Nickel methane

Catalyst Poisons. Hausberger, Atwood, and Knight (33) reported that nickel catalysts are extremely sensitive to sulfides and chlorides. If all materials which adversely affect the performance of a catalyst were classified as poisons, then carbon laydown and, under extreme conditions, water vapor would be included as nickel methanation catalyst poisons. 

Intimate mixing of the components can lead to the formation of compounds or of solid solutions of the components which are difficult to reduce at 300°C but which, when reduced, contain well dispersed and well stabilized nickel. Methanation catalysts in practice therefore are compromises which combine optimum reducibility with activity and stability. As an example of compound formation, alumina readily forms with nickel... 

Catalyst Section. The design criteria for the HYGAS plant methanation section were developed in the late 1960 s (10). At that time, three commercially available nickel methanation catalysts and one ruthenium... 

A. Hausberger As we mentioned earlier, the light hydrocarbons do not seem to affect catalyst activity, and they do reform into methane. However, you can increase the hydrocarbon content to levels where they do depress the methanation activity. If the hydrocarbons are high enough in unsaturation, they will form carbon when they get to a certain level. As far as hydrogen cyanide and ammonia are concerned, we don t expect them to affect the nickel methanation catalyst. 

W. Shen, J. Dumesic and C. Hill, "Deactivation of Nickel Methanation Catalysts Induced by the Decomposition of Iron Carbonyl", J. Catal.. 1983,84, 119-134. 

Since sulfur gases poison nickel methanation catalysts, sulfur material balances were done to determine the extent of sulfur buildup on the catalyst. This was accomplished by determining the total sulfur in the methanation catalyst and coal charged to the reactor and again on the ash and catalyst removed from the reactor. Representative results for 10 independent runs under similar experimental conditions are in Table IV. These data demonstrate that some of the sulfur is lost to the system, some remains in the ash, and some reacts with the catalyst. Furthermore, the considerable variance of the data for the independent runs indicates that the fate of the sulfur is very sensitive to experimental conditions. 

The per cent of the coal s original sulfur that has been deposited on the nickel methanation catalyst is shown in Table IV it amounts to between 23 and 47%. Although x-ray diffraction failed to reveal the combined form of this sulfur, probably because of its small concentration, it is presumed to be nickel sulfide formed by Reaction 6 ... 

A high heating value product gas ( 850 Btu/scf, C02-free) can be produced directly from coal-steam reactions using a single-stage reactor in conjunction with a multiple catalyst. The conversion ( 60%) is carried out at 2 atm and 650°C. The multiple catalyst consists of potassium carbonate and a nickel methanation catalyst. The influence of each catalyst on the coal-steam reactions is combined in the integrated system. Potassium carbonate increases the total gas production and rate while the nickel catalyst hydrocracks the evolved liquids and methanates the carbon oxides. 

Bartholomew, C.H. and Jarvi, G.A. (1979) Sulfur poisoning of nickel methanation catalysts I. in situ deactivation by H2S of nickel and nickel bimetallics. Journal of Catalysis, 60,257-269. 

Reactions (1) - (4) require a catalyst, which typically is supported nickel. Methane may also be converted by means of oxygen into synthesis gas by partial oxidation ... 

Oxygenate removal. Carbon monoxide is converted catalytically to hydrogen and carbon dioxide in two separate stages, the high- and low-temperature shift reactions. Carbon dioxide is removed by any of the available proprietary processes, and traces of residtral carbon monoxide are converted to methane over a nickel methanation catalyst. Any water formed in this stage can be removed by molecirlar sieves, or by washing with product ammonia. 

Beebe T P, Goodman D W, Kay B D and Yates J T Jr 1987 Kinetics of the activated dissociation adsorption of methane on low index planes of nickel single crystal surfaces J. Chem. Phys. 87 2305... 

This reaction is an undesirable side reaction in the manufacture of hydrogen but utilised as a means of removing traces of carbon monoxide left at the end of the second stage reaction. The gases are passed over a nickel catalyst at 450 K when traces of carbon monoxide form methane. (Methane does not poison the catalyst in the Haber process -carbon monoxide Joes.)... 

This is the point group to which all regular tetrahedral molecules, such as methane (Figure 4.12a), silane (SiFl4) and nickel tetracarbonyl (Ni(CO)4), belong. 

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. 

Direct hydrohquefaction of biomass or wastes can be achieved by direct hydrogenation of wood chips on treatment at 10,132 kPa and 340 to 350°C with water and Raney nickel catalyst (45). The wood is completely converted to an oily Hquid, methane, and other hydrocarbon gases. Batch reaction times of 4 hours give oil yields of about 35 wt % of the feed the oil contains about 12 wt % oxygen and has a heating value of about 37.2 MJ /kg (16,000 Btu/lb). Distillation yields a significant fraction that boils in the same range as diesel fuel and is completely miscible with it. 

Methanation of the clean desulfurized main gas (less than 1 ppm total sulfur) is accompHshed in the presence of a nickel catalyst at temperatures from 260—400°C and pressure range of 2—2.8 MPa (300—400 psi). Equations and reaction enthalpies are given in Table 4. 

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Steam Reforming. When relatively light feedstocks, eg, naphthas having ca 180°C end boiling point and limited aromatic content, are available, high nickel content catalysts can be used to simultaneously conduct a variety of near-autothermic reactions. This results in the essentiaHy complete conversions of the feedstocks to methane ... 

Goal Upgrading via Fischer-Tropsch. The synthesis of methane by the catalytic reduction of carbon monoxide and hydrogen over nickel and cobalt catalysts at atmospheric pressure was reported in 1902 (11). 

Methane. The largest use of methane is for synthesis gas, a mixture of hydrogen and carbon monoxide. Synthesis gas, in turn, is the primary feed for the production of ammonia (qv) and methanol (qv). Synthesis gas is produced by steam reforming of methane over a nickel catalyst. 

Thermodynamically, the formation of methane is favored at low temperatures. The equilibrium constant is 10 at 300 K and is 10 ° at 1000 K (113). High temperatures and catalysts ate needed to achieve appreciable rates of carbon gasification, however. This reaction was studied in the range 820—1020 K, and it was found that nickel catalysts speed the reaction by three to four orders of magnitude (114). The Hterature for the carbon-hydrogen reaction has been surveyed (115). 

Nickel catalysts are also used for steam methane reforming. Moreover, nickel catalysts containing potassium to inhibit coke formation from feedstocks such as LPG and naphtha have received wide appHcation. 

Na.tura.1 Ga.s Reforma.tion. In the United States, most hydrogen is presently produced by natural gas reformation or methane—steam reforming. In this process, methane mixed with steam is typically passed over a nickel oxide catalyst at an elevated temperature. The reforming reaction is... 

In the catalytic steam reforming of natural gas (see Fig. 2), the hydrocarbon stream, principally methane, is desulfurized and, through the use of superheated steam (qv), contacts a nickel catalyst in the primary reformer at ca 3.04 MPa (30 atm) pressure and 800°C to convert methane to H2. 

In the Sabatier reaction, methane and water are formed over a nickel— nickel oxide catalyst at 250°C. The methane is recovered and cracked to carbon and hydrogen, which is then recycled ... 

Most commercial methanator catalysts contain nickel, supported on alumina, kaolin, or calcium aluminate cement. Sulfur and arsenic are poisons to the catalyst, which can also be fouled by carry-over of solvent from the CO2 removal system. 

Steam Reforming Processes. In the steam reforming process, light hydrocarbon feedstocks (qv), such as natural gas, Hquefied petroleum gas, and naphtha, or in some cases heavier distillate oils are purified of sulfur compounds (see Sulfurremoval and recovery). These then react with steam in the presence of a nickel-containing catalyst to produce a mixture of hydrogen, methane, and carbon oxides. Essentially total decomposition of compounds containing more than one carbon atom per molecule is obtained (see Ammonia Hydrogen Petroleum). 

Hydrogenation Reactions. Hydrogen over a nickel, platinum, or paladium catalyst can partially or totally saturate the aromatic ring. Thermal hyrogenolysis of toluene yields benzene, methane, and biphenyl. 

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