Apatitic Tricalcium Phosphate as Novel Smart Solids for Supported Aqueous Phase Catalysis
FULL PAPERS
Table 2. Comparison of the reactivity of the three apatitic
The complex [Rh (m-S-t-Bu) (CO) (TPPTS) ] was prepared
2 2 2 2
as previously described. by reaction for 15 minutes at room
temperature of 2 equivalents of TPPTS with the complex [Rh2
supports in SAPC for the hydroformylation of oct-1-ene.[a]
[14]
HAP
±
PTCap OCPap
1 2.5
(
m-S-t-Bu) (CO) ] dissolved in methanol.
2 4
HPO content per cell unit
4
Initial water content
< 1 wt % 3 wt % 6 wt %
yield
0% 63% 93%
Catalyzed Reactions
[
a]
Experimental conditions: 80 8C, 18 hours, hydration rate
6%, errors on the yields: Æ 2%.
Catalytic tests were carried out in a 150 mL stainless steel
stirred autoclave heated by a thermostatic oil bath. All tests
1
were done with the same amounts of TPPTS (0.141 g, 2.27 Â
À4
1
(
0
mol), of complex [Rh (m-S-t-Bu) (CO) (TPPTS) ]
2 2 2 2
previously, this decrease is essentially due to a loss of
À5
0.038 g, 2.26 Â 10 mol), 2.3 g of the support, 57 mL of
À2
water from the support leading to small droplets toluene, and 2.86 g (2.55 Â 10 mol) of oct-1-ene. Given
containing the catalyst. It can also be due in part to the amounts of deionized water, ranging between 0 and 1.5 mL,
limited decomposition of tricalcium phosphate into were added to reach the desired hydration level. It is worth
mentioning that the values quoted correspond to the water
HAP and monetite, since both of these phosphates are
content including the initial residual water on the support, and
not convenient for SAPC as has been shown before.
are expressed as w/w % with regard to the mass of the resulting
hydrated support. In addition, all the experiments have been
carried out with an initial organic phase (oct-1-ene toluene)
Conclusion
saturated with water (otherwise the experiments are not
reproducible and are insignificant). The reactor was pressur-
This study shows the unexpected use of calcium ized three times at 2 bar with an equivalent mixture of
hydrogen and carbon monoxide. Then, the autoclave was
phosphates in the field of catalysis. Usually phosphates
pressurized at 2 bar with the same gas mixture, and the reactor
are introduced directly as catalytic solids, for instance,
mixed phosphates of cerium and terbium.[20] They are
also employed as supports for small metallic catalytic
particles embedded at their surface. For the first time,
we demonstrate that apatitic tricalcium phosphate is a
very useful support for supported aqueous phase
catalysis, and is much better than those used up to
was heated to 80 8C at 1870 rpm. The reactor was pressurized
with 5 bar of syngas and the pressure kept constant for usually
3
hours at 5 bar inside the reactor. Then, the gas mixture feed
was stopped and the reactor was cooled to room temperature.
Finally, the reactor was depressurized and the liquid and solid
phases were separated by filtration.
The organic phase was analyzed by gas phase chromatog-
now. Furthermore, the richness of the chemistry of raphy on a Carlo Erba HRGC 5160 chromatograph equipped
apatites could allow further developments since many with a flame ionization detector and a capillary column Alltech
Econopac FFAP (30 m; 0.53 mm; 1.2 mm), Tdet 200 8C, PH2
possibilities for substitution are permitted by this
structure. These results appear attractive and further
work is in progress.
0
.45 bar.
Analytical Methods
Experimental Section
Samples of apatitic tricalcium phosphate, before or after
catalytic runs were analyzed by several techniques. The X-ray
diffraction diagrams were obtained with a CPS 120 INEL
diffractometer using the Ka1 line emitted by an anticathode of
cobalt, (l 1.78892 ä). FTIR analyses covered the 4000 ±
Reagents
Reagents were calcium nitrate Ca(NO ) ¥ 4 H O, and dia-
3
2
2
À1
mmoniumphosphate (NH ) HPO (Prolabo, analytical grade).
400 cm region, on a Perkin-Elmer FTIR 1600 spectrometer
4
2
4
Other reagents and solvents used in the synthesis of catalyst or
in the catalytic tests were purchased from Aldrich and SDS,
and used without further purification. Rhodium trichloride
trihydrate and tris(m-sodium sulfonatophenyl)phosphine
with pellets of 1 mg of sample and 300 mg of KBr. NMR
measurements were carried out on a Bruker MSL-300 NMR
3
1
spectrometer operating at 120 MHz for P and at 300 MHz for
1
H. About 150 mg of powder sample was packed into a
(
TPPTS) were generous loans from Engelhardt-Comptoir,
zirconium rotor. All spectra were obtained by magic angle
spinning (MAS). Chemical shifts were referenced to external
85% H PO . Morphology of samples was observed using a
Lyon-Alemand-Louyot, and Hoechst (Ruhrchemie plant),
respectively.
3
4
Apatitic tricalcium phosphate was prepared at room tem-
perature, at pH 10, by double decomposition of calcium nitrate
and diammonium phosphate.[ After washing, the precipitate
was dried at 80 8C overnight. Then, it was checked by the
analytical techniques described below. Its composition corre-
sponds to Ca (PO ) (HPO )(OH) and contains 3 w/w %
scanning electron microscope JEOL JSM-6400 after a slight
metallization with silver. Local composition was estimated by
energy dispersion analysis of the X-rays induced by the
electronic beam (EDS). In addition, the initial sample was
examined by chemical analysis after acidic dissolution (the
level of calcium was determined by volumetric titration, and
phosphorus by colorimetry of the phosphovanadomolybde-
num complex), its specific surface area measured by BET
9]
9
4
5
4
residual water, as determined by the loss in weight after
heating at 100 8C for 3 h.
Adv. Synth. Catal. 2002, 344, 406 ± 412
411