Steam reforming of naphtha

Use of a special catalyst in the tubular reformer, and a special start-up system 

Fewer reformer tubes per quantity of hydrogen and CO produced at equal heat loads per unit area 

Currently, naphtha reforming is of minor importance. Some hydrogen and syngas production based on naphtha still takes place at a few locations with no access to NG. 

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The primary sources of toluene and xylenes are reformates from catalytic reforming units, gasoline from catcracking, and pyrolysis gasoline from steam reforming of naphtha and gas oils. As mentioned earlier, solvent extraction is used to separate these aromatics from the reformate mixture. 

A fuel cell produces electricity directly from the electrochemical reaction of hydrogen, from a hydrogen-containing fuel, and oxygen from the air. Hydrogen is industrially produced by steam reformation of naphtha oil, methane and methanol. High-purity hydrogen has been mainly used as a fuel for low-temperature fuel cells such as polymer or alkaline electrolyte fuel cells (Lin and Rei, 2000). 

The overall reacdons which occur in the steam reforming of naphtha are ... 

By far the most widespread method of producing synthesis gas for methanol production today is via steam reforming of naphtha and lighter hydrocarbons. The process routes for both natural gas steam reforming and naphtha reforming are virtually identical, so we shall consider only natural gas reforming. Since the ICI LP methanol process was... 

Table 13.6 Activity of nickel-uranium oxide catalysts for steam reforming of naphtha [72],...

But how ubiquitous actually are alkalis in the promotion of reactions catalyzed at metal surfaces An examination of recent authoritative sources [6,7] shows that the majority of medium-to large-scale processes do not employ alkali promoters, even when one includes nonmetallic (i.e., metal oxide) catalysts. In a number of cases (e.g., steam reforming of naphtha) it seems clear that the role of alkali is simply to reduce the acidity of the oxide support. There are famous cases, of course, where the presence of alkali species on the catalytically active metal surface is critically important to the chemistry. Notable are ethene epoxidation (Ag-Cs), ammonia synthesis (Fe-K), acetoxylation of ethene to vinyl acetate (Pd, Pd/Au-K), and Fischer-Tropsch synthesis (Fe, Co, Ru-K). The first three are major industrial... 

A general reaction mechanism for steam reforming of naphtha compounds is shown in Reaction 2.13. The reactions presented previously also apply to this process. 

The purpose of the present paper was 10 study the feasibility of using the hydrogenolysis of cyclopentane and the hydrogenation of benzene, typical examples of structure-sensitive and nonstructure-sensitive reactions, to measure the residual activity of specific centers remaining after coke is deposited on supported Ni and Ni-K catalysts. Potassium was chosen as the promoter, for it is often used in the formulation of nickel-based catalyst for steam reforming of naphthas (refs. 2-3). Comparisons between the promoted and unpromoted catalysts were performed at two different extents of metal-support interaction, which were caused by calcination to 400 or 700°C Some attention was paid to changes in selectivity induced by alkali promotion and/or carbon deposition. 

Steam reforming of naphtha is well established in industry. Characteristics of the reactions are summarized including a discussion of possibilities to control carbon formation by catalyst formulation. The progress in tubular reforming of natural gas related mainly to use of higher temperatures can be implemented for liquid feedstocks by installation of an adiabatic prereformer. This is illustrated by industrial examples. 

In the steam reforming of naphtha, potassium promoters accelerate the reaction of carbon with steam. However, this leads to formation of KOH, which sublimes. In this case, potassium aluminosilicate was successfully used as promoter. In the presence of steam and CO2 it decomposes into K2CO3 and KOH to an extent that is just sufficient to remove the coke that is formed. This prolonged catalyst lifetimes to 4-5 years [T35]. 

Various mixtures of carbon monoxide and hydrogen, known as synthesis gas, obtained from steam reforming of natural gas (methane) or, in a few cases, steam reforming of naphtha. 

Low prices for natural gas in the U.S. and naphtha in Europe prompted a change in feedstock. In the U.K., town gas was also produced by the steam reforming of naphtha, which provided about 90% of supplies in 1968, but was totally displaced by the newly found natural gas during the 1970s. European production of synthesis gas for chemical processing is now almost solely based on steam reforming of natural gas. 

The steam reforming of naphtha is, in essence, the reverse of the Fischer-Tropsch reaction, and is carried out under very similar conditions to methane reforming. 

The process for steam reforming of naphtha was developed mainly by ICI in England and has been widely used in Europe, Japan, and many developing countries. The main technical problem was to avoid carbon formation on the reforming catalyst without excessive steam... 

The other uses as catalysts are for synthesis of ammonia, methylation of carbon monoxide or carbon dioxide, steam reforming of naphtha and LPG, decomposition of peroxide, and treatment of waste water, etc. Market prices of precious metals are shown in Table 16.2 [3]. Ruthenium has a low price compared to a precious metal. 

Darwish, N.A., et al. 2004. Feasibility of the direct generation of hydrogen for fuel-cell-powered vehicles by on-board steam reforming of naphtha. Fuel 83 409 17. 

Rostrup-Nielsen, J. R., Hydrogen via Steam Reforming of Naphtha, Chem. Eng. Prog., September, 1977. 

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