PTQ Q2 2022 Issue

produce MTBE or ETBE in the short term, while ethanol supply is scarce, and switch to isooctene or isooc- tane when enough ethanol is avail- able to satisfy E20 requirements, or when gasoline oxygen content limi- tations prevent blending of ethanol and ethers. Alkylation technologies In the US, where use of fuel ethers is banned due to concerns about contamination of water, alkylate forms around 13% of the gasoline pool, with ethanol content at 10%. Alkylate exhibits all of the ideal properties of premium gasoline, being free from sulphur, olefins, and aromatics, having a high octane number, and low vapour pressure. In US refining circles, it has earned the moniker ‘liquid gold’ due to its utility in correcting gasoline blend properties and composition. Alkylate has found limited use in the Indian gasoline pool to date. Blending to the standard 91 RON gasoline grade does not require alky- late, and traditional alkylation tech- nologies bring their own challenges. Both types of legacy alkylation tech- nology use strong liquid acid cata- lysts: hydrogen fluoride (HF) and sulphuric acid. HF alkylation was more popular in earlier years due to lower installed cost than the sulphu- ric acid process, with around half of alkylation units in the US using HF. However, concerns about the poten - tial risks from HF acid release and aerosol formation have swung the balance in favour of sulphuric acid alkylation in recent decades. Sulphuric acid is inherently less efficient as an alkylation catalyst, so large volumes of catalyst are required. Regeneration of the cat- alyst is carried out in a separate spent acid recovery unit, which generates flue gas with high SOx, NOx, and volatile organic com- pound (VOC) content. The spent acid regeneration unit, acid storage and handling facilities, and waste- water treatment add significantly to outside battery limit (OSBL) scope, making capital costs another barrier to alkylation adoption in India. Ionic liquid alkylation technol- ogy has recently been marketed as a cleaner, safer alternative to sulphuric

Mixed C feed

C ranate

Alcohol recycle

Make-up water methanol

Product separation


C (optional)


Alcohol recovery

Figure 6 A flexible process for ethers and Isooctene production

late product achieving higher quality in the absence of iso-butylene. KBR’s solid acid alkylation technology (K-SAAT) produces alkylate with 99 RON in this configuration. ETBE vs MTBE The choice between MTBE and ETBE production has generally been a question of economics and local policy. In markets without incentives for bio-components, the lower cost of methanol versus eth- anol favours MTBE. Renewable fuels policies in Europe have lat- terly favoured conversion to ETBE production, utilising bioethanol, and Japan began widespread use of ETBE in 2010 to meet its obligations under the Kyoto Protocol. ETBE can play a useful role in the Indian market by extending the octane contribution of bioethanol in ex-refinery gasoline. While the blending RON of ETBE (120) is lower than ethanol (~130), each litre of eth - anol can be converted to 2.4 litres of ETBE, providing a larger octane con- tribution to the gasoline pool. Water solubility of ETBE is lower than both MTBE and ethanol, improving its

storage properties to enable blending at the refinery and reducing reliance on ethanol blending downstream. In addition to these benefits, the blending RVP of ETBE is only four psi (28 kPa) versus a blending RVP of around 20 psi (138 kPa) for etha - nol. ETBE is, therefore, an excellent component to help meet future gas- oline standards and allow blend- ing of low-value naphtha streams into gasoline. A flexible solution Given the dynamics of the Indian gasoline market, refiners may prefer to hedge their bets by constructing a unit with product flexibility. KBR partners with Neste Engineering Solutions Oy to license NexEthers technology for combined ethers pro- duction and NexOctane for isooc- tene or isooctane production, while offering the flexibility to design for swing production of ethers and isooctene. Figure 6 illustrates the flexible process, which offers very high conversion, high availability, and easy operability. In the Indian market, a refiner may opt to install a flexible unit to

Figure 7 Alkylation technology catalysts

18 PTQQ 2 2022

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