Recycles conversion limited

Methanol Synthesis. AH commercial methanol processes employ a synthesis loop, and Figure 6 shows a typical example as part of the overall process flow sheet. This configuration overcomes equiUbtium conversion limitations at typical catalyst operating conditions as shown in Figure 1. A recycle system that gives high overall conversions is feasible because product methanol and water can be removed from the loop by condensation. 

Continuous solution Free radical (backmixed reactor) Styrene monomer Recycled solvent W or W/O initiator Good Temperature Control Good for copolymers Good clarity and color Uniform product Limited in final conversion Limited in product range Pumping difficulties High capital Low-cost process for high-volume GP... 

Where possible, introducing extraneous materials into the process should be avoided, and a material already present in the process should be used. Figure 4.6h illustrates use of the product as the heat carrier. This simplifies the recycle structure of the flowsheet and removes the need for one of the separators (see Fig. 4.66). Use of the product as a heat carrier is obviously restricted to situations where the product does not undergo secondary reactions to unwanted byproducts. Note that the unconverted feed which is recycled also acts as a heat carrier itself. Thus, rather than relying on recycled product to limit the temperature rise (or fall), simply opt for a low conversion, a high recycle of feed, and a resulting small temperature change. 

Olefin—Paraffin Separation. The catalytic dehydrogenation of / -paraffins offers a route to the commercial production of linear olefins. Because of limitations imposed by equiUbrium and side reactions, conversion is incomplete. Therefore, to obtain a concentrated olefin product, the olefins must be separated from the reactor effluent (81—85), and the unreacted / -paraffins must be recycled to the catalytic reactor for further conversion. 

C with low conversion (10—15%) to limit dichloroalkane and trichloroalkane formation. Unreacted paraffin is recycled after distillation and the predominant monochloroalkane is dehydrochlorinated at 300°C over a catalyst such as nickel acetate [373-02-4]. The product is a linear, random, primarily internal olefin. 

Ammonia Synthesis and Recovery. The purified synthesis gas consists of hydrogen and nitrogen in about 3 1 molar ratio, having residual inerts (CH Ar, sometimes He). The fresh make-up gas is mixed with the loop recycle and compressed to synthesis pressures. AH modern synthesis loops recycle the unreacted gases because of equiUbrium limitations to attain high overall conversions. The loop configurations differ in terms of the pressure used and the point at which ammonia is recovered. 

The hydration reaction is carried out in a reactor at approximately 300°C and 70 atmospheres. The reaction is favored at relatively lower temperatures and higher pressures. Phosphoric acid on diatomaceous earth is the catalyst. To avoid catalyst losses, a water/ethylene mole ratio less than one is used. Conversion of ethylene is limited to 4-5% under these conditions, and unreacted ethylene is recycled. A high selectivity to ethanol is obtained (95-97%). 

All of the methods of recovery and recycle have been limited by market forces. However, the importance of environmental issues in the selection of the HBr conversion or recycle processes has only more recently been recognized (refs. 5, 6). For example, proposed restrictions (refs. 7, 8) on methyl bromide manufacture could eliminate this high-volume, economical route to HBr conversion. 

It is the formation of this material which makes the reaction have a low atom economy and, owing to the cost of disposal (usually by conversion to calcium phosphate and disposal as hazardous waste), has limited its commercial usefulness to high value products. Several methods have been developed to recycle (Ph)3PO into (Ph)3P but these have proved more complex than might be expected. Typically the oxide is converted to the chloride which is reduced by heating with aluminium. Overall this recovery is expensive and also produces significant amounts of waste. 

Microreactors Low conversion, catalytic reactions Simple design, transport rates can be increased by external recycling Limited ease of variation of parameters, maldistribution of flow can be prohibitive... 

The HC1 from the pyrolysis step is recycled to the oxyhydrochlorination step. The flow of ethylene to the chlorination and oxyhydrochlorination reactors is adjusted so that the production of HC1 is in balance with the requirement. The conversion in the pyrolysis reactor is limited to 55 per cent, and the unreacted dichloroethane (DCE) separated and recycled. 

In the production of ammonia from hydrogen and nitrogen the conversion, based on either raw material, is limited to 15 per cent. The ammonia produced is condensed from the reactor (converter) product stream and the unreacted material recycled. If the feed contains 0.2 per cent argon (from the nitrogen separation process), calculate the purge rate required to hold the argon in the recycle stream below 5.0 per cent. Percentages are by volume. 

The classic work of Storch and co-workers showed that essentially all coals below 89% C f can be converted in high yields to acetone soluble materials on extended reaction (12). We have investigated the behavior of coals of varying rank toward short contact time liquefaction. In one series of experiments, coals were admixed with about 5 volumes of a solvent of limited H-donor content (8.5% Tetralin) and heated to 425°C for either 3 or 90 minutes. The solvent also contained 18% p-cresol, 2% y-picolene, and 71.5% 2-methylnaphthalene and represented a synthetic SRC recycle solvent. The conversions of a variety of coals with this... 

Conversion per pass is limited by reaction equilibrium after cooling to condense the product methanol, the unreacted gas is recycled to the reactor. Developed by Imperial Chemical Industries in the late 1960s, since when it has been the leading process. As of 1991, 41 plants had been commissioned and a further 7 were under contract or construction. 

Both pyrolysis and gasification convert carbonaceous materials into energy-rich fuels by heating the feedstock under controlled conditions. Whereas incineration fully converts the input material into energy and ash, these processes deliberately limit the conversion so that combustion does not take place directly. Instead, they convert the material into valuable intermediates that can be further processed for materials recycling or energy recovery. 

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