Catalysis Letters Research Articles

Correction to: Reaction Kinetics and Catalysis Letters, volume 84, issue 1, year 2005

Correction to: Reaction Kinetics and Catalysis Letters, volume 84, issue 1, year 2005

Modeling the Environment-Dependent Kinetics of Oxygen Reduction Reaction – Effect of Relative Humidity

For proton exchange membrane fuel cells (PEMFCs) to achieve broad commercialization, the kinetics of oxygen reduction reaction (ORR) need to be better understood to improve the efficiency with minimized use of expensive Pt-based electrocatalyst(1). The increasing demands of PEMFC-powered heavy-duty vehicles make this issue critical, especially to meet the efficiency target (ultimately 72%)(2). Previous first principle-based theoretical analyses reasonably explained catalyst-dependent activity in ideal conditions (on single crystal catalysts in HClO4 solution under room temperature)(3). To design a practical catalyst, further analysis is required to bridge the gap between the ideal and actual PEMFC conditions (typically, covered with perfluorosulfonic acids under 60 to 90 °C, and 30 to 100% RH). In this talk, we examine the effect of relative humidity (RH) on ORR activity on a platinum surface. The effect of RH on ORR activity has been a controversial topic: an experimental study suggested lower RH increases the ORR activity(4), while another study showed the opposite trend(5). By using a multiscale continuum model, we validate our hypothesis that the controversial experimental results stem from the difference in the properties of the electrode/electrolyte interface. In the mathematical calculation, we assume that the polycrystalline platinum catalysts consist of multiple single crystalline surfaces(6) and that their activity is described by the summation of the activities on the single crystalline surfaces. Based on transition state theory, the reaction rate of each elementary step is calculated from the reaction free energy, reactant concentration, and activation energy with explicit accounting of the double-layer structure and interactions. In the presentation, the calculation results will be compared with experimental solid-state data using microelectrodes, and the mechanism of RH-dependent ORR activity will be discussed. Reference I. E. L. Stephens, A. S. Bondarenko, U. Grønbjerg, J. Rossmeisl and I. Chorkendorff, Energy & Environmental Science, 5 (2012).D. A. Cullen, K. C. Neyerlin, R. K. Ahluwalia, R. Mukundan, K. L. More, R. L. Borup, A. Z. Weber, D. J. Myers and A. Kusoglu, Nature Energy, 6, 462 (2021).H. A. Hansen, V. Viswanathan and J. K. Nørskov, The Journal of Physical Chemistry C, 118, 6706 (2014).M. Shibata, M. Inaba, K. Shinozaki, K. Kodama and R. Jinnouchi, Journal of The Electrochemical Society, 169, 044507 (2022).H. Xu, Y. Song, H. R. Kunz and J. M. Fenton, Journal of The Electrochemical Society, 152 (2005).G. A. Tritsaris, J. Greeley, J. Rossmeisl and J. K. Nørskov, Catalysis Letters, 141, 909 (2011).

Polyacrylonitrile‐Derived Co or Fe Containing Nanofibre Catalysts Prepared Via Electrispinning for Alkaline Membrane Fuel Cell Cathode

An increasing worldwide energy demand drives the need for the development of more efficient and greener energy production and storage technologies (1). In recent years, carbon nanofibres (CNFs) have drawn a lot of attention and been widely studied to address these topical problems. For example, the CNF-based materials can be employed as an oxygen reduction reaction (ORR) catalyst at the fuel cell cathode. The CNFs are appealing because of their attractive properties e.g. high specific surface area, high length/diameter ratio, specific porosities and multiple functionalities. For the preparation of CNFs, a simple and versatile technique called electrospinning can be applied (2).In our previous papers regarding CNFs, we have investigated the pyrolyzed electrospun composite materials without added transition metals as ORR catalysts in 0.1 M KOH (3, 4). For further optimization of the catalyst material ORR activity, we have now included the Co or Fe precursors to the electrospinning solution. For the first time, the Fe- or Co-containing polyacrylonitrile (PAN)-based CNFs were studied as a cathode catalyst in the anion exchange membrane fuel cell (AEMFC) (5).The composite catalyst materials were prepared via electrospinning of Iron(II) acetate or Cobalt(II) acetate containing PAN solution with and without ionic liquid (IL). The electrospun nanofibres were pyrolysed at different temperatures and acid treated. The materials consisted of CNFs with diameter from ca. 200 to 700 nm. The composition of the catalysts included C, O, N and corresponding transition metal (Fe or Co). In 0.1 M KOH solution, the best performing ORR catalyst material was Fe‐containing CNF without IL prepared at 800 °C (Fe‐PAN‐A800). The best AEMFC performance was observed for Fe‐containing CNF with IL prepared at 1000 °C. The maximum power density value of this catalyst (Fe/IL‐PAN‐A1000) was 289 mW cm−2, which was 82 % of the value obtained with the commercial Pt/C cathode catalyst (Figure 1). The reasons behind the good performance at the AEMFC cathode were considered to be high specific surface area, mesoporous CNF cross‐linked structure and the presence of ORR‐active N species and Me−Nx sites (5).References A. Sarapuu, E. Kibena-Põldsepp, M. Borghei and K. Tammeveski, Journal of Materials Chemistry A, 6, 776 (2018). A. Barhoum, K. Pal, H. Rahier, H. Uludag, I. S. Kim and M. Bechelany, Applied Materials Today, 17, 1 (2019). M. Mooste, E. Kibena-Põldsepp, L. Matisen, M. Merisalu, M. Kook, V. Kisand, V. Vassiljeva, A. Krumme, V. Sammelselg and K. Tammeveski, Catalysis Letters, 148, 1815 (2018). M. Mooste, E. Kibena-Põldsepp, V. Vassiljeva, M. Merisalu, M. Kook, A. Treshchalov, V. Kisand, M. Uibu, A. Krumme, V. Sammelselg and K. Tammeveski, Journal of Materials Science, 54, 11618 (2019). M. Mooste, E. Kibena-Põldsepp, V. Vassiljeva, A. Kikas, M. Käärik, J. Kozlova, V. Kisand, M. Külaviir, S. Cavaliere, J. Leis, A. Krumme, V. Sammelselg, S. Holdcroft and K. Tammeveski, ChemCatChem, 12, 4568 (2020). Figure 1

Correction to: Enhanced Biosynthesis of Furoic Acid via the Effective Pretreatment of Corncob into Furfural in the Biphasic Media

An error appeared in our paper entitled “Enhanced Biosynthesis of Furoic Acid via the Effective Pretreatment of Corncob into Furfural in the Biphasic Media” published in Catalysis Letters. Unfortunately, there are some mistakes in the values and equation in the Sect. 2.3 Conversion of Corncob to FAL and in Table 2.

Para-Toluenesulfonic Acid Catalyzed Synthesis of Indenes via a Tandem Friedel–Crafts Alkylation/Hydroarylation of Tertiary Propargylic Alcohols with Electron-Rich Arenes

An error appeared in our paper entitled “para-Toluenesulfonic Acid Catalyzed Synthesis of Indenes a Tandem Friedel–Crafts Alkylation/Hydroarylation of Tertiary Propargylic Alcohols with Electron-Rich Arenes” published in Catalysis Letters. The word “via” was unfortunately missed to include in the article title. The correct title is as follows, para-Toluenesulfonic Acid Catalyzed Synthesis of Indenes via a Tandem Friedel–Crafts Alkylation/Hydroarylation of Tertiary Propargylic Alcohols with Electron-Rich Arenes.

Correction to: Bulk Ring-Opening Polymerization of ε-Caprolactone by Zeolitic Imidazolate Framework

An error appeared in our paper entitled “Bulk Ring-Opening Polymerization of e-Caprolactone by Zeolitic Imidazolate Framework” published in Catalysis Letters. The wrong version of Fig. 7 has been used in the article. The corrected Fig. 7 is shown below.

Correction to: Synthesis of Polyhydroquinoline, 2,3-Dihydroquinazolin-4(1H)-one, Sulfide and Sulfoxide Derivatives Catalyzed by New Copper Complex Supported on MCM-41

An error appeared in our paper entitled “Synthesis of Polyhydroquinoline, 2,3-Dihydroquinazolin-4(1H)-one, Sulfide and Sulfoxide Derivatives Catalyzed by New Copper Complex Supported on MCM-41” published in Catalysis Letters. We used the wrong version of Fig. 3 in the article. The corrected Fig. 3 is shown below.

Correction to: The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5-MoO3/TiO2 Catalyst

An error appeared in our paper entitled “The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst” published in Catalysis Letters. We used a wrong icon in Fig. 8. The black line should be “Cat-A-V” and the red line should be “Cat-B-V”. The corrected Fig. 8 is shown below.

(Invited) Single Metal Atom Embedded in Two Dimensional Supports for Active Oxygen Reduction Reaction

Proton-exchange membrane fuel cell (PEMFC) is a clean technology for automobile and stationary applications that converts a chemical energy of H2 into electricity producing environmentally benign water as the only product.[1] The main bottlenecks of PEMFC has been considered to be a sluggish oxygen reduction reaction (ORR) at cathode side, and the use of costly Pt metal catalysts. To circumvent this problem, various Pt-based alloys,[2-4] core-shell structures[5-6] and nanostructure catalysts[7-9] have been extensively investigated to enhance Pt utilization and to improve an intrinsic catalytic activity. Recent catalyst developments have been focusing on dispersing single metal atoms on supports to maximize the metal usage and to introduce the unique catalytic properties compared to the bulk counterparts.[10-11] For instance, theoretical investigation suggested that Au doped graphene is highly active and stable ORR catalysts in contrast to Au (111).[12] Furthermore, comparative experiments demonstrated that the support materials affect the catalytic activity and selectivity significantly[13], indicating that choosing an appropriate combination of metal and support is crucial to design the single atom catalysts with desired catalytic properties. In this work, we focus on two-dimensional materials as supports for ORR single atom catalysts because of their high surface area and capability of stabilizing metal atoms.[14-17] We first investigate the stability of single metal atom on various two-dimensional materials, and then analyze ORR activity of stable metal-support combinations. We find that *OH and *OOH binding free energies are linearly correlated similar to the previous metal-based scaling relation, but we also show that rather smaller slope of the single atom catalysts scaling allows to design catalysts beyond the conventional volcano. We further investigated their possibility as hydrogen evolution reaction catalysts. [1] M. K. Debe, Nature 2012, 486, 43-51. [2] V. R. Stamenkovic, B. S. Mun, K. J. Mayrhofer, P. N. Ross, N. M. Markovic, Journal of the American Chemical Society 2006, 128, 8813-8819. [3] V. R. Stamenkovic, B. Fowler, B. S. Mun, G. Wang, P. N. Ross, C. A. Lucas, N. M. Marković, science 2007, 315, 493-497. [4] J. Greeley, I. Stephens, A. Bondarenko, T. P. Johansson, H. A. Hansen, T. Jaramillo, J. Rossmeisl, I. Chorkendorff, J. K. Nørskov, Nature chemistry 2009, 1, 552-556. [5] S. Back, Y. Jung, ChemCatChem 2017. [6] A. L. Strickler, A. Jackson, T. F. Jaramillo, ACS Energy Letters 2016, 2, 244-249. [7] D. Wang, Y. Yu, H. L. Xin, R. Hovden, P. Ercius, J. A. Mundy, H. Chen, J. H. Richard, D. A. Muller, F. J. DiSalvo, Nano letters 2012, 12, 5230-5238. [8] K. Jiang, Q. Shao, D. Zhao, L. Bu, J. Guo, X. Huang, Advanced Functional Materials 2017. [9] R. Chattot, T. Asset, P. Bordet, J. Drnec, L. Dubau, F. Maillard, ACS Catalysis 2016, 7, 398-408. [10] S. Siahrostami, G.-L. Li, J. K. Nørskov, F. Studt, Catalysis Letters 2017, 147, 2689-2696. [11] J. Liu, M. Jiao, L. Lu, H. M. Barkholtz, Y. Li, Y. Wang, L. Jiang, Z. Wu, D.-j. Liu, L. Zhuang, Nature communications 2017, 8, ncomms15938. [12] S. Stolbov, M. Alcántara Ortigoza, The Journal of chemical physics 2015, 142, 154703. [13] S. Yang, Y. J. Tak, J. Kim, A. Soon, H. Lee, ACS Catalysis 2017, 7, 1301-1307. [14] C. Zhang, J. Sha, H. Fei, M. Liu, S. Yazdi, J. Zhang, Q. Zhong, X. Zou, N. Zhao, H. Yu, ACS nano 2017, 11, 6930-6941. [15] S. Siahrostami, C. Tsai, M. Karamad, R. Koitz, M. García-Melchor, M. Bajdich, A. Vojvodic, F. Abild-Pedersen, J. K. Nørskov, F. Studt, Catalysis Letters 2016, 146, 1917-1921. [16] X. Zhang, J. Guo, P. Guan, C. Liu, H. Huang, F. Xue, X. Dong, S. J. Pennycook, M. F. Chisholm, Nature communications 2013, 4, ncomms2929. [17] G. Elumalai, H. Noguchi, H. C. Dinh, K. Uosaki, Journal of Electroanalytical Chemistry 2017.

Scientific legacy of Georgy K. Boreskov: bibliometric and thematic analysis

Year 2017 is momentous by the 110th anniversary of Prof. Georgy K. Boreskov’s birth. Prof. Georgy K. Boreskov (1907–1984) was a great scientist who made invaluable contribution to the theory of catalysis, kinetics and mechanisms of catalytic reactions. In 1958 he founded the Institute of Catalysis within the structure of Siberian Branch of Academy of Sciences, USSR. The Institute was headed by him until his death in 1984. Bibliometric and thematic analysis of scientific legacy of Prof. Georgy K. Boreskov represented by his publications 1929–1988 referred in the Web of Science, Scopus, Chemical Abstracts Plus and Russian Science Citation Index databases has been performed to highlight his unique contribution into the field of fundamental and applied catalysis. Among the widest areas of his expertise, heterogeneous oxidation catalysis significantly predominates. In patent publications authored by G. K. Boreskov, sulfur oxides are the most frequent compounds. The journal Reaction Kinetics and Catalysis Letters occupies third position (after Kinetics and Catalysis and Doklady Akademii Nauk SSSR) among the most frequent journal titles, where research works of G. K. Boreskov were published.

Fischer-Tropsch synthesis: Effect of solvent on the H2–D2 isotopic exchange rate over an activated nickel catalyst

The effect of solvent on the hydrogen-deuterium isotopic homomolecular exchange rate over a 26.4% Ni/Al2O3 catalyst was investigated using a plug flow reactor at room temperature (23°C) and at atmospheric pressure. In this study, two different molecular weight solvents were tested: n-pentane (MW¯(average molecular weight)=72), and n-hexadecane (MW¯=226). At dry (without addition of solvent) and n-pentane solvent addition conditions, similar amounts of H2 and D2 are consumed and the concentration of the HD produced is two times the consumption of H2 or D2. Thus, these conditions exhibited around 100% exchange with the formation of H2:HD:D2 having a 1:2:1 ratio. With n-hexadecane solvent, the initial exchange rate was approximately 45%, but the exchange rate decreased with time and reached a steady state rate after 60min on-stream. The lower exchange rate of the n-hexadecane solvent might be due to the limited mobility of reactant molecules in the liquid-filled pores of the catalyst. The exchange rate of the catalyst is decreased with increasing molecular weight and density of the solvent. An isotopic partitioning preference was not observed for the nickel catalyst under various co-fed solvents, and similar findings were observed in our previous work (Catalysis Letters 143 (2013) 1368–1373).

Non-PGM ORR Catalyst Active-Site Screening

Non-platinum group metal (non-PGM) oxygen reduction reaction (ORR) catalysts, based on pyrolyzed C, N, and transition metal systems, may replace precious metal catalysts in Pt-based fuel cell cathodes in the future. Major barriers to the adoption of these catalyst materials include much needed improvements in both ORR activity as well as durability under operating conditions. Detailed knowledge of the atomic-scale structure of the active site(s) would aid in strategically synthesizing materials with a higher density of desired active sites (those with simultaneously high ORR activity and practical stability). Density functional theory (DFT) modeling has previously been utilized to consider both relative stability of atomic scale structures,1 as well as to evaluate ORR activity2-5. Through the use of easily calculated descriptors, high-throughput DFT-based materials searches are possible. Relative formation energies of structures can be calculated via DFT with uniform atomic reference states. These formation energies may serve as a descriptor of relative active-site structure stability. This approach also allows for consideration of shifts in chemical potentials that can affect relative stability. Once the relaxed structure has been simulated, calculation of an active site with a bound ORR intermediate allows for an estimate of the binding energy of that intermediate using a computational hydrogen electrode approach2. Previously, O binding has been utilized as an activity descriptor for ORR catalysts2 but for non-PGM catalysts, OH binding is often the potential determining step in the ORR reaction pathway. As such, for screening purposes, we utilize the OH binding energy as a descriptor for ORR activity. Ideally, this value should be close to 1.23 eV with values less than this indicating OH overbinding and values greater indicating underbinding. Scaling law relations6suggest that both O and OH binding energies should be equally valid activity descriptors. We have performed an initial screening of 22 proposed active-site structures containing C, Fe, N, and H, as suggested through previously established structural motifs7. Three graphene-like C host materials, a “bulk” periodic graphene sheet, a zig-zag edge graphene nanoribbon, and an arm-chair edge graphene nanoribbon were considered. Active-site structures with one and two N-coordinated Fe atoms were considered as embedded in each of the three host materials, acting as C substitutional defects. In some cases, iron replaced two carbons to give different Fe coordination symmetry. Direct comparisons between similar structures in different C host materials were made where possible. For the nanoribbon hosted active site structures, the N-coordinated Fe moiety was only considered at the nanoribbon edge. The outcomes of this study will be the focus of this talk. In addition to the previously reported Fe2N5(*OH) zig-zag edge active site structure,8 preliminary studies suggest that bulk and zig-zag edge Fe2N6 structures (Figure 1) also have favorable OH binding characteristics, suggesting further investigation of their full ORR reaction pathways is merited and will be discussed. In all three cases, Fe2N5(*OH) zig-zag edge, Fe2N6 bulk, and Fe2N6 zig-zag edge, Fe is five-fold coordinated with N and a neighboring Fe, suggesting such coordination is an important aspect for tuning OH binding energy. Fe-Fe bond distances of 2.20 Å, 2.25 Å, and 2.24 Å were calculated for the Fe2N5(*OH) zig-zag, Fe2N6 bulk, and Fe2N6 zig-zag structures, respectively. In the case of the Fe2N5(*OH) zig-zag structure, the Fe atoms are initially out of the graphene plane whereas in the Fe2N6structures, they are initially in the graphene plane. Both multi-metal structures show enhanced stability, compared to their single-Fe counterpart structures for a wide range of Fe chemical potentials. By combining these simulation data, all calculated using the same methodology, direct comparison of structure-function relations for activity and structural stability for a wide range of structures, including similar structures at bulk and multiple edges, will be available for comparison. References 1 Holby, E. F. & Taylor, C. D. Applied Physics Letters 101, 064102, (2012). 2 Norskov, J. K. et al. Journal of Physical Chemistry B 108, 17886-17892, (2004). 3 Studt, F. Catalysis Letters 143, 58-60, (2013). 4 Kattel, S., Atanassov, P. & Kiefer, B. The Journal of Physical Chemistry C 116, 17378-17383, (2012). 5 Kattel, S., Atanassov, P. & Kiefer, B. Physical Chemistry Chemical Physics 15, 148-153, (2013). 6 Abild-Pedersen, F. et al. Physical Review Letters 99, 016105, (2007). 7 Holby, E. F., Wu, G., Zelenay, P. & Taylor, C. D. The Journal of Physical Chemistry C 118, 14388-14393, (2014). 8 Holby, E. F. & Taylor, C. D. Scientific Reports 5, (2015). Figure 1. Model Fe2N6 structure at a zig-zag edge nanoribbon with bound OH ORR intermediate. Figure 1

The Frontiers of Catalysis Science and Future Challenges

In the 10th Anniversary issue of Catalysis Letters in 2000, Professor M. W. Roberts reviewed the history of catalysis. This 25th Anniversary of the journal is a major milestone, and thus we have compiled an issue that has papers from some of the leading contributors to the frontiers of catalysis. We believe that now, on the occasion of the Silver Anniversary of the publication of Catalysis Letters, it is appropriate to focus on the rapid growth of the field, its development into molecular catalysis science and the future challenges that will be presented in the next 25 years. The importance of catalysis in energy conversion, in environmental remediation and in the development of new pharmaceuticals and biological chemistry has assured exponential development of the field equally in heterogeneous, homogeneous and enzyme catalysis over the past 25 years. While catalysis science used to be published in specialty journals, it has now entered the mainstream; in addition, the number of journals that publish papers with content chiefly dealing with catalysis has multiplied. Catalysis research is carried out and growing now on all of the continents with particular emphasis on Europe, the Americas, and Asia. The past 25 years have seen a transition of the field from one dominated by catalytic technologies to molecular catalysis science. There are three areas of catalysis science in which major advances have been made.

Response to the Comment of Drs. R. Imbihl and A. Toghan on the Article “Reaction Kinetic-Induced Changes in the Electrochemically Promoted C2H4 Oxidation on Pt/YSZ” by Peng-ont S., Souentie S., Assabumrungrat S., Praserthdam P., Brosda S., Vayenas C. G., Catalysis Letters 143 (2013) 445

My coauthors and I welcome the opportunity to answer the “Comment” of Drs. Imbihl and Toghan in order to address their criticism and thus also necessarily clarify some key points regarding mass transfer effects when studying promotional or, more generally, catalytic phenomena in ambient conditions or in vacuum. Temperature programmed desorption (TPD) spectrum of oxygen from an electrochemically promoted Pt/YSZ catalyst after gaseous 18O2 adsorption followed by electrochemical 16O2− supply, after which the TPD run starts [21]. .

04/01388 Steam reforming of sunflower oil over [formula omitted] catalysts prepared from hydrotalcite-like materials : Marquevich, M. et al. Catalysis Letters, 2003, 85, (1–2), 41–48

04/01388 Steam reforming of sunflower oil over [formula omitted] catalysts prepared from hydrotalcite-like materials : Marquevich, M. et al. Catalysis Letters, 2003, 85, (1–2), 41–48

Erratum: Requiem for the Reaction-Rate Equation?

In a Perspectives in Catalysis article that appeared recently in Catalysis Letters, Professor Michel Boudart hailed a coming revolution in catalytic kinetics [1]. He predicts that the twenty-first century will be dominated by the rate constant, which will be determined by a combination of microkinetic analysis, computational chemistry, and surface science techniques. By contrast, the twentieth century belonged to the rate equation, elucidated using a mechanistic approach to kinetic modeling and supported by discrete experimental data sets arising from a large number of reactions carried out over a range of reaction conditions. Boudart argues that by perfecting the methodology of microkinetic analysis over the next few decades, kinetics-assisted design of catalysts will become predictive, obviating the need for rate equations. Since catalysis is a kinetic phenomenon [2], an approach advocating a prominent role for kinetics in the future development of protocols for discovery, design, and rapid screening of catalysts holds great promise. However, it is perhaps premature to hold a requiem for the rate equation in catalytic reaction kinetics. Indeed, I would argue that the role of the rate equation is currently in ascendance in one area of growing importance, that of research involving the complex organic catalytic reactions common to pharmaceutical applications. In this field, kinetic analysis and the determination of rate constants via the rate equation presents exciting opportunities for future research, aimed at increasing fundamental mechanistic understanding, aiding future catalyst design, and streamlining pharmaceutical process research and development in an ever more competitive environment. The key to this ‘‘back-to-the-future’’ approach to reaction kinetics in liquid-phase organic reactions lies in the recent development of accurate in situ experimental methods for the continuous monitoring of reaction rate as a function of reaction progress. These tools now insure that the fastest way to obtain information about these reactions is simply to run them—and by that I mean to run them just as one would in the commercial application, without resorting to experiments that measure initial rates using distorted reactant concentrations. Monitoring reactions using such in situ methods, we may obtain the equivalent of thousands of separate ‘‘initial-rate’’ measurements at different reactant concentrations in one reaction—typically over the course of an hour or less. What would Langmuir, Rideal, or Michaelis and Menten have given for access to such plentiful data for use in their rate equations? The attraction in pharmaceuticals of an approach based on the rate equation may be stronger than in petrochemical applications. The reasons for this become more clear when we compare key characteristics of typical pharmaceutical reactions with those of the petrochemical or basic chemicals industry, where the methodology of microkinetic analysis [3] described by Boudart has been most successfully applied (table 1). Petrochemical reactions are conventionally carried out at relatively high temperatures over fixed beds of heterogeneous catalysts that maintain a constant level of conversion of the flowing gaseous reactants. The reactants are small molecules, and the products may be many. Networks describing the global reactions can be extremely complex, with parallel and consecutive elementary steps often numbering in the dozens. Incorporating all of these into an explicit rate equation may prove to be intractable. The aim of the microkinetic treatment is to identify the unior bimolecular rate constants for all of these steps, culminating in the presentation of a mechanism-based macroscopic picture of the reaction. For such an approach to be successful, the assembling of the data required entails extensive experimental work, including various ex situ adsorption and surface chemistry experiments in addition to the The publisher regrets that this article first published in Vol. 83, Nos. 3–4 November 2002, pp. 133–136, appeared without any of the equations. Since the author originally supplied the complete article, the publisher accepts full responsibility for this grievous error. This version of the article, now published correctly and in its entirety, is the true representation of the author’s intent. Please contact the author directly regarding reprints. Catalysis Letters Vol. 89, Nos. 3–4, September 2003 (# 2003) 281

Comment on ``Catalytic conversion in water. Part 6. A novel biphasic hydrocarboxylation of olefins catalyzed by palladium TPPTS complexes (TPPTS=P(C6H4-m-SO3Na)3)''

Recently, the biphasic hydrocarboxylation of olefins into carboxylic acids catalyzed by water-soluble palladium complexes has been described in Catalysis Letters as a novel and attractive process for the direct synthesis of carboxylic acids [1]. This interesting new development in the area of the biphasic catalysis had also been reported by our research group in New Journal of Chemistry [2,3]. This independent and simultaneous discovery of the biphasic hydrocarboxylation of olefins by two research groups shows undoubtedly that two-phase catalysis is presently one of the most active areas of catalysis research.

From Microporous to Mesoporous Molecular Sieve Materials and Their Use in Catalysis.

It is possible to say that zeolites are the most widely used catalysts in industry. They are crystalline microporous materials which have become extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis in the production of fine and speciality chemicals, particularly when dealing with molecules having kinetic diameters below 10 A. The reason for their success in catalysis is related to the following specific features of these materials:1 (1) They have very high surface area and adsorption capacity. (2) The adsorption properties of the zeolites can be controlled, and they can be varied from hydrophobic to hydrophilic type materials. (3) Active sites, such as acid sites for instance, can be generated in the framework and their strength and concentration can be tailored for a particular application. (4) The sizes of their channels and cavities are in the range typical for many molecules of interest (5-12 A), and the strong electric fields2 existing in those micropores together with an electronic confinement of the guest molecules3 are responsible for a preactivation of the reactants. (5) Their intricate channel structure allows the zeolites to present different types of shape selectivity, i.e., product, reactant, and transition state, which can be used to direct a given catalytic reaction toward the desired product avoiding undesired side reactions. (6) All of these properties of zeolites, which are of paramount importance in catalysis and make them attractive choices for the types of processes listed above, are ultimately dependent on the thermal and hydrothermal stability of these materials. In the case of zeolites, they can be activated to produce very stable materials not just resistant to heat and steam but also to chemical attacks. Avelino Corma Canos was born in Moncofar, Spain, in 1951. He studied chemistry at the Universidad de Valencia (1967−1973) and received his Ph.D. at the Universidad Complutense de Madrid in 1976. He became director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia in 1990. His current research field is zeolites as catalysts, covering aspects of synthesis, characterization and reactivity in acid−base and redox catalysis. A. Corma has written about 250 articles on these subjects in international journals, three books, and a number of reviews and book chapters. He is a member of the Editorial Board of Zeolites, Catalysis Review Science and Engineering, Catalysis Letters, Applied Catalysis, Journal of Molecular Catalysis, Research Trends, CaTTech, and Journal of the Chemical Society, Chemical Communications. A. Corma is coauthor of 20 patents, five of them being for commercial applications. He has been awarded with the Dupont Award on new materials (1995), and the Spanish National Award “Leonardo Torres Quevedo” on Technology Research (1996). 2373 Chem. Rev. 1997, 97, 2373−2419

Submitted as a letter to the editor of catalysis letters

Submitted as a letter to the editor of catalysis letters

Reaction kinetics and Catalysis Letters Vol. 1, No. 1 (1974), Acadamy of Sciences of the USSR and Hungarian Academy of Sciences, 4 issues per volume, price Dfl. 130. —per volume, incl. postage.

Reaction kinetics and Catalysis Letters Vol. 1, No. 1 (1974), Acadamy of Sciences of the USSR and Hungarian Academy of Sciences, 4 issues per volume, price Dfl. 130. —per volume, incl. postage.