Background technology
Supported palladium/carbon catalyst is mainly used in the selective hydrogenation of unsaturated compounds, be particularly useful for the crude terephthalic acid process for refining, carboxyl benzaldehyde impurity such as (being called for short 4-CBA) is carried out by changing other compound behind the hydrogenation in the crude terephthalic acid, just available crystalline method separate purifies.Because palladium/carbon catalyst usually adopts single active constituent, its improvement research is concentrated on the structure and the distribution situation of metal Pd on carrier of carrier always, and this can produce very big influence to the performance of catalyzer really.Because hydrogenation reaction is to carry out on the surface of metal Pd, generally speaking, for the identical catalyzer of metal Pd charge capacity, the dispersity of its metal Pd is higher, crystallite (grain-size is less than the 25 nanometers) content that is the metal Pd of load in the catalyzer is higher, activity of such catalysts is better, and work-ing life is also longer.
If directly will contain Pd compound (as chlorine palladium acid sodium or Palladous chloride) loads on the gac, activated carbon surface can the very thin glossiness metal Pd layer of very fast appearance, this mainly is because activated carbon surface contains just like reduction groups such as aldehyde radical, unbound electrons, very easily make the Pd ion be reduced into the non-valent metal Pd, the dispersity of metal Pd is very low in the catalyzer that makes like this.Experience is in the past told us, and before the reduction operation, the Pd ion that will contain in the steeping fluid of Pd compound is transformed into the effect that insoluble compound can be obtained.As at room temperature the water-soluble cpds hydrolysis of Pd being generated insoluble Pd (OH)
2Or PdOH
2O, back loading and then with reductive agents such as aldehyde, sodium formiate, glucose, formic acid or hydrogen reduction, can prevent migration and the grain growth of Pd on gac, as U.S. Pat 3,138,560 are introduced.But this steeping fluid stability that contains the Pd compound is very poor, and this has just improved the requirement of catalyst preparation process relatively.U.S. Pat 4; 476; the steeping fluid that contains the Pd compound is prepared in 242 propositions with organic solvents such as methyl alcohol or pyridines; it is said that this is also very effective to the migration and the grain growth that prevent Pd; but production process use methyl alcohol or pyridine are this in human body harmful's organic compound, all are disadvantageous from ring environment protection or labour protection.
Summary of the invention
The invention provides a kind of preparation method who is used for the palladium/carbon catalyst of selective hydrogenation, its technical problem to be solved is that metal Pd has higher dispersity in the catalyzer that obtains, content of crystallite is higher, and preparation process requires simply, and the raw material of employing is easy to environmental protection treatment.
Below be the technical scheme that the present invention solves the problems of the technologies described above:
A kind of preparation method who is used for the palladium/carbon catalyst of selective hydrogenation, catalyzer is a carrier with particle or pressed active carbon, supported active component metal Pd, the content of metal Pd is 0.2~5wt% in the catalyzer, the preparation method may further comprise the steps successively: 1) carrier active carbon carries out pickling, the acid concentration of pickle solution is 0.1~5N, and a kind of in hydrochloric acid, nitric acid or the phosphoric acid taken from acid; 2) carrier active carbon is washed with water to neutral after drying; 3) carrier active carbon is with halogen-containing ionic solution immersion, and the halogen ion concentration of infiltrate is 0.01~0.5N, and the infiltrate consumption is 0.1~3.0 times of gac saturated extent of adsorption, and infiltrating time is 2~24 hours; 4) the drying support gac is removed moisture; 5) with the solution impregnation that contains the Pd compound or spray carrier active carbon and make and contain that Pd is compound loaded to obtain catalyst precursor in gac, catalyst precursor reduces processing with reductive agent after aging, makes Pd in the Pd compound be reduced to metal Pd and promptly gets catalyst prod.
Halide-ions described in the above-mentioned steps 3 is preferably Br
-1Or I
-1, halide-ions can be preferably the halogenide of potassium from alkali-metal halogenide usually.The described Pd of the containing compound of step 5 is generally any in the title complex of the subsalt of the halogenide of taking from Pd, acetate, nitrate, the acid of chlorine palladium, the acid of chlorine palladium or palladium ammonia, is preferably the subsalt of acid of chlorine palladium or the acid of chlorine palladium.The described reductive agent of step 5 is generally takes from any in formic acid, sodium formiate, formaldehyde, hydrazine hydrate, glucose or the hydrogen, is preferably sodium formiate or hydrazine hydrate.
In aforesaid method, step 1,2,4,5 and existing general palladium/carbon catalyst preparation method basic identical, and known by those skilled in the art, described below only is that the present invention recommends.
Select suitable gac for use, remove the dust and surface porosity part of carbon surface absorption after, in the washing still, carry out pickling.Extremely neutral with deionized water wash after the pickling, the purpose of pickling is to adjust the structure of activated carbon surface functional group.
Get and contain Pd compound water and be mixed with the dipping glue, concentration is generally 0.01~20wt%, and the pH value of regulating the dipping glue is 4~6.Adopt methods such as dipping or sprinkling that Pd is carried on the carrier then, the method for recommendation is a spraying, and spraying time was at least 5 minutes.Then catalyst precursor was worn out 1~24 hour in air.
Catalyst precursor after aging is handled with the reductive agent reduction, reductive agent preferable formic acid sodium, and its toxicity is little, and the three wastes are few, help environmental protection, and cheap.Reduction temperature is 0~200 ℃, and the best is 50~120 ℃.The consumption of reductive agent depends on the dosage of active constituent Pd, is generally normal 1~10 times of reduction reaction, is preferably 2~5 times, and the recovery time is 1~10 hour, and the best is 1~4 hour.
Key of the present invention has been to increase step 3 wherein, and carrier active carbon with halogen-containing ionic solution immersion, makes halide-ions be adsorbed in activated carbon surface after pickling.Because halide-ions can be distributed in activated carbon surface very equably, and halide-ions and palladium and activated carbon surface all have affinity interaction power preferably, this has just increased the grappling effect of activated carbon surface to palladium, thereby the migratory movement that can reduce palladium is to stop or to delay the grain growth of palladium metal.
Compared with prior art, the invention has the advantages that metal Pd has higher dispersity in the catalyzer that makes, content of crystallite is higher, shows active high, long service life on use properties, and the step that increases in the preparation process is very simple, and the raw material of employing is easy to environmental protection treatment.
Below will the invention will be further described by specific embodiment, in an embodiment:
The measuring method of dispersity:
With pack into the sample hose of chemisorption instrument of catalyzer, use nitrogen purging, switch hydrogen, temperature programming to 200 ℃ keeps half an hour.After half an hour, air is switched to nitrogen, purge half an hour, advance pure hydrogen with quantity tube at last, note the milliliter number that at every turn advances hydrogen, by calculating the total milliliter of number that hydrogen reduces.
Method of calculation:
V inhales: the hydrogen adsorption amount; M (Pd): the measuring method of the nucleidic mass content of crystallite of palladium:
The palladium metal particle diameter records by X-fluorescence spectrophotometer and x-ray diffractometer (XRD).
The activity rating of catalyst condition:
Catalyst consumption: 2.0g
Thick p-Xylol amount: 30.0g
4-CBA amount: 1.0g
Reaction pressure: 70 kilograms
Hydrogen partial pressure: 5.0 kilograms
Reaction times: 1.0 hours
Temperature of reaction: 270 ℃
Embodiment
[embodiment 1]
With 100 grams, 4~8 orders, specific surface 800~1200m
2The cocoanut active charcoal of/g washs with the nitric acid of 0.4N, and wash temperature is 80 ℃, washes with water then to neutrality, and drying is 2~8 hours under 120 ℃.With Potassium Bromide and water preparation Br
-Concentration is the infiltrate of 0.01N, incipient impregnation gac 2~24 hours, and 80~120 ℃ times dry 2~8 hours are standby.
Preparation conversion palladium content is 40 milliliters of the chlorine palladium acid solutions of 0.5wt% then, about 1.0 milliliters of the tartrate that adds 2wt% therein, with alkali pH value is adjusted between 4~6 again, make it form the palladium glue, after stablizing 10~200 minutes, the palladium glue is sprayed on the above-mentioned treated gac obtains catalyst precursor.Catalyst precursor after the aging night sodium formiate 20 grams and pure water 200 grams with 5wt% be mixed with reduced liquid, catalyst precursor is immersed in the reduced liquid 2~4 hours, then with the extremely neutral catalyst prod that gets of pure water washing.
[embodiment 2]
With Potassium Bromide and water preparation Br
-Concentration is the infiltrate of 0.05N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 3]
With Potassium Bromide and water preparation Br
-Concentration is the infiltrate of 0.2N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 4]
With Potassium Bromide and water preparation Br
-Concentration is the infiltrate of 0.5N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 5]
With potassiumiodide and water preparation I
-Concentration is the infiltrate of 0.01N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 6]
With potassiumiodide and water preparation I
-Concentration is the infiltrate of 0.05N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 7]
With potassiumiodide and water preparation I
-Concentration is the infiltrate of 0.2N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[embodiment 8]
With potassiumiodide and water preparation I
-Concentration is the infiltrate of 0.5N, incipient impregnation gac 2~24 hours, and all the other are with embodiment 1.
[comparative example]
With 100 grams, 4~8 orders, specific surface 800~1200m
2The nitric acid washing of the cocoanut active charcoal usefulness 0.4N of/g, wash temperature is 80 ℃, washes with water then to neutrality, and is standby in 120 ℃ times dry 2~8 hours.
Preparation conversion palladium content is 40 milliliters of the chlorine palladium acid solutions of 0.5wt% then, about 1.0 milliliters of the tartrate that adds 2wt% therein, with alkali pH value is adjusted between 4~6 again, make it form the palladium glue, after stablizing 10~200 minutes, the palladium glue is sprayed on the above-mentioned treated gac obtains catalyst precursor.Catalyst precursor after the aging night sodium formiate 20 grams and pure water 200 grams with 5wt% be mixed with reduced liquid, catalyst precursor is immersed in the reduced liquid 2~4 hours, then with the extremely neutral catalyst prod that gets of pure water washing.
Measure the dispersity and the content of crystallite of the palladium metal of the live catalyst product load that the various embodiments described above and comparative example obtain, and catalyzer is carried out activity rating.The aging rear catalyst that catalyzer is obtained after 100 hours in 300 ℃ of roastings in nitrogen atmosphere is then measured the dispersity and the content of crystallite of the palladium metal of catalyst cupport once more, and catalyzer is carried out activity rating.The results are shown in Table 1.
Table 1.
| Pd content (wt%) | Dispersity (%) | Content of crystallite (%) | Transformation efficiency (%) |
Before aging | After aging | Before aging | After aging | Before aging | After aging |
Embodiment 1 | ????0.5 | ?27 | ????26 | ??80 | ??77 | ????99.9 | ????99.8 |
Embodiment 2 | ????0.5 | ?29 | ????28 | ??84 | ??82 | ????99.9 | ????99.8 |
Embodiment 3 | ????0.5 | ?31 | ????30 | ??85 | ??82 | ????99.9 | ????99.8 |
Embodiment 4 | ????0.5 | ?32 | ????30 | ??86 | ??85 | ????100.0 | ????99.8 |
Embodiment 5 | ????0.5 | ?28 | ????26 | ??81 | ??79 | ????99.9 | ????99.8 |
Embodiment 6 | ????0.5 | ?31 | ????29 | ??86 | ??83 | ????99.9 | ????99.8 |
Embodiment 7 | ????0.5 | ?33 | ????30 | ??87 | ??85 | ????100.0 | ????99.8 |
Embodiment 8 | ????0.5 | ?33 | ????30 | ??87 | ??85 | ????100.0 | ????99.8 |
Comparative example | ????0.5 | ?14 | ????8.1 | ??70 | ??60 | ????99.8 | ????96.5 |