Conversion reaction process

Figure4.4 Schematic ofthe conversion reaction process showing both the formation of Co nanoparticles and of the gel-like polymeric layer, as well as their evolution upon subsequent charges/discharges [110],...

Carbon monoxide and excess steam are normally passed over a cobalt catalyst at about 250-300 C resulting in greater than 99% conversion of CO to COj. This conversion reaction is widely used in oil or solid fuel gasification processes for the production of town gas or substitute natural gas. ... 

AMMONIA Raw material Process description Feedstock conversion reaction V012... 

The methanation reaction is currently used to remove the last traces (<1%) of carbon monoxide and carbon dioxide from hydrogen to prevent poisoning of catalysts employed for subsequent hydrogenation reactions. Processes for conversion of synthesis gas containing large quantities of carbon monoxide (up to 25%) into synthetic natural gas have been investigated to serve plants based on coal-suppHed synthesis gas. 

From these simple intermediates, many important chemicals and polymers are derived through different conversion reactions. The ohjec-tive of this hook is not merely to present the reactions involved in such conversions, hut also to relate them to the different process variables and to the type of catalysts used to get a desired product. When plausi-hle, discussions pertinent to mechanisms of important reactions are included. The hook, however, is an attempt to offer a simplified treatise for diversified subjects dealing with chemistry, process technology, polymers, and catalysis. 

The reactions that accomplished the conversion of intermediate 16 into intermediate 23 have taken place very smoothly. It is worth acknowledging that the //-hydroxy lactam moiety did not, at any stage, participate in any undesirable side reaction processes. The stability of the //-hydroxy lactam substructure in the presence of basic reagents is particularly noteworthy since a destructive retro-aldol cleavage reaction could have conceivably occurred on several occasions. The stability of this potentially labile moiety permits all of the desired transformations leading from 16 to 23 to be conducted without prior protection of the C-8 hydroxyl group. 

The concept of reaction diffusion (also called residual termination) has been incorporated into a number of treatments.7 7 Reaction diffusion will occur in all conversion regimes. However at low and intermediate conversions the process is not of great significance as a diffusion mechanism. At high conversion long chains are essentially immobile and reaction diffusion becomes the dominant diffusion mechanism (when i and j are both "large" >100). The termination rate constant is determined by the value of kp and the monomer concentration. In these circumstances, the rate constant for termination k - should be independent of the chain lengths i and j and should obey an expression of the form 75... 

In an ideal DKR, where the substrate stays racemic throughout the reaction process, the optical purity depends only on the enantiomeric ratio (E) (ee =(E— 1)/ (E +1)), and is independent of the extent of conversion. The enantiomeric excess of the product formed under racemizing conditions is equal to the initial enantiomeric... 

Buser H-R, MD Muller (1997) Conversion reactions of various phenoxyaUcanoic acid herbicides in soil 2 elucidation of the enantiomerization process of chiral phenoxy acids from incubation in a DjO/soil system. Environ Sci Technol 31 1960-1967. 

OS 72] [R 6] [P 53] A 3 X 7 library was made in a sequential and automated way with conversions of 35% (lowest) and 99% (quantitative for 16 reactions) [20]. The results obtained were compared for consistency with single-reaction processing on the same chip. 

Processes in which a flow stream is returned (recycled) to an earlier stage in the processing sequence are frequently used. If the conversion of a valuable reagent in a reaction process is appreciably less than 100 per cent, the unreacted material is usually separated and recycled. The return of reflux to the top of a distillation column is an example of a recycle process in which there is no reaction. 

The basic objective of the conversion coating process is to provide a corrosion-resistant film that is integrally bonded chemically and physically to the base metal and that provides a smooth and chemically inert surface for subsequent application of a variety of paint films. The conversion coating processes effectively render the surface of the basis material electrically neutral and immune to galvanic corrosion. Conversion coating on basis material coils does not involve the use of applied electric current to coat the basis material. The coating mechanisms are chemical reactions that occur between solution and basis material.1-4... 

Hougen- Watson Models for Cases where Adsorption and Desorption Processes are the Rate Limiting Steps. When surface reaction processes are very rapid, the overall conversion rate may be limited by the rate at which adsorption of reactants or desorption of products takes place. Usually only one of the many species in a reaction mixture will not be in adsorptive equilibrium. This generalization will be taken as a basis for developing the expressions for overall conversion rates that apply when adsorption or desorption processes are rate limiting. In this treatment we will assume that chemical reaction equilibrium exists between various adsorbed species on the catalyst surface, even though reaction equilibrium will not prevail in the fluid phase. 

The phase composition of glycine crystal forms during the drying step of a wet granulation process has been studied, and a model developed for the phase conversion reactions [88], X-ray powder diffraction was used for qualitative analysis, and near-infrared spectroscopy for quantitative analysis. It was shown that when glycine was wet granulated with microcrystalline cellulose, the more rapidly the granulation... 

The solid sorbent material must also be heated and cooled for regeneration and absorption cycles. Because the solid C02 sorbents operate at higher temperatures than the liquid absorption systems, they provide opportunities for simultaneous WGS reaction with C02 removal improving the CO conversion in sorbent-enhanced reaction process (SERP). A number of studies have been reported on the SERP concept and are currently underway as discussed in later sections. 

A batch reaction process has a downtime of 0.5 hrs/batch. The specific rate is 0.2 liters/gmol-hr and the starting concentration is 8 gmol/liter. Find the fractional conversion at which a maximum daily production is obtained. 

The reaction is reversible and therefore the products should be removed from the reaction zone to improve conversion. The process was catalyzed by a commercially available poly(styrene-divinyl benzene) support, which played the dual role of catalyst and selective sorbent. The affinity of this resin was the highest for water, followed by ethanol, acetic acid, and finally ethyl acetate. The mathematical analysis was based on an equilibrium dispersive model where mass transfer resistances were neglected. Although many experiments were performed at different fed compositions, we will focus here on the one exhibiting the most complex behavior see Fig. 5. 

Practical conversion processes can only approach the theoretical efficiencies shown in Table 3. The coal conversion reactions do not proceed to completion at ambient temperatures within practical time limitations. As a result, a portion of the coal feedstock must be burned to supply heat so that the reactions can be carried out at elevated temperatures and pressure where the rates of conversion are rapid. In practical systems, this additional heat can only be partially recovered. Consequently, practical conversion processes have actual heat recovery efficiencies of about 60-70% for production of high H/C ratio products. Production of secondary fuels having somewhat lower H/C ratio, i.e. about 2.0, permits attainment of heat recovery efficiencies of 70 to 80j. 

Catalyst a chemical agent which, when added to a reaction (process), will enhance the conversion of a feedstock without being consumed in the process. 

The preheating of solid fuel and the ash cooling are not included in the thermochemical conversion process. The basic criteria for these four thermochemical conversion reactions are that the solid-fuel convertibles (or moisture, char, volatiles) are converted from the solid phase into the interstitial gas phase and finally to the offgases (Figure 16 and Figure 19). The part of the solid-fuel convertibles that is converted into the interstitial gas phase is defined as the conversion gas [3]. The conversion gas is associated with two important physical properties, namely the empirical stoichiometry [CxHyOz] and the mass flux [kg/m s]. 

The dual nature of enamine-iminium pairs allows unique possibilities for domino processes. Reactions of enamines with electrophiles afford electrophilic iminium ions that are ready to react with another (internal or external) nucleophile. Conversely, reactions of unsaturated imininm ions with nucleophiles afford enamines. Examples of intramolecular enamtne-catalyzed domino processes are depicted in Scheme 35. In all of these reactions, both enamine and iminium mediated steps can be distinguished. 

The authors noted about the influence of electronic nature of 2-aminoazoles on the reaction efficiency. By the treatment of electron-deficient aminoazoles such as 2-aminothiadiazoles or 2-aminooxazoles, the low conversion of the reaction was observed. As an explanation of this outcome they supposed that the reactions in these cases occurred very slowly and the competing reaction processes did not take place. As a result the formation of side-products is favored, one of which might be the compound 94 (Scheme 41). 

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