Methanol synthesis gas and

Nature hasn t provided any convenient sources of pure CO and H2. There s some of each contained in natural gas but usually not in sufficient quantities to justify going after it. But these two compounds, either in the combined state or separate, are readily convertible to a number of commercial compounds. With that as a motivator, several processes have been developed to convert natural gas to synthesis gas. Natural gas is largely methane (CH4), and that provides a source of carbon and hydrogen. Air or water provides the other necessary ingredient, oxygen. 

Synthesis gas can easily be confused with the oxymoron synthetic natural gas, SNG. Both are sometimes called syngas. But SNG is basically methane made from petroleum products, like naphtha or propane, or from coal. It s used as a substitute for or supplement to natural gas. 

The two predominant methods oPmaking synthesis gas are steam reforming and partial oxidation. Both are quite simple. The steam reforming method involves passing methane or naphtha plus steam over a nickel catalyst. The reaction, if methane is the feedstock, is  

The reaction relies on the brute force of high temperatures and pressures and must be carried out in hardware much like the cracking furnaces described in the ethylene chapter. As always with cracking, undesirable reactions occur, resulting in the formation of CO2 and carbon. The latter is particularly a nuisance because it sets down on the catalyst and deactivates it. 

Like the steam reforming method, this process takes place at severe conditions, high temperatures and pressures, but no catalyst. The reaction is 

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Cyclopentadiene itself has been used as a feedstock for carbon fiber manufacture (76). Cyclopentadiene is also a component of supported metallocene—alumoxane polymerization catalysts in the preparation of syndiotactic polyolefins (77), as a nickel or iron complex in the production of methanol and ethanol from synthesis gas (78), and as Group VIII metal complexes for the production of acetaldehyde from methanol and synthesis gas (79). 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

Production of Vinyl Acetate from Methanol and Synthesis Gas... 

It will be shown that Reactions 2 and 3 can be made to proceed at a high rate and with a high selectivity. Combined with simple esterification. Reactions 2 and 3 form a basis for two-step routes for the synthesis of respectively ethyl acetate and propionic acid starting from methanol and synthesis gas as the only feedstock. 

Higher alcohol formation from synthesis gas is also known to occur over MoS2-based catalysts. The alcohol product distribution is quite different from the modified methanol synthesis catalysts and consists primarily of linear alcohols [114], In particular, the product distribution with Cs/Co/MoS2 catalysts has a maximum in the yield of ethanol [115], A modification of this synthesis in which higher alcohols formed from methanol and synthesis gas has been claimed by Quarderer et aL [116]. As K2C02-promoted CoS/MoS2 catalyst,... 

Currently, almost all acetic acid produced commercially comes from acetaldehyde oxidation, methanol or methyl acetate carbonylation, or light hydrocarbon Hquid-phase oxidation. Comparatively small amounts are generated by butane Hquid-phase oxidation, direct ethanol oxidation, and synthesis gas. Large amounts of acetic acid are recycled industrially in the production of cellulose acetate, poly(vinyl alcohol), and aspirin and in a broad array of other... 

Methane. The largest use of methane is for synthesis gas, a mixture of hydrogen and carbon monoxide. Synthesis gas, in turn, is the primary feed for the production of ammonia (qv) and methanol (qv). Synthesis gas is produced by steam reforming of methane over a nickel catalyst. 

Ethanol can also be obtained by the reaction of methanol with synthesis gas at 185°C and under pressure (6.9—20.7 MPa or 68—204 atm) in the presence of a cobalt octacarbonyl catalyst (177). However, although ethanol was the primary product, methyl formate, methyl, propyl and butyl acetates, propyl and butyl alcohols, and methane were all present in the product. 

Although methanol from synthesis gas has been a large-scale industrial chemical for 70 years, the scientific basis of the manufacture apparently can stand some improvement, which was undertaken by Beenackers, Graaf, and Stamhiiis (in Gheremisinoff, ed., Handbook of Heat and Mass Transfer, vol. 3, Gulf, 1989, pp. 671—699). The process occurs at 50 to 100 atm with catalyst of oxides of Gii-Zn-Al and a feed stream of H2, GO, and GO2. Three reactions were taken for the process ... 

The production of methanol from synthesis gas is a well-established process (23, 102), and there have been predictions that methanol itself could become the fuel of the future (103). Whether or not this prediction will prove correct is debatable4 meanwhile, Mobil suggests that coupling known methanol production technology with their new process provides an economically attractive alternative to both Fischer-Tropsch fuels and direct utilization of methanol (104). 

The activity and stability of skeletal catalysts can be improved with the use of additives, often referred to as promoters. These can be added to the alloy before leaching, or alternatively can be added to the leaching solution [16-19], An example is the use of zinc to promote skeletal copper for the catalytic synthesis of methanol from synthesis gas [20-22], Mary other promoters have been considered, both inorganic and organic in nature. 

The next 10 chapters cover a collection of petrochemicals not altogether related to each other. Synthesis gas is a basic building block that leads to the manufacture of ammonia and methanol. MTBE is made from methanol from synthesis gas (with a little isobutylene thrown in). The alcohols in Chapter 14 and 15, the aldehydes in 16, the ketones in 17, and the acids in 18 are all closely related to each other by looks, though the routes to get to them are perplexingly different. Alpha olefins and the plasticizer and detergent alcohols have the same roots and routes, but different ones from the rest. Maleic anhydride, acrylonitrile, and the acrylates— well, they re all used to make polymers and they had to be somewhere. 

BASF led the development of a route based on ethylene and synthesis gas. Its four step process begins with the production of propionaldehyde from ethylene, CO, and H2 using a proprietary catalyst mixture that they aren t telling anything about. Reaction with formaldehyde gives methacrolein. The last two steps are the same as above—oxidation with air yields the MAA subsequent reaction with methanol yields MMA. 

As we learned in Chapters 3 and 4, many inorganic compounds, not just ammonia, are derived from synthesis gas, made from methane by steam-reforming. In the top 50 this would include carbon dioxide, ammonia, nitric acid, ammonium nitrate, and urea. No further mention need be made of these important processes. We discussed MTBE in Chapter 7, Section 4, and Chapter 10, Section 9, since it is an important gasoline additive and C4 derivative. In Chapter 10, Section 6, we presented -butyraldehyde, made by the 0x0 process with propylene and synthesis gas, which is made from methane. In Chapter 11, Section 8, we discussed dimethyl terephthalate. Review these pertinent sections. That leaves only two chemicals, methanol and formaldehyde, as derivatives of methane that have not been discussed. We will take up the carbonylation of methanol to acetic acid, now the most important process for making this acid. Vinyl acetate is made from acetic... 

For example, the reaction of methyl acetate and synthesis gas at 170 C and 5000 psig with a Co-Lil-NPh catalyst results in the formation of acetaldehyde and acetic acid. The rate of acetaldehyde formation is 4.5 M/hr, and the yield based on Equation 15 is nearly 100%. Methane (1-2%) and ethyl acetate (1-2%) are the only by-products. The product mixture does not contain water, methanol or 1,1-dimethoxyethane. The acetic acid can easily be recycled by esterification with methanol in a separate step. 

Methane is an important starting material for numerous other chemicals. The most important of these are ammonia, methanol, acetylene, synthesis gas, formaldehyde, chlorinated methanes, and chlorofluorocarbons. Methane is used in the petrochemical industry to produce synthesis gas or syn gas, which is then used as a feedstock in other reactions. Synthesis gas is a mixture of hydrogen and carbon monoxide. It is produced through steam-methane reforming by reacting methane with steam at approximately 900°C in the presence of a metal catalyst CH4 + H20 —> CO + 3H2. Alternately, methane is partially oxidized and the energy from its partial combustion is used to produce syn gas ... 

Twenty-five years ago the only oxygenated aliphatics produced in important quantities were ethyl and n-butyl alcohols and acetone made by the fermentation of molasses and grain, glycerol made from fats and oils, and methanol and acetic acid made by the pyrolysis of wood. In 1927 the production of acetic acid (from acetylene) and methanol (from synthesis gas) was begun, both made fundamentally from coal. All these oxygenated products are still made from the old raw materials by the same or similar processes, but the amount so made has changed very little in the past quarter century. Nearly all the tremendous growth in the production of this class of compounds has come from petroleum hydrocarbons. 

The use of a mixed oxygen ion-electronic conductor membrane for oxygen separation with direct reforming of methane, followed by the use of a mixed protonic-electronic membrane conductor for hydrogen extraction has also been proposed in the literature [34]. The products are thus pure hydrogen and synthesis gas with reduced hydrogen content, the latter suitable, for example, in the Fish-er-Tropsch synthesis of methanol [34]. 

Synthesis gas (CO and H2) production contributes a large fraction, approximately 60%, of the cost of methanol. The synthesis gas for methanol used to be manufactured by coke gasification, but now is almost exclusively produced by steam reforming of natural gas. 

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