Research octane rating, gasoline

An octane rating scale was devised for fuels to quantify their knock resistance. Further research led to cataloguing the antiknock qualities of the myriad individual hydrocarbon species found in gasoline. 

Alkylation, where the olefins are reacted with isobutane to make a very desirable gasoline blending stock. Alkylate is an attractive blending component because it has no aromatics or sulfur, low vapor pressure, low end point, and high research and motor octane ratings,... 

The first stage product is then combined with a recycle stream and led to the second-stage converter. The inlet temperature is about 345°C (650°F) and the outlet approximately 400°C (750°F). The second-stage converter, filled with catalyst, produces gasoline constituents. The raw product is fractionated, the light ends alkylated, the naphtha recovered from the conversion steps is hydrotreated, and the products blended to produce a gasoline with a 92 research octane-clear (RON) rating. 

The more severe conditions of the Motor method have a greater influence on commercial blends than they do on the reference fuels. Thus, a Motor octane number of a commercial blend tends to be lower than the Research octane number. Recently, it has become the practice to label gasoline with an arithmetic avarage of both ratings, abbreviated (R + M)/2. 

Table I lists some of the available results from twenty of these commercial applications. In all cases, ZSM-5 increased both Research and Motor Octane. The ZSM-5 content in the unit inventory for these applications ranged from 0.2 to 3 wt %. The variations in the octane response from a given concentration of ZSM-5 are due to variations in the base octane (octane without ZSM-5), gasoline cut point, catalyst makeup rate and regenerator temperature.

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