Process for preparing high-octane gasoline blending stock

Details Process for preparing high-octane gasoline blending stock Process for preparing high-octane gasoline blending stock

1993-04-16

1994-01-04

Pal, Asok

Chemistry of hydrocarbon compounds

Aromatic compound synthesis

By ring formation from nonring moiety, e.g., aromatization,...

585407, 585417, C07C 200

Patent

active

052762327

DESCRIPTION:

BRIEF SUMMARY
FIELD OF TECHNOLOGY

This invention relates to a process for preparing high-octane gasoline blending stock mainly comprising of aromatic hydrocarbons.


BACKGROUND TECHNOLOGY

Catalytic reforming of straight-run naphtha in the presence of a platinum-alumina catalyst has been adopted widely as a process for preparing high-octane gasoline on a commercial basis. As naphtha to be fed to this catalytic reforming, a fraction boiling in the range from 70.degree. to 180.degree. C. is used for the preparation of automotive gasoline while a fraction boiling in the range from 60.degree. to 150.degree. C. is used for the preparation of BTX.
With this type of catalytic reforming, the conversion of feed naphtha to aromatic hydrocarbons decreases markedly as the number of carbon atoms in the naphtha decreases and this makes it difficult to prepare high-octane gasoline blending stock from light hydrocarbons mainly comprising of paraffins and/or olefins having 2 to 7 carbon atoms. For this reason, light hydrocarbons find limited uses as raw materials for the production of petrochemicals and city gas under the present conditions.
In consequence, technologies for preparing high-octane gasoline blending stock from light hydrocarbons are drawing attention in recent years as they enhance the value added of light hydrocarbons and accomodate increasing gasoline consumption.
The technologies proposed thus far for the preparation of high-octane gasoline blending stock from light hydrocarbons utilize a variety of catalysts: for example, hydrogen type ZSM-5, Ga-impregnated and/or Ga-exchanged hydrogen type aluminosilicates of MFI structure, hydrogen type gallosilicates of MFI structure, steam-modified crystalline galloaluminosilicates obtained by treating hydrogen or ammonium type galloaluminosilicates of MFI structure with steam [Kohyo Tokkyo Koho 60-501, 357 (1985)], and hydrogen type aluminogallosilicates of MFI structure described in an invention of the present inventors, Japan Kokai Tokkyo Koho No. Sho 62-254, 847 (1987).
However, hydrogen type ZSM-5, Ga-containing aluminosilicates, and crystalline gallosilicates are inferior to hydrogen type crystalline aluminogallosilicates as catalyst for the production of aromatic hydrocarbons. On the other hand, the aforesaid steam-modified crystalline galloaluminosilicates have structural defects as steam eliminates aluminum together with gallium from the skeletal structure during the modification with steam; they are likely to suffer permanent degradation of their catalytic activity in the course of their prolonged use and they are not yet satisfactory for commercial use. The aluminogallosilicates described in Japan Kokai Tokkyo Koho No. Sho 62-254, 847 (1987) do not show noticeable detachment of gallium from the crystal skeletal structure even in an atmosphere of hydrogen; however, they yield gradually less and less of aromatic hydrocarbons over a prolonged period of time with the selectivity to aromatic hydrocarbons being not sufficiently high and they still need to be improved in order to be commercially acceptable.
In the reactions directed to the preparation of high-octane gasoline blending stock from light hydrocarbons, it is important to maintain the yield of aromatic hydrocarbons at a high level stably over a prolonged period of time. Those catalysts which show a high activity in the initial phase but degrade easily, for example, suffer a severe loss of the activity by deposition of coke, are not suitable for commercial applications. Ideal catalysts are those which show a high activity initially and maintain that activity for a long period or to have a long life.
The reactions for the preparation of high-octane gasoline blending stock from light hydrocarbons in the presence of zeolite catalysts generally detest the presence of moisture.
The reaction of this kind is usually conducted at high temperature in the range from 300.degree. to 700.degree. C. If any moisture into contact with the catalyst at such a high temperature, it extracts the aluminum atoms in the catalyst or it cause

REFERENCES:
patent: 4761511 (1988-08-01), Barlow
patent: 4994254 (1991-02-01), Suzuki et al.
patent: 5073673 (1991-12-01), Hirabayashi et al.

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