High octane aromatics

Isomeri2ation of straight-chain hydrocarbons is of particular importance for lead-free gasoline. Addition of high octane aromatic hydrocarbons or olefins is questionable based on environmental considerations (77). An efficient octane enhancing additive is methyl tert-huty ether (MTBE). 

The incorporation of a ZSM-5 class zeolite into a ruthenium Fischer-Tropsch catalyst promotes aromatics formation and reduces the molecular weight of the hydrocarbons produced. These composite catalysts can produce a high octane aromatic gasoline in good yield in a single step directly from synthesis gas. 

The effect of crystallite size and shape of K-L zeolite on the dispersion of Pt was examined by a variety of techniques by Resasco and coworkers [143], They obtained multiple overlapping CO bands on these samples and were able to assign them to Pt clusters located inside the zeoHte pores (<2050cm ), near the pore mouth (2050-2075 cm" ) and outside the pores (>2075 cm" ). They were able to correlate high -octane aromatization activity with the K-L zeolite samples with short channels where most of the Pt is inside the pores. 

Reforming Both thermal and catalytic processes are utilized to convert naphtha fractions into high-octane aromatic compounds. Thermal reforming is utilized to convert heavy naphthas into gasoline-quality aromatics. Catalytic reforming is utilized to convert straight-run naphtha fractions into aromatics. Catalysts utilized include oxides of aluminum, chromium, cobalt, and molybdenum as well as platinum-based catalysts. 

More aromatic hydrocarbons needed, especially toulene for 5a. TNT benzene, toluene, and other high-octane aromatics... 

Benzene, along with other light high-octane aromatic hydrocarbons such as toluene and xylene, is used as a component of motor gasoline. Benzene is used in the manufacture of styrene, ethylbenzene, cumene, phenol, cyclohexane, nitrobenzene, and aniline. It is no longer used in appreciable quantity as a solvent because of the health hazards associated with it. 

In catalytic reforming, a low octane naphtha cut (typically a straight run or hydrocracked naphtha) is converted into high-octane aromatics, including benzene, toluene, and mixed xylenes. Aromatics are separated from the reformate by using a solvent such as diethylene glycol or sulfolane and then stripped from the solvent. Distillation is then used to separate the benzene-toluene-xylene into its components. 

As crude oil becomes more costly to recover from the ground, isomerization of pentane and hexanes can be expected to increase in prominence. Isomerization is the best way to raise the octane number of these low-boiling components of gasoline without loss in yield. Hydrocarbons with less than six carbons in the longest straight chain do not lend themselves to cyclization and conversion to high-octane aromatics. 

A.R. Pradhan, N. Viswanadham, M.L. Sharma, N. Ray, and T.S.R. Prasada Rao, Process for the production of LPG and high octane aromatic hydrocarbons from non economically viable petroleum feed stocks over a Zn-Al silicate molecular sieve catalyst , Indian Patent Application 871/DEL/94. 

When the lead content of motor gasolines is restricted, refiners must turn to other means of octane improvement in order to maintain the octane quality of their gasolines. The most widely used approach is to increase the amount of high-octane aromatics in gasoline. This will increase the polynuclear aromatics (PNA—sometimes referred to as polynuclear aromatic hydrocarbons or PAH) and the reactive smog-forming constituents in vehicle exhaust emissions. 

The reformer converts naphthenes and paraffins to high octane aromatics and branched paraffins (Table 4). In addition, low-carbon-number paraffins (C5-) outside the gasoline boiling range are produced and there is a net generation of Hj. These transformations take place through a complex set of chemical reactions which involve over 300 chemical species. In general, reactions can be classified by type as shown here. 

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