R. Prins | Swiss Federal Institute of Technology (ETH) (original) (raw)

Papers by R. Prins

Chemistry - A European Journal, 2000

Alumina-supported catalysts from various sources and with different rhodium dispersions predomina... more Alumina-supported catalysts from various sources and with different rhodium dispersions predominantly yield the hydrogenation product perhydro-1-indanol in the liquid-phase hydrogenation of 1-indanol, while carbonsupported catalysts mainly give the C-O bond scission - hydrogenation product perhydroindane. Addition of organic or inorganic bases to the reaction mixture suppresses C-O bond scission. To distinguish between the two possible pathways for C-O bond scission of direct hydrogenolysis or dehydration followed by hydrogenation, deuteration studies have been carried out with carbon-supported catalysts. Not only 1-indanol but also indane and indene (the two possible mechanistic intermediates in the C-O bond scission routes) were deuterated. Information about the actual pathway has been obtained by determining the degree of deuteration and the positions at which deuterium is incorporated in the resulting perhydroindane product by means of mass spectrometry and 13C NMR spectroscopy. The results prove that C-O bond scission takes place primarily through the direct hydrogenolysis pathway on the carbon-supported catalysts. Direct hydrogenolysis occurs on the carbon support because of the formation of a better leaving group (OH2+) from the benzylic hydroxy group and its subsequent substitution by spillover hydrogen.

Carbon, 1987

Four carbon black samples differing in surface area, pH and surface properties (oxygen functional... more Four carbon black samples differing in surface area, pH and surface properties (oxygen functionality) were pore volume impregnated with aqueous molybdate solutions as to achieve a MO loading of 0.5 MO atoms per nm2 support surface area. Dispersion measurements obtained by means of X-ray photoelectron spectroscopy, dynamic oxygen chemisorption and transmission electron microscopy, indicated the presence of highly dispersed molybdate in all precursor samples, which upon sulfidation was converted into molybdenum sulfide with a particle size varying between 3.5 and 13.5 nm dependant on the type of carbon black support. To explain these dispersion differences the interaction between molybdate ions and the carbon surface was studied by means of FTIR and XPS. No major changes were observed in the oxygen functionality of the carbon black upon loading with molybdate. Some minor changes were, however, observed by means of FTIR which could point to a chemical reaction between an aryl ether functional group and the molybdate ions.

Applied Catalysis, 1987

The effect of vanadium oxide as support and promoter on supported rhodium catalysts on the CO hyd... more The effect of vanadium oxide as support and promoter on supported rhodium catalysts on the CO hydrogenation has been investigated at 0.15 and 4.0 MPa.

The Journal of Physical Chemistry, 1983

The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 w t % Rh/ y-A12... more The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 w t % Rh/ y-A1203 catalyst shows EXAFS oscillations due to rhodium-rhodium nearest neighbors, which proves the existence of rhodium metal crystallites. Adsorption of CO at room temperature on the reduced catalyst significantly decreases the amplitude of these EXAFS oscillations. This implies that CO adsorption on very small rhodium crystallites leads to a disruption of a significant number of the metal-metal bonds.

Surface Science, 1983

... If the XPS results warrant a conclusion it must be that rhodium particles on TiC>2 hav... more ... If the XPS results warrant a conclusion it must be that rhodium particles on TiC>2 have the same charge as those on M^O^, while platinum particles on TiO; may have a somewhat higher positive charge. ... Rev. Letters 41 (1978) 1425. [22] Tran Minh Duc, C. Guillot, Y. Lassailly, J ...

Applied Catalysis, 1985

The catalytic acitivity of Rh/Ti02 and Rh/A1203 catalysts for the hydrogenation of CO at atmosphe... more The catalytic acitivity of Rh/Ti02 and Rh/A1203 catalysts for the hydrogenation of CO at atmospheric pressure and 523 K was investigated. Normal, non-SMSI state Rh/Ti02 as well as Rh/Ti0 2 catalysts in the SMSI state with varying dispersion were studied. In all cases only hydrocarbons and no oxygenated products were formed. When measured at equal dispersions the activities of Rh/A1203 and non-SMSr Rh/Ti0 2 catalysts hardly differed. The specific activity of Rh/Ti02 catalysts increased an order of magnitude when changing the dispersion from 1.10 to 0.12. This increase in specific activity was acompanied by an increase in the olefin-to-paraffin ratio, but neither the selectivity to methane nor the probability for chain growth was affected much. Reduction of the Rh/Ti02 catalysts at 773 K decreased their initial activities substantially compared to reduction at 523 K, whereas the steady-state activities were hardly affected. Apparently the SMSI state is removed to a great extent during CO hydrogenation. The lowering effect of SMSr on activity was a function of dispersion. The effect was much more pronounced for small metal particles, indicating that SMSI might be due to covering.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

Applied Catalysis, 1984

The reducibility of platinum on y-Al203 and Ti02 was studied with the aid of temperature programm... more The reducibility of platinum on y-Al203 and Ti02 was studied with the aid of temperature programmed reduction. The reduction peak temperature was found to be dependent on the temperature of the primary oxidation after impregnation and drying. The higher the oxidation temperature the lower the TPR peak temperature and the higher the H2 consumption. During the oxidation small PtO formed which were more easily reduced than the original isola z part$c+les were ed Pt ions. For Pt/A1203 no decomposition of Pt02 was observed up to 750 K, while bulk PtO2 decomposed around 600 K. This demonstrated that there is a substantial interaction between Pt02 and Al For PtO much weaker and on z 03. z supported on Ti02 and Si02 this interaction is hese suppor s Al2O3.

Studies in Surface Science and Catalysis, 2001

ABSTRACT

Le Journal De Physique Colloques, 1984

TrAC Trends in Analytical Chemistry, 1982

Thin Solid Films, 1994

ABSTRACT

The Journal of Physical Chemistry B, 2002

Catalysts have been prepared by subliming CoCl 2 or CoBr 2 vapor onto the H form of the zeolite M... more Catalysts have been prepared by subliming CoCl 2 or CoBr 2 vapor onto the H form of the zeolite MFI, followed by replacing the halide ions by OH groups and subsequent heat treatments. The Co sites have been characterized by EXAFS and XANES spectra at liquid nitrogen temperature. The data are correlated with the H 2 -TPR profiles of the same samples and their catalytic performance in reducing NO x with hydrocarbons. Materials with fairly large Co 3 O 4 particles after calcination, displaying a Co-Co distance of 3.5 Å and negligible interaction between Co and T sites (T ) Si or Al), have a poor selectivity in NO x reduction, because such oxide particles catalyze the combustion of the hydrocarbon. In contrast, highly selective catalysts show no Co 3 O 4 clusters and distinct interaction between Co and T atoms. Heating in H 2 at 400°C reduces Co-oxo ions, while cobalt oxide clusters are incompletely reduced and isolated Co 2+ ions in exchange positions remain unreduced. The water formed in the reduction of oxo species can interact with Co 2+ ions, increasing their coordination number with oxygen. A preedge XANES peak at 7710 eV indicates an electric-dipole-forbidden, but quadrupole-allowed and vibronically allowed 1s-3d electronic transition.

The Journal of Physical Chemistry B, 1997

ABSTRACT

The Journal of Physical Chemistry B, 1997

ABSTRACT

Chemistry - A European Journal, 2000

Alumina-supported catalysts from various sources and with different rhodium dispersions predomina... more Alumina-supported catalysts from various sources and with different rhodium dispersions predominantly yield the hydrogenation product perhydro-1-indanol in the liquid-phase hydrogenation of 1-indanol, while carbonsupported catalysts mainly give the C-O bond scission - hydrogenation product perhydroindane. Addition of organic or inorganic bases to the reaction mixture suppresses C-O bond scission. To distinguish between the two possible pathways for C-O bond scission of direct hydrogenolysis or dehydration followed by hydrogenation, deuteration studies have been carried out with carbon-supported catalysts. Not only 1-indanol but also indane and indene (the two possible mechanistic intermediates in the C-O bond scission routes) were deuterated. Information about the actual pathway has been obtained by determining the degree of deuteration and the positions at which deuterium is incorporated in the resulting perhydroindane product by means of mass spectrometry and 13C NMR spectroscopy. The results prove that C-O bond scission takes place primarily through the direct hydrogenolysis pathway on the carbon-supported catalysts. Direct hydrogenolysis occurs on the carbon support because of the formation of a better leaving group (OH2+) from the benzylic hydroxy group and its subsequent substitution by spillover hydrogen.

Carbon, 1987

Four carbon black samples differing in surface area, pH and surface properties (oxygen functional... more Four carbon black samples differing in surface area, pH and surface properties (oxygen functionality) were pore volume impregnated with aqueous molybdate solutions as to achieve a MO loading of 0.5 MO atoms per nm2 support surface area. Dispersion measurements obtained by means of X-ray photoelectron spectroscopy, dynamic oxygen chemisorption and transmission electron microscopy, indicated the presence of highly dispersed molybdate in all precursor samples, which upon sulfidation was converted into molybdenum sulfide with a particle size varying between 3.5 and 13.5 nm dependant on the type of carbon black support. To explain these dispersion differences the interaction between molybdate ions and the carbon surface was studied by means of FTIR and XPS. No major changes were observed in the oxygen functionality of the carbon black upon loading with molybdate. Some minor changes were, however, observed by means of FTIR which could point to a chemical reaction between an aryl ether functional group and the molybdate ions.

Applied Catalysis, 1987

The effect of vanadium oxide as support and promoter on supported rhodium catalysts on the CO hyd... more The effect of vanadium oxide as support and promoter on supported rhodium catalysts on the CO hydrogenation has been investigated at 0.15 and 4.0 MPa.

The Journal of Physical Chemistry, 1983

The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 w t % Rh/ y-A12... more The X-ray absorption spectrum of the Rh K edge of a highly dispersed reduced 0.57 w t % Rh/ y-A1203 catalyst shows EXAFS oscillations due to rhodium-rhodium nearest neighbors, which proves the existence of rhodium metal crystallites. Adsorption of CO at room temperature on the reduced catalyst significantly decreases the amplitude of these EXAFS oscillations. This implies that CO adsorption on very small rhodium crystallites leads to a disruption of a significant number of the metal-metal bonds.

Surface Science, 1983

... If the XPS results warrant a conclusion it must be that rhodium particles on TiC>2 hav... more ... If the XPS results warrant a conclusion it must be that rhodium particles on TiC>2 have the same charge as those on M^O^, while platinum particles on TiO; may have a somewhat higher positive charge. ... Rev. Letters 41 (1978) 1425. [22] Tran Minh Duc, C. Guillot, Y. Lassailly, J ...

Applied Catalysis, 1985

The catalytic acitivity of Rh/Ti02 and Rh/A1203 catalysts for the hydrogenation of CO at atmosphe... more The catalytic acitivity of Rh/Ti02 and Rh/A1203 catalysts for the hydrogenation of CO at atmospheric pressure and 523 K was investigated. Normal, non-SMSI state Rh/Ti02 as well as Rh/Ti0 2 catalysts in the SMSI state with varying dispersion were studied. In all cases only hydrocarbons and no oxygenated products were formed. When measured at equal dispersions the activities of Rh/A1203 and non-SMSr Rh/Ti0 2 catalysts hardly differed. The specific activity of Rh/Ti02 catalysts increased an order of magnitude when changing the dispersion from 1.10 to 0.12. This increase in specific activity was acompanied by an increase in the olefin-to-paraffin ratio, but neither the selectivity to methane nor the probability for chain growth was affected much. Reduction of the Rh/Ti02 catalysts at 773 K decreased their initial activities substantially compared to reduction at 523 K, whereas the steady-state activities were hardly affected. Apparently the SMSI state is removed to a great extent during CO hydrogenation. The lowering effect of SMSr on activity was a function of dispersion. The effect was much more pronounced for small metal particles, indicating that SMSI might be due to covering.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1996

Applied Catalysis, 1984

The reducibility of platinum on y-Al203 and Ti02 was studied with the aid of temperature programm... more The reducibility of platinum on y-Al203 and Ti02 was studied with the aid of temperature programmed reduction. The reduction peak temperature was found to be dependent on the temperature of the primary oxidation after impregnation and drying. The higher the oxidation temperature the lower the TPR peak temperature and the higher the H2 consumption. During the oxidation small PtO formed which were more easily reduced than the original isola z part$c+les were ed Pt ions. For Pt/A1203 no decomposition of Pt02 was observed up to 750 K, while bulk PtO2 decomposed around 600 K. This demonstrated that there is a substantial interaction between Pt02 and Al For PtO much weaker and on z 03. z supported on Ti02 and Si02 this interaction is hese suppor s Al2O3.

Studies in Surface Science and Catalysis, 2001

ABSTRACT

Le Journal De Physique Colloques, 1984

TrAC Trends in Analytical Chemistry, 1982

Thin Solid Films, 1994

ABSTRACT

The Journal of Physical Chemistry B, 2002

Catalysts have been prepared by subliming CoCl 2 or CoBr 2 vapor onto the H form of the zeolite M... more Catalysts have been prepared by subliming CoCl 2 or CoBr 2 vapor onto the H form of the zeolite MFI, followed by replacing the halide ions by OH groups and subsequent heat treatments. The Co sites have been characterized by EXAFS and XANES spectra at liquid nitrogen temperature. The data are correlated with the H 2 -TPR profiles of the same samples and their catalytic performance in reducing NO x with hydrocarbons. Materials with fairly large Co 3 O 4 particles after calcination, displaying a Co-Co distance of 3.5 Å and negligible interaction between Co and T sites (T ) Si or Al), have a poor selectivity in NO x reduction, because such oxide particles catalyze the combustion of the hydrocarbon. In contrast, highly selective catalysts show no Co 3 O 4 clusters and distinct interaction between Co and T atoms. Heating in H 2 at 400°C reduces Co-oxo ions, while cobalt oxide clusters are incompletely reduced and isolated Co 2+ ions in exchange positions remain unreduced. The water formed in the reduction of oxo species can interact with Co 2+ ions, increasing their coordination number with oxygen. A preedge XANES peak at 7710 eV indicates an electric-dipole-forbidden, but quadrupole-allowed and vibronically allowed 1s-3d electronic transition.

The Journal of Physical Chemistry B, 1997

ABSTRACT

The Journal of Physical Chemistry B, 1997

ABSTRACT