Gasoline methanol converted

Mobil Oil Corporation has developed a process on a pilot scale that can successfully convert methanol into 96 octane gasoline. Although methanol can be used directiy as a transportation fuel, conversion to gasoline would eliminate the need to modify engines and would also eliminate some of the problems encountered using gasoline—methanol blends (see Alcohol fuels Gasoline and other motor fuels). 

In case other fuels are used, the fuel cell must be capable of accepting them (direct methanol fuel cell, etc.), or they must be converted to hydrogen, typically using a reformer (natural gas, gasoline, methanol, etc., cf. Chapter 2, Fig. 2.44). The store is now accommodating the fuel of choice. 

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. 

In the eady 1980s, the process was commercialized in New Zealand to convert offshore natural gas to 2200 m /day (14,000 barrels/day) gasoline. Since then some of the methanol has been diverted from fuel production to chemical-grade methanol production by a dding additional methanol refining capacity. 

The MTG process was developed for synfuel production in response to the 1973 oil crisis and the steep rise in crude prices that followed. Because methanol can be made from any gasiftable carbonaceous source, including coal, natural gas, and biomass, the MTG process provided a new alternative to petroleum for Hquid fuels production. New Zealand, heavily dependent on foreign oil imports, utilizes the MTG process to convert vast offshore reserves of natural gas to gasoline (59). 

Catalysts in the ZSM-5 and ZSM-11 family are used to convert methanol into high octane gasoline components in the Mobil MTG process (45). 

Hydrocarbons from Synthesis Gas and Methanol. Two very important catalytic processes in which hydrocarbons are formed from synthesis gas are the Sasol Eischer-Tropsch process, in which carbon monoxide and hydrogen obtained from coal gasification are converted to gasoline and other products over an iron catalyst, and the Mobil MTG process, which converts methanol to gasoline range hydrocarbons using ZSM-5-type 2eohte catalysts. 

Methanol to Ethylene. Methanol to ethylene economics track the economics of methane to ethylene. Methanol to gasoline has been flilly developed and, during this development, specific catalysts to produce ethylene were discovered. The economics of this process have been discussed, and a catalyst (Ni/SAPO 34) with almost 95% selectivity to ethylene has been claimed (99). Methanol is converted to dimethyl ether, which decomposes to ethylene and water the method of preparation of the catalyst rather than the active ingredient of the catalyst has made the significant improvement in yield (100). By optimizing the catalyst and process conditions, it is claimed that yields of ethylene, propylene, or both are maximized. This is still in the bench-scale stage. 

As an alternate to LNG, natural gas can be chemically converted to methanol, chemical feedstocks (such as ethylene), gasoline, or diesel fuel. Most processes start with the conversion of methane to synthesis gas, a mixture of carbon monoxide and hydrogen. This can be done partial oxidation, an exothermic reaction ... 

Many GTL-derived fuels are being considered for blending with gasoline and diesel to achieve emission reductions of particulate matter (PM), carbon monoxide (CO), nitrogen compounds (NOx) and nonmethane hydrocarbons (NMHC). The most promising fuels converted from natural gas are methanol and ethers such as dimethyl ether (DME) and mcthyl-t-bntyl ether (MTBE). 

At the low-molecular-weight end of the spectrum, a process newly commercialized by Mobil for converting methanol into gasoline has significantly expanded opportunities in C-1 chemistry— the upgrading of one-carbon molectrles to mrrlticarbon products. The process involves the use of ZSM-5, a shape-selective zeolite catalyst. (See "Zeolite and Shape-Selective Catalysts" in Chapter 9.)... 

The final step in the methanol-to-gasoline process can be carried out in an adiabatic, fixed-bed reactor using a zeolite catalyst. A product mixture similar to ordinary gasoline is obtained. As is typical of polymerizations, a pure reactant is converted to a complex mixture of products. 

Most mechanistic work has focused on chemical reactions in solution or extremely simple processes in the gas phase. There is increasing interest in reactions in solids or on solid surfaces, such as the surfaces of solid catalysts in contact with reacting gases. Some such catalysts act inside pores of defined size, such as those in zeolites. In these cases only certain molecules can penetrate the pores to get to the reactive surface, and they are held in defined positions when they react. In fact, the Mobil process for converting methanol to gasoline depends on zeolite-catalyzed reactions. 

The first step — hydrogenation of coal — was the same for fuels and rubber. Powdered coal suspended in oil was pumped under great pressure with hydrogen over a catalyst and was converted into a synthetic crude oil. From this crude oil came Leuna gasoline, diesel fuel, iso-octane for aviation gasoline, ethylene oxide, and many other synthetic products. Coal, treated with scalding steam, was also processed into methanol. 

Although the mechanism proposed for the ZSM-5/methanol system adequately explains the production of the primary C2-C5 products, it is not clear how these are converted into the final gasoline product or indeed why this product should be so rich in aromatics. Production of olefins from methanol over zeolite catalysts has previously been described (110, 112) however, the ZSM-5 system appears to be unique with respect to both product selectivity and catalyst stability. Mobil now has some 140 patents relating to the preparation and use of ZSM-5 zeolites and has stated that "given a favorable economic and political climate a commercial unit could be in operation by the early 1980 s (101). 

NExETHERS A process for converting C5, C6, and C7 olefins to ethers for blending into gasoline to increase its octane rating. The process resembles Nextame but uses additional methanol to increase the yield of ethers. 

One of the considerations regarding the use of methanol as a fuel is that it emits higher amounts of formaldehyde, which is a contributor to ozone formation and a suspected carcinogen, compared to gasoline. Proponents of methanol dispute this, saying that one-third of the formaldehyde from vehicle emissions actually comes from the tailpipe, with the other two-thirds forming photochemically, once the emissions have escaped. They state that pure methanol vehicles produce only one tenth as much of the hydrocarbons that are photochemically converted to formaldehyde as do gasoline automobiles. 

Onboard reforming for fuel cells depends on catalytic reactions to convert conventional hydrocarbon fuels, such as gasoline or methanol, into hydrogen that fuel cells can then use to produce electricity to power vehicles. 

Methanol also seems to biodegrade quickly when spilled and it dissolves and dilutes rapidly in water. It has been recommended as an alternative fuel by the EPA and the DOE, partly because of reduced urban air pollutant emissions compared to gasoline. Most methanol-fueled vehicles use a blend of 85% methanol and 15% gasoline called M85. Building a methanol infrastructure would not be as difficult as converting to hydrogen. While methanol can be produced from natural gas, it can also be distilled from coal or even biomass. In the 1980s, methanol was popular for a brief time as an internal-combustion fuel and President Bush even discussed this in a 1989 speech. 

In liquefaction systems wood and wood wastes are the most common fuelstocks. They are reacted with steam or hydrogen and carbon monoxide to produce liquids and chemicals. The chemical reactions that take place are similar to gasification but lower temperatures and higher pressure are used. Liquefaction processes can be direct or indirect. The product from liquefaction is pyrolytic oil which has a high oxygen content. It can be converted to diesel fuel, gasoline or methanol. 

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