Coated monoliths

Figure 12.9-6. A small prototype unit (a) consists of a fan and coated monolith was placed in a test chamber shown in (b) and tested for VOC removal at ambient conditions, (c) The results show that the VOC level was decreased by half in less than an hour.

Poly-(N,N-dipyrid-2-yl-7-oxanorborn-2-en-5-ylcarbamido PdCl2)-coated Monolithic Supports for Heck Reactions... 

In recent years, several proposals have been made for the numerical simulation of SCR catalysts, primarily of coated monoliths [59, 60], and for control-oriented purposes [61]. 

FIGURE 14.5 Analysis of rainwater spiked with 0.3 mM H+, Na+, NHJ, K+, Ca +, Mg +. Column DS-coated monolithic stationary phase (Merck Chromolith, 50x4.6mm). Column temperature 35°C. Eluent 2mM ethylenediamine, 0.1 mM Li-DS, pH 6. Flow rate 4.0mL/min. Loop volume lOOpL. (From Xu, Q. et ah, J. Chromatogr. A, 1026, 191, 2004. Copyright 2004. With permission from Elsevier.)... 

M.C. Huff and L.D. Schmidt. Elementary Step Model of Ethane Oxidative Dehydrogenation on Pt-Coated Monoliths. AIChE J., 42 3484-3497,1996. 

Most of the experiments were carried out in a pilot-scale reactor (Fig. 8.25). For each experiment, four pieces of coated monoliths were stacked carefully in line and mounted in a 2 m- high heated column of 50 mm diameter. The preheated liquid feed was distributed via a spray nozzle. After each pass, the liquid was collected in the liquid-supply vessel and was circulated continuously through the reactor (batch-recycle mode). The preheated countercurrent nitrogen stream was fed after one pass to a condenser to separate the liquid, and then vented. The condensables were collected in a phase separator, from where the water could be tapped off, whilst the... 

For the experiments with increased water content or suppressed water removal, a 5 cm-long piece of coated monolith was mounted in a 500-mL autoclave. All liquid concentrations, operation conditions and catalyst hold-up were the same as in the pilot-scale plant. To maintain a gradient-less operation, a turbine-type stirrer recirculated the liquid very rapidly through the monolith channels. During the experiments, liquid samples were taken from the reactor and analyzed as described above. 

Experiments in a pilot-scale plant demonstrated the feasibility of applying coated monoliths and DX packings or katapak-S successfully as catalyst carriers in reactive stripping. It was proven that the water removal increases the catalyst activity and permits a shift" in the equilibrium. In accordance with the kinetics of this... 

The various aspects that are to be considered to achieve a proper and efficient catalyst testing approach are presented. This applies to heterogeneous systems in which the catalyst is the solid phase and the reactants are in the gaseous and/or the liquid phase. The presence of a solid phase introduces complicating phenomena on which this chapter focuses. In this respect, homogeneous catalysis is a limiting case and does not need separate treatment. The solid catalyst can be present as either a packed bed of particles, a wash-coated monolith, a fluid bed, an entrained bed, or in a liquid-phase slurry. 

Tubular reactors are probably the most common photocatalytic reactors. Their popularity stems, most likely, from their simplicity. They are characterized by a gas flow along the axis of a tube, which contains the photocatalyst in many possible forms such as a thin coated film on its wall, fluidized particles, a coated monolith, or even as a free powder resting on an appropriate support. The light sources are located, in most cases, externally to the tube, in a parallel configuration relative to its axis. Reflecting surfaces encompass the lamps array, assuring that the only absorbance of photons would be that of the photocatalyst (Figure 7). 

TABLE 3 Textural Properties of 200 cpsi Carbon-Coated Monoliths. 

Extensive investigations were performed to determine the potential of carbon-coated monoliths as supports for enzymes. The enzymes were adsorbed on the functionalized supports under ambient conditions, in a recycle reactor in which the liquid was recycled over the support under upflow conditions. A 50 mM phosphate buffer with pH 7 was used as a medium. The protein concentration was determined by using UV-VIS... 

In comparison with fixed beds consisting of catalyst particles, coated monoliths have the advantage of a tunable catalyst layer thickness, decoupling the internal diffusion distance within the catalyst from the external surface area. However, mainly as a consequence of the square channel geometry in commercially available monoliths, the thickness of the... 

FIGURE 37 SEM image after coating of the a-Al203 coated monolith with silica (left) and carbon (right). Note the well-defined thickness of these support layers ( 10 pm). 

Ga.s S5mthesis and application of carbon monoliths Environmental, VOC Oxidation of xylenes Low-temperature combustion Carbon-coated monolith (165,166)... 

Vergunst, Th. Carbon coated monolithic catalysts—preparation aspects and testing in the three-phase hydrogenation of cinnantaldehyde. 1999, PhD Thesis, Delft University of Technology. 

Figure 5 Campaign with the conti reactor first quasi-continuous production of hydrogen mass flow of hydrogen for 13 cycles during the first day of testing of two coated monoliths.

Hickman and Schmidt (158,159) thoroughly studied Eq. (33) over Pt-and Pt-Rh-coated monoliths and gauzes. Best results are obtained at about 1100°C with residence times of lO " to 10 s. High flow rates minimize mass transfer effects. Since the gas at the exit of the reactor is almost in... 

Several catalysts with the above washcoats were thermally cycled at successively higher temperatures until failure occurred. An acoustic technique was employed to detect invisible fractures. The failure temperature (7 ) obtained in this manner is plotted against the TSP value in Fig. 22 for each of these coated monoliths. Also included in these data... 

The American 1970 Clean Air Act defined ambient air quality standards (NAAQS) in the United States for atmospheric ozone, NO, lead, carbon monoxide, sulfur oxides, and PM-10 (particulate matter less than 10 p.m). The strategy to reduce levels of lead, NOx, PM-10, and to some extent carbon monoxide was to control emissions from automobiles that included the phasing-out of leaded fuel. As previously noted, ozone is a product of the photochemical reaction of volatile organic compounds with NOx (photochemical smog), so the balance between organic compounds and NOx pollutants is important in meeting target ozone levels (e.g., 0.12 ppm). Emissions from stationary sources is an important factor, and limits have been set for them. Because of low pressure drop requirements, coated monolithic catalysts... 

J.E. Aniia and R. Govind, Conversion of methanol to gasoline-range hydrocarbons in a ZSM-5 coated monolithic reactor, Ind. Eng. Chem. Res. i4 140 (1995). 

With thermal durability under control, the mechanical durability takes on a major focus to ensure total durability. To this end, it is necessary to ascertain high mechanical strength of the coated monolith, build in a resilient packaging system, and ensure positive and moderately high mounting pressure to guard against vibrational and impact loads. Much like automotive catalysts, the D(Xs can continue to function catalytically even in... 

Catalytic cross-flow reactor Calcium aluminum silicate H2 diffusion in liquid-filled pores Hydrogenation of p-nitrobcnzoic acid Pd-coated monolith wall 60 ... 

Sometimes, other support materials besides oxides, e.g., carbon, are attractive and advantageous for various reasons. In fine chemicals production a lot of experience exists with carbon-supported catalysts. Often they show good performance, and a high intrinsic activity is observed. Carbon support is pronounced for a weak interaction with the active phase and has a high surface area. An often-cited disadvantage of conventional carbon support is its mechanical weakness. Carbon-coated monolith can overcome this disadvantage due to the strength of the monolithic substrate. 

Our preliminary results of nickel on carbon-coated monolithic catalysts show that in a hydrogenation reaction it is five times more active than the corresponding nickel on alumina-washcoated monolithic catalyst without carbon coating. 

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