Synthesis gas hydrogen from

Advanced water-gas shift reactors using sulphur-tolerant catalysts to produce more hydrogen from synthesis gas at lower cost. 

Also, there is approximately another 19 million metric tons of relative high-purity carbon dioxide from refineries and other chemical plants in the United States that use hydrogen from synthesis gas and discharge carbon dioxide to the atmosphere. 

Economic Analysis of the Biological Water Gas Shift Process for the Production of Hydrogen from Synthesis Gas, October 2001. 

Fischer-Tropsch Process. The Hterature on the hydrogenation of carbon monoxide dates back to 1902 when the synthesis of methane from synthesis gas over a nickel catalyst was reported (17). In 1923, F. Fischer and H. Tropsch reported the formation of a mixture of organic compounds they called synthol by reaction of synthesis gas over alkalized iron turnings at 10—15 MPa (99—150 atm) and 400—450°C (18). This mixture contained mostly oxygenated compounds, but also contained a small amount of alkanes and alkenes. Further study of the reaction at 0.7 MPa (6.9 atm) revealed that low pressure favored olefinic and paraffinic hydrocarbons and minimized oxygenates, but at this pressure the reaction rate was very low. Because of their pioneering work on catalytic hydrocarbon synthesis, this class of reactions became known as the Fischer-Tropsch (FT) synthesis. 

Natural gas is by far the preferred source of hydrogen. It has been cheap, and its use is more energy efficient than that of other hydrocarbons. The reforming process that is used to produce hydrogen from natural gas is highly developed, environmental controls are simple, and the capital investment is lower than that for any other method. Comparisons of the total energy consumption (fuel and synthesis gas), based on advanced technologies, have been discussed elsewhere (102). 

Synthesis Gas Chemicals. Hydrocarbons are used to generate synthesis gas, a mixture of carbon monoxide and hydrogen, for conversion to other chemicals. The primary chemical made from synthesis gas is methanol, though acetic acid and acetic anhydride are also made by this route. Carbon monoxide (qv) is produced by partial oxidation of hydrocarbons or by the catalytic steam reforming of natural gas. About 96% of synthesis gas is made by steam reforming, followed by the water gas shift reaction to give the desired H2 /CO ratio. 

Methanol [67-56-1] (methyl alcohol), CH OH, is a colorless Hquid at ambient temperatures with a mild, characteristic alcohol odor. Originally called wood alcohol siace it was obtained from the destmctive distillation of wood, today commercial methanol is sometimes referred to as synthetic methanol because it is produced from synthesis gas, a mixture of hydrogen and carbon oxides, generated by a variety of sources. 

Synthetic Fuels. Hydrocarbon Hquids made from nonpetroleum sources can be used in steam crackers to produce olefins. Fischer-Tropsch Hquids, oil-shale Hquids, and coal-Hquefaction products are examples (61) (see Fuels, synthetic). Work using Fischer-Tropsch catalysts indicates that olefins can be made directly from synthesis gas—carbon monoxide and hydrogen (62,63). Shape-selective molecular sieves (qv) also are being evaluated (64). 

Hydrocarbons from Synthesis Gas and Methanol. Two very important catalytic processes in which hydrocarbons are formed from synthesis gas are the Sasol Eischer-Tropsch process, in which carbon monoxide and hydrogen obtained from coal gasification are converted to gasoline and other products over an iron catalyst, and the Mobil MTG process, which converts methanol to gasoline range hydrocarbons using ZSM-5-type 2eohte catalysts. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

Other Methods of Preparation. In addition to the direct hydration process, the sulfuric acid process, and fermentation routes to manufacture ethanol, several other processes have been suggested. These include the hydration of ethylene by dilute acids, the hydrolysis of ethyl esters other than sulfates, the hydrogenation of acetaldehyde, and the use of synthesis gas. None of these methods has been successfilUy implemented on a commercial scale, but the route from synthesis gas has received a great deal of attention since the 1974 oil embargo. 

Synthesis Ga.s, Since petroleum prices rose abmpdy in 1974, the production of ethanol from synthesis gas, a mixture of carbon monoxide and hydrogen, has received considerable attention. The use of synthesis gas as a base raw material has the same drawback as fermentation technology low yields limited by stoichiometry. 

Fischer-Tropsch Synthesis The best-known technology for producing hydrocarbons from synthesis gas is the Fischer-Tropsch synthesis. This technology was first demonstrated in Germany in 1902 by Sabatier and Senderens when they hydrogenated carbon monoxide (CO) to methane, using a nickel catalyst. In 1926 Fischer and Tropsch were awarded a patent for the discovery of a catalytic technique to convert synthesis gas to liquid hydrocarbons similar to petroleum. 

Synthesis gas is a major source of hydrogen, which is used for producing ammonia. Ammonia is the host of many chemicals such as urea, ammonium nitrate, and hydrazine. Carbon dioxide, a by-product from synthesis gas, reacts with ammonia to produce urea. 

Many chemicals are produced from synthesis gas. This is a consequence of the high reactivity associated with hydrogen and carhon monoxide gases, the two constituents of synthesis gas. The reactivity of this mixture was demonstrated during World War II, when it was used to produce alternative hydrocarbon fuels using Fischer Tropsch technology. The synthesis gas mixture was produced then hy gasifying coal. Fischer Tropsch synthesis of hydrocarbons is discussed in Chapter 4. 

About 3 X 109 kg of methanol are produced annually in the United States from synthesis gas, a mixture of carbon monoxide and hydrogen ... 

In run 19, where considerable carbon monoxide conversion was obtained in both stages, the recycle ratio was 1.48 scf recycle gas per scf feed gas. Recycle ratios in the other tests varied from 1.14 to 1.30. The design recycle ratio is 1.67 for lignite coal feed with hydrogen/steam synthesis gas. 

Four technologies have been most commonly used for separating hydrogen, carbon dioxide, and carbon monoxide from synthesis gas ... 

Carpenter-Evans A catalytic process for removing organic sulfur compounds from synthesis gas by hydrogenation to hydrogen sulfide, which is absorbed by iron oxide. The hydrogenation catalyst is nickel sub-sulfide, Ni3S2. Invented by E. V Evans and C. C. Carpenter in England around 1913 and operated in three commercial plants. 

The capture of C02 from process streams has been performed already for some decades in various industries. Examples of the capture of C02 from industrial applications are the production of hydrogen-containing synthesis gas for the production of ammonia or synthetic fuels or the purification of natural gas (from contaminated gas fields). Since in these processes, C02 is usually considered an undesired by-product, it is then released into the atmosphere. 

---