**4. Bio-alcohol-based bio-jet fuel production technologies**

**Figure 5** shows current worldwide production and consumption trend of bio-jet fuel. Bio-ethanol is widely commercialized as sustainable source of energy for use in transportation with worldwide production of 104 million m3 and 80% of its utilization as transportation fuel. The USA and Brazil accounted for 51.8 and 2.77 million m3 production, respectively. Worldwide bio-jet fuel amounted to 30 billion m3 . On the other hand, Korean domestic petroleum-based aviation fuel products totaled 13% (20.66 million m3 ) in 2013, which is similar to gasoline products (13.5%) and 44% of light oil products (29.7%).

Possible raw material for ATJ process includes methanol, ethanol, and butanol. Such alcohol-based raw material is converted to bio-jet fuel via polymerization and upgrading technology. Among these alcohols, bio-ethanol utilization is promising in view of its current production and consumption and worldwide use. At present,

#### **Figure 5.** *Worldwide bio-ethanol production and consumption of aviation fuel.*

bio-ethanol is mixed to maximum 10~15% with gasoline. Although potential market of ethanol for mixing with gasoline seems limited for expansion, conversion to bio-jet fuel via bio-ethanol upgrading shows possibility of replacing existing petroleum-based aviation fuel.

For conversion of bio-ethanol to bio-jet fuel, physicochemical properties of bio-ethanol should be compatible with petroleum-based aviation fuel. The USA is utilizing advanced ATJ technology to make physicochemical properties of bio-ethanol compatible with those of existing petroleum-based fuel. More specifically, 99.5~99.9% of anhydrous ethanol is mixed with existing fuel or converted to bio-jet fuel. High purity ethanol is used as raw material in the process for upgrading physicochemical properties of bio-jet fuel. Such ATJ process is based on bio-ethanol for production of bio-jet fuel, and oxygen contents of bio-ethanol is removed by dehydration, polymerization for access of carbon atoms from existing petroleumbased aviation fuel, and hydrogenation reaction for optimization of physicochemical properties. **Figure 6** shows technical overview of ATJ process for production of bio-jet fuel from bio-ethanol [8].

The most efficient method of reducing carbon emission is low carbon bio-jet fuel, relevant technology to produce it and its commercialization. Many international airlines initiated small-scale projects, but so far economic viability has not been demonstrated, and possible remedy is under consideration. To accomplish such economic viability, international standards for carbon emission objective and related policy on the part of airlines have to be established as well as monetary

**Figure 6.**

*Technical overview of ATJ process for production of bio-jet fuel from bio-ethanol.*

incentive for bio-jet fuel utilization. To initiate economic drive for bio-jet fuel market, mass production-capable technology for bio-jet fuel production has to be developed. For carbon-neutral growth by 2050, international carbon emission reduction objective has been set by the ICAO with respect to greenhouse gas emission of 2005. For this, the CAEP has been established within the ICAO, and the ICAO is playing a central role to reduce aviation-induced greenhouse gas emission by intensive efforts. Development of aviation bio-jet fuel is taken as a pivotal means for greenhouse gas reduction, and many nations and international organizations are actively initiating aviation bio-jet fuel development. The ICAO 38th general meeting resolution approved aviation bio-jet fuel as vitally important intermediate to longterm means of greenhouse gas reduction, thus establishing fundamental frame of reference. More specifically, possibility of sustainable drop-in bio-jet fuel technology and related long-term policy as well as monetary incentive is also emphasized. Furthermore, IATA announced that sustainable and renewable energy utilization is the most reliable means to achieve established objective of greenhouse gas reduction and requested 6% replacement of aviation fuel with renewable energy by 2020. Bio-fuel is regarded as efficient and economical means of greenhouse gas reduction, energy security, new source of income, and market development for farm products in rural areas. Therefore, bio-fuel drive is supported as a national policy. Bio-fuel is supported by national policy in many nations via budget support (bio-fuel producers, vendors, and users are exempt from taxation or subsidy is given), minimum mixing proportion regulation, and import duty levied on foreign bio-fuel for wide distribution of bio-fuel. Altogether, worldwide monetary subsidy for bio-fuel totaled 20 billion US dollars in 2009 which was supported by US and EU nations. The Korean government subsidy will increase by 4.5 billion KRW every year during 2010~2020. This will be augmented by 8.5 billion KRW during 2021~2035.

To convert ordinary alcohol to fundamental aviation fuel element of hydrocarbon, oxygen contents have to be removed by dehydration via catalytic upgrading process. Alumina, transition metal oxides, and zeolite derivatives of SAPO, H-ZSM-5, and heterogeneous acid catalyst 0.5%La-2%P/H-ZSM-5 with acid sites [9]. Conversion rate was close to 100% at 250°C. Selectivity of ethylene was nearly 99.9% which was obtained by removal of oxygen via dehydration [10]. Such ethylene is converted to another reaction intermediate of alpha-olefin by polymerization called oligomerization. This is approximately equivalent to existing aviation fuel compound and intended to increase distribution of carbons. Candidate catalysts include Ziegler-Natta-based, homogeneous chromium-diphosphine-based, and heterogeneous zeolite-based catalysts. Oligomerization reaction took place at 90~110°C and 89 bar, where alpha-olefin with C4~C20 carbon numbers was synthesized

*Recent Application of Bio-Alcohol: Bio-Jet Fuel DOI: http://dx.doi.org/10.5772/intechopen.89719*

with 96~97% of yield. Commercial oligomerization reaction involves 200°C and 250 bar with relatively wide range of carbon distribution of 5% C4, 50% C6~C10, 30% C12~C14, and 12% C16~C18 [11]. Such wide range of carbon numbers enables separation by selective distillation to light oil and aviation fuel. Hydrocarbons with low carbon numbers of C4~C8 separated by selective distillation process are reintroduced into oligomerization process and further synthesized into hydrocarbons with relatively high carbon numbers. Existing petroleum-based aviation fuel consists of hydrocarbons with C6~C16 range of high carbon numbers which require upgrading process. Such upgrading process necessitates hydrogenation reaction under hydrogen atmosphere and 370°C, WHSV of 3 h<sup>−</sup><sup>1</sup> , using 5% Pd/C or 5% Pt/C catalysts [12, 13].
