On isothermality in some commonly used plug flow reactors for X-ray based investigations of catalysts

Abstract

We compare two reactor setups commonly used to make operando measurements of catalyst behavior using X-rays in terms of the degree to which they may be considered to yield radial and axial isothermality.

Active sites and mechanisms in the direct conversion of methane to methanol using Cu in zeolitic hosts: a critical examination

“…Critically, isothermality within a reactor bed must be achieved to an acceptable degree in order to avoid thermal gradients yielding incorrect or misleading results from what are either, point measurements made within the body of a much larger sample, or measurements that report an average view over a large (a few millimetres) portion of a sample bed. 89 In the case of the use of synchrotron radiation, there is also the possibility that the X-rays themselves may induce unwanted changes in the systems under study, either through local heating effects, or from the production of electrons. Both of these possibilities have the potential to promote reduction of Cu(II) to Cu(I) wherein none should ordinarily occur.…”

Unwanted effects of X-rays in surface grafted copper(ii) organometallics and copper exchanged zeolites, how they manifest, and what can be done about them

“…= 2.2 mm) capillary. The sample was then mounted within a reactor system based on the design due to Chupas et al 59 that we have demonstrated 60 to yield an isothermal region twice the length of the sample bed and, therefore, to be appropriate to the kinetic study of these materials. All gases were of a high purity and flowed through scrubbers, as appropriate for each gas, to remove any residual oxygen and moisture prior their being passed through mass flow controllers (20 ml min À1 all gases).…”

Sample Environment for Operando Hard X-ray Tomography—An Enabling Technology for Multimodal Characterization in Heterogeneous Catalysis

“…To meet the requirements for operando catalysis studies, particularly the need for a gas-tight system and controlled environment, a quartz capillary reactor was chosen as the primary sample holder. Such capillary reactors are analogous to those used in many conventional XAS or XRD studies using synchrotron radiation [44]. A tube or rod (support) made of glassy carbon is positioned parallel to the capillary sample holder.…”

“…An appropriate gas delivery system, such as thermal mass flow controllers, allows precise control of gas composition, flow rate, and space velocity analogously to conventional XAS or XRD studies in capillaries. Two hot air blowers positioned on either side of the sample were chosen to allow relatively uniform heating, analogous to those used in conventional XAS and XRD studies [44]. Particular care must be taken when using aRCTIC to ensure uniform heating is applied to the sample during rotation and for extended periods of tomography data acquisition.…”