Search

The influence of the catalyst Sn content on the production of fatty alcohol from oleic acid by selective hydrogenation was studied using Rh‐Sn‐B catalysts supported on TiO2. The crystal phase of the support was analyzed by X‐ray diffraction (XRD), the reduction state of the metal phase by temperature‐programmed reduction (TPR), and the electronic state of surface species by X‐ray photoelectron spectroscopy (XPS). The metal activity was evaluated by the dehydrogenation of cyclohexane. It was found that the increase in Sn content leads to a proportional drop in the catalytic activity, which could be related to a metallic interaction between Rh and Sn, as shown by TPR. Oxide and metallic Sn, as well as Rh0 and Rh3+, were found by XPS on the catalyst surface. Metallic Rh was, however, found in higher concentration than oxidized Rh in all cases. The yield to fatty alcohols increased with Sn content, and its maximum value for oleyl and stearyl alcohol was 96%. Furthermore, a higher yield (88.3%) was obtained out of unsaturated fatty alcohol (oleyl alcohol), which has proved to be more valuable than saturated alcohol. This was attributed to an adequate Rh/Sn ratio, which modulates the hydrogenating activity of Rh and makes the metal function more selective for hydrogenation of the carbonyl group. The influence of the support on the catalyst performance decreases as the Sn content increases. The support has a practically negligible influence on the catalyst activity for 4–5 wt.% of Sn content. [ABSTRACT FROM AUTHOR]

Alumina and silica‐alumina supported Ru‐Pt catalysts were evaluated for the ring opening of naphthenes. Pt, Ru, and Ru‐Pt catalysts were prepared by the impregnation of inorganic precursors over γ‐alumina and silica‐alumina supports. The catalysts were evaluated by temperature programmed reduction (TPR), pyridine temperature programmed desorption (TPD), CO‐FTIR, and by test reactions of 33DM1B isomerization, cyclohexane dehydrogenation, cyclopentane hydrogenolysis, and the ring opening of decalin. The strong interaction between the metals (Pt‐Ru) was attributed to their reductions occurring simultaneously. The acidity and strength of the acid sites of the monometallic Ru catalyst were higher than those of the monometallic Pt catalyst. The total acidity (Lewis and Brønsted) and the strength of the acid sites were higher for the silica‐alumina supported catalysts. The silica‐alumina catalysts had 10 times more Brønsted acidity than the γ‐alumina ones and an increased activity and selectivity to decalin ring opening products. Supported monometallic Ru had the best performance for the ring opening reaction. [ABSTRACT FROM AUTHOR]

The catalytic performance of a Pt–Ir/Al2O3 catalyst for the selective ring opening of decalin was studied as a function of time. Fresh and used catalysts were evaluated with the reaction tests of cyclohexane dehydrogenation and cyclopentane hydrogenolysis to assess the metal function properties. The transformation of decalin was used as a test reaction for the ring opening of naphthenes. For this test the yield to ring contraction products passed through a maximum at intermediate values of conversion while yields to dehydrogenation, ring opening, and cracking products increased with conversion. Coke deposition also increased with reaction time but its distribution on the metal and acid sites did not change. Coke was more toxic for hydrogenolysis than for de/hydrogenation and therefore the products ratio of (ring opening)/(dehydrogenation) decreased at end of the reaction. Higher yields to dehydrogenated products produced a higher coke deposition while high activity in both hydrogenolysis and dehydrogenation favored the ring opening reaction. [ABSTRACT FROM AUTHOR]

The influence of indium on the properties of Pt–Re/Al2O3 catalysts used in naphtha reforming is studied. The addition of indium to the Pt–Re/Al2O3 catalyst produces a big decrease of acidity. It also produces an inhibition of the metal function, i.e., dehydrogenation and hydrogenolysis activity. The reaction of n-C5 isomerization shows that indium addition decreases the total activity of the Pt–Re catalyst but increases the selectivity to the i-C5 isomers. The selectivity to low cost light gases (C1–C3) is particularly decreased. The reaction of n-C7 reforming showed that addition of indium increases the stability of the catalyst and the selectivity to aromatics, and decreases the production of light gases. [ABSTRACT FROM AUTHOR]