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ple, natural variations in the starting material [11]; moreover,
the reproducibility of the catalyst preparation with respect to
the surface groups may become difficult. Zeolites, crystalline
aluminosilicates with varying structures and acidities during
synthesis, have been used very successfully in hydrocarbon
processing, but their use in fine chemical synthesis is still in
a relatively early state of development [12,13].
Because in earlier work [10] we found that a more acidic
carbon support was more active in hydrogenolysis than a
less acidic carbon support, in the present work we investi-
gated the possibility of using zeolites impregnated with pal-
ladium. An important advantage of zeolites is that they can
be readily synthesized in a reproducible manner. In this work,
a mixture of HMR isomers (HMR 1 and 2) extracted from
Norway spruce was hydrogenolyzed to MAT over palladium-
impregnated H-Beta-300, H-Beta-150, H-Beta-25, H-Beta-11,
H-Y, H-Mordenite, H-MCM-41, H-ZSM-5, SiO2, and Al2O3.
H-Beta-25 without palladium was also investigated. The influ-
ence of the initial ratio of isomers to reduction temperature was
studied as well.
5 ◦C/min). Na-Beta-11 zeolite (Si/Al weight ratio 11) was syn-
thesized as described previously [14] with some modification.
A solution was prepared by mixing colloidal silica (Ludox As
40, Aldrich) with distilled water. Another solution was prepared
by dissolving sodium aluminate (NaAlO2) in distilled water and
adding tetraethylammonium hydroxide ((C2H5)4NOH, Fluka).
The two solutions were mixed together and stirred for a while.
The gel thus formed was transferred into a Teflon cup, which
was inserted into a 300-ml stainless steel autoclave (Parr In-
struments). The synthesis was carried out at 150 ◦C for 96 h.
After completion, the autoclave was quenched and the crys-
talline product was filtered, washed with distilled water, dried
at 100 ◦C for 12 h, and calcined at 550 ◦C for 9 h in a muf-
fle oven (at a heating rate of 5 ◦C/min). Na-ZSM-5 zeolite was
synthesized in an autoclave at 150 ◦C for 48 h as described pre-
viously [15] with some modifications. The reagents used in the
synthesis were fumed silica (SiO2, Aldrich), sodium hydrox-
ide (NaOH, Merck), aluminium hydroxide (Al(OH)3, Aldrich),
tetrapropylammonium bromide ((C3H7)4NBr, Fluka), and dis-
tilled water. After synthesis was complete, the autoclave was
quenched in cold water, and the synthesized materials were fil-
tered and washed thoroughly with distilled water. Na-ZSM-5
samples were dried at 100 ◦C for 12 h, and templates were
removed by calcination at 540 ◦C for 8 h (at a heating rate
of 5 ◦C/min). Synthesis of Na-MCM-41 mesoporous molec-
ular sieve was conducted in an autoclave as described previ-
ously [16] with some modifications. The synthesis was per-
formed by preparing solutions A, B, and C. Solution A was
prepared by mixing fumed silica (SiO2, Aldrich) with dis-
tilled water under continuous stirring. Solution B was prepared
by adding tetramethylammonium silicate ((CH3)4NOH·2SiO2,
Aldrich) to sodium silicate (Na4O4Si, Merck) and stirring
for 15 min. Solution C was prepared by dissolving tetrade-
cyltrimethylammonium bromide (C17H38BrN, Aldrich) in dis-
tilled water. Solution B was slowly added to solution A and
stirred for 20 min. Subsequently, solution C was introduced
under vigorous stirring. A required amount of aluminium iso-
propoxide ([(CH3)2CHO]3Al, Aldrich) was mixed, and the gel
solution was stirred for 30 min. After the pH of the prepared gel
was measured, the gel was placed in a Teflon cup, which was
then inserted into an autoclave. The synthesis was performed at
100 ◦C in an oven for 24 h. After completion of the synthesis,
the reactor was quenched, and the mesoporous material was fil-
tered and washed thoroughly with distilled water. Na-MCM-41
was dried at 110 ◦C for 12 h and calcined at 550 ◦C for 10 h
(at a heating rate of 5 ◦C/min). The sodium forms of Beta-11,
ZSM-5, and MCM-41 were ion-exchanged with 1 M ammo-
nium chloride (NH4Cl) for 48 h and washed with distilled water
to remove any chloride ions. After subsequent drying at 100 ◦C
for 12 h, the proton forms were obtained by calcination of NH4
forms at 500 ◦C for 4 h (at a heating rate of 5 ◦C/min). The sup-
port materials were impregnated with palladium by the vacuum
evaporation impregnation method in a rotary evaporator, using
aqueous solution of palladium nitrate as a precursor. The cata-
lysts were dried at 110 ◦C for 12 h and calcined at 400 ◦C for
3 h (at a heating rate of 5 ◦C/min).
Hydrogenolysis was performed in 2-propanol at 70 ◦C under
hydrogen and nitrogen atmospheres in a stirred glass reactor.
The reaction scheme is depicted in Fig. 1a, and the difference
between the isomers is illustrated in Fig. 1b. The catalysts were
characterized by nitrogen physisorption, direct current plasma
atomic emission spectrometry (DCP), X-ray powder diffraction
(XRPD), CO pulse chemisorption, transmission electron mi-
croscopy (TEM), and Fourier transform infrared spectroscopy
(FTIR; pyridine adsorption).
2. Experimental
2.1. Synthesis of HMR
HMR was isolated from Norway spruce knots as follows.
First, the knots were ground and extracted in an acetone–water
mixture (90:1 vol/vol). Then the extract was concentrated in a
rotary evaporator and purified by flash chromatography on sil-
ica (eluent dichloromethane:ethanol, 97.5:2.5 vol/vol) to yield
a pure HMR solution, which was evaporated in the rotary evap-
orator. The material was 93% pure as determined by gas chro-
matography. The major impurity was the lignan conidendrin.
The HMR 1/HMR 2 ratio was approximately 1:3.
2.2. Catalysts
Palladium (5 wt% nominal loading)-impregnated H-Beta-
300, H-Beta-150, H-Beta-25, H-Beta-11, H-Y, H-Mordenite,
H-ZSM-5, H-MCM-41, SiO2, and Al2O3 were synthesized as
follows. NH4-Beta-300, NH4-Beta-150, NH4-Beta-25, NH4-
Mordenite-20, and NH4-Y-12 zeolites (SiO2/Al2O3 molar ra-
tios of 300, 150, 25, 20, and 12, respectively) were supplied
by Zeolyst International, SiO2 was provided by Merck, and
Al2O3 was obtained from UOP. The proton forms of the zeo-
lites were obtained through calcination of the NH4 form of the
materials in a muffle oven at 500 ◦C for 4 h (at a heating rate of