Supported monolithic honeycomb

Catalytic Support Body Monolithic Honeycomb Unit. The terms substrate and brick are also used to describe the high geometric surface area material upon which the active coating material is placed. Monolithic honeycomb catalytic support material comes in both ceramic and metallic form. Both are used in automobile catalysts and each possesses unique properties. A common property is a high geometric surface area which is inert and does not react with the catalytic layer. 

Most catalysts consist of active components dispersed as small crystallites on a thermally stable, chemically inactive support such as alumina, ceramics, or metallic wires and screens. The supports are shaped into spheroids, cylinders, monolithic honeycombs, and metallic mesh or saddles. 

Weiland et al observed that a small amount of Pt metal present in the Rh-based catalyst could significantly improve the catalyst activity for ATR of gasoline range fuels. They claimed that the role of Pt is to enhance oxidation activity, whereas Rh provides high SR activity. The Rh-Pt/alumina catalyst used in the study was supported on monolithic honeycombs and had a Rh to Pt ratio of 3-10 by weight. The geometry (metal monolith, ceramic monolith, or ceramic foam) of the support did not affect the product composition. ... 

Prior to spin coating, both ends of a pre-fabricated porous support, either in the form of a tube or a monolithic honeycomb element, are filled with the slip and temporarily sealed with gaskets. Slips of Ni, A1 and AI2O3 have been spin coated at a rotational speed of up to about 1300 rpm to form membrane layers [Sumitomo Electric Ind., 1981 NGK Insulators, 1986]. The development of a coating layer is expected to be faster with the in coating process than the dip coating process due to the centrifugal force. 

The monolith honeycomb structure is widely used as a catalyst support for gas treatment applications such as the cleaning of automotive exhaust gases and industrial off-gases [1,2]. In these applications, in which large volumetric flows must be handled, monoliths offer certain advantages, such as low pressure drop and high mechanical strength. 

Depending on the application, different kinds of support geometries such as pellets, monolithic honeycomb stmctures and fibers are used. Pressure drop induction becomes of importance when incorporating a catalyst to the reactor system. Pellets can contribute to relatively higher pressure drops. The monolithic honeycomb stmctures are technologically advanced and can offer low pressure drop induction. They are predominantly applied for environmental catalysis applications and hydrogen peroxide production. In order to lower the pressure drop in... 

Industrial catalysts require supports with desirable properties such as resistance to thermal shocks, mechanical strength and chemical stability. For catalytic combustion applications they must be adequately shaped to achieve low pressure drop. The monolithic honeycomb type is the most technologically advanced substrate and successfully satisfies these criteria. 

In this work the catalytic activity of a series of copper oxide catalysts supported on monolithic honeycomb supports in the reduction of nitrogen oxide with propylene in an oxidising atmosphere was studied. The monoliths were produced from acid washed sepiolite, sepiolite or a mixture of sepiolite and alumina in order to study the effect of the support on the activities and selectivities of the catalysts. Tlie introduction of nickel oxide as a second active species on the overall activity was also detennined. Finally tlie application of an alumina washcoat impregnated with the copper and nickel salts to increase the accessibility of tlie gases to be treated to the active phase was studied. 

Catalytic afterburning (off-gas purification) Pt/Pd LaCeCoO (perovsldte) oxides of y W, Cu, Mn, Ife supported catalyst (honeycomb monolith or catalyst bed) or bulk catalyst 150-400 °C 200-700 "C... 

A desiccant wheel assembly consists of i) a core that contains the desiccant materials, ii) a core/wheel support structure, iii) a drive system to rotate the wheel at a very low speed, and iv) a set of air seals to separate the process air stream from the regeneration air stream. The core has a monolith honeycomb type structure. Both sinusoidal and hexagonal channels are used in commercial equipment. Various types of materials have been used for support matrix that includes ceramic, glass fibers, and corrugated aluminum sheets. The desiccant materials may be washcoated, impregnated, or formed in situ on the support matrix. 

The reactor consists of a quartz tube (length = 62 cm, ID = 20 mm) placed in an oven for thermal insulation and reaction light-off. The monolithic honeycomb catalyst (diameter = 19 mm, variable length) is placed 230 mm downstream of the reactor inlet. For increased insulation, the part of the reactor tube, in which the catalyst is positioned, is wrapped with a 1-cm-thick layer of quartz wool. Uncoated monoliths up- and downstream of the catalyst are employed as heat shields (front heat shield (FHS) and back heat shield (BHS), respectively). The FHS also serves as support for the probe applied in the samphng technique. To prevent a gas by-pass between monoliths and quartz tube, the heat shields and the catalyst are wrapped with... 

Cellular ceramic supports are proposed as an attractive alternative to conventional carriers (generally spheres, extradates or pellets) for solid catalysts. They are of two types (i) monolith honeycomb made of small parallel squared channels (about 1 mm size) displaying a catalytic wall (400 channels per square inch or cpsi) or (ii) monolith foam presenting small blocks of pores (30 pores per inch or ppi). These materials are specifically manufactured by CTI Company (Ceramiques Techniques et Industrielles, Salindres, France) or Coming Company. 

Ceramic honeycomb monoliths are porous macro-structured supports consisting of parallel channels. On the walls a thin layer of active material can be applied (Figure 1). Honeycomb catalyst supports were originally developed for use in automotive... 

A variety of photocatalyst supports has been examined experimentally. Dip-coated glass slides or plates have been used in many experimental systems as a simple lab-scale supported photocatalyst system. Coated glass offers many of tlte important features of a supported photocatalyst while still offering relatively simple preparation. Honeycomb monoliths, widely used as commercial catalyst supports for a variety of gas-phase applications, have also been examined as photocatalyst supports (Fig. 3). Although these monoliths offer good stability and excellent throughput, providing illumination for the photocatalyst inside the monolith channels can be problematic [41,42]. Randomly structured support materials, like fiber-based filters, reticulated foams, and similar materials, have been used... 

Many commercial ceramic membranes nowadays come in the form of a monolith consisting of multiple, straight channels parallel to the axis of the cylindrical structure (Figure 3.6). The surfaces of the open channels are deposited with permselective membranes and possibly one or more intermediate support layers. The porous suppon of these multi-channel structures are produced by extrusion of ceramic pastes described above with a channel diameter of a few millimeters. Their lengths are somewhat limited by the size of the furnaces used to dry, calcine and sinter them and also by such practical considerations as the total compact weights to be supported during heat ueatment and the risk of distortion in the middle section. It should be noted that this type of honeycomb... 

The porous mass of the monolithic structure has a low pressure drop. If further reduction of the pressure drop in the bulk support is desired, there arc a few possibilities [Atomic Energy Commission (France), 1971]. Additional grooves can be machined or swaged with dowels which will produce channels, or a network of additional channels perpendicular to the honeycomb feed channels is provided by using materials such as carbon that can be burned off. 

A generalization of this concept of a monolithic multi-channel honeycomb structure is described in a patent by Hoover and Roberts [1978]. An integral support of porous ceramic material has a multiplicity of parallel passageways (or open channels). These passageways are substantially uniformly spaced. On the surface of these channels are coated with a permselective membrane layer. The feed stream flows inside the channels. The membrane, being the first layer in direct contact with the process stream, is selective to one or more species in the stream. In the normal cases of properly weued membrane pores, the permeate under a driving force will uansport through the membrane, any... 

The substrate is an integral part of the catalytic converter system. Its primary function is to bring the active catalyst into maximum effective exposure with the exhaust gases. In addition, it must withstand a variety of severe operating conditions, namely, rapid changes in temperature, gas pulsations from the engine, chassis vibrations, and road shocks. As noted earlier, pellets of cylindrical and spherical geometry and honeycomb monoliths both became available for catalyst supports. 

Composite ceramic monolith catalysts are also included among the commercial SCR systems. They are manufactured by depositing a layer of catalytic ingredients onto strong, thin-walled ceramic honeycomb supports (usually cordierite). They may suffer from erosion problems in the presence of dust, and their use may be preferably limited to a clean environment. 

---