preparationandcatalyticpropertiesof iron … · 2019. 7. 31. · sps1500vr, seiko instruments inc....

International Scholarly Research NetworkISRN CeramicsVolume 2012, Article ID 305496, 5 pagesdoi:10.5402/2012/305496

Research Article

Preparation and Catalytic Properties ofIron-Cerium Phosphates with Sodium Dodecyl Sulfate

Hiroaki Onoda and Takeshi Sakumura

Department of Informatics and Environmental Sciences, Faculty of Life and Environmental Sciences, Kyoto Prefectural University,1-5 Shimogamo Nakaragi-cho, Sakyo-ku, Kyoto 606-8522, Japan

Correspondence should be addressed to Hiroaki Onoda, [email protected]

Received 28 August 2012; Accepted 12 September 2012

Academic Editors: S. Gutzov and P. Thavorniti

Copyright © 2012 H. Onoda and T. Sakumura. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Iron phosphate was prepared from iron nitrate and phosphoric acid with sodium dodecyl sulfate at various stirring hours.The chemical composition of the obtained samples was estimated from ICP and XRD measurements. Particle shape and sizedistribution were observed by SEM images and laser diffraction/scattering methods. Further, the catalytic activity was studiedwith the decomposition of the complex between formaldehyde, ammonium acetate, and acetylacetone. The peaks of FePO4 wereobserved in XRD patterns of samples prepared in Fe/Ce = 10/0 and then heated at 600◦C. Other samples were amorphous in XRDpatterns. Iron-cerium phosphates had high catalytic activity for the decomposition of the complex.

1. Introduction

Phosphates have been used for ceramic materials, catalysts,fluorescent materials, dielectric substances, metal surfacetreatment, detergent, food additives, fuel cells, pigments, andso forth [1–3]. In these uses, catalyst is one of importantapplications of phosphate materials. Vanadium phosphateworks as a catalyst for oxidation of butane [4]. Nickelphosphate works for oxidation of alcohol [5]. Iron phosphateworks for oxidation of methane [6]. Aluminum phosphateworks for dehydration of alcohol [7]. Other phosphates,zirconium, cobalt, potassium phosphates, and so on, are alsoimportant as a catalyst [8–10].

Transition metal phosphates sometimes have the differ-ent ratio of cation/phosphorus with the theoretical ratio ofchemical composition, because of hydrogen cation, hydrox-ide anion, and so on. These hydrogen cation and hydroxideanion have influence on the catalytic activity of phosphatematerials, because of the formation of hydrogen site onsurface. These transition metal phosphates work as solid stateacidic catalyst. Therefore, the synthetic process is importantto control the chemical composition of phosphate materials.Generally, the additives in preparation process were used toprepare the target particle of phosphate materials [11]. Thespherical and porous particles of lanthanum phosphate were

obtained by the addition of urea [12]. In this work, as anadditive, sodium dodecyl sulfate (SDS) was used to preventthe aggregation in preparation process, which was one of thecommon anionic surfactant.

Transition metal phosphates have a weak point to solvein acidic and basic solutions. In previous work [13], thesubstitution with rare earth cation inhibited the elutionof phosphates. Therefore, rare-earth-substituted iron phos-phates have a possibility to use as a catalyst in solutions.

In this work, iron-cerium phosphates were preparedform iron nitrate, ammonium cerium nitrate, and phos-phoric acid with sodium dodecyl sulfate. The ratios ofiron/cerium and sodium dodecyl sulfate/phosphorus werestudied in this preparation. The obtained products wereestimated from their particle shape, size distribution, andcatalytic activity. The purpose in this work is to clearthe influence of cerium substitution, SDS, and heatingtemperature on chemical composition and catalytic activityof iron phosphates.

2. Experimental Procedure

The 0.2 mol/L of iron nitrate, Fe(NO3)3, solution was mixedwith 0.2 mol/L of phosphoric acid solution in the molar

2 ISRN Ceramics

Table 1: Chemical composition of precipitates from ICP measurements.

Preparation Precipitate, FexCeyHzPO4

Fe/Ce SDS/P x y z Fe/Ce

A 10/0 0/10 0.695 — 0.915 —

B 8/2 0/10 0.594 0.122 0.729 8/1.64

C 10/0 1/10 0.826 — 0.522 —

D 8/2 1/10 0.601 0.125 0.696 8/1.66

E 10/0 2/10 0.815 — 0.555 —

F 8/2 2/10 0.589 0.122 0.825 8/1.66

ratio of Fe/P = 1/1. This ratio is settled from the chemicalcomposition of iron orthophosphate, FePO4. Then, themixed solution was adjusted to pH 3 by ammonia solution.Sodium dodecyl sulfate (SDS) was added to the mixedsolution in SDS/P = 0/10, 1/10, and 2/10 to prevent theaggregation of particles. When sodium dodecyl sulfate wasadded before pH adjustment, the mass of particles wasformed. Therefore, sodium dodecyl sulfate was added afterpH adjustment. The phosphate particles were dispersed inthe solution by the addition of sodium dodecyl sulfate afterpH adjustment. Further, the mixed solution was stirred for24 hours. The precipitate was decantated off and dried at60◦C in air condition. The cerium-substituted samples werealso prepared to compare with iron phosphates. A part ofiron nitrate was substituted with ammonium cerium nitrate,(NH4)2Ce(NO3)6, in Fe/Ce = 8/2. The four iron (+III)cations were replaced with three cerium (+IV) cation. In thiswork, the ratio of P/(3Fe + 4Ce) was 1/3. All chemicals wereof guaranteed reagents from Wako Chemical Industries Ltd.(Osaka, Japan) without further purification.

A part of the precipitates was dissolved in hydrochloricacid solution. The ratios of phosphorus, iron, and ceriumin the precipitates were also calculated from InductivelyCoupled Plasma (ICP) results of these solutions, usingSPS1500VR, Seiko Instruments Inc. The thermal behaviorof these materials was analyzed by X-ray diffraction (XRD).XRD patterns were recorded on a Rigaku MiniFlex X-Raydiffractometer using monochromated CuKα radiation.

The powder properties of thermal products at 60, 200,400, and 600◦C were characterized by particle shape andsize distribution. Particle shapes were observed by scanningelectron micrographs (SEMs) using JGM-5510LV, JEOLLtd. Particle size distribution was measured with laserdiffraction/scattering particle size distribution HORIBA LA-910.

Further, as an application of phosphates, the catalyticactivity of these iron-cerium phosphates was studied with thedecomposition of the following complex:

CH3

CH3

CH3

CH3

+NH

HCHO H2O + CH3COONH4 + 2CH3COCH2COCH3

O O−

+ CH3COOH + 4H2O

−→·

(1)

10 20 30 40 50 60

Inte

nsi

ty

(a)

(c)

(d)

(e)

(f)

(b)

2θ (deg)

Figure 1: XRD patterns of samples heated at 600◦C, (a) Fe/Ce =10/0, SDS/P = 0/10, (b) 8/2, 0/10, (c) 10/0, 1/10, (d) 8/2, 1/10, (e)10/0, 2/10, and (f) 8/2, 2/10, •; FePO4.

Formaldehyde formed the complex with ammoniumacetate and acetylacetone. This complex has the light adsorp-tion at 415 nm. Samples were added in this solution andthen shaken for 24 hours. The strong catalyst decomposedthis complex. Therefore, the adsorption at 415 nm becamesmall. The catalytic activity of iron-cerium phosphate wasestimated from this adsorption at 415 nm.

3. Results and Discussion

3.1. Chemical Composition and Powder Properties of Iron-Cerium Phosphates. All obtained samples were yellow pow-der in color, therefore the iron condition in precipitate ismainly trivalent state. Table 1 shows the chemical compo-sition of precipitates from ICP measurements. Because theFe/P ratio in iron phosphate, FePO4, is 1, samples containeda certain degree of proton, like Fe0.695H0.915PO4. The Fe/Pratio became higher from 0.7 to 0.82 by the addition ofsodium dodecyl sulfate. The presence of proton is importantto be used as a phosphate catalyst. The cerium ratio in

ISRN Ceramics 3

(a)

10 μm

(b)

10 μm

(c)

10 μm

(d)

10 μm

Figure 2: SEM images of samples (60◦C), (a) Fe/Ce = 10/0, SDS/P = 0/10, (b) Fe/Ce = 8/2, SDS/P = 0/10, (c) Fe/Ce = 8/2, SDS/P = 1/10, and(d) Fe/Ce = 8/2, SDS/P = 2/10.

0

2

4

6

1 10 100 1000

(a)(b)

Nu

mbe

r of

par

ticl

es (

%)

Particle size (μm)

Figure 3: Particle size distribution of samples (60◦C, SDS/P = 0/10),(a) Fe/Ce = 10/0 and (b) 8/2.

precipitate was lower than that of preparation condition. Inprevious works [14, 15], lanthanum ratio in precipitates washigher than that in preparation condition. This differenceis considered to be from the valence state of rare earthcation. Cerium cation in this work is tetravalent one, on theother hand, lanthanum cation in previous works is trivalentone. Trivalent rare earth cation was much easy to react to

0

20

40

60

80

100

0 200 400 600

(a)(b)

Res

idu

al r

atio

(%

)

Temperature (◦C)

Figure 4: Catalytic activity of samples (SDS/P = 0/10), (a) Fe/Ce =10/0 and (b) 8/2.

phosphate materials. It is well known that trivalent rareearth phosphates are a main composition of Monazite oreand insoluble for acidic and basic solution in the groups ofphosphate materials. The addition of sodium dodecyl sulfatehad less influence on the Fe/Ce ratio in precipitates.

Samples heated at 60, 200, and 400◦C were amorphousin XRD patterns. Generally, phosphate materials preparedin a solution are amorphous in XRD analysis. Amorphous

4 ISRN Ceramics

0

20

40

60

80

100

0 200 400 600

(a)

(b)

(c)

Res

idu

al r

atio

(%

)

Temperature (◦C)

Figure 5: Catalytic activity of samples (Fe/Ce = 10/0), (a) SDS/P =0/10, (b) 1/10, and (c) 2/10.

phosphate materials were expected to have various kinds ofacidic sites to work as an acidic catalyst. Figure 1 shows XRDpatterns of samples heated at 600◦C. Samples prepared inFe/Ce = 10/0 had peaks of FePO4 in spite of the SDS ratio(Figures 1(a), 1(c), and 1(e)). On the other hand, samplesprepared in Fe/Ce = 8/2 were amorphous or had small peaksin XRD patterns (Figures 1(b), 1(d), and 1(f)).

Figure 2 shows SEM images of samples prepared invarious conditions. No specified shapes were observed in thiswork. By the substitution with cerium cation, large particleswere formed (Figures 2(a) and 2(b)). The addition of sodiumdodecyl sulfate made the particle size of phosphates smaller(Figures 2(b), 2(c), and 2(d)). The heating temperature hadno influence on particle shape of iron-cerium phosphates.Particle size distribution of samples was estimated forcatalytic reaction in the complex solution. Figure 3 showsthe particle size distribution of samples prepared in Fe/Ce= 10/0 and 8/2. The particle sizes of samples were from2 to 800 μm. Sample prepared in Fe/Ce = 8/2 had largerparticles than 100 μm in size. The amount of large particlesbecame smaller by the addition of sodium dodecyl sulfate(not shown). The heating temperature had little change onparticle size distribution of iron-cerium phosphates.

3.2. Catalytic Properties of Iron-Cerium Phosphates. Figure 4shows the catalytic activity of samples prepared in Fe/Ce =10/0 and 8/2 from the adsorption at 415 nm. The residualratio in absorbance was calculated on the basis of thatwithout catalyst. The low residual ratio means high catalyticactivity of iron-cerium phosphates. Sulfuric acid, as one ofcommon acidic catalysts, had about 30% of the residual

ratio in this reaction. In previous work [16], iron phosphatesheated at 60 and 600◦C indicated low catalytic activity.Because samples heated at 60◦C had large particles, theamount of acidic sites on surface of particles was small. Fromthe results of samples heated at 600◦C, the crystalline ironphosphate was considered to have little catalytic activity. Inthis work, samples prepared in Fe/Ce = 10/0 and then heatedat 60 and 600◦C indicated low catalytic activity. These resultshad same tendency with previous work. Samples prepared inFe/Ce = 8/2 and then heated at 60, 200, and 600◦C had highcatalytic activity. The substitution with cerium prevented thecrystallization of iron phosphate, therefore, sample heatedat 600◦C (Fe/Ce = 8/2) indicated high catalytic activity.Figure 5 shows the catalytic activity of samples preparedwith various SDS ratios. Samples prepared with SDS/P =1/10 and 2/10 had higher catalytic activity than sampleprepared without sodium dodecyl sulfate. Because samplesprepared with sodium dodecyl sulfate had smaller particles,the complex came into contact with phosphate catalysts.

4. Conclusions

Iron-cerium phosphates were prepared from iron nitrate,ammonium cerium nitrate, and phosphoric acid withsodium dodecyl sulfate. The obtained phosphates wereyellow powder in color, therefore the iron condition inprecipitate is mainly trivalent state. All samples had highhydrogen ratio in spite of the changes of the Fe/Ce andP/SDS ratios. The peaks of FePO4 were observed in XRDpatterns of samples prepared in Fe/Ce = 10/0 and thenheated at 600◦C. Other samples were amorphous in XRDpatterns. The particle size of samples prepared in Fe/Ce =8/2 was larger than that in Fe/Ce = 10/0. Samples preparedin Fe/Ce = 8/2 and then heated at 60, 200, and 600◦Cindicated high catalytic activity for the decomposition ofthe complex from formaldehyde, ammonium acetate, andacetylacetone.

References

[1] H. Onoda, H. Nariai, A. Moriwaki, H. Maki, and I. Motooka,“Formation and catalytic characterization of various rareearth phosphates,” Journal of Materials Chemistry, vol. 12, no.6, pp. 1754–1760, 2002.

[2] H. Onoda, T. Ohta, J. Tamaki, and K. Kojima, “Decompositionof trifluoromethane over nickel pyrophosphate catalysts con-taining metal cation,” Applied Catalysis A, vol. 288, no. 1-2, pp.98–103, 2005.

[3] H. Onoda, K. Yokouchi, and K. Kojima H, “Addition of rareearth cation on formation and properties of various cobaltphosphates,” Materials Science and Engineering: B, vol. 116, no.2, pp. 189–195, 2005.

[4] W. J. Tang, “Physico-Chemical Properties and Oxygen SpeciesBehavior of Bulk and Modified Vanadium Phosphate Catalystfor Partial Oxidation of N-Butane,” [Ph.D. thesis], UniversityPutra, Malaysia, 2008.

[5] C. Li, H. Kawada, X. Sun, H. Xu, Y. Yoneyama, and N. Tsubaki,“highly efficient alcohol oxidation on nanoporous VSB-5nickel phosphate catalyst functionalized by naoh treatment,”ChemCatChem, vol. 3, no. 4, pp. 684–689, 2011.

ISRN Ceramics 5

[6] X. Wang, Y. Wang, Q. Tang, Q. Guo, Q. Zhang, and H.Wan, “MCM-41-supported iron phosphate catalyst for partialoxidation of methane to oxygenates with oxygen and nitrousoxide,” Journal of Catalysis, vol. 217, no. 2, pp. 457–467, 2003.

[7] F. Yaripour, F. Baghaei, I. Schmidt, and J. Perregaarad,“Synthesis of dimethyl ether from methanol over aluminiumphosphate and silica-titania catalysts,” Catalysis Communica-tions, vol. 6, no. 8, pp. 542–549, 2005.

[8] N. Li, G. A. Tompsett, and G. W. Huber, “Renewable high-octane gasoline by aqueous-phase hydrodeoxygenation of C5and C6 carbohydrates over Pt/zirconium phosphate catalysts,”ChemSusChem, vol. 3, no. 10, pp. 1154–1157, 2010.

[9] D. K. Zhong, M. Cornuz, K. Sivula, M. Gratzel, and D.R. Gamelin, “Photo-assisted electrodeposition of cobalt-phosphate (Co-Pi) catalyst on hematite photoanodes for solarwater oxidation,” Energy and Environmental Science, vol. 4, no.5, pp. 1759–1764, 2011.

[10] G. Guan, K. Kusakabe, and S. Yamasaki, “Tri-potassiumphosphate as a solid catalyst for biodiesel production fromwaste cooking oil,” Fuel Processing Technology, vol. 90, no. 4,pp. 520–524, 2009.

[11] H. Onoda, K. Asai, and A. Takenaka, “Preparation of nickelphosphates with various acidic and basic compounds,” Journalof Ceramic Processing Research, vol. 12, no. 4, pp. 439–442,2011.

[12] H. Onoda, K. Taniguchi, and I. Tanaka, “Preparation andacidic properties of nano-porous lanthanum phosphate by theaddition of urea,” Microporous and Mesoporous Materials, vol.109, no. 1-3, pp. 193–198, 2008.

[13] H. Onoda and T. Sakumura, “Synthesis and pigmental prop-erties of nickel phosphates by the substitution with tetravalentcerium cation,” Materials Sciences and Applications, vol. 2, no.11, pp. 1578–1583, 2011.

[14] H. Onoda, H. Matsui, and I. Tanaka, “Improvement ofacid and base resistance of nickel phosphate pigment bythe addition of lanthanum cation,” Materials Science andEngineering: B, vol. 141, no. 1-2, pp. 28–33, 2007.

[15] H. Onoda, K. Tange, and I. Tanaka, “Influence of lanthanumaddition on preparation and powder properties of cobaltphosphates,” Journal of Materials Science, vol. 43, no. 16, pp.5483–5488, 2008.

[16] H. Onoda and T. Sakumura, “Preparation and acidic prop-erties of iron phosphates with sodium dodecyl-sulfate,” Phos-phorus Research Bulletin, vol. 27, pp. 28–32, 2012.

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preparationandcatalyticpropertiesof iron … · 2019. 7. 31. · sps1500vr, seiko instruments inc....

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