The Methanol Economy General Aspects

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Oil and natural gas, the main fossil fuels besides coal, are not only still our major energy sources and fuels but also the raw materials for a great variety of man-made materials and products. These range from gasoline and diesel oil to varied petrochemical and chemical products including synthetic materials, plastics, and pharmaceuticals. However, what Nature provided as a gift, formed over the course of eons, is being used up rather rapidly. The expanding world population (now exceeding 6 billion and probably reaching 8-10 billion in the 21st century), and the increasing standards of living and demands for energy in developing countries such as China and India, is putting increasing pressure on our diminishing fossil fuel resources and making them even more costly. Whereas coal reserves may last for another two or three centuries, readily accessible oil and gas reserves - even considering new discoveries, improved technologies, savings and unconventional resources (such as heavy oil deposits, oil shale, tar sand, methane hydrates, coalbed methane, etc.) - may not last much beyond the 21st century.

In order to satisfy mankind's ever-increasing energy needs, all feasible alternative and renewable energy sources must be considered and used. These include biomass, hydro and geothermal energy as well as the energy of the Sun, wind, waves, and tides of the seas. In practical reality, nuclear energy will above all have to be further developed and utilized. Our discussion here, however, is not dealing with the question of energy generation, which we believe mankind must and will solve (as in the final analysis majority our energies are derived from the Sun, an enormous and permanent energy source), but rather with the challenges of how to store and to best use energy. Most of our energy sources are used primarily to provide heat and electricity. Electricity is generally a good way to transport energy over relatively short distances when a suitable grid exists, but it is very difficult to store on a large scale (batteries for example are still inefficient and bulky). Besides finding new energy sources, it is therefore necessary to identify and develop new and efficient ways to store and distribute energy from whichever source it is derived.

One approach that has been proposed and widely discussed recently is the use of hydrogen. This would be generated eventually by water electrolysis using any available energy source and subsequently used as a clean fuel (the so-called "hydrogen economy"; see Chapter 9). Hydrogen is clean in its combustion, produc ing only water, although its generation is less clean if the requisite energy is derived from fossil fuels with their attendant polluting effects. As we have seen in Chapter 9, hydrogen has certain desirable attributes for energy storage and as a fuel but, due to its extreme volatility and explosive nature, many difficult issues will need to be resolved if it is to be used on a massive scale as an everyday energy source and fuel. As the lightest element, hydrogen has serious limitations in terms of its storage, transportation and deliverance of energy. The handling of volatile and potentially explosive hydrogen gas necessitates special conditions (high-pressure technology, cryogenic tanks, special materials to minimize diffusion and leakage, etc.), as well as strict adherence to extensive safety precautions, all of which makes hydrogen use very costly. In addition to these difficulties, there is a need to develop a currently non-existent infrastructure for the "hydrogen economy", and although this may eventually be developed it seems at present economically prohibitive. In any case, hydrogen per se will be unable to solve our continuing need for hydrocarbons and their products; for this, new synthetic methods must be developed that use existing natural resources more efficiently, or they may be synthesized from a non-fossil hydrocarbon source.

Today, the field of transportation is the major user of oil, with liquid hydrocarbon fuel products (gasoline, diesel oil) being the fuels of choice. These are easy and relatively safe to handle, to transport and to distribute, mainly because a vast infrastructure already exists. Consequently, the preferred alternative fuels for transportation should be comparable liquids.

Some years ago, one of the authors suggested a new, viable alternative approach of how to use more efficiently available oil and natural gas resources and, eventually, to free humankind from its dependence on fossil fuels. This approach is based on methanol, which forms the basis of the "Methanol Economy". Methanol (CH3OH), is the simplest, safest, and easiest to store and transport liquid oxygenated hydrocarbon. At present, it is prepared almost exclusively from synthesis gas (syn-gas, a mixture of CO and H2) obtained from the incomplete combustion of fossil fuels (mainly natural gas or coal). Methanol can also be prepared from biomass (wood, agricultural byproducts, municipal waste, etc.), but these play only a minor role. As discussed in Chapter 12, the production of methanol (and/or dimethyl ether) is also possible by the oxidative conversion of methane, avoiding the initial preparation of syn-gas, or by reductive hydrogenative conversion of CO2 (from industrial exhausts of fossil fuel burning power plants, cement plants, etc. and eventually the atmosphere itself). The hydrogen required (which is eventually generated from water using non-fossil fuel-based energy) is thus stored in the form of a safe and easily transportable liquid. The chemical recycling of excess CO2 would, at the same time, also help to mitigate climate changes caused in a significant part by the excessive burning of fossil fuels.

Methanol is an excellent fuel on its own right, with an octane number of 100, and it can be blended with gasoline as an oxygenated additive. Alternatively, methanol can be used in today's ICEs with only minor modifications. Methanol can also be used to generate electricity in fuel cells. This is achieved by first cat-alytically reforming methanol to H2 and CO; the H2, after separation from CO, is then fed into the fuel cell. Methanol can also react directly with air in the Direct Methanol Fuel Cell (DMFC), without the need for reforming. The DMFC greatly simplifies fuel cell technology, making it readily available to a wide range of applications such as portable electronic devices (e.g., cell phones, laptops), and soon also for motor scooters and cars, or for electricity generators and emergency back-up systems in areas of the world where electricity is still not available from a grid.

Another potentially significant application of the direct conversion of natural gas (methane) to methanol is in its ready and safe transportation when pipelines are neither feasible nor available. Today, LNG is transported across oceans under cryogenic conditions by using very large tankers (>200 000 tonnes). The LNG is unloaded at terminals and fed into pipelines to satisfy increasing needs, or to serve as a substitute for diminishing local natural gas sources. LNG is potentially hazardous, however, due perhaps to accidents or to acts of terrorism, and a single supertanker exploding close to high-density population area might have the devastating effect of a hydrogen bomb. Whilst hoping that such a situation will never occur, realistically we must be prepared to find alternative, safe methods of transporting natural gas. In this respect, its conversion to methanol is a feasible alternative. The direct conversion of natural gas to liquid methanol, in contrast to its prior conversion to syn-gas, can be achieved relatively easily and without building very large plants (see Chapter 12). Methanol produced close to the natural gas sources, can be easily transported.

Besides its use as energy storage and fuel, methanol also serves as a starting material for chemicals such as formaldehyde, acetic acid, and a wide variety of other products including polymers, paints, adhesives, construction materials, synthetic chemicals, pharmaceuticals, and single-cell proteins. Methanol can also be conveniently converted via a simple catalytic step to ethylene and/or propylene (the methanol-to-olefin, MTO, process), which serve as the building blocks in the production of synthetic hydrocarbons and related compounds (see Chapter 13). Thus, hydrocarbon fuels and products currently obtained from fossil fuels can be obtained from methanol, which is in turn produced by the chemical recycling of atmospheric CO2 (see Chapter 12). Methanol, therefore, has the ability to liberate mankind from its dependence on fossil fuels for transportation and hydrocarbon products, by allowing these to be produced via the hydrogenative recycling of CO2.

The concept of the "Methanol Economy" has broad advantages and possibilities. It is suggested that methanol be used as: (i) a convenient energy storage medium; (ii) a readily transported and dispensed fuel, including uses in methanol fuel cells; and (iii) as a feedstock for synthetic hydrocarbons and their products, including polymers and single-cell proteins (for animal feed and/or human consumption). The carbon source will eventually be the air, which is available to all on Earth, while the required energy will be obtained from alternative energy sources, including atomic energy.

It should be emphasized that there is no preference for any particular energy source in the production of methanol. All sources, including alternative sources and atomic energy can be used in the most economical, safe and environmentally acceptable ways. Methanol is a most convenient way in which to store and distribute energy, a suitable fuel in its own right, and a raw material in the production of synthetic hydrocarbons and their related compounds. The "Methanol Economy" offers a new way in which convenient and safe reversible energy storage and transportation can be achieved in the form of a simple, easily to handle liquid chemical - methanol. The ready conversion of methanol to synthetic hydrocarbons and their products will ensure that future generations will have access to the essential products and materials that today form an integral part of our life. At the same time, the "Methanol Economy", by recycling excess atmospheric CO2, will mitigate one of the major adverse effects on the Earth's climate caused by mankind, namely global warming.

The concept of the "Methanol Economy" has developed over a number of years, with the use of methanol as a fuel and gasoline additive only attracting interest during times of critical shortage. In fact, much more attention was (and is) paid to the use of ethanol obtained from agricultural sources, including fermenting corn (in the United States), sugar cane (in Brazil), or by bioconverting various other agricultural materials. The production and use of bioethanol as a transportation fuel was discussed in Chapter 8, and although this is feasible in some countries (e.g., Brazil, United States), it is able to satisfy only a small part of our overall transportation fuel requirements.

Although methanol and ethanol are chemically closely related (one and two carbon atom alcohols, respectively), when the public considers "alcohols" as transportation fuels they frequently fail to realize the significant differences between the two molecules. The fermentation of agricultural or natural products can be used to produce both alcohols, including "wood alcohol" (i.e., methanol) obtained from cellulose sources (primarily wood), though today methanol is produced mostly by synthetic processes. Industrial ethanol is produced by hydration of eth-ylene. Ethanol can also be prepared by fermentation, but whilst it represents a renewable, non-fossil fuel base, vast areas of suitable land are required to grow the sugar cane, corn, or wheat from which it is produced. The agricultural production of ethanol is also highly energy-demanding, and currently most of that energy comes from fossil fuels. Hence, the fundamental difference between the bioagri-cultural production of ethanol and of methanol is that the latter does not rely on agriculture or on diminishing fossil fuels.

In the interim, in the case of the methanol economy, still available natural gas (methane) can be efficiently converted to methanol by direct oxidative transformation, or from CO2 in the exhausts of fossil fuel-burning power plants. Eventually, it can also rely on the chemical conversion of atmospheric CO2, using hydrogen generated by the electrolysis of water (using any energy form, including alternative non-fossil fuel energies and atomic energy). In this way, mankind can produce methanol from chemical recycling of the CO2 of the air, which is accessible to all and, together with water, are inexhaustible resources on Earth.

The Olah group has long been involved in the study of various new aspects of methanol chemistry, beginning in the 1970s with the superacidic selective oxida tion of methane to methanol and the related condensation of methanol to higher hydrocarbons. During the 1980s, this was followed by the discovery of the bifunc-tional acid-base-catalyzed conversion of methanol or dimethyl ether to ethylene and/or propylene, and through them to both gasoline range aliphatic as well as aromatic hydrocarbons. These studies were conducted independently of the zeolite-catalyzed chemistry developed by Mobil (now ExxonMobil) and UOP for the conversion of syn-gas-based methanol to hydrocarbons (see Chapter 13).

As general realization has set in during recent years that our non-renewable fossil fuel resources are indeed diminishing, increasing efforts have been directed to finding solutions to counteract their depletion. A need for their more efficient and economic use is clear, and a variety of alternative energy sources and safer ways to use atomic energy, together with the proposed "hydrogen economy", have been pursued. It should be emphasized at this point, however, that in addition to finding better solutions to our overall energy needs in the post fossil fuel era, there will continue to be a lasting need for convenient and safe transportation fuels and for a multitude of hydrocarbon products that will necessitate the creation of vast quantities of synthetic hydrocarbons. Whilst the "hydrogen economy", as discussed, cannot itself fulfill these needs, it appears that the proposed broad concept of the "Methanol Economy" can indeed achieve this goal. In summary, the "Methanol Economy" encompasses:

• New and more efficient ways of producing methanol (and/or derived dimethyl ether) from still-existing natural gas sources by their oxidative conversion, without prior production of syn-gas.

• Utilization of the hydrogenative recycling of CO2 to methanol from industrial exhausts, but eventually from the air itself as the inexhaustible carbon source.

• The use of methanol and derived dimethyl ether as a convenient transportation fuel for both ICEs as well as in the new generation of fuel cells, including DMFC.

• The use of methanol as the raw material for producing ethylene and/or propylene to also provide the basis for synthetic hydrocarbons and their products.

The "Methanol Economy" offers a feasible means by which to liberate mankind from its dependence on diminishing oil and gas resources, while simultaneously utilizing and storing all sources of alternative energies (renewable and atomic). At the same time, by chemically recycling excess atmospheric CO2, one of the major man-made causes of climate change - global warming - will also be mitigated. These points are discussed in more detail in Chapters 11 to 14.

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