NO Reduction Process

The Inventa-NO process is similar to the BASF process in that the first source of by-product ammonium sulfate is eliminated. Like the BASF process the Inventa process prepares hydroxylamine sulfate by the reduction of nitric oxide with hydrogen over a noble metal catalyst suspended in sulfuric acid. The differences between the BASF and Inventa processes are  

Inventa uses plastic materials for mechanical parts of the plant, and 

Inventa uses a palladium (rather than platinum) catalyst. 

In the process the starting materials must be very pure, and an involved catalyst recovery step is necessary46 266. 

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Lesage et al. also investigated the NO reduction process after storage on a classical Ba-based catalyst, using a IR + MS operando set-up [132], The alternate exposure to... 

It is natural to presuppose that the reduction of nitro compounds should lead to the nitroso compounds, at least as an intermediate stage. Until quite recently, no reductive processes for the formation of nitrosoalkanes were known [3], More recently, some indirect evidence is said to show that, on electrolytic reduction of tertiary aliphatic nitro compounds, the final t-alkyl-hydroxylamines are produced by the intermediate formation of nitroso compounds which were not isolated [99]. 

The PPR and LFR are also applied in a more recently developed dedicated process for NOx removal from off-gases. The Shell low-temperature NO reduction process is based on the reaction of nitrogen oxides with ammonia (reactions iv and v), catalyzed by a highly active and selective catalyst, consisting of vanadium and titania on a silica carrier [18]. The high activity of this catalyst allows the reaction of NO with ammonia (known as selective catalytic reduction) to be carried out not only at the usual temperatures around 300°C, but at substantially lower temperatures down to 130°C. The catalyst is commercially manufactured and applied in the form of spheres (S-995) or as granules (S-095) [19]. 

The first application of the LFR in the Shell low-temperature NO reduction process was to treat the flue gas of a gas-fired furnace in a California refinery. The unit has been designed to treat flue gas containing 5 ppm v. of sulfur dioxide at 190°C and a space velocity of 5000 NmV(m -hr). The unit was started up successfully in 1991 [21],... 

Bueno-Lopez, A., Caballero, J.A., and Garcia-Garcia, A. (2002). Analysis of the reaction conditions in the NO, reduction process by carbon with a view to achieve high NO conversions. Residence time considerations. Energy Fuels, 16, 1425-8. 

NO reduction using CO was also analysed in this context.156 In this reaction as well as for stoichiometric CO + NO + O2 mixtures,114-119,153 the main question arises as to which is the rate-limiting step, which in some cases is believed to be the NO dissociation153,157 while in other seems to be related to the N-coupling steps.156 Both elementary steps need a cluster of noble metal atoms and thus NO reduction processes are generally structure sensitive and size dependent.114-119,153,155,157 The rate of these two steps and the performance of the catalyst under reaction conditions seems closely connected with the availability of noble metal reduced (zero-valent) sites, the formation of which are strongly inhibited at the... 

As precious metals can catalyze NO oxidation, we decided to investigate the influence of NO2 formation in the global NO reduction process and to correlate N2O formation to the characteristics of the catalysts and of the reacting medium. 

Other variations of the caprolactam process produce hydroxylamine disulfonic acid which is hydrolyzed to hydroxylamine sulfate and an ammonium sulfate by-product. Additional ammonium sulfate is produced downstream in the oximation step by the reaction of ammonia with sulfuric acid. Ammonium sulfate is a low value by-product and there is an advantage to producing hydroxylamine sulfate directly in order to avoid the production of unwanted ammonium sulfate downstream. The oxygen-based NO reduction process provides this advantage and the processes that use it are characterized as low by-product production processes. 

The economics of the oxygen-based NO reduction process is difficult to compare because different caprolactam processes vary so widely. Nevertheless, an early study by Stanford Research Institute (SRI) found that the capital investment for the NO reduction process was about one-half that for the conventional Rashig process. The basis of this comparison included both the hydroxylamine unit as well as the oximation step. Operating costs were not reported, but the conclusion by SRI was that the NO Reduction process offered a decided advantage over the conventional Rashig process [31]. 

Carbon monoxide concentration at the point of chemical injection is also important (2). Carbon monoxide is a measure of the gas phase hydroxyl radical (OH ) concentration, an important intermediate in the NOx reduction chemistry. Increasing OH- radical concentration has the effect of shifting the temperature window to a lower temperature for either urea or ammonia based systems. In some cases this can be a disadvantage but in many cases this knowledge can be used for further optimization of the NO reduction process. 

The oxidation processes were each confirmed to involve one electron by coulometric experiments. No reductive processes were observed in the potential range studied (-2.5V). The diosmium species is approximately 200mV easier to oxidise than the corresponding Ru2 complex which makes it an easier sysytem to work with experimentally. 

The two methods are particularly useful when the region of interest is close to the surface of the sample, e.g., for ultrathin films on substrates and for surface interdiffusion processes. ARXPS is probably the best tool for the study of surface oxides, as no reduction processes due to ion sputtering occur. Grafted polymers have also been widely studied by ARXPS. 

Hurst, B. E., and White C. M., 1986, THERMAL DeNO, A Commercial Selective Non-Catalytic NO, Reduction Process for Waste-to-Energy Applications, paper presented at the ASME 12th Biennial National Waste Processing Conference, Denver, CO, June 2. 

In CH2CI2 solution, T shows relatively weak, low-energy absorption bands, and a strong fluorescence band (Amax = 344 nm, r = 9.5 ns, 4> = 0.53) typical of the naphthalene chromophoric group. In CH2CI2/CH3CN 9 1 (v/v) solution, T shows an irreversible oxidative process at +1.6 V, whereas no reduction process has been observed in the potential window of the solvent used (up to —2.0 V vi. SCE). 

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