Reactor for in situ measurements of spatially resolved kinetic data in heterogeneous catalysis

Abstract

The present work describes a reactor that allows in situ measurements of spatially resolved kinetic data in heterogeneous catalysis. The reactor design allows measurements up to temperatures of 1300 °C and 45 bar pressure, i.e., conditions of industrial relevance. The reactor involves reactants flowing through a solid catalyst bed containing a sampling capillary with a side sampling orifice through which a small fraction of the reacting fluid (gas or liquid) is transferred into an analytical device (e.g., mass spectrometer, gas chromatograph, high pressure liquid chromatograph) for quantitative analysis. The sampling capillary can be moved with μm resolution in or against flow direction to measure species profiles through the catalyst bed. Rotation of the sampling capillary allows averaging over several scan lines. The position of the sampling orifice is such that the capillary channel through the catalyst bed remains always occupied by the capillary preventing flow disturbance and fluid bypassing. The second function of the sampling capillary is to provide a well which can accommodate temperature probes such as a thermocouple or a pyrometer fiber. If a thermocouple is inserted in the sampling capillary and aligned with the sampling orifice fluid temperature profiles can be measured. A pyrometer fiber can be used to measure the temperature profile of the solid catalyst bed. Spatial profile measurements are demonstrated for methane oxidation on Pt and methane oxidative coupling on Li/MgO, both catalysts supported on reticulated α−Al2O3 foam supports.

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

“…Firstly, model reactors have been developed which can operate closely to industrial operating conditions and which allow shining X‐rays, IR, UV including laser light into the reactor. For example, reactors have been designed that allow for profiling temperature and concentration of species, while performing spectroscopy at the same time 65, 66. Even spatio–temporal studies are possible 67, 68.…”

“…Nevertheless, studies addressing the dynamic behavior of catalytic reactors and solid (electro‐)catalysts for synthesis of chemical energy carriers remain largely underrepresented, and also a connection to the state of the catalyst in different places inside the reactor under such conditions is yet to be made. To tackle this, more work is needed in particular concerning the development of advanced laboratory reactor systems including catalysts, e.g., by combining X‐ray140 and optical141 in situ spectroscopy, capillary techniques,66 advanced methods for gas sampling, and effective approaches to reactor design and fabrication such as, e.g., microfabrication142 and additive manufacturing (3D printing) 143…”

Measurement and analysis of spatial reactor profiles in high temperature catalysis research

“…In the present paper the further development and application of the spatial profile technique by Horn et al will be outlined. In contrast to the designs developed at Oak Ridge National Lab and at the Paul Scherrer [11]. The latest developments described in this paper concern spatial profile measurements at high reactor pressures, spatial profile measurements in packed beds, and spatially resolved laser spectroscopy using fiber probes.…”

“…Therefore, current measurements employ sealed capillaries with a side-sampling orifice that is located at such a distance from the closed tip that the capillary channel remains filled at any sampling position (Fig. 2), thereby substantially improving the quality of the profiles [11,12]. In terms of the orifice diameter a compromise must be made between spatial resolution, sampling flow rate withdrawn from the reactor, and transfer time to the analytical device.…”

“…2, it will be outlined below how species, temperature and spectroscopic profiles are obtained. For details of the latest profile reactor operated at the Fritz Haber Institute in Berlin, the reader is referred to [11].…”