Catalyst denitrification

Hydrogenation reactions, particularly for the manufacture of fine chemicals, prevail in the research of three-phase processes. Examples are hydrogenation of citral (selectivity > 80% [86-88]) and 2-butyne-l,4-diol (conversion > 80% and selectivity > 97% [89]). Eor Pt/ACE the yield to n-sorbitol in hydrogenation of D-glucose exceeded 99.5% [90]. Water denitrification via hydrogenation of nitrites and nitrates was extensively studied using fiber-based catalysts [91-95]. An attempt to use fiber-structured catalysts for wet air oxidation of organics (4-nitrophenol as a model compound) in water was successful. TOC removal up to 90% was achieved [96]. 

Fig. 6.9 The catalysts for denitrification. Nitrate is reduced by a molybdenum enzyme while nitrite and oxides of nitrogen are reduced today mainly by copper enzymes. However, there are alternatives, probably earlier iron enzymes. The electron transfer bct complex is common to that in oxidative phosphorylation and similar to the bf complex of photosynthesis, while cytochrome c2 is to be compared with cytochrome c of oxidative phosphorylation. These four processes are linked in energy capture via proton (H+) gradients see Figure 6.8(a) and (b) and the lower parts of Fig. 6.9 which show separately the active site of the all iron NO-reductase, and the active site of cytochrome oxidase (02 reductase).

This may be of relevance if a possible implementation mode involves integrated ion-exchange/catalytic denitrification process where NaCl is used as background electrolyte. High chloride levels may also lead to catalysts poisoning, possibly due to metal corrosion. Although sulfide is also... 

The technology s bacteria act as metal and radionuclide adsorbers and also as denitrification catalysts that reproduce themselves at ambient temperature and pressure. 

Packed Bubble Bed Reactor (BBR) This is a tubular flow reactor with concurrent up-flow of gas and liquid (Figure 3.11). The catalyst bed is completely immersed in a continuous liquid flow while gas rises as bubbles. Some applications of BBR are the catalytic denitrification of aqueous nitrate solutions and the hydrogenation processes. 

Figure 3 shows a plot of the first-order denitrification rate constants vs. time on-stream at an operating pressure of 1500 psig. The catalysts with the highest initial denitrification activity at 1500 psig were catalyst... 

V (Ni-Mo) and the lowest yields with catalysts III (Ni-W) and IV (Ni-W). The highest conversion, i.e., material converted to products boiling below 550°F, was attained with catalyst VI (Ni-Co-Mo). The lowest conversion was attained with catalyst IV (Ni-W), a hydrocracking catalyst. The highest yields of naphtha and light oil were attained with catalysts I (Co-Mo) and VI (Ni-Co-Mo). Because of its high sustained denitrification activity, catalyst V (Ni-Mo) was selected for use in the preparation of syncrude by hydrogenation of the in situ distillate fractions. 

The inherent ability of selective catalytic reduction (SCR) catalysts for stack gas denitrification to store ammonia adsorptively can be exploited with appropriate control algorithms to damp out the influence of fluctuations in the amount of gas and level of nitrogen oxides being treated. Moreover, it also forms the basis of the adsorptive reactor concept for the total denitrification of flue gases without ammonia... 

The first run with ICR 106 catalyst (Run 81-4) was a 2000-hr test made in a relatively small pilot plant containing 130 mL of catalyst to determine denitrification kinetics and hydrogen consumption. Activity data are plotted in Figure 1 for 0.2, 0.3, and 0.6 LHSV. A simple first-... 

Reduction of NO to N20 or N2 is important in biological denitrification where anaerobic organisms are involved and model studies using copper catalysts have been studied.42 Much study on other catalytic reductions of NO (and of N02) has been made in connection with atmospheric pollution.43... 

Weisweiler, W. Environmentally friendly denitrification catalysts based on iron/manganese oxide/sulfate for use in simultaneous denitration and desulphurization of waste gases in a circulating fluidized bed, DECHEMA Monogr., 118 (Katalyse), pp. 81-103 (1989). 

The selective catalytic reduction (SCR) is the only flue gas denitrification technique so fer that has proven to be very effective. It has been extensively studied, successfiilly commercialised and applied on a large scale [2], Carbon can be used as catalyst in the SCR unit at lower temperatures than those used with conventional SCR catalysts. 

Nitrous oxide (N2O). The major source of atmospheric N2O is denitrification occurring in wet, nitrate-rich soils. N2O is a relatively unreactive and persistent gas in the atmosphere. However, N2O is very slowly oxidized to NO gases under the influence of sunlight and atmospheric catalysts. 

As was expected, demetallation/denitrification of the feed stock was substantially lower than that for Catalyst Systems B and C. Even though product pattern with this system was superior, short catalyst cycle length and consequently limited On-Stream Factor (OSF) weighed heavily against it. Short catalyst cycle length was operationally uneconomical due to frequent shut downs. 

Catalyst System-C incorporated Denitrification catalyst intended to lower Nitrogen in VGO (Hydrocracker Feed stock). The advantages over Catalyst System-B, if any, was not clear. Higher Distillate stability was expected but could not be substantiated. Distillate yield was comparable with that of Catalyst System-B. 

Fibrous catalysts were tested for intrinsic activity and selectivity in the liquid-phase hydrogenation of citral [134], benzaldehyde to toluene [63], nitrobenzene to aniline, and for the denitrification of water [135-137]. Palladium catalysts were found to be highly effective for these transformations. 

Y. Matatov-Meytal, V. Barelko, I. Yuranov, L. Kiwi-Minsker, A. Renken, M. Sheintuch, Cloth catalysts in water denitrification. II. Removal of nitrates using Pd-Cu supported on glass fibers, Appl. Catal. B Environ. 31 (2001) 233. 

Essentially all of the conversion of 650°F plus bottom material to transportation fuel occurs in the hydrotreating step. Table II compares the overall material balance and yield and nitrogen levels obtained at Toledo with original pilot plant results. These data indicate that the denitrification activity of the catalyst was consistent with prior results, however the apparent yield structure was different. The differences in yields are attributed to two factors (1)... 

Denitrification [the conversion of NOs to N2(ag>] is a common reaction catalyzed by many bacteria and proceeds rapidly. However, it appears that microbial catalysts are unable to catalyze the reverse of the denitrification reaction (Ngca, ) — NOs ). 

The common key issue in all three examples is a catalyst. While a catalyst for WO does not need to be selective, denitrification of drinkable water and preferential oxidation of... 

Pump it into a desulfurization system. Nothing new is injected here, it just has a different catalyst than the denitrification, and the substrates are at a different temperature and pressure. 

Flue gas purification (SCR) removal of NO ,- with NH3 Ti, W,V mixed oxides as honeycomb bulk catalysts Ti, W,V oxides on inert honeycomb supports hot denitrification (400 °C) cold denitrification (300 °C... 

Combined denitrification and desulfurization (DESONOX process) SCR catalyst + V2O5 honeycomb catalyst, catalyst bed up to 450 °C... 

---