Alcohol-To-Fuel
Type of post: OVERVIEW.
Introduction
Bioethanol produced from fermentation of sugar
based crops is the major product of the biofuels industry [1]. But, ethanol is
not a “drop-in” solution and requires substantial changes in refining or
distribution infrastructure. The properties of this alcohol (an oxygenated
single molecule) are largely different than those of gasoline, diesel and jet
fuel blendstocks (mixtures of hydrocarbons), leading to problems in blends. Ethanol
can cause corrosion problems in transport pipelines that were designed to work
only with gasoline.
In the specific case of the aviation fuel, there
are stricter quality requirements than fuels used in road transport. Ethanol shows
low compatibility as a blendstock for aviation fuel because of its high
volatility and water absorption and low flash point and energy density. Butanol
is not as incompatible as ethanol, however, it still poses unacceptable safety
risks due to its low flash point and high volatility. [2,3]
In order to avoid the problems related to the
limits of alcohol use to hydrocarbon blending, the direct conversion of alcohol
into conventional fuels (alcohol-to-fuel technology) is being studied as an
alternative. Those hydrocarbons can be used as transportation fuels with the
current infrastructure. In addition, this application does not require fuel
grade alcohols, reducing distillation energy inputs. Renewable feedstock-derived
fuels can reduce the dependency of the transport industry on one single energy
source, avoiding the volatility of petroleum prices and reducing greenhouse gas
(GHG) emissions.
Process
To make drop-in alternative fuel from alcohols,
the differences in the physical and chemical properties between alcohols and
conventional fuel have to be minimized. The process includes three steps:
alcohol dehydration, oligomerization and hydrogenation. One advantage with those
steps is that they have been used on a commercially relevant scale. However,
the demonstration of the integrated process on biomass-derived intermediates is
still necessary. The following tables exemplify three Alcohol-To-Fuel
technologies in different development stages.
Ethanol-To-Gasoline
[4]
|
|
Feedstock
|
Ethanol.
|
Process
technology
|
Catalytic
conversion of ethyl alcohol to synthetic hydrocarbons occurs in gaseous phase
in two stages:
1) Strongly
endothermic reaction of alcohol decomposition which produces ethylene and
steam.
2) Complex
strongly exothermic reactions of synthesis of hydrocarbons from ethylene.
|
Products
|
- Gaseous
biohydrocarbons.
- Liquid
biohydrocarbons (<210ºC).
-
Aromatic biohydrocarbons (>210ºC).
|
Current
status
|
Production
at commercial scale in Bogumiłów, near Łódź (Poland).
Capacity:
22,500 metric tons of hydrocarbons per year.
|
Alcohol-To-Jet
(ATJ)
[5, 6, 7,
8]
|
|
Feedstock
|
Ethanol
and isobutanol.
Production
process: fermentation (Gevo Integrated Fermentation Technology, GIFT).
|
Process
technology
|
Three
steps:
1)
Dehydration.
2)
Oligomerization.
3) Hydrogenation.
|
Products
|
- Jet
fuel.
- Isooactane.
|
Current
status
|
- Gevo
has been producing ATJ fuel in its biorefinery at South Hampton Resources’
facility in Silsbee (Texas, USA) since 2011. The plant has an input capacity
of approximately 5-10 thousand gallons of isobutanol per month and produces
testing volumes for commercial airlines.
- In
October 2016, Gevo entered into a heads of agreement with Deutsche Lufthansa
AG to supply its ATJ from its first commercial hydrocarbons facility,
intended to be built in Luverne (Minnesota, USA). The terms of the agreement contemplate
Lufthansa purchasing up to 8 million gallons per year of ATJ from Gevo or up
to 40 million gallons over the 5 year life of the off-take agreement.
- Gevo
ATJ was used throughout O’Hare International Airport in Chicago on November
8, 2017 for Fly Green Day.
|
Ethanol-To-Jet
[9, 10]
|
|
Feedstock
|
Ethanol.
Production
process: LanzaTech’s gas fermentation, which uses feedstocks such as industrial off gas, biomass wastes and residues.
|
Process
technology
|
Three
steps:
1)
Dehydration.
2)
Oligomerization.
3) Hydrogenation.
|
Products
|
- Jet
fuel.
- 2,3-BDO.
|
Current
status
|
- LanzaTech
is preparing a design and engineering package for an ATJ production facility
implementing this pathway. The process has been selected for demonstration
scale project under PD2B3 (Award DE-EE0007966).
- The
design will be for a facility that can produce 3 million gallons per year of
ATJ blendstock and diesel.
|
Figure 1. A: Gevo ATJ process (extracted from [5])
/ B: Lanzatech/PNNL ATJ process (extracted from [9])
Regulation
In 2016, ASTM's International Committee approved
a revision of ASTM D7566 (Standard Specification for Aviation Turbine Fuel
Containing Synthesized Hydrocarbons) to include ATJ synthetic paraffinic
kerosene derived from renewable isobutanol. In April 2018, ASTM International
voted in favor of revising again the specification to increase the approved
blend levels of ATJ fuel with petro-based jet fuel from 30% to 50%. Also, it included
ethanol as an approved feedstock in Annex A5 in addition to isobutanol. These changes
has been recently published in the last edition of the standard: ASTM D7566 - 18.
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REFERENCES
[1] B. Kummamuru: “WBA Global Bioenergy Statistics 2017”. World Bioenergy Association.
[2] J. I. Hileman, et al.: “Near-Term Feasibility of Alternative
Jet Fuels”, RAND
Corporation, 2009.
[3] W.-C. Wang et al.: “Review of Biojet Fuel Conversion Technologies”. Technical Report
NREL/TP-5100-66291, July 2016.
[4] “Profile: Bogumiłów
Ethanol-To-Gasoline plant”. BioRefineries Blog, 22/11/2017.
[5] G. Johnston: “Alcohol to Jet - Isobutanol”. ICAO Seminar on Alternative Fuels,
February 2017.
[6] “Gevo
and Lufthansa sign agreement for commercial supply of renewable Alcohol-To-Jet
Fuel”. BioRefineries Blog, 8/9/2016.
[7] “On Fly Green Day, Eight Airlines Fly withGevo’s Jet Fuel from O’Hare”. Gevo press release, 8/11/2017.
[8] “Jet Fuel Derived from Ethanol Now
Eligible for Commercial Flights”. Gevo press release, 3/4/2018.
[9] S. Simpson: “A Hybrid Catalytic Route to Fuels
from Biomass Syngas”.
U.S. DOE’s BETO Project Peer Review, March 2017.
[10] “PNNL technology clears way for ethanol-derived
jet fuel”. PNNL
press release, June 2018.