Vapor-phase synthesis of piperidine over SiO2 catalysts

Article abstract of DOI:10.1016/j.catcom.2018.03.010

Vapor phase dehydration of 5-amino-1-pentanol to produce piperidine was investigated over various oxide catalysts such as ZrO₂, TiO₂, Al₂O₃ and SiO₂. Among the tested catalysts, SiO₂ selectively produced piperidine at 300 °C. A high 5-amino-1-pentanol conversion of 99.9% with a piperidine selectivity of 94.8% was achieved over weak acidic SiO₂. In an experiment using isotope such as deuterated water, surface hydroxy groups of SiO₂ are concluded to be the active centers.

Full text of DOI:10.1016/j.catcom.2018.03.010

Accepted Manuscript
Vapor-phase synthesis of piperidine over SiO2 catalysts
Takuma Tsuchiya, Yoshihiro Kajitani, Kaishu Ohta, Yasuhiro
Yamada, Satoshi Sato
PII:
S1566-7367(18)30102-X
doi:10.1016/j.catcom.2018.03.010
CATCOM 5351
DOI:
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
10 January 2018
19 February 2018
7 March 2018
Please cite this article as: Takuma Tsuchiya, Yoshihiro Kajitani, Kaishu Ohta, Yasuhiro
Yamada, Satoshi Sato , Vapor-phase synthesis of piperidine over SiO2 catalysts. The
address for the corresponding author was captured as affiliation for all authors. Please
check if appropriate. Catcom(2018), doi:10.1016/j.catcom.2018.03.010
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ACCEPTED MANUSCRIPT
A manuscript for theoriginalpapersubmittedtothejournalofCatalysisCommunications
Vapor-phasesynthesisofpiperidineoverSiO catalysts
2
Takuma Tsuchiya, Yoshihiro Kajitani,KaishuOhta,YasuhiroYamada,SatoshiSato*
GraduateSchoolof Engineering,ChibaUniversity,Chiba,263-8522,Japan
*
Correspondingauthor.Tel. +81432903376; Fax:+81432903401
E-mail address: satoshi@faculty.chiba-u.jp(S. Sato)

ACCEPTED MANUSCRIPT
Abstract
Vapor phase dehydration of5-amino-1-pentanol to produce piper id ine was investigated over various oxide
catalysts such as ZrO2, TiO2, Al2O3 and S iO 2. Among the tested catalysts, S iO 2 se le ctively produced
o
piperidine at 300 C. A high 5-amino-1-pentanolconversionof99.9% witha p ip eridine se le ctivity of94.8%
was achieved over weak ac id ic S iO 2. In an experiment using is otope such as deuterated water, surface
hydroxygroupsofSiO2areconcluded tobe theactive centers.
Keywords:Dehydration; 5-amino-1-pentanol; piperidine;SiO2.

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1
. Introduction
Amino compounds are important chemicals in various industrial products for pharmaceut ic a ls and
agrochemica ls [1]. Amongamino compounds, espec ia lly cyclic amines are useful substances in the field of
med ic ines [2, 3] and pesticides [4], and they are w id ely used for hardening agent of rubbers, lubricating oil,
and flavoring agent [5, 6]. In a liquid phase, cyclic amines can be produced from amino alcohols using
catalysts suchas sulfuric acid [7] and Ru comp le xes [8, 9]. Rani et al. have reported that cyclic amines are
produced bydehydrationofdiols usingNH3 gas [10]. For the synthesis ofpiperidine, which is one ofcyclic
amines, using 5-amino-1-pentanol as a raw mater ia l (Scheme 1), a catalytic reaction using Rucomplex has
beenreported [11]. Because ofthe homogenous reaction ina liquid phase, it isdisadvantage that theycannot
be continuously recovered from the reaction mixture. In contrast, vapor-phase react io ns using Cu/Al2O3
[
5,12] and CuCrLa/Al2O3 [13] catalysts have beenreported as a se le ctive process. Zeolite catalysts have a ls o
been reported on this reaction, though witha low piperidine selectivity of72% and using a diluting solvent
14]. In our previous work, we have reported the dehydrat io n of 5-amino-1-pentanol to 4-penten-1-amine
Scheme 1). In the reaction over Yb2O3, 4-penten-1-amine was selectively synthesized with a convers io n
[
(
o
5
8.4% andaselectivity90.0% at 425 C[15].
Scheme 1 Dehydration of 5-amino-1-pentanol to piperidine and 4-penten-1-amine.
Silica is usually used as a support in many reactions because of its high specific surface area and its
inert character is tics. However, there are a few cases where pure S iO 2 shows aneffective catalytic activity for
dehydrat io nofchemicals. We have prev io usly reported novel catalyt ic synthesis ofangelica la ctones via the
lactonizationof levulinic ac id over silica. In the lactonization, S iO 2 was highly se le ctive for the formationof
o
angelica lactones from levulinic ac id at 275 C [16] because the side reactions were proh ib ited by the inert
characters of silica. It is a ls o known that silica effectively works for the dehydration of acetaldoxime to
o
acetonitrile at 270 C[17].
In th is study, we report the vapor-phase dehydrat io n of 5-amino-1-pentanol to piperidine over

ACCEPTED MANUSCRIPT
var io us oxide catalysts under continuous f lo w conditions (Scheme 1). We found that S iO 2 was a selective
catalyst forthesynthesis ofpiperidine without usingany dilutingsolvent. The active species for the format io n
of p ip eridine from 5-amino-1-pentanol were also discussed in an isotope experiment and a probab le
formationroutefortheformationofpiperidine oversilica was proposed.
2
. Experimental
2
.1 Samplesforthecatalyticreaction
5-Amino-1-pentanol was purchased from Sigma-A ld r ic h Co., Ltd., and was used for the catalyt ic
reactionwithout furtherpurification.Piperidineanddeuterated water, D2O, were purchased fromWakoPure
Chemical Industries Ltd. Four different silicas (CARIACT Q-3, Q-6, Q-10 and Q-15 with mean pore
diameters of3, 6, 10 and 15 nm, respectively) were supplied byFujiSilycia Chemical Ltd. TiO2(JRC-TIO-
4
) and Al2O3 (JRC-ALO-6) were supplied as Japan Reference Catalysts by Catalyst Society of Japan. A
yttr ia -stabilized ZrO2 (YSZ)wassuppliedbyDaiichiKigensoKagakuKogyoCo., Ltd.,Japan. H-Y (Si/Al=
.3) zeolite was supplied byN ik ki Chemical Co., Ltd., Japan. Zeolite (Beta-35, S i/ Al = 36.9) was supplied
byClariantInternationalLtd.
.2 Catalyticreaction
The vapor-phase dehydration of 5-amino-1-pentanol was carried out in a fixed-bed down flow
6
2
reactor withan inner diameter of 17 mm under the atmospher ic pressure of either H2 or N2 gas. Pr io r to the
reaction, 0.5-5.0 gofacatalystwasplaced inthe catalystbedand heatedataprescribed temperature for 1 hto
stabilize the temperature of the catalyst bed. After the preheating, pure 5-amino-1-pentanol was fed through
-1
thetopofreactor usingsyringe pump at a liquid feedrateof1.77 g h together withaneither H2 orN2 flow of
3
-1
o
2
0 cm min . Because the melting point of5-amino-1-pentanol is ca. 37 C, the syringe was heated at ca. 50
o
o
C bya 250-W light bulb. The liqu id effluent collected at 0 C every hour was analyzed bya FID-GC (GC-
1
4A, Shimadzu, Japan) witha capillarycolumn ofInert Cap 1 (0.25 mm I.D. and 60 m le ngth, GL-Sc ie nce,
Japan). A GC-MS (QP5050A, Shimadzu) was used for the identificat io n of products in the effluent. The
majorproducts inthe dehydrationwerep ip eridine and4-penten-1-amine. Thecatalyticactivitywasevaluated
byaveraging the convers io nand selectivitydata in the initial5 h. Boththe conversionof5-amino-1-pentanol
and the selectivityto eachproduct weredefinedasmolarpercentage.

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An addit io nal pretreatment of silica with isotope such as D2O was carried out. Prior to the
o
pretreatment ofD2O, 5.0 gofa silica placed in the catalyst bed was heated at 300 C for 1 h. D2O was fed at
o
-1
o
3
00 C and a liquid feed rate of1.77 g h for 2 h, and then the silica sample was heated at 300 C for 1 h to
remove the residual D2O. After that, we performed the catalytic reaction of 5-amino-1-pentanol under the
same conditions as a usual experiment using 5-amino-1-pentano l. Mass-spectrometer in the GC-MS
equipment wasusedforanalysisofpiperidine recovered duringanappropriateperiodofthereaction.
3
. Results andDiscussion
3
.1.Dehydrationof 5-amino-1-pentanoltopiperidine overseveralacidcatalysts
As theeffectivityofacidcatalyst indehydrocyclizat io nofdiols hasbeenreported [18, 19], we tested
several ac id catalysts in the present study (Table 1). In the react io n over the acid catalysts, piperidine was
produced with a relative high selectivity irrespective of the conversion of 5-amino-1-pentanol. In our
prev io usstudy, we have studiedac id strengthofthe solid catalysts suchas T iO 2, Al2O3,zeoliteandS iO 2 [16,
17, 20, 21]. It has been found that S iO 2 has weak acid sites and zeolite and Al2O3 have strongacid sites. 4-
Penten-1-amine, which is the unsaturated amine product in the dehydrat io n of 5-amino-1-pentanol, was
detected as aby-product witha selectivity of4.2% inthereactionover Al2O3. Reddyet al. have reported the
dehydrat io n of 5-amino-1-pentanolover zeolite [14]. When zeolites are used as a catalyst, the dehydrat io n
proceeds at a high conversion, but a la rge number of by-products were produced, which reduced the
selectivityofpiper id ine. Althoughthe conversionover strongacidic zeolites was higher thanother catalysts,
the selectivity to p ip er id ine was lo wer thanthat of other catalysts. Tetragonal ZrO2 (YSZ) with both acid ic
and basic sites gave lo w convers io n. ZrO2 (YSZ) showed a low selectivityto piperidinebecause itproduced
several by-products such as δ-valerolactam and dimers with molecular weight higher than 125, where the
molecular weight ofp ip eridine is85. Amongthe tested catalysts, S iO 2 with low acid ic sites gave the highest
piperidine se le ctivity whereas the convers io n of 5-amino-1-pentanol was lo wer than other catalysts. Then,
we examined the conversionof5-amino-1-pentanolbyusing severalsilicas inthefollowingsection.
3
.2. Dehydrationof 5-amino-1-pentanoltopiperidine overSiO2 underdifferent conditions.

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Table 2 shows the dehydrationof5-amino-1-pentanol over S iO 2 (Q-6) and S iO 2 (Q-10) catalysts at
different reaction temperatures. As the react io n temperature was raised, the convers io n of 5-amino-1-
o
pentanol increased. At 350 C, S iO 2 (Q-6) showed the highest conversion82.1%. The piper id ine selectivity
o
was higher than 95% at 325 C. By-products such as dimers and trimers increased with increase in the
o
reactiontemperature. At a low temperature of300 C,S iO 2 (Q-10) showed the highest p ip eridine selectivity.
However, the selectivity ofpiperidine was significantly decreased withrise in the reactiontemperature, and
the yieldofpiperidine was as lowas 75%. Therefore, weattempted to improve the conversionby increasing
o
contact time at300 C.
The effect of contact time (W/F) in the dehydrat io n of5-amino-1-pentanol to piperidine over S iO 2
o
(
Q-6)at300 C,whereW andFare thecatalyst weightandthe feedrateof5-amino-1-pentanol,respectively,
as shown in Fig. S1. The conversionof5-amino-1-pentanol gradually increased at lo nger contact time. The
average convers io n of 5-amino-1-pentanol in the initial 5 h was 10.3% at a W/F of 0.28 h, while it was
73.1% at 1.1 h, 91.2% at 2.0 h and 99.9% at 2.8 h. The se le ctivity of piperidine slightly decreased from
98.8% at 0.28 h to 94.9% at 2.8 h. Although the high convers io n was attained in the initial per io d, it
decreased slightly with time on stream (Fig. S2). The major cause of the deactivat io n could be due to the
coke format io n.It isconfirmed byTG analysisofthe samp le s used forthereaction:weight lossofca. 15and
7
% were observed in the TG curves of zeol it e (Be ta -35, F ig . S3) and S iO
2
(Q-6, F ig . S4), respectively. Thus, the
catalystdeactivationwouldbe inevitable.
In order to confirm which pore size of silica is suitable for this reaction, we investigated the
dehydrat io nof5-amino-1-pentanol over different silica samples at a W/F of2.8 h. Table 3 shows the effect
ofpore size ofsilica inthedehydrat io n. Byemployingtheoptimized W/F, the other S iO 2 catalysts (Q-3and
Q-10) a ls o showed a convers io n of over 99%. In case of Q-15, which has the lo west surface area, the
conversion was lo wer, 86.3%. The selectivity was in all cases around 94% with only small differences
between the different S iO 2 catalysts. Judging from the highest se le ctivity of 94.9%, Q-6 has the most
appropriatepore size.
In p io neering papers, Cu/Al2O3 [5,12] and CuCrLa/Al2O3 [13] catalysts have been reported as
o
effectivecatalysts. High yieldofpiperidineover99% was obtainedatca.200 C,whereas the react io ns have

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been operated under the conditions using a solvent as a diluent [12,13] at high pressure of hydrogen [13].
Thesereports, however, have nodiscussiononthe rolesofCuand alumina for thedehydrat io n.Inthis study,
we performedthecatalytic reactionof5-amino-1-pentanolwithout usingsolvent.
Generally, ac id catalysts are efficient for the dehydrat io n of alcohols. We have examined the
dehydrat io n of 1,5-pentanediol to tetrahydropyran over ac id catalyst such as S iO 2-Al2O3, Al2O3 and T iO 2
[19]. We have previously reported the catalytic dehydrationof 1,4-butanediol to tetrahydrofuranover acid
catalysts [22]. The se le ctivity to tetrahydrofuran was 97.4% at 100% conversion of 1,4-butaned io l over
o
Al2O3 at 325 C while the conversion was only 1.6% over S iO 2. Tab le S1 shows the convers io n of 1,5-
pentanedioltotetrahydropyran. Inthe reactionover Al2O3, a1,5-pentanediolconversionwas reportedat350
o
o
C [19]. We also tested the reactionover Al2O3 at 300 C:a high tetrahydropyran se le ctivity of 95.3% was
obtained at the convers io nof100%. On the other hand, even whenthe experiment over S iO 2 (Q-6) catalyst
was carried out with catalyst weight of approximately 17 times more, the conversionwas 0.4% evenat 350
o
C. It is reasonable that 1,5-pentanediol shows a lo w reactivity over the weak ac id catalyst such as S iO 2,
while it shows highreactivity over a strongac id catalyst suchas Al2O3, wh ic habstractsOH group from1,5-
pentanediol. Incontrast, 5-amino-1-pentanol havinga basic amino group shows a highconvers io nof99.9%
o
over S iO 2 evenat 300 C. Basic 5-amino-1-pentanol cou ld act as a poisonof strongac id ic sites of Al2O3.
This would be the reasonwhy the Al2O3 has lo w activity (Tab le 1). Judging from the results, it is supposed
that hydroxyl groups of 1,5-pentanediol hardly adsorbs to the weak acid catalyst, whereas a basic reactant
suchas 5-amino-1-pentanolreadilyadsorbsontheweakacid SiO2andthenthereactioncanproceed.
3
.3. Dehydrationof 5-amino-1-pentanoloverdeuteratedSiO2.
Silanol groups ofsilica are knownto be involved inseveral catalyt ic react io ns [16, 23]. To confirm
the contributionof the silanol group in the dehydrationof 5-amino-1-pentanol, the react io n was carr ie d out
o
byexchanging the hydrogenof the silanol groups with deuterium, bycontacting D2O w it h silica at 300 C.
Figure S5shows the MS profilesofpiperidineproduced from5-amino-1-pentanolover thedeuteratedsilica.
The m/z peak of main product piperidine can be confirmed at 85, wh ic h is the molecular weight. The m/z
peak of 84 is a fragment io n in which one hydrogen atom of piperidine is eliminated. The peaks of86-87

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shows piper id ine containing isotope e le ments withdifferent neutron numbers. Thus, by replacing hydrogen
in piper id ine molecule with D, the peak intensities of85-87 increase. The re la tive intensityof the m/zpeaks
aresummarized inTab le S2. Fig. 1depicts the change inthe relative intensit ie sof the m/zpeak at 86 against
the intensityof84 withtimeonstream. At the first recoveryofthereact io neffluent for 20 min, the m/zpeak
of86 showed a higher value than that of the normalexperiment usingSiO2 w it hout deuterium. This revea ls
that the hydrogenofthe silanol group is introduced into theproductduringcatalyticreaction. Inthe recovery
of the second 20 min, the m/zpeaks intensities of86 as well as 87 decreased as compared withthose ofthe
first20 min, while anincrease inthepeak intensitybyintroduct io nofD into the productcouldbeconfirmed.
At the third 20 min, the m/z peak intensit ie s of 86 and 87 closed to the same level as those of the normal
reactionusinga silica withouttreatment withD2O.
Inordertoconfirm whether hydrogenin theproduced p ip er id ine isdirectlysubstitutedbydeuterium
or not, we conducted a reference experiment using p ip er id ine as a reactant. Fig. 1 also shows the reference
results. It was confirmed that the m/z peak of 86 increased slightly at the first recovery time of 20 min.
Compared to thepeak intensityat86 in the first and the second20 minofthereactionof5-amino-1-pentanol,
thepeak intensityat86 was small inthe reactantpiperidine. This ind ic atesthat the exchangeofH/D between
piperidine and the surface OD group is slower than the dehydration of5-amino-1-pentanol. Therefore, the
deuterationof piperidine was found to be mainly performed during the dehydrationprocess of 5-amino-1-
pentanol. TheMSprofiles andtherelative intensityofthepeaksarepresentedinFig.S6andTable S3.
We have cons id ered the se le ctivity to unsaturated a lc ohols strongly depends on the adsorption
structure of dio ls on catalyst surface [24, 25]. The adsorpt io n model of 1,4-butaned io l on Er2O3 was also
successfully simulated withdensity funct io naltheory(DFT) andpaired interactingorbita ls (PIO)ca lc ulat io n
as acid-base concerted tridentate coordination [26]. In a similar manner, the reaction mechanism on the
dehydrat io n of 1,5-pentanediol has been d is cussed [27]. In the dehydration of 5-amino-1-pentanol to 4-
penten-1-amine, theacid-base coordinationreactionmechanismis also presumed [15].
In Fig. 2, we proposed a possible acid-base concerted reaction scheme of 5-amino-1-pentanol to
produce piperidine over silica. Judging from the results of experiment using deuterated S iO 2, we propose a
mechanism where hydrogenofsurface silanol is introduced into the product during the reaction. The silanol

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groups of silica could be the active sites as ac id and base centers for an acid-base concerted mechanism.
Firstly, the hydroxyl group of 5-amino-1-pentanol is adsorbed to oxygen of a silanol group and proton of
another silanol group is adsorbed to nitrogen of amino group of 5-amino-1-pentanol. Subsequently, the
oxygen of the hydroxyl group of 5-amino-1-pentanol abstracts a proton form the amino group. The amine
can now attack the methylene next to the protonated hydroxylic moiety closing the ring. The remaining
protononthe amine group canbe abstractedbythe catalyst. According to the resultsof isotopeexperiments,
whenoxygenofthe hydroxyl group of5-amino-1-pentanolattacks a nearbyhydrogenatom, Dof thesilanol
group and hydrogen of the amino group can be exchanged with a certain probability. This hydrogen
exchange possibly occurs during the reaction, but the exchange rate is slower than that of the
dehydrocyclizationof 5-amino-1-pentanol (Fig. 1). This is because it could adsorb strongly on the catalyst
due to the bifunct io nal groups. Thus, it is cons id ered that the dehydration proceeds due to the silanol groups
functioningas Broenstedacid andLewis base,asshowninFig. 2.
4
. Conclusions
Vapor-phase dehydrat io n of 5-amino-1-pentanol to piperidine was stud ie d over various solid
catalysts. The continuous flow reaction has an advantage for the easiness of the separat io n of catalyst. The
formationofpiperidine from5-amino-1-pentanolwasefficientlyenhanced bysilica catalysts. The format io n
ofpiper id ine did not require strongacids suchas zeolite and Al2O3. Weak ac id s ofsilica were sufficient for
the react io n, and the secondary reaction such as dimerizat io n hardly proceeded over silica. The react io n
temperature was lowered to300°C whichresulted inonlya slight decrease ofselectivitytowards p ip er id ine,
but greatly enhanced the conversionof5-amino-1-pentanol to over 99.9%. At a contact time of 2.8ha high
piperidineselectivityof94.8%wasachieved.Inexperiments employingdeuteratedS iO 2, it was revealed that
silanol groups are involved in the react io n process, which most likely proceeds via a concerted ac id -base
mechanism.

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8
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[
7

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a
Table 1 Dehydrationof5-amino-1-pentanoltopiperidineoverseveralcatalysts.
b
b
Selectivity (mol%)
Conversion
mol%)
Catalyst
c
c
(
PD
4P1A
Others
ZrO
2
(YSZ)
(ALO-6)
(TIO-4)
1.7
12.8
37.9
75.4
96.3
14.5
10.3
7.9
65.6
0
4.2
0
34.4
17.3
12.8
8.1
Al
2
O
3
2
78.5
87.2
90.8
84.7
89.3
98.8
99.2
TiO
Zeolite (HY)
1.1
0
Zeolite (Beta-35)
15.3
10.7
1.2
SiO
SiO
2
(Q-3)
(Q-6)
0
2
0
SiO
2
(Q-10)
0
0.8
a
o
3
-1
Reactionconditions:reactiontemperature,300 C; N2gasflow rate,20cm min ; W/F,0.28 h, whereW
and F arethecatalyst weight andthefeedrateof5-amino-1-pentanol, respectively.
b
c
Averagedactivityinitial5 h. PD,piperidine;4P1A, 4-penten-1-amine.

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a
Table 2 Dehydrationof5-amino-1-pentanoltopiperidineoverSiO2 at different reactiontemperatures.
b
Reaction
b
Selectivity (mol%)
Conversion
(mol%)
Catalyst
Temperature
c
c
o
PD
4P1A
Others
(
C)
SiO
2
(Q-6)
300
10.3
32.2
82.1
7.9
98.7
96.7
91.1
99.2
99.1
90.2
0
0
0
0
0
0
c
1.3
3.3
8.9
0.8
0.9
9.8
325
350
SiO
2
(Q-10)
300
325
23.8
62.1
b
350
a
3
-1
N2 gas flow rate, 20 cm min ; W/F, 0.28 h. Averaged activity initial 5 h. PD, piperidine; 4P1A, 4-
penten-1-amine.

ACCEPTED MANUSCRIPT
o
a
Table 3 Effect ofporesize inthe dehydrationof5-amino-1-pentanoloversilicaat300 C.
b
b
Catalyst
Selectivity (mol%)
SA
m g )
Conversion
(mol%)
2
-1
c
(
PD
Others
6.7
SiO
SiO
2
2
(Q-3)
(Q-6)
7
05
99.8
99.9
99.9
86.3
o
93.3
94.8
93.3
94.7
451
259
5.2
SiO
SiO
2
(Q-10)
(Q-15)
6.7
2
226
5.3
a
3
-1
Reactionconditions:reactiontemperature,300 C; N2gasflow rate,20cm min ; W/F,2.8h.
b
Averagedactivityinitial5 h.
c
PD, piperidine.

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0
0
.2
.1
(
(
a)
b)
(
(
c)
d)
0
20
40
60
Time on stream / min
Fig.1Changes in the relative intensityof m/zpeak at 86 to84 in thedehydrationof5-amino-1-pentanolover
o
SiO2 (Q-6) at300 CandaW/F=2.8 h.
(a), dehydrationof5-amino-1-pentanoloverdeuteratedS iO 2; (b), reactionofp ip eridine over deuteratedS iO 2;
(c), dehydrationof5-amino-1-pentanolovernormalsilica withoutdeuteration; (d), referencepiperidine.

ACCEPTED MANUSCRIPT
Adsorption
Dissociation
Desorption
Regeneration
-
O-D : acidic site,
-OD : basic site
Fig. 2 Proposed reaction mechanism of the dehydration of 5-amino-1-pentanol to produce p ip er id ine over
SiO2.
Graphicalabstract
o
3
00 C/SiO2
Conversion: 99.9%
Selectivity: 94.8%

ACCEPTED MANUSCRIPT
Highlights




Vapor phasedehydrationof5-amino-1-pentanolwasinvestigatedover variousoxidecatalysts.
o
SiO
2
selectivelyproducedpiperidine inthedehydrationof5-amino-1-pentanolat300 C.
Ahigh5-amino-1-pentanolconversionof99.9%withapiperidineselectivityof94.8%wasachieved.
In anexperimentusingdeuteratedwater,surfacehydroxygroupsaresuggestedtobetheactivecenters.