Distribution product

The product distribution of hydrocarbons formed during the Fischer-Tropsch process follows an Anderson-Schulz-Flory distribution (Spath and Dayton, 2003)  

W is the weight fraction of hydrocarbon molecules containing n carbon atoms 

In general, a is largely determined by the catalyst and the specific process conditions. 

It has been proposed that zeolites or other catalyst snbstrates with fixed sized pores can restrict the formation of hydrocarbons longer than some characteristic size (usually n 10). This would tend to drive the reaction to minimnm methane formation without producing the waxy prodncts. 

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However, before extrapolating the arguments from the gross patterns through the reactor for homogeneous reactions to solid-catalyzed reactions, it must be recognized that in catalytic reactions the fluid in the interior of catalyst pellets may diSer from the main body of fluid. The local inhomogeneities caused by lowered reactant concentration within the catalyst pellets result in a product distribution different from that which would otherwise be observed. 

Specifications for density, distillation curve and viscosity shown above are for products distributed in temperate climates. Other limits are required for arctic regions, particularly the Scandinavian countries. See Tables 5.13 and 5.14. 

The European specifications require a minimum cetane number of 49 for the temperate climatic zones and the French automotive manufacturers require at least 50 in their own specifications. The products distributed in France and Europe are usually in the 48-55 range. Nevertheless, in most Scandinavian countries, the cetane number is lower and can attain 45-46. This situation is taken into account in the specifications for the arctic zone (Table 5.14). In the United States and Canada, the cetane numbers for diesel fuels are most often less than 50. 

Fission product distribution Radioactive waste activity distribution... 

Figure C2.3.9. Product distribution of dissymmetrical ketone photolysis as influenced by cefyltrimethylammonium chloride (CTAC) micelles. The initial ketone, A(CO)B is photolysed to lose the carbonyl group and to produce tliree products, AA, AB and BB. These data are for benzyl (A) 4-methylbenzyl (B) ketone. Product AA is 1,2-diphenylethane, product BB is 1,2-ditolylethane and product AB is l-phenyl-2-tolyl-ethane. At low CTAC concentration, in the absence of micelles, a random distribution of products is obtained. In the presence of micelles, however, the AB product is heavily favoured. Adapted with pennission from 1571.

A more demanding dynamical study aimed to rationalize the product distribution in photochemical cycloaddition, looking at butadiene-butadiene [82]. A large number of products are possible, with two routes on the excited Si state leading back to channels on the ground state. The results are promising, as the MMVB dynamics find the major products found experimentally. They also... 

Let us illustrate this with the example of the bromination of monosubstituted benzene derivatives. Observations on the product distributions and relative reaction rates compared with unsubstituted benzene led chemists to conceive the notion of inductive and resonance effects that made it possible to explain" the experimental observations. On an even more quantitative basis, linear free energy relationships of the form of the Hammett equation allowed the estimation of relative rates. It has to be emphasized that inductive and resonance effects were conceived, not from theoretical calculations, but as constructs to order observations. The explanation" is built on analogy, not on any theoretical method. 

Reaction Relative rate hffks Product distribution ... 

TABLE 1-56. TYPICAL PRODUCT DISTRIBUTION OF THE DECOMPOSITION AT 100°C OF BENZOYL PEROXIDE (0.02 MOLE) IN THIAZOLE (I MOLE) (397)... 

TABLE 1-58. PRODUCT DISTRIBUTION OF THE REACTION AT VARIOUS TEMPERATURES OF 2-METHYLTHlAZOLE (157) WITH BUTYL-LITHIUM FOLLOWED BY QUENCHING WITH DjS04 (441). 

The more stable (E) alkenyl radical m which the alkyl groups R and R are trans to each other is formed faster than its Z stereoisomer Steps 3 and 4 which follow are fast and the product distribution is determined by the E-Z ratio of radicals produced m step 2... 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives The reactivity of a particular position in o bromotoluene for example is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene On the basis of the partial rate factor data given here for Fnedel-Crafts acylation predict the major product of the reaction of o bromotoluene with acetyl chlonde and aluminum chloride... 

Sasol produces synthetic fuels and chemicals from coal-derived synthesis gas. Two significant variations of this technology have been commercialized, and new process variations are continually under development. Sasol One used both the fixed-bed (Arge) process, operated at about 240°C, as weU as a circulating fluidized-bed (Synthol) system operating at 340°C. Each ET reactor type has a characteristic product distribution that includes coproducts isolated for use in the chemical industry. Paraffin wax is one of the principal coproducts of the low temperature Arge process. Alcohols, ketones, and lower paraffins are among the valuable coproducts obtained from the Synthol process. 

Table 2. Approximate Product Distribution from Sasol Two ...

Fig. 5. The effect of temperature on product distribution in VPO of butane with air.

Effect of Pressure. The effect of pressure in VPO has not been extensively studied but is informative. The NTC region and cool flame phenomena are associated with low pressures, usually not far from atmospheric. As pressure is increased, the production of olefins is suppressed and the NTC region disappears (96,97). The reaction rate also increases significantly and, therefore, essentially complete oxygen conversion can be attained at lower temperatures. The product distribution shifts toward oxygenated materials that retain the carbon skeleton of the parent hydrocarbon. 

Propane. The VPO of propane [74-98-6] is the classic case (66,89,131—137). The low temperature oxidation (beginning at ca 300°C) readily produces oxygenated products. A prominent NTC region is encountered on raising the temperature (see Fig. 4) and cool flames and oscillations are extensively reported as compHcated functions of composition, pressure, and temperature (see Fig. 6) (96,128,138—140). There can be a marked induction period. Product distributions for propane oxidation are given in Table 1. 

Catalysts and Promoters. The function of catalysts in LPO is not weU understood. Perhaps they are not really catalysts in the classical sense because they do not necessarily speed up the reaction (25). They do seem to be able to alter relative rates and thereby affect product distributions, and they can shorten induction periods. The basic function in shortening induction periods appears to be the decomposition of peroxides to generate radicals (eq. 33). 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

These variations permit the separation of other components, if desired. Additional data on uranium, plutonium, and nitric acid distribution coefficients as a function of TBP concentration, solvent saturation, and salting strength are available (24,25). Algorithms have also been developed for the prediction of fission product distributions in the PUREX process (23). 

Amines or ammonia replace activated halogens on the ting, but competing pyridyne [7129-66-0] (46) formation is observed for attack at 3- and 4-halo substituents, eg, in 3-bromopyridine [626-55-1] (39). The most acidic hydrogen in 3-halopyridines (except 3-fluoropyridine) has been shown to be the one in the 4-position. Hence, the 3,4-pyridyne is usually postulated to be an intermediate instead of a 2,3-pyridyne. Product distribution (40% (33) and 20% (34)) tends to support the 3,4-pyridyne also. 

The product distribution appears to depend on the radiation used for quinone excitation, the structure of the quinone, and the quinone—alkene ratio. In the example cited, l,4-ben2oquinone gives only the spirooxetane, whereas chlorarul gives both products in amounts related to the ratio of starting materials... 

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