Far field combined AFM and micro-Raman imaging for characterisation of surface of structured catalysts : example of Pd Doped CoOxCoO_x catalysts on precalcined kanthal steel

A coupled AFM-Raman system was used to study the surface heterogeneity of catalytic materials at various stages of their preparation. The catalysts chosen for the analyses were cobalt oxide with and without palladium dopant deposited on surface of pre-calcined steel carriers. Steel carriers are surveyed here in terms of their application as fillers for structured reactors for the catalytic combustion of volatile organic compounds. Upon steel precalcination stage the interfaced AFM-Raman and in situ Raman analyses revealed the evolution of alumina and iron oxide phases on the surface with their final stable forms found as being α-Al_{2}O_{3} and α-Fe_{2}O_{3}. Upon catalyst layering stage AFM-Raman mapping evidenced uniform coverage of precalcined steel carrier with cobalt spinel oxide Co_{3}O_{4}. For the doped catalyst except Co_{3}O_{4} palladium(II) oxide grains were also found on the surface. The differences in the composition of cobalt catalysts were correlated with the differences in their catalytic activity

DeNOxDeNO_{x} abatement modelling over sonically prepared copper USY and ZSM5 structured catalysts

Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In this study, the performance of three structured supports with deposited Cu/USY (Ultrastabilised Y—zeolite) for deNOx abatement were modelled. Based on kinetic and flow resistance experimental results, the one-dimensional (1D) model of structured reactor was developed. The performance of the structured reactors was compared by the length of the reactor necessary to achieve an arbitrary 90% NOx conversion. The performed simulations showed that the sonochemically prepared copper USY and ZSM-5 zeolites deposited on metallic supports may be successfully used as catalysts for deNOx process

Non-noble metal oxide catalysts for methane catalytic combustion : sonochemical synthesis and characterisation

The aim of this study was to obtain nanocrystalline mixed metal-oxide–ZrO2 catalysts via a sonochemically-induced preparation method. The effect of a stabiliser’s addition on the catalyst parameters was investigated by several characterisation methods including X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The sonochemical preparation method allowed us to manufacture the catalysts with uniformly dispersed metal-oxide nanoparticles at the support surface. The catalytic activity was tested in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was higher than that of the reference catalysts prepared by the incipient wetness method without ultrasonic irradiation. The cobalt and chromium mixed zirconia catalysts revealed their high activities, which are comparable with those presented in the literature

In search of governing gas flow mechanism through metal solid foams

Solid foams have been intensely studied as promising structured catalytic internals. However, mechanisms governing flow and transport phenomena within the foam structures have not been properly addressed in the literature. The aim of this study was to consider such flow mechanisms based on our experimental results on flow resistance. Two mechanisms were considered: developing laminar flow in a short capillary channel (flow-through model), and flow around an immersed solid body, either a cylinder or sphere (flow-around model). Flow resistance experiments were performed on three aluminum foams of 10, 20, and 40 PPI (pores per inch), using a 57 mm ID test column filled with the foams studied. The foam morphology was examined using microtomography and optical microscopy to derive the geometric parameters applied in the model equations. The flow-through model provided an accuracy of 25% for the experiments. The model channel diameter was the foam cell diameter, and the channel length was the strut thickness. The accuracy of the flow-around model was only slightly worse (35%). It was difficult to establish the geometry of the immersed solid body (sphere or cylinder) because experiment characteristics tended to change from sphere to cylinder with increasing PPI value

Prospective catalytic structured converters for NH3−SCRNH_3-SCR of NOxNO_x from biogas stationary engines : in situ template-free synthesis of ZSM-5 Cu exchanged catalysts on steel carriers

The main objective of this study is to develop highly active catalyst and its preparation method that would meet the requirements of steel carriers for short- channel structured converters for NO x abatement from stationary biogas engines. The in situ synthesis was applied to deposit a series of Cu-exchanged MFI zeolite (ZSM-5) on kanthal sheets. The samples differ in preparation con- ditions: organic template assisted and template-free syn- thesis, Si/Al ratio and catalyst carrier pretreatment (calcined vs. non-calcined). Dip-coating method was used as a reference to compare loading efficiency. In order to evaluate preparation quality and purity of resulting struc- ture the samples were examined by XRD and SEM/EDS at various stages of preparation. For the assessment of mechanical endurance of the deposited catalyst layers the ultrasonication method was used. The results demonstrated high depositing efficiency of the in situ synthesis as well as high activity and selectivity of the Cu-exchanged MFI samples prepared without costly organic template

Characterization of fluid flow and heat transfer of expanded metal meshes for catalytic processes

In this work, three raised expanded metal meshes (EMMs) differing in mesh size were tested experimentally with regard to their flow and transport properties. Empirical equations for the Nusselt number and Fanning friction factor were developed. Alongside the experiments, simple computational fluid dynamics (CFD) models were used to simulate the pressure drop and heat transfer coefficients within EMMs. Finally, the Performance Efficiency Criterion (PEC) was applied to compare EMMs with other reactor packings

Short-channel structured reactor as a catalytic afterburner

Short-channel structures of triangular and sinu- soidal channel cross-sectional shape were examined exper- imentally to find their heat (or mass) transfer and flow friction (flow resistance) characteristics. A particular emphasis was placed on influence of the channels length (referred to its hydraulic diameter) on transport and hydro- dynamic characteristics. The transport and friction proper- ties were correlated in terms of dimensionless channel length with satisfactory accuracy. The dimensionless channel length was proved to be a key factor that determines the transport and friction coefficients. Comparison with ceramic monolith has shown possibility of using the struc- tures in automotive catalytic converters