Other Reforming Processes

A unique steam reforming process [495]-[497] has been developed in Japan to the pilot-plant stage. It reportedly can operate without upstream desulfurization and should be able to gasify naphtha, crude oil, and atmospheric or vacuum residues. 

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Natural gas is by far the preferred source of hydrogen. It has been cheap, and its use is more energy efficient than that of other hydrocarbons. The reforming process that is used to produce hydrogen from natural gas is highly developed, environmental controls are simple, and the capital investment is lower than that for any other method. Comparisons of the total energy consumption (fuel and synthesis gas), based on advanced technologies, have been discussed elsewhere (102). 

Mixtures of CO—H2 produced from hydrocarbons, as shown in the first two of these reactions, ate called synthesis gas. Synthesis gas is a commercial intermediate from which a wide variety of chemicals are produced. A principal, and frequendy the only source of hydrogen used in refineries is a by-product of the catalytic reforming process for making octane-contributing components for gasoline (see Gasoline and OTHER MOTOR fuels), eg. 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

In many cases there is an interaction between the carrier and the active component of the catalyst so that the character of the active surface will change. For example, the electronic character of the supported catalyst may be influenced by the transfer of electrons across the catalyst-carrier interface. In some cases the carrier itself has a catalytic activity for the primary reaction, an intermediate reaction, or a subsequent reaction, and a dual-function catalyst is thereby obtained. Materials of this type are widely employed in reforming processes. There are other cases where the interaction of the catalyst and support are much more subtle and difficult to label. For example, the crystal size and structure of supported metal catalysts as well as the manner in which the metal is dispersed can be influenced by the nature of the support material. 

As well as the previously described methods of hydrogen production, there are other commercial processes whose application is restricted to specialised production conditions. These include the partial oxidation of heavy hydrocarbons, autothermal reforming and the Kvcerner process. In addition, there are numerous production processes that are still at the basic research stage, but show promising potential. These primarily include thermochemical hydrogen production, photochemical and biological processes. The main characteristics of these methods are outlined below. For a more detailed discussion, please refer to the relevant specialist literature. 

These are the good things that happen in the cat reforming process because iso-paraffins, naphthenes, and aromatics each have higher octane numbers than the molecules from which they were created. Other changes happen that are not so good. 

Today the two most common methods used to produce hydrogen are (1) steam reforming of natural gas, and (2) electrolysis of water. The predominant method for producing synthesis gas is steam reforming of natural gas, although other hydrocarbons can be used as feedstocks. For example, hydrogen can be produced from the biomass reforming process. 

Steam, at high temperatures (975-1375 K) is mixed with methane gas in a reactor with a Ni-based catalyst at pressures of 3-25 bar to yield carbon monoxide (CO) and hydrogen (H ). Steam reforming is the process by which methane and other hydrocarbons in natural gas are converted into hydrogen and carbon monoxide by reaction with steam over a nickel catalyst on a ceramic support. The hydrogen and carbon monoxide are used as initial material for other industrial processes. 

Other important parameters in the steam reforming process are temperature, which depends on the type of oxygenate, the steam-to-carbon ratio and the catalyst-to-feed ratio. For instance, methanol and acetic acid, which are simple oxygenated organic compounds, can be reformed at temperatures lower than 800 °C. On the other hand, more complex biomass-derived liquids may need higher temperatures and a large amount of steam to gasify efficiently the carbonaceous deposits formed by thermal decomposition. 

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