Methanol/synfuels

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). 

With the recent development of zeolite catalysts that can efficiently transform methanol into synfuels, homogeneous catalysis of reaction (2) has suddenly grown in importance. Unfortunately, aside from the reports of Bradley (6), Bathke and Feder (]), and the work of Pruett (8) at Union Carbide (largely unpublished), very little is known about the homogeneous catalytic hydrogenation of CO to methanol. Two possible mechanisms for methanol formation are suggested by literature discussions of Fischer-Tropsch catalysis (9-10). These are shown in Schemes 1 and 2. 

MTG [Methanol to gasoline] A common abbreviation for any process achieving this conversion, notably the Mobil process. This uses as a catalyst the synthetic zeolite ZSM-5, invented at the Mobil Research Laboratory in 1972. The process was first disclosed in 1976 and commercialized in 1985 by New Zealand Synfuels, a joint venture of Mobil Corporation and Petrocorp. In 1990, this process was providing one third of New Zealand s gasoline requirements. 

Figure 17.24. Types of reactors for synthetic fuels [Meyers (Ed.), Handbook of Synfuels Technology, McGraw-Hill, New York, 1984], (a) ICI methanol reactor, showing internal distributors. C, D and E are cold shot nozzles, F = catalyst dropout, L = thermocouple, and O = catalyst input, (b) ICI methanol reactor with internal heat exchange and cold shots, (c) Fixed bed reactor for gasoline from coal synthesis gas dimensions 10 x 42 ft, 2000 2-in. dia tubes packed with promoted iron catalyst, production rate 5 tons/day per reactor, (d) Synthol fluidized bed continuous reactor system for gasoline from coal synthesis gas.

Methanol production is not a "capital intensive" process as compared to other synfuel production systems. Fixed capital cost is between US 0.21 and 0.35 per liter/year of installed capacity. This investment cost is similar to that needed for ethanol production in Brazil. 

The zeolite-catalyzed methanol conversion technology, whether the desired product is gasoline, diesel, jet fuel or ethylene for petrochemicals, will provide new opportunities for synfuels in the coming decades. 

The MTG process utilised by Synfuel is based on a fixed-bed adiabatic reaction system. This reaction is highly exothermic and heat generated is removed by recycle gas which limits the temperature rise in the MTG reactors to 420°C at the reactor outlet. Hot reactor effluent is cooled with waste heat being used to preheat recycle gas and to vaporise methanol feed to the DME reactor. 

At the time, the United States Office of Coal Research (later to become part of the Department of Energy) was very interested in the conversion of coal to liquid products. As many of you know, the United States has tremendous coal reserves. Since methanol had been made commercially from both natural gas and coal, it was recognized that the MTG reaction had the potential of providing the critical step in the first new synfuels process since the pioneering work in Germany some 50 to 60 years earlier. 

In the two decades since I.C.I. introduced the low-pressure methanol process others have gained increasing shares of the market. Major competitors include Lurgi, Mitsubishi Gas Chemicals and Haldor Topsoe. All have their own variations of the co-precipitated Cu-ZnO catalysts. Recently, Alberta Gas Chemicals has constructed several 1200 tonne/day plants one at Medicine Hat, Alberta and the other at Taranaki near the Synfuels methanol-to-gasoline plant in New Zealand. The Alberta Gas Chemicals plants use catalysts under licence. 

The methanol route is highly selective towards production of liquid transportation fuels. Only a very small amount of hydrocarbons beyond C are produced. The process uses a zeolite catalyst, developed by Mobil Research and Development Corp. (MRDC), USA. The final gasoline produced does not need further refining a nd attains the quality of unleaded premium gasoline. The world s first commercial synfuel plant for the production of gasoline from natural gas via methanol has been constructed in New Zealand and went successfully onstream in late 1985. The capacity is 570,000 tonnes of gasoline per year. The MTG reaction system is an adiabatic fixed bed version. 

With the methanol plants, the ASPEN steady state simulation was used to investigate the performance of the units with changing feedgas composition (H/C ratio and gas calorific valve) prior to startup. Since Synfuels processing fee for turning natural gas into gasoline is set by the yield obtained, the ASPEN simulator provides an important basis for fee determination under gas upset conditions. 

The Synposium marked the successful inauguration in October 1985 of the world s first commercial plant for production of gasoline from natural gas, based on the Mobil methanol-to-gasoline process. The plant is operated by the New Zealand Synthetic Fuels Corporation, of which Mobil is a shareholder. The Synposium was held at the University of Auckland and concluded with a tour of the synfuel gas-to-gasoline plant at Motunui, near New Plymouth. 

Mobil s Methanol-to-Gasoline (MTG) Process [1] is the first new synfuels process to be commercialized since the Fischer-Tropsch process of the 1920 s. The MTG process was chosen by New Zealand to convert natural gas from their extensive offshore Maui field into gasoline via methanol. Started up in late 1985, the plant at Motonui produces 14,500 BPD of premium gasoline, which is one third of New Zealand s total demand. 

Methanol To Gasoline) and MTS (Methanol To Synfuel), the production of fuels by oligomerization of olefins (Conversion of Olefins to Distillate, COD) or the synthesis of a wide range of hydrocarbons in Fischer-Tropsch processes. Some main features of these processes are outlined in the following sections. 

Another approach is the MTS process (Methanol To Synfuel) introduced by Lurgi GmbH, which is, in terms of process engineering, comparable to the MOGD process. However, primarily diesel is produced - besides a smaller... 

Guidebook for the Use of Synfuels in Electric Utility Combustion Systems - Volume 1 Methanol. Palo Alto, California Electric Power Research Institute, December 1983. AP-3348... 

FIGURE 3. Induction of revertants in Salmonella strain TA98 with increasing concentration of fraction 9 (basic, ether-soluble from Synfuel A) (A) and fraction 14 (neutrals/ methanol from Synfuel A) (B) without metabolic activation (A), with activation with an enzyme (S-9) prepared from rat livers induced with Aroclor 1254 (O) or with sodium phenobarbital ( ) (0.1% in drinking water). From Epler et al. reprinted by permission of Elsevier. 

The considerations for methanol production are valid also for manufacture of synfuels. The manufacture of synthetic gasoline by the Mobil MTG (Yurchak, 1988) or Topsoe TIGAS process (Topp-Joergensen, 1988) proceeds via methanol or dimethylether as intermediate. Diesel can be manufactured by the Fischer-Tropsch synthesis followed by hydrocracking of the wax product (v.d. Burgt et al., 1988). Slurry b Fischer-Tropsch processes for diesel may operate at a Hj/CO ratio slightly lower than for methanol synthesis (Dry, 1988). 

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