Synthesis-gas production

3 Synthesis gas production. Alqahtany et al.92 have studied synthesis gas production from methane over an iron/iron oxide electrode-catalyst. Although the study was essentially devoted to fuel cell operation, for purposes of comparison some potentiometric work was performed at 950°C. It was found that under reaction conditions Fe, FeO or Fe304 could be the stable catalyst phase. Hysteresis in the rates of methane conversion were observed with much greater rates over a pre-reduced surface than over a pre-oxidised surface possibly due to the formation of an oxide. 

In this section the use of amperometric techniques for the in-situ study of catalysts using solid state electrochemical cells is discussed. This requires that the potential of the cell is disturbed from its equilibrium value and a current passed. However, there is evidence that for a number of solid electrolyte cell systems the change in electrode potential results in a change in the electrode-catalyst work function. This effect is known as the non-faradaic electrochemical modification of catalytic activity (NEMCA). In a similar way it appears that the electrode potential can be used as a monitor of the catalyst work function. Much of the work on the closed-circuit behaviour of solid electrolyte electrochemical cells has been concerned with modifying the behaviour of the catalyst (reference S is an excellent review of this area). However, it is not the intention of this review to cover catalyst modification, rather the intention is to address information derived from closed-circuit work relevant to an unmodified catalyst surface. 

80% of the hydrogen produced is produced on the basis of natural gas/crude oil 

The production of one ton of ammonia requires a mixture of 2400 m of highly purified hydrogen and 800 m- of highly purified nitrogen (at 0°C and 1000 mbar). It is produced using different processes depending upon the raw materials utilized. 

Nitrogen is taken from air or from the nitrogen content of natural gas. This is carried out by low temperature fractionation of air, which is preferred when pure oxygen is required as an oxidizing agent in the production of synthesis gas. Alternatively air is employed directly in the production of synthesis gas and the oxygen is removed by the to be oxidized reaction partners. 

Hydrogen is produced from hydrocarbons or coal and water  

The choice of process depends upon the availability of raw materials. Hydrogen for ammonia synthesis is currently rarely produced by water electrolysis, except in countries 

Usually only the carbon-containing materials and hydrogen from other sources are regarded as raw materials in the narrow sense because of the abundance of air, which 

Certain raw materials for synthesis gas production that were once of primary importance currently are used only under special economic and geographical circumstances (e.g., China, where 66% of production is based on coal). These include solid 

Relative specific energy requirement (based on lower heating values) 1.0 1.1 1.3 1.7 

The capital cost and the specific energy requirement (i.e., feed and fuel, and so the manufacturing cost) largely depend on the raw material employed [411], [412], Table 22 shows the relative capital cost and the relative energy requirement for a plant with a capacity of 1800 t/d ammonia. For the natural gas based plant the current best value of 28 GJ/t NH3 is used. 

Light hydrocarbons ranging from natural gas (methane) to naphtha (max. Cn) undergo reaction with steam over a catalyst according to Equation (35) which is usually 

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Secunda discharges no process water effluents. AU. water streams produced are cleaned and reused in the plant. The methane and light hydrocarbons in the product are reformed with steam to generate synthesis gas for recycle (14). Even at this large scale, the cost of producing fuels and chemicals by the Fischer-Tropsch process is dominated by the cost of synthesis gas production. Sasol has estimated that gas production accounts for 58% of total production costs (39). 

The technology of urea production is highly advanced. The raw materials requited ate ammonia and carbon dioxide. Invariably, urea plants ate located adjacent to ammonia production faciUties which conveniently furnish not only the ammonia but also the carbon dioxide, because carbon dioxide is a by-product of synthesis gas production and purification. The ammonia and carbon dioxide ate fed to a high pressure (up to 30 MPa (300 atm)) reactor at temperatures of about 200°C where ammonium carbamate [111-78-0] CH N202, urea, and water ate formed. 

R. WintreU, The K-T Process Koppers Commercially Proven Coal and Multi-Fuel Gasifier for Synthesis Gas Production in the Chemical andFertilkyer Industries, American Institute of Chemical Engineers, New York, Aug. 1974. 

In principle biomass is a useful fuel for fuel cells many of the technologies discussed above for using biomass as a fuel produce either methane or hydrogen directly and as highlighted below synthesis gas production from biomass for conversion to methanol is an attractive option. Cellulose-based material may be converted to a mixture of hydrogen (70% hydrogen content recovered), CO2 and methane by high-temperature treatment with a nickel catalyst. 

Aasberg-Petersen, K., Synthesis gas production for FT synthesis, in Fischer-Tropsch Technology, Chap. 4, Steynberg, A. and Dry, M., Eds., Elsevier, Amsterdam, 2004. 

In the 1930s, Standard Oil of New Jersey (7) was the first company to employ on a commercial scale the indirect conversion of methane, the main component of natural gas, via steam reforming to give synthesis gas, which is a mixture of H2 and CO, with the H2/CO ratio depending on the reactant composition. C02 is also formed in synthesis gas production, and sulfur compounds are present as impurities. Synthesis gas can be used as a feedstock for numerous chemicals and fuels and as a source of pure hydrogen or carbon monoxide. 

Some examples of new problems encountered in synthesis gas production are the following. 

ATR is a stand-alone process which combines POX and SR in a single reactor. The ATR process was first developed in the late 1950s by Topsoe, mainly for industrial synthesis gas production in ammonia and methanol plants [27]. 

The direct oxidation of CH is an alternate route for synthesis gas production ... 

Application of fluidized catalyst techniques to the Fischer-Tropsch synthesis (30) has yielded a process that produces chiefly (about 70%) motor gasoline, with minor amounts (about 30%) of fuel oil and oxygenated compounds. The fluidized iron catalyst process is outstanding because of its very high space-time yield and because it may be competitive with existing petroleum production and refining processes, if natural gas at 10 cents or less per 1000 cubic feet is available as the raw material for synthesis gas production. 

Table V shows the salient features of several Fischer-Tropsch processes. Two of these—the powdered catalyst-oil slurry and the granular catalyst-hot gas recycle—have not been developed to a satisfactory level of operability. They are included to indicate the progress that has been made in process development. Such progress has been quite marked in increase of space-time yield (kilograms of C3+ per cubic meter of reaction space per hour) and concomitant simplification of reactor design. The increase in specific yield (grams of C3+ per cubic meter of inert-free synthesis gas) has been less striking, as only one operable process—the granular catalyst-internally cooled (by oil circulation) process—has exceeded the best specific yield of the Ruhrchemie cobalt catalyst, end-gas recycle process. The importance of a high specific yield when coal is used as raw material for synthesis-gas production is shown by the estimate that 60 to 70% of the total cost of the product is the cost of purified synthesis gas.

According to another important and promising technology, hydrocarbons are produced from methanol, which, in turn, is synthesized from synthesis gas. Called the methanol-to-gasoline process, it was practiced on a commercial scale and its practical feasibility was demonstrated. Alternative routes to eliminate the costly step of synthesis gas production may use direct methane conversion through intermediate monosubstituted methane derivatives. An economic evaluation of different methane transformation processes can be found in a 1993 review.1... 

Synthesis-Gas-Production Processes. These processes were improved and developed as a result of changes in feedstock availability and economics. Before World War II, most NH3 plants obtained H2 by reacting coal or coke with steam in the water-gas process, A small number of plants... 

If the rich gas from the CRG reactor is passed over another bed of high-nickel catalyst at a lower temperature, the equilibrium of the five components is reestablished. Carbon oxides react with hydrogen to form methane and the calorific value of the gas is increased. It should be noted that this methanation step differs from that encountered in ammonia synthesis gas production because of the high steam content the temperature rise is reduced and there is no possibility of temperature runaway as the... 

In-Situ Study of Carbon Deposition during C02 Reforming of Methane for Synthesis Gas Production, Using the Tapered Element Oscillation Microbalance... 

It is fair to state that by and large the most important application of structured reactors is in environmental catalysis. The major applications are in automotive emission reduction. For diesel exhaust gases a complication is that it is overall oxidizing and contains soot. The three-way catalyst does not work under the conditions of the diesel exhaust gas. The cleaning of exhaust gas from stationary sources is also done in structured catalytic reactors. Important areas are reduction of NOv from power plants and the oxidation of volatile organic compounds (VOCs). Structured reactors also suggest themselves in synthesis gas production, for instance, in catalytic partial oxidation (CPO) of methane. 

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