Solubility of hydrogen in small particles of palladium

Boudart, M.; Hwang, Hongsun

doi:10.1016/0021-9517(75)90280-8

Cited by 243 publications

(81 citation statements)

References 8 publications

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“…It is believed that α-and β-Pd _ hydride species are formed during hydrogenation and that β sites promote alkane selectivity due to mainly higher amount of hydrogen dissolved within the particles 47), 48) . However, it has been shown that for very small particles, _ β-Pd hydride phase is rarely formed 49), 50) , hence a dramatic size reduction in the case of nanocluster Pd/ C catalyst could lead to the enhanced selectivity to the olefinic diol. The increased effect of steric hindrance (geometric effect) due to the stabilizer in the case of the protected Pd nanoparticles also contributes to the higher selectivity to the olefinic diol 39) .…”

Section: Palladium Nano Catalystsmentioning

confidence: 99%

Catalytic Hydrogenation of 2-Butyne-1,4-diol: Activity, Selectivity and Kinetics Studies

Rode

2008

J. Jpn. Petrol. Inst.

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The reaction pathway for hydrogenation of 2-butyne-1,4-diol involves parallel and consecutive isomerization as well as hydrogenation reactions forming other side products along with cis-2-butene-1,4-diol and butane-1,4-diol. Hence, achieving the highest selectivity to butene-and/or butanediol is critical from industrial point of view. Hydrogenation of butynediol is also of fundamental significance, due to its adsorption characteristics leading to the formation of active species and their role in determining the product distribution. Studies on designing various catalyst systems including colloidal as well supported palladium nanoparticles for the hydrogenation of butynediol, role of additives, catalyst pretreatment, kinetic studies carried out in our group has been presented in this review. Interestingly, almost complete selectivity to the intermediate olefinic diol was achieved with 1％ Pd/CaCO3 _ NH3 catalyst system. This could be due to the competitive adsorption of ammonia on the palladium surface along with the substrate 2-butyne-1,4-diol. Studies on catalyst pretreatment and kinetics using palladium catalyst have also been presented here. Nanostructure palladium both colloidal as well as supported catalysts showed a very high catalytic activity (10-40 times more) in the hydrogenation 2-butyne-1,4-diol to cis-2-butene-1,4-diol compared with the corresponding conventional Pd catalysts. For platinum based catalysts, formation of side products was completely eliminated in the hydrogenation of butyne diol. The increase in the basic strength of alkali metal doped Pt catalysts measured by CO2-TPD, led to the increase in electron density of Pt hence, faster desorption and higher selectivity to butenediol. In the case of continuous hydrogenation, the selectivity pattern was completely different from that found in the case of batch slurry reactor and by varying the contact time, the selectivity to both butene-and butanediols could be varied over a wide range of conditions.

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Section: Palladium Nano Catalystsmentioning

confidence: 99%

Catalytic Hydrogenation of 2-Butyne-1,4-diol: Activity, Selectivity and Kinetics Studies

Rode

2008

J. Jpn. Petrol. Inst.

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“…Pd-hydride formation has been the subject of many studies [14], [15], [16], [17], [18], [19], [20] and [21] and also may occur during catalytic reactions [10] and [22]. Because Pd catalysts are used in many reactions involving hydrogen (e.g., hydrogenation of CO [23], [24], [25], [26] and [27] and of CO 2 [28], [29], [30] and [31], methanol synthesis [27], [28] and [31]), the presence of Pd hydrides may have a pronounced effect on catalyst performance [10] and [22].…”

Section: Introductionmentioning

confidence: 99%

Hydride formation and stability on a Pd–SiO2 thin-film model catalyst studied by TEM and SAED

Jenewein¹,

Penner²,

Gabasch³

et al. 2006

Journal of Catalysis

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Hydride formation was studied on Pd particles supported on SiO 2 , and the results were evaluated with reference to a corresponding ZnO-promoted Pd/SiO 2 catalyst reported recently. Pd particles (mean size, ~5 nm) were epitaxially grown on NaCl(001) cleavage faces and subsequently covered by a layer of amorphous SiO 2 , thereby maintaining their epitaxial orientation. The films were subjected to various hydrogen and annealing treatments in the temperature regime of 373-873 K, and their stability in an O 2 environment (373-573 K) was also tested. The structural and morphological changes were followed by transmission electron microscopy and selected area electron diffraction. Reduction at 523 K increased the mean particle size considerably and converted the Pd particles into an amorphous hydride phase that decomposed at and above 673 K either by reduction in hydrogen or by annealing in He environment, forming a crystalline Pd 2 Si phase. Oxidative treatments of the Pd-H phase at temperatures above 523 K induce transformation into partially oriented Pd particles. The Pd 2 Si phase was stable under reductive conditions up to 873 K and decomposed into disoriented Pd particles on oxidation at temperatures at and above 573 K. Although the Pd/SiO 2 catalyst can be readily converted into an amorphous hydride phase, it loses its hydrogen storage capability on entering the silicide state at 673 K, and hence no hydride formation was observed. These results are in contrast to previous observations on a corresponding Pd/ZnO/SiO 2 catalyst, where the formation of a well-ordered PdZn alloy prevented the formation of the hydride phase and significantly enhanced the structural stability of the catalyst and its resistance against sintering. In contrast, the Pd/SiO 2 system was converted into the amorphous hydride state under "real" catalytic conditions, for example, during CO 2 hydrogenation at around 523 K.

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“…Simultaneously, the addition of gold to palladium increases the stability of the hydride phase, so the decomposition of this phase occurs at higher temperature. On the other hand, the stability of the hydride phase formed by small crystallites is much lower than the stability of this phase formed by large crystallites which results in shifting of the maximum TPHD profile towards lower temperatures [18,23]. Fig.…”

Section: Resultsmentioning

confidence: 97%

“…Based on the literature data and our earlier experience concerning the formation and decomposition of β-PdH phase [15,[18][19][20][21][22][23][24], the position, shape (width, distortion), and intensity of a TPHD peak depend on different variables, among which Pd dispersion, type of support, and modifying additives play a dominant role. The introduction of gold to the palladium lattice brings about a more-or-less serious decrease in hydrogen dissolution (i.e., a lower H/Pd ratio in respective hydride phase).…”

Section: Resultsmentioning

confidence: 99%

Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

Bonarowska

Zieliński

Matus

et al. 2018

Reac Kinet Mech Cat

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This work investigates the influence of activation by microwave irradiation on the catalytic properties of Pd-Au/C Sibunit catalysts in the hydrodechlorination of CCl 4 . Pd and Pd-Au samples were thoroughly characterized by CO chemisorption, X-ray diffraction, TPHD and STEM, and used in gas phase hydrodechlorination of tetrachloromethane. The studies showed that homogenous Pd-Au alloys are formed more efficiently if short-time microwave activation is applied instead of conventional activation by H 2 reduction at 380°C. These catalysts show higher activity, stability and higher selectivity towards the desired products (C1-C5 hydrocarbons) than the catalysts activated by conventional reduction in 10%H 2 /Ar flow.

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Solubility of hydrogen in small particles of palladium

Cited by 243 publications

References 8 publications

Catalytic Hydrogenation of 2-Butyne-1,4-diol: Activity, Selectivity and Kinetics Studies

Catalytic Hydrogenation of 2-Butyne-1,4-diol: Activity, Selectivity and Kinetics Studies

Hydride formation and stability on a Pd–SiO2 thin-film model catalyst studied by TEM and SAED

Influence of microwave activation on the catalytic behavior of Pd-Au/C catalysts employed in the hydrodechlorination of tetrachloromethane

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