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... 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.
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... 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)... 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 ...
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Catalysts resembling reforming catalysts were prepared to contain finely dispersed 0.75% Pt, 0.7% Re, or 0.35% Pt plus 0.1-2% Re on chlorided ..gamma..-alumina. The catalysts were dried in an oxidizing atmosphere and studied by... more
Catalysts resembling reforming catalysts were prepared to contain finely dispersed 0.75% Pt, 0.7% Re, or 0.35% Pt plus 0.1-2% Re on chlorided ..gamma..-alumina. The catalysts were dried in an oxidizing atmosphere and studied by temperature-programed reduction. Up to a Re/Pt ratio of 0.6:1 the metals were completely reduced in hydrogen below 255°C, i.e., the platinum catalyzed rhenium reduction. A small amount of added water (< 50 ppm) also promoted rhenium reduction. Segregation of the metals occurred in oxygen above 200°C, but at 100°C, the rate of segregation was slow. These results suggested that under reforming conditions, Pt-Re catalysts are completely reduced bimetallic clusters. The mechanisms of reduction, cluster formation, and oxidative segregation are discussed.
Incipient-wetness impregnation of gamma-Al(2)O(3) with HAuCl(4) and subsequent removal of chlorine with NaOH, and deposition-precipitation of HAuCl(4) on TiO(2) at pH 7 resulted in supported Au(3+) species. Time-resolved in situ XAS at... more
Incipient-wetness impregnation of gamma-Al(2)O(3) with HAuCl(4) and subsequent removal of chlorine with NaOH, and deposition-precipitation of HAuCl(4) on TiO(2) at pH 7 resulted in supported Au(3+) species. Time-resolved in situ XAS at the Au L(3) edge showed that the Al(2)O(3)-supported oxidic or hydroxidic species were reduced in hydrogen at 440 K to yield small metallic gold clusters. The Au(3+) precursor decomposed to metallic gold in inert atmosphere at 573 K and in oxidizing atmosphere above 623 K. In all atmospheres, initially small clusters were formed that gradually grew with increasing temperature. The TiO(2)-supported species were considerably less stable. In hydrogen and carbon monoxide, Au(0) clusters of 1 to 1.5 nm were formed at room temperature, which was the lowest temperature studied. In inert and oxidizing atmosphere, the Au(3+) precursor decomposed fully to metallic gold at 530 K, as shown by XAS and temperature-programmed experiments. Large clusters were obtained already in the initial stage of reduction. Residual chlorine inhibited the reduction and led to sintering of the gold clusters. Exposure of the TiO(2)-supported catalyst precursor to light or the X-ray beam led to partial reduction, and STEM showed that storage of the reduced gold clusters under ambient conditions led to agglomeration and bimodal cluster-size distributions.
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The hydrodenitrogenation (HDN) of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the... more
The hydrodenitrogenation (HDN) of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the hydrodesulfurization (HDS) of corresponding alkanethiols were studied over sulfided NiMo/Al2O3. Alkanethiols and dialkylamines were primary products in the HDN of the amines with secondary α-carbon atoms, formed by substitution of the amine group by H2S or an alkylamine. Alkanes and alkenes were secondary products, formed from elimination and hydrogenolysis of the alkanethiols, as confirmed by the similar alkenes/alkane ratios in the HDN of the alkylamines and HDS of the corresponding alkanethiols. 2-Methyl-2-butylamine and benzylamine reacted much faster than the amines with secondary α-carbon atoms. Methylbutenes and methylbutane were the primary products of 2-methyl-2-butylamine, and toluene was the primary product of benzylamine. This and the different methylbutenes/methylbutane ratios in the HDN of 2-methyl-2-butylamine and HDS of 2-methyl-2-butanethiol indicate that 2-methyl-2-butylamine, with a tertiary α-carbon atom, and the activated benzylamine react by means of an E1 mechanism.
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To study the problems inherent in deep hydrodesulfurization (HDS), the separate and simultaneous HDS of 4,6-dimethyldibenzothiophene and hydrodenitrogenation (HDN) of pyridine were investigated over a Ni-MoS2/γ-Al2O3 and a Pd/γ-Al2O3... more
To study the problems inherent in deep hydrodesulfurization (HDS), the separate and simultaneous HDS of 4,6-dimethyldibenzothiophene and hydrodenitrogenation (HDN) of pyridine were investigated over a Ni-MoS2/γ-Al2O3 and a Pd/γ-Al2O3 catalyst. The HDS of 4,6-dimethyldibenzothiophene and its three intermediates, 4,6-dimethyl-tetrahydro-dibenzothiophene, 4,6-dimethyl-hexahydro-dibenzothiophene and 4,6-dimethyl-dodecahydro-dibenzothiophene, demonstrated that, over the Pd catalyst, the (de)hydrogenation reactions were relatively fast compared to the C–S bond breaking
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ABSTRACT The gas-phase nitration of toluene was studied over a solid-acid zeolite beta catalyst with two different nitrating agents, HNO3 and N2O4, in a setup for continuous nitration. The selectivity of the reactions to 4-nitrotoluene... more
ABSTRACT The gas-phase nitration of toluene was studied over a solid-acid zeolite beta catalyst with two different nitrating agents, HNO3 and N2O4, in a setup for continuous nitration. The selectivity of the reactions to 4-nitrotoluene was good, but the catalysts deactivated within a few hours. HNO3 gave higher yields than N2O4, but both HNO3 and N2O4 required a temperature lower than 160°C to obtain acceptable yields and less oxidation products. At higher temperatures, catalyst deactivation was accelerated and the yield of nitrotoluene decreased. Lowering the feed rate of toluene led to a slower deactivation of catalyst. The deactivation of the catalyst was caused by pore blocking due to liquid reaction products as well as coke formation. Unlike in liquid-phase nitration, dealumination did not play a role in the deactivation of the catalyst, which could be regenerated by calcination in air.
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... Max Lauwiner, Ronny Roth and Paul Rys *. ... The selectivity for the nitro group reduction vis-à-vis that of the azo bridge in substituted nitrophenylazobenzenes is higher for compounds with the nitro group in para position to the azo... more
... Max Lauwiner, Ronny Roth and Paul Rys *. ... The selectivity for the nitro group reduction vis-à-vis that of the azo bridge in substituted nitrophenylazobenzenes is higher for compounds with the nitro group in para position to the azo bridge than for the corresponding meta ...
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... AF Gusovius, TC Watling and R. Prins Corresponding Author Contact Information , E-mail The Corresponding Author. Laboratory of Technical Chemistry, Swiss Federal Institute of Technology (ETH), 8092 Zürich, Switzerland. Received 28... more
... AF Gusovius, TC Watling and R. Prins Corresponding Author Contact Information , E-mail The Corresponding Author. Laboratory of Technical Chemistry, Swiss Federal Institute of Technology (ETH), 8092 Zürich, Switzerland. Received 28 December 1998; revised 21 May 1999 ...