Research Article Improvement the Activity and Selectivity ...downloads.hindawi.com/archive/2014/823054.pdfResearch Article Improvement the Activity and Selectivity of Fenton System

Research ArticleImprovement the Activity and Selectivity of Fenton System inthe Oxidation of Alcohols

Guoqiang Yang Qiuxing Lin Xingbang Hu Youting Wu and Zhibing Zhang

School of Chemistry and Chemical Engineering and National Engineering Research Center for Organic Pollution Control and ResourceNanjing University Nanjing 210093 China

Correspondence should be addressed to Xingbang Hu huxbnjueducn and Youting Wu ytwunjueducn

Received 18 October 2013 Accepted 23 February 2014 Published 24 March 2014

Academic Editor David W Mazyck

Copyright copy 2014 Guoqiang Yang et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The reactivity and selectivity of Fenton system (Fe2+H2O2) were improved with N-hydroxyphthalimide (NHPI) as cocatalyst The

oxidation process of benzyl alcohol to benzaldehyde has been studiedThe reaction catalyzed by this new Fe2+H2O2NHPI system

can be well performed under room temperature without adding any organic solvent Besides this catalyst system is effective for theoxidation of different alcohols

1 Introduction

The Fenton reagent is a simple catalyst system which is com-posed of Fe2+ andH

2O2 In the reaction process with Fentonrsquos

reagent the hydroxyl radicals are generated rapidly at thepresence of ferrous ion This catalyst system is proved to besuccessful for the treatment of organic pollutants in industrialwastewater [1ndash12] There are numerous reports concerningpretreatment option to improve the biodegradability of com-plex wastes and recalcitrant from industry wastewater andlandfill leachate [2ndash4]The original pollutants are often trans-formed to CO

2andH

2Odue to the strong oxidizing property

of the Fenton system [4ndash7] In recent studies Fenton systemis coupled with other methods such as membrane filtrationand coagulation to degrade organic compounds to a largerextent [8 9] Besides the Fenton reagent is also effective inlight alcohols and alkanersquos oxyfunctionalization [10 13] butthe application for selective oxidation is rare [11 12]

The Fenton system has wonderful water solubility andthere are abundant ferrous irons on the earth Thus it is pos-sible to develop amild and inexpensive water phase oxidationprocess using this system Despite its numerous advantagesone limitation of traditional Fentonrsquos reagent must be takeninto account its high oxygen reactivity which often leadsto deep oxidation [5 6 14ndash16] To apply the Fenton systemin chemical synthesis the most crucial problem is how to

control its reactivity and enhance its selectivityThe efficiencyof Fentonrsquos reagent is affected by various factors such aspH the counterion of Fe2+ solvent iron chelation UVand microwaves which control the oxidation reactivity andregeneration ability of Fe2+ from Fe3+ [4 17ndash20] In additionit has been found that the additives play a vital role to changethe reactivity of Fenton system [13 21ndash23] For example thereaction with KH

2PO4as additive provided high conversion

and good selectivity in the oxidation of benzyl alcohol [13]The objective of this study is to control the reactivity of

Fenton system and enhance its selectivity Based on a detailedinvestigation on a series of additives we have found thatthe reactivity of Fenton system can be well controlled andthe benzyl alcohol oxidation can be performed with goodselectivity at room temperature in water

2 Experimental

All the chemicals were obtained with purities higher than99 A typical experiment was carried out in a water bathThe alcohol (20mmol) FeSO

4sdot7H2O (05mmol) and NHPI

(05mmol) were added to a glass reactor 44mmol H2O2

(30wt in water 45mL) was added with a syringe pumpby 02mLmin speed in 30min The reaction mixture wasvigorously stirred (about 750 rpm) Reaction mixtures wereanalyzed using GC and GC-MS

Hindawi Publishing CorporationJournal of CatalystsVolume 2014 Article ID 823054 6 pageshttpdxdoiorg1011552014823054

2 Journal of Catalysts

Table 1 Effect of additives for the oxidation of benzyl alcohol to benzaldehyde at 70∘Ca

Entry Catalyst Amountb (mol) Conv () Selc ()1 FeSO4NaBF4

251 666 945 (89 11)2 2510 710 943 (88 12)3

FeSO4NaH2PO4

251 747 960 (87 13)4 255 20 965 (87 13)5 2510 16 933 (93 7)6

FeSO4KH2PO4

251 641 959 (90 10)7 2525 44 951 (92 8)8 255 19 892 (88 12)9 FeSO4KHPd 251 513 947 (82 18)10 2525 328 867 (92 8)a20mmol of benzyl alcohol (216 g) 22 equiv of H2O2 (44mmol 45mL 30 wt in water) reaction time 05 h H2O2 was added with a syringe pump by02mLmin speed bAmount of catalyst cTotal selectivity to benzaldehyde and benzoic acid Value in parentheses means the ratio of benzaldehydebenzoicacid dKHP potassium hydrogen phthalate


Entry Catalyst Amountb (mol) Time (h) Conv () Selc ()1

FeSO4NaH2PO4 25105 38 959 (91 9)

2 2 86 951 (90 10)3 4 95 912 (90 10)4 FeSO4NaH2PO4 2525 05 11 982 (92 8)5 2 19 982 (93 7)6 FeSO4NaH2PO4 2510 05 11 988 (92 8)7 19 13 989 (91 9)8 FeSO4KBr 2510 05 34 100 (89 11)9 FeSO4NaBF4 2510 05 17 gt999 (100 0)10 FeSO4KH2PO4 2525 05 12 983 (93 7)11 FeSO4N1111Gly 2525 05 206 917 (96 4)12 FeSO4N2111OAc 2525 05 257 984 (87 13)13 FeSO4[HMIM][HSO4] 2510 05 13 gt999 (100 0)a20mmol of benzyl alcohol 22 equiv of H2O2 (30 wt in water) H2O2 was added with a syringe pump by 02mLmin speed bAmount of catalyst cTotalselectivity to benzaldehyde and benzoic acid Value in parentheses means the ratio of benzaldehydebenzoic acid

Different reaction conditions (temperature concentra-tion Fe salt and speed of adding H

2O2) have been opti-

mized Limited by the length these results were listed inthe Supplementary data (Figures S1 and S2 and TablesS1-S2) (see Supplementary Material available online athttpdxdoiorg1011552014823054)

3 Results and Discussion

31 The Influence of Different Additives It has been revealedthat some additives (such as KH

2PO4and KHSO

4) to Fenton

system can lead to a more effective oxidizing process at70∘C [13] The role of KH

2PO4was to control the pH of

the solution which can change the rate to generate hydroxylradicals As a result the selectivity of the reaction wasenhanced [13] Encouraged by this idea we have tried tofurther improve the reaction by adding different inorganicbuffers in Fenton system The influence of different additives(NaBF

4 NaH

2PO4 KH2PO4 and KHP) at 70∘C was studied

(Table 1)Our resultswithKH2PO4as additivewere very close

to those of a previous report [13] It seems that the adding ofNaBF

4 NaH

2PO4 or KHP cannot give better results

Performing reaction at room temperature is beneficial tosave energy and develop safe process The performance ofthese inorganic buffers was investigated at 25∘C Unfortu-nately the reactivity of these catalyst systems is quite poorat room temperature (Table 2 entries 1ndash10) Though goodselectivity can be obtained the conversion is quite lowIncreasing reaction time or changing the amount of additivecould not improve the results at all

Though ionic liquids have shown attractive role inimproving the reactivity of oxidation system [24ndash27] itseems that this compound cannot cooperate well withFenton system (Table 2 entries 11ndash13) The conversionwith [HMIM][HSO

4] (hexylmethylimidazole hydrosulfate)

as additive is only 13 at 25∘CAddingN1111

Gly (tetramethy-lammonium glycinate) or N

2111OAc (trimethylethylammo-

nium acetate) can accelerate the reaction but the selectivityis also not so good

32 NHPIFeSO4Oxidation Process How to improve the

selectivity of Fenton system and maintain its reactivity at thesame time are a challenge To solve this problem and findout an excellent additive the classical free radical mechanism

Journal of Catalysts 3

Table 3 Oxidation of benzyl alcohol with different catalyst systems at 25∘Ca

Entry Catalyst Amountb (mol) Conv () Selc ()1

FeSO4NHPI2525 367 991 (94 6)

2 25125 360 982 (92 8)3 2550 318 959 (90 10)4 FeSO4TEMPO 2525 205 989 (96 4)5 FeSO44-OH-TEMPO 2525 139 996 (99 1)6 Fe2(SO4)3NHPI 2525 321 952 (87 13)7 Fe(NO3)3NHPI 2525 599 942 (82 18)8 FeCl3NHPI 2525 433 876 (84 16)a20mmol of benzyl alcohol 22 equiv of H2O2 (30 wt in water) reaction time 05 h H2O2 was added with a syringe pump by 02mLmin speed bAmountof catalyst cTotal selectivity to benzaldehyde and benzoic acid Value in parentheses means the ratio of benzaldehydebenzoic acid

∙

∙

∙

∙

∙

∙

∙

OH

O

minusH2O

H2O2

O2

OOH

H+

OH

minusH2O

H2O2

PINONIPH

OHminus

OH

OH

OH

OH

OH

H+

Fe2+

OH

O

O

O

NndashO NndashOH

H2O

H2O

H2O2OOHFe3+

Oil

Water

O

H

Figure 1 Proposed mechanism for the oxidation of benzyl alcohol using NHPIFenton system

of Fenton system was carefully analyzed The whole radicalreaction process of Fenton system is shown as follows [28ndash30]

Fe2+ +H2O2997888rarr Fe3+ +OHminus +HO∙ (1)

Fe3+ +H2O2997888rarr Fe2+ +H+ +HOO∙ (2)

Fe2+ +HO∙ 997888rarr Fe3+ +OHminus (3)

H2O2+HO∙ 997888rarr H

2O +HOO∙ (4)

Fe2+ +HOO∙ 997888rarr Fe3+ +OOHminus (5)

Fe3+ +HOO∙ 997888rarr Fe2+ +H+ +O2

(6)Hydroxyl radical was generated in water phase by a series

of complex reactions then hydroxyl radical can abstract

a hydrogen atom from alcohols to form alkyl radicalsIf large numbers of hydroxyl radicals accumulate withoutcontrol this may cause deep and nonselective oxidation[31] Therefore we believed that there should be at leasttwo ways to improve reaction selectivity of Fenton systemOne is to control the generation rate of hydroxyl radicalsand the other is to reduce the accumulation of nonselectivehydroxyl radicals and convert them to radicals with higherselectivity such as phthalimide N-oxyl (PINO) which hasbeen widely used in oxidation reaction [32ndash35] Addinginorganic buffers can change the pH of reaction mixture andcontrol the generation rate of radicals This is the first waymentioned above and it has been widely investigated [13 18ndash23] Selectivity can be enhanced by this way but the catalyticactivity of this system is quite low at room temperature(Table 2)


Table 4 Oxidation of several alcoholsa

Entry Substrate Temp (∘C) Product Con () Sel ()

1 OH 25

O

H 367 936

2OH

25

O

H 43 gt999

3

OH

25

O

123 gt999

4

OH

55

O

505 gt999

5OH

55O

48 gt999

6OH

55O

H133 900

7OH

H3CO55

O

H

H3CO

493 975

8OH

H3C55

O

H

H3C

411 960

9OH

55O

548 825

aCatalyst FeSO4NHPI 20mmol of benzyl alcohol 22 equiv of H2O2 (30 wt in water) reaction time 05 h H2O2 was added with a syringe pump by02mLmin speed

So far there is no report about the secondway If amethodcan be developed to achieve the second way the selectivityshould be improved without losing catalytic activity Thereare two keys to successfully develop this method first theadditive should mainly exist in the organic phase which canavoid possible influence on the Fenton system induced by theadditive second the additive can react with hydroxyl radicalsto generate other radicals with high oxidation selectivityquickly (Figure 1) N-Hydroxyphthalimide (NHPI) is anexcellent choice under these two restrictions and PINOradical can be generated from NHPI which has been provento be catalyst with high oxidation selectivity [32ndash35] Thenthe effect of NHPI as additive was studied Indeed the resultis satisfying as expected Both the selectivity and conversion

are obviously improved by adding NHPI (Table 3 entries1sim3) TEMPO(2266-tetramethylpiperidinooxy) and 4-OH-TEMPO (4-hydroxy-TEMPO) also gave better conversionand selectivity comparing with those using inorganic buffersHowever the conversion with TEMPO or 4-OH-TEMPOis lower than that with NHPI The reactivities of differentiron salts were evaluated in the oxidation of benzyl alcohol(Table 3) Obviously FeSO

4sdot7H2O cooperating with NHPI

gives the highest selectivity in comparison with Fe2(SO4)3

Fe(NO3)3sdot9H2O and FeCl

3

33 Oxidation of Several Alcohols To investigate the univer-sality of NHPIFeSO

4H2O2system oxidations of different

alcohols were performed (Table 4) Most of these oxidations


gave good results Though the result of benzyl alcohol issatisfying at 25∘C the converting rates of 4-isopropyl benzylalcohol and 120572-phenylethyl alcohol are a little low at 25∘Cwhichmay be caused by the replacement of electron donatinggroups The conversion of 120572-phenylethyl alcohol achieved505 at 55∘C with excellent selectivity It should be notedthat ortho substituent and bulky groups may also reduce thereaction rate (Table 4 entries 5 and 6) 4-Methoxybenzylalcohol and 4-methylbenzyl alcohol were tested at 55∘Cbecause of the high melting points and the results were fairlysatisfactory (Table 4 entries 7sim8) However the selectivityof the 2-butanol oxidation is a little poor with this catalystsystem

4 Conclusion

To improve the selectivity of Fenton reagent (Fe2+H2O2) in

oxidation reaction the cooperation between Fenton reagentand a series of additives has been investigated It was foundthat the reactivity and selectivity of Fenton system wereimproved with NHPI as cocatalyst The oxidation of benzylalcohol catalyzed by this new Fe2+H

2O2NHPI system can

be well performed under room temperature without addingany organic solvent Besides this catalyst system is effectivefor the oxidation of different alcohols We hope the catalystsystems developed here provide a new way for a greeninnoxious and cheap candidate for the oxidation of alcoholsand similar compounds

Conflict of Interests

The authors declare that they have no conflict of interestsregarding the publication of this paper

Acknowledgment

This work was supported by the National Natural ScienceFoundation of China (no 21176110)

References

[1] H R Eisenhauer ldquoOxidation of phenolic wastesrdquo Journal(Water PollutionControl Federation) vol 36 no 9 pp 1116ndash11281964

[2] J H Ramirez F M Duarte F G Martins C A Costa and LMMadeira ldquoModelling of the synthetic dyeOrange II degrada-tion using Fentonrsquos reagent from batch to continuous reactoroperationrdquo Chemical Engineering Journal vol 148 no 2-3 pp394ndash404 2009

[3] J A Zazo J A Casas A F Mohedano M A Gilarranz and J JRodrıguez ldquoChemical pathway and kinetics of phenol oxidationby Fentonrsquos reagentrdquo Environmental Science and Technology vol39 no 23 pp 9295ndash9302 2005

[4] H Y Wang Y N Hu G P Cao and W K Yuan ldquoDegradationof propylene glycol wastewater by Fentonrsquos reagent in a semi-continuous reactorrdquo Chemical Engineering Journal vol 170 no1 pp 75ndash81 2011

[5] F Haber and JWeiss ldquoThe catalytic decomposition of hydrogenperoxide by iron saltsrdquo Proceedings of the Royal Society A vol147 pp 332ndash351 1934

[6] J Weiss ldquoInvestigations on the radical HO2in solutionrdquo

Transactions of the Faraday Society vol 31 pp 668ndash681 1995[7] A Santos P Yustos S Rodrıguez and A Romero ldquoMineraliza-

tion lumping kinetic model for abatement of organic pollutantsusing Fentonrsquos reagentrdquo Catalysis Today vol 151 no 1-2 pp 89ndash93 2010

[8] M S Lucas A A Dias A Sampaio C Amaral and JA Peres ldquoDegradation of a textile reactive Azo dye by acombined chemical-biological process fentonrsquos reagent-yeastrdquoWater Research vol 41 no 5 pp 1103ndash1109 2007

[9] D Mantzavinos and E Psillakis ldquoEnhancement of biodegrad-ability of industrial wastewaters by chemical oxidation pre-treatmentrdquo Journal of Chemical Technology and Biotechnologyvol 79 no 5 pp 431ndash454 2004

[10] F Gozzo ldquoRadical and nonmdashradical chemistry of the Fentonmdashlike systems in the presence of organic substratesrdquo Journal ofMolecular Catalysis A Chemical vol 171 no 1-2 pp 1ndash22 2001

[11] C Espro S Marini F Mendolia F Frusteri and A ParmalianaldquoEnhancing effect of S and F moieties on the performance ofFenton system in the selective oxidation of propanerdquo CatalysisToday vol 141 no 3-4 pp 306ndash310 2009

[12] W Wang M H Zhou Q Mao and X Wang ldquoNovel NaYzeolite-supported nanoscale zero-valent iron as an efficientheterogeneous Fenton catalystrdquo Catalysis Communications vol11 no 11 pp 937ndash941 2010

[13] F Shi M K Tse Z Li and M Beller ldquoControlling iron-catalyzed oxidation reactions from non-selective radical toselective non-radical reactionsrdquo Chemistry vol 14 no 29 pp8793ndash8797 2008

[14] M P Ormad R Mosteo C Ibarz and J L Ovelleiro ldquoMul-tivariate approach to the photo-Fenton process applied tothe degradation of winery wastewatersrdquo Applied Catalysis BEnvironmental vol 66 no 1-2 pp 58ndash63 2006

[15] J de Laat and T G Le ldquoEffects of chloride ions on theiron(III)-catalyzed decomposition of hydrogen peroxide andon the efficiency of the Fenton-like oxidation processrdquo AppliedCatalysis B Environmental vol 66 no 1-2 pp 137ndash146 2006

[16] C K Duesterberg W J Cooper and T D Waite ldquoFenton-mediated oxidation in the presence and absence of oxygenrdquoEnvironmental Science and Technology vol 39 no 13 pp 5052ndash5058 2005

[17] J J Pignatello E Oliveros and AMackay ldquoAdvanced oxidationprocesses for organic contaminant destruction based on thefenton reaction and related chemistryrdquo Critical Reviews inEnvironmental Science and Technology vol 36 no 1 pp 1ndash842006

[18] P Bautista A F Mohedano J A Casas J A Zazo and J JRodriguez ldquoAn overview of the application of Fenton oxidationto industrial wastewaters treatmentrdquo Journal of Chemical Tech-nology and Biotechnology vol 83 no 10 pp 1323ndash1338 2008

[19] W Manchot ldquoUeber Sauerstoffactivirungrdquo Liebigs Annalen DerChemie vol 314 no 1-2 pp 177ndash199 1901

[20] K V Padoley S N Mudliar S K Banerjee S C Deshmukhand R A Pandey ldquoFenton oxidation a pretreatment option forimproved biological treatment of pyridine and 3-cyanopyridineplant wastewaterrdquo Chemical Engineering Journal vol 166 no 1pp 1ndash9 2011


[21] H GWilliam L Yiishyan and JW Kang ldquoAdvanced oxidationprocesses A kinetic model for the oxidation of 12-dibromo-3-chloropropane in water by the combination of hydrogenperoxide andUV radiationrdquo IndustrialampEngineering ChemistryResearch vol 34 no 7 pp 2314ndash2323 1995

[22] M C Lu Y F Chang Y M Chen and Y Y Huang ldquoEffect ofchloride ions on the oxidation of aniline by Fentonrsquos reagentrdquoJournal of Environmental Management vol 75 no 2 pp 177ndash182 2005

[23] M-C Lu J-N Chen and C-P Chang ldquoEffect of inorganicions on the oxidation of dichlorvos insecticide with Fentonrsquosreagentrdquo Chemosphere vol 35 no 10 pp 2285ndash2293 1997

[24] X B Hu J Y Mao Y Sun H Chen and H R Li ldquoAcety-lacetone-Fe catalystmodified by imidazole ionic compound andits application in aerobic oxidation of 120573-isophoronerdquo CatalysisCommunications vol 10 no 14 pp 1908ndash1912 2009

[25] W H Guan C M Wang X Yun X B Hu Y Wang and HR Li ldquoA mild and efficient oxidation of 236-trimethylphenolto trimethyl-14-benzoquinone in ionic liquidsrdquo Catalysis Com-munications vol 9 no 10 pp 1979ndash1981 2008

[26] M Rong C Liu J Han and H Wang ldquoCatalytic oxidationof alcohols by a double functional ionic liquid [bmim]BF

4rdquo

Catalysis Communications vol 10 no 4 pp 362ndash364 2009[27] U K Sharma N Sharma R Kumar R Kumar and A K

Sinha ldquoBiocatalytic promiscuity of lipase in chemoselectiveoxidation of aryl alcoholsacetates a unique synergism of cal-b and [hmim]br for the metal-free H

2O2activationrdquo Organic

Letters vol 11 no 21 pp 4846ndash4848 2009[28] I Casero D Sicilia S Rubio and D Perez-Bendito ldquoChemical

degradation of aromatic amines by Fentonrsquos reagentrdquo WaterResearch vol 31 no 8 pp 1985ndash1995 1997

[29] M C Lu J N Chen and C P Chang ldquoOxidation of dichlorvoswith hydrogen peroxide using ferrous ion as catalystrdquo Journal ofHazardous Materials B vol 65 pp 277ndash288 1999

[30] J J Pignatello andDark a ldquond photoassisted iron(3+)-catalyzeddegradation of chlorophenoxy herbicides by hydrogen perox-iderdquoEnvironmental ScienceampTechnology vol 26 no 5 pp 944ndash951 1992

[31] D Bianchi R Bortolo R Tassinari M Ricci and R Vignola ldquoAnovel iron-based catalyst for the biphasic oxidation of benzeneto phenol with hydrogen peroxiderdquo Angewandte Chemie vol112 no 23 pp 4491ndash4493 2000

[32] Z Yao X Hu J Mao and H Li ldquoAn environmentally benigncatalytic oxidation of cholesteryl acetate withmolecular oxygenby using N-hydroxyphthalimiderdquo Green Chemistry vol 11 no12 pp 2013ndash2017 2009

[33] T Hara T Iwahama S Sakaguchi and Y Ishii ldquoCatalyticoxyalkylation of alkenes with alkanes and molecular oxygenvia a radical process using N-hydroxyphthalimiderdquo Journal ofOrganic Chemistry vol 66 no 19 pp 6425ndash6431 2001

[34] Y Aoki S Sakaguchi and Y Ishii ldquosynthesis of naphthalenedi-ols by aerobic oxidation of diisopropylnaphthalenes catalyzedby N-hydroxyphthalimide (NHPI)120572 120572

1015840

-azobisisobutyronitrile(AIBN)rdquo Advanced Synthesis amp Catalysis vol 346 no 2-3 pp199ndash202 2004

[35] Y Ishii S Sakaguchi and T Iwahama ldquoInnovation of hydro-carbon oxidation with molecular oxygen and related reactionsrdquoAdvanced Synthesis and Catalysis vol 343 no 5 pp 393ndash4272001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

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International Journal of


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Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of



Entry Catalyst Amountb (mol) Conv () Selc ()1 FeSO4NaBF4

251 666 945 (89 11)2 2510 710 943 (88 12)3

FeSO4NaH2PO4

251 747 960 (87 13)4 255 20 965 (87 13)5 2510 16 933 (93 7)6

FeSO4KH2PO4

251 641 959 (90 10)7 2525 44 951 (92 8)8 255 19 892 (88 12)9 FeSO4KHPd 251 513 947 (82 18)10 2525 328 867 (92 8)a20mmol of benzyl alcohol (216 g) 22 equiv of H2O2 (44mmol 45mL 30 wt in water) reaction time 05 h H2O2 was added with a syringe pump by02mLmin speed bAmount of catalyst cTotal selectivity to benzaldehyde and benzoic acid Value in parentheses means the ratio of benzaldehydebenzoicacid dKHP potassium hydrogen phthalate


Entry Catalyst Amountb (mol) Time (h) Conv () Selc ()1

FeSO4NaH2PO4 25105 38 959 (91 9)

2 2 86 951 (90 10)3 4 95 912 (90 10)4 FeSO4NaH2PO4 2525 05 11 982 (92 8)5 2 19 982 (93 7)6 FeSO4NaH2PO4 2510 05 11 988 (92 8)7 19 13 989 (91 9)8 FeSO4KBr 2510 05 34 100 (89 11)9 FeSO4NaBF4 2510 05 17 gt999 (100 0)10 FeSO4KH2PO4 2525 05 12 983 (93 7)11 FeSO4N1111Gly 2525 05 206 917 (96 4)12 FeSO4N2111OAc 2525 05 257 984 (87 13)13 FeSO4[HMIM][HSO4] 2510 05 13 gt999 (100 0)a20mmol of benzyl alcohol 22 equiv of H2O2 (30 wt in water) H2O2 was added with a syringe pump by 02mLmin speed bAmount of catalyst cTotalselectivity to benzaldehyde and benzoic acid Value in parentheses means the ratio of benzaldehydebenzoic acid

Different reaction conditions (temperature concentra-tion Fe salt and speed of adding H

2O2) have been opti-

mized Limited by the length these results were listed inthe Supplementary data (Figures S1 and S2 and TablesS1-S2) (see Supplementary Material available online athttpdxdoiorg1011552014823054)

3 Results and Discussion

31 The Influence of Different Additives It has been revealedthat some additives (such as KH

2PO4and KHSO

4) to Fenton

system can lead to a more effective oxidizing process at70∘C [13] The role of KH

2PO4was to control the pH of

the solution which can change the rate to generate hydroxylradicals As a result the selectivity of the reaction wasenhanced [13] Encouraged by this idea we have tried tofurther improve the reaction by adding different inorganicbuffers in Fenton system The influence of different additives(NaBF

4 NaH

2PO4 KH2PO4 and KHP) at 70∘C was studied

(Table 1)Our resultswithKH2PO4as additivewere very close

to those of a previous report [13] It seems that the adding ofNaBF

4 NaH

2PO4 or KHP cannot give better results

Performing reaction at room temperature is beneficial tosave energy and develop safe process The performance ofthese inorganic buffers was investigated at 25∘C Unfortu-nately the reactivity of these catalyst systems is quite poorat room temperature (Table 2 entries 1ndash10) Though goodselectivity can be obtained the conversion is quite lowIncreasing reaction time or changing the amount of additivecould not improve the results at all

Though ionic liquids have shown attractive role inimproving the reactivity of oxidation system [24ndash27] itseems that this compound cannot cooperate well withFenton system (Table 2 entries 11ndash13) The conversionwith [HMIM][HSO

4] (hexylmethylimidazole hydrosulfate)

as additive is only 13 at 25∘CAddingN1111

Gly (tetramethy-lammonium glycinate) or N

2111OAc (trimethylethylammo-

nium acetate) can accelerate the reaction but the selectivityis also not so good

32 NHPIFeSO4Oxidation Process How to improve the

selectivity of Fenton system and maintain its reactivity at thesame time are a challenge To solve this problem and findout an excellent additive the classical free radical mechanism




FeSO4NHPI2525 367 991 (94 6)


∙

∙

∙

∙

∙

∙

∙

OH

O

minusH2O

H2O2

O2

OOH

H+

OH

minusH2O

H2O2

PINONIPH

OHminus

OH

OH

OH

OH

OH

H+

Fe2+

OH

O

O

O

NndashO NndashOH

H2O

H2O

H2O2OOHFe3+

Oil

Water

O

H




Fe3+ +H2O2997888rarr Fe2+ +H+ +HOO∙ (2)



2O +HOO∙ (4)


Fe3+ +HOO∙ 997888rarr Fe2+ +H+ +O2







1 OH 25

O

H 367 936

2OH

25

O

H 43 gt999

3

OH

25

O

123 gt999

4

OH

55

O

505 gt999

5OH

55O

48 gt999

6OH

55O

H133 900

7OH

H3CO55

O

H

H3CO

493 975

8OH

H3C55

O

H

H3C

411 960

9OH

55O

548 825







3






4 Conclusion



2O2NHPI system can




Acknowledgment


References





























4rdquo












1015840












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




FeSO4NHPI2525 367 991 (94 6)


∙

∙

∙

∙

∙

∙

∙

OH

O

minusH2O

H2O2

O2

OOH

H+

OH

minusH2O

H2O2

PINONIPH

OHminus

OH

OH

OH

OH

OH

H+

Fe2+

OH

O

O

O

NndashO NndashOH

H2O

H2O

H2O2OOHFe3+

Oil

Water

O

H




Fe3+ +H2O2997888rarr Fe2+ +H+ +HOO∙ (2)



2O +HOO∙ (4)


Fe3+ +HOO∙ 997888rarr Fe2+ +H+ +O2







1 OH 25

O

H 367 936

2OH

25

O

H 43 gt999

3

OH

25

O

123 gt999

4

OH

55

O

505 gt999

5OH

55O

48 gt999

6OH

55O

H133 900

7OH

H3CO55

O

H

H3CO

493 975

8OH

H3C55

O

H

H3C

411 960

9OH

55O

548 825







3






4 Conclusion



2O2NHPI system can




Acknowledgment


References





























4rdquo












1015840












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




1 OH 25

O

H 367 936

2OH

25

O

H 43 gt999

3

OH

25

O

123 gt999

4

OH

55

O

505 gt999

5OH

55O

48 gt999

6OH

55O

H133 900

7OH

H3CO55

O

H

H3CO

493 975

8OH

H3C55

O

H

H3C

411 960

9OH

55O

548 825







3






4 Conclusion



2O2NHPI system can




Acknowledgment


References





























4rdquo












1015840












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of



4 Conclusion



2O2NHPI system can




Acknowledgment


References





























4rdquo












1015840












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of








4rdquo












1015840












Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Research Article Improvement the Activity and Selectivity ...downloads.hindawi.com/archive/2014/823054.pdfResearch Article Improvement the Activity and Selectivity of Fenton System