The following scientific publications contain references to the TEOM Series 1500 Pulse Mass Analyzer:

Ind. Eng. Chem. Res. 1993, 32, 2969-2974

Simultaneous Measurement of Adsorption, Reaction, and Coke Using a Pulsed Microbalance Reactor

Frank Hershkowitz and Paul D. Madiera
Exxon Research & Engineering Company, Route 22 East, Annandale, NJ 08801 USA

A new research tool has been developed that allows in-situ measurement of the transient adsorption and coke deposition that occurs on zeolytic catalysts during short contact-time interactions with reactants. The tool is a microbalance pulse reactor (MPR), whose central feature is a new kind of microbalance that can accurately weigh a catalyst without regard to high velocities of vapor passing through. This TEOM microbalance measures mass by inertia instead of weight. In the MPR, zeolytic catalysts are exposed to short pulses of vapor-phase absorbate carried through the catalyst bed on helium carrier gas. The MPR has application to understanding the mechanisms of catalytic cracking, which include a complex interaction of adsorption, shape-selective diffusion, and rapid deactivation by coke.

 

Rupprecht & Patashnick Internal Study

Measuring Real Time Microgram Mass Changes in a Packed Bed of FCC Catalyst Using the R&P PMA-1500 Pulse Mass Analyzer

Tammy Heesakker
Rupprecht & Patashnick Co., Inc.

A new way to quantify the mass transfer dynamics of adsorption, coking, and deactivation using a fast (0.1 sec.), accurate (1ug) microreactor/microbalance is discussed. A demonstration using 1cc pulses of Isobutylene, Helium carrier gas and Magnasiv FCC catalyst at 300 and 450 degrees Celsius is presented.

 

Catalyst Deactivation 1994 Studies in Surface Science and Catalysis , Vol. 88 1994 Elsevier

In Situ Coking Kinetics Obtained from a Flow Through Microbalance and Reaction Kinetics Monitored by GC

S. C. Fung, C. A. Querini (a), K. Liu (b), D.S. Rumschitzki (b), T. C. Ho
Exxon Research & Engineering Company, Route 22 East, Annandale, NJ 08801 USA
(a) INCAPE, Sgo del Estero 2654 - (3000) Santa Fe - Argentina
(b) Department of Chemical Engineering, City College of New York, NY, NY 10031

A novel microbalance reactor system has been designed to provide continuous monitoring of coking rate and determinations of the reaction kinetics under realistic conditions. This microbalance is based on the mass effect on the vibrational frequency. The major advantage of this design as compared to a conventional gravimetric balance is that all feed gases to the vibrational microbalance flow through the catalyst bed situated at the tip of a hollow glass tube. Therefore, accurate measurements of catalyst activity can be obtained with the vibrational microbalance but not with a gravimetric balance because severe feed gas bypassing occurs in the latter. The utility of this new microbalance reactor system is demonstrated in gas adsorption , catalyst deactivation and coke removal.

 

Applied Catalysis A: General 137 (1996) L1-L8

Catalyst deactivation studied by conventional and oscillating microbalance reactors

De Chen (a), A. Gronvold (b), H. P. Rebo (a), K. Moljord (b), A. Holmen (a)
(a) Dept. Of Ind. Chem., Norwegian University of Science and Tech., N-7034 Trondheim, Norway
(b) SINTEF Applied Chemistry, N-7034 Trondheim, Norway

The oligomerization of ethene over H-ZSM-5 has been used as a model reaction for studying coke formation in two different microbalance reactors, a conventional microbalance and a new oscillating TEOM 1500 microbalance reactor. Significant gradients prevailed in the catalyst bed in the basket of the conventional microbalance reactor even with this moderately rapid and exothermal reaction, making it difficult to obtain true kinetic information. In the oscillating microbalance reactor the reactants are forced to flow through the catalyst bed in the same manner as in a fixed-bed reactor and kinetic data could be obtained in the absence of transport limitations in the catalyst layer.

 

ACS Symposium Series Fluid Catalytic Cracking III Materials and Processes

Activity and Deactivation in catalytic Cracking Studied by Measurement of Adsorption During Reaction

Frank Hershkowitz, Haroon S. Kheshgi, and Paul D. Madiera
Exxon Research & Engineering Company, Route 22 East, Annandale, NJ 08801 USA

A new research tool has been developed that allows in-situ measurement of the transient adsorption and coke deposition that occur on zeolytic catalysts during short contact-time interactions with reactants. The tool is a microbalance pulse reactor (MPR), whose central feature is a new kind of microbalance that can accurately weigh a catalyst without regard to high velocities of vapor passing through. Zeolytic catalysts are exposed to short pulses of vapor-phase absorbate carried through the catalyst bed on helium. Adsorption responses to pulses of n-decane, isopropyl benzene and triisopropylbenzene on La3+Y and other zeolites are reported. A regression/simulation method is used to characterize the adsorption responses in terms of adsorption and reaction parameters. The deactivation of the zeolite by coke is found to follow a linear trend, as measured using a sequence of pulses.

 

Journal of Physical Chemistry, 101, 1113-1124

Isothermal Reduction of Titanium Dioxide-Based Materials

James E. Rekoske and Mark A. Barteau
Center for Catalytic Science and Technology, Department of Chemical Engineering,
University of Delaware, Newark, DE 19716 USA

As metal oxide reduction may be a limiting or otherwise important step in a reaction cycle, a complete description of the kinetics of the reduction can be critical to the successful choice of catalytic material. Unfortunately, such information is often lacking. Such is the case in our attempts to develop a catalytic cycle from the stoichiometric reductive carbonyl coupling reaction on reduced TiO₂ surfaces. To provide the necessary reduction kinetics, reaction of the anatase and rutile forms of TiO₂ with H₂ has been studied from 573 to 773 K. A novel flow-through microreactor which provides time-resolved catalyst mass measurements to +/- 1 µg while maintaining a conventional, tubular reactor, gas-solid contacting pattern has been employed. A shift in the kinetic order with respect to H₂ with increasing temperature occurs, from one-half order at 573 K to zero order at 673 K and above. A discontinuity was also observed within this same temperature range in Arrhenius plots of the reduction rates of both anatase and rutile TiO₂; apparent activation energies determined were approximately 12 kcal mol^-1 above and 29 kcal mol^-1 below 623 K. Modification of the surface of anatase TiO₂ with a sufficient loading of group VIII metals removes the Arrhenius plot discontinuity, increasing the rate reduction and decreasing the apparent activation energy at low temperatures. A change in the rate determining step is indicated by these observations, and a mechanistic scheme which combines the current and previous observations within a single framework is proposed.