Methane to synthesis gas

Net efficiency includes themial losses in reforming methane to synthesis gas. 

As an alternate to LNG, natural gas can be chemically converted to methanol, chemical feedstocks (such as ethylene), gasoline, or diesel fuel. Most processes start with the conversion of methane to synthesis gas, a mixture of carbon monoxide and hydrogen. This can be done partial oxidation, an exothermic reaction ... 

Partial oxidation of methane to synthesis gas over Ru/Ti02 catalysts... 

Concerning the reaction pathway, two routes have been proposed the sequence of total oxidation of methane, followed by reforming of the unconverted methane with CO2 and H2O (designated as indirect scheme), and the direct partial oxidation of methane to synthesis gas without the experience of CO2 and H2O as reaction intermediates. The results obtained by Schmidt and his co-workers [4, 5] indicate that the direct reaction scheme may be followed in a monolith reactor when an extremely short contact time is employed at temperatures in the neighborhood of 1000°C. However, the majority of previous studies over numerous types of catalysts show that the partial oxidation of methane follows the indirect reaction scheme, which is supported by the observation that a sharp temperature spike occurs near the entrance of the catalyst bed, and that essentially zero CO and H2 selectivity is obtained at low methane conversions (<25%) where oxygen is not fully consumed [2, 3]. A major problem encountered... 

Controlled elimination of mass and heat transport resistances is an important prerequisite for obtaining intrinsic kinetic parameters of the fast exothermic reaction of partial oxidation of methane to synthesis gas. It has been demonstrated that under conditions of strong transport limitations erroneous conclusions concerning the reaction scheme can be derived [7-9]. It was determined in this laboratory that transport limitations are practically absent over a wide range of operating conditions if one portion of the catalyst (< 40 pm) is diluted with -5 portions of an... 

Zhang, Z.L. and Verykios, X.E., Carbon dioxide reforming of methane to synthesis gas over supported Ni catalysts, Catal. Today, 21, 589,1994. 

The forty-eighth volume of Advances in Catalysis includes a description of a new and increasingly well understood class of catalysts (titanosilicates), a review of transmission electron microscopy and related methods applied to catalyst characterization, and summaries of the chemistry and processes of isobutane-alkene alkylation and partial oxidation and C02 reforming of methane to synthesis gas. 

Catalytic Conversion of Methane to Synthesis Gas by Partial Oxidation... 

Co and Fe catalysts have also been studied for the partial oxidation of methane to synthesis gas. Their potential relies on the fact that Co and Fe have higher melting and vaporizing points than Ni. Lower performances were mostly observed, however, which is probably related to the higher activity of CoO and FC2O3 for the complete oxidation of methane [121, 132, 133]. The recognized order of reactivity for partial oxidation is in fact Ni Co > Fe. However, it was observed that the performance of Co improves when a promoter is added. An extensive study of the catalytic partial oxidation of methane over CO/AI2O3 catalysts with different metals (0.1 wt% of Ni, Pt,... 

These values of A Hr are standard state enthalpies of reaction (aU gases in ideal-gas states) evaluated at 1 atm and 298 K. 7VU values of A are in kilojoules per mole of the first species in the equation. When A Hr is negative, the reaction hberates heat, and we say it is exothermic, while, when A Hr is positive, the reaction absorbs heat, and we say it is endothermic. Tks Table 2-2 indicates, some reactions such as isomerizations do not absorb or liberate much heat, while dehydrogenation reactions are fairly endothermic and oxidation reactions are fairly exothermic. Note, for example, that combustion or total oxidation of ethane is highly exothermic, while partial oxidation of methane to synthesis gas (CO + H2) or ethylene (C2H4) are only slightly exothermic. 

In this paper, we summarize results from a small scale methane direct oxidation reactor for residence times between lO and lO seconds. For this work, methane oxidation (using air or oxygen) was studied over Pt-10% Rh gauze catalysts and Pt- and Rh-coated foam and extruded monoliths at atmospheric pressure, and the reactor was operated autothermally rather than at thermostatically controlled catalyst temperatures. By comparing the steady-state performance of these different catalysts at such short contact times, tiie direct oxidation of methane to synthesis gas can be examined independent of the slower reforming reactions. 

The current two-step industrial route for the synthesis of methanol, from coal or methane to synthesis gas and then from synthesis gas to methanol, has certain drawbacks. The economic viability of the whole process depends on the first step, which is highly endothermic. Thus a substantial amount of the carbon source is burned to provide the heat for the reaction. It would be highly desirable, therefore, to replace this technology with a technically simpler, single-step process. This could be the direct partial oxidation of methane to methanol, allowing an excellent way to utilize the vast natural-gas resources. Although various catalysts, some with reasonable selectivity, have been found to catalyze this reaction (see Sections 9.1.1 and 9.6.1), the very low methane conversion does not make this process economically feasible at present. 

K. Gosiewski, Simulations of non-stationary reactors for the catalytic conversion of methane to synthesis gas. Chem. Eng. Sci.,... 

Equally important are structural changes on the micrometer and the millimeter length scales, and eventually real reactors on a centimeter or even meter scale. In the first cases, full-field XAS is a well-matched method for in situ monitoring [6, 13, 25], An illustrative example is the catalytic partial oxidation (CPO) of methane to synthesis gas, a relevant reaction in the future s solid-oxide fuel cells. In Figure 4.3.4, it was... 

Hu YH, Ruckenstein E. Catalytic conversion of methane to synthesis gas by partial oxidation and CO2 reforming. Adv Catal. 2004 48 297-345. 

The ITM Syngas process involves the direct conversion of methane to synthesis gas (see Fig. 22.7). The process utilizes a mixed, conducting ceramic membrane and partial oxidation to produce the synthesis gas.40 The goal of this advanced reformer technology is to reduce the cost of hydrogen production by over 25 percent.59,79... 

The enthalpy of reaction, AH, is the other important thermodynamic parameter to consider. On its own, whether a reaction is exothermic or endothermic will not determine if a reaction is industrially feasible or not. Both exothermic and endothermic processes are known in industry, methanol carbonylation to acetic acid (Equation 3 AH —123 kJ/mol at 200°C), being an example of the former and the steam reforming of methane to synthesis gas, (Equation 4 AH + 227 kJ/mol at 800°C), being an example of the latter. 

Indirect processes for converting natural gas to alcohols and higher hydrocarbons require the initial conversion of methane to synthesis gas (CO/H2). This is a difficult and expensive step normally carried out by steam reforming and partial oxidation (6). Subsequent synthesis gas conversion steps, such as FT synthesis and related processes (1,2), must occur with high selectivity to desired products in order to minimize extensive recycle of undesired products to the initial synthesis gas generation step. C5+ paraffins, low- and intermediate-molecular-weight olefins, and C20+ linear hydrocarbons provide useful feeds in downstream processes leading to fuels and petrochemicals. 

Hamakawa S, Shiozaki R, Hayakawa T, Suzuki K, Murata K, Takehira K, Koizumi M, Nakamura J, and Uchijima T. Partial oxidation of methane to synthesis gas using Ni/Cao.8Sro.2Ti03 anode catalyst. J. Electrochem. Soc. 2000 147 839-844. 

Ostrowski T, Giroir-Fendler A, Mirodatos C, and Mleczko L. Comparative study of the partial oxidation of methane to synthesis gas in fixed-bed and fiuidized-bed membrane reactors Part 11—development of membranes and catalytic measurements. Catal Today 1998 40(2-3) 191-200. 

Claiidge JB, York APE, Brungs AJ, Marquez-Alvarez C, Sloan J, Tsang SC, Green MLH (1998) New catalysts for the conversion of methane to synthesis gas Molybdenum and tungsten carbide. J Catal 180 85... 

At relatively low temperatures (< 800 °C), over most catalysts investigated, the catalytic partial oxidation of methane to synthesis gas is thought to follow the so-called indirect scheme, according to which initially methane is combusted until all... 

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