Abstract The method of regenerating a granular, foraminous nickelaluminum catalyst which has been activated by removing about 2-50 percent of the aluminum from a nickel-aluminum alloy originally containing about 25-60 percent by weight of nickel and about 4075 percent by weight of aluminum and which has lost activity through use as a fixed-bed catalyst in the preparation of butane1,4-diol by the continuous hydrogenation of an aqueous mixture containing about 30-80 percent by weight of water and diol selected from the group consisting of 2-butyne-1,4-diol and 2butene-1,4-diol at a temperature of about 60-150*C., a hydrogen pressure of about 100-400 atmospheres and a superficial gas velocity of at least about 0.5 foot per minute which comprises washing the catalyst with a wash medium consisting essentially of about 90-99 percent by weight of water and about 1-10 percent by weight of a polycarboxylic acid selected from the group consisting of citric and succinic acids. Such catalysts can be reactivated by first washing with the above polycarboxylic acid solution and then treating with a dilute aqueous alkali metal hydroxide solution, thereby removing additional aluminum from the alloy. Catalysts which have become fouled through use of an aqueous feed mixture containing dissolved calcium ions can be regenerated by washing the catalyst with the above polycarboxylic acid solution until the wash liquid no longer becomes saturated with calcium ions.
The method of claim 1 in which the catalyst is first washed with polycarboxylic acid for at least 6 hours at a temperature of less than 40* C., and then is reactivated by treating with a 0.1-10 percent by weight aqueous alkali metal hydroxide solution at a temperatuRe not in excess of 50* C., thereby removing an additional amount of aluminum from the alloy.
Claim 2
Dependent Claim
46 words
The method of claim 2 in which the hydrogenation is carried out at a temperature of 60*-150* C. under a hydrogen partial pressure of 100-400 atmospheres and a superficial gas velocity of at least 0.5 foot per minute, measured as the hydrogen leaves the catalyst bed.
Claim 3
Dependent Claim
51 words
The method of claim 3 in which the aqueous mixture fed to the hydrogenation reaction contains 20-70 percent by weight of butynediol and 30-80 percent by weight of water and the pH of the hydrogenation reaction medium is adjusted so as to maintain a pH of 6.5-8 at the reactor exit.
Claim 4
Dependent Claim
18 words
The method of claim 3 in which the wash medium contains 2-6 percent by weight of citric acid.
Claim 5
Dependent Claim
29 words
The method of claim 5 in which the aqueous mixture fed to the hydrogenation reaction contains 35-65 percent by weight of butynediol an 40-65 percent by weight of water.
Claim 6
Dependent Claim
22 words
The method of claim 6 in which the catalyst is washed for at least 12 hours with citric acid at ambient temperature.
Claim 7
Dependent Claim
22 words
The method of claim 7 in which the alkali metal hydroxide solution is a 1-5 percent by weight aqueous sodium hydroxide solution.
Claim 8
Dependent Claim
57 words
The method of claim 1 in which the aqueous mixture fed to the hydrogenation reaction contains 1-1,000 parts per million of calcium ions, and the acid wash is carried out at a temperature of less than 40* C. by a series of washings which are continued until the wash liquid no longer becomes saturated with calcium ions.
Claim 9
Dependent Claim
45 words
The method of claim 9 in which the acid wash is carried out using a 2-6 percent by weight citric acid solution at ambient temperature and is continued until the calcium ion concentration in the wash liquid levels off below about 500 parts per million.