GB709583A - Cracking heavy hydrocarbonaceous residues, to obtain products rich in aromatic hydrocarbons - Google Patents

Abstract

Heavy hydrocarbon oils are cracked to obtain products rich in aromatic hydrocarbons boiling in the gasoline range, by contacting the oil with a dense fluidized mass of catalytically-inert solid particles at a temperature of 850 DEG to 1200 DEG F., and then contacting the effluent vapours from the inert mass with a dense fluidized mass of catalytic solid particles, containing a substantial proportion of copper, at a temperature of 1050 DEG to 1200 DEG F. The products contain olefins in addition to aromatic hydrocarbons. Suitable inert materials for use in the first stage are coke, sand, clay, silica gel, and kieselguhr. The catalytic material for the second stage may be finely-divided copper metal, or an alloy of copper with nickel, chromium or silver; or it may be copper in amounts of 5 to 50 per cent. deposited on kieselguhr, bauxite, silica gel, alumina, or titania. Pumice or kaolin may serve as the base for the copper catalyst. The inert particles and the catalytic particles are preferably maintained as <PICT:0709583/III/1> two superimposed fluidized beds in the same reactor. A heavy residual oil (pour point about 105 DEG F.), obtained as bottoms stream from the vacuum distillation of South Louisiana crude oil, is preheated to 500*-700 DEG F. and mixed in line 1 with coke particles (80-200 mesh) at a temperature of 900 DEG -1300 DEG F., which are supplied from standpipe 3. The mixture of partially vaporized feed and coke is passed, at a temperature of 850 DEG -1200 DEG F., through distributing cone 7 into the lower section of reactor 10 where a turbulent mass of solids Ma having an upper interface La is formed. If desired, additional fluidizing gas such as steam and/or hydrocarbon gases may be supplied via line 12 and/or 13 to establish a linear superficial vapour velocity of about 0.3 to 3 ft./sec. in the lower section of reactor 10. Fluidized solids carrying freshly deposited coke are withdrawn through standpipe 15. Part of the coke is conveyed into line 19, and carried by air into heater 20 where it is submitted to partial combustion, being raised thereby to a temperature of 900 DEG -1300 DEG F. The flue gases are withdrawn via line 24, while the reheated solids are withdrawn into standpipe 3. Coke product (6-8 per cent. of the feed oil) is withdrawn from the system through line 17. Vapours containing entrained solids pass upwards from level La in reactor 10, and impinge against grid 30 which throws back the solids to mass Ma but allows the vapours to pass on to the upper section of the reactor. This upper section contains a fluidized mass Mb of silica gel particles (80-200 mesh) having 10 per cent. of copper deposited thereon. The temperature of this catalytic mass is maintained at 1050 DEG -1200 DEG F., and the hold-up of the mass provides for a vapour-solids contact time of 2-30 seconds. The products pass through a cyclone 32 and line 34 to conventional recovery equipment (not shown). The products contain 10-25 volume per cent. of C6+ hydrocarbons boiling in the range 150 DEG -400 DEG F. containing 75-95 per cent. benzene, toluene and xylenes. Other products are C2-C3 olefines, butadiene, isoprene, piperylene, cyclopentadiene, butenes, iso and normal pentenes, and cyclopentene. There is also obtained an aromatic fraction boiling in the range 400 DEG -700 DEG F., and an aromatic tar boiling above 700 DEG F. Contaminated catalyst is continuously withdrawn from mass Mb through standpipe 36, and conveyed by air through line 38 into regenerator 40, where a dense fluidized mass M40 is maintained. The coke is burned off the catalyst, and the latter is maintained at about 1100 DEG -1400 DEG F., excess heat being used to raise steam in coil 56. The combustion gases are withdrawn through line 46, and the regenerated catalyst is returned to mass Ma through standpipe 52. A supersonic attriter may be arranged in line 1 and/or line 19. Coal tar, asphalt and pitch may also be cracked by the above process.