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Originally appeared in: February 2013, pgs 75-77. Used with permission.

Clean Fuels Special Report T. Thom, Calumet Superior LLC, Superior, Wisconsin; R. Birkhoff and E. Moy, Badger Licensing LLC, Cambridge, Massachusetts; and E-M El-Malki, ExxonMobil Research and Engineering Co., Fairfax, Virginia Consider advanced technology to remove benzene from gasoline blending pool

Under present clean-fuel regulations, specifically Mobil 8,000 bpd. Prior to the acquisition by Calumet, this refinery Source Air Toxics II (MSAT II), US refiners must reduce the was managing the MSAT II benzene compliance with reform- benzene content in gasoline to 0.62 vol% on an average annual er feed precursor removal through a naphtha splitter installed basis. This rule went into effect Jan. 1, 2011, for large refiners; upstream of the reformer in 2010. In addition, this refinery small refiners received deferments until 2015. In Europe and purchased credits from other refineries within the organiza- many other countries, a 1 vol% maximum benzene level in tion’s network. The decision to install technology was made in gasoline is also in effect. Other regions are expected to adopt 2010. Initially, it was economically driven to counter the losses similar clean-fuel regulations. For refiners, the challenge is to from the reduced reformer feedrate. Later, the new unit facili- meet these tightening gasoline specifications for benzene cost- tated the sale of the refinery, as purchasing benzene credits effectively without significant octane loss. became a mute issue. In the decision-making process, octane losses were mostly weighed against necessary investments to Challenges increase hydrogen production due to losses via the reformer. Several approaches are available to reduce benzene levels in At this time, with the reformate-alkylation unit in full opera- finished gasoline. Naphtha reforming is the predominant refin- tion, this refinery easily met the 0.62 vol% specification with- ery benzene source. Accordingly, preventing the formation of out requiring credits. benzene in the reformer is accomplished by prefractionation of the naphtha feed by removing benzene precursors. How- New technology. The advanced reformate-alkylation process ever, for many refiners, prefractionation of the reformer feed catalytically converts benzene into high-octane alkyl-aromatic does not provide sufficient benzene reductions to achieve the blending components by reacting a benzene-rich stream with 0.62 vol% in the gasoline pool. Alternatively, converting the re- light olefins, such as ethylene or propylene.1,2 In a typical appli- former-produced benzene is done downstream of a reformate cation, the new process reduces benzene concentrations in re- splitter. Benzene containing the light-reformate fraction from formate by reacting benzene contained in a light-cut reformate this splitter is sent to a hydrogenation reactor where benzene is with refinery-grade propylene from a fluid catalytic cracking converted to cyclohexane. Both strategies incur octane loss and (FCC) unit over a proprietary zeolite catalyst. Typical ben- add extra burdens onto the hydrogen balance for the refinery. zene concentration in a light-cut reformate, produced by the A third approach is benzene extraction for the petrochemi- reformate splitter, ranges from 10 vol% to 30 vol%. Fig. 1 is a cal market. While petrochemical benzene can be an attractive simple flow diagram of the new reformate-alkylation process. product, significant investment is required to recover benzene Key features include: unless the refinery has existing facilities or spare capacity for • Fixed-bed catalyst technology. This advanced process such a process. It is very difficult to justify this investment on uses a fixed-bed, liquid-phase reactor with low utility require- a small scale. An alternative technology, reformate-aklyation process, can Light Propylene LPG reformate provide a low-cost solution for refiners to meet the benzene regulation without the octane loss and hydrogen debits associ- ated with other processing options.1 Reformate Reformate Mogas alkylation Calumet Superior Refinery Reformate The refinery in Superior, Wisconsin, was acquired by splitter Calumet Superior, LLC, in October 2011. At that time, the Stabilizer benzene-reduction project was in progress. The Superior re- Heavy reformate finery has a nominal crude capacity of 36,000 bpd, along with a semi-regenerative catalytic reforming unit with a capacity of Fig. 1. Process flow diagram of reformate-alkylation technology.

HYDROCARBON PROCESSING FEBRUARY 2013 Clean Fuels ments. The reactor can be a single bed (stage) or multiple beds, Besides benzene reduction, the process provides several depending on the benzene content of the feed and desired ben- advantages. The reaction of benzene with light olefin results in zene conversion. In revamp projects, it is possible to retrofit a volume swell, which largely depends on the benzene content existing tubular or fixed-bed reactors for the new application. of the feed and degree of benzene conversion. Also, an octane • Catalyst. The process uses a proprietary high-activity gain of 2 to 3 numbers of (R+M)/2 in the total reformate is zeolite catalyst with long cycle lengths. In addition, the catalyst typical. The advanced technology offers reformer flexibility, is regenerated ex-situ to further extend service life. since it allows refineries to process the full-range naphtha feed • Stabilization. Propane fed to the unit with propylene is in the reformer, thus increasing hydrogen production along removed from the reformate-alkylation product in a stabilizer. It with significant octane gain. can produce a propane product of HD-5 quality. Product from the reformate-alkylation unit is a light reformate with a reduced The Project Reid vapor pressure (Rvp). Before selecting the advanced reformate-alkylation tech- nology for the project, the licensor performed a pilot study 3 FCC propylene using reformate provided by the refinery. With the pilot-plant product, the refinery conducted blending studies to verify the Benzene-containing product properties and blending value. The refinery evalua- feedstock Propane tion matched the estimates provided by the licensor. A tech- nology license was executed in July 2010 and preparation be- 3 Reformate gan for the new process design. Since the refinery regularly 2-Stage once-through Stabilizer alkylation product reactor system

Fig. 2. Flow diagram of reformate-alkylation unit at Calumet’s Superior, Wisconsin refinery.

Fig. 3. Calumet’s Superior refinery reformate-alkylation unit was constructed in modules. Fig. 4. Side view of Calumet’s new reformate-alkylation unit.

HYDROCARBON PROCESSING FEBRUARY 2013 Article copyright ©2013 by Gulf Publishing Company. All rights reserved. Printed in U.S.A. Not to be distributed in electronic or printed form, or posted on a website, without express written permission of copyright holder. Clean Fuels sells its propylene to the US Gulf Coast market, a reactor con- an increase of about 4 points octane (R+M)/2 across the unit, figuration was selected to minimize propylene consumption which is equivalent to an increase of about 2 to 3 points on the and further optimize the process economics. Fig. 2 is a flow basis of total reformate. The new unit has enabled Calumet to diagram of the new reformate-alkylation unit. The recently installed reformer naphtha feed splitter was changed to operate as the reformate-product splitter Tighter gasoline specifications challenge how to for the new reformate-alkylation unit. Two new ben- zene alkylation reactors and a new product stabilizer handle benzene precursors in light-cut reformate with all associated equipment were installed. cost-effectively and maintain octane levels for Calumet had an aggressive timeline for the proj- final blending. ect execution with mechanical completion targeted for November 2011. Given the climatic conditions at the refinery location, the short seasonal construc- tion window was given full consideration. Due to close coop- improve the hydrogen management within the refinery. The eration with the licensor, collaboration with selected detailed Calumet Superior reformate-alkylation unit is designed to engineering contractors and utilization of selected modular process 5,500 bpd of feedstock. construction, Calumet was able to achieve mechanical com- pletion ahead of schedule and startup of the unit within 16 Benefits to the Superior refinery. The new reformate-alkyl- months.3 Long-delivery equipment were ordered shortly after ation unit was designed, constructed and commissioned on project kick-off. The licensor provided information that al- an aggressive project timeline. This project applied creative lowed Calumet to quickly submit applications for regulatory and forward-thinking execution strategies. The new unit had permits.3 Using modular design accelerated the construction an installation cost of approximately $19 million, within the and minimized the footprint of the new unit within the refin- original budget allocated at the early stages of the project. With ery. Six separate structural modules containing equipment, the new unit at the Superior refinery, Calumet complied with piping and instrumentation were delivered to the refinery to the MSAT II regulations for benzene. In addition, the project create a tri-level structure. The major vessels, such as alkyla- provided several economic benefits with a simple investment tion reactors, stabilizer and pumps, were placed on the perim- payback in approximately 20 months: eter of this tri-level structure, as shown in Figs. 3 and 4. • With the new technology, Calumet meets benzene com- pliance while allowing for full reformer operation. Recovering Unit operation. Initial plant commissioning activities began more hydrogen at the reformer has averted installing a hydro- in mid-November 2011 with assistance of operations and gen unit. technology experts from the technology licensor providers.2 • With the additional octane increase, Calumet can operate Catalyst was loaded November 9–10, and, after a subsequent the reformer at less severity to produce more gasoline volume. two-week period to set up rotational equipment and process • With the new unit, benzene compliance is achievable, as controls, the unit began operations on December 1, reach- shown in Fig. 5. The benzene level is consistently maintained ing steady-state operation within a matter of days. Operating below 1 wt%. When the product is blended in the gasoline and process control strategies were fine-tuned in the follow- pool, the Calumet refinery meets the 0.62 vol% maximum ing weeks. At the end of December, the startup was officially benzene level. completed. • The product is fully blendable into the gasoline pool. The operation of the new unit was straightforward and easy to control. Minimal staffing is required, one board/field op- NOTES 1 BenzOUT reformate-alkylation technology was developed by ExxonMobil erator per shift. The unit is operated without any online analy- Research and Engineering Co. (EMRE) and is licensed by Badger Licensing LLC. sis, and one daily set of samples. Performance exceeded design 2 In December 2009, EMRE and Badger agreed to jointly market BenzOUT tech- expectations, in terms of benzene conversion and propylene nology to third parties. Since then, licenses and related engineering services are provided exclusively through Badger. consumption. The product quality is consistent with projec- 3 tions made at the onset of the project. Calumet benefited from Badger Licensing LLC. 2.5 Timothy Thom is the engineering manager at the Calumet Superior refinery. He is responsible for turnaround planning and capital project management. 2.0 Ronald Birkhoff is director of business development for Badger Licensing LLC. He is responsible for commercialization of new process technologies. 1.5 Erik Moy is a technology manager at Badger Licensing LLC in Cambridge, 1.0 Massachusetts. He is responsible for the BenzOUT technology design and Benzene, wt % Benzene, development activities. 0.5 Dr. El-Mekki El-Malki is the licensing manager at ExxonMobil Research and Engineering Co., located in Fairfax, Virginia. He is responsible for licensing 0.0 ExxonMobil downstream technologies in the Middle East and Africa regions. In Time addition, he is the BenzOUT portfolio manager responsible for the marketing Fig. 5. Benzene concentration in treated reformate by the new technology. and licensing of EMRE’s reformate alkylation (BenzOUT) technology for benzene reduction in gasoline.

Article copyright ©2013 by Gulf Publishing Company. All rights reserved. Printed in U.S.A. Not to be distributed in electronic or printed form, or posted on a website, without express written permission of copyright holder. For more information on how BenzOUT™ technology can benefit your refinery, please contact:

Grant Donahoe El-Mekki El-Malki, Ph.D. Director - Business Development ExxonMobil Research and Engineering Badger Licensing LLC Technical Sales & Licensing One Financial Center or 3225 Gallows Rd. Room 3A1913 Boston MA 02111 Fairfax VA 22037 Direct: 617.748.7202 Direct: 703.846.5712 [email protected] [email protected]