Ethanol: The Renewable Naphtha

FROM THE JUNE ISSUE: With existing capabilities, chemical coproducts represent a low-hanging fruit for the industry. Ethanol, in fact, is a better feedstock for some chemicals than oil-based sources.
By Luca Zullo | May 29, 2018

The commercial use of oil, which began in the second part of the nineteenth century, provided the world with new forms of energy, but also delivered a feedstock that made the modern chemical industry possible. The chemical industry predates the oil industry, but it is the development of industrial organic chemistry, made possible by abundant hydrocarbons, that made the modern chemical industry we know today. 

The impact of the chemical industry on society cannot be overstated. For example, only the incredibly rich would be able to afford anything more than occasional use of fabrics of vibrant and varied colors, as dyes previously were exclusively of vegetable and animal origin. 

The almost infinitely wide variety of materials, coatings, fibers and detergents available today, with their even more significant number of applications and astonishing performance, would have been unimaginable in the world before oil. Surprisingly, given all the diversity in appearance, properties and applications, virtually all of the organic chemical industry output comes from a handful of base chemicals—methane, ethylene, propylene, butylene, and the aromatics benzene, toluene and xylene. With the exception of methane, all these chemicals are derived from a crude oil fraction: naphtha.

Naphtha is one of the lighter fractions of oil and a precursor of gasoline. In fact, in the early days of the internal combustion engine, straight naphtha was used as a fuel. While some of these base chemicals can come from other sources, naphtha remains a critical feedstock for the chemical industry and in the oil value chain.

The chemical industry consumes less than 10 percent, on average, of a standard 42-gallon barrel of oil, yet it provides more than 40 percent of the overall commercial value of all barrel derivatives. The biofuel industry has long recognized that overall profitability can be improved by side streams and coproduction of higher-value and lower-volume products.

The ethanol industry should look at the naphtha model with interest as it searches for new growth opportunities. Ethanol is the perfect renewable naphtha. 

Chemical Feedstock
Ethanol, like naphtha, is mainly a fuel molecule with characteristics that make it an excellent chemical feedstock. It is reactive and produced in large volumes with well-understood and advantageous economics. Ethanol, unlike naphtha, is a pure substance. For chemical synthesis, pure substances have an advantage over mixtures like naphtha, as the desired chemistry might require fewer synthesis and separation steps. 

Ethanol chemistry is rich in possible reaction pathways and allows for the synthesis of a variety of products such as acetates, esters, ketones, fatty alcohols and many more with broad applications in several industries. Many of these products have no economically or technically viable fermentation synthesis route. Often, these chemicals also are drop-in replacements for molecules of broad market appeal that are currently derived from fossil resources. Drop-in replacements make it easier to manage the market risk and minimize adoption cost for the buyers.

These chemicals, which can be both a feedstock for other synthesis or used in end-user products, commonly command several hundred dollars per ton premiums over ethanol. Economics are important. The experience of the past several years have taught that competing with oil-derived products is challenging and that the market will not pay a premium for a product derived from a renewable resource. Competitiveness against incumbent petrochemical producers on a market basis is essential. 

This vision requires adequate technology with the right mixture of technical and economic performance. To extract such value from the spread between ethanol and chemicals, one needs a process technology that ensures high mass yield and selectivity with moderate capital costs. Heterogeneous catalysis, used in the petrochemical world, is that technology.

The high concentration of the fuel grade ethanol enables the design of compact reactors, as ethanol does not contain a significant volume of nonreactive dilutive materials. The relatively high purity of ethanol allows catalysys with all but the finickiest of catalysts with a small amount of purification and preconditioning.

The last but immensely beneficial characteristic of heterogeneous catalysis is the ease of scale-up. Once the laboratory work has demonstrated that a good catalyst is available, and the desired mass yield, selectivity and operational life are achieved, scale-ups by four or five times magnitude in a single step are possible. The chemical industry achieves such scale-up factors thanks to the maturity of understanding of the hydraulics and thermal characteristics of catalytic reactors.

As none of the operations used in these processes is new to the world, the time from research and development in the lab to industrial scale design can be greatly reduced. Time to market can be similarly short.

The benefits for the ethanol producers do not stop here. A catalytic process that uses ethanol as feedstock can literally be bolted onto the mill without the needs of any retrofit on the front end. No changes in the process are needed, no changes in quality and yield of DDGS, oil and other coproducts is risked. Once again, this incremental growth around a core process is straight out of the oil industry playbook. Some of the largest industrial complexes in the world sit on locations that were once modest lamp-oil refining operations. Looking at ethanol as a feedstock might even allow an increase in the grind rate for extra oil and protein, without relying on volatile and saturated markets for the disposal of additional ethanol.

Operationally, we have a literal light-switch upgrade—the day the catalytic process is ready to start up, the only change is the diversion of some ethanol from the load-out to the new process. No need to disrupt or in any way impact the existing operations, while the new process still benefits from the ethanol plant’s existing infrastructure in logistics, utilities and operational expertise. 

This vision has prompted Greenyug to develop an ethanol-to-ethyl acetate plant adjacent to the ADM corn processing plant in Columbus, Nebraska. The project is under construction. Ethyl acetate is a widely used, low-toxicity organic solvent used in a variety of industrial and consumer applications from wood varnishes to nail polish. It is obtained through petrochemical processes, but Greenyug and ADM will bring to market a biobased ethyl acetate in commercially significant quantities.

While tooling up for this start-up, Greenyug is only scratching the surface of what an ethanol-chemical industry built on top of the U.S. ethanol biorefining industry could do and become.

Author: Luca Zullo
Vice President of Business Development