CN104923271A - Supported fluorine-doped and nitrogen-fluorine co-doped titanium dioxide for acrylonitrile photocatalytic degradation - Google Patents

Abstract

The invention relates to a supported modified titanium dioxide composite oxide catalyst and a preparation method thereof; wherein the catalyst is applied to acrylonitrile photocatalytic degradation under two simulated sunlight radiation conditions. At first, two catalysts capable of removing acrylonitrile through photo catalysis are provided; a sol-gel method is adopted to prepare titanium dioxide, then hydrogen fluoride or ammonium fluoride is taken as the doping precursor to modify titanium dioxide, fluorine or nitrogen-fluorine is doped into titanium dioxide, and finally the modified titanium dioxide is loaded on a silicon dioxide carrier; wherein the size of silicon dioxide is 100 to 200 meshes. The catalyst prepared by the method mentioned above greatly improves the efficiency of acrylonitrile photocatalytic degradation. The prepared catalyst is applied to acrylonitrile photocatalytic degradation under simulated sunlight radiation, after six minutes of radiation, the degradation rate can reach 65.9%, if a supported fluorine-doped titanium dioxide catalyst is used; and the degradation rate can reach 71.5% if a supported nitrogen-fluorine co-doped titanium dioxide catalyst is used.

Description

Photocatalytic degradation acrylonitrile support type Fluorin doped and nitrogen fluorine mix titanium dioxide altogether

Technical field

The present invention relates to acrylonitrile photocatalytic degradation composite oxide catalysts in two kinds of aqueous phases, specifically, relating in aqueous phase acrylonitrile photocatalytic degradation silica as supporting Fluorin doped or nitrogen fluorine mixes photochemical catalyst of the titanium dioxide of modification and preparation method thereof altogether, belonging to environmental technology field.

Background technology

Acrylonitrile (acrylonitrile, CH2=CH-CN are called for short AN) is the monomer of synthesis ABS industrial plastic, acrylic fiber, acrylonitrile-butadiene rubber and resin, is therefore a kind of important chemical raw material.Although acrylonitrile has very large use, acrylonitrile is then more and more serious at the various problem of environmental pollutions produced and bring in use procedure.Be number four in the toxic chemical list of the 52 kinds of priority acccess control determined in China, there is high toxicity and potential genetoxic.Relevant expert's research is thought, acrylonitrile is also a kind of serious carcinogen.Acrylic nitrile waste water not only destroys water ecosystem, and has very large harmfulness to the health of the mankind.Because there is very large demand in market to acrylonitrile, so acrylonitrile has huge output, but endanger environment and human health simultaneously.So the process of Wastewater from Acrylonitrile Production has become a hang-up of acrylonitrile process enterprise.At present, the method for traditional process acrylonitrile has absorption method, burning method, cyclic activated sludge process etc.But these method costs are higher, or remove insufficient, or condition of work is required harsh.

From Fujishima and Honda Late Cambrian TiO in 1972 ₂after Single Crystalline Electrodes has the function of light decomposition water, the heterogeneous light-catalyzed reaction of semiconductor causes the great interest of people.The Mitsui of Japan pushes practicality to gas-solid phase photocatalysis air-cleaning technology first.Photocatalyst oxidizes reduction mechanism mainly catalyst is subject to UV-irradiation, absorb luminous energy, there is electron transition, generate electron hole pair, directly redox is carried out to the pollutant being adsorbed in surface, or the hydroxyl of oxidized surface absorption, generate the hydroxyl free radical of strong oxidizing property, pollutant is oxidized.Due to semiconductor light-catalyst TiO ₂inorganic matter, nontoxic, cheap, and can be harmless material by the most of organic substance decomposing be present in air and aqueous phase, from having formed very promising environmental protection catalyst.But photochemical catalytic oxidation also has a lot of defect, such as lower reaction rate, effectively can not utilize visible ray, easily reunite, easy in inactivation and difficultly to reclaim.These seriously limit TiO ₂application in waste gas and wastewater treatment.

TiO ₂photocatalytic activity can increase its specific area by adding silica gel and obtain raising.In recent years, a lot of bibliographical information mode of loading of titanium dioxide, such as activated carbon loaded TiO ₂, molecular sieve carried TiO ₂, bead load TiO ₂, silicon dioxide carried TiO ₂.Utilize carrier adsorption characteristic can improve the mineralization ability of catalyst to degradation of contaminant.The activity of load rear catalyst is greatly improved compared with the activity of non-loaded titanium dioxide, this is because can form cooperative effect between titanium dioxide and carrier.Wherein silica absorption property is good, and specific area is larger.Silicon dioxide carried TiO ₂a kind of loaded catalyst of function admirable, the heat endurance of this kind of existing silica of catalyst and mechanical stability, and be the transparent body of light, the scattering of light can be reduced, thus effectively can improve the degradation property of catalyst.Add SiO ₂can control TiO effectively ₂crystal grain grow up, the effective agglomeration suppressing catalyst, makes catalyst obtain less particle diameter and higher specific area.The TiO of load on silica gel ₂also can there is interface with silica to spread, form Si-O-Ti key.The formation of Si-O-Ti key can suppress the TiO of anatase titanium dioxide ₂to the TiO of rutile-type ₂change.

Calendar year 2001 Asahi reports N doping on " science " magazine can make TiO ₂band gap narrow, thus make TiO ₂also there is activity under visible light illumination.From then on nonmetallic ion-doped own through becoming expansion TiO ₂the important modification method utilized under visible light.Nonmetal doping modification is utilized to improve TiO ₂the active advantage of is can at expansion TiO ₂the catalytic activity of catalyst ultraviolet light is not had influence on again while visible light catalysis activity.Nonmetal doping TiO such as having synthesized F, C, S, P, B, N has been studied at present by multiple catalysts preparation method ₂.In addition, as everyone knows, the particle diameter of catalyst, shape, composition and crystalline phase affect TiO strongly ₂photocatalysis performance.In various form, spherical TiO ₂particle has good individual layer and stability.Pan etc. report the mesoporous F doped Ti O of Monolayer Dispersion ₂there is excellent light in dye degrades collect performance and there is good photocatalytic activity.HF as the doping presoma in fluorine source, and can not only make it have morphology Control function due to its etching property.Also have and report that F doping can reduce the restructuring in photoinduced electron and hole thus improve photocatalysis performance.

The effective approach of another one is the quantity increasing its surface acid site.Confirm that photocatalytic activity strengthens along with increasing of catalyst surface acidic site.The nineteen ninety-fives such as Cui report can by doped metallic oxide TiO ₂increase its surface acidity and photocatalytic activity.Wang etc. report indefinite form TiO for 2006 ₂at high temperature sulfur doping TiO can be synthesized with sulphur compound ₂, having acidic site can as photochemical catalyst.But few people's report acidic catalyst carrys out photocatalytic degradation acrylonitrile.

penetrate down etc. reporting UV illumination, improve sulfuration TiO by improving temperature and extending the reaction time ₂photochemical catalytic oxidation gas-phase propene nitrile.Krichevskaya etc. report UV illumination and penetrate down, use P25 to carry out photocatalytic degradation gas-phase propene nitrile.But the report of the photocatalytic degradation of acrylonitrile is less in liquid phase.

Summary of the invention

For solving the problem, the object of the present invention is to provide two kinds of photochemical catalysts of acrylonitrile photocatalytic degradation in aqueous phase, with 100-200 object silica for carrier, using hydrogen fluoride or ammonium fluoride as doping presoma, prepare the catalyst of the bigger serface with meso-hole structure, its photocatalytic activity is higher.

The present invention also aims to the preparation method of the catalyst that acrylonitrile photocatalytic degradation in above-mentioned aqueous phase is provided, the titania composite oxide catalyst utilizing sol-gal process to prepare silica supported Fluorin doped or nitrogen fluorine to mix altogether.

The present inventor is found by research, and in the aqueous solution, the Photocatalytic activity of acrylonitrile and titanium dioxide load capacity on silica have much relations.Support type Fluorin doped of the present invention or nitrogen fluorine mix titanium deoxide catalyst altogether to have silica compared with bigger serface for carrier, it has larger reference area, so prepared photochemical catalyst also has larger specific area, make it have stronger adsorption capacity, its degrading activity improves a lot than the photochemical catalyst of non-load.

In order to improve the photocatalytic activity of catalyst further, composite oxide catalysts provided by the present invention adopts Fluorin doped.With in sol-gal process preparation process, aqueous hydrogen fluoride solution is joined in catalyst as doping presoma, and then high-temperature calcination forms Fluorin doped catalyst, can greatly improve its photocatalytic activity.

Composite oxide catalysts provided by the present invention also can adopt nitrogen fluorine to mix altogether.With in sol-gal process preparation process, ammonium fluoride aqueous solution is joined in catalyst as doping presoma, and then high-temperature calcination forms nitrogen fluorine and mixes catalyst altogether, thus improve its photocatalytic activity.

Present invention also offers the preparation method of above-mentioned compound oxide photocatalyst, it comprises the following steps:

10mL absolute ethyl alcohol, the presoma mix and blend of 0.5mL water and a certain amount of fluorine or nitrogen fluorine forms solution A.Wherein the presoma of fluorine is the aqueous hydrogen fluoride solution of commercially available 40%, and the presoma of nitrogen fluorine is the ammonium fluoride aqueous solution of 13.83mol/L.

The butyl titanate of 5mL is joined in the 13mL absolute ethyl alcohol of vigorous stirring, form solution B.

Solution A is added drop-wise in the solution B of vigorous stirring, dropwises rear continuation stirring and form colloidal sol in two hours, 100-200 object porous silicon glueballs is joined in sol solution, then continue to stir until form transparent or semitransparent gel.

By the gel of formation at room temperature, place 12h and carry out aging, then dry in 80 DEG C of baking ovens, until obtain dry gel.

By the gel of drying mortar porphyrize, be then placed in Muffle furnace and calcine two hours at a certain temperature, what obtain is that support type F adulterates or NF mixes TiO altogether ₂/ SiO ₂composite oxide catalysts.

According to concrete technical scheme of the present invention, the addition of hydrogen fluoride or ammonium fluoride aqueous solution adds according to predetermined stoichiometric proportion.The mol ratio of HF/Ti is respectively 0:1, and 0.3: 1,0.7: 1,1.1: 1 and 2.0: 1.NH ₄the mol ratio of F/Ti is respectively 0: 1, and 0.2: 1,0.4: 1,0.8: 1 and 1.6: 1.

According to concrete technical scheme of the present invention, the particle size of the silica gel adopted is 100-200 order.TiO ₂load capacity be respectively 16%, 22%, 36%, 53%, 70%, 100%.

According to concrete technical scheme of the present invention, the calcining heat that this programme adopts is respectively 350 DEG C, 450 DEG C, 550 DEG C and 650 DEG C, and calcining atmosphere is air.

By comparing can learn the activity of catalyst, the support type Fluorin doped of bigger serface prepared by the present invention or nitrogen fluorine mix type titania composite oxide photochemical catalyst altogether than corresponding non-supported catalyst, and non-doped catalyst has better photocatalytic activity.

Accompanying drawing explanation

Fig. 1 is the support type F doped Ti O of preparation ₂/ SiO ₂the electromicroscopic photograph of composite oxides;

Fig. 2 is support type F doped Ti O ₂/ SiO ₂the observed rate constant of composite oxides and the graph of relation of load capacity;

Fig. 3 is support type F doped Ti O ₂/ SiO ₂the doping of the F of composite oxides and the graph of relation of observed rate constant;

Fig. 4 is the support type F doped Ti O of preparation ₂/ SiO ₂the X ray diffracting spectrum of composite oxides under different calcining heat;

Fig. 5 is that the support type NF of preparation mixes TiO altogether ₂/ SiO ₂the electromicroscopic photograph of composite oxides;

Fig. 6 is that support type NF mixes TiO altogether ₂/ SiO ₂the observed rate constant of composite oxides and the graph of relation of load capacity;

Fig. 7 is that support type NF mixes TiO altogether ₂/ SiO ₂the doping of the NF of composite oxides and the graph of relation of observed rate constant;

Fig. 8 is that the support type NF of preparation mixes TiO altogether ₂/ SiO ₂the X ray diffracting spectrum of composite oxides under different calcining heat;

Fig. 9 is the support type F doped Ti O of preparation ₂/ SiO ₂composite oxides and support type NF mix TiO altogether ₂/ SiO ₂composite oxides and non-doped Ti O ₂/ SiO ₂the photocatalytic activity contrast of composite oxides under solar simulated condition is irradiated.

Detailed description of the invention

The excellent effect introduced realization of the present invention below by way of specific embodiment and have, but any restriction should do not formed to practical range of the present invention accordingly.

The evaluation method of catalyst activity:

The spherical xenon lamp of concrete steps: 350W is as the light source of solar simulated.0.5g catalyst sample is dissolved in the acrylonitrile aqueous solution of 180mL10mg/L, is placed in 250mL sealed reactor.Before illumination, suspension agitation 60min reaches adsorption/desorption balance.Open light source, open outside cooling water recirculation system simultaneously and make it maintain 25 DEG C.Water sampling at a fixed time, uses the membrane filtration of 0.45 micron, measures with HPLC.

Detection method: the concentration of acrylonitrile adopts high effective liquid chromatography for measuring.High performance liquid chromatography is the beautiful LC2000 in sky, and detector is LC-2030 UV-detector; Chromatographic column is SunfireTM C18,4.6mm × 150mm Column.The mobile phase adopted is: methyl alcohol (high performance liquid chromatography is pure): water (ultra-pure water)=3: 7 (volume ratio), and its flow velocity is 1mL/min.The characteristic wavelength selected is 210nm.

Evaluation method: the photocatalytic activity of prepared catalyst can be evaluated by observed rate constant.Its computational methods are

$\mathrm{In}\left(\frac{C_o}{C}\right)=k_{\mathrm{app}}t$

Also can be evaluated by the clearance of acrylonitrile.Its computational methods are

$\frac{C_o-C}{C_o}\×100\%$

In formula, C ₀for the concentration (mg/L) of acrylonitrile in solution before illumination; C is the concentration (mg/L) of acrylonitrile in illumination t solution; k _appfor observed rate constant (min ^-1); D is the degradation rate of acrylonitrile.

The mode of appearance of catalyst is evaluated by SEM photo.

Fig. 1 is support type F doped Ti O prepared by the present embodiment ₂/ SiO ₂the electromicroscopic photograph of composite oxides.Support type F doped Ti O as can be seen from Figure ₂/ SiO ₂composite oxides do not have serious gathering, grained matte, uniform particle sizes.

Table 1

Table 1 provides support type F doped Ti O ₂/ SiO ₂the BET surface area of the sample of the different loads amount of composite oxides and total pore volume.Along with TiO ₂the increase of load capacity, BET specific surface area and total pore volume reduce gradually, and TiO is described ₂well be dispersed in the hole of silica gel.And the sample after load has higher specific area compared to not having non-loaded catalyst.

Activity rating 1

Evaluate according to the above-mentioned composite oxides of method to the different loads amount of F doping prepared by embodiment to catalyst activity evaluation, Activity evaluation is shown in Fig. 2.SiO ₂existence make it have larger specific area.Its active component TiO is made along with the increase of load capacity ₂increase thus add its photocatalytic activity.

Activity rating 2

Support type F doped Ti O ₂/ SiO ₂the activity rating of the various HF doping of composite oxides as shown in Figure 3.It is best to the Photocatalytic activity of acrylonitrile in 1.1: 1 for the mol ratio of HF and Ti as seen from the figure.

In the present embodiment, the support type F doped Ti O prepared under different calcining heats ₂/ SiO ₂the XRD of composite oxides as shown in Figure 4.Its diffraction maximum is anatase TiO ₂characteristic peak, there is not the phase transformation to rutile.And along with the increase of calcining heat, anatase peak intensity increases, and peak shape comes to a point, and illustrates that relative crystallinity increases.

Activity rating 3

Fig. 5 is that support type NF prepared by the present embodiment mixes TiO altogether ₂/ SiO ₂the electromicroscopic photograph of composite oxides.Support type NF mixes TiO altogether as seen from the figure ₂/ SiO ₂composite oxides are assembled less, and aggregated particle is 200-500nm, is less than non-doped samples.

Table 2

Table 2 provides BET surface area and the total pore volume of the different loads amount sample of the composite oxides that support type NF mixes altogether.Along with the increase of load capacity, BET specific surface area and total pore volume reduce gradually, and TiO is described ₂well be dispersed in the hole of silica gel.SiO ₂existence substantially increase the specific area of sample.

Activity rating 4

According to above-mentioned the composite oxides of method to the different loads amount that NF prepared by embodiment mixes altogether of catalyst activity evaluation are evaluated the results are shown in Figure 6.Its active component TiO is made along with the increase of load capacity ₂increase thus add its photocatalytic activity.When load capacity is 36%, it has maximum photocatalytic activity to the degraded of acrylonitrile.

Activity rating 5

Fig. 7 is that support type NF mixes TiO altogether ₂/ SiO ₂the graph of relation of the different NF doping of composite oxides and the observed rate constant of corresponding catalyst.As can be seen from the figure, at NH ₄during F/Ti=0.8, it has best photocatalytic activity.

Fig. 8 mixes TiO altogether for the support type NF prepared by under different calcining heat ₂/ SiO ₂the XRD collection of illustrative plates of composite oxides.As can be seen from the figure all collection of illustrative plates all only have the composition of anatase, do not undergo phase transition.And along with the enhancing of calcining heat, peak intensity grow, peak type comes to a point, and illustrates that its relative crystallinity increases.

Activity rating 6

Fig. 9 is that the support type F for preparing of the present embodiment adulterates and NF mixes TiO altogether ₂/ SiO ₂the photocatalytic activity of composite oxides under solar simulated condition is irradiated.As can be seen from Figure under solar simulated is irradiated, support type F adulterates and NF mixes TiO altogether ₂/ SiO ₂composite oxides all have stronger photocatalytic activity, and its photocatalytic activity can reach 65.9% and 71.5% respectively, far above non-doped samples.

Claims (6)

1. two kinds of acrylonitrile photocatalytic degradation composite oxide catalysts, it is that titanium dioxide using 100-200 object silica as carrier loaded modification obtains.Wherein said being modified as is come titania-doped by hydrogen fluoride or ammonium fluoride as fluorine source or nitrogen fluorine source.

2. as right 1 require as described in the preparation method of composite oxide catalysts, it comprises the following steps:

(1) 10mL absolute ethyl alcohol, the predecessor of a certain amount of fluorine or nitrogen fluorine, 2mL glacial acetic acid mix and blend forms solution A.

(2) 5mL butyl titanate is joined in the 13mL absolute ethyl alcohol of vigorous stirring, drip rear continuation and stir 20min, form solution B.

(3) solution A is added drop-wise in the solution B of vigorous stirring, rate of addition is 0.5mL/min, dropwises rear continuation stirring two hours, joins in mixed liquor by 100-200 object porous silicon glueballs, then continue stirring one hour, form transparent or semitransparent gel.

(4) by the gel of formation at room temperature, place 12 hours, carry out aging, then dry in 80 DEG C of air dry ovens, until obtain dry gel.

(5) by the gel of drying mortar porphyrize, be placed in Muffle furnace and calcine two hours at a certain temperature, then just obtain required catalyst.

3. as described in claim 2 preparation method, wherein, the predecessor of fluorine is the aqueous hydrogen fluoride solution of commercially available 40%, and the predecessor of nitrogen fluorine is the ammonium fluoride aqueous solution of the 13.83mol/L prepared with analytically pure ammonium fluoride.

4. as described in claim 2 preparation method, wherein, calcining heat is 350 DEG C, 450 DEG C, 550 DEG C and 650 DEG C, and the highest to calcine prepared catalyst activity at 450 DEG C.

5. preparation method as described in claim 2, wherein, the support type Fluorin doped titania composite oxide of addition prepared by 0.7mL of aqueous hydrogen fluoride solution has best activity, and load type nitrogen fluorine prepared when the addition of ammonium fluoride aqueous solution is 0.85mL mixes titania composite oxide catalyst altogether best activity.

6. preparation method according to claim 2, the method characteristic that this catalyst has high efficiency photocatalysis degraded acrylonitrile is owing to using silica as carrier and use hydrogen fluoride to be doped with fluorine or use ammonium fluoride to be doped with nitrogen fluorine.