Honeycomb activity tests

Figure 20 shows the results of an activity test of a honeycomb element and the analysis of unreacted ammonia. 

The characterization of the sintered catalysts was extended in the present paper to the analysis of the performance of honeycomb monoliths under operating conditions of real industrial interest. Interpretation of DeNOx and SO2-SO3 activity tests was supported by means of a complete model of the SCR process, which has been developed and widely verified in previous works [6]. 

Ham et al. (99) have studied the effect of S02 in the temperature range 523-723K. Below 573 K a decrease of activity by 60% at 523 K and 20% at 573 K occurs, while above 573 K no inhibition was observed. During the tests at low temperature with S02, accumulation of ammonium sulfate and/or ammonium bisulfate occurs and may cause severe blocking. At higher temperatures these salts decompose and this may explain the absence of inhibition. Complete regeneration of deactivated catalysts can be achieved by heat treatment at 773 K. Over Cu-H-MOR bound with silica and deposited on a cordierite honeycomb, only 12% decrease of NO conversion was observed at 673 K after 350 h passivation in presence of 200... 

Many desirable characteristics of honeycomb monolithic catalyst beds were illustrated by these two examples (1) catalyst loading lower than on pellets was adequate to maintain activity (2) the axial heat transfer rate resulted in rapid heat dissipation from the reaction zone (3) a vanation of void-to-caialysi-surface ratio with new turbulent interfaces at each interval introduced a convenient control over the extent of reaction. Two other variables that were investigated are loading of catalyst over bed length and type of catalyst used however, the comparative analyses have not been as systematically demonstrated for the particular operation described in these tests. 

From this catalyst performance test the lifetime of SCR catalysts may be predicted, thus providing a replacement strategy for SCR elements. Honeycomb elements or plate-type elements are placed in the oven of a bench-scale setup. With this method the integral activity of an element is obtained. 

Meijer and Janssen [131] described tests to evaluate issues such as activity, selectivity, fouling lifetime of the catalyst, the surface composition and concentration profiles in depth of honeycomb catalysts. 

The important role of honeycomb structures which minimise the pressure drop is well known in recent years this has lead to the development of various time consuming and expensive preparation methods for the manufacture of these types of supported catalysts. Their improvements were directly related to well defined catalytic processes in which not only the composition but also the structural and textural aspects must be studied to optimise the catalytic behaviour [1-3], Nevertheless, technical or economical reasons may frequently negate their use at industrial scale [4-6]. Moreover, the external morphology in which an industrial catalyst may be cast is imposed by the industrial reactor setup, and sometimes an effective laboratory tested catalyst may suffer a loss in activity when moulded with a specific geometry for industrial application. 

This report is concerned with the preparation and testing of small honeycomb catalysts with Co304 or copper chromite as the active phase. With Co304, the oxidation of C2H4 is one of the more difficult reactions to catalyze. Both CO and the higher molecular weight hydrocarbons (unburned fuel) are more readily oxidized (21). C2H4 is one of the main constituents of cracked fuel from the cylinder quench layer. 

First, the activity of base metal honeycombs tested for CO oxidation was good with the temperature of 50% conversion at 80,000/hr space velocity being about 260°C after aging 16 hrs at 815°C. This is comparable to the activity of honeycombs containing Pt that are presently being used. 

The CVS test findings depend on whether the honeycomb has been subjected to idle conditions (the 427°—538°C temperature is not high enough to remove the S from the oxide surface) or to high temperatures (>700°C) which remove the S before the test is run. In the test, the catalyst should reach a temperature >700°C quickly (in several minutes) in order to maintain its activity if it started out free from sulfur. 

The activity of the 4.5-in. honeycombs with copper chromite as the active catalyst, when mounted 4 in. from the exhaust flanges of a vehicle and when used with low sulfur fuel (144 ppm S), appears to be somewhat less than that of a Pt honeycomb (for which we would expect >90% CO conversion and >80% HC conversion in the tests of Table VII). 

The hexaaluminate mentioned above was employed for the test apparatus of 160 kW prototype combustor gas turbine by cooperative work of Kobe Steel and Osaka Gas and Catal. Chem. Inc., Far East (Figure 16). The combustor consisted of seven series-arranged catalyst honeycombs with different activities and thermal stabilities depending on... 

Catalyst - The catalyst herein under study is a commercial Ti-W-V catalyst with 9-weight % of WO3 and about 0.6 % of V2O5. Monolith channels had an opening of 0.415 cm and a wall thickness of 0.08 cm. Sample honeycomb monoliths were cut with a cross section of 3x3 channels and length of 15 cm, calcined for 2 hours at 500, 750 and 800°C and loaded in the reactor for DeNOx testing. The monoliths were instead crushed into granules of 1-1.5 mm diameter and tested in a separate rig for SO2-SO3 activity measurements. 

Thermal testing Voids or disbands in both metallic and nonmetallic materials, location of hot or cold spots in thermally active assemblies Laminated structures, honeycomb, and electronic circuit boards Produces a thermal image that is easily interpreted Difficult to control surface emissivity poor discrimination... 

The effectiveness of the Pt-modified diamond electrodes for the electrocatalysis of fuel cell reactions was examined. We have tested their electrocatalytic activities for O2 reduction and alcohol oxidation. Figure 19.7 compares O2 reduction currents for the as-deposited diamond, the as-deposited diamond/Pt, honeycomb 60 x 500 nm/Pt and the 400 nm x 3 xm/Pt electrodes in 1 M H2SO4... 

---