Process for producing synthesis gas

Figure 5-2. The ICI process for producing synthesis gas and ammonia (1) desulfurization, (2) feed gas saturator, (3) primary reformer, (4) secondary reformer, (5) shift converter, (6) methanator, (7) ammonia reactor.

The synthesis gas generation process is a noncatalytic process for producing synthesis gas (principally hydrogen and carbon monoxide) for the ultimate production of high-purity hydrogen from gaseous or liquid hydrocarbons. 

The carbon monoxide-hydrogen mixture traditionally was generated from coke, steam, and air by the water-gas method, but this process has been supplanted by steam-hydrocarbon reforming and by the partial oxidation of natural gas. More recently, processes for producing synthesis gas by the partial oxidation of pulverised coal have been introduced. 

AM Gaffney, R Song, R Oswald, D Corbin. Cobalt-Based Catalysts and Process for Producing Synthesis Gas. WO Patent 0,136,323, May 25, 2001. 

A fermentation route to 1-butanol based on carbon monoxide employing the anaerobic bacterium, Butyribacterium methjlotrophicum has been reported (14,15). In contrast to other commercial catalytic processes for converting synthesis gas to alcohols, the new process is insensitive to sulfur contaminants. Current productivities to butanol are 1 g/L, about 10% of that required for commercial viabiUty. Researchers hope to learn enough about the bacteria s control mechanisms to be able to use recombinant DNA to make the cells produce more butanol. 

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. 

As shown in Figure 5.4 and Figure 5.17 and as described for each of the major processes that produce synthesis gas, the Water Gas Shift Conversion or the Carbon Monoxide Shift reaction is one of the traditional purification steps that will still be found in many ammonia plants. The CO must be removed because it acts as a poison to the catalyst that is used in ammonia synthesis. 

The Shell Gasification Process (SGP) is a highly versatile, well-proven, system for producing synthesis gas (H2+CO) from virtually any available fluid hydrocarbon feedstock ranging from natural gas to asphalt. This feedstock flexibility feature can be especially valuable in times of hydrocarbon scarcity. 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

The petroleum industry is now the principal suppHer of ben2ene, toluene, the xylenes, and naphthalene (see BTX processing Feedstocks). Petroleum displaced coal tar as the primary source for these aromatic compounds after World War II because it was relatively cheap and abundantly available. However, the re-emergence of king coal is predicted for the twenty-first century, when oil suppHes are expected to dwindle and the cost of producing chemicals from coal (including new processes based on synthesis gas) will gradually become more competitive (3). 

A possibly more sophisticated method for utilizing biomass to produce synthesis gas is by aqueous phase reforming (APR), a processing method that was developed for carbohydrates and other more readily accessible biomass oxygenates by Dumesic et Valenzuela et al. however,... 

In 1925, Fischer and Tropsch developed a process for producing a mixture of saturated and unsaturated hydrocarbons, and oxygenated products such as alcohols and esters by the reaction of synthesis gas (a mixture of CO and H2) using heterogeneous catalysts of Fe and Co (eq. 1.1) [1],... 

---