Among primary alcohols, bio-n-butanol is considered as a promising alternative fuel candidate. However, relatively low production efficiency and high cost of component recovery from the acetone-n-butanol-ethanol (ABE) or isopropanol-n-butanol-ethanol (IBE) fermentation processes hinders industrial-scale production of bio-n-butanol. Hence it is of interest to study the intermediate fermentation product, i.e. ABE and IBE as a potential alternative fuels. However, for fuel applications, the IBE mixture appears to be more attractive than ABE due to more favorable properties of isopropanol over acetone, such as being less corrosive to engine part, higher energy density and octane number. In this study, an experimental investigation on the performance, combustion and emission characteristics of a port fuel-injection SI engine fueled with IBE-gasoline blends was carried out. By comparisons between IBE-gasoline blends with various IBE content (0 vol.%-60 vol.% referred to as G100-IBE60) and more commonly used alternative alcohol fuels (ethanol, n-butanol and ABE)-gasoline blends, it was found that IBE30 performed well with respect to engine performance and emissions, including brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), carbon monoxide (CO), unburned hydrocarbons (UHC) and nitrogen oxides (NO x). Then, IBE30 was selected to be compared with G100 under various equivalence ratio (Φ=0.83~1) and engine load (300 and 500 kpa BMEP). Overall, higher BTE (0.04-4.3%) and lower CO (4%), UHC (15.1-20.3%) and NO x (3.3-18.6%) emissions were produced by IBE30 compared to G100. Therefore, IBE could be a good alternative fuel to gasoline due to the environmentally benign fermentation process (from non-edible biomass feedstock and without recovery process) and the potential to improve energy efficiency and reduce pollutant emissions.

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Alcohols, especially n-butanol, have received a lot of attention as potential fuels and have shown to be a possible alternative to pure gasoline. The main issue preventing butanol's use in modern engines is its relatively high cost of production. ABE, the intermediate product in the ABE fermentation process for producing bio-butanol, is being studied as an alternative fuel because it not only preserves the advantages of oxygenated fuels, but also lowers the cost of fuel recovery for individual component during fermentation. With the development of advanced ABE fermentation technology, the volumetric percentage of acetone, butanol and ethanol in the biosolvents can be precisely controlled. In this respect, it is desirable to estimate the performance of different ABE blends to determine the best blend and optimize the production process accordingly. In this paper, pure ABE fuels with different component volumetric ratio, (A: B: E of 3:6:1, 6:3:1 and 5:14:1), were combusted in a naturally aspirated, port-fuel injected spark ignited engine. The performance of these blends was evaluated through measurements of in-cylinder pressure, and various exhaust emissions. In addition, pure gasoline and neat n-butanol were also tested as baselines for comparison of ABE fuels. The tests were conducted at an engine speed of