CN105727942B - A kind of palladium/carbon nano-tube catalyst and its preparation method and application - Google Patents
A kind of palladium/carbon nano-tube catalyst and its preparation method and application Download PDFInfo
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Abstract
The catalyst and its preparation method and application that the present invention relates to a kind of for synthesizing methanol by hydrogenating carbon dioxide, more particularly to a kind of palladium/carbon nano-tube catalyst and its preparation and application, catalyst is using carbon nanotube as carrier, Pd nano particle is deposited on inside carbon nanotube pipe, it is denoted as x%Pd/CNTs-in, or Pd nano particle is deposited on outside carbon nanotube pipe, it is denoted as x%Pd/CNTs-out, x indicates the load capacity of palladium in catalyst, the load capacity of palladium is 1~10wt% in catalyst, catalyst of the present invention is applied in the reaction of synthesizing methanol by hydrogenating carbon dioxide, under the same terms, palladium/carbon nano-tube catalyst is applied to hydrogenation of carbon dioxide to generate the space-time yield of methanol to be conventional alumina, silica, the 1.8-26 of activated carbon supported palladium catalyst .4 again.
Description
Technical field
The invention belongs to catalyst fields, and in particular to a kind of palladium/carbon nano-tube catalyst and preparation method thereof and two
Application in carbonoxide synthesizing methanol by hydrogenating.
Background technique
Carbon dioxide (CO2) a large amount of discharge bring global climate changes, caused the highest attention of international community.
Global carbon dioxide discharge amount in 2013 is 36,000,000,000 tons, wherein Chinese discharge amount has just reached 10,000,000,000 tons, CO2Emission reduction it is necessary
Implement as early as possible, is even more that Time and tide wait for no man in China；On the other hand, fossil resource is increasingly depleted, and energy crisis also constantly warns
The mankind.The most fundamental solution for solving above-mentioned environmental problem and energy problem is exactly to imitate naturally, construct artificial photosynthesis, is utilized
CO2With hydrate fuel and chemicals.But just current scientific and technological level, uses CO2It is also faced with hydrate fuel and chemicals
It is greatly difficult, if generating hydrogen using the electric energy electrolysis water that solar energy photocatalytic water and other renewable energy generate,
Utilize CO2Hydrogen addition technology synthetic fuel and chemicals are then solution one of an environmental problem and the effective way of energy problem
[Nature Chemistry.6(2014)320]。
Methanol is one of most important raw material of industry, itself is also good fuel, utilizes CO2Synthesizing methanol by hydrogenating is real
The existing above-mentioned most effective strategy of route.For CO2The catalyst research of synthesizing methanol by hydrogenating it is most be Cu/ZnO catalyst, grind
Studying carefully most of is that CuO/ZnO is supported on Al2O3、ZrO2、SiO2、TiO2On equal carriers, and add into catalyst Na, K, Ce,
The metals such as Cs, Ca, Zr, La, Mn, Ti, Th, Mg, Ba are modified [Handbook of Heterogeneous as auxiliary agent
Catalysis.Wiley,2008,2920].And some researches show that Supported Pd-Catalysts to have than Cu/ZnO catalyst more in recent years
High low temperature active [Journal of Catalysis.197 (2001) 267], shows excellent CO2It is catalyzed potentiality, section
It grinds worker and some researchs, Collins etc. [Catalysis Letters.103 (2005) 83] research also has been done to Pd catalyst
It was found that Ga2O3Addition can be obviously improved CO on Pd catalyst2Add the reactivity of hydrogen.[the Catalysis such as Iwasa
Letters.96 (2004) 75] by Pd (NO3)2Aqueous solution be supported on a series of oxide carriers, such as ZnO, Ga2O3、
In2O3、SiO2、MgO、CeO2、ZrO2On, the study found that the catalytic activity highest of Pd/ZnO, XRD characterization finds the formation of methanol
With PdZn alloy phase there are closely related.Koizumi etc. [Catalysis Today.194 (2012) 16] with MCM-41 and
This kind of mesoporous silicon material of SBA-15 loads Pd, achieves and compares SiO2The better catalytic activity of Pt-supported catalyst.Nevertheless, Pd
CO on catalyst2There is still a need for greatly improve for the activity of preparing methanol by hydrogenation.Another research field, multi-walled carbon nanotube (are abbreviated as
CNTs) due to its graphited tube wall, nanoscale lumen, to H2Good adsorption desorption performance and the enrichment to substrate
It arouses widespread concern, this nanoscale tubulose carbon material is compared to conventional catalyst carrier such as Al2O3、SiO2, it is living
Property charcoal etc. has more superior performance [Current topics in catalysis.4 (2005) 1], recent studies suggest that, it urges
Agent is located in CNTs pipe and pipe is outer, and catalytic performance has apparent difference, is assembled in the catalyst in CNTs pipe some
There is more superior catalytic performance [Nature materials.6 (2007) 507] in reaction, this superiority is embodied in incessantly
Activity is even more improved largely to target product selectivity.Research work (the application number of our early periods
200910236390.1, Angew.Chem.Int.Ed.50 (2011) 4913) show to be supported on urging for nano platinum particle in lumen
Agent has higher activity and selectivity in the asymmetric hydrogenation of keto ester, is that the outer platinum/carbon nanotube catalyst of pipe is living
Seven times of property are traditional platinum/active carbon and active ten times of platinum/aluminium oxide catalyst or so.But Bao et al. is it has also been found that support
It supports with intraluminal ruthenium nano particle catalyst in the ruthenium nano particle catalyst ratio outside carbon nanotubes lumen in ammonia synthesis table
Reveal better reactivity [Chem, Eur.J., 16 (2010) 5379].Thus combine Pd catalyst to CO2Preparing methanol by hydrogenation
Special performance as carrier of low temperature advantage and CNTs, this research system develops a kind of preparation method, selective by palladium
Nanoparticle is supported in carbon nanotubes lumen or outside lumen, and then is applied to CO2Synthesizing methanol by hydrogenating reaction, realizes such
CO on catalyst2To the Efficient Conversion of methanol.
Summary of the invention
The present invention provides a kind of palladium/carbon nano-tube catalysts suitable for synthesizing methanol by hydrogenating carbon dioxide.
The present invention provides the preparation method and applications of above-mentioned palladium/carbon nano-tube catalyst.
Palladium/carbon nano-tube catalyst provided by the invention, Pd nano particle are optionally deposited on carbon nanotube pipe
Intracavitary portion, or it is carried on carbon nanotubes lumen outer surface.Carbon nanotube used in it is that multi-walled carbon nanotube (is abbreviated as
CNTs), outer diameter is 8~60nm, preferably 10~50nm, and palladium is calculated as 1~10% with Metal Palladium quality, is deposited on carbon nanotube pipe
Intracavitary portion's Pd nano particle is carried on the Pd nano particle outside carbon nanotubes lumen having a size of 2~5nm having a size of 1~3nm.
It is provided by the invention to prepare above-mentioned Pd nano particle and support palladium/carbon nanometer pipe catalytic inside carbon nanotubes lumen
Agent x%Pd/CNTs (in) is prepared by the following method:
A) carbon nanotube is placed in the nitric acid solution of 34~68wt%, at 130~155 DEG C flow back 8~16h, go from
Sub- water washing filters, 60~80 DEG C of dry 24~36h obtain the carbon nanotube of functionalization to neutrality；
B) the resulting carbon nanotube 1g of step a is taken to be dipped in the palladium salt solution of certain solvent of 10~30mL metering, with 28
2~6h of ultrasonication of~100kHz, 100W；
C) mixture of the resulting carbon nanotube of step b and palladium salt is stirred at 20~30 DEG C, until solvent volatilization is completely,
Mixture becomes solid；
D) by the resulting mixture of step c dry 12 at 60~80 DEG C~for 24 hours.It is gone back at 200~300 DEG C with High Purity Hydrogen
2~4h of original, obtains x%Pd/CNTs-in catalyst.
It is provided by the invention to prepare above-mentioned Pd nano particle and support palladium/carbon nanometer pipe catalytic outside carbon nanotubes lumen
Agent x%Pd/CNTs-out is prepared by the following method:
A) carbon nanotube is placed in the nitric acid solution of 34~68wt%, at 130~155 DEG C flow back 8~16h, go from
Sub- water washing filters, 60~80 DEG C of dry 24~36h obtain the carbon nanotube of functionalization to neutrality；
B) the resulting carbon nanotube 1g of step a is taken to be dipped in 5~25mL dimethylbenzene, with 28~100kHz, the ultrasound of 100W
Wave handles 2~6h；
C) ammonium carbonate/ammonia spirit of 0.5~1mol/L is prepared, the palladium salt of metering is dissolved in 20~40mL solution, adds
Enter in the resulting carbon nanotube of step b and xylene mixture, stirs evenly；
D) the resulting mixture of step c is stirred to dry 24~36h at 80~100 DEG C, it is then dry in 140~450 DEG C
Dry 12~for 24 hours.Then High Purity Hydrogen reductase 12~4h at 200~300 DEG C is used, x%Pd/CNTs (out) catalyst is obtained.
The load capacity of Pd is 1~10wt% in above-mentioned x%Pd/CNTs catalyst loading, and highest loading is 10wt%,
General loading is 3~5wt%
Above-mentioned carbon nanotube is multi-walled carbon nanotube, and outer diameter is 8~60nm, and 3~50nm of internal diameter, length is 10~30 μm,
Phosphorus content > 95%, preferably outer diameter are 10~60nm, and interior 5~30nm of caliber, length is 10~30 μm, phosphorus content > 95%, especially
It is that outer diameter is 10~20nm, and interior 5~10nm of caliber, length is 0.5~30 μm of phosphorus content > 99%.
In above-mentioned preparation method, carbon nanotube is handled through nitric acid reflux oxidation, and concentration of nitric acid is 34~68wt%, preferably
50~68wt%；Return time is 6~18h, preferably 10~14h；Reflux temperature be 110~160 DEG C, preferably 130~150
℃。
In above-mentioned preparation method, palladium salt used includes palladium chloride, palladium acetate, palladium nitrate etc., preferably palladium chloride；Dissolution
Solvent used in palladium salt is the mixed solvent of acetone, ethyl alcohol, water and acetone or alcohol and water, preferably acetone；Measure palladium salt
Concentration be 0.02~0.2mol/L, preferably 0.1~0.15mol/L.
In above-mentioned preparation method, ultrasonic power 100W, supersonic frequency is 28~100kHz, preferably 45kHz；When ultrasonic
Between be 1~6h, preferably 3h.
The activity rating that catalyst reacts synthesizing methanol by hydrogenating carbon dioxide is in pressurization static bed continuous flow reactor-
It is carried out in GC combined system.Reaction is in 2.0~5.0MPa, and 200~260 DEG C, material synthesis gas group becomes V (H2)/V(CO2)/V
(Ar)=72/24/4, air speed be GHSV=1000~5000mL/ (h g) reaction condition under carry out.Before reaction, forerunner is aoxidized
State catalyst is in normal pressure, pure H2By certain heating reduction program (at room temperature with 1 DEG C/min liter in air-flow (flow velocity 30mL/min)
To 250 DEG C, constant temperature 6h) carry out prereduction in situ, last 12h, after be adjusted to reaction required temperature, switching imports material synthesis gas.
The reaction end gas being discharged from reactor outlet is unloaded immediately to normal pressure, warm pipeline (temperature is maintained at 130 DEG C) direct sending gas phase color
Spectrometer ten-way valve is sampled, by the thermal conductivity detector (TCD) (TCD) and hydrogen flame detector of AgilentGC-6890 type gas chromatograph
(FID) combine and make on-line analysis.The former chromatographic column filler is TDX-01 carbon molecular sieve (Dalian Chemistry and Physics Institute chiral center product), column
Long 3m, uses H2Make carrier gas, work at 100 DEG C, is used for separation detection CO, Ar (as internal standard) and CO2；The latter's chromatographic column is
PEG-20M capillary column (Dalian Chemistry and Physics Institute chiral center product), specification are 30m × 0.32mm × 0.5 μm, use N2Make carrier gas,
Operating temperature is maintained at 100 DEG C, is used for separation detection lower carbon number hydrocarbons, low-carbon alcohol ether and other oxygen-bearing organic matters.CO2Conversion ratio and life
At the C- based selective of CO by N2Internal standard method measuring and calculating, the C- based selective and space-time yield of the carbonaceous products such as alcohol, ether, hydrocarbon are by C base
Normalization method calculates.
The preparation method of palladium/carbon nano-tube catalyst provided by the invention and the catalyst are in hydrogenation of carbon dioxide synthesis first
Advantage in alcohol reaction is:
1, the method for preparing catalyst is simple to operate, can control the size and distributing position of Pd nano particle,
The size of Pd nano particle can be controlled well in 1~5nm and be evenly distributed in carbon nanotubes lumen or managed
Outside chamber.
2, Pd nano particle is deposited on the Pd/CNTs-in catalyst in carbon nanotube pipe compared to conventional alumina, titanium dioxide
The Pd/CNTs-out catalyst that silicon, activated carbon supported palladium catalyst and nanoparticle are deposited on outside carbon nanotube pipe is shown
Higher methanol selectivity and reactivity.
Detailed description of the invention
Fig. 1 is the transmission electron microscope photo of catalyst；
Wherein, scheme (A) and scheme the transmission electron microscope photo that (B) is 5%Pd/CNTs-in catalyst prepared by embodiment 3, from
As can be seen that carbon nanotube outer diameter is 10~20nm in figure, internal diameter is 5~10nm, and Pd nano particle is uniformly dispersed, having a size of 1
~3nm, 80% Pd nano particle are located inside carbon nanotubes lumen；
Scheme (C) and scheme the transmission electron microscope photo that (D) is 5%Pd/CNTs-out catalyst prepared by embodiment 4, from figure
As can be seen that carbon nanotube outer diameter is 10~20nm, internal diameter is 5~10nm, and Pd nano particle is uniformly dispersed, having a size of 2~
5nm, 90% Pd nano particle are located at outside carbon nanotubes lumen.
Specific embodiment
Below by embodiment, the invention will be further described.
Embodiment 1
Weigh carbon nanotube (Chengdu Organical Chemical Co., Ltd., Chinese Academy of Sciences's product, 5~10nm of internal diameter, outer diameter 10~
20nm, 10~30 μm of length, phosphorus content > 95%) 12g is placed in the round-bottomed flask of 1L, is added 600mL concentrated nitric acid (68wt%),
It is stirred at reflux at 140 DEG C 12 hours in oil bath, being washed with deionized after cooling to upper liquid pH value is neutrality, and sand core funnel is taken out
Filter, is put into 80 DEG C of baking ovens constant temperature 24 hours, the carbon nanotube for the functionalization being open.87.6mg palladium chloride is weighed to be placed in
In 50mL flask, the concentrated hydrochloric acid hydrotropy that 0.5mL mass fraction is 37% is added, adding 25mL acetone keeps palladium chloride sufficiently molten
Solution.It takes the carbon nanotube 1g of above-mentioned functionalization to be added in the palladium chloride solution, gained mixed liquor is placed in ultrasonator super
Sonication 3h sets power 100W, frequency 45kHz.Then it stirs in 30 DEG C of lower open mouths to solvent and all evaporates, mixed liquor Cheng Gu
Body block.Gained block is placed in 60 DEG C of baking ovens dry 12h, obtains the oxidation state forerunner of 5%Pd/CNTs-in catalyst
Body；
Catalyst is to the catalytically active assessment of synthesizing methanol by hydrogenating carbon dioxide in pressurization static bed continuous flow reactor-
It is carried out in GC combined system.Catalyst samples dosage is 0.5g, and before reaction, oxidized catalyst is in normal pressure, pure H2Air-flow, flow velocity
For 30mL/min, in by certain temperature program carry out prereduction in situ, rise to 250 DEG C, constant temperature 6h at room temperature with 1 DEG C/min, altogether
Last 12h, obtain 5%Pd/CNTs-in catalyst, after be adjusted to reaction required temperature, switching import material synthesis gas carry out it is anti-
It answers.Product makees online point by being equipped with the AgilentGC-6890 type gas chromatograph of TCD and FID dual detector, double chromatographic columns
Analysis.In 2.0MPa, 200 DEG C, V (H2)/V(CO2Under)/V (Ar)=72/24/4, GHSV=1000mL/ (h g) reaction condition,
CO on 5%Pd/CNTs-in catalyst2Up to 1.64%, methanol selectivity (adds hydrogen partial, does not include generating conversion ratio for 77.8%
The selectivity of CO), corresponding space-time yield reaches 3.94mg/ (h g), and detailed results are shown in Table 1 sequence 1.
Embodiment 2
Weigh carbon nanotube (middle section's epoch nanometer Co., Ltd product, 5~10nm of internal diameter, 10~20nm of outer diameter, length 10
~30 μm, phosphorus content > 95%) 12g is placed in the round-bottomed flask of 1L, is added 600mL concentrated nitric acid (68wt%), 140 DEG C in oil bath
Under be stirred at reflux 12h, being washed with deionized after cooling to upper liquid pH value is neutrality, and sand core funnel filters, and is put into 80 DEG C of bakings
In case constant temperature for 24 hours, the carbon nanotube for the functionalization being open.The carbon nanotube for weighing the above-mentioned functionalization of 1g is burnt in 50mL round bottom
In bottle, 20mL dimethylbenzene is added, is ultrasonically treated 3h, sets power 100W, frequency 45kHz.Weigh 2g ammonium carbonate, 87.6mg chlorination
Palladium is dissolved in 35mL concentrated ammonia liquor, then ammonia concn 25% is added in the mixed liquor of above-mentioned carbon nanotube and dimethylbenzene, stirs
30min is mixed, for 24 hours in 100 DEG C of dryings, 140 DEG C of dry 12h obtain the oxidation state presoma of 5%Pd/CNTs-out catalyst；
Catalyst is to the catalytically active assessment of synthesizing methanol by hydrogenating carbon dioxide in pressurization static bed continuous flow reactor-
It is carried out in GC combined system.Catalyst samples dosage is 0.5g, and before reaction, oxidized catalyst is in normal pressure, pure H2Air-flow, flow velocity
For 30mL/min, in by certain temperature program carry out prereduction in situ, rise to 250 DEG C, constant temperature 6h at room temperature with 1 DEG C/min, altogether
Last 12h, obtain 5%Pd/CNTs-out catalyst, after be adjusted to reaction required temperature, switching import material synthesis gas carry out it is anti-
It answers.Product makees online point by being equipped with the AgilentGC-6890 type gas chromatograph of TCD and FID dual detector, double chromatographic columns
Analysis.In 2.0MPa, 200 DEG C, V (H2)/V(CO2Under)/V (Ar)=72/24/4, GHSV=1000mL/ (h g) reaction condition,
CO on 5%Pd/CNTs-in catalyst2Up to 1.29%, methanol selectivity 74.4%, corresponding space-time yield reaches conversion ratio
2.98mg/ (h g), detailed results are shown in Table 1 sequence 2.
Embodiment 3
The preparation of 5%Pd/CNTs-in catalyst is with embodiment 1, in 2.0MPa, 220 DEG C, and V (H2)/V(CO2)/V (Ar)=
Under the reaction condition of 72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-in catalyst, CO2Conversion ratio reaches
1.86%, methanol selectivity 65.1%, corresponding space-time yield reaches 3.56mg/ (h g), and detailed results are shown in Table 1 sequence 3.
Embodiment 4
The preparation of 5%Pd/CNTs-out catalyst is with embodiment 2, in 2.0MPa, 220 DEG C, and V (H2)/V(CO2)/V(Ar)
Under the reaction condition of=72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-out catalyst, CO2Conversion ratio reaches
1.41%, methanol selectivity 55.4%, corresponding space-time yield reaches 2.41mg/ (h g), and detailed results are shown in Table 1 sequence 4.
Embodiment 5
The preparation of 5%Pd/CNTs-in catalyst is with embodiment 1, in 2.0MPa, 240 DEG C, and V (H2)/V(CO2)/V (Ar)=
Under the reaction condition of 72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-in catalyst, CO2Conversion ratio reaches
2.41%, methanol selectivity 53.8%, corresponding space-time yield reaches 3.69mg/ (h g), and detailed results are shown in Table 1 sequence 5.
Embodiment 6
The preparation of 5%Pd/CNTs-out catalyst is with embodiment 2, in 2.0MPa, 240 DEG C, and V (H2)/V(CO2)/V(Ar)
Under the reaction condition of=72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-out catalyst, CO2Conversion ratio reaches
2.33%, methanol selectivity 16.7%, corresponding space-time yield reaches 1.18mg/ (h g), and detailed results are shown in Table 1 sequence 6.
Embodiment 7
The preparation of 5%Pd/CNTs-in catalyst is with embodiment 1, in 2.0MPa, 250 DEG C, and V (H2)/V(CO2)/V (Ar)=
Under the reaction condition of 72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-in catalyst, CO2Conversion ratio reaches
2.96%, methanol selectivity 48.1%, corresponding space-time yield reaches 3.96mg/ (h g), and detailed results are shown in Table 1 sequence 7.
Embodiment 8
The preparation of 5%Pd/CNTs-out catalyst is with embodiment 2, in 2.0MPa, 250 DEG C, and V (H2)/V(CO2)/V(Ar)
Under the reaction condition of=72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-out catalyst, CO2Conversion ratio reaches
2.52%, methanol selectivity 13.2%, corresponding space-time yield reaches 0.98mg/ (h g), and detailed results are shown in Table 1 sequence 8.
Embodiment 9
The preparation of 5%Pd/CNTs-in catalyst is with embodiment 1, in 2.0MPa, 260 DEG C, and V (H2)/V(CO2)/V (Ar)=
Under the reaction condition of 72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-in catalyst, CO2Conversion ratio reaches
3.16%, methanol selectivity 39.8%, corresponding space-time yield reaches 3.47mg/ (h g), and detailed results are shown in Table 1 sequence 9.
Embodiment 10
The preparation of 5%Pd/CNTs-out catalyst is with embodiment 2, in 2.0MPa, 260 DEG C, and V (H2)/V(CO2)/V(Ar)
Under the reaction condition of=72/24/4, GHSV=1000mL/ (h g), on 5%Pd/CNTs-out catalyst, CO2Conversion ratio reaches
2.61%, methanol selectivity 11.3%, corresponding space-time yield reaches 0.83mg/ (h g), and detailed results are shown in Table 1 sequence 10.
Embodiment 11-13 is as a comparison case
Embodiment 11
It weighs 87.6mg palladium chloride to be placed in 50mL flask, the concentrated hydrochloric acid hydrotropy that 0.5mL mass fraction is 37% is added, then
25mL deionized water, which is added, dissolves palladium chloride sufficiently, and 1g silica (SiO is added2, Alfa Aesar product, SA=269m2/
G), gained mixed liquor is placed in ultrasonator ultrasonic treatment 3h, sets power 100W, frequency 45kHz.It stands overnight, so
It is placed in 60 DEG C of baking ovens dry 12h, obtains 5%Pd/SiO2The oxidation state presoma of catalyst；
Catalyst is to the catalytically active assessment of synthesizing methanol by hydrogenating carbon dioxide in pressurization static bed continuous flow reactor-
It is carried out in GC combined system.Catalyst samples dosage is 0.5g, and before reaction, oxidized catalyst is in normal pressure, pure H2Air-flow (flow velocity
To carry out prereduction in situ by certain temperature program (rising to 250 DEG C at room temperature with 1 DEG C/min, constant temperature 6h) in 30mL/min), altogether
12h is lasted, 5%Pd/SiO is obtained2Catalyst.After be adjusted to reaction required temperature, switching import material synthesis gas reacted.It produces
Object makees on-line analysis by being equipped with the AgilentGC-6890 type gas chromatograph of TCD and FID dual detector, double chromatographic columns.?
2.0MPa, 250 DEG C, V (H2)/V(CO2Under)/V (Ar)=72/24/4, GHSV=1000mL/ (h g) reaction condition, 5%Pd/
SiO2CO on catalyst2Up to 2.36%, methanol selectivity (adds hydrogen partial, does not include the selection for generating CO conversion ratio for 31.6%
Property), corresponding space-time yield reaches 2.15mg/ (h g), and detailed results are shown in Table 1 sequence 11.
Embodiment 12
The preparation of catalyst has only changed catalyst carrier into aluminium oxide (Al with embodiment 112O3, traditional Chinese medicines reagent is limited
Products, SA=263m2/g).In 2.0MPa, 250 DEG C, V (H2)/V(CO2)/V (Ar)=72/24/4, GHSV=1000mL/
Under the reaction condition of (h g), 5%Pd/Al2O3CO on catalyst2For conversion ratio up to 2.95%, methanol selectivity (adds hydrogen portion for 2%
Point, do not include the selectivity for generating CO), corresponding space-time yield reaches 0.15mg/ (h g), and detailed results are shown in Table 1 sequence 12.
Embodiment 13
The preparation of catalyst has only changed catalyst carrier into active carbon (AC, the limited public affairs of traditional Chinese medicines reagent with embodiment 11
Take charge of product, SA=663m2/g).In 2.0MPa, 250 DEG C, V (H2)/V(CO2)/V (Ar)=72/24/4, GHSV=1000mL/ (h
G) under reaction condition, CO on 5%Pd/AC catalyst2Conversion ratio up to 1.85%, methanol selectivity be 5.4% (add hydrogen partial,
Do not include the selectivity for generating CO), corresponding space-time yield reaches 0.29mg/ (h g), and detailed results are shown in Table 1 sequence 13.
1 catalyst activity evaluation result of table
Evaluation condition 2.0MPa, GHSV=1000h-1；Add hydrogen partial dimethyl ether selectivity unlisted.
Claims (14)
1. a kind of application of palladium/carbon nano-tube catalyst in synthesizing methanol by hydrogenating carbon dioxide reaction, it is characterised in that:
The catalyst be selectively mainly deposited on using carbon nanotube as carrier, by Pd nano particle inside carbon nanotubes lumen or
It is mainly deposited on outside carbon nanotubes lumen, outside refers to the outer surface of tube wall of carbon nanotube；
It is mainly deposited on and refers to that the quality being deposited on inside carbon nanotubes lumen is greater than inside carbon nanotubes lumen and be deposited on carbon and receive
Quality outside mitron lumen, is denoted as x%Pd/CNTs-in, and internal palladium particle diameter is 1~3nm；
It is mainly deposited on and refers to that the quality being deposited on outside carbon nanotubes lumen is greater than outside carbon nanotubes lumen and be deposited on carbon and receive
Quality inside mitron lumen, is denoted as x%Pd/CNTs-out, and external palladium particle diameter is 2~5nm；
Wherein CNTs is multi-walled carbon nanotube, and x indicates the load capacity of palladium in catalyst, in catalyst the load capacity of palladium be 1~
10wt%.
2. application as described in claim 1, it is characterised in that: carbon nanotube is multi-walled carbon nanotube, and outer diameter is 8~60nm,
Internal diameter is 3~50nm, and length of carbon nanotube is 0.5~50 μm, phosphorus content > 95%.
3. application as claimed in claim 2, it is characterised in that: the phosphorus content is > 99%.
4. application as claimed in claim 2, it is characterised in that: carbon nanotube outer diameter is 10~50nm, and internal diameter is 5~30nm,
Length of carbon nanotube is 5~40 μm.
5. application as claimed in claim 2, it is characterised in that: carbon nanotube outer diameter is 10~20nm, and internal diameter is 5~10nm,
Length of carbon nanotube is 10~30 μm.
6. application as claimed in claim 1 or 2, it is characterised in that:
It is mainly deposited on and refers to that the Pd nano particle being deposited on inside carbon nanotubes lumen accounts for inside carbon nanotubes lumen and be deposited on
The 60%-80% of total amount in carbon nanotube；
It is mainly deposited on and refers to that the Pd nano particle being deposited on outside carbon nanotubes lumen accounts for outside carbon nanotubes lumen and be deposited on
The 60%-90% of total amount in carbon nanotube.
7. application as described in claim 1, it is characterised in that: the x%Pd/CNTs-in catalyst the preparation method is as follows:
A) carbon nanotube is placed in nitric acid solution, is stirred at reflux at 110~160 DEG C, be washed with deionized after cooling to
Upper liquid is neutrality, is filtered, dry, the carbon nanotube for the functionalization being open；
B) it takes the resulting carbon nanotube of step a) to be dipped in palladium salt solution, is ultrasonically treated, obtains mixture, wherein palladium salt solution
It is dissolved in the solvent centainly measured for palladium salt；
C) the resulting mixture of whipping step b) makes solvent volatilization in mixture completely, obtain the oxygen of Pd/CNTs-in catalyst
Change state presoma；
D) the resulting oxidation state presoma of step c) is dry, with High Purity Hydrogen at 200~300 DEG C reductase 12~4h, obtain x%
Pd/CNTs-in catalyst.
8. application as described in claim 1, it is characterised in that:
The x%Pd/CNTs-out catalyst the preparation method is as follows:
A) carbon nanotube is placed in nitric acid solution, is stirred at reflux at 110~160 DEG C, be washed with deionized after cooling to
Upper liquid is neutrality, is filtered, dry, the carbon nanotube for the functionalization being open；
B) it takes the resulting carbon nanotube of step a) to be dipped in dimethylbenzene, is ultrasonically treated；
C) ammonium carbonate/ammonia spirit for preparing 0.5~1mol/L, palladium salt is dissolved in ammonium carbonate/ammonia spirit, and step b) is added
In resulting carbon nanotube and xylene mixture, stir evenly；
D) the resulting mixture of step c) is dry, High Purity Hydrogen reductase 12~4h at 200~300 DEG C is then used, x%Pd/ is obtained
CNTs-out catalyst.
9. the application of catalyst as claimed in claim 7, it is characterised in that:
In step b), palladium salt solution concentration is 0.02~0.2mol/L, solvent used be one of acetone, ethyl alcohol or water or
Two kinds of mixing；
In step c), temperature when stirring is 20~30 DEG C；
In step d), drying temperature be 60~80 DEG C, drying time be 12~for 24 hours.
10. the application of catalyst as claimed in claim 7, it is characterised in that:
In step b), palladium salt solution concentration is 0.1~0.15mol/L, and solvent used is acetone.
11. the application of catalyst as claimed in claim 8, it is characterised in that:
In step b), the mass ratio of carbon nanotube and dimethylbenzene is 1:20~1:30；
In step c), ammonium carbonate and the mass ratio of palladium salt are 20:1~40:1 in ammonium carbonate/ammonia spirit；
In step d), dry for continuously twice, first time drying temperature is 80~100 DEG C, drying time is 24~36h, the
Redrying temperature be 140~150 DEG C, drying time be 12~for 24 hours.
12. the application of catalyst as described in claim 7 or 8, it is characterised in that:
In step a), carbon nanotube is handled through nitric acid solution reflux oxidation, the mass ratio of nitric acid in carbon nanotube and nitric acid solution
For 1:40~1:60, nitric acid solution concentration is 34~68wt%, and return time is 8~16h, and reflux temperature is 130~150 DEG C,
Drying temperature is 60~80 DEG C, and drying time is 24~36h；
In step b), ultrasonic treatment uses ultrasonator, power 100W, and supersonic frequency is 28~100kHz, ultrasonic time
For 1~6h；
In system, the load capacity of palladium is 1~10wt%, and palladium salt used is one of palladium chloride, palladium acetate or palladium nitrate or two
Kind or more.
13. the application of catalyst as described in claim 7 or 8, it is characterised in that:
In step a), carbon nanotube is handled through nitric acid solution reflux oxidation, and nitric acid solution concentration is 50~68wt%, return time
For 10~14h；
In step b), ultrasonic treatment uses ultrasonator, supersonic frequency 45kHz, and ultrasonic time is 3~4h；
In system, palladium salt used is palladium chloride.
14. application as described in claim 1, it is characterised in that: palladium/carbon nano-tube catalyst is synthesized for hydrogenation of carbon dioxide
In methanol reaction, in 2.0~5.0MPa, 200~260 DEG C, material synthesis gas group becomes V (H2)/V(CO2)=2/1~4/1, it is empty
It is carried out under the fast reaction condition for GHSV=1000~5000mL/ (h g).
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