Methane from carbon monoxide and hydrogen

Tn the synthesis of methane from carbon monoxide and hydrogen, it is desired to operate the reactor or reactors in such a way as to avoid carbon deposition on catalyst surfaces and to produce high quality product gas. Since gas compositions entering the reactor may vary considerably because of the use of diluents and recycle gas in a technical operation, it is desirable to estimate the effects of initial gas composition on the subsequent operation. Pressure and temperature are additional variables. 

The reactions studied were the catalytic formation of methane from carbon monoxide and hydrogen (according to Sabatier (34), normal pressure), the catalytic hydrogenation of unsaturated hydrocarbons and also of unsaturated fatty acids ( fat hardening according to Normann (35)). Here again, a certain analogy was established between... 

The formation of methane from carbon monoxide and hydrogen using a nickel catalyst was studied by Parsley. The reaction... 

Following earlier work in which the intermediate in the formation of methane from carbon monoxide and hydrogen was found to be carbon, McCarty and Wise carried out a thorough study of the system. Four types of carbon were found to be formed from carbon monoxide on nickel at 550 50K. Chemisorbed carbon atoms reacted readily with hydrogen as did the initial layers of nickel carbide. Further deposits of the carbide, amorphous carbon, and crystalline elemental carbon were much less reactive and the kinetics of the reaction should be described by the established rate laws. Conversion of the more active to the less active forms of carbon occurred above approximately 600 K. 

In 1902 Sabatier and Senderens (5) reported the synthesis of methane from carbon monoxide and hydrogen in the presence of nickel and cobalt catalysts. 

Several important chemical reactions for the conversion of coal to methane are shown in Table 2. Steam conversion involves the reaction of coal with steam to produce hydrogen and carbon monoxide. Hydrogen conversion is a reaction in which coal and hydrogen react to form methane. Oxygen conversion produces hydrogen and carbon monoxide by partial oxidation of coal. Methan-ation involves a reaction in which methane and water are produced from carbon monoxide and hydrogen. The water gas shift reaction between carbon monoxide and steam produces carbon dioxide and hydrogen. 

Another important use of methane is its conversion into synthesis gas (or syn-gas), a mixture of hydrogen gas and carbon monoxide as shown in Figure 17.1. Syn-gas can also be derived from coal. When this occurs, it is called water gas. Interestingly, the reaction of methane giving carbon monoxide and hydrogen can be reversed so that methane can be produced from coal through this route. 

Methanol can also be produced through a two-step process comprising of steam reforming of methane and methanol synthesis from carbon monoxide and hydrogen. The first step of steam reforming of methane consists of the following two reactions ... 

Fig. 2.19. Standard free energies of formation of hydrocarbons and alcohols from carbon monoxide and hydrogen with water as by-roduct. A, ethanol B, methanol C, acetylene D, benzene E, propylene F, ethylene G, propane H, ethane I, methane [7].

Derivation (1) By high-pressure catalytic synthesis from carbon monoxide and hydrogen (2) partial oxidation of natural gas hydrocarbons (3) several processes for making methanol by gasification of wood, peat, and lignite have been developed but have not yet proved out commercially (4) from methane with molybdenum catalyst (experimental). 

The equilibrium conversion in the steam reforming of methane to carbon monoxide and hydrogen is determined from the two equilibrum expressions shown in Example 1.1. In this second example a large hydrogen plant making 100,000 Nm /h of H2 is considered. 

A mixture of the two reactants carbon monoxide and hydrogen is called synthesis gas and IS prepared by several processes The most widely used route to synthesis gas employs methane (from natural gas) and gives a 3 1 hydrogen to carbon monoxide ratio... 

Figure 2.8 The surface reaction between adsorbed carbon monoxide and hydrogen to methane over rhodium catalysts occurs at lower temperatures in the presence of a vanadium oxide promoter, which is known to enhance the rate of CO dissociation (from Koerts el al. 113]). 

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