Syngas to Methanol

Methanol is produced from a nonstoichiometric syngas mixture (CC 2 CO H2 = 5 5 90) at 50-100 bar pressure and a temperature between 225°C and 275°C over a Cu/Zn0/Al203 catalyst. The predominant reaction is 

Combining it with the WGS reaction (1) discussed previously, one obtains 

The process is exothermic, and the heat released by the methanol synthesis is used to partially heat up the natural gas for the endothermic synthesis gas generation. 

The modern methanol synthesis catalyst consists of copper, zinc oxide, and alumina. Copper metal is seen as the catalytically active phase, and ZnO as the promoter. It is well known that the interaction between the two components is essential for achieving a high activity, but the nature of the promoting effect is still a matter of debate. Loss of activity is caused by sintering of the Cu crystallites, and, if the feed gas contains impurities such as chlorine and sulfur, by poisoning. 

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ENSOL A combined process for converting syngas to methanol and then to ethanol. Acetic acid is an intermediate. Developed by Humphries Glasgow, in conjunction with BASF and Monsanto. 

High temperature conversion of a 2 1 mixture of syngas to methanol and... 

Reaction (2) is simply the sum of reactions (1) and (3), so even though all reactions progress simultaneously, only reactions (1) and (3) are considered independently, with maximum conversion of syngas to methanol limited by thermodynamic equilibrium. 

Methanol. Methanol is produced by stoichiometric reaction of CO and H2. The syngas produced by coal gasification contains insufficient hydrogen for complete conversion to methanol, and partial CO shifting is required to obtain the desired concentrations of H2, CO, and CO2. These concentrations are expressed in terms of a stoichiometric number, ((H2 — CO)/(H2 + CO2), which has a desired value of 2. In some cases CO2 removal is required to achieve the stoichiometric number target. CO and H2 are then reacted to form methanol in a catalytic methanol synthesis reactor. 

Once syngas and methanol can be produced viably from renewable resources then established synthetic pathways can be used to produce a whole variety of bulk chemical feedstocks (Scheme 6.16). (There is insufficient space to discuss the details here and readers are invited to consult a textbook of industrial chemistry.) By analogy, syngas and/or methanol will become the petroleum feedstock of the future. 

ICI Low Pressure Methanol A process for making methanol from methane and steam. The methanol is first converted to syngas by steam reforming at a relatively low pressure. The syngas is then converted to methanol over a copper-based catalyst ... 

Octamix [Octane mixture] A process for converting syngas to a mixture of methanol with higher alcohols by reducing the CO/H2 ratio below that required for the usual process for making methanol. The process is operated at 270 to 300°C, 50 to 100 bar, in the presence... 

Olefining [Olefin refining] A process for converting syngas or methanol to a mixture of ethylene, propylene, and butenes. The catalyst is a ZSM-5-type zeolite in which some of the aluminum has been replaced by iron. Developed in 1984 by the National Chemical... 

Despite the current decrease of oil prices, the conversion of syngas to alcohols remains an attractive objective. Many companies are involved in alcohols synthesis projects, based on high pressure or low pressure technologies, with motor-fuels and octane boosters as targets. The I.F.P. (France Idemitsu (Japan) R D program is focused on the co-produc-tion of methanol and light alcohols. These product... 

Syngas and methanol. Methanol is one of the top industrial chemicals today. It is produced on a very large scale from fossil-derived syngas by use of a Cu-Zn-Al-oxide catalyst, however, it can of course also be produced in a similar manner from bio-derived syngas. Methanol (and also syngas) can be used as a feedstock to produce dimethyl ether via catalytic dehydration. However, the chemistry involved in these processes is well-known, and will not be considered here, since it has been extensively dealt with in detail elsewhere. ... 

Applications of HT-type catalysts, prepared by the above methods, have been reported in recent years for basic catalysis (polymerization of alkene oxides, aldol condensation), steam reforming of methane or naphtha, CO hydrogenation as in methanol and higher-alcohol synthesis, conversion of syngas to alkanes and alkenes, hydrogenation of nitrobenzene, oxidation reactions, and as a support for Ziegler-Natta catalysts (Table 2). 

Methanol is very important both as a produet and as a feedstock in chemical industry the total world capacity is currently over 30 Mt/a and is rising at about 3% p.a. Syngas is now the only realistic feedstock for making methanol. Major plants to make it from very cheap raw materials have been built in Trinidad, Saudi Arabia and elsewhere these use methane from oil wells, which was previously flared to waste, but can easily be converted into syngas. Such methanol plants use what is termed stranded gas which is natural gas in a remote area where it cannot be economically used for any other purpose. Very large mega-scale methanol plants > 1.5 Mt/a are now built. For example in Trinidad, which is now the world s largest exporter of methanol, with a total production capacity of 6.5 Mt/a. 

Syngas conversion to methanol has been shown to take place on supported palladium catalyst [1]. Methanol can in turn be converted to gasoline over ZSM-5 via the MTG process developed by Mobil [2]. In recent work we have reported syngas (CO/H2) conversion to hydrocarbon products on bifunctional catalysts consisting of a methanol synthesis function, Pd, supported on ZSM-5 zeolites [3]. Work on syngas conversion to hydrocarbon products on Pd/SAPO molecular sieves has been published elsewhere [Thomson et. al., J. CataL. in press].Therefore, this paper will concentrate on propylene conversion. 

As we stated earlier, syngas can be used directly as a fuel, but it is also important as a raw material for producing other fuels. For example, syngas can be directly converted to methanol ... 

Syngas can be burned directly or converted to methanol. Calculate AH° for the conversion reaction ... 

Although biomass-to-methanol technology has yet to be commercialized, laboratory technology suggests that commercial production would be feasible at a cost of about 0.20/L. Assuming that expected improvements in syngas cleanup and a reduction in feedstock costs are realized, the costs may be reduced to the target of 0.15/L as eady as 1998. 

In previous studies the authors have reported that metals oxides such as GaaOa, AI2O3, Zr02 and Cr203 contained in Cu/ZnO-based catalysts have an important role to improve simultaneously the activity and the selectivity[1, 2]. Unlike Cu/ZnO-based catalysts, Raney copper catalysts have not been widely reported in the literature as practical catalysts for methanol synthesis. However, 20 years ago Wainwright and co-workers have been the first to report the potentiel use of Raney Cu and Raney Cu-Zn as catalysts to produce methanol from syngas to use as synthetic liquid fuel [3]. Recent works of Wainwright et al. on methanol synthesis... 

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