Zeolite with ammonia over

Amination with ammonia over zeolite catalysts at 350-400°C to give methylamine (and some dimethylamine) ""... 

The synthesis of ethylenediamine (EDA) from ethanolamine (EA) with ammonia over acidic t3pes of zeolite catalyst was investigated. Among the zeolites tested in this study, the protonic form of mordenite catalyst that was treated with EDTA (H-EDTA-MOR) showed the highest activity and selectivity for the formation of EA at 603 K, W/F=200 g h mol, and NH3/ =50. The reaction proved to be highly selective for EA over H-EDTA-MOR, with small amounts of ethyleneimine (El) and piperazine (PA) derivatives as the side products. IR spectroscopic data provide evidence that the protonated El is the chemical intermediate for the reaction. The reaction for Uie formation of EDA from EA and ammonia required stronger acidic sites in the mordenite channels for hi er yield and selectivity. 

Reactions of Aromatic Compounds with Ammonia over Y Zeolite... 

The reactions of chlorobenzene and benzaldehyde with ammonia over metal Y zeolites have been studied by a pulse technique. For aniline formation from the reaction of chlorobenzene and ammonia, the transition metal forms of Y zeolites show good activity, but alkali and alkaline earth metal forms do not. For CuY, the main products are aniline and benzene. The order of catalytic activity of the metal ions isCu> Ni > Zn> Cr> Co > Cd > Mn > Mg, Ca, Na 0. This order has no relation to the order of electrostatic potential or ionic radius, but is closely related to the order of electronegativity or ammine complex formation constant of metal cations. For benzonitrile formation from benzaldehyde and ammonia, every cation form of Y zeolite shows high activity. 

To manufacture aniline from chlorobenzene and ammonia, cuprous oxide or diamino cuprous chloride has been used as the catalyst and the reaction is usually carried out in the liquid phase under pressure (7). There are few reports on the reaction in gas phase. Jones (8) found that CuX was active for aniline formation while ZnX led to the formation of dichlorobenzenes. The reaction of benzaldehyde with ammonia over zeolite has never been reported. 

Ito, E., R.J. Hultermans, P.M. Lugt, M.H.W. Burgers, H. van Bekkum and C.M. van den Bleek, 1995b, Selective reduction of NO, with ammonia over cerium exchanged zeolite catalysts - Towards a solution for an ammonia slip problem, in Catalysis and Automotive Pollution Control III, eds A. Frennet and J.-M. Bastin, Vol. 96 of Studies in Surface Science and Catalysis (Elsevier, Amsterdam) pp. 661—673. 

SELECTIVE REDUCTION OF NOx WITH AMMONIA OVER CERIUM EXCHANGED ZEOLITE CATALYSTS TOWARDS A SOLUTION FOR AN AMMONIA SLIP PROBLEM... 

Figure 2. NO reduction with ammonia over different cerium exchanged zeolites NO 1000 ppm, NH3 1000 ppm and 5% O2 at GHSV of 30,000 h . (0) CeNa-MOR(70), (O) CeNa-ZSM-5(95) and (a) CeNa-Y(65).

The exclusive selectivity towards nitrogen in the NH3 oxidation with oxygen is striking, considering the fact that NO or N2O production is observed with many other catalysts [13]. A reaction patliway of ammonia oxidation over cerium zeolite remains to be elucidated. Tlie comparison of ammonia conversions in its oxidation and in the NO reduction illustrates a characteristic of tlie NO reduction with ammonia over cerium zeolite. At lower temperatures, NH3 appears to be activated more easily under NO reduction conditions tlian witli oxygen only. This picture of reductant activation differs fonn tliat assumed for hydrocarbons, where the activation of hydrocarbons is regarded as an important factor for NO reduction [3, 27]. fri a previous paper, we have proposed the intermediacy of NO2 in the NO reduction with ammonia at lower temperatures (e.g. 300 °C) [23]. Tliis intennediate NO2 can probably oxidize ammonia more efficiently than oxygen. 

Seiyama T, Arakawa T, Matsuda T, Yamazoe N, Takita Y (1975) Catalytic Reduction of Nitric-oxide with Ammonia over Transition-metal Ion-exchanged Y-zeolites. Chem Lett 4... 

Williamson WB, Lunsford JH (1976) Nitric oxide reduction with ammonia over copper(II) Y zeolites. J Phys Chem 80 (24) 2664-2671... 

Various alkyl-substituted pyridine derivatives are formed from the condensation of butyraldehyde with ammonia at high temperatures. For example, cocondensation of -butyraldehyde with acrolein [107-02-8] and ammonia at 400°C over a borosilicate zeolite gives 3-ethylpyridine [536-78-7] in 70% yield... 

Reaction of Chlorobenzene with Ammonia. Preliminary experiments showed that chlorobenzene did not show any reaction over zeolites in a helium stream and that CuY zeolites have good activity for aniline formation. Therefore, the reaction over CuY was studied in detail. 

Jones and Landis (12) assumed the formation of the ammine complexes and their participation in the reaction of toluene with ammonia to form benzonitrile over a variety of transition metal-exchanged X zeolites. 

Similarly, zeolites can catalyze the addition of ammonia to an olefinic double bond, as is exemplified by the BASF process for the production of tert-butylamine by reaction of isobutene with ammonia, in the vapor phase, over a rare earth exchanged ZSM-5 or Yzeolite (Fig. 2.20) [58, 59]. This process has an atom efficiency of 100% and replaced a conventional synthesis via a Ritter reaction, which employs HCN and sulfuric acid and generates formate as a coproduct. 

Auroux et al. (82, 91-93) observed a behavior similar to that seen for HY and HM zeolites above for the adsorption of ammonia over samples of HZSM-5 and HZSM-11 in the temperature range 416 to 673 K. The differential heat versus coverage curves had the same shape and decreased slightly with increasing temperature. Two exceptions in this behavior were noted. First, the differential heats for the samples at 673 K were unusually low. The initial heat for one sample of HZSM-5 at 673 K was lower than 100 kJ moP, whereas it was near 150 kJ mol at 523 K. The adsorption process seemed to be almost completely reversible at this temperature and could not be used to characterize the strong acidity of the solids. 

Zeolites have also known as efficient catalysts for a wide variety of acid-promoted cyclization reactions. Most of them involves the formation of N-heterocycles through the intramolecular amination reaction pathway [48-50]. See examples are shown in Figure 11.13. Pyridines are also being produced by the reaction of ammonia over solid support acid catalyst with various aldehydes [50]. 

The effect of various organic additives on the catalj ic performance of zeolites and Al-containing MCM-41 in the liquid phase Beckmann rearrangement of cyclohexanone oxime 5 was investigated at 130 °C. Over USY zeolite with a large amount of EFAL, the lactam yield was improved by adding ethanol, dimethyl sulfoxide, ammonia, diethylamine or pyridine to the... 

Xu L, McCabe RW, Hammerle RH (2002) NOx self-inhibition in selective catalytic reduction with urea (ammonia) over a Cu-zeolite catalyst in diesel exhaust. Applied Catalysis B Environmental 39 51-63... 

Wallin M, Karlsson C-J, Skoglundh M, Palmqvist A (2003) Selective catalytic reduction of NOx with NH3 over zeolite H-ZSM-5 influence of transient ammonia supply. J Catal 218 (2) 354-364... 

The introduction of monovalent and bivalent transition metal cations into zeolites is also possible and introduces in zeolites sites with redox activity. Several of these systems have wide application in catalysis. In particular, Co-zeolites, such as Co-MFI and Co-FER, have been deeply investigated for their activity in the CH4-SCR reaction [246]. In this case the adsorption of bases such as nitriles and ammonia, followed by IR and by TPD technique, show that they act as medium-strong Lewis acid sites. The current opinion is that these sites are catalytically active for the DeNO c reaction just when they are isolated in the zeolite cavities. A recent investigation provided evidence for the deposition of part of Co ions also at the external surface of the zeolite upon cation exchanging [85] and to their likely nonnegligible catalytic activity [247]. The deposition of Co species at the external cavities can be a reason for only apparent over-exchanging (i.e., production of zeolites with Co +/AP+ atomic ratios >0.5). 

The ODH of propane over titanium and vanadium containing zeolites and nonzeolitic catalysts revealed that Ti-silicalite was the most active. The addition of water caused an increase in selectivity, probably due to a competitive adsorption on the active sites. The reaction is proposed to occur on the outer surface of the Ti-silicalite crystallites on Lewis acid sites, and a sulfation of the catalyst, which increases the acidity of these sites, results in a further increase of the catalytic activity. The maximum conversion obtained was 17% with a propene selectivity of up to 74% [65]. Comparison of propane oxidation and ammoxidation over Co-zeolites shows an increase in conversion and propene selectivity during ammoxidation. For a conversion of 14%, 40% propene selectivity was obtained with ammonia, whereas, at 10% conversion the propene selectivity was only 12% with oxygen. The increase in activity and selectivity can be due to the formation of basic sites via ammonia adsorption [38]. 

Fig. 9.5 Differential heats of ammonia adsorption over HY zeolites with various A1 content as a...

NO -laden fumes are preheated by effluent from the catalyst vessel in the feed/effluent heat exchanger and then heated by a gas- or oil-fired heater to over 600° F. A controlled quantity of ammonia is injected into the gas stream before it is passed through a metal oxide, zeolite, or promoted zeolite catalyst bed. The NO is reduced to nitrogen and water in the presence or ammonia in accordance with the following exothermic reactions ... 

Rather than selective non-catalytic reduction, the reduction can be carried out over a catalyst (e.g. zeolite) at 150 to 450 C. This is known as selective catalytic reduction. Figure 25.31 shows a typical selective catalytic reduction arrangement10. Either anhydrous or aqueous ammonia can be used. This is mixed with air and injected into the flue gas stream upstream of the catalyst. Removal efficiency of up to 95% is possible. Again, slippage of excess ammonia needs to be controlled. 

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