Wiley InterScience highlighted a paper that was just published in MacroMolecular Reaction Engineering by Professor Rolf Mülhaupt and his student Rainer Xalter of Albert-Ludwigs University in Freiburg, Germany.
This paper discusses the use of METTLER TOLEDO FBRM® and PVM® for real-time in-process monitoring of polymer and catalyst particles. During the polymerization of high-density polyethylene (HDPE), FBRM® and PVM® are used to determine polymer growth kinetics and to measure the effects of catalyst breakage and attrition within standard commercial-scale reactors.
“Unprecedented insight into the particle growth processes during ethylene slurry polymerizations catalyzed by supported single-site and Ziegler catalysts was gained by online monitoring using two different probes inserted directly into the reactor. FBRM online monitoring complemented by PVM online visualization of polymer particles allowed for the distinction of different types of particle growth processes depending on catalyst type and productivity.”
Citation: “On-line Monitoring of Polyolefin Particle Growth in Catalytic Olefin Slurry Polymerization by means of LasentecTM Focused Beam Reflectance Measurement (FBRM) and Video Microscopy (PVM) Probes”, R. Xalter and R. Mülhaupt, Macromol. React. Eng. 2010, 4, 25. http://doi.wiley.com/10.1002/mren.200900048?crel=US_AC_eAdv_Blog
Full News Release (Wiley InterScience, January 5, 2010)
The new technique involves using a LasentecTM “Particle Vision and Measurement” (PVM) probe developed by Mettler-Toledo GmbH, which, the authors explain, “makes video microscopic images of moving particles technically feasible via CCD camera-mediated imaging using a pulsed light source”, combined with a Lasentec “Focused Beam Reflectance Measurement” (FBRM) probe developed by the same company. The FBRM probe “employs a rotating focused laser beam which is scattered back at individual particles at or close to the focal point of the laser beam.” Mathematical evaluation of the duration and intensity of the backscattered light is used to determine particle size distributions.
As the scientists explain, “While the FBRM technique delivers well-founded statistical data regarding the evolution of the particle size distribution over time, the PVM probe yields high-quality images providing detailed information on size and shape of the particle species being present in the respective stages of the polymerization process.” Methods for correlating the results with reaction kinetics were developed, and results from both probes compared well with those obtained from off-line monitoring for a variety of reaction scenerios. Although only polyethylene was investigated in this paper, application to other polyolefin slurry systems is expected to be straightforward. Application to copolymerization reactions is expected to yield exciting results.
“On-line Monitoring of Polyolefin Particle Growth in Catalytic Olefin Slurry Polymerization by means of LasentecTM Focused Beam Reflectance Measurement (FBRM) and Video Microscopy (PVM) Probes”, R. Xalter and R. Mülhaupt, Macromol. React. Eng. 2010, 4, 25.
HDPE, the most common form of polyethylene, is produced in catalytic slurries. Current methods for monitoring these types of reactions have involved off-line monitoring or the use of special cells without stirring. Stirring is necessary in commercial polyethylene production, but it plays havoc with standard particle monitoring techniques, and it is the particles that must be under constant surveillance if the reaction is to be followed closely.