Monolithic reactors for environmental applications

2017

This paper presents the first results of monopropellant decomposition tests obtained from monolithic ceramic catalysts produced by means of additive layer manufacturing techniques and using ceramic precursors. The purpose is to compare the performance of printed monoliths with traditionally manufactured catalysts with respect to decomposition of highly concentrated hydrogen peroxide. Small holes with a pitch larger than 0 are generally difficult to manufacture. Holes with a diameter of 1.25 mm are difficult to manufacture when the pitch is larger than 2. Decomposition tests revealed that the manufacturing process does not influence the transient pressure performance but is noticeable in the transient temperature performance. However, the influence is only present during part of the transient phase. For optimum transient performance the surface area-to-volume ratio should be maximised.

Chemical Engineering Journal, 2010

A novel structured catalyst based on a binderless zeolite film was developed onto a cordierite monolith. The zeolitic film was obtained performing a binderless washcoating which was followed by a hydrothermal treatment, which resulted in a coating with hybrid physicochemical properties, having a porous washcoat-like microstructure with an intergrowth between the aggregates. This combination confers to the zeolite coating an open structure which is an advantage of washcoats and a high mechanical stability characteristic of the zeolite growths. It should be emphasized that these desired properties are obtained without the use of binders. The physico-chemical properties were investigated through MIP (mercury intrusion porosimetry), SEM (scanning electron microscopy), ultrasonic adherence tests, NO-TPD (temperature-programmed desorption of NO) and EPMA (electron probe microanalysis). The catalytic properties of the monolith were evaluated in the selective catalytic reduction of NO x at high spatial velocities, showing promising results.

Extruded monolith substrates are widely used in automotive and stationary emission control reactors such as selective catalytic reduction (SCR) units. Monoliths are increasingly being used, developed, and evaluated as catalyst supports in many new reactor applications such as chemical and refining processes, catalytic combustion, ozone abatement, and others. This paper gives a general overview of monolith fabrication, characteristics and typical use. Several commercial product applications and new developments for use of monolith reactors in automotive, stationary and chemical industry are discussed.

Applied Catalysis A: General, 1995

Many important industrial processes currently employ synthetic zeolites as catalysts. Fixed and fluidized bed reactors, employed in most commercial applications, use catalyst pellets formed from mixtures of zeolite crystals and binders. However, binders hinder access to the zeolite active sites; thereby reducing catalytic efficiency. This study demonstrates that zeolites synthesized in situ on monolithic substrates offer lower resistance to mass transfer. The controlling mass transfer regime in these reactors is assessed from experimental and theoretical studies of two test reactions in ZSM-5 coated monolithic reactors, Also, the applicability of the monolithic reactor configuration to other zeolite catalyzed processes is discussed. * Tel. ( + 1-513) 5562666, Fax ( + 1-513) 5563473. 0926-860X/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI0926-860X( 95) O0123-9

Chemical Engineering Journal, 2001

Monolithic supports are uni-body structures composed of interconnected repeating cells or channels. They are most commonly composed of ceramic or metal materials but some can also be made of plastic. The most important physical characteristics when used as a catalyst ...

2015

FeCralloy rods (0.5 mm thickness) were subjected to high temperature thermal oxidation to produce a metastable alumina phase. This structured layer acts as an anchor to bind additional coatings of alumina via washcoat techniques, thereby improving the layer thickness and increasing adhesion of the catalytic surface. In addition, thin films of structured zeolite catalysts (ZSM-5 and Zeolite Y) were grown onto the surface of a metal substrate using in-situ hydrothermal synthesis. All catalysts were fully characterised by SEM, EDX and XRD. The cracking of n-heptane over structured catalysts for both ZSM-5 and Zeolite Y showed very similar product selectivity compared with similar traditional pelleted catalyst forms. The alumina coated FeCralloy rods were impregnated with 1 wt. % platinum and tested in a fixed bed reactor to assess the impact on yield for the dehydrogenation of methylcyclohexane and compared with conventional 1 wt. % Pt/Al2O3 pellets. This paper demonstrates that struct...

Annales de chimie Science des Matériaux, 2018

In this work, the Me/CeO2 (Me = Rh, Ni) catalytic phase was in-situ deposited by the Solution Combustion Synthesis (SCS) on commercial cordierite monolith (500 cpsi) and alumina open-cell foams (20,30,40 ppi). All the coated structures were characterized by SEM/EDX to analyze the morphological characteristics of the coated films; the mechanical stability was analyzed by ultrasound tests; pressure drops at different superficial velocities were derived. The catalytic activity and stability were investigated towards Steam Reforming (SR) and Oxy-Steam Reforming (OSR) of different fuels (CH4, biogas, n-dodecane) and CO2 methanation reaction. High catalytic activity was observed for both reforming and methanation processes, following the order 500 cpsi-monolith < 20 ppi-foam < 30 ppi-foam ≈ 40 ppi-foam. Excellent long-term stability was observed over 200 h of time-on-stream (TOS). RÉSUMÉ. Dans cet article, la phase catalytique Me/CeO2 (Me = Rh, Ni) a é té dé posé e in situ par la synthè se de combustion en solution (SCS, le sigle de « Solution Combustion Synthesis » en anglais) sur des monolithes de cordié rite (500 cpsi) et des mousses à cellules ouvertes d'alumine (20,30,40 ppi). Toutes les structures revê tues ont é té caracté risé es par SEM / EDX pour analyser les caracté ristiques morphologiques des films revê tus; la stabilité mé canique a é té analysé e par ultrasons; la permé abilité et le coefficient de forme ont é té dé rivé s des donné es de chute de pression. L'activité et la stabilité catalytique ont é té é tudié es pour les ré actions de reformage à la vapeur (SR, le sigle de « Steam Reforming » en anglais) et à l'oxy-vapeur (OSR, le sigle de « Oxy-Steam Reforming » en anglais) de diffé rents combustibles (CH4, biogaz, n-dodé cane) et la ré action de mé thanisation au CO2. Une activité catalytique é levé e a é té observé e à la fois pour les procé dé s de reformage et de mé thanation, suivant l'ordre de 500 cpsi-monolithe <20 ppi-mousse <30 ppi-mousse ≈ 40 ppi-mousse. Une excellente stabilité à long terme a é té observé e sur une pé riode de 200 heures d'utilisation (TOS, le sigle de « time-on-stream » en anglais).

Applied Catalysis A: General, 2010

A novel fixed-bed reactor for gas-solid catalytic reactor using bulk monolithic catalyst (BMC), the so-called tube fitted bulk monolithic catalyst (TFBMC), instead of conventional packed bed reactor is presented. From the two types of monolithic catalyst, i.e. washcoated and the one made from bulk catalyst, the first one has been widely discussed in the literature. However, there is scarce report regarding the latter. In this research we have focused on introducing, preparation and application of TFBMC. Here, the two types of monolithic catalysts are compared. The advantages and disadvantages of the proposed concept as compared with packed bed reactor are discussed. Several parameters such as material, structure and preparation method of the catalysts are investigated. As a case study the mold ability and the performance of TFBMC in Fischer Tropsch synthesis (FTS) are explained. The results indicate that the TFBMC has superior advantages over the conventional fixed-bed reactors. Furthermore, the concept employed in fabrication of TFBMC may be easily applied with minimum modification to the conventional fixed-bed reactors which results in more productivity and better performance.

Catalysis Today, 2001

Also in multiphase applications, monolithic catalytic reactors have a large potential. In many respects they outperform the conventional reactors such as slurry and trickle bed reactors. Monoliths can play a role in process intensification because they allow exceptionally large rates and selectivities. They can also be used in multifunctional reactors.

2013

Structured catalysts formed from the growth of zeolites on substrates is an area of increasing interest due to the increased efficiency of the catalytic process, and the ability to provide superior heat transfer and thermal conductivity for both exothermic and endothermic processes. However, the generation of structured catalysts represents a significant challenge when balancing the relationship variables between materials properties and catalytic performance, with the Na2O, H2O and Al2O3 gel composition paying a significant role in this dynamic, thereby affecting the both the type and range of application. The structured catalyst films generated as part of this investigation have been characterised using a range of techniques, including X-ray diffraction (XRD), Electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and Thermogravimetric Analysis (TGA), with the transition from oxide-on-alloy wires to hydrothermally synthesised uniformly zeolite coated surfaces being demo...