Catalyst bed length

The results of catalytic activity tests are reported in Figure 9.13a in terms of the temperature profile as a function of the catalyst bed length and in Figure 9.13b in... 

The catalyst bed length for the demonstration test was set at the likely length for a commercial plant. For the demonstration unit, the internal diameter was selected to be about 10 cm, which is significantly larger than catalyst particle size to minimize wall effects. In addition, heat transfer along the reactor wall would also be negligible. 

Transport effects should be avoided in qualitative analysis and kinetic studies [7]. This is accomplished by using small particles (100 pm), the ratio of reactor diameter to particle size dt/dp should be larger than 15, and the ratio of catalyst bed-length to the particle diameter should be larger than 20. It is also well known that the amount of sample influences the TPR profile resolution [8], i.e. multiple... 

Meats23-2 showed that the catalyst bed-length effect observed during de-nitrogenation of gas oils in pilot-scale reactors can be correlated on the basis of an axial dispersion effect on the reactor performance. Montagna and Shah29 showed that the bed-length effect observed in desulfurization reaction with 22 percent KVTB and 36 percent KATB (see Fig. 4-4) can also be explained on the basis of an axial dispersion effect on the reactor performance. 

Figure 4-19 Percentage desulfurization versus catalyst bed-length and liquid flow rate.

Control of the temperature throughout the reforming catalyst bed can be established by use of a monolithic catalyst. The heat transfer control can be accomplished by combining three effects that monolithic catalyst beds can impact significantly (1) direct, uniform contact of the catalyst bed with the reactor wall will enhance conductive heat transfer (2) uniformity of catalyst availability to the reactants over the length of the flow will provide continuity of reaction and (3) coordination of void-to-catalyst ratio with respect to the rate of reaction will moderate gas-phase cracking relative to catalytically enhanced hydrocarbon-steam reactions. This combination provides conditions for a more uniform reaction over the catalyst bed length. 

Uniformity is particularly important for MTG because of its extremely high conversion level requirements (Fig. 5). MTG scale-up was conducted with catalyst bed lengths approximately equal to that expected for a commercial size reactor (ref. 9). 

Total Molar Feed Mass Flow Rate Inlet Pressure Inlet Temperature Catalyst Bed Diameter Catalyst Bed Length Catalyst Bulk Density Catalyst Particle Diameter... 

In fixed-bed reactor technologies, an important factor is the pressure drop over the catalyst bed. In order to minimize the mass transfer effects, knitted silica fiber catalysts having small diffusion distance (< 10 pm) and low pressure drop, were applied in this study. 10 layers (0.4 g) of the catalyst was placed in the reactor between stainless steel nets and glass beads were used as inert packing material. The catalyst layer thickness was 0.15 cm resulting in catalyst bed length of... 

The determination of the number and position of unsaturated bonds in components of a sample mixture is one of the most important tasks in identifying unknown compounds. This is essential, first, for the correct choice of the conditions under which the samples must be chemically treated in order to avoid side-reactions that often occur with unsaturated bonds. At present the GC determination of unsaturated bonds is almost exclusively based on the hydration method, which simplifies chromatograms of complex mixtures [223]. The position of double bonds in a molecule is detected by oxidation methods. In principle the hydration method has much in common with that for determining a carbon skeleton as far as the catalysts, equipment and analytical techniques are concerned. The main differences are lower temperatures and shorter catalyst beds. Thus, the catalyst bed length can be 5—10 cm [224—226] and even several millimetres, which allows the hydration to be run directly at the point of sample injection into the... 

Catalytic stability of a Pd/H-Mordenite catalyst for C5/C6 hydroisomerization was tested in a laboratory reactor for 1000 hours. The content, chemical composition and structure of the coke formed on the catalyst discharged from a pilot reactor working in an accelerated condition was characterized using XRD, EPR, MAS-NMR, FTIR and TPO techniques. The catalyst shows stable catalytic activity and selectivity during 1000 hours. The nature of the coke and its combustion behavior depended upon time on stream and varied with the catalyst bed length. As time on stream increased, coke initially formed on palladium metals and then moved to acidic sites on the support where polyaromatic or pseudographite-like structures were formed through further acid catalyzed reactions. 

The model fits the experimentally observed coke profile well, although the predictions are generally lower than the measured values. Both the model and experimental data show a coke profile that decreases along the catalyst bed length. This decreasing profile supports the assumption that coke is formed from an early intermediate in the reaction network. 

Apart from the above criterion that compares the reactor tube diameter to the pellet diameter, also the catalyst bed length should be compared to the catalyst pellet diameter. The latter comparison is related to the assessment of the importance of effective axial diffusion phenomena. The catalyst bed length required to achieve a given conversion increases with the importance of the latter. Comparison of the reactor lengths required in the absence and presence of effective axial diffusion is the basis of a criterion ... 

The catalytic activities were evaluated in a fixed-bed reaction system at atmospheric pressure. 100 mg of the catalyst diluted with 100 mg of SiC was loaded into a quartz reactor with the catalyst bed length of 10 mm. A total gas flow rate of 66.7 ml min was employed, corresponding to a space velocity of 40,000 ml h g cat - Prior to each test, the catalyst was reduced in situ with hydrogen at 300°Cfor 2 h. The feed gas mixture was composed of 2 vol% CO, I vol% O2, xvol% H2 (x = 0-40), and balance He. In some cases, I0vol% water was also introduced to the feed gas. The effluent gas was analyzed using an online gas chromatograph (Agilent GC-6890) equipped with a thermal conductivity detector. 

Figure 2.1.1. Effect of liquid space velocity and catalyst bed length on hydrocracking in trickle beds (after Henry, H. C. and J. B. Gilbert [23]),...

In these expressions and C are the inlet and outlet concentrations of the key component k, the first order kinetic constant SV, space velocity W, a constant Z, the catalyst bed length dp, the catalyst particle diameter y, liquid viscosity and 0, 0, the surface tension of water and the liquid. 

Axial distance down the bed necessary to achieve even liquid distribution, cm Catalyst bed length, m... 

A pillar structure of small rectangular posts was incorporated near the outlet of the reaction channel to retain the catalyst. The reaction was studied in the temperature range of 80-120 °C and at inlet pressures up to 5 bar. Benzyl alcohol conversion and benzaldehyde selectivity at 80 and 120 °C were very close to those from conventional glass stirred reactors. The best conversion of benzyl alcohol of 95.5% with selectivity to benzaldehyde of 78% was obtained for a micropacked bed reactors with catalyst sizes of 53-63 pm and a catalyst bed length of 48 mm at 120 °C and 5 bar. The effect of catalyst particle size on the reaction was examined with two ranges of particle size 53-63 pm and 90-125 pm. Lower conversion was obtained with particle sizes of 90-125 pm, indicating the presence of internal mass transfer resistances. In situ Raman measurements were performed and could be used to obtain the benzaldehyde concentration profile along the catalyst bed. 

The cocurrent flow makes it possible to obtain a temperature profile which is close to the optimum the gas is heated adiabatically to a temperature close to the maximum reaction rate curve, and the temperature/conversion profile then follows closely the maximum rate curve for the test of the catalyst bed length. 

FIGURE 7.15 Sulfur profiles along the catalyst bed length in the bench-scale trickle-bed reactor at different times. (— -) 60s, ( ) 400s, (-X-) 900s, (-1700s, and (o) experimental value. 

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