Summary of the invention
For solving above-mentioned one or more problem, the invention provides a kind of employing anion regulation and control preparation Pd/ α-Al
2o
3the preparation method of catalyst, the steps include:
(1) precursor of the precursor of palladium and auxiliary agent is dissolved in the solution of certain pH value and makes maceration extract;
(2) by the α-Al through calcination process
2o
3ball adds in the prepared maceration extract of step (1), in maceration extract, adds appropriate ion salt, then at 40~60 ℃ standing 6~24h;
(3) by the α-Al after step (2) processing
2o
3ball, puts into baking oven dry 12~24h at 100~200 ℃;
(4) α-Al after step (3) processing
2o
3ball, fully washs by deionized water;
(5) α-Al after washing
2o
3ball is fully dry in baking oven;
(6) dry rear gained catalyst precarsor is in hydrogen or carbon monoxide atmosphere, and 4~the 8h that reduces at 150~400 ℃ obtains catalyst of the present invention,
Its active component of described catalyst is the palladium of high dispersive form, α-Al that carrier is inertia
2o
3ball, is mainly used in the reaction of CO oxidative coupling synthesizing dimethyl oxalate, has excellent catalytic activity and selective.
That is to say, the invention provides a kind of method of carrying out Kaolinite Preparation of Catalyst by add specific ion salt and suitable content in maceration extract, the prepared catalyst of the method significantly changes the distribution of the dispersed of noble metal active component and noble metal active component, thereby guarantees to be issued to good catalytic activity effect in the condition of extremely low noble metal dosage.The present invention be take palladium bichloride as palladium source, the ball-aluminium oxide of take (has certain mechanical strength as carrier, diameter range is at 1-10mm), in preparation, adopt the mode of adding ion salt that active component palladium is loaded on alumina support with the state of more optimizing, form a kind of efficient, low heat release and stable catalyst for synthesizing oxalic ester.
The specific embodiment
The invention discloses a kind of employing anion regulation and control preparation Pd/ α-Al
2o
3the preparation method of catalyst, the steps include:
(1) precursor of the precursor of palladium and auxiliary agent is dissolved in the solution of certain pH value and makes maceration extract;
(2) by the α-Al through calcination process
2o
3ball adds in the prepared maceration extract of step (1), in maceration extract, adds appropriate ion salt, then at 40~60 ℃ standing 6~24h;
(3) by the α-Al after step (2) processing
2o
3ball, puts into baking oven dry 12~24h at 100~200 ℃;
(4) α-Al after step (3) processing
2o
3ball, fully washs by deionized water;
(5) α-Al after washing
2o
3ball is fully dry in baking oven;
(6) dry rear gained catalyst precarsor is in hydrogen or carbon monoxide atmosphere, and 4~the 8h that reduces at 150~400 ℃ obtains catalyst of the present invention,
Its active component of described catalyst is the palladium of high dispersive form, α-Al that carrier is inertia
2o
3ball, is mainly used in the reaction of CO oxidative coupling synthesizing dimethyl oxalate, has excellent catalytic activity and selective.
From the 100h study on the stability curve map of Fig. 1, can find, the yield of catalyst is substantially consistent in 100h evaluation procedure, illustrates that the stability of catalyst is better.The dispersion that can observe catalyst from the TEM photo of Fig. 2 and Fig. 3 is more even, and grain size is less.From Fig. 4, to 9 observations, can find, the active component of catalyst is at the certain spatial distribution state of having of carrier inside, and the difference of distribution also can cause that the performance of catalyst changes.
Comprehensive, catalyst activity component high degree of dispersion prepared by the inventive method, active component is specific spatial distribution state in carrier granular, catalyst finished particle diameter 1-10mm, and in adaptive response technique, catalyst has many-sided requirements such as certain hardness and caloic heat transfer.The prepared catalyst noble metal dosage of this preparation method is low and thermal discharge is little, under lower bed temperature condition, not only guaranteed the stability of catalyst activity component, also guarantee higher activity and the space-time yield of dimethyl oxalate simultaneously, improved the utilization rate of noble metal.
In another embodiment, the precursor of the palladium described in step (1) adopts: any one or more any combination in palladium bichloride, palladium nitrate, palladium and acetylacetone,2,4-pentanedione, in final gained catalyst, the content of palladium is counted 0.05%~1.0% of vehicle weight with palladium element.
In another embodiment, the ion salt adding in step (2) adopts: one or more in chlorate, sulfate and nitrate.
In another embodiment, described ion salt adopts NaCl, NaBr, Na
2sO
4.
In another embodiment, the concentration of described ion salt is 0~200g/L.
In another embodiment, described in step (1), solution is the acid solutions such as hydrochloric acid solution, salpeter solution, and its pH is between 0~6.
With example, further illustrate the present invention below, but the invention is not restricted to example.
Example 1:
(1) preparation of catalyst
0.075g palladium bichloride and 0.40g auxiliary agent ferric nitrate are dissolved in the hydrochloride buffer that pH=1.1 volume is 15ml, 15g alumina balls through calcination process are added in 15ml maceration extract, place at ambient temperature 12h, then put into drying box dry 12h at 100 ℃, then at 150 ℃, be dried 12h; At 60 ℃, with 5 times of volumes of deionized water washing 10 times, every minor tick 2~3h, outwells after the solution soaking for the last time, put into 100 ℃ of baking ovens continuation and be dried 12h, by gained load the alumina balls of palladium pass into CO: N
2be that the gas of 1: 4 reduces 4h at 150~400 ℃, obtain catalyst finished product.Pd content is wherein 0.3% of carrier quality, and auxiliary agent iron content is 0.6% of carrier quality.
(2) performance evaluation and life-span are investigated
Adopt fixed bed reactors, reaction tube diameter 15mm, two sections of temperature controls.Add catalyst 10ml (stacking volume), upper strata is inertia porcelain bead rectification preheating, with 150ml/min, 100ml/min, 150ml/min, pass into carbon monoxide, methyl nitrite, nitrogen respectively, control heating-up temperature 120-140 ℃, at bed temperature 130-165 ℃, react and investigate yield, stable reaction started timing after one hour, successive reaction two hours, obtain dimethyl oxalate product 13.6g, amounting to yield is 680g (DMO)/l (cat) h.
Example 2:
In example 1, the ion salt quality adding in catalyst preparation is respectively: 0g, 0.5g, 1g, 1.5g, 2g, 2.5g, make that the concentration of ion salt in maceration extract is 0,33.3g/L, 66.7g/L, 100g/L, 130g/L, 167g/L, i.e. cost example sample M0-M5.
Performance evaluation condition is with example 1, and dimethyl oxalate yield is respectively as following table:
M4 catalyst has been carried out to the life-span of 100h and investigated, active situation is shown in Fig. 1.
Sample characterization:
By TEM picture (seeing Fig. 2~3) and section optical microscope photograph (seeing Fig. 4~9), can find out, anion add impregnating depth and the thickness that has changed catalyst sample active component, thereby affect the degree of decomposition of catalyst to the selective and methyl nitrite of dimethyl oxalate.Yet test (seeing the following form) by decentralization, find, the introducing of anion does not cause the significant change of decentralization.
Sample title |
Metal?Dispersion(%) |
Crystallite?Size(nm) |
M0 |
28.5320 |
3.9254 |
M1 |
28.0127 |
3.9981 |
M2 |
27.9956 |
4.0006 |
M3 |
28.3258 |
3.9541 |
M4 |
28.4650 |
3.9346 |
M5 |
28.3320 |
3.9531 |
Above disclosed is only preferred embodiment of the present invention, certainly can not limit with this interest field of the present invention, and the equivalent variations of therefore doing according to the claims in the present invention, still belongs to the scope that the present invention is contained.