Kinetic and deactivation modelling of biphenyl liquid-phase hydrogenation over bimetallic Pt–Pd catalyst (original) (raw)
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Applied Catalysis A-general, 2004
The hydrogenation of tetralin, naphthalene, and phenanthrene as individual feed components and in diesel model feeds has been studied over a series of mono-and bimetallic Pt and Pd supported on ␥-alumina at 300 • C and 500 psig in excess of H 2 . The influence of fluorine on activity level and sulfur resistance was evaluated in the presence of controlled concentrations (0-1000 ppm) of dibenzothiophene (DBT).
Fuel Processing Technology, 2012
The effect of the composition of the metallic function (Pt and Pt-Pd) and acid function (HUSY and Hβ zeolites) in the catalysts has been studied in the hydrocracking of LCO in the 350-400°C range. The remaining operating conditions are: 50 bar; H 2 /LCO molar ratio (n H2), 8.90 mol H2 (mol LCO) − 1 ; space velocity (WHSV), 4 h − 1 ; time on stream (TOS), 0-24 h. The reaction indices studied are the conversions of hydrocracking and hydrodesulphurization and the yields of naphtha, medium distillates, LPG and dry gases. It has been proven that the metallic function, the acidity of the acid function and temperature increase give way to an increase in the activity remaining in the catalyst in the pseudo-stable state (subsequent to deactivation for 5 h time on stream). Likewise, these conditions enhance the production of naphtha and medium distillates with a lower content of aromatics and a higher one of paraffins and naphthenes. Pt-Pd/HY catalyst is very stable and has a high capacity for producing naphtha and medium distillates at 400°C.
Hydrogenation of aromatics over supported Pt-Pd catalysts
Applied Catalysis A-general, 2002
Silica–alumina (SA)- and β-zeolite (βZ)-supported Pt, Pd, and Pt-Pd catalysts were compared for the simultaneous hydrogenation (HYD) of toluene (T) and naphthalene (NP) in the presence of dibenzothiophene (DBT). Under the selected conditions (P=50 bar, T=448 K, weight hourly space velocity (WHSV)=25.8 h−1), all the catalysts were resistant to poisoning with 113 ppm of S (as DBT). The turnover frequency (TOF) calculated at zero time decreased in the following order: T>NP>DBT. On the basis of TOF values for the HYD of toluene, the monometallic Pt/βZ showed larger activity than the bimetallic Pt-PdH/βZ at short time on-stream, but this order was reversed under steady-state conditions. From FTIR of adsorbed CO and XPS measurements, the formation of the Pt–Pd alloy on this catalyst was excluded. The enhancement in activity observed for Pt-PdH/βZ as compared with Pt/βZ is related to the synergic effect of the two metals, which led to a lower deactivation and larger S-tolerance. On the other hand, the high activity of the βZ-as compared with SA-supported samples was attributed to the higher acidity of the former. The involvement of acid sites in activity was studied by comparing the performances of fresh and pyridine-neutralized Pt-PdH/βZ and Pt/βZ catalysts. For HYD of toluene, the value of TOFt=0 for the two zeolite catalysts was much lower on pyridine-neutralized samples, but still higher than on the non-neutralized Pt-PdL/SA and Pt-PdH/SA. It is proposed that Pt-Pd phases deposited on acidic βZ develop stronger activity, which does not change after neutralization.
Variation in noble metal morphology and its impact on functioning of hydrogen mitigation catalyst
Fuel and Energy Abstracts, 2011
Platinum Palladium SEM Hydrogen mitigation catalyst a b s t r a c t A large amount of hydrogen is generated in nuclear reactor during loss of coolant accident (LOCA) conditions. This can be a threat to containment integrity if flammable limit (4% in air) is crossed. Passive autocatalytic recombiner is one of the most feasible remedies for this. Here we report a new class of mixed noble metal catalysts prepared by modified methods, viz Pt, Pt þ Pd or Pt followed Pd on stainless steel wire gauze. These catalysts were characterised for noble metal loading, phase purity by XRD, morphology of surface by Scanning Electron Microscopy (SEM). They were then evaluated for their catalytic activity for H 2 eO 2 recombination reaction under static air condition and in presence of various poisons like carbon dioxide, methane, carbon monoxide and water. .in (S. Varma).
Tuning the activity of supported metal catalysts
2019
This research intends to explore strategies able to modify the activity of heterogeneous catalysts, in order to draw structure-activity relationships and gain an improved understanding of the catalytically active sites. Different approaches have been attempted, such as applying an activation treatment, modifying the metal loading, changing the support and adding organic ligands. These methods have been applied to supported noble metal nanoparticles of Pt, Pd and bimetallic AuPd, which have been previously found active for liquid-phase hydrogenation and oxidation reactions such as the reduction of nitro compounds and the oxidation of alcohols. Several characterisation methods were applied to study the structure and properties of these materials. First, a Pt/TiO2 catalyst for the selective hydrogenation of 3-nitrostyrene has been developed by optimising the effect of the variation of metal loading and heat treatment. In particular, a series of catalysts were prepared, tested and chara...
Iranian Journal of Chemical Engineering, 2021
In the presented research, the selective hydrogenation of benzene in a mixture of benzene and normal heptane (5 vol % of benzene) over different kinds of heterogeneous catalysts was investigated. For this purpose, a series of catalysts with various supports such as Pd/ZSM-5, Pd/13X, and Pd/ was developed. To prepare Pd-supported catalysts, the modification of supports was conducted by a specified amount of palladium nitrate in the aqueous solution. Experimental catalyst evaluation tests were performed in the catalyst assessment setup. The characterizations of the physicochemical properties of the prepared catalysts were performed by XRD, NH₃-TPD, and BET. It can be found that the conversion of benzene was promoted under the optimized reaction conditions of 200 °C, 1 MPa, H2/HC = 1.3 (molar ratio), and the weight hourly space velocity (WHSV) = 25 hr-1. Among these catalysts, Pd/13X exhibited the maximum conversion of benzene (90 %) and the minimum light-cut production under the optimum conditions. The study on the stability of catalysts shows that the decline activity of the Pd/13X catalyst is more than that of the other catalysts (from 90 % to 81 %) in the specified 20 h time on stream, but so far the activity of this catalyst is the highest in comparison with that of other catalysts at the end of the defined time (20 h).
Hydrogenation of Aromatics in Diesel Fuels on Pt/MCM-41 Catalysts
Journal of Catalysis, 1997
The hydrogenation activity of Pt supported on two mesoporous MCM-41 samples differing in their chemical composition has been studied by following the kinetics of the hydrogenation of naphthalene at 225-275 • C reaction temperature and 5.0 MPa total pressure and by comparing the kinetic parameters obtained with Pt supported on a mesoporous amorphous silica-alumina (MSA) and other conventional supports, such as commercial amorphous silicaalumina (ASA), zeolite USY, γ-alumina, and silica. The two mesoporous MCM-41 and MSA materials having very high surface areas allowed for a better dispersion of the Pt particles, and they showed a superior overall hydrogenation activity as compared to the other supports. However, Pt/USY displayed the highest turnover (activity per exposed surface Pt), owing to the interaction of small Pt aggregates in the supercage of the zeolite with the strong Brönsted acid sites associated to framework aluminum forming electrondeficient Pt species of known enhanced activity. Moreover, both the Al-MCM-41 and USY-based catalysts presented the highest sulfur tolerance during the hydrogenation of a naphthalene feed containing 200 ppm sulfur added as dibenzothiophene. The high metal dispersion and the interaction of the small Pt clusters with the mildly acidic sites present in Al-MCM-41 may account for its high sulfur tolerance. The superior hydrogenation activity and sulfur tolerance of Pt-MCM-41 catalyst observed in the naphthalene experiments were further confirmed during the hydrogenation of a hydrotreated light cycle oil (LCO) feed containing ca 70 wt% aromatics and 400 ppm sulfur.
Catalysis Letters, 2000
The reactivity of different organic compounds (naphthalene, alkylnaphthalenes, decalins, tetralin and their mixtures) and the roles of the support acidity and of the noble metals were studied in Pd/Pt on MCM-41 (with different Si/Al ratios) catalysts. The catalytic tests showed that the hydrogenolysis/ring-opening reactions mainly occurred on saturated compounds, while cracking took places mainly on unsaturated compounds. The presence of alkyl side chains on the polyaromatic ring inhibited the hydrodearomatization activity, proportionally to their length and number. Mixtures of naphthalene and methylnaphthalenes gave rise to a competition between the substrates, with a decrease in both hydrogenation and hydrogenolysis/ring-opening activities. Increasing support acidity favoured hydrogenolysis/ring-opening and cracking reactions, smoothing the hydrogenation activity. Noble metals are shown to be necessary not only in hydrogenation, but also in hydrogenolysis/ring-opening reactions.
Influence of support and supported phases on catalytic functionalities of hydrotreating catalysts
Fuel, 2014
were prepared. The HDS activity in DBT conversion was in the order: NiMo P NiW > CoMo on alumina. Al 2 O 3 -zeolite support was the most active in HDS of DBT. The most active catalyst in HDS of DBT was NiMo supported on Al 2 O 3 -zeolite. a b s t r a c t Different mixed-oxide supports were synthesized using homogeneous co-precipitation methods. Alumina-silica, alumina-titania, and alumina-zeolite supports were prepared and then impregnated with Mo (or W) and Co (or Ni) in order to evaluate their behavior in the dibenzothiophene hydrodesulfurization. Supports and supported catalysts were characterized by atomic absorption and textural properties. The conversion of model compounds (tetralin, 1-methylnaphthalene, and decalin) was investigated with the aim of understanding ring opening reaction over the support in presence of hydrogen. The model test reactions for support as well supported sulfide catalysts were carried out in a batch reactor at 4 MPa and 340°C. Conversion of cyclo-compounds showed that decalin had the highest conversion followed by 1-methylnaphthalene and tetralin when using a silica-alumina supported catalyst. The hydrodesulfurization results as a function of support variation indicated that high acidity of support has positive effect on the hydrogenolysis of CAS bond breaking. Thus, it is inferred that a balance between metal sites of hydrogenation and cracking of the support is critical in order to synthesize a bifunctional catalyst for deep hydrodesulfurization where sulfur removal as well as cetane improvement are mandatory.