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Science & Technology

December 3, 2007
Volume 85, Number 49
pp. 55-59

Methanol's Allure

Simplest alcohol shows promise as a feedstock and fuel

Jyllian Kemsley

Methanol is the lightest, simplest alcohol. Colorless and flammable, it is a somewhat poisonous, corrosive liquid with a slightly sweeter odor than ethanol. Once produced by collecting and distilling the vapor from burning wood, methanol is gaining ground as an alternative to petrochemical feedstocks and fuels—and it may provide an answer for what to do with excess CO2.

Future Fuel Daimler Chrysler's NECAR 5 used methanol to fuel a cross-country trip.

Methanol can be transformed into everything now made from oil and gas, says Nobel Laureate George A. Olah, a professor of chemistry and director of the Loker Hydrocarbon Research Institute at the University of Southern California. What's more, he adds, it's "a prime way to store, transport, and utilize energy."

Olah is arguably the U.S.'s biggest proponent of methanol as a feedstock and fuel. His book "Beyond Oil and Gas: The Methanol Economy" was published in 2006 (C&EN, Oct. 2, 2006, page 51). "I am not saying methanol is the only solution" to the world's energy problems, Olah emphasizes. "We should use everything that is feasible. But in this big mix, methanol has a significant role."

Yes, that's methanol, not ethanol. For all the focus on bioethanol in the U.S., ethanol as a fuel is problematic. The U.S. used about 20% of its corn crop to make 4.8 billion gal of ethanol in 2006. Even if more acreage is devoted to corn, that's a long way from the U.S. Department of Energy's goal of 60 billion gal by 2030. Ethanol derived from cellulosic materials such as prairie grass has additional potential, but that technology is still at an early stage and costs remain high.

Diverting corn from livestock feed to ethanol production has also already been blamed for rising food prices in the U.S. and Mexico. And then there's the question of environmental pollution from increased fertilizer and pesticide use as farmers try to improve corn yields (C&EN, Oct. 8, page 11; Envir. Sci. & Technol. 2007, 41, 7593).

Additionally, the ability to convert excess food stock to fuel production is a luxury not enjoyed by many other countries. China, for example, cannot afford to divert much food to fuel, yet its energy needs have risen such that the International Energy Agency expects China to overtake the U.S. and become the world's largest energy consumer by about 2010.

Meanwhile, as the price of oil hits $100 per barrel, chemical companies producing petroleum-based products are also feeling the crunch of higher costs and are looking for alternative chemical feedstocks (C&EN, Oct. 22, page 29).

All of this would seem to lay out a red carpet for methanol. On the feedstock side, products from methanol include synthetic gasoline, formaldehyde, acetic acid, olefins, and dimethyl ether (DME), which is touted as a clean-burning diesel substitute. Global methanol production capacity is currently about 12 billion gal per year.

As an automotive fuel, methanol initially looks unpromising—its energy content, 64,500 Btu per gal, is about half that of gasoline. The values for gasoline and ethanol are 124,800 Btu per gal and 76,500 Btu per gal, respectively. Also, methanol is toxic when ingested. Similar to ethanol, it is corrosive to current gas tank liners and pipeline seals and gaskets.

On the positive side, the costs to adapt current infrastructure to accommodate methanol would be similar to those for ethanol and far less onerous than developing an infrastructure to compress and transport hydrogen or liquefied natural gas. Methanol burns cleanly, producing CO2 but eliminating other products of gasoline combustion such as benzene and particulate emissions. Methanol is harder to ignite than gasoline and burns cooler, making it less of a fire hazard. It's also miscible in water, and would likely dilute and biodegrade in a spill.

As an automotive fuel, methanol is most commonly discussed in terms of M85 fuel, which has 85% methanol mixed with unleaded gasoline. Such a blend allows for cold-weather starting and has colored flames in case of fire. According to the California Energy Commission, M85 reduces total toxic air pollutants by 50% compared with gasoline alone.

M85 was used in California in a pilot program started in 1980 that eventually involved about 13,000 flexible-fuel vehicles. The program peaked in the early 1990s, then interest waned as methanol prices rose and producers focused on converting methanol to methyl tert-butyl ether (MTBE) as a fuel additive to reduce tailpipe emissions, says Gregory A. Dolan, vice president of the Methanol Institute. The flex-fuel program was terminated in 2005.

Loker Hydrocarbon Research Institute
Methanol Power A direct methanol fuel cell consumes methanol and oxygen to produce CO2, H2O, and electricity to power a fan.

Beyond California, methanol was the required fuel for the Indy Racing League (IRL) from the 1960s until 2006, when ethanol was phased in. The switch was a marketing move to take advantage of ethanol's growing reputation as a renewable fuel, says John Griffin, vice president of public relations for IRL. It was also a financial gain for the league, since the ethanol industry is now supplying fuel free of charge, whereas methanol had to be purchased.

For its part, China is on the verge of committing to methanol as an important alternative to petroleum fuel. Interfax-China reported in October that the nation should finalize state methanol fuel standards by mid-2008. Even without the standards in place, China will put 1 billion to 2 billion gal of methanol toward fuel use this year, Dolan says.

In addition to direct use as a fuel in engines, methanol can be used in fuel cells. In one type of methanol-charged fuel cell, the strategy is on-board generation of hydrogen through catalytic reforming. The hydrogen is then fed into a typical proton-exchange membrane fuel cell. In a demonstration project, fuel-cell-powered Daimler Chrysler's NECAR 5 made a trip from San Francisco to Washington, D.C., in 2002, the first attempt to drive a fuel-cell-powered car cross-country. The car had to be refueled about every 300 miles.

The direct methanol fuel cell (DMFC), developed by researchers at USC-Loker and California Institute of Technology's Jet Propulsion Laboratory, is another promising design. With a platinum-ruthenium catalyst at the anode and platinum at the cathode, the fuel cell overall consumes methanol and oxygen to produce CO2, H2O, and electricity.

DMFCs have been hampered by low efficiency levels relating to methanol's ability to permeate of the commercial Nafion membrane. However, USC-Loker researchers have improved efficiencies by developing a proprietary membrane made of polystyrene sulfonic acid cross-linked within a poly(vinylidene fluoride) matrix. DMFC technology is still considered too expensive to implement in vehicles but instead is being developed to power portable electronics. In October, Toshiba unveiled a DMFC-powered multimedia player that the company says runs for 10 hours on 10 mL of methanol.

Methanol is also considered promising as a fuel for generating electricity. In the Caribbean, Methanol Holdings (Trinidad) Ltd. (MHTL) is collaborating with the University of Trinidad & Tobago (UTT) on a project to use methanol derived from natural gas as a fuel for gas turbines. A demonstration pilot plant at MHTL's Point Lisas facility in Trinidad can generate up to 8.5 MW of power, enough to meet the electricity needs of two methanol plants at the site.

The goal of the project is to provide methanol as a fuel for electricity generation for other Caribbean islands. Delivering methanol by ship would be less costly than installing pipelines for or shipping liquefied natural gas (LNG), which needs to be stored in cryogenic compartments.

"LNG works for long distances and very large markets, but we believe methanol will be economic for the smaller markets typical in the Caribbean," says Haydn I. Furlonge, a professor in the Natural Gas Institute of the Americas at UTT.

With methanol's potential as a fuel established, the question then becomes how to make it. Historically, methanol has been produced by partially oxidizing coal or natural gas to produce synthesis gas (syngas), a mixture of H2, CO, and CO2. Those components can then be reacted to form methanol, with CO2 as a by-product.

The technology is well-developed and is being implemented on a massive scale in China to take advantage of the country's coal reserves. China Shenhua Energy Co. is the country's leading coal extraction company, and it has teamed up with several chemical and petrochemical companies to develop coal-to-methanol technology.

One of its partners is Dow Chemical, which is working with Shenhua on a feasibility study of an integrated coal-to-methanol-to-olefins facility in China's Shaanxi province. The plant would have on-site processing of its primary products to other chemicals and plastics, as well as a chlorine unit. About 3 million tons per year of methanol would be converted to 1 million metric tons per year of olefins, or about 10% of Dow's total ethylene and propylene production.

"It's proven technology but not previously applied at this scale," says Donald Chen, Dow's business director for hydrocarbons and energy in China and the Pacific region. "The whole process is a challenge because this is the first time we'll put all those elements together." The facility will be the biggest of its kind in the world when it is done, Chen adds, likely in five to seven years.

Although the route from natural gas to methanol is primarily steam reforming to produce syngas, other approaches are possible. These include methane bromination followed by hydrolysis, reacting methane with homogeneous transition-metal catalysts in sulfuric acid, direct oxidation of methane with oxygen or air, or reacting methane with CO2 in a process called dry reforming. Challenges of these processes include difficulty in handling bromine or sulfuric acid, and poor selectivity of direct oxidation reactions. Methanol can also be produced by converting biomass to syngas, but that faces cost and capacity issues similar to those for bioethanol production.

One of the downsides of producing methanol from coal or natural gas is that the processes produce CO2. Generally companies don't yet have a concrete plan for dealing with CO2 emissions. Says Dow's Chen, "CO2 is one of the most important topics we'll look at in the feasibility study" of the coal-to-methanol-to-olefins facility. He adds, "we'll do everything we can to find a solution, but what the outcome will be is difficult to say."

Aside from the usual options of funneling CO2 into oil wells or sequestering it underground, several groups are investigating using CO2 to make commodity chemicals, fuels, and materials (C&EN, April 30, page 11). USC's Olah has a particularly ambitious proposal: use it to make more methanol.

In one incarnation, CO2 would be captured from industrial flue gases at fossil-fuel-burning plants and cement factories (C&EN, Oct. 29, page 25). In another, engineers would find ways to absorb CO2 from the air, dialing back the atmospheric concentration of the greenhouse gas.

Olah proposes two CO2-to-methanol reactions. One is to hydrogenate CO2 with H2 produced from water electrolysis. The second path to methanol is to reduce CO2 electrochemically. Both pathways require energy, but that energy could come from a renewable source such as solar, wind, or hydroelectric power; hydrogen could also come from microbial fuel cells fed with biomass (C&EN, Nov. 26, page 45). Methanol would thus provide a means for storing energy from renewable sources for use at nighttime or during overcast or windless days.

Challenges to CO2-to-methanol conversion include purification of the CO2 from industrial plants as well as transportation between sites that produce CO2 and sites that produce hydrogen.

Although none of the companies contacted by C&EN revealed plans to divert CO2 into methanol production, they generally recognized the merits of the proposal. "It certainly is an exciting idea," says Rajeev Gautam of Honeywell subsidiary UOP, which is actively developing methanol-to-olefin processes to produce ethylene and propylene. CO2-to-methanol "is something that I think would have a big impact," Gautam adds.

With the exception of CO2-to-methanol, much of the technology surrounding methanol as a feedstock and fuel is proven and feasible, but it's expensive. As oil passes $100 per bbl, however, methanol technology will become more economically attractive. And as nations get closer to capping CO2 emissions, interest in chemical recycling of CO2 should also grow.

Methanol proponents are careful to say that it won't be the only answer to the world's need for petroleum alternatives. "The whole thing is that there is no one solution. We will have to adopt multiple solutions," says USC chemistry professor and Loker codirector G. K. Surya Prakash. "It's like a jigsaw puzzle. There's not one technology but a multitude of technologies, and methanol is one of them."

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2011 American Chemical Society

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