Other Methanol Syntheses

one can speak rather more of coproduction of methanol and fuel gas. Equilibrium adjustment assumed, only 26.7 % of the CO from a synthesis gas containing 50% CO and 50% H2 is converted at 100 bar and 250°C. Thus 5240m synthesis gas would have to be made available to produce Iton of methanol. Of this quantity, about 2100 m would be converted to methanol and the remaining 3 140 m would be obtained as fuel gas with about 60% CO and 40% H2. In other words, only about 32.5 % of the heat carried in the reactor in the synthesis gas is contained in the methanol. 

Chem Systems operate with methanol catalyst attainable on the market but do, however, carry out their own development work also. This is mainly directed at the application of the methanol produced as combustion fuel (not as motor fuel) as this application is definitely in the foreground of the Chem Systems endeavors regarding process development. Crude methanol produced in the reactor with the liquid-entrained catalyst is particularly little suited to manufacturing pure methanol due to its high percentage of byproducts as treatment of this methanol is technically difficult and costly. 

Recent other developments range from use of homogeneous, liquid catalysts to direct oxidation of methane. 

Brookhaven National Laboratory, USA claims a process in which methanol is produced from carbon monoxide and hydrogen over a liquid phase homogeneous catalyst at some 100°C and pressures between 10 and 15 bar. Carbon dioxide - even in small amounts - is detrimental to catalyst lifetime, CO conversion of 94% is expected. Selectivity of the catalyst seems to be extremely high. 

University of Manitoba, Canada, has published [3.27] results of laborattuy tests on direct conversion of methane to methanol. Pressures applied range from 30 to 70 bar, temperatures from 300 to 430° C. At space velocities comparable to those of commercialized processes, the conversion rate is between 4 and 10% of the natural gas feed only, and methanol selectivity is between 70 and 90%, the balance being mainly CO2. As oxidant, pure oxigen has been proposed. 

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The alkalized zinc oxide—chromia process developed by SEHT was tested on a commercial scale between 1982 and 1987 in a renovated high pressure methanol synthesis plant in Italy. This plant produced 15,000 t/yr of methanol containing approximately 30% higher alcohols. A demonstration plant for the lEP copper—cobalt oxide process was built in China with a capacity of 670 t/yr, but other higher alcohol synthesis processes have been tested only at bench or pilot-plant scale (23). 

Its appeal Hes in the fact that synthesis gas can be produced from trash, municipal sewage, scrap wood, sawdust, newsprint, or other waste. The early work of Fischer and Tropsch on methanol synthesis showed that ethanol could be obtained in the process (165) and that by certain modifications the proportion of ethanol in the product could be increased (166). The Hterature concerning this method is extensive (167—176). The conditions that favor ethanol formation are 125—175°C and 1.42 MPa (14 atm) in the presence of reduction catalysts such as powdered iron. 

Examples for calculated heat transfer coefficients are shown in the table on Figure 1.5.1 The physical and other properties are used from the UCKRON-1 Example for methanol synthesis. These properties are ... 

For a first test of the reactor and all associated service installations it is recommended that experiments for methanol synthesis should be carried out even if this reaction is not especially interesting for the first real project. The reason for this recommendation is that detailed experimental results were published on methanol synthesis (Berty et al, 1982) made on a readily available catalyst. This gives a good basis of comparison for testing a new system. Other reactions that have been studied in detail and for which the performance of a catalyst is well known can also be used for test reactions. 

Here a four-step mechanism is described on the framework of methanol synthesis without any claim to represent the real methanol mechanism. The aim here was to create a mechanism, and the kinetics derived from it, that has an exact mathematical solution. This was needed to perform kinetic studies with the true, or exact solution and compare the results with various kinetic model predictions developed by statistical or other mehods. The final aim was to find out how good or approximate our modeling skill was. 

Methanol synthesis will be used many times as an example to explain some concepts, largely because the stoichiometry of methanol synthesis is simple. The physical properties of all compounds are well known, details of many competing technologies have been published and methanol is an important industrial chemical. In addition to its relative simplicity, methanol synthesis offers an opportunity to show how to handle reversible reactions, the change in mole numbers, removal of reaction heat, and other engineering problems. 

Conclusions from the test problems are not limited by any means to methanol synthesis. These results have more general meaning. Other reactions also will be used to explain certain features of the subjects. Yet the programs for the test problem make it possible to simulate experiments on a computer. In turn, computer simulation of experiments by the reader makes the understanding of the experimental concepts in this book more profound and at the same time easier to grasp. 

In the above three processes, the catalysts are all composed of Cu-based methanol synthesis catalyst and methanol dehydration catalyst of AI2O3. The reactors used by JFE and APCI are slurry bubble column, while a circulating slurry bed reactor was used in the pilot plant in Chongqing. It can be foxmd from Table 1 that conversion of CO obtained in the circulating slurry bed reactor developed by Tsinghua University is obvious higher and the operation conditions are milder than the others. 

Skeletal catalysts are usually employed in slurry-phase reactors or fixed-bed reactors. Hydrogenation of cottonseed oil, oxidative dehydrogenation of alcohols, and several other reactions are performed in sluny phase, where the catalysts are charged into the liquid and optionally stirred (often by action of the gases involved) to achieve intimate mixing. Fixed-bed designs suit methanol synthesis from syngas and catalysis of the water gas shift reaction, and are usually preferred because they obviate the need to separate product from catalyst and are simple in terms of a continuous process. 

Thus methanol and ammonia plants are sometimes combined since carbon dioxide, which must be removed from hydrogen to use it for ammonia production, can in turn be used as feed to adjust the COrHj ratio to 1 2 for efficient methanol synthesis. The methanol can be condensed and purified by distillation, bp 65 °C. Unreacted synthesis gas is recycled. Other products include higher boiling alcohols and dimethyl ether. 

Low Hp/CCf ratios under more moderate temperatures and pressures, with copper ased methanol synthesis catalysts possibly alkalinized yield methanol-higher alcohol mixtures (4-6) with rather high contents (5-12 wt %) of other oxygenated molecules (ketones, esters) - (7>8). 

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 ... 

Figures 1 and 2 show the process routes for methanol synthesis. The first one is based on a fluidized bed and includes a pressurized gasifier (Winkler type) that produces a very clean gas, practically free of tars and other impurities from wood distillation. The second route is based on a fixed bed...

The activation of methane [1] is also included as one of the most desired yet not technically viable reactions. Abundant amounts of methane occur with crude oil and as gas in remote locations it is also produced in large quantities during hydrocarbon processing. A large fraction of this methane is flared, because economical use or transportation is not possible. This gas and the abundant resources of methane gas hydrates would make a very suitable feedstock for higher hydrocarbons, if its activation to produce molecules other than synthesis gas were feasible. Despite enormous fundamental and practical efforts [1-5], no applicable method has yet been found for creation of ethylene, methanol, or formaldehyde from methane. 

ZnO exhibits varied catalytic properties, being active for hydrogenation and dehydrogenation reactions, dehydration of alcohols, methanol synthesis, and other reactions. ZnO is a wide-band n-type semiconductor with surface states present in the band gap. It can be doped with cations, and defects can be generated by treatment under oxidizing or reducing conditions (which change the availability of electrons at the surface). 

The preparation of Cu/ZnO catalysts and precursors for the methanol synthesis reaction have been described [87, 88], while others [89] used a mixture of Pt, Ru and a leachable metal such as A1 to prepare catalysts for CO-tolerant catalysts for fuel cells. 

Skeletal Cu-Zn catalysts show great potential as alternatives to coprecipitated Cu0-Zn0-Al203 catalysts used commercially for low temperature methanol synthesis and water gas shift (WGS) reactions. They can also be used for other reactions such as steam reforming of methanol, methyl formate production by dehydrogenation of methanol, and hydrogenolysis of alkyl formates to produce alcohols. In all these reactions zinc oxide-promoted skeletal copper catalysts have been found to have high activity and selectivity. 

It is the reprecipitation of Zn(OH)2 in the porous skeletal copper which provides promotion in methanol synthesis, water gas shift, and other reactions. The highly dispersed reprecipitated Zn(OH)2 decomposes at around 400 K to form ZnO which is an active promoter of copper catalysts. 

The current primary feedstock for industrial methanol synthesis is synthesis gas a mixture of CO, C02> and hydrogen derived from the reforming of natural gas or other hydrocarbons [2], The interconversion of carbon oxides and methanol, central to methanol synthesis and steam reforming, is defined by the following three equilibrium equations ... 

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