Methanol manufacture

Chemicals have long been manufactured from biomass, especially wood (sHvichemicals), by many different fermentation and thermochemical methods. For example, continuous pyrolysis of wood was used by the Ford Motor Co. in 1929 for the manufacture of various chemicals (Table 20) (47). Wood alcohol (methanol) was manufactured on a large scale by destmctive distillation of wood for many years until the 1930s and early 1940s, when the economics became more favorable for methanol manufacture from fossil fuel-derived synthesis gas. 

Synthesis gas is a loose name for hydrogen/carbon monoxide mixtures of varying proportions. These two compounds are so basic, they are too simple to start with for most petrochemicals. The primary applications of synthesis gas are only ammonia and methanol manufacture and a little normal butyl and 2-ethylhexyl alcohol production. 

Table 3.3 gives the total uses of hydrogen. Ammonia production is by far the most important application, followed by methanol manufacture. Hydrogenations in petroleum refineries are an important use. Many other industries utilize hydrogen. Miscellaneous uses include hydrogenation of fats and oils in the food industry, reduction of the oxides of metals to the free metals, pure hydrogen chloride manufacture, and liquid hydrogen as rocket fuel. 

Methanol manufacturing processes in current use have been reported to consume forty four times as much exergy as the theoretical minimum exergy loss estimated above for the direct methanol synthesis [Ref. 16.). 

Figure 8. Current energy consumptions for methanol manufacture by various syngas production...

Methanol. Methanol is a water-soluble, low molecular weight alcohol that may be of increasing importance as a low-sulfur fuel, a chemical feedstock, and perhaps as a gasoline additive or an intermediate in gasoline production. The synthesis of methanol is accomplished by the catalytic conversion of synthesis gas containing two moles of hydrogen for each mole of carbon monoxide. Methanol synthesis is widely practiced in industry on a commercial scale. See Chapter 10 for a discussion of methanol manufacture. 

Ether synthesis produces branched ethers like methyl t-butyl ether (MTBE) by reacting methanol (or ethanol) with branched alkenes such as isobutene. These ethers are valuable for their high octane quality and also, on account of the oxygen they contain, their ability to reduce both CO and hydrocarbon exhaust emissions. Alcohols, such as methanol, manufactured from natural gas or coal, and ethanol, produced by fermentation, are other oxygenated components in limited use. 

Figure 12.20. Polygeneration configuration for the combination of methanol manufacture and IGCC. ASU, air separation unit.

A recent process development may lead to simplified plants for methanol manufacture from synthesis gas with a high carbon oxides to hydrogen ratio. Commercial methanol catalysts in fine powder form are suspended in inert mineral... 

Most of the methanol made until the end of World War II was produced from coke-derived synthesis gas as well as off-gases from fermentation, coke ovens, and steel furnaces. One of the most significant changes in commercial methanol manufacture was the use of natural gas as the feedstock source. There were a number of factors that contributed to the use of natural gas. A natural gas facility produced a higher quality synthesis gas with fewer impurities, and in the United States natural gas was available in almost unlimited quantities. In 1946, about 71% of the carbon monoxide used in feeding methanol plants was derived from coke or coal By 1948, about 77% was obtained from natural gas [2]. 

Additionally, reactor effluent gas in partial oxidation always contains sulfur in the form of H2 and COS, which requires eventual downstream removal before the synthesis gas can be used for methanol manufacturing. 

Combined reforming has been successfully applied in grass roots applications, but it may find its best application in the potential retrofit of ammonia plants to methanol manufacturing. Use of combined reforming in a retrofit enables the ammonia producer to convert to methanol production and maximize production while achieving an acceptable return on investment (pretax, internal rate of return, IRR, of more than 20%). 

Prereforming is not a widely used practice, due in part to the limited number of commercially available catalysts and more specifically to the wide use of li t natural gas feedstocks for methanol manufacture. In recent years more active and stronger prereforming catalysts have been successfully demonstrated in commercial operation, and these will likely be used more frequently when heavy... 

In the 1920s, one of the early important synthetic organic industrial chemicals from the aliphatic (chain molecule) branch was synthetic alcohol, particularly methyl alcohol (or methanol), marking another dramatic shift from natural to synthetic. Du Pont was one of two American firms to put synthetic methanol, manufactured as a by-product to its synthetic ammonia plant and drawing heavily on newer techniques in high pressure technologies, on the market in... 

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