Based on Synthesis Gas

Many chemicals are produced from synthesis gas. This is a consequence of the high reactivity associated with hydrogen and carhon monoxide gases, the two constituents of synthesis gas. The reactivity of this mixture was demonstrated during World War II, when it was used to produce alternative hydrocarbon fuels using Fischer Tropsch technology. The synthesis gas mixture was produced then hy gasifying coal. Fischer Tropsch synthesis of hydrocarbons is discussed in Chapter 4. 

Synthesis gas is also an important building block for aldehydes from olefins. The catalytic hydroformylation reaction (Oxo reaction) is used with many olefins to produce aldehydes and alcohols of commercial importance. 

Methanol, the second major product from synthesis gas, is a unique compound of high chemical reactivity as well as good fuel properties. It 

Ammonia is one of the most important inorganic chemicals, exceeded only by sulfuric acid and lime. This colorless gas has an irritating odor, and is very soluble in water, forming a weakly basic solution. Ammonia could be easily liquefied under pressure (liquid ammonia), and it is an important refrigerant. Anhydrous ammonia is a fertilizer by direct application to the soil. Ammonia is obtained by the reaction of hydrogen and atmospheric nitrogen, the synthesis gas for ammonia. The 1994 U.S. ammonia production was approximately 40 billion pounds (sixth highest volume chemical). 

The production of ammonia is of historical interest because it represents the first important application of thermodynamics to an industrial process. Considering the synthesis reaction of ammonia from its elements, the calculated reaction heat (AH) and free energy change (AG) at room temperature are approximately -46 and -16.5 KJ/mol, respectively. Although the calculated equilibrium constant = 3.6 X 108 at room temperature is substantially high, no reaction occurs under these conditions, and the rate is practically zero. The ammonia synthesis reaction could be represented as follows  

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The price of acetaldehyde duriag the period 1950 to 1973 ranged from 0.20 to 0.22/kg. Increased prices for hydrocarbon cracking feedstocks beginning in late 1973 resulted in higher costs for ethylene and concurrent higher costs for acetaldehyde. The posted prices for acetaldehyde were 0.26/kg in 1974, 0.78/kg in 1985, and 0.92/kg in 1988. The future of acetaldehyde growth appears to depend on the development of a lower cost production process based on synthesis gas and an increase in demand for processes based on acetaldehyde activation techniques and peracetic acid. 

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). 

The two major chemicals based on synthesis gas are ammonia and methanol. Each compound is a precursor for many other chemicals. From ammonia, urea, nitric acid, hydrazine, acrylonitrile, methylamines and many other minor chemicals are produced (see Figure 5-1). Each of these chemicals is also a precursor of more chemicals. 

Another fairly recent development based on synthesis gas is the oxo process, in which olefins are reacted with carbon monoxide and hydrogen to produce aldehydes and alcohols. Octyl and nonyl alcohols have been made on a commercial scale since 1948. These long-chain alcohols are used mostly as raw materials for plasticizers. 

An interesting nonpetrochemical alternative developed by Monsanto [2] is based on synthesis gas and NH3. In the first step, acetonitrile is obtained with selectivity of 85% at 300-600°C and pressures up to 35 bar by using Mo/Fe oxide catalysts ... 

The production of higher hydrocarbons directly from methane by catalytic oxidative coupling is a novel methane conversion process which warrants further study. When combined with an ethylene oligomerisation step it is a potential alternative to conventional processes, based on synthesis gas, for producing liquid fuels from methane. However, further research is necessary to provide the information required to assess the commercial prospects for this route. 

In the new efforts to develop a synfuel industry based on synthesis gas from coal the slurry type reactors play a dominant role. For instance, a bubble column slurry reactor was mainly applied in a recent comparative study of various catalysts carried out in Germany. In the US, several pilot plants for syngas conversion processes are under construction which make use of the advantages of the slurry technology. 

Another actual pyrolysis-based biorefinery concept is the Bioliq process that was developed at the Karlsruhe Institute of Technology (KIT).Bioliq aims at the production of synthetic fuels such as Fischer-Tropsch diesel and chemicals from biomass. Synthesis based on synthesis gas requires pressures of up to 10 MPa. High-pressure entrained flow gasification provides high-quality tar-free syngas with low methane contents. 

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