Monolith coating

Lenz and Aicher reported the experimental results obtained with an autothermal reformer fed with desulfurized kerosene employing a metallic monolith coated with alumina washcoat supporting precious metal catalysts (Pt and Rh) [78]. The experiments were performed at steam-to-carbon ratios S/C = 1.5-2.5 and... 

The differences in reactions at different reactor positions was studied by Springmann et al. who reported product compositions for ATR of model compounds as a function of reactor length in a metal monolith coated with a proprietary noble metal containing Rh. As expected, the oxidation reactions take place at the reactor inlet, followed by the SR, shift, and methanation reactions. Figure 32 shows the product concentration profiles for a 1-hexene feed, which are typical results for all the fuels tested. These results show that steam, formed from the oxidation reactions, reaches a maximum shortly after the reactor inlet, after which it is consumed in the shift and reforming reactions. H2, CO and CO2 concentrations increase with reactor length and temperature. In this reactor, shift equilibrium is not reached, and the increase in CO with distance from the inlet is the net result of the shift and SR reactions. Methane is... 

Figure 7.14 Chromatogram of (1) uracil, (2) phenol, and (3) benzyl alcohol on C3 porous polymer monolith coated chip [33].

Vasishtha, M., Sundberg, D.C., and Rittschof, D., Evaluation of release rates and control of biofouling using monolithic coatings containing an isothiazolone, Biofouling, 9, 1, 1995. 

Mazzarino and Baldi [27] investigated hydrogenation of a-methylstyrene into cumene, using a ceramic monolith coated with Pd (1% of active metal). They studied the... 

EDX mapping of the cross section of a cordierite (Mg2AUSi50i8) monolith coated... 

If the flooring undergoes temperature cycling, a monolithic coating which is bonded to the steel will develop cracks because of the considerable differences in coefficients of thermal expansion. This can be prevented in the case of a brick flooring, which is not bonded and is free to slide by providing expansion joints in the brickwork. 

Steel decking transmits vibrations which have been known to crack plastic monolithic coatings and brickwork. 

The hydrolysis and condensation of silicon alkoxides is an area of intense interest. The sol-gel process uses high-purity monomers for low-temperature production of fibers, monoliths, coatings, and powders. Structures of the polymers produced in the sol ultimately dictate both gel and glass properties. 

Results. The monolithic coating of the spray formulation applied to the double pond covered both the liquid-containing area, the top and outside edges, and also formed the spillway between the two ponds. After several days, some cracks developed in the coating at the top inside... 

Fig. 1 Schematic presentation of the CVD reactor and photograph of (a) non-coated monolith, (b) monolith coated in the isothermal CVD reactor and coated with (c) thin and (d) thick cobalt oxide layer using a temperature-gradient of 3 °C/cm along the monolith, which has a length of 5 cm. The exhaust-side has the highest temperature 230 °C.

Almost all commercial heterogeneous catalytic reactions are conducted with a contact time of at least several seconds. Many require much longer contact time. There are, however, a few commercial catalytic processes in which the reaction is completed in a very short time (order of milliseconds). These very fast reactions are usually affected by heat- and mass-transport resistances. They are usually carried out either on catalytic gauzes or on a reticulated structure or monolith coated with a very thin washcoat on which a catalyst is impregnated. 

Aderhold, D., Haynes, A.G., Spencer, ML.W. Winterbom D.J.W. (2003). Monolith coating apparatus and method therefore, US Patent 6,599,570 0ohnson Matthey). 

Karatzas et al. [34] performed autothermal reforming of tet-radecane, low sulfur, and Fischer-Tropsch diesel in a monolithic reformer over rhodium/ceria/lanthana catalyst. The reformer had a thermal power output of 14 kW. It was composed of an inert zirconia-coated alumina foam for feed distribution at the reactor inlet and two 400 cpsi cordierite monoliths coated with the catalyst switched in series. At an O/C ratio of 0.45, a S/C ratio of 2.5 and temperatures exceeding 740°C, full conversion of the low sulfur feed was achieved, while the formation of the byproduct ethylene was between 100 and 200 ppm. As shown in Figure 14.7, an increasing S/C ratio suppresses ethylene formation. The catalyst showed stable performance for 40 h duration. Karatzas et al. [44] determined experimentally as shown in Figure 14.8 that the efficiency of their ATR increased with increasing fuel inlet temperature and O/C ratio. 

Adachi et al. [168] developed a model for a natural gas fuel processor composed of an ATR designed as metallic foam monolith coated with catalyst and two-stage WGS reactors also designed as foam monoliths followed by two-stage ceramic monoliths for the preferential oxidation of carbon monoxide as shown in Figure 14.27. Figure 14.28 shows the course of temperature and gas composition of feed and reformate as calculated for... 

Acrylic monolithic coatings are suitable for interior or exterior applications with relatively benign atmospheric exposures. Refer to Table 18.5. They excel at water and weather resistance, and are best at breathing in the presence of a moisture transmissive problem in the slab. They are intended for protection against moderate corrosion environments. The advantages for their use are as follows ... 

The homogeneity of the distribution of metal species has also been tested by binding Cr(acac)3 on a large-scale monolith coated with an alumina-based mixed oxide (see Figure 10) [37]. Samples, six in total, were taken at three different radial positions and two different axial positions of the monolith, and analysis gave an average of 1.0 0.1 wt-% chromium. 

Figure 10. Reaction of Cr(acac)3 on a large-scale monolith coated with an alumina-based mixed oxide. Cr was determined in samples kiken from six different positions on the monolith [37].

Liguras et al. investigated autothermal reforming of ethanol over ruthenium and nickel catalysts on structured supports such as ceramic foams and monoliths [212,213]. Conditions chosen were an O/C ratio of 0.61 and an S/C ratio of 1.5. The reaction was performed at a very high pre-heating temperature of the monoliths and consequently substantial conversion occurred even upstream of the reactor, which created a hot spot of up to 950 °C in the monoliths. A ceramic monolith coated with 5 wt.% ruthenium formed in addition to carbon oxides methane as the main byproduct, but there were also small amounts of acetaldehyde, ethylene and ethane [212]. When the S/C ratio was increased to 2.0, the by-products could be suppressed. Increasing the O/C ratio had a similar effect and also suppressed the methane formation. The ruthenium catalyst showed stable conversion for a 75-h test duration. Nickel/lanthana catalysts containing 13 wt.% nickel on a lanthana carrier showed similar performances with respect to activity, selectivity and stability [213]. 

Figure 4.23 shows the comparison of a fixed-bed reactor filled with iron/chromium catalyst with a monolith coated with precious metal water-gas shift catalyst. At... 

Figure4.23 Comparison of carbon monoxide conversion overofa fixed bed of iron/chromium catalyst operated at 4500h gas hourly space velocity and a monolith coated with precious metal catalyst operated at 45 000h for reformate containing 5.9% carbon monoxide, 7.4% carbon dioxide, 31.7% hydrogen, 28.8% nitrogen and 26% steam [57].

Springmarm et ol. [152] simulated a 10-kWei autothermal reformer for gasoline with a one-dimensional, dynamic model. The reformer was a metallic monolith coated with precious metal catalyst. The reformer consisted of two parts both of 70-mm diameter, a small electrically heated monolith only 5-mm long (400 cells per square inch or about 1300-pm channel size) and a second, about 100-mm long monolith (1600 cells per square inch or about 630-pm channel size). Both monoliths were coated with the same catalyst Kinetic data were determined prior to the simulations [56] and heat losses were estimated for the reactors, which is a critical issue. The reformer was operated at a S/C ratio of 2 and an O/C ratio of 0.75. The pressure was 4bar and the feed inlet temperature 500 °C. 

Monolith reactor model—For validation purposes, the kinetic models of the SCR catalyst [6] and of the PGM catalyst [18] were used to simulate catalytic activity runs over honeycomb monoliths coated with the SCR and the PGM component, respectively, of the studied ASC system. In the case of the SCR catalyst, the kinetics were implemented in a heterogeneous dynamic ID -I- ID model of a single monolith channel, accounting both for external (gas-solid) and internal (intra-porous) mass transfer resistances [12, 25, 26]. Model simulations... 

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