TWO-STEP PRODUCTION OF 1,3-BUTADIENE FROM ETHANOL

A plant utilizing a two-step reaction process, which takes a 95% ethanol stream (by mass) and produces a 98% 1,3-butadiene stream, was designed for this project. The production goal for this plant was 200,000 tonnes of butadiene with the main motivation behind the project being the recent rise in butadiene prices. The process first passes ethanol through a catalytic dehydrogenation reactor to convert ethanol to acetaldehyde and hydrogen. A kinetic model was used to determine the reaction rates and operating conditions of the reactor. The acetaldehyde intermediate is further reacted with ethanol in a catalytic reactor to form butadiene. A hydrogen byproduct stream is also generated in this design and is purified for sale. This report provides a design and economic analysis for the production of butadiene on the Gulf Coast. Process flow sheets, energy and utility requirements, and equipment summaries are provided and analyzed. Process profitability is sensitive to the cost of both ethanol and butadiene. It is shown that the plant is very profitable for its expected 15-year lifespan with an expected internal rate of return of 40%, return on investment of 34%, and net present value of $172,000,000 (for a discount rate of 15%). The process becomes unprofitable if the price of ethanol increases to over $3.00/gallon. A combination of increased ethanol price and decreased butadiene price will also cause the plant to be unprofitable. Therefore, plant construction is only recommended given an acceptable price of ethanol and butadiene. This working paper is available at ScholarlyCommons: http://repository.upenn. edu/cbe_sdr/42 CBE 459 Senior Design Project: TWO-STEP PRODUCTION OF 1,3-BUTADIENE FROM ETHANOL By: Jonathan Burla, Ross Fehnel, Philip Louie, and Peter Terpeluk Presented To: Mr. Leonard Fabiano, Dr. Warren Seider, and Dr. Talid Sinno April 10, 2012 Department of Chemical and Biomolecular Engineering University of Pennsylvania School of Engineering & Applied Science Letter of Transmittal Burla, Fehnel, Louie, Terpeluk Mr. Leonard Fabiano University of Pennsylvania School of Engineering & Applied Science 220 S 33 Street Philadelphia, PA 19104 April 10, 2012 Dear Mr. Fabiano, We have analyzed a two-step process of converting ethanol to 1,3-butadiene. Enclosed is our solution to the design problem proposed by Mr. Bruce Vrana. Our plant design involves two reaction sections, both of which use heterogeneous catalysts in fixed bed reactors, and two separation sections to purify the products and recycle the unreacted feed. We have also designed a Dowtherm heating system for our process, which will supply heat to the reactor sections. This report provides details on the process equipment required and the potential profitability of the plant. The design determined a liquid feed flow rate of 155,000 lb/hr of ethanol and a production rate of 56,000 lb/hr of butadiene. Production was assumed to operate 24 hours a day for 330 days out of the year. The main capital investments for this project are the pressure swing adsorption unit, the reactors, and the multi-stage compressor, and the main variable investments are ethanol, steam, and natural gas. Overall, our process appears to be very profitable, with a return on investment of 34%. However, this analysis is very sensitive to both the price of ethanol and butadiene. Uncertainties lie in the cost for purification of hydrogen and the selectivities of the reactions, both of which were based on estimates from industry. Furthermore, no research has been done in recent years on the kinetics of the second reaction. Detailed kinetics would allow further optimization to be achieved.