X-to-Liquids – Take Your Pick: X = gas, coal, biomass

There is a reason why oil is the premier fuel of the world economy. It’s a liquid and it can be transported, it can be stored, and it can be handled more easily than any other fuel.
Although worldwide there are approximately the same volumes of recoverable oil and natural gas reserves, the energy content of gas consumption is less than half that of oil consumption. This is because many gas reserves are stranded and far from consumption markets. Long pipelines are costly and risky, especially when more than one country is traversed.
An option that has been increasingly adopted to monetize stranded gas reserves is liquefied natural gas, or LNG. This involves deep refrigeration of natural gas, converting it to liquid and reducing its volume about 600 times, followed by its transport in special ships. Although the process is simple – there is not much required beyond refrigerating the gas – large investments are needed for the liquefaction and regasification terminals. In addition, security issues have led many cities to decline the installation of a nearby terminal. A less expensive solution is compressed natural gas, CNG, a process that involves simply pressurizing or even chilling the gas and transporting it in special ships, which act like floating pipelines. But CNG is only competitive for small distance and small volume transportation. The problem with both LNG and CNG is that at the receiving end gas is still gas, burdened by the same problems that have consistently kept its use lagging behind oil.
An alternative option that has received increasing attention is the so-called gas-to-liquids or GTL technology, which is a chemical transformation of natural gas into fuel products. In this case, not only is there monetization of stranded natural gas reserves after transportation to the consuming market, but value is added through transformation into high-quality petrochemical naphtha, premium diesel, specialty lubricants, and food grade paraffin. GTL technology opens up a whole new world of refining and refining routes.
Conventional GTL technology has three steps: reforming natural gas into synthesis gas (a mixture of hydrogen and carbon monoxide); conversion of the synthesis gas into liquid hydrocarbons and water; and product upgrading to adjust the final product properties.

A significant amount of fuel was produced by this process (using coal gasification instead of natural gas) in Germany before and during World War II, and in South Africa in response to the embargo imposed against its apartheid regime. Today, only a very small number of players possess commercial GTL plants: SASOL and PetroSA, both in South Africa, and Shell in Malaysia. Nevertheless, a big number of companies have been investing in the development of GTL technologies, and quite a number of new large-capacity projects have been announced, particularly in Qatar. Should all the new world-scale plants announced by Shell, SasolChevron, and ExxonMobil become reality, Qatar will become the GTL capital of the world.
Henrique S. Cerqueira is a senior chemical engineer and Eduardo Falabella Sousa-Aguiar is the GTL manager at PETROBRAS Research and Development Center in Rio de Janeiro, Brazil.
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