An Overview of the Global Market, Fleet, and Components in the Field of Aviation Gasoline

Abstract

Aviation gasoline is a fuel for spark-ignition piston internal combustion engines, which are usually used in light aircraft (small aviation and general aviation). This technique is widely used for regional and interregional transportation, for the initial training and retraining of aviation staff, for private use, for agricultural purposes, for the development of aviation sports and tourism, and for combat and rescue operations. This article gives some estimates of the production and consumption of aviation gasoline in the EU, North and South America, Asia–Pacific, Africa, and CIS countries. Export possibilities and the reliance on import within different regions are analyzed. Economic indicators for aviation gasoline are calculated by assessing the share of its production in the GDP and per capita consumption. In the context of the transition to unleaded aviation gasoline, the structure of the piston aviation fleet and its readiness for the transition are considered. The paper also analyzes the following existing components of unleaded aviation gasoline: technical capabilities and promising components.

1. Introduction

Aviation gasoline is a class of petroleum fuels, the characteristics of which are subject to increased requirements due to the special conditions of their application. To ensure reliable, uninterrupted engine operation, aviation gasoline must have high chemical and phase stability, optimum vaporizability, high detonation resistance, and compatibility with fuel system materials [1]. Aviation gasoline is distinct from automotive gasoline due to its enhanced antiknock properties, which are traditionally achieved using tetraethyl lead (TEL) [2]. For jet fuel, the structural characteristics of a turbojet engine require the fuel to have a high energy density, high temperature oxidation stability, and high combustion efficiency. Improved low temperature properties are also required. There are no detonation resistance requirements for jet fuel [3]. Therefore, kerosene fraction has been widely used as jet fuel due to its higher density compared with gasoline, better low-temperature properties, and improved combustion efficiency compared with diesel. Jet fuel cannot be substituted with gasoline at high altitudes due to the high pressure of its vapors, which causes the fuel to boil as the pressure decreases.

The main peak of piston aircraft utilization was in the first half of the twentieth century. At that time, the main research on the development of aviation gasoline was carried out. Both in the USSR and abroad, several grades of aviation gasoline were developed, differing in some characteristics and intended for different operating conditions. However, due to the gradual replacement of piston aircraft with jet aircraft, the range of grades was reduced over time [4]. Currently, the global market of aviation gasoline is represented with the following grades:

• Avgas 100LL (Low Lead)—the most universal and widespread aviation gasoline grade in the world in terms of production and consumption, which is approved for use in almost all piston aircrafts. Requirements for this fuel grade are set in the specifications ASTM D910 and UK DEF STAN 91-90. There is also a more environmentally friendly modification of Avgas 100LL—Avgas 100VLL (Very Low Lead)—for which the maximum lead content is set to 0.45 g Pb/L (from 0.56 g Pb/L for Avgas 100LL) [5].
• B-91/115—a grade developed in the USSR, produced according to the Russian standard GOST 1012 or Polish specification WT-06/OBR PR/PD/60 [6]; it is mainly used in Russia and in the CIS for aircrafts equipped with Russian engines (ASH-62ir, AI-26V, M-14B, M-14P and M-14V-26); it is also allowed on most engines produced by Continental and Lycoming. It differs from Avgas 100LL in its lower antiknock resistance and less stringent lead content standard.

The negative impact of lead on human health has been studied in detail in a number of works [7,8,9]; in particular, some have investigated the effect on children living within 500 m of airports [10,11]. Thus, the reformulation of the composition of gasoline is an issue that is quite essential. Some studies suggest replacing aviation gasoline with aviation kerosene [12]; however, it is shown that kerosene is not fully burned and may lead to spontaneous combuction, which indicates the limitations of using kerosene in the spark-ignition engines. To improve the properties of gasoline, alcohols can be used to improve the completeness of combustion and reduce toxic emissions, such as n-butanol [13], n-pentanol [14], or ethanol [15]. It should be noted, however, that using such gasoline increases fuel consumption and its hygroscopicity. Thus, the main directions of research in the field of aviation gasoline are aimed at eliminating the use of TEL in their composition within the framework of the EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative. Research is under way to develop new unleaded aviation gasolines, and new piston aircraft engines are being designed so that there is potential for them to operate on such fuels. In 2023, the U.S. Environmental Protection Agency is expected to publish a final lead hazard bill [16], at which time a legislative phase-out of leaded gasoline will be initiated. The standard process for a transition takes approximately 7–8 years, so it is likely to be implemented in 2030 [17].

The Federal Aviation Administration announced the approval of unleaded aviation gasoline grade G100UL for all spark-ignition aircraft engines starting September 1, 2022 [18]. Earlier in June 2021, this grade was only allowed for low-compression ratio piston engines. The use of unleaded aviation gasoline for all engines was approved after 12 years of testing. GAMI elected to use the existing and approved STC pathway to obtain approval instead of ASTM specifications. The possibility of using unleaded aviation gasoline in piston engines is also shown in papers [19]. Thus, a key difference of the aviation gasoline of the future will be the absence of TEL in its composition. Currently, several grades of unleaded aviation gasoline have already been actively used:

• UL82 and UL87—unleaded aviation gasoline, designed for engines with a low-compression ratio. Requirements are regulated according to ASTM D6227.
• UL91 and UL94—the most researched and widely used unleaded grades of aviation gasoline that were developed to replace Avgas 100LL and have been approved for more than 90% of the fleet. The standards are established according to the ASTM D7547 standard.
• UL100 and UL 102—promising grades of aviation gasoline designed to replace Avgas 100LL. The standards for test gasoline blends are established in the specifications ASTM D7960 and ASTM D7719.

The aviation gasoline industry remains one of the furthest away from decarbonization, as there is still partial dependence on the use of lead to improve antiknock properties. The introduction of new technologies in general aviation requires thorough research, which slows down the implementation of ideas into reality. In civil aviation, there are noticeable decarbonization trends observed wherein sustainable aviation fuel (SAF), electricity, and hydrogen are being adopted [20]. The most progress has been made in the production of kerosene surrogates, which can be used in a blend with petroleum fuel as per jet fuel standards ASTM D1655, Def Stan 91–91. The usage of drop-in fuels is considered a temporary solution for facilitating the shift from conventional resources to net-zero technology.

Hydrogen and electricity require the creation of a completely new infrastructure for aviation, as well as significant modifications to the engine and fuel equipment of the aircraft—all of which require additional time. Hydrogen aviation is the closest to being introduced into passenger transportation [21], with one of the closest marketing statements coming from the Australian company Skytrans, which intends to launch hydrogen air transportation as early as 2026 [22]. Electrification is a more complex solution for short-haul aviation, but no less promising due to fewer iterations to obtain clean energy. In this part, we can highlight the NASA report [23], according to which demonstration flights are planned for 2023–2025. Decarbonization affects general aviation to a lesser extent through the replacement of fuels with sustainable ones, due to the high requirements for their properties, but it affects it through the substitution of piston engines to jet engines.

To evaluate the prospects of the aviation gasoline market, the purpose of this study is to analyze the changes that have occurred in the piston aviation industry over the last 10 years in relation to the following tasks:

• To assess the aviation gasoline market globally and in key regions according to consumers/producers, as well as the relation to economic indicators (presented in Section 3.1 and Section 3.2).
• Evaluate the state of the fleet: the number and types of aircraft and its development prospects (described in Section 3.3).
• Analyze aviation gasoline key components (presented in Section 3.4).

2. Methodology

The study presents four subsections, of which the selection of information for each has its own characteristics. For Section 3.1, it was necessary to analyze the market, which was done with the help of open government sources that collect statistical information. In the case of the United States, data from the U.S. Energy Information Administration [24]; Canada—Canadian Center for Energy Information [25]; and the European Union—Eurostat [26] were used. For other regions and countries, data were used from the United Nations [27], which collected information in cooperation with industry organizations and national governments. Data for the Russian market were obtained by analyzing the number of piston aircraft, their consumption, and flight hours as part of a previously defended dissertation on the subject [28]. In the case of countries for which very few statistics are available, a gray literature search was conducted to gain a general understanding of the aviation fuel situation in that country.

In order to assess the economic indicators in Section 3.2, it is necessary to estimate the cost of aviation fuel in the selected regions. The cost of aviation gasoline for the European Union and the United States [29,30] is a data set for which the estimated deviation and dispersion have been calculated. Because not every country has a data set, the average price reported in transactions or by manufacturers was used for other regions [31,32]. The calculation of the economic indices, i.e., aviation gasoline consumption per capita and the share of fuel production in GDP, was based on the World Bank’s GDP data for 2022, the population of the USA, Canada [33,34,35], Mexico, and other countries [36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55].

Section 3.3 is based on data from the Federal Aviation Administration (FAA) and the General Aviation Manufacturers Association (GAMA). The study of aviation gasoline composition is based on patents and articles issued by fuel producers and is presented in Section 3.4. The search and selection of literature for this section was carried out using sources in the period 1999–2023, articles—using the Web of Science, Google Scholar, SAE, and articles in Russian—e-library electronic library, and patents—using Patentscope and the European Patent Office. In addition, the work examined the studies of organizations such as the Coordinating Research Council (CRC) and doctoral theses from research institutes found from university websites and Google searches. The search terms included the following: “aviation gasoline”, “unleaded aviation gasoline”, “aviation gasoline production”, “aviation gasoline technology”, and in the case of a search for a specific country, its name.

One should also note the assumptions made in this article:

• According to market analysis, not all countries publish open information about the aviation gasoline market; for such regions as the APR (namely China) and some African countries, UN information is not available or may be unreliable.
• Using the average cost of aviation gasoline allows for only a rough estimate of the level of revenue from fuel sales.
• Technology is also evaluated only through public information found in patents and articles; the actual components may be slightly different.

3. Results and Discussions

3.1. Aviation Gasoline Market

3.1.1. Global Aviation Gasoline Market

As of 2022, the global aviation gasoline market is estimated to be over 600,000 tons/year or 224 million gallons/year. The annual growth rate was 0.1% between 2010 and 2020, but in general, the overall demand for aviation gasoline is projected to decline by 0.6% through 2043 [56]. Global aviation gasoline production, consumption, exports, and imports are summarized in Figure 1 [24,25,26,27,57].

The leading positions in both the production and consumption of aviation gasoline are held by North American countries—the United States and Canada. Together they account for more than 70% of the global production and more than 60% of the global consumption of aviation gasoline. Among European countries, the Netherlands and Poland hold the leading positions in aviation gasoline production, and France and Great Britain are the leading countries in its consumption. However, most of the gasoline produced by European countries is exported, with the total volume of aviation gasoline exports accounting for more than 50% of global exports (including exports within the European Union).

Australia is a major actor in the Asia–Pacific region, and Brazil is a major participant in South America—both of which have sufficiently powerful complexes for the production of aviation gasoline to fully satisfy their own fuel needs. The African region lacks its own production, so importing is the only way to provide fuel. The largest importers of aviation gasoline are Ghana, Zimbabwe, and South Africa. Let us consider the market of each region separately.

3.1.2. The European Aviation Gasoline Market

The dynamics of aviation gasoline consumption and production volumes in the European domestic market is presented in Figure 2. Over the last 8 years, aviation gasoline consumption in Europe has decreased by almost 17% (from 83.8 to 70.3 thousand tons/year) and has stabilized at around 73 thousand tons/year over the last few years, barring the 2020 crisis. The main consumers of aviation gasoline in Europe are France, Great Britain, and Germany, which account for more than 55% of total European consumption. The main producers of aviation gasoline in Europe are the Netherlands, Poland, and France. They account for more than 90% of the European region’s production volume.

Statistics on exports and imports in the European Union are presented in Figure 3. The leading positions in exports among European countries are occupied by the Netherlands, Poland, and France. The share of the Netherlands is more than 50% of the total export of aviation gasoline in Europe, and the total of the three cited states is more than 95%.

The leading countries in terms of aviation gasoline imports are France, the United Kingdom, and Germany (more than 65% of the total imports of aviation gasoline in Europe). Total imports in Europe are decreasing in contrast to exports, despite the fact that in the period before the pandemic, the behavior of imports and exports was approximately the same. The largest producers of both leaded and unleaded grades of aviation gasoline are shown in

Table 1. The Major Importers and Exporters of Aviation Gasoline in Europe.

Company	AVGAS Grade|Standard	Country of Import
Shell (London, UK)	100LL|ASTM D910 and DEF STAN 91-90	North and South America, EU, Asia–Pacific
TotalEnergies (Paris, France)	UL91|ASTM D7547 and DEF STAN 91-90 100LL|ASTM D910 and DEF STAN 91-90	EU
Vitol Group (Rotterdam, The Netherlands)	100LL|ASTM D910 and DEF STAN 91-90	EU, Asia–Pacific, North America, Africa
BP (London, UK)	UL91|ASTM D7547 and DEF STAN 91-90 100LL|ASTM D910 and DEF STAN 91-90	EU, Asia–Pacific, North and South America, Africa
Repsol (Madrid, Spain)	100LL|ASTM D910	EU, Asia–Pacific, North and South America, Africa
Warter Aviation (Plock, Poland)	UL91|ASTM D7547 and DEF STAN 91-90 100LL|WT-09/OBR PR/PD/48 B-91/115|GOST 1012-72 and WT-06/OBR PR/PD/60	EU, CIS
Hjelmco Oil (Sollentuna, Sweden)	91/96UL|ASTM D7547 mod. 100LL ASTM D910 and DEF STAN 91-90	Sweden, Japan

.

3.1.3. The North American Aviation Gasoline Market

The dynamics of aviation gasoline consumption and production volumes in the North American domestic market are shown in Figure 4. Over the last decade, the volume of aviation gasoline production and consumption in North America decreased from 559 to 504 and from 604 to 557 thousand tons per year, respectively. The USA and Canada are undisputed leaders in both the consumption and production of aviation gasoline. They account for more than 94% of the North American region’s consumption and 100% of its production.

The dynamics of export and import volumes of aviation gasoline in North America are presented in Figure 5. There is no information on the amount of aviation gasoline exported from the United States on the official website of the Department of Energy. When calculating the quantity of exports through current-period balances, imports, production, and consumption, the value of exports appears insignificant. Over 2013–2021, gasoline imports to the United States (a key importer) increased due to consumption growing faster than production.

The largest producers of aviation gasoline, as well as prospective importer companies (mostly European) in North America, are presented in

Table 2. The Major Importers and Exporters of Aviation Gasoline in North America.

Company	Avgas Grade|Standard	Country of Import
ConocoPhillips (Houston, TX, USA)	100LL|ASTM D910	North America
ExxonMobil (Irving TX, USA)	100LL|ASTM D910	North and South America, EU, Asia–Pacific, Africa
Phillips66 (Houston, TX, USA)	100LL|ASTM D910	North America
Shell (London, UK)	100LL|ASTM D910 and DEF STAN 91-90	North and South America, EU, Asia–Pacific
Vitol Group (Rotterdam, The Netherlands)	100LL|ASTM D910 and DEF STAN 91-90	EU, Asia–Pacific, North America, Africa
BP (London, UK)	UL91|ASTM D7547 and DEF STAN 91-90 100LL|ASTM D910 and DEF STAN 91-90	EU, Asia–Pacific, North and South America, Africa
Repsol (Madrid, Spain)	100LL|ASTM D910	EU, Asia–Pacific, North and South America, Africa
Swift Fuels (West Lafayette, IN, USA)	UL94|ASTM D7547	USA

.

3.1.4. The South American Aviation Gasoline Market

The dynamics of the aviation gasoline consumption and production volumes in the South American domestic market are shown in Figure 6. Between 2011 and 2018, consumption was reduced from 109 thousand tons to 56 thousand tons. Production had a similar correlation, falling from 90 thousand tons to 21 thousand tons over the same period. Brazil and Colombia are leaders in both the consumption and production of aviation gasoline, accounting for more than 60% of the region’s consumption and 80% of its production. However, since 2019, Brazil has ceased production as a result of refinery closures [58], and the country has shifted to dependence on imports.

The only country exporting aviation gasoline is Argentina, with an export volume equal to 1 thousand tons in 2020. The dynamics of import volumes and its structure by country is presented in Figure 7. The increased import volume in 2019 is due to the aforementioned closure of refinery in Brazil. In addition to Brazil, Argentina imports fuel, as do Ecuador, Paraguay, Chile, and Uruguay. It is possible that Argentina may have also exported fuel that was previously imported.

3.1.5. The Aviation Gasoline Market of the Asia–Pacific Region

Let us consider the market of the Asia–Pacific region, of which the largest and most economically developed country is China. There is no publicly available information on the production and consumption of aviation gasoline in China; therefore, only statements on consumption and production from news sources are considered below.

The volume of aviation gasoline consumption in China was estimated at 40 thousand tons including imports. The largest producer of aviation gasoline is Lanzhou Petrochemical. In 2015, the volume of aviation gasoline production at its facilities was estimated at 20 thousand tons [59]. Another producer is Changsha Tonglian Aviation Technology Co., Ltd. (Changchun, China), whose production capacity is estimated at 1.5 thousand tons per year. Until 2015, China produced aviation gasoline of its own grades RH-75, RH-95/130, and RH-100/130, according to national specifications. In 2015, the two companies Dongying Huaya Guolian Aviation Fuel Co., Ltd. (Shandong Sheng, China) and Guanghan Tianzhou Aviation Engine Fuel Technology Co., Ltd. (Guanghan, China) launched their own production of 100LL grade gasoline.

China has a government program to gradually reduce the consumption of leaded gasoline and replace it with unleaded gasoline grades. Since 2015, the state petrochemical corporation China Petroleum & Chemical Corporation has started the production of UL91 unleaded aviation gasoline and received approval from the Chinese Civil Aviation Certification Center for its use on some aircraft models. As of 2019, Sichuan Tianzhou General Aviation Technology Co., Ltd. (Guanghan, China) has also received permission to produce UL91, 100VLL [60].

The dynamics of aviation gasoline consumption and production volumes in the Asia–Pacific domestic market other than China is shown in Figure 8. The key consumer and producer of aviation gasoline in the region (over 60%) is Australia. In general, it can be noted that the market is quite stable.

The exporters of the region are South Korea and Australia, with a larger share by the former (15–20 thousand tons in the years 2017–2020). Importers (as shown in Figure 9) are mainly countries that do not produce aviation gasoline, such as New Zealand, Laos, the Philippines, India, and various island states. RegardingIndia, it is interesting to note that country has initiated a program for the import substitution of aviation gasoline [61]. As early as 2023, the country exported 100LL grade gasoline for the first time, which was produced by Indian Oil Corporation [62].

3.1.6. The African Aviation Gasoline Market

Due to the political and economic situation in most African countries and the lack of other statistical sources and news in the public domain other than UN data, estimates of the market situation, production, and consumption levels may be subject to significant deviations. This study assumes that there is no production of aviation gasoline in the African region. On this basis, the volume of imports by country will be numerically equal to the volume of consumption and, accordingly, the overall dynamics of imports will correspond to the dynamics of consumption. The dynamics and structure per country are presented in Figure 10. The largest importers of aviation gasoline of both leaded and unleaded grades are Gabon, Guinea, Ghana, Mali, the Republic of South Africa, and others.

3.1.7. The Aviation Gasoline Market of CIS Countries

The dynamics of the consumption and production of aviation gasoline in the domestic markets of CIS countries in open sources is only given for Uzbekistan, Kazakhstan, and Russia; it is presented in Figure 11. According to the source [27], the level of aviation gasoline consumption in Uzbekistan in the period from 2011 to 2020 decreased from 2 thousand tons/year to 1 thousand tons/year. Information from source [63] confirms the existence of the production of aviation gasoline in Uzbekistan at the Fergana refinery. There is information about Turkmenistan’s plans to start production of aviation gasoline at the Turkmenbashi refinery [64]. Aviation gasoline production data for Kazakhstan is presented in the Figure 11, based on UN statistical information. Data on the dynamics of aviation gasoline exports from the CIS countries and Russia are not available in open sources.

Currently, the Russian aviation gasoline market is represented by two grades. About half of the market is occupied by Avgas 100LL. Due to the extensive experience of the USSR in the production of its own grades of aviation gasoline, as well as in the production and operation of domestic piston aviation equipment and the presence of a large number of piston aircraft produced back in the USSR in the fleet, the domestic market has its own peculiarities. Thus, B-91/115 grade, developed in the USSR, is in demand and is produced in Russia. B-91/115 grade aviation gasoline is mostly used for the needs of the Russian Ministry of Defense (in particular, for aviation schools and the Russian Army, Air Force, and Navy Volunteer Society), while AVGAS 100LL aviation gasoline is used for the needs of civil aviation (commercial/non-commercial aviation, special purpose aviation, etc.).

Figure 12 shows data on the dynamics of aviation gasoline consumption in Russia by grade since 2010 and a forecast up to 2030 (under the baseline scenario described above).

The demand of the Russian fleet regarding the grades consumed is equally estimated between Avgas 100LL and B-91/115. The vast majority of aircraft in the Russian fleet are also allowed to use automotive gasoline with RON 95, but in this case, additional restrictions are imposed in the form of a shortened service interval, payload limitations, and maximum flight altitude. Mogas was often used until 2014 due to the high price of imported aviation gasoline in use in Russia. Imported gasoline was the only available option at that time. At the moment, the volume of mogas used to operate piston aviation equipment is estimated at 300 tons/year.

Unleaded aviation gasoline is currently unavailable on the Russian market due to indirect legislative restrictions. Mandatory requirements for aviation gasoline are set by the Technical Regulation of the Customs Union TR TS 013 “On requirements for motor and aviation gasoline, diesel and marine fuel, jet fuel and fuel oil”. This document contains mandatory requirements for “performance number” (rich mixture), which is at least 115 units and labelled as the color “green”. Regulatory requirements for imported unleaded aviation fuel do not require the determination of the performance number due to the fact that this indicator only has objective significance for leaded gasoline. Thus, imported unleaded aviation fuel cannot be legitimately used on the territory of the Russian Federation and the Customs Union.

3.2. Production and Economic Performance Relations

Economic indices—the share of production in GDP and per capita consumption of aviation gasoline—allow for an indirect assessment and comparison of the current states of general aviation, as well as the refining industry. Thus, the highest per capita consumption is observed in New Zealand, Australia, USA, and Canada due to the high levels of the development of the general aviation industry.

The largest share of aviation gasoline production in GDP is observed in developed countries with high GDP per capita, such as the USA, Canada, Australia, Poland, and the Netherlands. A summary of the aviation gasoline market and its relation to GDP is given in

Table 3. Statistical indicators for aviation gasoline and their relationship with economic indices.

The Region	The Country	Consumption, kt/Year	Population, Million	Consumption per Capita	GDP, Billion USD	Production, kt/Year	GDP per Capita	Share in GDP, %
North America	USA	507	335.16	1.52	24,462	468	73.0	0.0046
	Canada	27	40.2	0.67	2273	36	56.5	0.0038
	Mexico	18	129.04	0.14	2742	0	21.3	-
South America	Brazil	27	203.06	0.13	3837	2	18.9	0.0002
	Colombia	10	52.26	0.19	1052	11	20.1	0.0031
	Argentina	5	46.05	0.11	1225	0	26.6	-
Europe	France	20	68.128	0.30	3769	25	55.3	0.0018
	United Kingdom	12	67.026	0.18	3656	0	54.5	-
	Germany	4	84.358	0.05	5309	0	62.9	-
	Poland	5	37.726	0.12	1625	32	43.1	0.0054
	Netherlands	1	17.886	0.07	1231	63	68.8	0.0139
CIS	Russia	10	146.424	0.07	5326	9	36.4	0.0005
	Kazakhstan	6	19.854	0.30	604	6	30.4	0.0027
	Uzbekistan	1	36.197	0.03	339	1	9.4	0.0008
Asia–Pacific	Australia	43	26.659	1.61	1626	39	61.0	0.0044
	New Zealand	7	5.199	1.35	237	0	45.6	-
	Republic of Korea	1	51.439	0.02	2585	13	50.3	0.0008
Africa	Ghana	7	30.832	0.23	196	0	6.4	-
	Gabon	19	2.233	8.51	35	0	15.7	-
	Guinea	13	13.261	0.98	39	0	2.9	-
	Mali	5	23.293	0.21	51	0	2.2	-

.

To carry out the calculation of the GDP share, average aviation gasoline prices were considered, taking into account the following facts: In Europe, between September 2020 and now, the price of Avgas 100LL leaded gasoline varies from 1.3 to 3.05 euro/L depending on the region. The average price at the same time is 2.43 euros with a standard deviation of 0.53 and dispersion of 0.28. Unleaded Avgas 91UL ranges from 1.7 to 2.4 euro/L with an average price of 2.04 euro/L euro with a standard deviation of 0.44 and dispersion of 0.19. It should be noted that within one airport, UL91 gasoline is sold at a price 5–7% lower than leaded 100LL gasoline [29]. The average price of Avgas 100LL was taken for calculations. In North America, the price of Avgas 100LL aviation gasoline ranges from $4.25 to $12.5/gallon, with an average of $6.9/gallon (approximately $2.4/kg) with a standard deviation of 1 and dispersion of 1.2 [30]. Costs in Australia are based on information on an airport website [31] and in South Korea, on Indian import data [32].

3.3. The State of the World’s Piston Aviation Fleet

The development of the global aviation gasoline market primarily depends on the prospects of piston aviation. Figure 13 shows the FAA forecast for the development of general aviation [56]. According to the FAA, the general aviation fleet will increase annually until 2043 by an average of 0.2%; thus, the number of aircraft will grow from 209,140 in 2022 to 216,395 in 2043. However, piston aviation represents only 71.2% of the general aviation fleet. The number of piston aircraft is expected to decline from 140,485 in 2022 to 122,350 in 2043; thus, the average annual decline of piston aircraft will be about 0.6%. The reason for this is the overall growing cost of aircraft ownership and the availability of cheaper alternatives.

In order to assess the prospects for unleaded aviation gasoline production, it is necessary to estimate the amount of piston aircraft and approved fuel produced over the last decades. The analysis of the global production of piston aircraft in the period 2006–2019 and their fuel requirements according to GAMA (The General Aviation Manufacturers Association) is presented in

Table 4. The structure of the world fleet of aircraft manufactured in 2006–2019 by fuel consumption.

Indicator	UL91	UL94	100LL	Total
Airplanes, pcs.	8149	9533	19,511	19,511
Helicopters, pcs.	3383	3383	5688	5688
Total, pcs.	11,532	12,916	25,199	25,199
Scope among airplanes %	41.8	48.9	100.0	100.0
Scope among helicopters %	59.5	59.5	100.0	100.0
Scope among all aircraft, %	45.8	51.3	100.0	100.0
Airplanes, pcs.	8149	9533	19,511	19,511

[65].

According to the analyzed data, 100LL covers 100% of the modern aircraft fleet, while UL91 unleaded gasoline can be used on 46% of new aircraft. The scope of UL94 unleaded gasoline is slightly higher—51% due to the availability of Continental Motors TSIO-550-K engine approval. A new grade of unleaded aviation gasoline, G100UL, has been approved for use in all engine types, which also means full fleet coverage [18]. As the total number of small aircraft fleets decreases, demand for aviation gasoline is expected to decrease by 10–15%.

3.4. An Overview of Components Used in the Production of Aviation Gasoline

In order to determine the components applicable for use in the composition of unleaded aviation gasoline, first of all, it is necessary to consider the requirements of regulatory documentation to their physical and chemical characteristics. Requirements for the physical and chemical characteristics of UL91 and UL94 grades of aviation gasoline are established by ASTM D7547 [66]. Requirements for UL91 grade are also included in the DEF STAN 91-090 standard [67]. For high-octane aviation gasolines with a MON over 100, there are currently no unified requirements. There are UL100 and UL102 test grades. Research on their development is carried out by several foreign companies. Currently, they are undergoing a set of bench tests. The requirements for the characteristics have not been completely formulated. Specifications for test gasoline grades are set in ASTM D7960 [68], ASTM D7719 [69], and ASTM WK69284 standards [70].

Table 5. Requirements for the different grades of aviation gasoline.

Property	Limit	TR TS 013/2011	100VLL ASTM D910	UL91 ASTM D7547	UL91 DEF STAN 91-090	UL94 ASTM D7547	UL102 ASTM D7719	UL102 ASTM D7960	100M ASTM D8434
Motor Octane Number	Min.	91.0	99.6	91.0	91.0	94.0	102.2	102.5	99.6
Rated Octane Number		-	-	-	95.0	-	-	-	-
Performance number	Min.	115 1	130	-	-	-	-	-	130
Lead content, g Pb/L	Max.	-	0.45	0.013	0.013	0.013	0.013	0.013	0.013
Manganese content, g Mn/L	Min.–Max.	-	-	-	-	-	-	-	0.05–0.1
Density at 15 °C, kg/m3	Min.–Max.	-	report	report	report	report	790–825	report	report
Distillation:
Initial boiling point, °C	Min.	-	report	report	report	report	report	report	report
10% is evaporated at temperature, °C	Max.	82	75	75	75	75	75	75	75
40% is evaporated at temperature, °C	Min.	-	75	75	75	75	75	75	75
50% is evaporated at temperature, °C	Max.	105	105	105	105	105	165	105	105
90% is evaporated at temperature, °C	Max.	170	135	135	135	135	165	135	135
Final boiling point, °C	Max.	-	170	170	170	170	180	210	170
Sum of 10 and 50% evaporated, °C	Min.	-	135	135	135	135	135	135	135
Recovery, % vol.	Min.	-	97	97	97	97	97	97	97
Residue, % vol.	Max.	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
Loss, % vol.	Max.	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
Vapor pressure, kPa	Min.–Max.	29.3–49.0	38.0–49.0	38.0–49.0	38.0–49.0	38.0–49.0	38.0–49.0	38.0–49.0	38.0–49.0
Freezing point, °C	Max.	−60	−58	−58	−58	−58	−58	report	−58
Sulfur content, % by mass	Max.	0.03	0.05	0.05	0.05	0.05	0.05	0.05	0.05
Net heat of combustion, kJ/kg	Min.	-	43.5	43.5	43.5	43.5	41.5	42	43.5
Corrosion of copper strip, 2 h at 100 °C	Max.	-	No. 1	No. 1	No. 1	No. 1	No 1	No 1	No 1
Oxidation stability, potential gum mg/100 mL	Max	-	6	6	6	6	6	6	6
residue	Max	-	-	3	2	3	-	-	-
Total gum, mg/100 mL	Max.	3	-	-	-	-	-	1	-
Mechanical impurities and water content	Max	absence	-	absence	-	absence	-	-	-
Water reaction, volume change, mL	Max.	-	±2	±2	±2	±2	±2	±2	±2
Electrical conductivity, pSm/m 3	Min.–Max.	-	50–450	50–450	50–600	50–450	50–450	50–450	50–450
Color	-	Green 2	-	-	-	-	-	-	-
Content of aromatic hydrocarbons, % wt.	Min.	-	-	-	-	-	70	-	-
Benzene content, % wt.	Max.	-	-	-	-	-	0.1	-	-

¹ For B-92 grade, the standard for the indicator “performance number” is not less than 100; it is determined at the stage of production preparation and is guaranteed by the production technology. ² Aviation gasoline with a MON of at least 99.5 and a performance number of at least 130 may contain blue dye. ³ Determined only when an antistatic additive is used.

shows a comparison of requirements for these grades, as well as mandatory requirements for aviation gasoline sold in the territory of the Customs Union, established by TR TS 013/2011 [71].

Based on the data given in Table 5, it follows that the requirements for UL91 and UL94 grades fully correspond to the requirements for Avgas 100LL, except for the indicators characterizing antiknock properties (MON, performance number), as well as color. Consequently, the production technologies of UL91 and UL94 aviation gasoline should be close to the production technologies of Avgas 100LL. Based on literature data [28], the average component composition of Avgas 100LL is shown in

Table 6. The average component composition of aviation gasoline AVGAS 100LL.

Component	Concentration, % wt.
Alkylate	up to 70
Isomerate and isopentane fraction	10–20
Toluene	10–25
Isooctane	up to 90
TEL	up to 0.19
Antioxidant, mg/kg, max.	16
Dye, mg/kg, max	2.7

.

It is known that the exceptionally high anti-detonation properties of Avgas 100LL are provided as a result of the use of tetraethyl lead (TEL), which is added in an amount not exceeding 0.56 g/L (in conversion to lead) to the base carbon–hydrogen blend. The required color of commercial gasoline is provided by introducing dyes.

The basic component of aviation gasoline is alkylate [72]. The main compounds included in alkylate are C8 isoparaffins, which have the highest specific mass heat of combustion and a high-octane number. Characteristics that delineate the limits of alkylate involvement in Avgas 100LL are high temperatures of 10% and 50% evaporated volumes, the final boiling point, as well as low vapor pressure.

According to data in the literature, Avgas 100LL is traditionally produced using the so-called light alkylate as the main component, since the broad fraction alkylate used for the production of mogas has FBP values that are too high, which limits its application without the separation of the light fraction [72].

Other high-octane components of aviation gasolines are aromatic hydrocarbons, primarily toluene. They are characterized by high temperatures of 10% and 50% evaporated volumes, low vapor pressure, and a low value of the specific mass heat of combustion, which indirectly limits their share in the composition. Traditionally, the concentration of the aromatic component in the composition of aviation gasoline is kept close to the upper limit, limited by the above-mentioned characteristics. Since UL91 and UL94 performance requirements (except for knock resistance) are similar to Avgas 100LL, the presence of the aromatic component is also necessary for meeting regulatory requirements.

To ensure optimal vaporizability, aviation gasolines contain light components—isopentane fraction or isomerate. These components have a high vapor pressure value, low temperatures of 40% evaporated volume and the sum of 10 and 50% evaporated volumes, as well as high losses. Their use in the composition of aviation gasolines makes it possible to adjust the value of vapor pressure in wide ranges.

Lower requirements for the detonation resistance of aviation gasoline grades UL91 and UL94 allow us to make the following assumption: in order to ensure the required quality indicators for these grades, it is advisable to use base hydrocarbon blends for Avgas 100LL without adding TEL.

According to earlier studies [73], it is not possible to meet all the requirements for Avgas 100LL aviation gasoline without using TEL. In order to obtain formulations with MON values above 100, it is necessary to use other high-octane components and additives that will affect the other parameters. Therefore, for such compositions, it is necessary to establish new standards for distillation points, first of all.

Some modifications to the requirements for the universal grade Avgas 100LL ASTM D910 open up prospects for the use of a number of high-octane components and additives to produce an alternative lead-free aviation gasoline grade. Scientific, technical, and patent literature discusses the use of the following products:

(1)

oxygen-containing compounds (oxygenates);

(2)

aromatic amines;

(3)

manganese antiknock agents;

(4)

individual aromatic hydrocarbons (other than toluene);

(5)

combinations of the compounds above.

An example of the use of aromatic hydrocarbons is the development of UL102 fuel by Swift Fuels, of which mesitylene (1,3,5-trimethylbenzene) is used in its composition [74]. The performance standards for this grade are set by the ASTM D7719 specification. This standard specifies that UL102 gasoline is a binary fuel composition consisting of 79–84% wt. mesitylene (1,3,5-trimethylbenzene) and 16–21% wt. isopentane (2-methylbutane). Swift Fuels envisions producing such fuels from renewable plant feedstocks. However, their low mass heat of combustion, high boiling point, as well as an increased tendency to form deposits in the combustion chamber can be noted among the disadvantages of aromatic hydrocarbons. On the other hand, as they have high density, aromatized fuels have a high volumetric heat of combustion. For this reason, ASTM D7719 standardizes the density of gasoline.

Manganese antiknock agents have found wide application as additives to mogas as a result of the ban on the production of leaded gasoline. Among many different compounds, cyclopentadienyltricarbonyl manganese and methylcyclopentadienyltricarbonyl manganese (MMT) have been widely used in practice. Currently, the use of manganese additives in mogas is prohibited in Russia [71]. The advantages of manganese antiknock agents are their high antiknock efficiency at low concentrations. However, there is also a disadvantage, which is the increased tendency of manganese-containing gasoline to form deposits in the combustion chamber of engines. Thus, manganese antiknock agents can theoretically serve as a substitute for TEL to increase the octane number for aviation gasoline. The use of manganese antiknock additives for aviation gasoline in concentrations from 0.01 to 0.5 g per liter of fuel is described in the patents of Afton Chemical Corporation [75] and Calumet Specialty Products Partners [76].

In 2015, Afton Chemical Corporation in cooperation with Phillips 66, submitted a draft standard to the ASTM committee that establishes standards for UL100 unleaded gasoline containing a manganese antiknock agent. The explanatory note to the draft standard specifies a formulation of UL100 unleaded gasoline that includes 5–15% isopentane and/or butane, 50–85% alkylate, 5–20% aromatics, and a <1% AvGuard UL proprietary additive package [70]. The standards set for the UL100 performance number are identical to those for Avgas 100LL bulk leaded aviation gasoline except for the lead content. The standard sets the norm for manganese content from 0.05 to 0.1 g. Mn/L. The fuel has passed a set of laboratory and bench tests.

When using gasoline with manganese-containing additives, there is a problem of the accumulation of manganese oxides in the combustion chamber. Therefore, manganese antiknock agents, like MMT, require a carrier of their combustion products from the engine cylinders. Afton Chemical Company’s patent [77] describes a combustion chamber manganese scavenger composition based on organophosphorus compounds selected from the groups of tritolyl phosphate, triphenyl phosphate, triisopropyl phosphate, dimethyl methyl phosphonate, triphenyl phosphine oxide, and triisopropyl phosphate. The patent also describes manganese scavenger from the groups of dibromopropane, dibromotoluene, and dibromomethylaniline.

Aromatic amines have been used as antiknock additives for aviation gasoline since the 1920s. In the USSR, extraline (technical purity N-methylaniline) was used for this purpose, and in the USA and England, xylidine was used [78]. Currently, the possibility of using aromatic amines for the production of unleaded alternative aviation gasoline with a MON over 100 is being considered in the USA [78]. Meta-toluidine (3-methylaniline) at concentrations ranging from 3 to 12% wt. is considered the most promising compound [68]. The patent also offers technical solutions for the use of various aromatic amines as high-octane additives to unleaded gasoline. Petroleo Brasileiro S.A. offers a composition of unleaded gasoline containing a mixture of toluidine isomers from 2 to 10% vol. [79]. ExxonMobil Research & Engineering Co. (Irving, TX, USA) proposes the use of various aromatic amines of the general formula NH2-Ar-(R1)n, where R1 is a C1-10 alkyl substituent located in the meta and para positions in the aromatic ring; Ar is a phenyl aromatic group; n is an integer from 0 to 3 [51]. In general, it should be noted that the use of aromatic amines can be a very promising direction for Russia, taking into account the experience accumulated in our country by using N-methylaniline as an additive to automobile and aviation gasoline. However, it is necessary to take into account the potential disadvantages of this approach, which are associated with the increased formation of deposits on valves when fuel containsa high concentration of aromatic amines in fuel. The standards for unleaded aviation gasoline in which amines are allowed are set forth in the ASTM D7960 specification for test grade UL102. The appendix to the standard describes an average fuel composition containing amines from 1 to 10% in the composition.

The use of oxygen-containing compounds (oxygenates) is one of the most promising directions for the development of unleaded aviation gasoline. Among various oxygenates the following deserve the most attention: ethanol, ethyl tert-butyl ether (ETBE) and methyl tert-butyl ether (MTBE).

There are various technical solutions for the use of ethanol (or bioethanol), both as a component of gasoline in a low concentration of up to 5% vol. [80] and as a base component of alternative aviation fuel. South Dakota State University (USA) conducted extensive research and tests of aviation fuel E85 (Aviation Grade E85-AGE85), consisting of 80–90% vol. of ethanol and hydrocarbon fraction C5 (mainly isopentane) with a small addition of fatty acid methyl esters as an anticorrosion additive [81]. The disadvantages of such fuel are its much lower heat of combustion, high latent heat of vaporization, high corrosion aggressiveness, and incompatibility with some elastomers. In addition, the use of AGE85 fuel requires modifications to the aircraft fuel system to adapt its operation at higher fuel/air ratios. However, despite the research conducted, AGE85 ethanol aviation fuel has not yet found commercial application as an alternative to aviation gasoline [82].

Dialkyl ethers (ETBE and MTBE) have a higher heat of combustion than ethanol, are nearly insoluble in water, and are less aggressive towards elastomers; as a result, the prospects for their application are evaluated more highly than ethanol. The Swedish company Hjelmco Oil, which has achieved the greatest practical success in the production of unleaded aviation gasoline grades 80/87 and UL91, is currently developing unleaded aviation gasoline UL100, which contains a significant amount of ETBE [83]. Texaco Development Corp. (Beaumont, TX, USA) in its patent [84] proposes a composition of unleaded aviation gasoline containing up to 40% dialkyl ethers (ETBE or MTBE) combined with aromatic amines and a manganese antiknock additive. It should be noted that in the USA, as a result of comprehensive studies on the development of a fuel composition of unleaded gasoline [73], a fundamental possibility of using ETBE at a concentration of up to 30% was established. In addition, the U.S. has developed an ASTM standard for ETBE for its use as a component of aviation fuel [85]. In Russia, studies were also conducted to involve MTBE in the composition of aviation gasoline B-91/115. Its high antiknock properties were established [86]. The use of oxygenates in unleaded aviation gasoline is also assumed in the ASTM D7960 specification for UL102 test grade. The appendix to the standard describes an averaged top-liquid composition, containing up to 10% heteroatom compounds (including oxygenates) in a composition.

In the United States, the development of unleaded aviation gasoline fuel compositions has been conducted since the late 1990s under the direction of the Coordinating Research Council, Inc. (CRC) (Alpharetta, GA, USA). In 2010, the CRC released a final report presenting the results of four phases of research on the development and testing of the fuel compositions of unleaded aviation gasoline alternative 100LL [73]. In the course of the work, 279 different fuel compositions were tested, of which 10 types of components and additives were used—the main ones being alkylate, aviation alkylate, technical purity isooctane, toluene, ethyl tert-butyl ether (ETBE), ethanol, metha-toluidine, and methylcyclopentadienyltricarbonyl manganese (MMT). The main conclusion of the CRC report is that it is impossible to obtain unleaded aviation gasoline that fully meets the requirements of ASTM D910 for 100LL grade.

Table 7. The compositions and test results of unleaded aviation gasoline with a MON above 100.

Component	CRC [73]	CRC [73]	CRC [73]	D7960 [68]	D7960 [68]	D7719 [69]	D7719 [69]	WK69284 [70]	WK69284 [70]
Alkylate	-	-	-	-	-	-	-	74.5	77.1
Aviation Alkylate	-	4.02	-	13.0	12.0	-	-	-	-
Technical purity iso-octane	42.51	39.98	46.98	-	-	-	-	-	-
Toluene	25.01	25.00	25.01	35.0	45.0	-	-	11.5	8.9
ETBE	29.98	29.79	24.99	-	-	-	-	-	-
Iso-octane 99%				26.0	12.0	33.0	13.0	-	-
Isopentane				20.0	21.0	10.0	10.0	9.6	12.9
Butane				-	-	2	2	4.4	1.1
Isobutanol				-	5.0	-	-	-	-
Mesitylene					-	55.0	75.0	-	-
Meta-toluidine	2.50	1.03	3.02	6.0	-	-	-	-	-
Aniline					5.0	-	-	-	-
MMT (mg Mn/L)								71.7	125
Test results
Motor Octane Number	101.0	99.8	101.2	101.0	103.7	99.8	101.3	99.8	100.2
Performance number	131.2	146.1	152.5	-	-	-	-	133.3	131.5
Density at 15 °C, kg/m3	765.1	760.2	764.0	766.0	779.0	773.1	815.4	708.1	702.6
Fraction composition: Initial boiling point, °C	81.0	79.5	82.5	-	-	-	-	36.0	37.0
10% is evaporated at temperature, °C	89.5	88.5	90.0	63.3	65.5	-	-	68.0	68.5
40% is evaporated at temperature, °C	93.5	93.0	94.5	101.6	101.4	-	-	95.0	95.5
50% is evaporated at temperature, °C	95.0	94.5	96.5	103.9	104.0	-	-	97.0	98.0
90% is evaporated at temperature, °C	112.5	109.5	113.5	120.4	115.5	-	-	98.5	103.0
Final boiling point, °C	191.5	178.0	189.5	196.9	179.0	-	-	116.5	138.0
Sum of 10 and 50% evaporated, °C	184.5	183.0	186.5	167.2	169.5	-	-	165.5	166.5
Recovery, % vol.	99.0	98.9	98.5	-	-	-	-	98.5	98.5
Residue, % vol.	0.9	1.0	0.8	-	-	-	-	0.7	0.9
Loss, % vol.	0.1	0.1	0.7	-	-	-	-	0.8	0.6
Vapor pressure, kPa	17.4	18.7	16.6	42.5	44.1	-	-	47.8	41.2
Freezing point, °C	<−70	−41	−47	−70	−65.5	-	-	<−70	<−78
Net heat of combustion, MJ/kg	40.61	40.78	40.96	42.5	42.13	42.40	41.70	43.8	44.0
Oxidation stability (5 h aging):
potential gum, mg/100 cm3	2	3	4	-	-	-	-	2	2
residue, mg/100 cm3	<0.1	0.3	<0.1	-	-	-	-	0.3	0
Water reaction, volume change, cm3	0	0	0	-	-	-	-	0	0

summarizes the most successful fuel compositions and their test results from the CRC report. In addition, Table 7 shows the test results and compositions of unleaded gasoline compositions with a MON above 100, developed by leading companies in this field and published in the relevant patents.

As can be seen from the CRC results, the achievement of the MON value corresponding to the standard for 100LL gasoline—at least 99.6—as well as performance number—at least 13—is possible only if the gasoline simultaneously contains at least 1% vol. m-toluidine, 29.9% vol. ETBE, and 25% vol. toluene. However, the heat of the combustion of such a composition due to the high proportion of toluene and ETBE is 40.78 MJ/kg, which is much lower than the value established in ASTM D910—43.5 MJ/kg. In addition, this composition does not meet the specifications for freezing point, vapor pressure, and some points of distillation. A much higher concentration of m-toluidine, up to 10% vol, is required to obtain more acceptable values of the heat of combustion with a reduced fraction of toluene and ETBE. It should also be noted that in all compositions that met the requirements of ASTM D910 for knock resistance, technical purity isooctane was used as one of the base components.

CRC’s research was the basis for ASTM D7960. The development of compositions according to this document was actively carried out by Shell. According to patent data, it is possible to produce unleaded UL102 grade meeting the requirements of ASTM D7960 on the basis of alkylate (15–30% vol.), toluene (35–55% vol.), and isopentane (from 8% vol.) with the addition of a 2 to 10% vol. of aniline and 4 to 10% vol. of C4–C5 alcohols [87].

The production of an unleaded aviation gasoline of UL100 grade corresponding to the requirements of the new WK69284 under development and according to the patents of Afton Chemical Corp (Richmond, VA, USA) [75,88] is possible when using a base component of aromatic compounds from 1 to 50% (vol.) and aviation alkylate from 20% (vol.) with the addition of a manganese-containing organic compound, ensuring the concentration of manganese in the fuel composition is not more than 125 mg/L. The averaged component compositions of unleaded aviation gasolines with a MON not less than 100 are given in

Table 8. The average component composition of aviation gasolines UL100.

Component	UL102 ASTM D7960	UL102 ASTM D7719	UL100 ASTM WK69284
Alkylate	15–30	0–5	50–85
Technical purity iso-octane	15–30	0–15	-
Isomerate C5–C6	15–30	-	-
Isopentane fraction	15–30	10–20	0–15
Aromatic hydrocarbons	35–55	58–88	0–20
Butane	-	0–2	0–5
Aromatic amines	2–10	-	-
Oxygenates	4–10	-	-
MMT	-	-	up to 125 mg Mn/L
TOTAL	100	100	100

.

4. Conclusions

The FAA forecasts that the production of aviation gasoline remains low, and there is no tendency to increase its production; on the contrary, the number of gasoline-powered fleets is expected to gradually decrease, with substitution towards jet-powered aircrafts. Nevertheless, until 2043, more than 50% of general aviation will be piston-powered aircraft, which means that aviation gasoline will need to be produced to operate aircraft for the next 20 years at least. The objective of the work was to assess the key regions involved in production, how imports and exports have changed over the last 10 years, and how technology will change. The main findings of the research can be summarized as follows:

• The largest share of aviation gasoline production in a GDP is observed in developed countries with a high GDP per capita, such as the USA, Canada, Australia, Poland, and the Netherlands. Just 5 of these countries account for 88% of aviation gasoline production. A total of 77% of consumption is in the USA, Canada, Brazil, France, and Australia. In general, less than 10 market players influence its development.
• The decarbonization of civil aviation has not yet reached light aviation; there are currently no roadmaps, except for the phase-out of leaded fuel. However, as civil aviation decarbonizes and moves away from piston engines, the use of aviation gasoline will gradually decline. It will be replaced with jet-powered aircraft as well as hydrogen and electricity.
• However, before piston aircraft are phased out, the primary issue of lead in fuel needs to be resolved, and fuel can be standardized. Today’s aircraft fleet are 100% covered by 100LL gasoline; the recent approval of G100UL fuel for all engine types holds great promise for the introduction of unleaded aviation gasolines. Once the leaded gasoline ban is implemented, the market is expected to switch to 100% unleaded gasoline.
• The average composition of UL91 and UL94 unleaded grades based on alkylate, isomerate, isopentane fraction, and an aromatic component was formulated. The main directions for the possible development of aviation gasolines with a MON over 100 have been determined as follows: the use of aromatic amines, manganese antiknock agents, and individual aromatic hydrocarbons in the composition of oxygenates.