GB788000A - Improved method and apparatus for reacting carbon-containing gaseous compounds in the presence of a catalyst - Google Patents

Abstract

<PICT:0788000/III/1> Reactions, e.g. cracking of hydrocarbon oils, are effected by contacting a carbon-containing reactant vaporous at a reaction temperature with a fluidized catalyst (e.g. containing silica and alumina, zirconia, boria or magnesia) in a reaction zone (10), withdrawing contaminated catalyst through a vertical riser (20) in suspension in an oxygen-containing gas to a regeneration zone (11) vertically above the reaction zone, in which it is maintained in fluidized condition by means of an oxygen-containing gas, and returning the regenerated catalyst to the reaction zone by means of a plurality of vertical stand pipes (21, 22) symmetrically arranged round the riser (20). The numerals refer to the apparatus illustrated in Fig. 1 in which the regenerator is supported upon the reactor by means of an intermediate vessel 12 through which air can circulate freely. The regenerator may, however, rest directly on the reactor if it has a diameter less than about 25 feet. The vaporous portion of a hydrocarbon oil such as gas oil, reduced crude, vacuum distillate or solvent decarbonized residual oil having an initial boiling point of 400-600 DEG F., and an end point of 700-1300 DEG F. and an A.P.I. gravity of 10 DEG to 40 DEG , e.g. 25 DEG , may be cracked at 850 DEG to 950 DEG F., e.g. 900 DEG F., by introduction into reactor 10 through nozzles 44, at a pressure of 1 atmosphere to 50 p.s.i.g., preferably 5 to 25 p.s.i.g., a weight space velocity of 0.25 to 15, e.g. 0.5 to 5, and a catalyst to oil ratio of 2 to 25, e.g. 5 to 10 by weight. Thereafter the catalyst may pass via louvres 18 shielded by baffles 19 into a striping zone concentric with the riser and supplied with a stripping gas such as steam, hydrogen, flue gas, carbon dioxide or a normally gaseous hydrocarbon (methane, ethane or propane) maintained at e.g. 5 DEG to 20 DEG F. higher than the reaction zone, e.g. at 800 DEG to 1000 DEG F., usually 875 DEG to 950 DEG F., or in a specific example at 1080 DEG F. The catalyst is then withdrawn by means of the riser 20 and reciprocable valve 27. The riser is sealed from the reactor by means of expansion joint 24 lying within the intermediate chamber and the valve 27 is controlled to provide the desired flow rate irrespective of the position of the valve seat 28 in the end of the riser. It is preferred to supply from 10 to 40 per cent of the total amount of oxygen-containing regenerating gas through the riser and to convey the catalyst at from 10 to 60 ft. per sec. From 0.05 to 0.5 cu. ft. of said gas may be used in the riser per lb. of catalyst and 4 to 20 lb. per hour of catalyst per lb. of catalyst in the reactor may be carried up the riser. The catalyst passes into a distribution vessel 23 having small openings 34 in its convex upper surface. Regeneration gas is supplied through an annular pipe 36 also provided with openings, which surrounds the distributer. The regenerator generally contains 2 to 5 times as much material as the reactor and is of larger cross-section. Regeneration takes place at 700 DEG to 1200 DEG F., usually 1000 DEG to 1150 DEG F. with air. The catalyst passes after regeneration into the symmetrically placed standpipes 21 and 22 also equipped with expansion joints, which terminate preferably somewhat above the riser but sufficiently low to avoid immediate entry of the regenerated catalyst into the stripping zone, and are regulated by plug valves 29 and 30. Preferred sizes and proportions of apparatus are described. Reference has been directed by the Comptroller to Specification 767,769.