Non-catalytic processes

Hi-Chloroff A thermal (non-catalytic) process for removing chlorine from chlorinated hydrocarbon wastes containing either low or high concentrations of chlorine. Developed by Kinetics Technology International. See also Chloroff. 

Semet-Solvay The Semet-Solvay Engineering Corporation, Syracuse, NY, was best known for its coke-oven technology, developed from the end of the 19th century. The eponymous process was a cyclic, non-catalytic process for making fuel gas from oil. 

A substoichiometric amount of air or oxygen is used. The reaction can be carried out in the presence or the absence of a catalyst. In the non-catalytic process, a mixture of oxygen and natural gas is preheated, mixed and ignited in a burner the reactor temperature must be high enough to reach complete CH4 conversion (typically 1200-1500 °C). Combustion products such as CO2 and H2O are also formed to a certain extent. 

Plasmas can be classified as either thermal or non-thermal. " Thermal plasma is a highly energetic state of matter, characterized by thermal equilibrium between the three components of the plasma electrons, ions, and neutrals. However, it requires high-energy input to achieve high temperatures. Researchers at MIT used a non-catalytic thermal plasma technology to produce H2 from liquid hydrocarbons. Non-catalytic processes are beyond the scope of this work, and will not be discussed. 

The gasification of hydrocarbons to produce hydrogen is a continuous, non-catalytic process (Figure 10-2) that involves partial oxidation of the hydrocarbon. Air or oxygen (with steam or carbon dioxide) is used as the oxidant at 1095— 1480°C (2000-2700°F). Any carbon produced (2-3 wt% of the feedstock) during the process is removed as a slurry in a carbon separator and pelleted for use either as a fuel or as raw material for carbon-based products. 

Compared with the common high-temperature conversion of natural gas and further carbon oxide conversion on a catalyst [131], the current process promotes process simplification the reaction is implemented at relatively low temperature (860-900 °C instead of 1400-1600 °C for existing non-catalytic processes of methane conversion) and an additional unit for catalytic conversion of carbon oxide is excluded (in NH3 production). 

Finally, new catalytic processes (e.g., multi-step treatments, new supports, and intermetallic systems) which avoid the metallic contamination (mainly by V, Ni, Fe, Ti and the alkalis) must be explored, just as non-catalytic processes should not be neglected in order to prevent shortage of catalyst from limiting progress. 

Flash hydrogenation is a short residence time (1 to 10 sec) gas-phase, non-catalytic process in which pulverized coal is rapidly heated (20,000-30,000° C/sec) in hydrogen to obtain liquid and gaseous hydrocarbons directly. Experiments were conducted in a 2 lb/hr, 1 ID x 8 ft long downflow tubular reactor in the range of 500° to 900°C and 500 to 3000 psi H2 pressure for North Dakota Lignite and New Mexico subbituminous coal (L). The ultimate analyses of these coals are given in... 

The rate constants for such outer-sphere reactions can therefore differ markedly from those corresponding to true weak-overlap pathways, even after correction for electrostatic double-layer effects. This can cause some difficulties with the operational definition of inner-sphere electrocatalysis considered above, whereby outer-sphere reactions are regarded as "non-catalytic processes. In addition, there is evidence that inner- rather than outer-sphere pathways can provide the normally preferred pathways at metal-aqueous interfaces for reactants containing hydrophobic functional groups [116]. 

In contrast to steam reforming, gasifieation is a non-catalytic process and is therefore very flexible in its feedstock requirements. At times of high natural gas priees this ability to process cheap feeds ean make gasifieation an attractive alternative. This eapability does, however, require additional eapital, since at the minimum, facilities for removing unwanted components in the feedstock, such as sulfur or ash, must be included. 

Table 5.2 Salomon s classification of catalytic and non-catalytic processes.

Another consideration is the increased cost or low availability of starting materials. Often non-catalytic processes require more expensive starting materials as the chemistry will not go with less active, cheaper materials. An example of this is the use of aryl-bromides in place of cheaper aryl-chlorides owing to reactivity constraints. Also, if the desired product is homo-chiral, then the chirality must be introduced through a chiral starting material. The supply of these starting materials are often limited by what is naturally available, i.e. the chiral pool, and this can affect cost and quantity availability. 

In catalytic reactions the range of activation energies is lowered by the fact that the initiating intermediate forms a weakly-bonded chemisorbed species whose attachment to the surface is rarely beyond 50 kcal/mol (200 kJ/mol). This limits the expected catalytic activation energies to between 20 and 50 kcal/mol (80 to 200 kJ/mol) and makes catalytic reactions less temperature sensitive than non-catalytic processes. Moreover, catalytic reactions can have such low activation energies that a pinch of catalyst may set off an explosion in an exothermic reaction, even if the reaction will not proceed at all in the absence of the catalyst. 

Oxidation of anthracene is interesting from the viewpoint of obtaining anthraquinone, a valuable product. The oxidation can actually be carried out by a non-catalytic method using any oxidant, but the non-catalytic process requires rigid conditions and is accompanied by formation of a number of side products, especially anthrone and bianthrone (Eq. 12-27). 

Among non-catalytic processes, a technology developed by Hydrocarbon Research is particularly widely used. The molar hydrogen/toluene ratio is around 4 1 the molar yield is around 97 to 99%, i.e., of the same order as with catalytic dealkylation. 

Soot formation in ATR can be eliminated by addition of a certain amount of steam to the feedstock and by special burner design. Steam can hardly be added to the non-catalytic processes without the risk of increased soot formation because of the resulting lower temperature. This means less flexibility for the composition of the syngas from POX units. 

The division between the non-catalytic microbial syntheses and the catalytic microbial transformation is perhaps not very sharp. The oxidation of ethanol to acetic acid in the manufacture of vinegar by the traditional microbial route uses a permanent culture of bacteria growing on wooden slats. The bacteria oxidize the ethanol in the wine as it flows over the slats, and, at the same time they draw sufficient nutrients from the wine to maintain a population which is both constant and healthy. Individual organisms divide and die, but the overall bacterial culture is unchanged, and is catalytic in its action. Here, in a real sense, the distinction between a catalytic and a non-catalytic process depends on the scale on which the process is described. 

Many processes of the chemical industry consist of extremely complex reaction schemes, often because the feedstock is a complicated mixture derived from natural resources, but in some cases even with a simple feed. Examples of non-catalytic processes will be dealt with here, of catalytic processes in Chapter 2. Important non-catalytic processes are thermal cracking (also called pyrolysis), polymerization, combustion, oxidation, and photochlorination. They proceed through radical steps. By way of example, the first two will be dealt with here. 

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