Liquefaction Technology for Natural Gas (GTL)

Fig. 1 - GTL process flow

Our company is engaged in development of GTL (Gas-to-Liquids) technology, used to convert natural gas to liquid products. GTL is seen as a highly effective technology for enabling diversification of the primary energy mix. As Fig. 1 shows, GTL technology consists of three parts: a reforming reactor that converts natural gas into a mixture of carbon monoxide and hydrogen (syngas), a Fischer–Tropsch (FT) synthesis reactor for obtaining FT crude oil from the syngas, which consists of normal paraffin molecules; and a hydrogenation section that converts the FT crude oil into liquid fuels such as naphtha, kerosene, and diesel. Through these processes are manufactured synthetic liquid fuels such as GTL kerosene and GTL diesel.

With the help of a grant from the New Energy and Industrial Technology Development Organization (NEDO), we developed technologies for converting syngas (obtained by reforming natural gas) into paraffinic hydrocarbons via a high-performance Fischer-Tropsch (FT) reaction, which are then treated with a high-performance hydrogenation catalyst to manufacture high quality diesel fuel. In the drive to make the technology commercially viable, we joined the Nippon GTL Technology Research Association, an organization of six private-sector companies, and oversaw a successful run of 3,000 continuous hours at a demonstration plant on a scale of 500 barrels per day as part of a joint research project with the Japan Oil, Gas and Metals National Corporation (JOGMEC).

Microcrystalline zeolite
Commercial zeolite

Fig. 2 - Comparison of zeolite crystal sizes

To boost the efficiency of GTL fuel manufacturing, the hydrogenation section after the FT synthesis reactor must have a catalyst that can effectively crack the long-chain wax coming from the bottom of the separator tower without producing excess light gas byproducts. Normally, this hydrocracking catalyst is made using a material called zeolite. As the photograph shows, the microcrystalline zeolite developed by our company is unique in that the crystals are much smaller than those of other zeolites that were available at the time. This makes it possible to manufacture GTL fuels efficiently from long-chain molecules.

We have perfected a technology for mixing cracked diesel, obtained using our own hydrocracking catalyst, with hydrogenated diesel created by hydrotreating the diesel naturally found in FT crude oil, thereby producing GTL diesel with properties that meet JIS requirements.

Table 1 - Properties of GTL diesel (Example)

Commercial diesel (Example) GTL diesel JIS Grade 2 diesel standards
Sulfur content 7 ppm Less than 1 ppm 10 ppm or less
Cetane index 55 70 or higher 45 or higher
Pour point -15°C -17°C or lower -7.5°C or lower

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