GB748777A - Improvements in or relating to process for rejuvenating platinum and/or palladium hydroforming catalysts - Google Patents

Abstract

In a cyclic hydrocarbon hydroforming process, platinum- or palladium-containing catalyst is rejuvenated by oxidation with a gas having an oxygen partial pressure of at least 0.4 atmosphere at a temperature above about 825 DEG F. and below the sintering temperature of the catalyst (see Group III). If desired, the treatment may be preceded by burning carbonaceous matter from the catalyst with an oxygen-containing gas at a temperature within the same range. Before re-use the catalyst is treated with a reducing gas, e.g. in the hydroformer. The rejuvenation procedure is especially suitable for use when hydroforming is carried out at a low pressure, e.g. below 350 lbs. per square inch. Apparatus is shown diagrammatically for fluidized and fixed bed operation. In the fixed bed process four reactors are used and each is regenerated in turn; the feed is vacuum purged to remove gases and water, and the hydrogen separated from the reaction products may be purified by contact with an amine solution, silica gel, charcoal, or activated carbon to remove water, hydrogen sulphide, and hydrocarbons before recycling. Reference is also made to a moving bed process. In examples a mid-continent virgin naphtha of boiling range 200-360 DEG F. is hydroformed at 840 DEG -960 DEG F., 200 lbs. per square inch gauge pressure, a liquid hourly space velocity of 2, and a recycle gas rate of 5000 cubic feet per barrel of feed.ALSO:Platinum- or palladium-containing catalyst, which has become deactivated by use in a hydrocarbon hydroforming process, is rejuvenated by treatment, at a temperature above about 825 DEG F and below the sintering temperature of the catalyst, with a gas having an oxygen partial pressure of at least 0.4 atmosphere. The treatment may take place at 1000 DEG -1200 DEG F. for a period of 0.1-36 hours with air, oxygen, or oxygen- <PICT:0748777/III/1> enriched air, air may be used at the hydroforming pressures (50-350 lbs. per sq. in.) or oxygen at atmospheric pressure. If desired the treatment may be preceded by burning carbonaceous matter from the catalyst with an oxygen-containing gas at a temperature within the same range, for example with a gas containing 0.5-2 per cent by volume of oxygen (e.g. air diluted with flue gas or nitrogen) for 0.2-5 hours at 825 DEG -1300 DEG F. in order to reduce the carbon content to less than 0.1 per cent. The rejuvenation may form part of a cyclic hydroforming process in which, before re-use, the catalyst is treated with a reducing gas, e.g. in the hydroformer. As shown in Fig. 2, the feed is vaporized in heater 111 and introduced through line 112 into hydroformer 114 containing a fluidized bed of catalyst; recycle gas containing hydrogen enters at 117, 118, 119 and hydroforming is carried out at a temperature of 850 DEG -1000 DEG F. and a pressure of 50-350 lbs. per sq. in. Reaction products leave at 121 and catalyst is continuously withdrawn through riser 122 and hopper 123 into regenerator 126 where it flows in countercurrent with flue gas containing about 2 per cent oxygen at the temperature and pressure of the hydroformer; the temperature in regenerator 126 is controlled by indirect cooling or by regulating the flow rate, temperature, or oxygen content of the gas; catalyst is returned to the hydroformer through lines 132, 133. A portion of the catalyst is diverted through line 136 to rejuvenator 135 where it is treated with air, oxygen, or oxygenenriched air at a temperature of 1000 DEG -1200 DEG F. for 1-4 hours; hydrocarbon may be added to the gas used to raise the temperature. Rejuvenated catalyst is returned to the hydroformer via cooler 142. The invention may also be applied to a hydroforming process in which four fixed bed reactors are used (Fig. 1, not shown). The naphtha feed is vacuum purged to remove gases and water and then passed through three reactors in series while the fourth is being regenerated; heaters are included before each reactor. The hydrogen separated from the reaction products may be purified by contact with an amine solution, silica gel, charcoal, or activated carbon to remove water, hydrogen sulphide, and hydrocarbons before recycling. Regeneration is effected by passing recycle gas and flue gas in succession through the bed, and then adding air to the flue gas to burn off the carbon; when the activity of the catalyst falls it is treated with air, which may contain a fuel gas, for 1-5 hours, then purged free from oxygen with flue gas, and finally reduced with hydrogen or recycle gas. The platinum or palladium catalyst may be supported on alumina which may also contain silica, fluoride, chloride, boria, titania, chromium, vanadium, or an oxide of phosphorus. It may be prepared by mixing an alumina hydrosol or a suspension of alumina with a mixture of aqueous chloroplatinic acid or platinum chloride and ammonium polysulphide solution and drying; alternatively alumina gel (prepared as in Specification 552,053), alumina monohydrate or sintered alumina may be mixed with a solution of chloroplatinic acid, platinum tetrachloride, or a colloidal suspension of platinum sulphide. Catalyst may also be prepared as described in Specifications 657,565 and 686,641. Example 1 describes the preparation of a catalyst consisting of platinum, titanium, and alumina, and Examples 2 and 3 the preparation of platinum or alumina catalysts.