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1

Wyznaczenie kinetyki estryfikacji kwasu laurynowego n-heksanolem, n-oktanolem i n-dekanolem w obecności żywicy jonowymiennej Dowex 50WX8 jako katalizatora

Hamryszak Łukasz

Przemysł Chemiczny

|

2024

|

T. 103, nr 1

66--72

PL

Przeprowadzono badania kinetyczne procesu estryfikacji kwasu laurynowego n-heksanolem, n-oktanolem, n-dekanolem w zakresie temp. 393-413 K i dla stosunków molowych alkohol:kwas 3:1-10:1 z udziałem katalizatora heterogenicznego Dowex 50WX8 (1,5% mas.). Badania prowadzono w warunkach izotermicznych w doświadczalnym reaktorze półokresowym z ciągłym wyprowadzaniem wody. Stwierdzono, że reakcje można opisać za pomocą równania kinetycznego typu Langmuira i Hinshelwooda z reakcją powierzchniową pomiędzy kwasem laurynowym i alkoholem jako etapem limitującym. Określono parametry równania kinetycznego, wartości energii aktywacji malały w zakresie 62-54 kJ/mol w szeregu n-heksanol > n-oktanol > n-dekanol.

EN

CH₃(CH₂)₁₀COOH was esterified with CH₃(CH₂)₅OH, CH₃(CH₂)₇OH and CH₃(CH₂)₉OH at 393-413 K and at molar ratios (alc.:acid) of 3:1-10:1 in the presence of the Dowex catalyst 50WX8 (1.5% by mass). The kinetics of the studied processes were described by the detd. LangmuirHinshewood type kinetic equation, the limiting step of which was the surface reaction of CH₃(CH₂)₁₀COOH with alcohol. The activation energy decreased in the range of 62-54 kJ/mol in the alcohol series: n-hexanol > n-octanol > n-decanol.

2

Wpływ temperatury i stężenia wodoru na aktywność i selektywność wybranych katalizatorów heterogenicznych zawierających metale szlachetne w procesie uwodornienia metyloacetylenu i propadienu

Kacprzak Krzysztof, Lewera Adam

Przemysł Chemiczny

|

2023

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T. 102, nr 7

700--706

PL

Katalizatory Pd/Al₂O₃, Pd/TiO₂ i Pt/Al₂O₃ otrzymano metodą impregnacji-redukcji i zastosowano do zbadania wpływu nadmiaru wodoru i temperatury prowadzenia procesu na selektywność i aktywność w procesie selektywnego uwodornienia metyloacetylenu i propadienu zawartych we frakcji węglowodorów C₃ z krakingu parowego. Katalizatory zawierające pallad wykazywały wyższą aktywność i selektywność niż Pt/Al₂O₃, ale w obecności nadmiaru wodoru w większym stopniu następował spadek ich selektywności. W niskich temperaturach, w obecności katalizatora Pd/TiO₂ obserwowano większy przyrost propylenu i większe stężenie pozostałego metyloacetylenu i propadienu, a w warunkach zwiększonego stężenia wodoru i w umiarkowanych temperaturach charakteryzował się on wyższą aktywnością (i niewielkim spadkiem selektywności), co czyni z niego interesującą alternatywę dla powszechnie stosowanych w tym procesie katalizatorów Pd/Al₂O₃.

EN

The Pd/Al₂O₃, Pd/TiO₂ and Pt/Al₂O₃ catalysts obtained by the impregnation-redn. method were used for selective hydrogenation of MeC≡CH and CH₂=C=CH₂ (contained in the C₃ fraction stream from the steam cracking process) to MeCH=CH₂. Pd-contg. catalysts showed higher activity and selectivity than Pt/Al₂O₃, but the excess of H₂ caused a decrease in their selectivity to a greater extent. In the presence of Pd/TiO₂, a greater increase in the MeCH=CH₂ content was obsd. than in Pd/Al₂O₃ at low temps., but at the same time higher concns. of residual MeC≡CH and CH₂=C=CH₂ were obsd. Under conditions of increased H₂ concn. and moderate temps., the Pd/TiO₂ catalyst showed higher activity (and a slight decrease in selectivity), which makes it an interesting alternative to the Pd/Al₂O₃ catalysts commonly used in the process.

3

Catalyst regeneration techniques in naphtha reforming: Short review

Gupta Aviral, Gupta S. K.

Chemical and Process Engineering

|

2022

|

Vol. 43, nr 2

101–-108

EN

Catalytic reforming is an important intermediate in the processing of crude (naphtha in particular) to obtain gasoline. The catalyst used in the process (platinum) is quite expensive and may negatively impact the business if not used judiciously. The aforesaid not only refers to the reduction in loss of the catalyst per unit of gasoline produced but also to the manufacturing of an environmentally friendlier product alongside which is the need of the planet and also a necessity to meet the increasingly strict government norms. In order to meet the above requirements, various refineries around the world use various well-known conventional methods which depend on the quality and quantity of crude manufactured by them. This paper focuses on highlighting recent advancements in methods of catalytic regeneration (CR) in the reforming unit of petroleum industries to produce high octane gasoline, without any major replacements in their existing setup. Research papers formulated by the application of methodologies involving non-linear models and real-time refinery data have only been considered to avoid any deviations/errors in practical applications. In-depth analysis of these papers has led to the origin of some ideas which have been included as suggestions and can be considered as subjects of further research. In all, the objective of the paper is to serve as a reference for researchers and engineers working on devising optimum methods to improve the regeneration of reforming catalysts.

4

Materiały funkcjonalne oparte na magnetycznych nanokapsułkach węglowych

Kasprzak Artur, Popławska Magdalena, Koszytkowska-Stawińska Mariola

Wiadomości Chemiczne

|

2021

|

[Z] 75, 11-12

1211--1233

EN

The chemistry of carbon nanomaterials attracts continuous attention of scientists because of their promising properties and applications. Carbon-encapsulated iron nanoparticles (CEINs) are subgroup of carbon nanomaterials. CEINs are the core-shell nanostructures including the metallic phase permanently encapsulated in a tight carbon coating. The carbon shell protects CEINs against oxidation of metal into a corresponding oxide, as well as prevents them from spontaneous aggregation. It has been documented that the magnetic properties of CEINs are superior in comparison with the respective materials comprising metal oxides. Additionally, the presence of the carbon shell enables surface functionalization of CEINs by means of various synthetic routes, both covalent and non-covalent ones. Chemical functionalization enables tuning the materials’ properties and applications, for example toward introducing catalytically active sites or improving colloidal stability. One may conclude that CEINs combine physicochemical properties of graphene and iron nanoparticle. Therefore, this is prospective material for many applications. In this article, we discuss the properties, chemistry and selected applications of CEINs.

5

Kataliza procesów hydrosililowania z udziałem cieczy jonowych

Bartlewicz Olga, Szymańska Anna, Jankowska-Wajda Magdalena, Dąbek Izabela, Maciejewski Hieronim

Wiadomości Chemiczne

|

2021

|

[Z] 75, 1-2

5--29

EN

Hydrosilylation is a fundamental and elegant method for the laboratory and industrial synthesis of organosilicon compounds. The hydrosilylation reaction is usually performed in a single-phase homogeneous system. A major problem, particularly in homogeneous catalysis, is the separation of catalyst from the reaction mixture. The presence of metals in the reaction products, even in trace quantities, is unacceptable for many applications, therefore efforts have been made at applying heterogeneous catalysts or immobilised metal complexes in order to obtain high catalytic activity and easy product isolation at the same time. One of the methods for producing such catalysts is the employment of ionic liquids as agents for the immobilization of metal complexes. Biphasic catalysis in a liquid-liquid system is an ideal approach through which to combine the advantages of both homogeneous and heterogeneous catalysis. The ionic liquids (ILs) generally form the phase in which the catalyst is dissolved and immobilized. In our research we have obtained a number of catalytic systems of such a type which were based on rhodium and platinum complexes dissolved in phosphonium, imidazolium, pyridinium and ammonium liquids. Currently, there has a common trend to obtain heterogenized systems that combine advantages of homogeneous and heterogeneous catalysis, which makes the hydrosilylation process more cost- effective. Such integration of homo- and heterogeneous catalysts is realized in several variants, as supported IL phase catalysts (SILPC) and solid catalysts with ILs layer (SCILL). Although all the above systems show high catalytic activities, their structure is unknown. This is why we have made attempts to modify selected ionic liquids (corresponding to our most effective systems) and we have applied them as ligands in the synthesis of platinum and rhodium complexes. Another group of catalysts comprises anionic complexes of rhodium and platinum which were obtained by reactions between halide complexes of metals and a respective ionic liquid. Most of the obtained complexes are solids insoluble in hydrosilylation reagents and are characterized by a high catalytic activity. A considerable development of heterogeneous catalysts of this type and their application in many hydrosilylation processes can be expected in the future. This mini-review briefly describes the recent progress in the design and development of catalysts based on the presence of ionic liquids and their applications for hydrosilylation processes.

6

Multipurpose usage of magnetic proppants during shale gas exploitation

Bogacki Jan, Zawadzki Jarosław

Ecological Chemistry and Engineering. S

|

2019

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Vol. 26, nr 1

37--44

EN

Magnetic material may be added to proppant, as the magnetic marker allows to determine the range and efficiency of hydraulic fracturing. However, magnetic proppant may be also used in flowback fluid treatment and monitoring of environmental pollution. As a result of shale gas hydraulic fracturing, large volume of flowback fluid is created. Flow back fluid have similar properties to fracturing fluid, but it is potentially enriched with large amount of salts and organic compounds leached from shale. Magnetic proppant may serve as a heterogeneous catalyst during organic pollutants decomposition. Additionally, in case of leakage and consequently the fracturing fluid pollution, magnetic proppant is placed into the soil environment. It can be detected using magnetometric methods. This article discusses the above-mentioned issues based on the knowledge and experience of the authors and the literature review.

7

Major advances and challenges in heterogeneous catalysis for environmental applications: A review

Wacławek S., Padil V. V. T., Černík M.

Ecological Chemistry and Engineering. S

|

2018

|

Vol. 25, nr 1

9--34

EN

Heterogeneous catalysis is one of the fastest developing branches of chemistry. Moreover, it is strongly connected to popular environment-related applications. Owing to the very fast changes in this field, for example, numerous discoveries in nanoscience and nanotechnologies, it is believed that an update of the literature on heterogeneous catalysis could be beneficial. This review not only covers the new developments of heterogeneous catalysis in environmental sciences but also touches its historical aspects. A short introduction to the mechanism of heterogeneous catalysis with a small section on advances in this field has also been elaborated. In the first part, recent innovations in the field of catalytic air, water, wastewater and soil treatment are presented, whereas in the second part, innovations in the use of heterogeneous catalysis for obtaining sustainable energy and chemicals are discussed. Catalytic processes are ubiquitous in all branches of chemistry and there are still many unsolved issues concerning them.

8

Montmorillonite as the catalyst in oxidation of limonene with hydrogen peroxide and in isomerization of limonene

Malko M., Antosik A. K., Wróblewska A., Czech Z., Wilpiszewska K., Miądlicki P., Michalkiewicz B.

Polish Journal of Chemical Technology

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2017

|

Vol. 19, nr 4

50--58

EN

In our studies montmorillonite (MMT) was used as the heterogeneous, natural catalyst. This material was previously prepared by bentonite purification with help of the sedimentation method. The obtained catalyst was characterized by: XRD, SEM, BET and EDX. Catalytic tests with montmorillonite as the catalyst were performed with the natural terpene – R-(+)-limonene. This compound was oxidized with hydrogen peroxide and, moreover, in the separate process it was also isomerized. As the main products of limonene oxidation were detected: (1,2-8,9)-diepoxide, perillyl alcohol, carvone, carveol, 1,2-epoxylimonene and 1,2-epoxylimonene diol. In the isomerization of R-(+)-limonene were formed: terpinenes, terpinolene and p-cymene. Conversions of limonene in these processes reached 70–80%. The application of montmorillonite (the natural of origin) in the studied processes (oxidation and isomerization) is environmentally friendly, it allows to reduce the cost of the studied processes. The resulting products of the processes of oxidation and isomerization of R-(+)-limonene have many applications.

9

Elementary steps in heterogeneous catalysis: The basis for environmental chemistry

Ertl G., Zielińska M., Rajfur M., Wacławek M.

Chemistry-Didactics-Ecology-Metrology

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2017

|

R. 22, NR 1-2

11--41

EN

Catalysis is an alternative way for reaching an immediate formation of a product, because of a lower energy barrier (between the molecules and the catalysts). Heterogeneous catalysis comprises the acceleration of a chemical reaction through interaction of the molecules involved with the surface of a solid. It is a discipline, which involves all the different aspects of chemistry: inorganic and analytical chemistry in order to characterize the catalysts and the forms of these catalysts. The industrial chemistry puts all these things together to understand the solid chemical handling, chemical reaction and energy engineering and the heat and mass transfer in these catalytic processes. Very often there are more than one, but several products, then the role of the catalyst is not so much related to activity, but to selectivity. The underlying elementary steps can now be investigated down to the atomic scale as will be illustrated mainly with two examples: the oxidation of carbon monoxide (car exhaust catalyst) and the synthesis of ammonia (the basis for nitrogen fertilizer). There is a huge market for the catalysts themselves despite of their high costs. A large fraction is used for petroleum refineries, automotive and industrial cleaning processes. The catalytic processes is a wide field and there are still many problems concerning energy conservation and energy transformation, so there is much to do in the future.

PL

Kataliza stała się obecnie alternatywnym sposobem na natychmiastowe tworzenie produktu chemicznego z uwagi na niższą barierę energetyczną (między cząsteczkami a katalizatorami). Kataliza heterogenna obejmuje przyspieszenie reakcji chemicznej poprzez oddziaływanie cząsteczek związanych z powierzchnią ciała stałego. Jest to dyscyplina, która obejmuje różne aspekty chemii: chemię nieorganiczną i analityczną w celu scharakteryzowania katalizatorów i form tych katalizatorów. Chemia przemysłowa następnie łączy te wszystkie zagadnienia razem, aby zrozumieć chemiczną manipulację ciał stałych, reakcję chemiczną i inżynierię energetyczną oraz przenoszenie ciepła i masy w tych procesach katalitycznych. Bardzo często tworzy się nie jeden, lecz kilka produktów, wtedy rola katalizatora nie jest tak bardzo związana z aktywnością, ale z selektywnością. Podstawowe etapy można teraz zbadać w skali atomowej, co będzie zilustrowane głównie dwoma przykładami: utlenianiem tlenku węgla (katalizator spalin samochodowych) i syntezą amoniaku (podstawa nawozu azotowego). Istnieje ogromny rynek katalizatorów pomimo wysokich ich kosztów. Duża ich część jest stosowana w samochodach, w rafineriach ropy naftowej i przemysłowych procesach czyszczenia. Procesy katalityczne stanowią szeroki obszar badań i nadal istnieją liczne problemy związane z oszczędzaniem i transformacją energii.

10

Praktyczne zagadnienia modelowania procesów chemicznych w porowatych ziarnach katalizatora

Boroń D., Bizon K., Tabiś B.

Przemysł Chemiczny

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2016

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T. 95, nr 5

1036--1041

PL

Przedstawiono praktyczne zagadnienia związane z ilościowym opisem procesów chemicznych przebiegających w ziarnach katalizatorów porowatych. Analizowano poprawność założeń przyjmowanych do matematycznego modelowania takich procesów i do obliczeń technologicznych. Dokonano oceny jednorodności pól stężeń i temperatury w katalizatorach porowatych na podstawie dwóch procesów egzotermicznych. Wykazanie jednorodności stężeń i temperatur w ziarnie kontaktu lub braku zewnętrznych oporów wnikania masy i ciepła umożliwia dobór odpowiednio uproszczonego modelu warstwy zarówno katalizatora stacjonarnego, jak i złoża fluidalnego.

EN

Changes of concns. and temps. in processes for exothermic hydrogenation of PhH and oxidn. of SO2, carried out on the catalyst pellets of (0.35–8.0) 10-3 m in diams. were computer simulated by using a heterogeneous model. The simulation results were used to verify the literature criteria enabling choice of a simplified math. model for a description of the processes.

11

Kataliza heterogeniczna w procesach utleniania cyklicznych ketonów do laktonów

Sitko M., Oleksy W., Chrobok A.

Przemysł Chemiczny

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2014

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T. 93, nr 5

722-727

PL

Przedstawiono doniesienia literaturowe dotyczące zastosowania heterogenicznych katalizatorów w reakcji Baeyera i Villigera utleniania cyklicznych ketonów do odpowiednich laktonów. Laktony znajdują szerokie zastosowanie w produkcji polimerów, farmaceutyków oraz herbicydów. Jednym z ważniejszych jest ε-kaprolakton wykorzystywany do produkcji biodegradowalnego polikaprolaktonu o stale wzrastającym znaczeniu. Przedstawiono przykłady zastosowania różnych czynników utleniających, takich jak nadkwasy organiczne, wodoronadtlenki alkilowe, tlen oraz nadtlenek wodoru w połączeniu z katalizatorami reakcji utleniania immobilizowanymi na różnych stałych nośnikach: zeolitach, krzemionce, minerałach oraz innych nośnikach o mniejszym znaczeniu aplikacyjnym. Szczególny nacisk położono na przedstawienie alternatywnych metod z udziałem nadtlenku wodoru, spełniających wymogi zielonej chemii.

EN

A review with 45 refs., of zeolites, silica and clays-supported heterogeneous catalysts used in Baeyer-Villiger oxidn. of cyclic ketones to lactones with org. peracids, alkyl hydroperoxides, O2 and H2O2.

12

Zastosowanie katalizatora heterogenicznego ZCu w procesie foto-Fentona

Świderska-Dąbrowska R., Schmidt R.

Gaz, Woda i Technika Sanitarna

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2014

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Nr 7

279--283

PL

W artykule przedstawiono wyniki badań utleniania fenolu w roztworze wodnym z zastosowaniem katalizatora heterogenicznego, zeolitu modyfikowanego jonami Cu(II) w układzie ZCu + H2O2 + UV. Badania wykazały, że efektywność utleniania fenolu jest wyższa w układzie heterogenicznym w porównaniu do homogenicznego. Przy zastosowaniu katalizatora heterogenicznego ZCu następuje utlenianie fenolu głównie do pirokatechiny i hydrochinonu, a ich stężenia po 60 minutach reakcji są prawie trzykrotnie większe w porównaniu do katalizy homogenicznej. Analiza uzyskanych wyników wskazuje na inny mechanizm utleniania przy zastosowaniu heterogenicznego katalizatora ZCu. Wyniki analiz chromatograficznych potwierdziły, że fenol utlenia się z całkowitym zniszczeniem struktury pierścieniowej do kwasu mrówkowego, który następnie utleniany jest do CO2 i H20.

EN

The paper presents results of research on phenol oxidation in the aąueous solution with application of heterogeneous catalyst, zeolite modified with Cu(II) ions in the ZCu + H2O2 + UV configuration. Results proved that phenol oxidation efficiency is higher in the heterogeneous configuration compared to homogeneous. During application of ZCu heterogeneous catalyst phenol is oxidized mostly to catechol and hydroquinone, and their concentrations, after 60 minutes of reaction time, are almost three times higher, in comparison with homogeneous catalysis. Analysis of obtained results shows different mechanism of oxidation with heterogeneous ZCu catalyst applied. Results of chromatographic analyses proved that phenol is oxidized with complete destruction of ring structure to formic acid, which is next oxidized to CO2 and H20.

13

Zastosowanie immobilizowanych cieczy jonowych w katalizie heterogenicznej

Strzelec K.

Przemysł Chemiczny

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2013

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T. 92, nr 9

1670-1673

PL

Przedstawiono aktualny przegląd wykorzystania organicznych i nieorganicznych nośników do immobilizacji cieczy jonowych oraz zastosowanie takich układów w katalizie heterogenicznej. Zaprezentowano najważniejsze aspekty związane z charakterystyką strukturalną, klasyfikacją, właściwościami i otrzymywaniem systemów katalitycznych opartych na heterogenizowanych cieczach jonowych, wraz z najnowszymi przykładami ich zastosowania w syntezie organicznej.

EN

A review, with 48 refs., of the use of org. and inorg. materials as supports for the immobilization of ionic liqs. and their catalytic application was given. Structural characteristics, classification, properties and preparation of supported ionic liqs. in catalytic systems were described. Same examples of their use in org. synthesis were presented.

14

Immobilizowane ciecze jonowe w "zielonej" katalizie heterogenicznej

Nowicki J., Muszyński M.

Przemysł Chemiczny

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2010

|

T. 89, nr 9

1241-1244

15

Kataliza heterogeniczna

Rachwalik R., Ogonowski J.

LAB Laboratoria, Aparatura, Badania

|

2010

|

R. 15, nr 2

19-26

16

Environmental heterogeneous catalysis and water purification by activated interfaces: a survey of different ways of surface activation and demonstration of a novel, simple and efficient procedure

Franzle S., Silbernagel H., Uchlier L., Liepelt G.

Ecological Chemistry and Engineering. S

|

2010

|

Vol. 17, nr 1

25-36

EN

Besides the established procedures, a multitude of environmental organic compounds can be mineralized or at least degraded to species like acetate by irradiating iron(III) complexes adsorbed to certain broad-gap semiconductors by visible light. Quantum yields are increased considerably by adsorption with respect to LMCT photochemistry in homogeneous solution, and the semiconductor acts as a electron- (rather, valence band hole) transfer agent which conserves the oxidizing properties of the ligand radical originally produced for longer periods of time (although modulated down to �Ăvb). The SC colloid particle, not excited itself, transports the hole, then allowing to oxidize co-adsorbed species present in small concentrations but also accumulated by adsorption. Water purification from various kinds of pollutants is feasible, and the reaction which is photocatalytic at turnovers . 100 referring to Fe complex can be kept up by air input into the suspension also tolerating repeated inputs of compounds to be removed. Except for some acetate formed, mineralization of substrates is complete.

PL

Poza ustalonymi procedurami wiele związków organicznych występujących w środowisku może być mineralizowanych lub, co najmniej degradowanych do np. octanów przez naświetlanieświatłem widzialnym kompleksów z żelazem(III), zaadsorbowanych na niektórych szerokopasmowych półprzewodnikach. Wydajność kwantowa znacznie wzrasta dzięki adsorpcji ze względu na fotochemię LMCT (Ligand-to-Metal Charge Transfer) w jednorodnym roztworze. Półprzewodnik działa jak przekaźnik elektronu (lub raczej dziury w paśmie przewodnictwa), który utrwala utleniające właściwości rodnikow ligandu, pierwotnie wytwarzanych w dłuższych okresach czasu. Koloidalna cząstka półprzewodnika, sama niewzbudzona, jest nośnikiem dziury i umożliwia utlenianie współabsorbowanych związków występujących w niewielkich stężeniach, a także zgromadzonych w wyniku adsorpcji. Oczyszczanie wody z różnego rodzaju zanieczyszczeń jest możliwe, a reakcja fotokatalityczna o wydajności < 100 w odniesieniu do kompleksu Fe może zachodzi. z udziałem powietrza wprowadzanego do zawiesiny, tolerując ponowne wprowadzenie związków, które mają być usunięte. Z wyjątkiem niektórych octanów mineralizacja substratu zachodzi całkowicie.

17

Auger Electron Spectroscopy for Materials Science: Examples of Applications

Pisarek M., Łukaszewski M., Janik-Czachor M.

Polish Journal of Chemistry

|

2009

|

Vol. 83, nr 8

1393-1412

EN

This paper summarizes the results of the investigations on selected topics from the field of materials science, such as: composition and stability of the passive films on metal alloys and the effect of electrochemical and chemical modifications on the catalytic activity and selectivity of Cu-based amorphous alloys as well as of Raney Ni catalysts doped with Cr. Microscopic and surface analytical techniques like scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) provide an in sight into the mechanism of the functionalization of the materials studied. The local chemical and morphological inhomogeneities at a micro- and nano-scale have been monitored. An attempt has been made to find an interrelation between the composition, structure and morphology of materials and their specific behavior in the processes considered.

18

Oxidation of cyclohexene catalyzed by Pt and Rh dispersed in a polymer matrix

Stochmal E., Sołtysek A., Nyczak A., Hasik M., Turek W., Korytkowska-Wałach A.

Polish Journal of Applied Chemistry

|

2009

|

Vol. 53, nr 3

247-252

EN

Polyanilinc (PANI)-Pt and polypyrrolc (PPy)-Rh compositcs obtained by chcmical reduction of Pt4' or Rh3* ions preformed in the prescncc of the polymers have been used as catalysts of eyclohexcnc oxidation by molecular oxygen under mild conditions. It has been found that PPy-Rh is more active than PANI-Pt in the first stage of the reaction resulting in 2-cyclohcxcnc-1-hydroperoxide. Differences in selectivity of the second stage of cyclohcxcnc oxidation yielding cyclohcxene epoxide, 2-cyclohexcnone and 2-cyclohexcnol over both catalysts have been also observed.

19

Reakcje i procesy katalityczne. Cz. I b

Sarbak Z.

LAB Laboratoria, Aparatura, Badania

|

2009

|

R. 14, nr 5/6

12-16

20

Układy bimetaliczne Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag i Pt-Au jako katalizatory heterogeniczne reakcji z udziałem wodoru

Matczak P.

Wiadomości Chemiczne

|

2008

|

[Z] 62, 7-8

683-708

EN

Heterogeneous catalysts play an important role in the manufacture of various chemical substances in large-scale processes, e.g. crude oil processing and organic synthesis [1]. Heterogeneous catalyst most often consists of a transition metal arranged on an oxide support [2]. The transition metal employed is usually one from Group 10 of the Periodic Table (Ni, Pd or Pt). The Group 10 metals are efficient catalysts of reactions with hydrogen. Such reactions occur in the above-mentioned crude oil processing and organic synthesis. In large-scale applications some modifications of the catalyst properties are often necessary to increase the rate of an appropriate stage of catalyzed reaction and to avoid by-products. The change of the catalytic properties can be obtained by incorporating another metal into the catalyst. Heterogeneous catalysts in which the active part contains two metals are called bimetallic catalysts or, more generally, bimetallic systems [3, 4]. Research on bimetallic catalysts was initiated in the 1960s and since then these catalysts have become an object of increasingly in-depth investigations [5]. The aim of this review is to summarize the available knowledge on heterogeneous bimetallic catalysts. The review has been narrowed only to a few combinations of metals, i.e. Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag, and Pt-Au. In the first part of the review some general information on the forms of the bimetallic systems is presented. The term bimetallic system itself is quite broad and includes, among other, the following representatives (Fig. 1): alloys, surface alloys, monometallic monolayer or pseudomorphic overlayers arranged on the surface of the other metal, monometallic nanoparticles and clusters arranged on the surface of the other metal, alloyed nanoparticles and clusters, core/shell nanoparticles and clusters, and heteroaggregates. Recently, the last three of these representatives have been in the centre of interest [5, 6]. They offer properties very different from those characteristic of bulk materials [15]. Later, the methods of synthesis and structural characterization of the bimetallic systems are described. At present, the preparation of the bimetallic catalysts that exhibit an appropriate structure is difficult and expensive. Hence, further progress in this field is still required. Some new methods of preparation [7, 16-41], as well as many experimental [42-45, 48-67] and theoretical papers [69-77] on structural, energetic and electronic properties of the bimetallic systems are reviewed. In the last part of the review the catalytic behaviour of the Pd-Ag, Pd-Pt, Pd-Au, Pt-Ag and Pt-Au systems is discussed in detail. The discussion concentrates on the catalytic reactions with hydrogen, e.g. hydrogenation, dehydrogenation, hydrogenolysis, etc. [106-137]. In such reactions the bimetallic catalysts exhibit higher selectivity than the monometallic ones. They also have better resistance to deactivation. At the very end of this review the theoretical investigations on H2 dissociation and H adsorption on the bimetallic systems have been mentioned [138-155].