Papers by Zbigniew Karpiński
Journal of Catalysis, 1989
In Part I of this series (W. Juszczyk et al., in Proceedings, 9th International Congress on Catal... more In Part I of this series (W. Juszczyk et al., in Proceedings, 9th International Congress on Catalysis, Calgary, 1988 (M.J. Phillips and M. Ternan, Eds.), Vol. 3, p. 1238. The Chemical Institute of Canada, Ottawa, 1988) using the catalytic conversion of neopentane as a virtually noncoking probe, the authors found that after reduction at moderate temperatures (573-773 K), Pd/AlâOâ is
Recent studies of trust and cooperation in social dilemma situations focus on explaining how soci... more Recent studies of trust and cooperation in social dilemma situations focus on explaining how social identity processes - triggered by differentiation based on a nominal characteristic – affect cooperative behaviors among strangers. Few studies, however, predict and explain whether and how much cooperation occurs among strangers who vary by characteristics that have status value attached - i.e., characteristics that cause actors possessing one state of a given characteristic to be perceived as more worthy than actors possessing another state of that same characteristic. Even studies that incorporate the status hierarchies’ effects into social dilemma models focus on groups’ effectiveness in producing collective goods, rather than on the simplest trust-game type interactions. This might be defensible insofar as game theory predicts that status differences will have no effect on cooperation among strangers. Our paper takes a different approach: Using status characteristics theory, we p...
Journal of the Chemical Society, Faraday Transactions, 1997
ABSTRACT
During an initial stage of the reaction of CCl2F2 with hydrogen on alumina-supported Pd and Pd-Au... more During an initial stage of the reaction of CCl2F2 with hydrogen on alumina-supported Pd and Pd-Au catalysts, an extensive defluorination occurs. However, at steady state, this undesired defluorination is greatly reduced; CH4 and CH2F2 constitute the only major reaction products. A temperature programmed hydrogen treatment study shows retention of fluorine (and carbon) in used catalysts.
Studies in Surface Science and Catalysis, 2000
ABSTRACT
Applied Catalysis B: Environmental, 2015
ABSTRACT Catalytic gas-phase hydrodechlorination (HdCl) of tetrachloromethane was investigated ov... more ABSTRACT Catalytic gas-phase hydrodechlorination (HdCl) of tetrachloromethane was investigated over Au/Sibunit and Pd/Sibunit carbon prepared by impregnation, and Pd-Au/Sibunit carbon prepared by either reductive deposition of Au onto Pd or successive impregnation of Pd/Sibunit carbon with a solution of gold salt carried out at aerobic conditions. The activated (by reduction in H2 at 400 °C) catalysts were characterized in terms of H2 and CO chemisorptions, XRD and (S)TEM-EDS measurements. Presence of smaller (<2 nm) metal particles in 2.8 wt.% Pd/Sibunit (dmean 3.1 nm) evidenced by TEM was not confirmed by XRD and gas chemisorptions. XRD and (S)(TEM)-EDS showed a reasonable quality of Pd-Au alloying in catalysts prepared by reductive deposition. Compared with the monometallic palladium, active carbon-supported bimetallic Pd-Au catalysts (∼0.24 g charges) showed very good activity (conversions up to 92%), resistance to deactivation during ∼70 h runs and high selectivity to nonchlorinated products (up to ∼80%) in the reaction of hydrodechlorination of tetrachloromethane, carried out at 90 °C. However, their behavior greatly depends on the quality of Pd-Au alloying: well mixed Pd-Au particles of Pd-Au maintain a very good catalyst performance, while the increasing presence of small unalloyed Pd particles leads to rapid deactivation. A large part of these small Pd particles can be leached out from such insufficiently homogenized catalystsby dissolution in 10% nitric acid. This treatment, followed by catalyst re-reduction results in the remarkable improvement of catalytic performance, especially the catalyst's stability in a long-term operation. During the reaction, carbon species originating from CCl4 enter palladium (but not PdAu) bulk, leading to the formation of the palladium carbide phase, PdCx, which seems to be less effective in hydrogen activation, and results in massive accumulation of nonreactive deposits containing both carbonaceous as well as chlorine species leading to rapid catalyst deactivation.
Solid State Phenomena, 2007
Abstract. Multi-wall carbon nanotubes (MWCNTs) were used as a support for the deposition of highl... more Abstract. Multi-wall carbon nanotubes (MWCNTs) were used as a support for the deposition of highly dispersed platinum. After characterization by several physical techniques, the catalyst was studied in reactions for: hydrodechlorination of carbon tetrachloride and the ...
ChemInform, 2010
ABSTRACT Heterogeneous photocatalysis offer many possibilities for finding appropiate environment... more ABSTRACT Heterogeneous photocatalysis offer many possibilities for finding appropiate environmentally friendly solutions for many of the the problems affecting our society (i.e., energy issues). Researchers are still looking for novel routes to prepare solid photocatalysts able to transform solar into chemical energy more efficiently. In many developing countries, biomass is a major energy source, but currently such countries lack of the technology to sustainably obtain chemicals and/or fuels from it. The Roadmap for Biomass Technologies, authored by 26 leading experts from academia, industry, and government agencies, has predicted a gradual shift back to a carbohydrate-based economy. Biomass and biofuels appear to hold the key to satisfy the basic needs of our societies for the sustainable production of liquid fuels and high value-added chemicals without compromising the scenario of future generations. In this review, we aim to discuss various design routes for nanostructured photocatalytic solid materials in view of their applications in the selective transformation of lignocellulosic biomass to high value-added chemicals.
Topics in Catalysis, 2009
... 20. Cavalli L, Pasquale A, Rossi M, Rubini C (2003) US Patent 6,627,777 B2, 30 Sept 2003 21. ... more ... 20. Cavalli L, Pasquale A, Rossi M, Rubini C (2003) US Patent 6,627,777 B2, 30 Sept 2003 21. Holbrook MT, Myers JD (2007) US Patent 2007/0225530 A1, 27 Sept 2007 22. Cao YC, Jiang XZ (2005) J Mol Catal A 242:119 23. Balakrishnan K, Sachdev A, Schwank J (1990) J ...
Reactive and Functional Polymers, 2009
Reaction Kinetics and Catalysis Letters, 1988
H2 pressure influences in different ways the reaction rates of neopentane conversion over Pd/SiO2... more H2 pressure influences in different ways the reaction rates of neopentane conversion over Pd/SiO2 and Pt/SiO2 catalysts. It seems that on Pt/SiO2 both isomerization and hydrogenolysis involve a common surface intermediate (probably an adalkyl), whereas on Pd/SiO2 the hydrogenolysis goes via more dehydrogenated species than those involved in isomerization.
Reaction Kinetics and Catalysis Letters, 1999
Active carbon-and MgF2-supported ruthenium catalysts characterized by a comparable metal dispersi... more Active carbon-and MgF2-supported ruthenium catalysts characterized by a comparable metal dispersion were investigated in CCl2F2 hydrodechlorination. Ruthenium, especially when supported on carbon, exhibits a considerable selectivity to CHClF2. This propensity and a noticeable activity towards C2-products differentiate ruthenium from palladium catalysts.
Materials, 2009
Heterogeneous photocatalysis offer many possibilities for finding appropiate environmentally frie... more Heterogeneous photocatalysis offer many possibilities for finding appropiate environmentally friendly solutions for many of the the problems affecting our society (i.e., energy issues). Researchers are still looking for novel routes to prepare solid photocatalysts able to transform solar into chemical energy more efficiently. In many developing countries, biomass is a major energy source, but currently such countries lack of the technology to sustainably obtain chemicals and/or fuels from it. The Roadmap for Biomass Technologies, authored by 26 leading experts from academia, industry, and government agencies, has predicted a gradual shift back to a carbohydrate-based economy. Biomass and biofuels appear to hold the key to satisfy the basic needs of our societies for the sustainable production of liquid fuels and high value-added chemicals without compromising the scenario of future generations. In this review, we aim to discuss various
Journal of Molecular Catalysis A: Chemical, 2004
A comparative study of hydrodechlorination of dichlorodifluoromethane, carbon tetrachloride and 1... more A comparative study of hydrodechlorination of dichlorodifluoromethane, carbon tetrachloride and 1,2-dichloroethane over aluminasupported Pt catalysts showed several interesting features in the catalytic behavior. Platinum proved to be very good catalyst in CCl 4 hydrodechlorination (with high selectivity toward CHCl 3 ), whereas for CCl 2 F 2 and 1,2-dichloroethane hydrodechlorinations this metal exhibits rather low activity and, in addition, converts the reactants to less valuable products (e.g. alkanes). However, a rapid deactivation of Pt catalysts during hydrodechlorination requires their frequent regeneration. Two regeneration protocols tested in this work showed interesting, albeit somewhat different, activity evolutions. Removal of chlorine species by hydrogen at 350 • C led to a moderate increase of catalytic activity. On the other hand, a partial removal of carbonaceous residues by oxidative pretreatment brought about a considerable increase of the overall conversion level in CCl 4 hydrodechlorination. Additional temperature-programmed experiments with spent and regenerated Pt/Al 2 O 3 catalyst suggest that a partial removal of carbonaceous deposit (most probably followed by its reconstruction) leading to the formation of very active catalyst, less susceptible to poisoning by chlorine.
Journal of Molecular Catalysis A: Chemical, 2002
The kinetics of ethane hydrogenolysis over cobalt catalysts supported on silica has been investig... more The kinetics of ethane hydrogenolysis over cobalt catalysts supported on silica has been investigated. The results compare well with previous data from Sinfelt et al., Haddad and Goodwin, and Babernics et al. The data were found to be characterized by an isokinetic temperature, T iso = 490 ± 40 K and it was therefore possible to apply the model of selective energy transfer (SET). This approach indicates that either there is an energy transfer from the catalyst by full resonance to a vibration mode of the reactant with ν = 680 cm −1 corresponding to a metal (M)=CH 2 bond, or there is an energy transfer to an M-CH 3 vibration mode in the region of 400 cm −1 , most likely at 355 cm −1 . In any case, these interpretations indicate that it is the breaking of one or two metal-carbon bonds that determine the reaction, not the cleavage of the carbon-carbon bond of ethane. This is in agreement with recent views of Sinfelt.
Journal of Catalysis, 2003
This work provides evidence that reduction of Pd/SiO 2 catalysts in dihydrogen at temperatures as... more This work provides evidence that reduction of Pd/SiO 2 catalysts in dihydrogen at temperatures as low as 450 and 500 • C may already lead to a considerable interaction between palladium and silica, identified by the formation of palladium silicides (Pd 4 Si and Pd 3 Si). This result seems significant in view of the frequent usage of this temperature level in activation and pretreatment of Pd/SiO 2 catalysts. Application of a high flow of a reducing gas mixture and different reduction time periods indicates that an efficient removal of water vapor from the catalyst zone during hydrogen pretreatment facilitates reduction of silica to silicon, which, in turn, interacts with nearby palladium species. Silation of palladium in Pd/SiO 2 catalysts during a prolonged reduction at 450 and 500 • C has a considerable effect on the catalytic properties in the reaction of 2,2-dimethylbutane with dihydrogen. Incorporation of silicon into palladium lowers the catalytic activity, decreases the activation energy, increases the selectivity toward isomerization (at the expense of hydrogenolysis), and also changes the type of 2,2-dimethylbutane interaction with the surface of catalyst (from αγ to αγ mode).
Journal of Catalysis, 2004
The effect of catalyst pretreatment on the performance of chlorine-free γ -alumina-supported pall... more The effect of catalyst pretreatment on the performance of chlorine-free γ -alumina-supported palladium catalysts with metal loadings in the range of 0.3 to 2.77 wt% has been investigated in the hydroconversion of n-hexane (nH) and 2,2-dimethylbutane (22DMB) at 290 • C and atmospheric pressure. The catalyst properties were modified by varying the catalyst pretreatment: low-temperature reduction (LTR) at 300 • C; high-temperature reduction (HTR) at 600 • C; and oxidation of highly reduced catalysts followed by LTR (regeneration). The isomerization activity for both nH and 22DMB conversion is enhanced by HTR of the Pd/Al 2 O 3 as compared to LTR and regeneration. It is concluded that HTR increases the Lewis acidity of the alumina and the participation of Lewis acid sites improves catalytic performance. The influence of Lewis acid catalyst sites on the macroscopic kinetics overshadows the modest catalytic contribution from palladium. Ammonia effectively blocks the acid centers and limits the overall catalytic performance to metal-only catalysis. The role of support acid sites in the conversion of C 6 -hydrocarbons was further demonstrated by isomerization activity associated with 22DMB hydroconversion catalyzed by an alumina-supported Ni catalyst. Based on the results of FTIR studies of adsorbed CO and results of temperature-programmed palladium hydride phase decomposition (TPHD), it was concluded that a part of the alumina-supported Pd transforms into a Pd-Al alloy during the HTR pretreatment. The catalytic performance of the regenerated catalysts in the C 6 -alkane conversion is consistent with the suggestion that the Pd-Al alloy formed during HTR decomposes during the regeneration treatment to form Al 2 O 3 moieties on the Pd surface. These moieties, most likely, interact strongly with nearby palladium species, creating sites which are active for alkane isomerization and, simultaneously, resistant to coking. .pl (Z. Karpiński). ple, when Pd/Al 2 O 3 is prereduced at 600 • C, the overall activity increases and the isomerization selectivity is enhanced to 95% for the hydroconversion of C 6 -alkanes at reaction temperatures less than 300 • C in comparison with catalysts prereduced at temperatures less than 400 • C [3-5]. The enhanced isomerization selectivity was attributed to an increase in the Lewis acidity of the γ -alumina that results from the high-temperature pretreatment . Confirmation
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Papers by Zbigniew Karpiński