Alternatives to using Modified Hydrofluoric Acid at ExxonMobil

Sally Hayati Torrance Refinery Action Alliance July 10, 2015 Three viable alternative technologies to replace MHF are described. A fourth option would be for ExxonMobil to stop alkylation at the Torrance refinery and perform it elsewhere. Any of these options would be preferable to continuing the use of MHF in Torrance. Brief Introduction to Modified Hydrofluoric Acid (MHF) Exxon Mobils Torrance refinery has 250,000 lbs. of modified hydrofluoric acid (MHF) onsite for use in the alkylation unit. This unit produces alkylate, an additive used to boost the octane content of gasoline. Hydrofluoric acid (HF) is dangerous because of extreme toxicity and volatility. Upon release under refinery conditions of heat and pressure, it doesnt fall to the ground. Instead, the entire amount of released acid forms a dense toxic cloud that can drift for miles outside the refinery. MHF is a proprietary form of HF that is just as toxic. It was developed with the hope of eliminating cloud formation. Its developers and users, however, can only claim a 65% reduction in the amount of airborne acid. Thus, 35% becomes airborne when MHF is accidentally released (vs. 100% for HF). This 35% forms a (smaller) dense toxic cloud that can move with the air for miles outside the refinery. But with 250,000 lbs. of MHF onsite, the relative reduction in cloud size is small comfort for those who live within 10 miles of the refinery. A 1986 test showed that within two minutes of release, a 1,000-gallon (8,300 lb.) spill of HF produced a toxic cloud lethal to all exposed within a range of 5 miles, and immediately dangerous to life and health as far away as 7.5 miles. But the same results would be achieved by the accidental release of 2,860 gallons of MHF. The ExxonMobil refinery has more than ten times that amount of MHF onsite (and the Valero refinery in Wilmington has some comparable amount). ExxonMobil itself has confirmed the dangers of MHF in documents submitted to the EPA for the Risk Management Programs worst-case toxic release scenario, as shown in this map:

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Solid Acid Catalyst Method In the 1990s when it seemed that HF alkylation would be banned altogether, considerable research was performed on safer alkylation methods.1 One of the most promising was Solid Acid Catalyst (SAC) alkylation, which is safe for workers and the community and environmentally more benign than either acid. 2 Three primary solid acid alkylation processes were developed: CB&I Alkyclean, UOP Alkylene, and Exelus ExSact. Pilot plant tests indicate that the alkylate product from UOPs Alkylene has octane numbers and production costs comparable with traditional processes.3 In 1995 NIST funded a 3-year research project into solid acid catalysts for alkylation.4 Out of this effort, the ABB Lummus Global, Inc., Albemarle Corporation, and Neste Oil Corporation joint venture developed and optimized a solid acid alkylation demonstration plant that produced 10 barrels per day from 2002 to 2004 in Finland. As of 2005, the joint venture was in negotiations with several large energy companies to establish the first commercial-scale plant to produce upwards of 10,000 barrels per day. At least one contract was made for the resulting product, CB&Is Alkyclean, at Hyperion Refining in South Dakota, which planned to open a refinery processing 400,000-barrel-per-day of heavy crude from Canada.5 Expecting environmental opposition, the refinery chose SAC in an effort to portray their refinery as a clean operation. Yet there was stiff opposition from inhabitants of the rural area, and the refinery was never built. In 2013, the company announced a contract from Shandong Wonfull Petrochemical Group Co., Ltd. to provide processing engineering design for a first-of-a-kind solid acid alkylation unit to be located in China. The unit was to be capable of producing 100,000 tons per annum of alkylate and is scheduled for startup in early 2014. Theres no word on progress. According to Exelus, the octane obtained with ExSact alkylate is higher than that obtained by liquid catalysts.6 According to one Exelus study commissioned by a refiner, HF alkylation units are well-suited for revamping to ExSact alkylation.7 Several parts of the HF unit can continue their operation unchanged, reducing cost. Some equipment used for HF alkylation, like brick-lined vessels, acid containment and neutralization equipment, and refrigeration equipment are not necessary with SAC, reducing capital expenditures. Exelus has a discussion of the technical issues related to revamping of HF units on their website. The HF revamp option may save considerable capital over other alkylation options. Exelus estimates the capital cost of the revamp at about 50% of a grassroots ExSact unit and about 20% of a new sulfuric acid facility (including acid regeneration). In addition to eliminating the possibility of a catastrophic accident, SAC promises to deliver long-term economic benefits. Manufacturers claim that if all 112 domestic alkylation plants were retrofitted, the process could save approximately $580 million in processing costs per year.8 Yet, no US refinery has a SAC alkylation unit. This is typical for a new technology whose primary benefits are safety and environmental, even for those offering long-term savings but with initial conversion costs. Unless companies are forced to use such technologies, they generally chose not to. The incentive to adopt alternative catalysts went away when MHF and water suppression systems were demonstrated in 19949 and government agencies were lulled into complacency. Ironically, MHF is less deadly, not safe, and only 20% of HF units ever actually converted. Although SAC would effect long-term savings, upfront costs discourage retrofitting efforts. With few new refineries being built, SAC is unlikely to make headway without government mandates for inherently safer technology in existing refineries.

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Composite ionic liquid alkylation Composite ionic liquid alkylation (CILA) is an inherently safer technology that was developed by Shell and Chinese technologists. Since it is a liquid, existing alkylation unit retrofits are simplified. Ionic liquids (IL) are liquid salts: not salts dissolved in liquid, but salt that exists in the liquid phase. ILs are non-volatile (no cloud will form), low in toxicity, non-flammable, relatively inexpensive to manufacture, and far less corrosive than HF or H2SO4.10 They usually exist as liquids well below room temperature and up to a temperature as high as 200oC.11 One type of CILA called Ionikylation was proven in a pilot plant and then retrofitted into an existing 65,000-tonne/year H2SO4 alkylation unit in China by 2006. In 2013 a new 100,000-tonne/year CILA alkylation unit was successfully started up in China.12 The retrofit allegedly increased the yield of the process compared to sulfuric acid and increased the capacity of the process units by 40%, with attractive economics.13 The quality of the alkylate from Ionikylation compares favorably to alkylate from HF and H2SO4 units,14 as shown in the following table of pilot test results.15 CILA process reactions take place at ambient temperatures and moderate pressures, further reducing risk. The reactor used in Ionikylation is a commercial mixer that is much simpler and cheaper than the reactor used in the H2SO4 alkylation process. Ionikylation can be easily retrofitted to an existing H2SO4 or HF alkylation unit. Whatever technical challenges remain in the development of CILA can be easily rectified with the development of a market through government regulation eliminating HF.16 Sulfuric acid technologies Sulfuric acid (H2SO4) and hydrofluoric acid (HF) technologies have nearly equal shares of the alkylation market overall in the US. About 30% of alkylation units on the West Coast, Alaska, and Hawaii use HF technology, 50% on the Gulf Coast, and a full 71% in the Rocky Mountain region use HF. Only two of twenty California oil refineries17 use MHF (none use unmodified HF). Both are in the Greater South Bay: the Torrance ExxonMobil and Wilmington Valero refineries. Sulfuric acid (H2SO4) has a clear advantage over MHF from a safety and environmental standpoint. The American Petroleum Institute has issued a Recommended Practice specifically for HF alkylation units (API RP 751). This publication recommends that access to an HF alkylation unit be strictly limited due to the potential hazards of HF. No similar, specific safety document is required for sulfuric acid alkylation.18 HF and MHF are on the Department of Homeland Securitys (DHS) Chemical of Interest (COI) list for potential use by terrorists. H2SO4 is not on the list. HF is a toxic, volatile gas under refinery conditions, while H2SO4 is a toxic liquid. Therefore, H2SO4 is much easier to contain in the event of an accidental release. Tests conducted in 1991 by Quest Consultants, Inc. showed that there is virtually no potential for H2SO4 aerosol formation from an alkylation unit release. That means that released H2SO4 will not form a cloud that can move into neighborhoods adjacent to the refinery. Instead, it falls onto the ground as a liquid, with minimum vaporization posing a risk only to workers on the scene of the accident, not to the surrounding community. The primary safety and environmental disadvantage of H2SO4 is due to the larger amounts of fresh and spent acid that must be brought in and out compared to HF. If truck transport were used, far more

Figure 2. RON & MON are Motor Octane Numbers: the higher the better

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trucks would be required than for HF. Even so, the risk from trucks full of HF is significantly greater than from trucks full of H2SO4. There are no MHF mitigating measures available on the roads. But piping acid in from Carson, utilizing an existing pipeline, would all but eliminate this disadvantage, especially when combined with the use of on-site H2SO4 regeneration facilities.19 In 1994, Mobil won approval to use MHF at the Torrance refinery by claiming, to the Safety Advisors satisfaction, that MHF plus mitigation (safeguards) is no more dangerous than H2SO4 alkylation.20 Few experts agree with this unusual assessment. The decision reflected a heedless reliance on unverified proprietary claims shrouded in secrecy and on safeguards with inherent limitations and vulnerabilities. Why are refineries reluctant to give up the use of HF or MHF in densely populated areas? In 1990, Mobil refinery general manager Wyman Robb estimated that it would cost more than $100 million and take three to four years to convert to sulfuric acid.21 Yet it took a similar effort with possibly greater cost to research, develop, and install MHF and mandated mitigation measures. The answer is that HF technology is apparently the most profitable process for alkylate production.22 The acid consumption rate for HF alkylation is less than 1% of the rate for H2SO4. Its not community danger from increased acid transportation that concerns ExxonMobil, but increased material cost. Sulfuric acid alkylation also requires chilling equipment to maintain a low reaction temperature, which HF alkylation unit does not. And HF alkylation plants may process a wider range of feedstock mix and give somewhat higher-octane products than H2SO4 plants.23 Yet close to 50% of alkylation is done with H2SO4, which is clearly viable and competitive with HF. The HF benefit is real but marginal. Nevertheless, since the safety and environmental risks and costs of HF are externalities that enter into a cost-benefit analysis only as a minimal insurance cost, that marginal advantage is sufficient motivation for ExxonMobil to put hundreds of thousands of peoples lives at stake by choosing HF. 1 2000-08-28 A solid idea (and a liquid one), Oil & Gas Journal,

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21 1990-01-12 AQMD Urges Ban on Refinery Usage of Toxic Chemical : Safety: Staff members surprise and please Torrance city officials by suggesting a ban on hydrogen fluoride, Act 1410. JANET RAE-DUPREE, LA Times,