Synol process

For low space velocities of synthesis gas, the products from nitrided catalysts in fixed-bed reactors are somewhat similar to those of the Synol process employing high space velocities and low temperatures. Possibly the yields of alcohols and other oxygenated molecules obtained from nitrided catalysts under the conditions employed in the Synol process would be even higher than those obtained from nitrides at low space velocities. 

Special references on the methanol and higher alcohol syntheses are Ellis (27), Hirst (45), Hastens (54), and Giesen and Hanisch (38). The Oxyl process is described by Roelen and Beery (96). The Synol process literature is covered in references (4, 38, 110, 118). Oxo synthesis literature is reported on in some detail by Holm (46), Schuster (100), and Orchin and Schroeder (83). 

Under the title Synol Process Wenzel (46) published experiments in the field of the medium-pressure synthesis with iron catalysts. The following conditions were mentioned as promoting the formation of alcohol (a) low synthesis temperature (preferably below 200°C.), (b) high pressure (e.g., 20 atm.), (c) operation in several stages, preferably with recycling of gas, minimum conversion in each stage, and removal of carbon dioxide between the stages. 

The synol process is of interest in a discussion of the Fischer-Tropsch reaction for the following reasons ... 

The same catalyst, when used at a higher temperature as in the hot-gas recycle process, yields chiefly hydrocarbons, with only 5-10% alcohols, whereas in the synol process a very high recycle ratio of about 100 w ith drying of the gas on each cycle yields as much as 70% conversion to alcohols. The total conversion is over 90% to alcohols plus hydrocarbons, with only a very small amount of carbon dioxide produced. It is likely that the formation of the normal straight-chain alcohols, which constitute the bulk of the synol alcohol product, precedes the formation of olefins on this iron catalyst at 20 atmospheres in the temperature range 190-325 C. 

Carbon deposition apparently is proceeding at an appreciable velocity even at 190-225° C. under the conditions of the synol process. The formation of carbon at 300-325 C. in the hot-gas recycle or the fluidized iron catalyst processes, therefore, is not peculiar to the elevated temperatures used in those processes, although its rate is higher at the higher temperatures. 

It is possible that a reaction similar to the 0X0 reaction occurs on the surface of catalysts during the synthesis of hydrocarbons and alcohols by the Fischer-Tropsch and the synol processes, and accounts for the small (about 10%) fraction of branched hydrocarbons and isoalcohols produced. In this coimection it is of interest to note that as Pichler (37) indicated, the optimum operating pressures for nickel, cobalt, iron, and ruthenium Fischer-Tropsch catalysts increase in the order mentioned, and the difficulty of metal carbonyl formation also increases in this order. 

Fischer-Tropsch A process for converting synthesis gas (a mixture of carbon monoxide and hydrogen) to liquid fuels. Modified versions were known as the Synol and Synthol processes. The process is operated under pressure at 200 to 350°C, over a catalyst. Several different catalyst systems have been used at different periods, notably iron-zinc oxide, nickel-thoria on kieselgtihr, cobalt-thoria on kieselgiihr, and cemented iron oxide. The main products are C5-Cn aliphatic hydrocarbons the aromatics content can be varied by varying the process conditions. The basic reaction was discovered in 1923 by F. Fischer and... 

Synol A version of the Fischer-Tropsch process developed in Germany during World War II. It used a different catalyst and produced a larger fraction of alcohols and olefins. 

Synthol A version of the Fischer-Tropsch process, for making liquid fuels and organic chemicals from syngas. Developed by Pullman Kellogg between 1940 and 1960. First operated at the SASOL plant in South Africa in 1955. The name was used also for the product from the original Fischer-Tropsch process, developed in the 1920s. See also Synol. Hydrocarbon Process., 1963, 42(11), 225. 

General Introduction. Three processes, the Oxo, Synol, and Isosynthesis, are related to the Fischer-Tropsch process in that hydrocarbons or oxygenated chemicals are produced from mixtures of hydrogen and carbon monoxide. The principal catalysts, operating conditions, and products pf these syntheses and similar data on the Fischer-Tropsch process and some of its variations are compared in Table 11-8. 

The Synol and isosynthesis processes, as well as the Oxyl and iron nitride variations of the Fischer-Tropsch synthesis, were developed to produce special products from synthesis gas. All but the isosynthesis are designed to produce high yields of oxygenated materials. The isosynthesis yields highly branched aliphatic hydrocarbons and aromatics. While none of these processes has been used commercially, they could be of interest at some future time. 

---