Methanation water vapor effect

Acetic acid is having a great demand in plastics, textiles, paper, paints, and adhesives industries. At present, it is the produced by the Monsanto process. Alternative route for the synthesis of aeetie acid is by using CO and methane. A South African patent by Freund and Wambach [309] claimed that with one or more metals of group VIA, VIIA, and VIIIA on alumina, the direet synthesis of acetic acid from CO and CH at 100-600°C and 0.1-20 MPa, a selectivity of 70-95% is obtained. Cu-Co oxides [310] and Pd or Pt-based eatalysts [311] are foimd to be effective for the activation of C-H bond in methane. Introduction of oxygen to the reactant system is another way to overeome thermodynamic limitations. Huang et al. [312] explored the eatalytie aetivity of VjOj-PdCyAl OjOn the direct synthesis of acetic acid from CH and CO in the presence of and showed the water-vapor effect on the rate of formation of acetic acid. 

Coping with the greenhouse effect is a vei-y difficult sociopolitical problem. A greenhouse effect existed on Earth long before the Industrial Revolution. Had it not. Earth s surface would be much colder than it is now. The introduction of gases absorbing infrared radiation only enhances the greenhouse effect. Carbon dioxide is not the only gas of importance water vapor and methane, for exam-... 

Effects of Cold Gas Recycle and Approach to Equilibrium. Product gases resulting from various CGR ratios were analyzed (Table XI). For the experiments tabulated, a decrease in the cold recycle ratio resulted consistently in increases in the product gas concentrations of water vapor, hydrogen, and carbon dioxide and a decrease in methane concentration. These trends may be noted in experiment HGR-12 as the CGR ratio decreased from 8.7 1 to 1.2 1, in experiment HGR-13 as it increased from 1.0 1 to 9.1 1, and in experiment HGR-14 as it decreased from 3.0 1 to 1.0 1. These trends indicate that the water-gas shift reaction (CO + H20 —> C02 + H2) was sustained to some degree. Except for the 462-hr period in experiment HGR-14, the apparent mass action constants for the water-gas shift reaction (based on the product gas compositions in Table XI) remained fairly constant at 0.57-1.6. These values are much lower than the value of 11.7 for equilibrium conversion at 400°C. In... 

The catalytic activity of ln/H-ZSM-5 for the selective reduction of nitric oxide (NO) with methane was improved by the addition of Pt and Ir which catalyzed NO oxidation, even in the presence of water vapor. It was also found that the precious metal, particularly Ir loaded in/H-ZSM-5 gave a low reaction order with respect to NO, and then showed a high catalytic activity for the reduction of NO at low concentrations, if compared with ln/H-ZSM-5. The latter effect of the precious metal is attributed to the enhancement of the chemisorption of NO and also to the increase in the amount of NO2 adsorbed on in sites. 

A constant interaction parameter was capable of representing the mole fraction of water in the vapor phase within experimental uncertainty over the temperature range from 100°F to 460°F. As with the methane - water system, the temperature - dependent interaction parameter is also a monotonically increasing function of temperature. However, at each specified temperature, the interaction parameter for this system is numerically greater than that for the methane - water system. Although it is possible for this binary to form a three-phase equilibrium locus, no experimental data on this effect have been reported. 

Table 14.4 summarizes the estimated total direct radiative forcing calculated for the period from preindustrial times to 1992 for C02, CH4, N20, and O, (IPCC, 1996). The estimate for CH4 includes the effects due to its impacts on tropospheric ozone levels or on stratospheric water vapor, both of which are generated during the oxidation of methane. That shown for 03 is based on the assumption that its concentration increased from 25 to 50 ppb over the Northern Flemi-sphere. The total radiative forcing due to the increase in these four gases from preindustrial times to the present is estimated to be 2.57 W m 2. 

Infrared (IR) active gases, like water vapor (H20), carbon dioxide (C02), ozone (03), methane (CH4), nitrous oxide (N20), chlorofluorocarbons CFC-11 (CC13F) and CFC-12 (CC12F2) naturally and anthropogenically present in the Earth s atmosphere, absorb thermal IR radiation emitted by the Earth s surface and atmosphere. This phenomenon is known as the atmospheric greenhouse effect , and the IR active... 

Example 8 Effective Gas Emissivity Methane is burned to completion with 20 percent excess air (air half-saturated with water vapor at 298 K (60°F), 0.0088 mols H20/mol dry air) in a furnace chamber of floor dimensions 3 X 10 m and height 5 m. The whole surface is a gray-energy sink of emissivity 0.8... 

As another example of the effect of water vapor on hydrocarbon formation in discharge, in a paper on the formation of hydrocarbons in model primitive earth atmospheres containing methane and helium (9), the authors state that the presence of water or ammonia decreased the... 

The effects of hydrogen compounds on the behavior of other chemical species, particularly that of ozone in the mesosphere, were first examined by Bates and Nicolet (1950), and have been the subject of numerous subsequent studies (Hampson, 1966 Hunt, 1966 Hesstvedt, 1968 Crutzen, 1969 Nicolet, 1971). The high reactivity of the hydrogen free radicals, especially OH, makes these species of particular importance in atmospheric chemistry. The compounds that initiate the hydrogen radical chemistry are methane (for which the budget was discussed in Section 5.3), water vapor, and molecular hydrogen. 

Unlike HC1 however, hydrogen fluoride does not react appreciably with OH, so that the fluorine atoms, which react with methane, hydrogen, or water vapor, are effectively stabilized as HF. Since the sources of HF and HC1 are similar but their loss rates are quite different as a result of the reaction of OH with HC1 at low altitudes, the HF/HC1 ratio can provide an indication of the abundance of the OH radical (see, e.g., Sze and Ko, 1980). 

Other processes that could contribute to upper stratospheric ozone changes include trends in methane, nitrous oxide, and water vapor. These source gases can, for example, lead to changes in HOx and NOx, which can in turn affect ozone loss rates and the competition between different catalytic cycles. However, the effect of these changes is considerably smaller than the dramatic impact of the five-fold enhancement in chlorine caused by human activities. By the turn of the 21st century, observations and modelling studies showed that chlorine chemistry dominated the trends found in upper stratospheric ozone (see Muller et al., in WMO/UNEP, 1999). 

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