Beckmann-rearrangement of cyclododecanone oxime to ω-laurolactam in the gas phase

Article abstract of DOI:10.1016/j.jcat.2009.01.010

The classical route for the industrial production of ω-laurolactam is the homogeneously catalyzed Beckmann-rearrangement of cyclododecanone oxime in the liquid state using fuming sulfuric acid catalyst. Contrary to that, a completely different way is shown in the present work. In addition to the use of a solid acid catalyst, the vapor phase was chosen. From a process technical point of view it is a superior route compared with the classical one. Following intensive investigations of the vapor phase behavior of substrate, product and the main by-products, a catalyst screening of the most promising materials was performed. In addition, a modification of the most active catalysts was carried out to get more information about reaction sites and to optimize the catalyst activity. Using an acid treated [Al,B]-BEA zeolite at a temperature of approx. 320 °C and reduced pressures, complete conversion combined with excellent selectivity of 98% were obtained. The accumulation of reactants in the fixed bed was less than 5 wt%. Furthermore, investigations of deactivation and regeneration behavior of the catalyst were done. It could be demonstrated that the catalytic material could be regenerated under oxidative atmosphere as well as under non-oxidative conditions through thermal desorption of the deactivating compounds without any measurable loss of catalytic performance.

Full text of DOI:10.1016/j.jcat.2009.01.010

Journal of Catalysis 263 (2009) 42–55
Contents lists available at ScienceDirect
Journal of Catalysis
www.elsevier.com/locate/jcat
Beckmann-rearrangement of cyclododecanone oxime to ω-laurolactam in the gas
phase
∗
W. Eickelberg, W.F. Hoelderich
Chemical Technology and Heterogeneous Catalysis, University of Technology RWTH Aachen, Worringerweg 1, 52074 Aachen, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The classical route for the industrial production of ω-laurolactam is the homogeneously catalyzed
Beckmann-rearrangement of cyclododecanone oxime in the liquid state using fuming sulfuric acid
catalyst. Contrary to that, a completely different way is shown in the present work. In addition to the
use of a solid acid catalyst, the vapor phase was chosen. From a process technical point of view it is
a superior route compared with the classical one. Following intensive investigations of the vapor phase
behavior of substrate, product and the main by-products, a catalyst screening of the most promising
materials was performed. In addition, a modification of the most active catalysts was carried out to get
more information about reaction sites and to optimize the catalyst activity. Using an acid treated [Al,B]-
Received 6 November 2008
Revised 19 January 2009
Accepted 20 January 2009
Available online 13 February 2009
Keywords:
ω-Laurolactam
Cyclododecanone oxime
BEA zeolite
◦
BEA zeolite at a temperature of approx. 320 C and reduced pressures, complete conversion combined
Beckmann rearrangement
Gas phase reaction
with excellent selectivity of 98% were obtained. The accumulation of reactants in the fixed bed was
less than 5 wt%. Furthermore, investigations of deactivation and regeneration behavior of the catalyst
were done. It could be demonstrated that the catalytic material could be regenerated under oxidative
atmosphere as well as under non-oxidative conditions through thermal desorption of the deactivating
compounds without any measurable loss of catalytic performance.
© 2009 Elsevier Inc. All rights reserved.
1. Introduction
neous catalysis, wherein the catalytic material can be separated
from the reaction mixture and reused again. In this work a closer
look on zeolitic catalysts is given, since these led to good results
for the Beckmann-rearrangement of cyclohexanone oxime to ε-
caprolactam [2–7].
The most well-known polyamide is Nylon 6. Its monomer ε-
caprolactam is one of the 50 most important bulk chemicals in the
world, with an estimated annual production of 4.4 million tons
worldwide [1,35]. Another very important polyamide is Nylon 12,
which is characterized by superior mechanical, chemical and
thermo-mechanical load capacities. The classical synthesis route
for ω-laurolactam starts from 1,3-butadiene, through the inter-
mediates 1,5,9-cyclododecatriene, cyclododecane, cyclododecanone
and cyclododecanone oxime, which undergoes a Beckmann-rearran-
gement to form ω-laurolactam (Scheme 1).
The standard catalyst for industrial plants for the oximation and
rearrangement is fuming sulfuric acid. Generally ammonia is used
to neutralize the product mixture. The disadvantage of this pro-
cedure is the enormous production of ammonia sulfate, causing
some ecological concerns in addition to an economical drawback.
Starting with the optimization and reengineering of the old reac-
tion pathways, important producers nowadays focus their efforts
on new synthesis routes. A solution to the problem even for world
scale plants could be the change from homogeneous to heteroge-
Corma et al. [8] reported a heterogeneously catalyzed rear-
rangement of cyclododecanone oxime in the liquid state. They car-
ried out the reaction batch-wise with chlorobenzene under reflux
◦
at 130 C and ambient pressure during 24 h. The catalysts used
were H-ZSM-5 and [Al]-BEA with molar Si/Al ratios of 31 to 10,000.
A non-dealuminated [Al]-BEA (Si/Al-ratio = 34) turned out to be
the most active material. The selectivity was approximately 98%
and the conversion higher than 92%. The only by-product formed
during the reaction was cyclododecanone. Later on, the same group
published results where they used MCM-41 and ITQ-2 structures
as catalysts for the reaction [9,10]. The drawback of these reaction
routes was that the catalyst could be used only once and could not
be regenerated due to very strong adsorption of heavier products.
Our research focused also first on solvents in the liquid and su-
percritical phase. The liquid phase was chosen because of the high
boiling point of the feed and the product. Unfortunately, also in our
case the catalyst could be used only once due to the fact that the
deposits could not be removed. A paper concerning this research
will be published separately. Due to the results obtained thereby,
the research strategy was changed. The aim of this work was to
Corresponding author.
E-mail address: hoelderich@rwth-aachen.de (W.F. Hoelderich).
*
0021-9517/$ – see front matter © 2009 Elsevier Inc. All rights reserved.
doi:10.1016/j.jcat.2009.01.010

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
43
Table 1
BEA zeolites prepared by the group of Mr. F. Fajula, CNRS, in Montpellier.
Catalyst
Treatment
BEA2
BEA3
BEA5
BEA7
PT262
PT271
PT313
PT349
PT326/328
Dealuminated [Al]-BEA
Dealuminated [Al]-BEA
Dealuminated [Al]-BEA
Dealuminated [Al,B]-BEA
Dealuminated [Al]-BEA
Dealuminated [Al]-BEA
Dealuminated [Al,B]-BEA
Dealuminated [Al]-BEA
Dealuminated [Al]-BEA
carry out the Beckmann rearrangement in the gas phase, which
originally was thought not to be possible. An important step to
build up such a reactor system is the observation of the thermo-
dynamical properties of the substrate, the product and the main
by-products of the rearrangement reaction. The vapor pressures of
the compounds involved in the reaction were investigated in de-
tail. Theoretical calculations were done using different incremental
methods and the results were compared with the experimental re-
sults.
For the presented reaction, a broad range of zeolitic and non-
zeolitic catalysts was applied under different conditions. Even high
◦
temperatures of above 300 C could be used without any thermal
decomposition of the unstable starting material cyclododecanone
oxime. The deactivation and regeneration behavior of the catalyst
was investigated as well as the nature the catalytically active sites.
2. Experimental
2.1. Catalysts
For the catalyst pre-selection some standard catalysts were
tested. Degussa provided Aerosil and H-ZSM-5 material, Grace pro-
vided Z-alumina and USY catalysts. The [B]-MFI zeolite was syn-
thesized according to the patent of BASF [US 6884743].
In addition, some catalytically interesting materials such as
MCM-41 (all silica) [Catalyst A], TS-1 [Catalyst B], [Al] MCM-41
[Catalyst C] and the [B]-BEA [Catalyst D] were prepared in our
group and applied.
Si-MCM-41 (all silica) [Catalyst A]: In the first step, 350 g (35%)
TEAOH, 659.5 g H2O and 70.3 g tetradecyltrimethyl ammonia bro-
mide were stirred for one hour under argon atmosphere and at
room temperature. Then 30.59 g Aerosil-200 SiO2 was added and
the mixture stirred again for three hours. In the next hour 83.7 g
Aerosil-200 and 175.8 g H2O were added continuously and stirred
for three more hours, before the mixture was put in a steel au-
◦
toclave for one week at 130 C. Finally the obtained material was
washed with deionized water, filtered, dried and calcined.
The synthesis of the TS-1 [Catalyst B] material was performed
based on a route developed by Serrano et al. [11,12].
[B]-BEA [Catalyst D] was synthesized and calcined according to
the method of De Ruiter et al. [13,14]. For a slight deboronation,
the raw material was treated for 60 min with HCl-solution (pH 6)
at room temperature. The resulting material has a Si/B-ratio of ap-
prox. 32. For a stronger deboronation, the raw material was treated
for 24 h with HCl-solution (pH 5) at room temperature. After this
treatment, the catalyst showed a Si/B-ratio of approx. 700 [Catalyst
D deb.].
A broad range of dealuminated and/or deboronated BEA zeolites
were synthesized by the group of F. Fajula, CNRS in Montpellier
(Table 1).
For the dealumination treatment, a route developed by Des
Courieres et al. [15] was used.
For the use in the gas phase reactor system all catalysts were
pressed with a weight of 4 tons, crushed again and sieved. The
Scheme 1. Synthesis of ω-laurolactame.

44
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
fraction with a grain size distribution of 1.0–1.4 was used in the
tubular reactor.
2.2. Characterization
X-ray powder diffraction (XRD) was carried out using a Siemens
D5000 (CuKα1,2, secondary monochromator, variable diaphragm
◦
V20, angular velocity of 1, 2 min−1). Elemental analysis (ICP-AES)
was performed using a Spectroflame D (Spectro). BET and ni-
◦
trogen sorption isotherms were measured (at −196 C) using a
ASAP 2000 (Micrometrics). NMR measurements were conducted
on Bruker DSX 500. For thermogravimetric analysis
a Netsch
209/2/E equipped with a STA 409 controller was used (heating rate
◦
2 C min−1, Al2O3 crucibles were used with α-Al2O3 as reference).
NH3-TPD was performed on a Porotec, TPDRO 1100. The already
◦
calcined material was heated to 550 C for 24 h under helium at-
mosphere. Then the ammonia was adsorbed at room temperature
for 3 h (atmosphere: 3 vol% NH3 in Helium, flow: 0.02 l/min). To
remove the physisorbed water, the catalyst was heated to up to
◦
150 C under helium. During the measurement the system was
◦
−1
◦
up to 1000 C (helium flow: 0.02
heated up with 15 C min
l/min).
Fig. 1. System for vapor pressure measurements.
The IR-spectra were taken with the system of Nicolte (Protégé
460), but with a modification of the cell to measure also crys-
talline substances. For that, a special carrier was installed inside
the cell, where a wafer with a diameter of 13 mm could be fixed.
The wafer with a material density of 5–10 mg/cm2 was prepared in
a press by Gasby Specac. The wafer was heated with a heating coil
fixed in a ceramic casing, wherein the temperature measurement
was located. The wafer temperature was regulated by a Eurotherm-
PID-controller. The cell windows were made of KBr. Furthermore,
a high-vacuum-pump (Fa. Edwards E2M12) was connected to the
measuring cell to evacuate the cell to a pressure of 10
The analysis of the product mixture was generally performed
using gas chromatography. For these measurements, a system of
Hewlett–Packard (HP 6890 Series, Chem Station) was used.
low Si/Al-ratio, cyclohexane was used as solvent, because the pre-
ferred solvent isopropanol reacts on the alumina sites. The feed so-
lution was pumped through a capillary (inner diameter of 0.5 mm)
into the vaporization system, where the preheated carrier gas was
purged to vaporize the substrate solution immediately. Then the
reaction mixture was heated in the preheating zone to the reac-
tion temperature and fed into the fixed bed with a diameter of
6 mm and a length of approx. 250 mm where the catalyst was
packed. To quench the reaction mixture together with the solvent,
after the reactor a cooling trap (liquid nitrogen) was connected at
the outlet of the tubular reactor. Behind the cooling trap a vacuum
pump with an air needle valve was installed to control the sys-
tem pressure. To create a homogeneous temperature distribution,
the heated air was circulated in the oven by a propeller.
−3
mbar.
2.3. Vapor pressure measurement
The standard reaction conditions were: reaction temperature:
325 C, system pressure: 50 mbar, amount of catalyst: 1.0 g, feed
◦
To measure the vapor pressure of the substrate cyclodode-
canone oxime, the product ω-laurolactam and the main by-
product cyclododecanone, a pressure cell was built as shown in
Fig. 1. The cell (stainless steel, material: 1.4571) was installed in
a temperature-controlled oven. The pressure indicator (Edwards,
APG/NPMW/16 ST/ST) was attached to the top of the steel cell.
A second capillary was passed out of the oven and was connected
to a vacuum pump (Edwards, Model E2M-12).
flow: approx. 10 g/h, substrate concentration in the feed solution:
3.0 wt%, WHSV: approx. 0.3 goxime/(gcat h), carrier gas: approx.
3.5 Nl/h N2
After 120 min TOS (time on stream) a sample of the product
mixture from the cooling trap and a sample of the catalyst were
taken and analyzed. For the long-term reaction study the cooling
trap was changed every 60 min and the content was analyzed.
For the measurements, a certain amount of material was filled
into the steel cell and set to the system. The oven was heated to
up to 80 C and evacuated for one hour to remove impurities. Be-
2.5. Regeneration
◦
For regeneration, the same reaction system as described was
taken. After the reaction the deactivated catalyst was regenerated
under the following regeneration conditions: 550 C, 1013 mbar, ca.
3.5 Nl/h air or nitrogen as regeneration gas. Duration of regenera-
tion: approx. 12 h.
fore the measurement was started, the valve was closed and the
◦
◦
system was heated stepwise (10 C) up to 200 C. In each temper-
ature step, the system was held at constant temperature until the
equilibrium was reached and no more pressure increase could be
◦
◦
detected. At the end the cell was cooled down again to 80 C to
compare the starting pressure with the one after the measurement.
A sample of the test substance was analyzed.
3. Results and discussion
3.1. Vapor pressure
2.4. Catalytic experiments
The determination of the vapor pressures of substrate, product
and the main by-product cyclododecanone is an essential key value
for the process of the gas phase rearrangement of cyclododecanone
oxime to laurolactam.
Fig. 3 shows the results of the theoretical calculation of the va-
por pressure. The boiling point was determined using the method
The reactor system for the gas phase rearrangement was in-
stalled in a single temperature-controlled oven (Fig. 2). The feed
solution was cyclododecanone oxime dissolved in isopropanol with
a concentration of 3 g oxime per 100 g solvent, which is the upper
solubility limit at room temperature. While using catalysts with a

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
45
Fig. 2. Gas phase reactor system.
of Miller et al. [16–18], the critical data analogous to the method of
Joback et al. [19,20] and finally the vapor pressure was calculated
based on the considerations of Gomez-Nieto and Thodos [21–23].
The vapor pressure of cyclododecanone oxime is shown in
For the cyclic ketone cyclohexanone the selected method fits
very well to the base data. Both curves are congruent (see Fig. 4).
The measured vapor pressure of cyclododecanone oxime of up
◦
to 200 C and the already discussed data from the incremental cal-
◦
culation are shown in Fig. 5A. Two very important facts are respon-
sible for the deviation between measurement and theoretic data:
first the error of the incremental method. Especially at low tem-
peratures the error of the method is comparatively high. The error
between these curves is in the same range as the error of the ana-
log reaction system (see Fig. 4A) at low temperatures. The second
and main influencing factor on the error is the instability of the
Fig. 3A. At standard reaction conditions (T = 325 C) this substrate
has a calculated vapor pressure of approx. 130 kPa or 1.3 bar,
◦
and at the minimum reaction temperature (T = 200 C) a vapor
pressure of 6.7 mbar. Laurolactam shows comparable values (see
◦
Fig. 3B). At standard reaction conditions (T = 325 C) laurolactam
has a calculated vapor pressure of approx. 115 kPa or 1.15 bar, and
◦
at the minimum reaction temperature (T = 200 C) a vapor pres-
◦
cyclic keto oxime. Even at low temperatures of 130 to 150 C the
sure of 7.2 mbar.
oxime decomposes to ammonia and cyclododecanone. This decom-
position is generally greater at higher temperatures. Between 150
and 200 C it was not possible to adjust the equilibrium between
In the case of cyclododecanone, some additional Antoine-data,
determined by DuPont [24], were used to determine its vapor
pressure. Fig. 4 shows these values together with the results of
the theoretical calculation. At lower temperatures the curves show
◦
gas and liquid state of cyclododecanone oxime. The cell pressure
increased constantly, due to the decomposition and the built up of
ammonia. After cooling down the system again, the starting pres-
sure was not reached, which is a sign of the formation of gaseous
substances. By opening the measurement system, the characteris-
tic smell of ammonia was noticed and the GC-analysis showed the
production of cyclododecanone during the measurement.
However, laurolactam showed a stable chemical behavior. Dur-
ing the measurement no decomposition was observed and a stable
equilibrium could be adjusted to the system at each temperature.
Nevertheless, the measured vapor pressure is higher than the the-
oretical values. Thereby the error of the incremental method is
responsible for this deviation, too.
◦
a difference. The vapor pressure between 120 and 280 C, deter-
mined by the incremental method, is lower than the one from
DuPont. However, both curves are in the uncritical area, where
condensation of cyclododecanone could not take place during the
reaction.
To prove the accuracy of the chosen method, the vapor pressure
of the chemically similar reaction system cyclohexanone oxime to
ε-caprolactam was studied. The well-known vapor pressure data
of cyclohexanone oxime, ε-caprolactam and cyclohexanone were
compared with the vapor pressure investigated via incremental
calculations (see Fig. 4). In the case of cyclohexanone oxime (see
Fig. 4A), the vapor pressure determined via incremental meth-
Section 3.2 will show that these data are sufficient for the
present investigation.
◦
ods between 120 and 240 C is lower than that taken from the
◦
database. At temperatures of above 240 C the curves are almost
congruent.
3.2. Partial pressure distribution of the feed gas
For caprolactam the vapor pressure data determined by incre-
mental method, are in the whole temperature interval higher than
the base data (see Fig. 4B). For lactames a better fitting method
could not be found, but in the scope of the present work this error
is acceptable.
To ensure that all compounds, particularly the substrate and the
products, are in the gas phase, the partial pressure of each reaction
partner had to be checked. If the partial pressure is lower than the

46
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
(A)
(A)
(B)
(B)
(C)
(C)
Fig. 4. Comparison of the used incremental methods with the reaction system of
cyclohexanone oxime (A)/caprolactam (B)/cyclohexanone (C).
Fig. 3. Theoretical vapor pressure as function of temperature determination via
incremental methods. (A) Cyclododecanone oxime, (B) laurolactam, (C) cyclodode-
canone.
the test reaction a dealuminated [Al]-BEA (BEA5) with a high cat-
alytic activity for the rearrangement was used. For a significant
result the catalyst mass in the reactor system was increased to
3.0 g instead of 1.0 g as for the standard reaction.
vapor pressure, which was investigated in Section 3.1, this com-
pound is in the gaseous state.
The partial pressure distribution was determined using the data
of Table 2. For the given standard reaction mixture of a carrier gas
flow of 3.5 Nl/h N2 and a feed flow of approx. 10 g/h with an con-
centration of 3.0 wt%, the fraction of cyclododecanone oxime or
laurolactam of the partial pressure is only 0.056% of the system
pressure. Even at high system pressures of around 1000 mbar the
partial pressure of substrate or product is far below the vapor pres-
sure (refer to Section 3.1) at minimum reaction temperatures. This
means that all compounds are gaseous under each reaction con-
dition adjustment and no condensation takes place, even with the
error of the vapor pressure calculation determined in Section 3.1.
For the reactions at different temperatures the dealuminated
[Al]-BEA (BEA5) treated with HNO3 (Si/Al-ratio: 557) from CNRS
was used. The reactions were carried out at 200, 250, 300 and
◦
350 C. The other parameters remained constant.
Fig. 6 illustrates how the temperature influenced the conver-
sion. The initial conversion for all temperatures was at a high level
◦
of 100%. At a low reaction temperature of 200 C the conversion
decreased rapidly to 60% after 360 min TOS. At higher tempera-
◦
tures, the catalyst kept its high activity. At 250 C after 360 min
TOS, 93% of the oxime were still converted. After increasing the
◦
reaction temperature to 300 or 350 C, no decrease in conversion
was observed anymore during the reaction time of 6 hours. That
means that higher temperatures help to facilitate the desorption of
the products and the deactivation by self-inhibition is reduced.
Cyclododecanone oxime is a very unstable molecule, which de-
composes easily to cyclododecanone. Especially at temperatures
3.3. Investigation of the reaction parameters
3.3.1. Temperature effect
The temperature has an important influence on the conversion
of cyclododecanone oxime and the selectivity of laurolactam. For
◦
higher than 130 C the thermal decomposition rate increases. In

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
47
(A)
Fig. 6. Conversion as function of TOS (time on stream) at different temperatures.
Catalyst: 3.0 g dealuminated [Al]-BEA (BEA5), system pressure: 50 mbar, WHSV:
−1
approx. 0.1 goxime gcatalyst h−1, carrier gas: 3.5 Nl/h N2.
ity. On the contrary, the selectivity improved at a temperature of
◦
◦
250 C. Even at 300 and 350 C, selectivities of more than 98%
could be obtained. The reason for this is the very short residence
time of less than a second in the reactor system. After the flash
evaporation of the oxime, the reaction gas entered the catalyst
fixed bed immediately, where the substrate was rearranged to lau-
rolactam. Without any catalytic influence, the thermodynamically
preferred decomposition would take place.
(B)
The most important advantage of high temperatures is the
much better desorption of the products from the active sites. Fig. 8
shows the material accumulation curves at different temperatures.
Fig. 5. Comparison of the theoretical determined data to the measurement. (A) Cy-
clododecanone oxime, (B) laurolactam.
◦
The strongest hold-up was clearly at temperature around 200 C.
During the first 180 min TOS almost 100 wt% of the fed material
remained in the system. When the temperature was increased to
250 C, only 45 wt% were held up within the first hour, and from
Table 2
◦
Real gas data of the reaction mixture compounds.
180 to 360 min TOS approx. 20 wt% remained in the fixed bed. At
Critical
pressure
[Pa]
Critical
temperature constant a
[K]
“Van der Waals” “Van der Waals”
◦
constant b
300 C, 10–15 wt% were accumulated and this value is in the error
[Pa m6/mol2]
[m3/mol]
◦
range of the measurement. At a temperature of 350 C the hold-up
Nitrogen
Isopropanol
3.40E+06
126,2
1.37E−01 [25]
1.58E+00 [16]
6.17E+00
3.87E−05 [16]
1.11E−04 [16]
2.67E−04
increased again slightly to approx. 20 wt%. At this state probably
compounds of a high molecular weight were formed on the sur-
face, which could not be removed easily anymore.
Cyclododecanone 3.20E+06 [26] 823 [17]
oxime
Laurolactam
An interesting issue was the by-product composition at differ-
2.80E+06 [17] 920 [17]
8.82E+00
3.41E−04
◦
ent reaction temperatures (Fig. 9). At 200 C cyclododecanone was
formed. The long residence times favored the formation of the ke-
◦
view of this property it was expected that at higher reaction tem-
peratures the selectivity should decrease. Fig. 7 shows the selectiv-
ity as function of the TOS at different temperatures. Surprisingly,
higher temperatures did result in a deterioration of the selectiv-
tone. When the temperature was increased to 250 C, no more
cyclododecanone formation could be detected, and only a small
amount of new unknown compounds were found. Higher reac-
tion temperatures again favored the formation of cyclododecanone
−1
−1
,
Fig. 7. Selectivity as function of TOS at different temperatures. Catalyst: 3.0 g dealuminated [Al]-BEA (BEA5), system pressure: 50 mbar, WHSV: approx. 0.1 goxime
g
catalyst h
carrier gas: 3.5 Nl/h N2.

48
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
Fig. 8. Material accumulation as function of TOS at different temperatures. Catalyst: 3.0
g dealuminated [Al]-BEA (BEA5), system pressure: 50 mbar, WHSV: approx.
−1
0.1 goxime gcatalyst h−1, carrier gas: 3.5 Nl/h N2.
Fig. 9. By-product composition at different reaction temperatures. Catalyst: 3.0
g dealuminated [Al]-BEA (BEA5), system pressure: 50 mbar, WHSV: approx.
−1
0.1 goxime gcatalyst h−1, carrier gas: 3.5 Nl/h N2.
and the consecutive reaction of cyclododecanone to 2-dodecenal.
In addition the ring opening to cyanoundecene was increasingly
◦
detected at temperatures of 300 C and higher. This olefin has the
tendency to polymerize easily.
3.3.2. Pressure effect
A dealuminated [Al]-BEA (BEA2) material treated with HNO3
and a Si/Al-ratio of 434 (after the regeneration tests) was used
to study the influence of the pressure. Fig. 10 shows the conver-
sion and the selectivity as function of the system pressure and
corresponding partial pressure of cyclododecanone oxime and lau-
rolactam.
The selectivity to laurolactam is strongly influenced by the pres-
sure. At a partial pressure lower than 0.1 mbar laurolactam is
formed almost exclusively. With increasing system pressure, and
with it partial pressure, the selectivity decreased to approx. 30%
at about 1000 mbar. Low pressure facilitates desorption of the
formed products from the active sites, resulting in higher selec-
tivity. Another sign of a better desorption is the high production
of ring-opening products and faster deactivation of the catalyst at
higher system pressures, which is characteristic for long residence
times on the acid sites and polymerization of the ring opening
products such as cycloundecene.
Fig. 10. Influence of the pressure on the conversion and the selectivity. Catalyst:
1.0 g dealuminated [Al]-BEA (BEA2). Reaction temperature: 300 C, WHSV: approx.
0.3 goxime/(gcat h), carrier gas: 3.5 Nl/h N2.
◦
was known that in the gas phase rearrangement of cyclohexanone
oxime to caprolactam delocalized silanol groups, especially silanol
nests, are the catalytically active sites that catalyze the reaction
very well, particular focus on silanol rich materials was taken [7].
Fig. 11 shows some selected results of the screening test.
3.4. Catalyst screening
The material providing highest selectivity for the rearrange-
ment of cyclododecanone oxime to laurolactam in the gas phase is
For the screening tests quite a number of catalysts were chosen
in addition to the very active zeolites with BEA structure. Since it

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
49
◦
Fig. 11. Activity of different types of zeolitic and non-zeolitic catalysts under standard conditions. Reaction temperature: 325 C, system pressure: 50 mbar, WHSV: approx.
0.3 goxime/(gcat h), carrier gas: approx. 3.5 Nl/h N2.
the dealuminated [Al]-BEA zeolite (Si/Al-ratio: 260) [PT262]. Even
though the non-dealuminated BEA (Si/Al-ratio: 13.4) [BEA_raw] led
to higher conversion, the acid treated variation is much more in-
teresting due to its excellent selectivity (see Fig. 11, PT262). The
Brønsted acid sites of the [Al]-BEA [BEA_raw] are to strong at stan-
The titanium–silicalite 1 (TS-1, Catalyst B), which contains
Lewis-acid sites on its surface was also tested. At standard con-
ditions the activity was poor. The conversion was lower than 10%
and the selectivity was less than 70%. Remarkable in this context
is the increasing activity at higher reaction temperatures. Not only
the conversion could be improved, but the selectivity increased as
◦
dard reaction conditions (325 C), thus side reactions occur. The
◦
main by-product formed during the reaction was the ring-opening
product cyanoundecene. Weaker acid sites are much more selec-
tive, and with the right setup the highest yield could be achieved.
Surprisingly, deboronated [B]-BEA zeolite (Si/B-ratio: approx. 700)
[JNB_30/31 deb. =Catalyst D deb.] is not that selective, although it
carries a similar silanol structure on the surface and the same pore
structure.
well. At a reaction temperature of 375 C the conversion increased
to 25% and a selectivity of 90% was obtained.
In summary it can be said that BEA zeolite is the most promis-
ing catalyst due to its excellent selectivity for the rearrangement
of cyclododecanone oxime to laurolactam. Therefore, several mod-
ifications of BEA zeolite have been carried out and the catalytic
performance of those modified materials was investigated.
The Brønsted acid sites of USY with a SiO2/Al2O3-modul of 28
are too strong. As for the non-dealuminated [Al]-BEA [BEA_raw],
the selectivity is lower than in the case of dealuminated [Al]-BEA
[PT262] and the formation of cyanoundecene is observed.
Of interest was the behavior of the [B]-MFI in the rearrange-
ment reaction of cyclododecanone oxime, as this zeolitic cata-
lyst results in excellent performance for the reaction of cyclohex-
anone oxime to caprolactam [6,7]. However, the reaction tests have
shown only a weak activity of this zeolite catalyst in the lauro-
lactam formation. Only 8% of cyclohexanone oxime was converted
with a moderate selectivity of 85% to ω-laurolactam. In case of the
bulkier cyclododecanone oxime, the pore opening could not be en-
tered and furthermore, no pore mouth selectivity as in the case of
ε-caprolactam [7] could take place. Therefore, only some reaction
occurred on the outer crystal surface.
The simplest catalyst is amorphous silica (FK700) without any
zeolitic pore structure, but with a huge amount of silanol groups
on the surface. The activity is comparatively weak. Only 20% of the
oxime was converted and a selectivity of only 75% was observed
even though terminal and geminal silanol groups were present, but
those do not catalyze the rearrangement very well, as is also know
for the ε-caprolactam production.
MCM-41 is characterized by a distinctive mesopore system. The
substrate can therefore enter the pore system easily. Nevertheless,
the catalytic performance of Catalyst A (=JNM_69C-77) is poor.
Only 8% of the oxime were converted with a low selectivity of
just 65%. The silanol configuration on the surface is similar to the
one of amorphous silica, because the MCM-41 (all silica) was not
treated after the synthesis like the active [Al]-BEA, and hence none
of the catalytically highly active defect sites were introduced into
the framework.
3.5. Catalyst modification
3.5.1. Post synthesis treatment of [Al]-BEA zeolite
The dealumination treatment significantly influenced the cat-
alytic activity of BEA zeolite catalysts in the Beckmann-rearrange-
ment of cyclododecanone oxime to ω-laurolactam. Several struc-
tural analyses were carried out to get more information about the
active sites. Fig. 12 shows the IR bands in the range between 3800
and 3600 cm−1. The starting [Al]-BEA zeolite has two intensive
−1
bands at 3741 and 3734 cm
and two weak signals at 3615 and
3781 cm−1. Kirisci et al. reported that the small peak at 3615 cm
is the result of bridged hydroxyl groups of framework alumina [25,
26]. The species were assumed to have a very strong acidity. The
−1
same group gives an explanation for the intensive bands at 3741
−1
and 3734 cm
with the shoulder up to 3741 cm−1. This area is
related to internal and external terminal silanol groups with com-
paratively weak Brønsted acidity. The band at 3781 cm
−1
is called
the “very high frequency”-band. Löffler at al. [27] and Kustov et
al. [28] report that these species are terminal Al–OH groups with
medium acidity.
Due to the acid treatment using HNO3, framework and extra
framework alumina species were removed. This work was carried
out by the group of F. Fajula. The variations PT271 and PT262 are
[Al]-BEA zeolites treated to a different extent, by leaving the cat-
alyst twice the time in the HNO3-solution. Their spectra are also
shown in Fig. 12. The bands at 3615, 3781 and 3673 cm
removed completely or alternatively covered by the broad band
between 3300 and 3700 cm−1. According to Jia et al. and our own
results [7,29], this expanded peak is the result of a high concen-
tration of silanol nests, formed during the acid treatment, when
−1
are

50
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
◦
Fig. 13. FTIR spectra after pyridine adsorption and 60 min desorption at 150 C and
−2
Fig. 12. FTIR-spectra of the non-dealuminated [Al]-BEA and two dealuminated
(PT271, PT262) BEA zeolites.
10
mbar.
Table 3
Band allocation of the adsorbed pyridine.
−1
Band position [cm
]
Adsorbed species
Acid site character
1635
1621
1576
1545
1490
1455
1397
Pyridine ion
Pyridine
Pyridine
Pyridine ion
Pyridine and pyridine ion
Pyridine
Brønsted
Lewis
Lewis
Brønsted
Lewis and Brønsted
Lewis
Pyridine ion
Brønsted
T-atoms were removed from the framework and defects have been
created.
With the help of pyridine adsorption during the FTIR measure-
ment, it is possible to get detailed information about the character
of the acid sites. The method is discussed intensely in the Litera-
ture. The report of Creyghton et al. [30] provides a good overview
of the acid character of the adsorbed pyridine species. The respec-
tive band positions are specified in Table 3.
Fig. 14. Temperature programmed desorption of ammonia of the raw material and
the two dealuminated variations.
The peak area is a direct indicator for the density of acid
sites. By integrating this peak area, the amount of adsorbed
ammonia can be determined. In the case of the raw material
The results of the FTIR measurements with pyridine adsorption
for the already mentioned BEA zeolites [Al]-BEA, PT271 and PT262
◦
−1
BEA_raw, 670 μmol/gcat at 280 C and 414 μmol/gcat were des-
are shown in Fig. 13. The peak at 1545 cm
is a characteristic sig-
◦
orbed at 450 C. For the material PT262 402 μmol/gcat and for
PT271 690 μmol/gcat were desorbed at 280 C and no further NH3
nal for the type of acidity. It represents the pyridine ion attached
to strong Brønsted acid sites. The disappearance of this peak gives
evidence that the newly created material lost strong Brønsted acid-
ity during the acid treatment. However, next to the Lewis acid sites
◦
desorption was detected at higher temperatures.
Finally, these materials were tested for their catalytic activity.
Fig. 15 illustrates conversion, selectivity and accumulation of re-
actants in the fixed bed as function of Si/Al-ratio of the tested
catalysts. Furthermore, the amount of adsorbed ammonia in TPD-
measurements is shown. For the reaction the standard conditions
weak Brønsted acidity is still left, as can be seen by the slight band
−1
at 1635 cm
.
With the help of NH3-TPD measurements, the acidic strength
and the density of the acid sites on the zeolite can be determined.
Therefore the non-dealuminated [Al]-BEA and the differently HNO3
treated e.g. dealuminated PT271 and PT262 were investigated with
this method (see Fig. 14). All three catalysts revealed a distinctive
◦
at 325 C and 50 mbar were used.
As previously discussed, the dealumination treatment has a cru-
cial influence on catalyst performance. Even if the conversion of
cyclododecanone oxime drops with increasing Si/Al-ratio, the se-
lectivity increased to an excellent level of almost 100%. The second
crucial advantage is the reduced reactant accumulation of the cat-
alyst, which is associated to a faster deactivation of the catalyst.
Strong Brønsted acidic sites of alumina species are responsible for
the formation of by-products, especially the ring opening to cya-
noundecene, which has high polymerization tendency.
◦
peak at approx. 280 C, indicating weak acidic sites. Additionally,
◦
the starting [Al]-BEA shows a second NH3-desorption at 450 C,
indicating that this material has also strong acid sites in addi-
◦
tion to weaker ones. At temperatures of 280 C the ammonia was
desorbed from the weakly acidic silanol groups [31,32] and at
◦
higher temperatures of approx. 450 C the ammonia desorbed from
the stronger acidic hydroxyl groups of the Brønsted acid alumina
species. In the case of PT271 and PT262 the high temperature peak
disappeared completely. That means that only weakly acidic sites
remained.
When T-bonded alumina sites were removed the from the BEA
framework, highly selective silanol nests remained on the surface,
which were of only extremely weak Brønsted acidity. Such sites

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
51
Fig. 16. Activity of boron containing BEA zeolites at standard conditions.
Fig. 15. Conversion, selectivity and reactant accumulation in catalyst bed as func-
tion of the Si/Al-ratio and the amount of adsorbed ammonia (TPD-measurement) at
standard reaction conditions.
Table 4
Results of the ICP- and NH3-TPD-measurement of the zeolites PT262, PT313, BEA7
and [B]-BEA (Catalyst D).
Catalyst
Si/Al-ratio, Si/B-ratio
[mol/mol]
Amount of adsorbed NH3
[μmol/gcat
]
[Al]-BEA (PT 262)
[Al,B]-BEA (PT 313)
[Al,B]-BEA (BEA7)
[B]-BEA (Catalyst D)
260, –
320, 45
260, 37
Approx. 1500, 32
402
351
437
915
Fig. 17. Mass fraction of coke to catalyst after 8 h TOS at different reaction temper-
atures and under standard conditions.
catalyzed the rearrangement in a superb manner. Due to the acid
treatment, the hard accumulation of reactants was reduced to a
minimum level.
In Fig. 16 the results of the reaction tests are shown. Sur-
prisingly, the [B]-BEA showed the poorest catalytic performance
among these 4 boron containing BEA zeolites with a selectivity of
approximately 95%, a conversion of less than 25% and the highest
accumulation of the reactants and products.
3.5.2. Boron containing BEA zeolites
Other interesting catalysts in this context were boron-containing
BEA zeolites. Instead of alumina, boron oxide was incorporated
into the framework. To remove the T-sites, less aggressive treat-
ment was sufficient compared with the treatment in the case of
[Al]-BEA zeolites. During the deboronation procedure silanol nests
were created in the framework, as it was found by the Hoelderich
et al. for the [B]-MFI Zeolite used in the Beckmann rearrangement
of cyclohexanone oxime to ε-caprolactam [7].
The performance of the other three catalysts was much bet-
ter. The selectivities are at a high level of almost 100%. The most
remarkable attribute is the sharply increased conversion of PT313
and especially of BEA7. Using these BEA zeolites the conversion
more than doubled without any influence on selectivity and on the
accumulation of the reactants and products. The reason for the ex-
cellent performance could not be determined yet, but the catalytic
effect on the rearrangement was remarkable.
For the experiments three types of BEA zeolites were prepared
and applied. These materials have different fractions of boron ox-
ide and alumina introduced into the framework. Zeolites were
slightly dealuminated, or rather deboronated, and analyzed by ICP,
3.6. Deactivation/regeneration
Long-term reaction test have shown that the catalysts are
strongly deactivated after approx.
pyridine-FTIR, NH3-TPD. In the case of the pyridine-FTIR of these
8 h time on stream under
−1
samples no signal at 1545 cm
was detected. That means that
standard reaction conditions. After these 8 h the amount of or-
ganic compounds were measured with thermogravimetric analysis.
Fig. 17 shows the mass fraction of organic compounds adsorbed
on the catalyst or polymer compounds or coke blocking the active
sites of the zeolitic catalyst at different reaction temperatures.
At lower reaction temperatures the catalyst adsorbed high
amounts of organic substances. Desorption test have shown that
these residues were mainly substrate and product adsorbed on the
the strong Brønsted acidity of the strong active hydroxyl groups
from the alumina species was lowered to an insignificant level.
The results of the ICP and NH3-TPD-measurement are shown in
Table 4.
The dealuminated [Al]-BEA PT 262, which was already dis-
cussed in Section 3.5.1, is compared with the boron-containing
materials. The PT 313 and the BEA7 were [Al,B]-BEA zeolites differ-
ently treated with HNO3 according to the method of Des Courieres
et al. [15]. The longer the residence time in the treatment solution,
the less alumina and boron oxide species remain in the structures.
The [B]-BEA is almost alumina free.
PT262, PT313 and BEA7 desorbed during the NH3-measurement
402, 352 and 437 μmol/gcat, respectively. The [B]-BEA has a sig-
nificantly higher amount of desorbed ammonia indicating a higher
density of active sites. Thus, this BEA was supposed to show the
best catalytic performance.
◦
catalyst. At approx. 300 to 320 C a minimum of less than 5 wt%
material hold up was detected and due to this the highest yield of
laurolactam could be obtained. At this point the optimum condi-
tions for the gas phase reaction were achieved and the formation
of so-called white coke, oligomers of laurolactam was reduced due
to depolymerization.
For the regeneration of the catalyst two pathways are possi-
ble: oxidative and non-oxidative removal of the deactivating com-
pounds.

52
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
Fig. 18. Activity of a dealuminated [Al]-BEA (PT326/328) during 8 reaction cycles (standard reaction conditions) with intermediate oxidative regeneration.
Fig. 19. NH3-TPD measurements of fresh BEA and after 8 reaction/regeneration cy-
cles.
Fig. 20. XRD measurements of fresh BEA and after 8 reaction/regeneration cycles.
The standard regeneration with air was carried out at below
550 C for approx. 12 h. After this treatment all catalysts used
◦
the micro- and the mesopores did not change and the BET-surface
stayed at 520 m2/g.
Within the scope of these investigations, the dealuminated BEA
is stable over the regeneration treatments under oxidative condi-
tions. No loss of activity, no changes of the surface morphology
and zeolitic structure were observed.
recovered their complete initial activity. To observe the regener-
ability of the dealuminated [Al]-BEA rich in silanol groups with
a Si/Al-ratio of approx. 531, eight cycles of reaction with inter-
mediate regeneration under oxidative conditions were carried out
(Fig. 18).
The second regeneration pathway is the regeneration under in-
ert conditions (here under N2-atmosphere). The advantage could
be a smoother regeneration, without “burning” of the organic com-
pounds from the catalyst, to avoid hot spots and a possible long-
time deactivation due to silanol condensation. Because of the lim-
ited number of reaction/regeneration cycles, a weak silanol con-
densation was not detected. Hence the same test series as for
air-regeneration was done under nitrogen atmosphere, where the
deactivating compounds were removed through thermal desorp-
tion from the catalyst surface.
These reaction tests have shown that the activity of the catalyst
did not drop through the stress of this treatment. Selectivity and
conversion stay on the high level of almost 100%.
Before and after this treatment the catalyst was investigated
with ICP-AES, BET, XRD and NH3-TPD to determined the physical
structure and the surface morphology of the zeolite.
The ICP AES analysis showed the same Si/Al-ratio of approx.
531 for both samples. Therefore, a further dealumination of the
catalyst could not be observed. This assumption is supported by
the NH3-TPD (Fig. 19) measurement. Both catalysts have shown the
Fig. 22 shows the results of the activity test. Conversion and
selectivity remained high even after the eighth regeneration cycle
under nitrogen.
◦
same signal at 280 C with the same amount of adsorbed ammonia
(approx. 420 μmol/gcat), confirming that the kind and the number
of acid sites did not change during the tests.
To make sure that all deactivating compounds were removed
from the surface, the regenerated BEA was analyzed by TG
Also the zeolitic structure was stable. The XRD analysis (Fig. 20)
showed that the characteristic signal of BEA-structures [33] at
◦
(Fig. 23). Up to a temperature of 150 C large amounts of water,
◦
◦
◦
2θ = 7.8 and 22.4 did not change. Especially the signal at 22.4
which were adsorbed during the preparation for the measurement,
were desorbed. In the interesting temperature interval between
is a typical sign of the crystallinity of the zeolite [34]. Another
structural analysis was carried out via N2-BET-surface measure-
ment of the fresh and the used BEA (Fig. 21). The distribution of
◦
200 and 600 C no significant loss of mass was detected. The loss
◦
of mass at temperatures higher than 600 C was caused by the

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
53
Fig. 21. BET measurements of fresh BEA and after 8 reaction/regeneration cycles.
Fig. 22. Activity of a dealuminated [Al]-BEA (PT326/328) during 8 reaction cycles (standard reaction conditions) with intermediate non-oxidative regeneration.
be reactivated in the same way as with the standard oxidative re-
generation.
In addition to the different load of deactivating compounds at
various reaction temperatures, Fig. 24 shows the influence of the
◦
regeneration gas. A catalyst used in the reaction at 200 C is mainly
blocked due to the product formed. As already mentioned, these
substances could be removed through oxidation or desorption at
high temperatures.
◦
No significant difference of both 325 C-curves between nitro-
gen and air regeneration can be seen.
4. Conclusions
The aim of the present work was the investigation of the pos-
sibility of gas phase rearrangement of cyclododecanone oxime to
laurolactam over solid acid catalysts. To prove that all reactants
were in the gaseous state, vapor pressure measurements and the-
oretical calculations using incremental methods were carried out.
To study the catalytic performance a fixed bed reactor system
was chosen to screen different types of solid acids. The reaction
Fig. 23. TG analysis of a catalyst regenerated under nitrogen atmosphere.
typical condensation of silanol groups of the BEA zeolite. The ev-
idence was that through nitrogen regeneration the catalyst could

54
W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
◦
atures above 250 C more and more laurolactam polymerized to
oligomers—the so-called “white coke”—which is additionally block-
ing the active sites. Both compounds could be removed with an
◦
oxidative regeneration at 550 C. Eight reaction cycles with inter-
mediate regeneration have shown that the BEA zeolite is com-
pletely regenerable without any loss of its catalytic activity. An-
other interesting pathway is the non-oxidative regeneration under
◦
nitrogen atmosphere at 550 C, where the deactivating compounds
are removed through thermal desorption, which is the more gentle
treatment due to the prevention of hot-spots. Even here the cata-
lyst could be reactivated completely. Thermogravimetric analyses
have shown that no residues were left on the catalyst surface after
regeneration with nitrogen.
For the Beckmann rearrangement of cyclododecanone oxime to
ω-laurolactam zeolite catalysts have been used only in liquid re-
action systems so far. The disadvantages of this process are the
strong deactivation of the catalyst, the comparatively difficult re-
generation of the catalytic material and the high technical effort
caused by this. From a process technical point of view, a gas phase
rearrangement is the far better solution. A broad range of differ-
ent reactor systems is available. The results have shown that the
catalytic performance in the gas phase is excellent. Even in the
standard fixed bed reactor, selectivity and conversion of almost
100% in combination with a minimum reactant accumulation were
achieved. Thus, for a large-scale use, the route of a gas phase reac-
tion system should be chosen.
Fig. 24. Thermogravimetric analysis under air and nitrogen atmosphere of two cat-
alysts used at different reaction temperatures (200 and 325 C).
◦
tests have shown that BEA zeolite has the most promising struc-
ture. Thus, the investigations focused on this material. The starting
material [Al]-BEA showed strong catalytic activity, but due to the
strong Brønsted acidity, the formation of ring opening products
such as cyanoundecene was preferred. Consequently the selectiv-
ity was low. By modifying the BEA zeolite with post-synthesis
acid treatment, the alumina T-sites were removed from the BEA
framework, defects have been created and less Brønsted acidic
sites remained on the catalyst surface. Structural analysis with the
help of ICP, NH3-TPD and pyridine-FTIR have shown that delocal-
ized silanol groups were generated. Modified BEA zeolite catalysts
yielded far better performance. The conversion decreased slightly,
but the selectivity increased to an excellent level of almost 100%
in combination with a minimized accumulation of reactants and
products on the catalyst.
Acknowledgments
Particular thanks go to Mr. Fajula, CNRS, Montpellier and his
co-workers for the catalyst samples and for the intensive collabo-
ration. The authors are grateful to Mr. Lacroix and Mr. Hub, Arkema
for fruitful discussions and the financial support by Arkema is
gratefully acknowledged.
Remarkable are the results with boron containing BEA zeo-
lites. Using a dealuminated [Al,B]-BEA the conversion was more
than doubled with the same excellent selectivity and a minimum
accumulation. The BEA zeolite named BEA7 in the present work
showed the best catalytic activity.
References
[1] Product Focus, Chem. Week 10 (1999) 47.
[2] W.F. Hoelderich, Stud. Surf. Sci. Catal. 75 (1993) 127.
[3] W.F. Hoelderich, Stud. Surf. Sci. Catal. 46 (1989) 193.
[4] W.F. Hoelderich, in: G. Alberti, T. Bein (Eds.), Comprehensive Supramolecular
Chemistry, vol. 7, Pergamon, New York, 1996, p. 671.
[5] W.F. Hoelderich, J. Röseler, D. Arntz, DP 19608660, to Degussa AG.
[6] G.P. Heitmann, G. Dahlhoff, W.F. Hoelderich, Appl. Catal. A 185 (1999) 99.
[7] G.P. Heitmann, G. Dahlhoff, W.F. Hoelderich, J. Catal. 186 (1999) 12.
[8] M.A. Camblor, A. Corma, H. García, V. Semmer-Herlédan, S. Valencia,
J. Catal. 177 (1998) 267.
In addition to the catalyst, the reaction conditions were inves-
tigated. The reaction temperature has a crucial influence on the
adsorption and desorption process of the catalyst. At low reaction
◦
temperatures of less than 250 C, the formed products could not
be desorbed and the catalyst deactivated very fast. Consequently
the yield decreased rapidly after short reaction times. At higher re-
[9] M.J. Climent, A. Corma, V. Fomes, H. Garcia, S. Iborra, J. Miralles, I. Rodriguez,
Stud. Surf. Sci. Catal. 135 (2001) 3719.
◦
action temperatures this phenomenon disappeared. 325 C turned
out to be the optimum reaction temperature. At this point excel-
lent selectivities with a minimum accumulation in the fixed bed
were detected. It should be mentioned that the reactor setup is
quite important. Due to instable behavior of the cyclododecanone
[10] A. Corma, J. Catal. 186 (1999) 57.
[11] D.P. Serrano, M.A. Uguina, G. Ovejero, R.V. Grieken, M. Camacho, Microporous
Mater. 4 (1995) 273.
[12] G. Ovejero, R.v. Grieken, M.A. Uguina, D.P. Serrano, J.A. Melero, Catal. Let. 41
(1996) 69.
[13] R. De Ruiter, thesis, University of Technology, Delft, 1992.
[14] R. De Ruiter, J.C. Jansen, H. van Bekkum, Synthesis of Microporous Materials,
vol. 1, 1992, p. 167.
[15] T. Des Courieres, D. Anglerot, F. Fajula, E. Bourgeat-Lami C. Ziivkov, EP0488867
(1992), to Elf Aquitaine (FR).
[16] Perry’s Chemical Engineering Handbook, 6th ed., McGraw–Hill, 1984, p. 3.
[17] M. Tyn, T.W. Calus, Processing 21 (4) (1975) 16.
[18] H.G. Rackett, J. Chem. Eng. Data 15 (1970) 514.
[19] K.G. Joback, M.s. thesis in Chem. Engin., MIT, Cambridge, 1984.
[20] K.G. Joback, R.C. Reid, Chem. Eng. Commun. 57 (1987) 233.
[21] M. Gomez-Nieto, G. Thodos, IEC Fund. 17 (1978) 45.
[22] M. Gomez-Nieto, G. Thodos, IEC Fund. 16 (1977) 254.
[23] M. Gomez-Nieto, G. Thodos, Can. J. Chem. Eng. 55 (1977) 445.
[24] Website DuPont (January 2004), http://www.dupont.com/intermediates/
products/vle_cddk.html.
◦
oxime at temperatures higher than 130 C, the residence time of
the substrate in the hot reaction zone had to be minimized. The
solution is a flash evaporation of the dissolved substrate in the
reactor system. Thereby residence times of less than 1 s could
be achieved and the thermal decomposition to cyclododecanone,
which is thermodynamically preferred, was prevented.
Furthermore, a closer look was taken at the influence of the
partial pressure on the reaction. Low pressures are of advantage.
Using substrate partial pressures lower than 0.1 mbar, which cor-
responds to 200 mbar system pressure at standard reaction condi-
tions, supported the desorption of the formed laurolactam and the
selectivity increased.
Finally, the deactivation and regeneration behavior was inves-
[25] I. Kiricsi, C. Flego, G. Pazzuconi, W.O. Parker Jr., R. Millini, C. Perego, G. Bellussi,
J. Phys. Chem. 98 (17) (1994) 4627.
[26] C. Jia, P. Massiani, D. Barthomeuf, J. Chem. Soc. Faraday Trans. 89 (19) (1993)
3659.
◦
tigated. At lower reaction temperatures of less than 200–250 C
the formed product is mainly responsible for the deactivation, due
to its strong adsorption on the surface of the catalyst. At temper-

W. Eickelberg, W.F. Hoelderich / Journal of Catalysis 263 (2009) 42–55
55
[27] E. Löffler, U. Lohse, Ch. Peuker, G. Oehlmann, L.M. Kustov, V.L. Zholobenko, V.B.
[31] S.G. Hedge, R. Kumar, R.N. Bhat, P. Ratnasamy, Zeolites 9 (1989) 231.
[32] P.G. Smirniotis, E. Rickenstein, J. Catal. 140 (1993) 526.
Kazansky, Zeolites 10 (1990) 266.
[28] L.M. Kustov, V.L. Zholobenko, V.B. Kazansky, E. Löffler, U. Lohse, Ch. Peuker, G.
[33] J.M. Newsman, M.M.J. Treacy, W.T. Koetsier, C.B. de Gruyter, Proc. R. Soc. Lon-
Oehlmann, Zeolites 10 (1990) 304.
don A 420 (1988) 375.
[29] C. Jia, P. Massiani, D. Barthomeuf, J. Chem. Soc. Faraday Trans. 89 (19) (1993)
[34] A. Corma, A. Martinez, P.A. Arroyo, J.L.F. Monteiro, E.F. Sousa-Aguiar, Appl.
3659.
Catal. 142 (1996) 139.
[30] E.J. Creyghton, S.D. Ganeshie, R.E. Downing, H. van Bekkum, J. Mol. Catal. 115
(1997) 457.
[35] G. Dahlhoff, J.P.M. Niederer, W.F. Hoelderich, Catal. Rev.-Sci. Eng. 43 (4) (2001)
381–441.