore size distribution, active surface area, degree of metal dispersion, and heats of adsorption. Temperature-programmed techniques can be automatically performed via user-programmable pretreatment and analysis procedures while a flow-based pulse titration method rapidly determines active surface area.

Thomas echoes Pugh’s comments: “Training is very big now and attendances have doubled in the last year. This is about protecting the investment, too, as customers can be spending anything from $3,000 to $110,000 on their instruments,” Thomas explains. “A whole generation of people with the sort of knowledge needed to use this technology have taken early retirement, so there is a generation gap developing. Many of the younger people often don’t understand the science involved and so don’t know whether the data they are getting is any good. Therefore we do encourage training.”

More options

Malvern and Quantachrome certainly aren’t alone in responding to the chemical industry’s demand for online real-time particle characterization data. For instance, Sympatec, Clausthal-Zellerfeld, Germany, is another long established vendor. Its line of products rely on laser diffraction, image analysis and ultrasonics extinction. Mytos analyzers, which combine proven laser diffraction sensors and dry dispersers, are the state-of-the-art in-line laser diffraction units for dry powders from 0.25–3,500 µm, claims the company. For granulates or very fragile particles, Mytis units team the laser diffraction technology with a gravity disperser in a single instrument that covers 0.5–10,000 µm range.

Mettler Toledo, Columbia, Md., certainly believes in the value of in-situ particle measurement. Its Lasentec FBRM and PVM analyzers are in-process, real-time technologies said to be suitable for crystallization or virtually any solids or dispersed-phase concentration testing. Models of both are available for use from lab through scale-up to production, ensuring consistent data throughout the life of a process.

 

Figure 2. Portable unit provides performance that reportedly rivals larger and more expensive FTIR spectrometers. Source: A2 Technologies.

For A2 Technologies, Danbury, Conn., portability is key. The company’s new Exoscan FTIR spectrometer, launched in March at Pittcon, is designed for non-destructive, on-site surface and bulk analysis (Figure 2). Claimed to be the most compact FTIR spectrometer on the market, Exoscan weighs less than seven pounds. Yet, says A2, its analytical performance rivals far larger and more expensive traditional FTIR spectrometers.

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