CN104353465A - Catalyst for formaldehyde catalytic oxidation and preparation method of catalyst - Google Patents

Abstract

The invention discloses a catalyst for formaldehyde catalytic oxidation and preparation method of the catalyst. The catalyst for formaldehyde catalytic oxidation is of a nuclear and shell structure; a nuclear is Co3O4, and a shell is CeO2; the ratio of the nuclear to the shell is calculated according to the mole percent of Co and Ce metal atoms; Co is 95.55-97.60 percent, and Ce is 2.40-4.45 percent. According to the preparation method, Co3O4 catalyst particles are prepared by a parallel flow coprecipitation method, and the surfaces of the Co3O4 catalyst particles are loaded with a CeO2 shell layer. The catalyst for formaldehyde catalytic oxidation can be used for enabling the conversion rate of formaldehyde to be 100 percent under room temperature of 25 DEG C; meanwhile, the catalyst is extremely high in catalysis and CO2 selectivity.

Description

The Catalysts and its preparation method that a kind of formaldehyde through catalytic oxidation is used

Technical field

The present invention relates to the Catalysts and its preparation method that a kind of formaldehyde through catalytic oxidation is used, belong to environmental catalysis technical field.

Background technology

Eliminating carbaldehyde Method has a variety of, as absorption method, chemical reaction method etc.Wherein, under temperate condition, catalytic oxidation is considered to a kind of effective ways of thorough elimination formaldehyde: indoor HCHO is fully oxidized as H under the reaction condition of gentleness ₂o and CO ₂, become the focus that researcher pays close attention at present.

Since last century end, to carry out a large amount of work about indoor formaldehyde through catalytic oxidation reaction and catalyst system and catalyzing both at home and abroad.Its catalytic active component is generally noble metal (Pt, Au and Pd).Due to its popularity of price limit of the costliness of these noble metals.

Therefore, develop transition-metal catalyst and there is certain practical significance.Compare with precious metal catalyst system, Co ₃o ₄catalyst is due to cheap, and the advantages such as reaction temperature is low, high catalytic activity show powerful application potential in CO low-temperature oxidation, but Co ₃o ₄catalyst but rarely has report at formaldehyde low-temperature oxidation area research.

Summary of the invention

An object of the present invention is in order to by Co ₃o ₄the catalyst that catalyst application provides in formaldehyde low-temperature catalytic oxidation.

Two of object of the present invention is the preparation method providing a kind of above-mentioned formaldehyde through catalytic oxidation used catalyst.

know-why of the present invention

Can be found by literature survey, body phase Co ₃o ₄belong to spinel structure, have the Co of eight-coordinate simultaneously ³⁺with the Co of four-coordination ²⁺, just because of the crystalline form of its uniqueness and the attribute that appraises at the current rate, show comparatively Strong oxdiative ability, it shows unique catalytic performance and enjoys concern both domestic and external in CO low-temperature catalytic oxidation in recent years.But its research in formaldehyde low-temperature oxidation but rarely has report.

At Co ₃o ₄middle introducing CeO ₂auxiliary agent, not only plays effect that is stable and that optimize to catalyst structure, and CeO ₂and Co ₃o ₄component has very strong cooperative effect, makes CeO ₂strong oxygen stores the oxidability that ability greatly enhances catalyst.

The present invention is with Co ₃o ₄catalyst, as key component, wraps up CeO at catalyst surface ₂shell, not only can stablize Co ₃o ₄form, stops its particle to be reunited in activation process.And the core-shell structure copolymer Rotating fields of its uniqueness can reach following effect: 1) regulate Co ₃o ₄interior Co ²⁺/ Co ³⁺ratio, thus improve Co ₃o ₄oxidability; 2) in course of reaction, CeO ₂the oxidation activity of catalyst can also be improved further by storing oxygen; 3) improve the anti-caking power of catalyst, keep the decentralization of active component; 4) effectively suppress the formation of surface carbonate, maintain the activity of catalyst; 5) Co is made ₃o ₄the formaldehyde of the non-complete oxidation in activated centre is through CeO ₂the outside diffusion process of film in there is secondary oxidation and improve oxidation efficiency further.

technical scheme of the present invention

The catalyst that formaldehyde through catalytic oxidation is used, be core, shell structure, described core is Co ₃o ₄, shell is CeO ₂, the ratio of nucleocapsid presses the molar percentage calculating of Co, Ce metallic atom, specific as follows:

Co 95.55–97.60%

Ce 2.40–4.45%。

First the preparation method of the catalyst that above-mentioned a kind of formaldehyde through catalytic oxidation is used, namely adopt co-precipitation method to prepare Co ₃o ₄catalyst granules, then at Co ₃o ₄the area load CeO of catalyst granules ₂shell, its preparation process specifically comprises the steps:

(1), by the Co (NO of 1mol/L ₃) ₂the Na of solution I and 0.5mol/L ₂cO ₃solution II by volume ratio is that 1:3.5 mixes, and the often amount of dripping that controls is that the mixed liquor of gained is dropwise added drop-wise to the Na that 0.5mol/L is housed by 0.05 – 0.07mL ₂cO ₃in the beaker of solution III, controlling speed of agitator in dropping process is 200 – 300r/min, temperature 60 C, pH value is controlled to drip within the scope of 9.4-9.8 to terminate by pH meter on-line monitoring, wait to drip and terminate, suction filtration after ageing 1h, after the filter cake distilled water of gained washs 6 times, then dries 12h by filter cake through 120 DEG C, then in 300 DEG C of roasting 4h, obtain powder cobaltosic oxide, then sieve, obtaining granularity is 200 – 250 object cobaltosic oxide powders;

The Na of the above-mentioned 0.5mol/L be equipped with in beaker ₂cO ₃the amount of solution III according to the stirring-head of mechanical agitator near but not encounter at the bottom of beaker and the Na of 0.5mol/L can be touched ₂cO ₃solution III is as the criterion;

(2), in concentration be that to add the granularity prepared by step (1) in the cerous nitrate aqueous solution IV of 0.035-0.066mol/L be 200 – 250 object powder cobaltosic oxides, and constantly stir and form suspension, then under 60 DEG C of conditions with the Na of 0.5mol/L ₂cO ₃aqueous solution V regulates suspension pH value to be 7.0, suction filtration after ageing 2h, and the filter cake of gained spends deionized water 6 times, and finally successively at 120 DEG C of dry 12h, roasting 4h at 350 DEG C, obtains the catalyst that formaldehyde through catalytic oxidation is used;

Above-mentioned concentration used is the cerous nitrate aqueous solution IV of 0.035-0.066mol/L and the amount of 200-250 object cobaltosic oxide powder, and by mole% calculating, namely Co:Ce is 95.55 – 97.60%:2.40 – 4.45%.

beneficial effect of the present invention

The catalyst that a kind of formaldehyde through catalytic oxidation of the present invention is used, owing to adopting transition metal oxide Co ₃o ₄as the core of catalyst, CeO ₂for shell, therefore its cost sharply reduces compared to noble metal catalyst.

Further, the catalyst that a kind of formaldehyde through catalytic oxidation of the present invention is used, due to CeO ₂for shell, make formaldehyde transform required reaction temperature completely and reduce 85 – 100 DEG C, namely room temperature 25 DEG C just can make the conversion ratio of formaldehyde reach 100%, and a kind of formaldehyde through catalytic oxidation of the present invention catalyst used can continue at least 48h operates continuously, the conversion ratio of formaldehyde reaches 100%, simultaneously CO ₂selectively be stabilized in 100%; As continuous running 60h, the conversion ratio of formaldehyde still can reach 99.2%, and CO ₂selectively reduced by only 0.80%, show thus, the good stability of catalyst tool that a kind of formaldehyde through catalytic oxidation of the present invention is used and CO ₂selective.

Further, the preparation method of the catalyst that a kind of formaldehyde through catalytic oxidation of the present invention is used, its preparation method is simple, be easy to operation, and catalyst performance repeatability is relatively good, easily accomplishes scale production.

Detailed description of the invention

Below by specific embodiment, the present invention is described further, but does not limit the present invention.

Used in various embodiments of the present invention:

Miniature quartz reaction tube fixed bed reactors (LW4, Wuxi drawing instrument factory);

Polyformaldehyde glass bubbler;

Carbon molecular sieve chromatographic column, Ramiin, GC2060, the sensitive Instrument Ltd. in Shanghai;

Nickel reburner, the sensitive Instrument Ltd. in Shanghai.

embodiment 1

The catalyst that formaldehyde through catalytic oxidation is used, be core, shell structure, described core is Co ₃o ₄, shell is CeO ₂, the ratio of nucleocapsid presses the molar percentage calculating of Co, Ce metallic atom, specific as follows:

Co 97.60%

Ce 2.40%。

First the preparation method of the catalyst that above-mentioned a kind of formaldehyde through catalytic oxidation is used, namely adopt co-precipitation method to prepare Co ₃o ₄catalyst granules, then at Co ₃o ₄the area load CeO of catalyst granules ₂shell, its preparation process specifically comprises the steps:

(1), by 125mL concentration be the Co (NO of 1mol/L ₃) ₂solution I and 437.5mL concentration are the Na of 0.5mol/L ₂cO ₃solution II by volume ratio is that 1:3.5 mixes, and the often amount of dripping that controls is that the mixed liquor of gained is dropwise added drop-wise to the Na that 30mL concentration is 0.5mol/L is housed by 0.05 – 0.07mL ₂cO ₃in the beaker of solution III, controlling speed of agitator in dropping process is 200 – 300r/min, temperature 60 C, pH value is controlled to drip within the scope of 9.4-9.8 to terminate by pH meter on-line monitoring, wait to drip and terminate, suction filtration after ageing 1h, after the filter cake distilled water of gained washs 6 times, then dries 12h by filter cake through 120 DEG C, then in 300 DEG C of roasting 4h, obtain powder cobaltosic oxide, then sieve, obtaining granularity is 200 – 250 object cobaltosic oxide powders;

The Na of the above-mentioned 0.5mol/L be equipped with in beaker ₂cO ₃the amount of solution III according to the stirring-head of mechanical agitator near but not encounter at the bottom of beaker and the Na of 0.5mol/L can be touched ₂cO ₃solution III is as the criterion;

(2), 0.760g six nitric hydrate cerium salt is dissolved in the cerous nitrate aqueous solution IV that the concentration obtained in 50mL water is 0.035mol/L, adding granularity prepared by 5g step (1) is wherein 200 – 250 object powder cobaltosic oxides, and constantly stir formation suspension, under 60 DEG C of conditions, then use the Na of 0.5mol/L ₂cO ₃aqueous solution V regulates suspension pH value to be 7.0, suction filtration after ageing 2h, and the filter cake of gained spends deionized water 6 times, and finally successively at 120 DEG C of dry 12h, roasting 4h at 350 DEG C, obtains the catalyst A that formaldehyde through catalytic oxidation is used;

Above-mentioned concentration used is the cerous nitrate aqueous solution IV of 0.035mol/L and the amount of 200-250 object cobaltosic oxide powder, and by mole% calculating, namely Co:Ce is 97.60%:2.40%.

application Example 1

By catalyst A compressing tablet used for the formaldehyde through catalytic oxidation of above-described embodiment 1 gained and to be crushed to 40-60 order for subsequent use.

Being fixed to internal diameter in miniature quartz pipe fixed bed reactors after mixing with isopyknic quartz sand with the catalyst A (40-60 order) that the formaldehyde through catalytic oxidation of 0.5g embodiment 1 gained is used is the interlude of the reaction tube of 6mm, is the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde glass bubbler (heating water bath 36 DEG C) to bring into, reaction temperature is controlled from 25 DEG C, 50 DEG C, 80 DEG C in course of reaction, 100 DEG C, 120 DEG C, 150 DEG C, 180 DEG C, 200 DEG C to 230 DEG C, after getting each temperature spot reaction 30min, reaction end gas is passed through nickel reburner after carbon molecular sieve chromatographic column is separated, is carried out the formaldehyde in the tail gas of on-line determination outflow, CO and CO by fid detector ₂content, record detects corresponding different temperatures 25 DEG C, 50 DEG C, 80 DEG C, 120 DEG C respectively, formaldehyde conversion corresponding under 150 DEG C of conditions and CO ₂selective, gained the results are shown in following table:

The catalyst A that formaldehyde through catalytic oxidation is used as can be seen from the above table can by formaldehyde complete oxidation 50 DEG C time, and 120 DEG C time CO ₂selectively reach 99.32%.

application comparative examples 1

Be 200 – 250 object cobaltosic oxide powders for contrast with the granularity of embodiment 1 step (1) gained;

Being that to be fixed to internal diameter in miniature quartz pipe fixed bed reactors after 200 – 250 object cobaltosic oxide powders mix with isopyknic quartz sand be the interlude of the reaction tube of 6mm by the granularity of 0.5g embodiment 1 gained, is the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde bubbler (heating water bath 36 DEG C) to bring into.Reaction temperature is controlled from 25 DEG C in course of reaction, 50 DEG C, 80 DEG C, 100 DEG C, 120 DEG C, 150 DEG C, 180 DEG C, 200 DEG C to 230 DEG C, after getting each temperature spot reaction 30min, reaction end gas is passed through nickel reburner after carbon molecular sieve chromatographic column is separated, is carried out the formaldehyde in the tail gas of on-line determination outflow, CO and CO by fid detector ₂content, record detects corresponding different temperatures 25 DEG C, 50 DEG C, 80 DEG C, 120 DEG C respectively, formaldehyde conversion corresponding under 150 DEG C of conditions and CO ₂selective, gained the results are shown in following table:

as can be seen from the above table, contrast granularity is that 200 – 250 object cobaltosic oxide powders could by formaldehyde complete oxidation 150 DEG C time, and 150 DEG C time CO ₂selectively be only 60.00%.

embodiment 2

The catalyst that formaldehyde through catalytic oxidation is used, be core, shell structure, described core is Co ₃o ₄, shell is CeO ₂, the ratio of nucleocapsid presses the molar percentage calculating of Co, Ce metallic atom, specific as follows:

Co 95.55%

Ce 4.45%。

First the preparation method of the catalyst that above-mentioned a kind of formaldehyde through catalytic oxidation is used, namely adopt co-precipitation method to prepare Co ₃o ₄catalyst granules, then at Co ₃o ₄the area load CeO of catalyst granules ₂shell, its preparation process specifically comprises the steps:

(1), granularity is 200 – 250 object cobaltosic oxide powders, and detailed process is with embodiment 1;

(2), 1.439g six nitric hydrate cerium salt is dissolved in 50mL water obtains the cerous nitrate aqueous solution IV that concentration is 0.066mol/L, adding granularity prepared by 5g step (1) is wherein 200 – 250 object powder cobaltosic oxides, and constantly stir formation suspension, under 60 DEG C of conditions, then use the Na of 0.5mol/L ₂cO ₃aqueous solution V regulates suspension pH value to be 7.0, suction filtration after ageing 2h, and the filter cake of gained spends deionized water 6 times, and finally successively at 120 DEG C of dry 12h, roasting 4h at 350 DEG C, obtains the catalyst B that formaldehyde through catalytic oxidation is used;

Above-mentioned concentration used is the cerous nitrate aqueous solution IV of 0.066mol/L and the amount of 200-250 object cobaltosic oxide powder, and by mole% calculating, namely Co:Ce is 95.55%:4.45%.

application Example 2

By catalyst B compressing tablet used for the formaldehyde through catalytic oxidation of above-described embodiment 2 gained and to be crushed to 40-60 order for subsequent use.

Being fixed to internal diameter in miniature quartz pipe fixed bed reactors after mixing with isopyknic quartz sand with the catalyst B (40-60 order) that the formaldehyde through catalytic oxidation of 0.5g embodiment 2 gained is used is the interlude of the reaction tube of 6mm, is the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde bubbler (heating water bath 36 DEG C) to bring into.Reaction temperature is controlled from 25 DEG C in course of reaction, 50 DEG C, 80 DEG C, 100 DEG C, 120 DEG C, 150 DEG C, 180 DEG C, 200 DEG C to 230 DEG C, get after each temperature spot reacts 30 min, reaction end gas is passed through nickel reburner after carbon molecular sieve chromatographic column is separated, is carried out the formaldehyde in the tail gas of on-line determination outflow, CO and CO by fid detector ₂content, record detects corresponding different temperatures 25 DEG C, 50 DEG C, 80 DEG C, 120 DEG C respectively, formaldehyde conversion corresponding under 150 DEG C of conditions and CO ₂selective, gained the results are shown in following table:

The catalyst B that formaldehyde through catalytic oxidation is used as can be seen from the above table can by formaldehyde complete oxidation 80 DEG C time, and 180 DEG C time CO ₂selectively reach 100.00%.

embodiment 3

The catalyst that formaldehyde through catalytic oxidation is used, be core, shell structure, described core is Co ₃o ₄, shell is CeO ₂, the ratio of nucleocapsid presses the molar percentage calculating of Co, Ce metallic atom, specific as follows:

Co 96.98%

Ce 3.02%。

First the preparation method of the catalyst that above-mentioned a kind of formaldehyde through catalytic oxidation is used, namely adopt co-precipitation method to prepare Co ₃o ₄catalyst granules, then at Co ₃o ₄the area load CeO of catalyst granules ₂shell, its preparation process specifically comprises the steps:

(1), granularity is 200 – 250 object cobaltosic oxide powders, and detailed process is with embodiment 1;

(2), 0.962g six nitric hydrate cerium salt is dissolved in 50mL water obtains the cerous nitrate aqueous solution IV that concentration is 0.044mol/L, adding granularity prepared by 5g step (1) is wherein 200 – 250 object powder cobaltosic oxides, and constantly stir formation suspension, under 60 DEG C of conditions, then use the Na of 0.5mol/L ₂cO ₃aqueous solution V regulates suspension pH value to be 7.0, suction filtration after ageing 2h, and the filter cake of gained spends deionized water 6 times, and finally successively at 120 DEG C of dry 12h, roasting 4h at 350 DEG C, obtains the catalyst C that formaldehyde through catalytic oxidation is used;

Above-mentioned concentration used is the cerous nitrate aqueous solution IV of 0.044mol/L and the amount of 200-250 object cobaltosic oxide powder, and by mole% calculating, namely Co:Ce is 96.98%:3.02%.

application Example 3

By catalyst C compressing tablet used for the formaldehyde through catalytic oxidation of above-described embodiment 3 gained and to be crushed to 40-60 order for subsequent use.

With the catalyst C(40-60 order that the formaldehyde through catalytic oxidation of 0.5g embodiment 3 gained is used) mix with isopyknic quartz sand after to be fixed to internal diameter in miniature quartz pipe fixed bed reactors be the interlude of the reaction tube of 6mm, be the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde bubbler (heating water bath 36 DEG C) to bring into, reaction temperature is controlled from 25 DEG C, 50 DEG C, 80 DEG C in course of reaction, 100 DEG C, 120 DEG C, 150 DEG C, 180 DEG C, 200 DEG C to 230 DEG C, after getting each temperature spot reaction 30min, reaction end gas is passed through nickel reburner after carbon molecular sieve chromatographic column is separated, is carried out the formaldehyde in the tail gas of on-line determination outflow, CO and CO by fid detector ₂content, record detects corresponding different temperatures 25 DEG C, 50 DEG C, 80 DEG C, 120 DEG C respectively, formaldehyde conversion corresponding under 150 DEG C of conditions and CO ₂selective, gained the results are shown in following table:

The catalyst C that formaldehyde through catalytic oxidation is used as can be seen from the above table can by formaldehyde complete oxidation 25 DEG C time, and 120 DEG C time CO ₂selectively reach 100.00%.

Contrasted by the result of Application Example 1-3 and application comparative examples 1 gained, can find out, a kind of formaldehyde through catalytic oxidation of the present invention catalyst used is in catalysis oxidation of formaldehyde process, the catalyst C that particularly formaldehyde through catalytic oxidation is used just can make the conversion ratio of formaldehyde reach 100% at 25 DEG C, and pure Co ₃o ₄catalyst is in formaldehyde through catalytic oxidation process, and the formaldehyde conversion reaction temperature reached needed for 100% oxidation wants more than 150 DEG C.

application Example 4

By catalyst C compressing tablet used for the formaldehyde through catalytic oxidation of above-described embodiment 3 gained and to be crushed to 40-60 order for subsequent use.

With the catalyst C(40-60 order that the formaldehyde through catalytic oxidation of 0.5g embodiment 3 gained is used) mix with isopyknic quartz sand after to be fixed to internal diameter in miniature quartz pipe fixed bed reactors be the interlude of the reaction tube of 6mm, be the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde bubbler (heating water bath 36 DEG C) to bring into.Control reaction temperature 120 DEG C in course of reaction, by reaction end gas after carbon molecular sieve chromatographic column is separated by nickel reburner, by fid detector carry out the on-line determination reaction time be respectively 4h, 24h, 48h, 60h time the tail gas that flows out in formaldehyde, CO and CO ₂content, thus formaldehyde conversion and CO when calculating reacting time is respectively 4h, 24h, 48h, 60h ₂selective, gained the results are shown in following table:

The catalyst C stability that formaldehyde through catalytic oxidation is used is as can be seen from the above table fine, and formaldehyde conversion reaches 100% Absorbable organic halogens 48h, now CO ₂selectively also be stabilized in 100%; And when the reaction time reaches 60h, the conversion ratio of formaldehyde just starts to drop to 99.20%, CO ₂selectively be down to 99.82%, namely formaldehyde conversion only reduces by 0.8%, CO ₂selectively only reduce by 0.18%, show thus, the good stability of catalyst tool that a kind of formaldehyde through catalytic oxidation of the present invention is used and CO ₂selective.

application comparative examples 2

Be 200 – 250 object cobaltosic oxide powders for contrast with the granularity of step (1) gained in embodiment 3, be 200 – 250 object cobaltosic oxide powders for contrast with 0.5g with the granularity of step (1) gained in embodiment 3, being fixed to internal diameter in miniature quartz pipe fixed bed reactors after mixing with isopyknic quartz sand is the interlude of the reaction tube of 6mm, is the N of 30mL/min at flow velocity ₂under atmosphere after 200 DEG C of pretreatment 30min, then drop to room temperature, then switching overall flow rate is that the reaction gas of 50mL/min carries out catalytic reaction, and in described reaction gas, be 600ppm containing formaldehyde gas, surplus is air, and formaldehyde gas is by Balance Air N ₂flow through paraformaldehyde bubbler (heating water bath 36 DEG C) to bring into.Control reaction temperature 120 DEG C in course of reaction, by reaction end gas after carbon molecular sieve chromatographic column is separated by nickel reburner, by fid detector carry out the on-line determination reaction time be respectively 4h, 24h, 48h, 60h time the tail gas that flows out in formaldehyde, CO and CO ₂content, thus formaldehyde conversion and CO when calculating reacting time is respectively 4h, 24h, 48h, 60h ₂selective, gained the results are shown in following table:

Pure Co as can be seen from the above table ₃o ₄catalyst stability is poor, and formaldehyde conversion is up to 84% and stablizes 4h, now CO ₂selective is 78.52%; Then along with the increase in reaction time, the conversion ratio of formaldehyde starts to drop to 71%, and CO ₂selectively be increased to 82.44%; After 15h, formaldehyde conversion is down to 43%, CO ₂selectively be stabilized in 82%; During 20h, the whole inactivation of catalyst, formaldehyde conversion is reduced to 0, CO ₂selectively also drop to 0.

In sum, a kind of formaldehyde through catalytic oxidation of the present invention catalyst used just can make the conversion ratio of formaldehyde reach 100% room temperature 25 DEG C, the good stability of this catalyst tool and CO simultaneously ₂selective.

Above said content be only the present invention conceive under basic explanation, and according to any equivalent transformation that technical scheme of the present invention is done, all should protection scope of the present invention be belonged to.

Claims (5)

1. the catalyst that formaldehyde through catalytic oxidation is used, it is characterized in that described formaldehyde through catalytic oxidation catalyst used is core, shell structure, described core is Co ₃o ₄, shell is CeO ₂, the ratio of nucleocapsid presses the molar percentage calculating of Co, Ce metallic atom, specific as follows:

Co 95.55–97.60%

Ce 2.40–4.45%。

2. the catalyst that a kind of formaldehyde through catalytic oxidation as claimed in claim 1 is used, is characterized in that the ratio of nucleocapsid calculates by the molar percentage of Co, Ce metallic atom, specific as follows:

Co 97.60%

Ce 2.40%。

3. the catalyst that a kind of formaldehyde through catalytic oxidation as claimed in claim 1 is used, is characterized in that the ratio of nucleocapsid calculates by the molar percentage of Co, Ce metallic atom, specific as follows:

Co 95.55%

Ce 4.45%。

4. the catalyst that a kind of formaldehyde through catalytic oxidation as claimed in claim 1 is used, is characterized in that the ratio of nucleocapsid calculates by the molar percentage of Co, Ce metallic atom, specific as follows:

Co 96.98%

Ce 3.02%。

5. first the preparation method of the catalyst that a kind of formaldehyde through catalytic oxidation as claimed in claim 1 is used, namely adopt co-precipitation method to prepare Co ₃o ₄catalyst granules, then at Co ₃o ₄the area load CeO of catalyst granules ₂shell, its preparation process specifically comprises the steps:

(1), by the Co (NO of 1mol/L ₃) ₂the Na of solution I and 0.5mol/L ₂cO ₃solution II by volume ratio is that 1:3.5 mixes, and the often amount of dripping that controls is that the mixed liquor of gained is dropwise added drop-wise to the Na that 0.5mol/L is housed by 0.05 – 0.07mL ₂cO ₃in the beaker of solution III, controlling speed of agitator in dropping process is 200 – 300r/min, temperature 60 C, pH value is controlled to drip within the scope of 9.4-9.8 to terminate by pH meter on-line monitoring, wait to drip and terminate, suction filtration after ageing 1h, after the filter cake distilled water of gained washs 6 times, then dries 12h by filter cake through 120 DEG C, then in 300 DEG C of roasting 4h, obtain powder cobaltosic oxide, then sieve, obtaining granularity is 200 – 250 object cobaltosic oxide powders;

The Na of the above-mentioned 0.5mol/L be equipped with in beaker ₂cO ₃the amount of solution III according to the stirring-head of mechanical agitator near but not encounter at the bottom of beaker and the Na of 0.5mol/L can be touched ₂cO ₃solution III is as the criterion;

(2), in concentration be that to add the granularity prepared by step (1) in the cerous nitrate aqueous solution IV of 0.035-0.066mol/L be 200 – 250 object powder cobaltosic oxides, and constantly stir and form suspension, then under 60 DEG C of conditions with the Na of 0.5mol/L ₂cO ₃aqueous solution V regulates suspension pH value to be 7.0, suction filtration after ageing 2h, and the filter cake of gained spends deionized water 6 times, and finally successively at 120 DEG C of dry 12h, roasting 4h at 350 DEG C, obtains the catalyst that formaldehyde through catalytic oxidation is used;

The cerous nitrate aqueous solution IV of above-mentioned 0.035-0.066mol/L used and the amount of 200-250 object cobaltosic oxide powder, by mole% calculating, namely Co:Ce is 95.55 – 97.60%:2.40 – 4.45%.