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lunes, 2 de julio de 2018

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.
[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.

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