Methanol dimethyl ether from

A system that has received considerable interest in recent years is the catalytic conversion of methanol to gasoline. Numerous hypotheses have been advanced to explain the mechanism, and solid-state 13 C n.m.r. has played an important role in this respect, in that it can directly examine the organic species in the zeolite without any interference from the inorganic matrix. The initial formation of dimethyl ether from methanol over H-ZSM-5 was proposed by van Hooff 141 subsequent dehydration and methylation reactions lead to lower alkenes,142 which in turn oligomerize at ambient temperature to linear alkyl chains.143 At temperatures of about 373 K, branched alkyl chains are also formed. Many more promising applications can be anticipated in this area. 

Figure 4.14b. Associative reaction path towards formation of dimethyl ether from methanol 16. ...

Dimethyl ether forms as condensation side product of the methanol synthesis from CO/H2. Today, the greatly improved selectivity of modern methanol catalysts has reduced this side-product formation to such an extent that deliberate production of dimethyl ether from methanol at heterogeneous alumina or aluminosilicate contacts is carried out industrially. 

MegaDME A process for making dimethyl ether from methanol. Developed by Lurgi, based on their Mega-Methanol process, but not yet commercialized. 

Yaripour, F. Baghaei, F. Schmidt, I. Perregaard, J. Synthesis of Dimethyl Ether from Methanol over Aluminium Phosphate and SUica-Titania Catalysts. Catal Commun. 2005, 6, 542-549. 

The unit has virtually the same flow sheet (see Fig. 2) as that of methanol carbonylation to acetic acid (qv). Any water present in the methyl acetate feed is destroyed by recycle anhydride. Water impairs the catalyst. Carbonylation occurs in a sparged reactor, fitted with baffles to diminish entrainment of the catalyst-rich Hquid. Carbon monoxide is introduced at about 15—18 MPa from centrifugal, multistage compressors. Gaseous dimethyl ether from the reactor is recycled with the CO and occasional injections of methyl iodide and methyl acetate may be introduced. Near the end of the life of a catalyst charge, additional rhodium chloride, with or without a ligand, can be put into the system to increase anhydride production based on net noble metal introduced. The reaction is exothermic, thus no heat need be added and surplus heat can be recovered as low pressure steam. 

Depending on the reason for converting the produced gas from biomass gasification into synthesis gas, for applications requiring different H2/CO ratios, the reformed gas may be ducted to the water-gas shift (WGS, Reaction 4) and preferential oxidation (PROX, Reaction 5) unit to obtain the H2 purity required for fuel cells, or directly to applications requiring a H2/CO ratio close to 2, i.e., the production of dimethyl ether (DME), methanol, Fischer-Tropsch (F-T) Diesel (Reaction 6) (Fig. 7.6). 

Figure 3 shows the effect of partial pressure of water on the rate of dimethyl ether carbonylation. It is apparent from Figure 3 that the reaction is markedly accelerated by added water. One possible explanation for this is the hydrolysis of dimethyl ether to methanol and its subsequent carbonylation. However, the contribution of the hydrolysis is quite small as shown in Figure 3. Therefore, the carbonylation of dimethyl ether via methanol should be negligible. The role of water for the reaction is not clarified yet.

Many of the existing energy products are being used as fuel for the transport sector and are made from either petrol-based material or from renewable resources such as biomass by some kind of chemical process. The most common biofuels that are being used for transport purposes are dimethyl ether (DME), methanol, ethanol, butanol and biodiesel. 

Early attempts to convert methanol into olefins were based on the zeolite ZSM-5. The Mobil MTO process was based on the fluidised bed version of the MTG technology. Conversion took place at about 500°C allegedly producing almost complete methanol conversion. However, careful reading of the patent Uterature indicates that complete methanol conversion may not have been achieved by this means. Because of incomplete conversion, there would be a necessity to strip methanol and dimethyl ether from water and hydrocarbon products in order to recycle unconverted methanol. In this variant, the total olefin yield is less than 20% of the products of which ethylene is a minor but not insignificant product. The major product is gasoUne. Ethylene is difficult to process and has to be treated specially. Claims that it is possible that ethylene can be recycled to extinction conflict with the known behaviour of ethylene in zeolite catalyst systems and have to be viewed with some suspicion. 

A new CD process for the production of vinyl acetate from acetic acid, ethylene, and oxygen using a Pd-type catalyst at 338 20 K, 2-5 bar was disclosed. This illustrates the wide-ranging possibilities for the application of CD in a variety of processes for the chemical, petrochemical, and petroleum industry. The production of acetic acid from the carbonylation of dimethyl ether or methanol using RD and homogeneous catalyst was also patented. ... 

The specific numerical case used is a ternary mixture of dimethyl ether (DME), methanol (MeOH), and water. The feed composition is 5 mol% DME, 50 mol% MeOH, and 45 mol% water. The feed flow rate is lOOkmol/h, and the feed is fed on Stage 32 of a 52-stage column. The liquid sidestream is withdrawn from Stage 12. The column pressure is set at 11 atm so that cooling water can be used in the condenser (reflux-drum temperature is 323 K with a distillate composition of 98 mol% DME and 2 mol% MeOH). The NRTL physical property package is used. 

This pattern of reaction was identified with methoxide ion as the nucleophile in the formation of dimethyl ether from the reaction of methoxide with methyl benzoate in methanol solution at 100°C. Bunnett, J. F. Robison, M. M. Pennington, F. C. /. Am. Chem. Soc. 1950, 72,2378. 

Olah, G. A., Goeppert, A., Suiya Prakash, G. K. (2009). Chemical recycling of carbon dioxide to methanol and dimethyl ether from greenhouse gas to renewable, environmentally carbon neutral fuels and synthetic hydrocarbons. Journal of Organic Chemistry, 74, 487—498. http //dx.doi.org/10.1021/jo801260f. 

Enthalpy of dilution of poly(ethylene glycol) dimethyl ether in methanol Data extract from Landolt-Bornstein VIII/6D2 Polymers, Polymer Solutions, Physical Properties and their Relations I (Thermodynamic Properties PVT-data and miscellaneous properties of polymer solutions) ... 

Ternary composites have also been used comprising a Fischer-Tropsch catalyst, a methanol synthesis catalyst, and a zeolite [100]. Two Fe-based catalysts (ie, one promoted by K and the other by Ru), two HY zeolites with different acidities, a commercial HZSM-5, and Cu/ZnO/AljOj (methanol synthesis catalyst) were tested in these composites. Dimethyl ether (DME), methanol, and hydrocarbons were formed. Addition of the Cu/ZnO/Al Oj catalyst to a binary mixture of a Fischer-Tropsch catalyst and HZSM-5 results in the increase of the CO conversion by more than 20 times. The DME selectivity decreases as the conversion increases. Y zeolites and the Fischer-Tropsch synthesis catalyst promoted by Ru generated the most active composites. The role of zeolites in the ternary composite is assumed with the DME synthesis. First, methanol is synthesized from syngas on Cu/ZnO/Al Oj then it is dehydrated by an acid catalyst to produce DME and finally, DME initiates FT synthesis, which is then propagated by CO. 

Olah, G. A. Goeppert, A. Surya Prakash, G. K. Chemical Recycling of Carbon Dioxide to Methanol and Dimethyl Ether From Greenhouse Gas to Renewable, Environmentally Carbon Neutral Fuels and Synthetic Hydrocarbons. J. Org. Chem. 2009,74, 487 98. 

Michael, J., D.R Nava, W.A. Payne, and L.J. Stief (1979a), Rate constants for the reaction of atomic chlorine with methanol and dimethyl ether from 200 to 500 K, J. Chem. Phys., 70,... 

The reaction mechanism and rates of methyl acetate carbonylation are not fully understood. In the nickel-cataly2ed reaction, rate constants for formation of methyl acetate from methanol, formation of dimethyl ether, and carbonylation of dimethyl ether have been reported, as well as their sensitivity to partial pressure of the reactants (32). For the rhodium chloride [10049-07-7] cataly2ed reaction, methyl acetate carbonylation is considered to go through formation of ethyUdene diacetate (33) ... 

Dimethyl Ether. Synthesis gas conversion to methanol is limited by equiUbrium. One way to increase conversion of synthesis gas is to remove product methanol from the equiUbrium as it is formed. Air Products and others have developed a process that accomplishes this objective by dehydration of methanol to dimethyl ether [115-10-6]. Testing by Air Products at the pilot faciUty in LaPorte has demonstrated a 40% improvement in conversion. The reaction is similar to the Hquid-phase methanol process except that a soHd acid dehydration catalyst is added to the copper-based methanol catalyst slurried in an inert hydrocarbon Hquid (26). 

By selection of appropriate operating conditions, the proportion of coproduced methanol and dimethyl ether can be varied over a wide range. The process is attractive as a method to enhance production of Hquid fuel from CO-rich synthesis gas. Dimethyl ether potentially can be used as a starting material for oxygenated hydrocarbons such as methyl acetate and higher ethers suitable for use in reformulated gasoline. Also, dimethyl ether is an intermediate in the Mobil MTG process for production of gasoline from methanol. 

Mobil MTG and MTO Process. Methanol from any source can be converted to gasoline range hydrocarbons using the Mobil MTG process. This process takes advantage of the shape selective activity of ZSM-5 zeoHte catalyst to limit the size of hydrocarbons in the product. The pore size and cavity dimensions favor the production of C-5—C-10 hydrocarbons. The first step in the conversion is the acid-catalyzed dehydration of methanol to form dimethyl ether. The ether subsequendy is converted to light olefins, then heavier olefins, paraffins, and aromatics. In practice the ether formation and hydrocarbon formation reactions may be performed in separate stages to faciHtate heat removal. 

Oxygenates and Chemicals A whole host of oxygenated products, i.e., fuels, fuel additives, and chemicals, can be produced from synthesis gas. These include such produc ts as methanol, ethylene, isobutanol, dimethyl ether, dimethyl carbonate, and many other hydrocarbons and oxyhydrocarbons. Typical oxygenate-producing reactions are ... 

Entries 11 and 13 in Table 3.4 present data relating the efiect of methyl substitution on methanol and methylamine. The data show an increased response to methyl substitution. While the propane barrier is 3.4 kcal/mol (compared to 2.88 in ethane), the dimethylamine barrier is 3.6kcal/mol (compared to 1.98 in methylamine) and in dimethyl ether it is 2.7 kcal/mol (compared to 1.07 in methanol). Thus, while methyl-hydrogen eclipsing raised the propane barrier by 0.5 kcal/mol, the increase for both dimethylamine and dimethyl ether is 1.6 kcal/mol. This increase in the barrier is attributed to greater van der Waals repulsions resulting from the shorter C—N and C—O bonds, relative to the C—C bond. 

A solution of cholest-4-en-3-one (139), 1 g, in diethylene glycol dimethyl ether (20 ml) is treated for 1 hr with a large excess of diborane at room temperature under nitrogen and then left for a further 40 min. Acetic anhydride (10 ml) is added and the solution refluxed for 1 hr. The mixture is concentrated to a small volume, diluted with water and extracted with ether. The extracts are washed with 10% sodium hydroxide solution, then with water and dried over sodium sulfate. Removal of the solvent leaves a brown oil (1.06 g) which is purified by chromatography on alumina (activity I). Hexane elutes the title compound (141), 0.68 g mp 76-77°. Successive crystallization from acetone-methanol yields material mp 78-79°, [a]p 66°. 

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