Showing papers in "Applied Catalysis A-general in 2001"

Mechanisms of catalyst deactivation

Abstract: The literature treating mechanisms of catalyst deactivation is reviewed. Intrinsic mechanisms of catalyst deactivation are many; nevertheless, they can be classified into six distinct types: (i) poisoning, (ii) fouling, (iii) thermal degradation, (iv) vapor compound formation accompanied by transport, (v) vapor-solid and/or solid-solid reactions, and (vi) attrition/crushing. As (i), (iv), and (v) are chemical in nature and (ii) and (v) are mechanical, the causes of deactivation are basically three-fold: chemical, mechanical and thermal. Each of these six mechanisms is defined and its features are illustrated by data and examples from the literature. The status of knowledge and needs for further work are also summarized for each type of deactivation mechanism. The development during the past two decades of more sophisticated surface spectroscopies and powerful computer technologies provides opportunities for obtaining substantially better understanding of deactivation mechanisms and building this understanding into comprehensive mathematical models that will enable more effective design and optimization of processes involving deactivating catalysts. © 2001 Elsevier Science B.V. All rights reserved.

Advances in the catalysis of Au nanoparticles

Abstract: Gold catalysts have recently been attracting rapidly growing interests due to their potential applicabilities to many reactions of both industrial and environmental importance. This article reviews the latest advances in the catalysis research on Au. For low-temperature CO oxidation mechanistic arguments are summarized, focusing on Au/TiO 2 together with the effect of preparation conditions and pretreatments. The quantum size effect is also discussed in the adsorption and reaction of CO over Au clusters smaller than 2 nm in diameter. In addition, recent developments are introduced in the epoxidation of propylene, water-gas-shift reaction, hydrogenation of unsaturated hydrocarbons, and liquid-phase selective oxidation. The role of perimeter interface between Au particles and the support is emphasized as a unique reaction site for the reactants adsorbed separately, one on Au and another on the support surfaces.

New developments in catalysis using ionic liquids

Abstract: Ionic liquids are low melting point salts that represent an exciting new class of reaction solvents for catalysis. Being composed entirely of ions, they possess negligible vapour pressures, and the wide range of possible cations and anions means that other solvent properties may be easily controlled. There is currently great interest in the use of these materials as solvents for a wide range of applications, including catalysis. Many reactions show advantages when carried out in ionic liquids, either with regard to enhanced reaction rates, improved selectivity, or easier reuse of catalysts. This review is intended to bring the reader up to date on the developments involving ionic liquids in catalytic applications over the previous 18 months. Recent spectroscopic investigations into the solvent properties of ionic liquids with relevance to catalysis are discussed first, followed by a critical review of the major developments in transition metal, Lewis acid, and enzyme catalysed processes in these solvents. Particular emphasis is given to the combination of ionic liquids with supercritical fluids, Pd-based catalysts, and enzymes. Wherever possible, the results gained in ionic liquids are critically compared with those obtained using other catalytic systems.

Present status and perspectives in de-NOx SCR catalysis

Abstract: This paper surveys the present status and the perspective of de-NO x SCR catalysis for stationary sources, that is based on the reduction of NO x by NH 3 to form water and nitrogen. After a brief description of the SCR chemistry the characteristics of commercial SCR catalysts, their physico-chemical properties and reactivity, and their performances in both NO x reduction and SO 2 oxidation are presented. The mechanism of the SCR reactions, the mathematical modeling of the reactor and the arrangements of the reactor and process are then described. Finally the emerging technologies for NO x removal and the future perspectives of the SCR catalysis are outlined.

Organic chemistry of coke formation

Abstract: The modes of formation of carbonaceous deposits (“coke”) during the transformation of organic compounds over acid and over bifunctional noble metal-acid catalysts are described. At low reaction temperatures, ( 350°C), the coke components are polyaromatic. Their formation involves hydrogen transfer (acid catalysts) and dehydrogenation (bifunctional catalysts) steps in addition to condensation and rearrangement steps. On microporous catalysts, the retention of coke molecules is due to their steric blockage within the micropores.

Automobile exhaust catalysts

Abstract: It has now been over 25 years since the introduction of the catalytic converter to reduce emissions from the internal combustion engine. It is considered one of the greatest environmental successes of the 20th century, however, new emission control technologies are still being developed to meet ever more stringent mobile source (gasoline and diesel) emissions. This short review will discuss the basis for improvements and highlight technology area, which will require further improvements in emissions and fuel economy. Some of the issues related to fuel cells which some believe may replace the internal combustion engines for automobile applications is also be briefly discussed.

Catalyst deactivation: is it predictable?: What to do?

Abstract: Catalyst deactivation is usually inevitable, although the rate at which it occurs varies greatly. This article discusses the causes of deactivation and the influence on reaction rate. Methods for minimising catalyst deactivation, by tailoring catalyst properties and/or process operations, are presented, as well as reactor configurations suitable for the regeneration of deactivated catalysts. Alkane dehydrogenation is used as an example to demonstrate the variety of engineering solutions possible.

Dehydrogenation and oxydehydrogenation of paraffins to olefins

Abstract: Catalytic paraffin dehydrogenation for the production of olefins has been in commercial use since the late 1930s, while catalytic paraffin oxydehydrogenation for olefin production has not yet been commercialized. However, there are some interesting recent developments worthy of further research and development. During World War II, catalytic dehydrogenation of butanes over a chromia-alumina catalyst was practiced for the production of butenes that were then dimerized to octenes and hydrogenated to octanes to yield high-octane aviation fuel. Dehydrogenation employs chromia-alumina catalysts and, more recently, platinum or modified platinum catalysts. Important aspects in dehydrogenation entail approaching equilibrium or near-equilibrium conversions while minimizing side reactions and coke formation. Commercial processes for the catalytic dehydrogenation of propane and butanes attain per-pass conversions in the range of 30–60%, while the catalytic dehydrogenation of C 10 –C 14 paraffins typically operates at conversion levels of 10–20%. In the year 2000, nearly 7 million metric tons of C 3 –C 4 olefins and 2 million metric tons of C 10 –C 14 range olefins were produced via catalytic dehydrogenation. Oxydehydrogenation employs catalysts containing vanadium and, more recently, platinum. Oxydehydrogenation at ∼1000 °C and very short residence time over Pt and Pt-Sn catalysts can produce ethylene in higher yields than in steam cracking. However, there are a number of issues related to safety and process upsets that need to be addressed. Important objectives in oxydehydrogenation are attaining high selectivity to olefins with high conversion of paraffin and minimizing potentially dangerous mixtures of paraffin and oxidant. More recently, the use of carbon dioxide as an oxidant for ethane conversion to ethylene has been investigated as a potential way to reduce the negative impact of dangerous oxidant–paraffin mixtures and to achieve higher selectivity. While catalytic dehydrogenation reflects a relatively mature and well-established technology, oxydehydrogenation can in many respects be characterized as still being in its infancy. Oxydehydrogenation, however, offers substantial thermodynamic advantages and is an area of active research in many fronts.

Cyclohexane oxidation continues to be a challenge

Abstract: Many efforts have been made to develop new catalysts to oxidize cyclohexane under mild conditions. Herein, we review the most interesting systems for this process with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen. Using H 2 O 2 , Na-GeX has been shown to be a most stable and active catalyst. Mesoporous TS-1 and Ti-MCM-41 are also stable, but the use of other metals such as Cr, V, Fe and Mo leads to leaching of the metal. Homogeneous systems based on binuclear manganese(IV) complexes have also been shown to be interesting. When t -BuOOH is used, the active systems are those phthalocyanines based on Ru, Co and Cu and polyoxometalates of dinuclear ruthenium and palladium. Microporous metallosilicates containing different transition metals showed leaching of the metal during the reactions. Molecular oxygen can be used directly as an oxidant and decreases the leaching of active species in comparison to hydrogen peroxide and tert -butyl hydroperoxide. Metal aluminophosphates (metal: Mn, Fe, Co, Cu, Cr V) are active and relatively stable under such conditions. Mn-AlPO-36 yields directly adipic acid, but large amounts of carboxylic acids should be avoided, as they cause metal leaching from the catalysts. Rare earth exchanged zeolite Y also shows good selectivity and activity. In the last part of the review, novel alternative strategies for the production of cyclohexanol and cyclohexanone and the direct synthesis of adipic acid are discussed.

Solid acid catalysis using ion-exchange resins

Abstract: In this review article, we describe the use of commercially available polymeric ion-exchange resins for a range of industrially important transformations. Recent developments both on the materials design and applications will be described. Examples of high catalytic activity will be described in areas ranging from alkylation, transalkylation, isomerization, oligomerization, acylation, esterification and nitration. The two main classes of ion-exchange resins are based upon styrene-based sulfonic acids (Amberlyst® and Dow type resins), which show very high activity in the areas of esterification and etherification, to the perfluorosulfonic acid-based catalysts including the recently developed Nafion® resin/silica nanocomposites. These show very high activity in the area of linear alkyl benzene formation, isomerization, and some select acylation type chemistries. These new types of catalysts (which have been used commercially) are adding to the ever-growing portfolio of highly active solid acid catalysts, which couple both economic and environmental drivers to improve organic transformations within the chemical industry.

A comparative study of water-gas-shift reaction over ceria supported metallic catalysts

Abstract: Water-gas-shift (WGS) reaction rates have been measured on Pd/ceria, Ni/ceria, Fe/ceria, Co/ceria, ceria, and Pd/silica. Pd/ceria exhibited much higher activities than either ceria alone or Pd/silica, demonstrating a cooperative effect between Pd and ceria. Pd/ceria and Ni/ceria showed essentially the same activities and were much more active than either Co/ceria or Fe/ceria. Reaction orders on Pd/ceria were approximately zeroth-order in CO, half-order in H 2 O, inverse-half-order in CO 2 and inverse-first-order in H 2 . Diffuse-reflectance FTIR measurements on Pd/ceria indicate the ceria exists in a reduced state under WGS conditions and is covered by carbonate species that are removed only by reoxidation of ceria The implications of these results for improved WGS catalysis are discussed.

Perspectives in catalytic applications of mesostructured materials

Abstract: This review paper deals with proven and potential applications of mesoporous molecular sieves in catalysis. In addition to introduction and conclusion, the text is divided into two parts, respectively, dedicated to the design of solid catalysts and catalyst supports and to some relevant examples of catalytic processes.

Developments in the production and application of dimethylcarbonate

Abstract: Manufacturing methods of dimethylcarbonate (DMC) are examined, in particular those which have been industrially exploited. Apart from the old phosgenation process, two processes based on the oxy-carbonylation of methanol went on stream: the copper chloride catalysed, one step liquid-phase process, by EniChem, and the palladium catalysed, two steps gas-phase process, via methylnitrite, by UBE. Two further technologies are attractive for full-scale development in the next future: the gas-phase direct methanol oxy-carbonylation and the alkylenecarbonate transesterification process. In the last few years, the use of DMC in the chemical industry has considerably grown, due to its chemical properties and its non-toxicity, an outstanding example being represented by the non-phosgene production of aromatic polycarbonates. Other very promising fields of large scale DMC application are as solvent and as oxygenate in reformulated fuels.

Alkali-treatment technique — new method for modification of structural and acid-catalytic properties of ZSM-5 zeolites

Abstract: ZSM-5 zeolite having a SiO2/Al2O3 molar ratio of 39.4 was treated in a NaOH alkali solution and the changes in structural and acidic properties were investigated. A siliceous species was selectively dissolved from the framework of zeolite, although a lower amount of Al was also eluted. In this procedure, mesopores with a uniform size were formed on the zeolite, while the microporous structure remained. The acidic property was changed very little quantitatively or qualitatively, even though the catalytic activity for cracking of cumene was enhanced by the alkali-treatment. This can be explained by the facts that adsorptive and diffusive properties of cumene through micropores of the ZSM-5 are increased by the creation of mesopores.

Activities and stabilities of heterogeneous catalysts in selective liquid phase oxidations: recent developments

Abstract: Different strategies for the heterogenization of redox-active elements in solid matrices are reviewed. These include framework-substituted molecular sieves, amorphous mixed oxides by grafting or sol–gel methods, grafting or tethering to the inner walls of mesoporous molecular sieves, encapsulation by ship-in-a-bottle or other techniques and ion exchange in layered double hydroxides. The different approaches are illustrated by reference to recent developments involving a variety of metal catalysts — titanium, chromium, cobalt, manganese, iron, ruthenium, tungsten, molybdenum, vanadium and tantalum — in oxidations with O 2 , H 2 O 2 and RO 2 H as primary oxidants. Emphasis is placed on an evaluation of the stability of the various catalysts under reaction conditions, a conditio sine qua non for practical utility. Protocols for establishing heterogeneity are discussed. An analysis of experimental results leads to the conclusion that many of the systems described in the literature, particularly those involving oxometal species, are unstable towards leaching or the appropriate rigorous tests for heterogeneity have not been performed.

Catalysis as a foundational pillar of green chemistry

Abstract: Catalysis is one of the fundamental pillars of green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The design and application of new catalysts and catalytic systems are simultaneously achieving the dual goals of environmental protection and economic benefit. No subject so pervades modern chemistry as that of catalysis. (Ron Breslow, Chemistry Today and Tomorrow: The Central, Useful, and Creative Science ) Green chemistry, the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances, is an overarching approach that is applicable to all aspects of chemistry. From feedstocks to solvents, to synthesis and processing, green chemistry actively seeks ways to produce materials in a way that is more benign to human health and the environment. The current emphasis on green chemistry reflects a shift away from the historic “command-and-control” approach to environmental problems that mandated waste treatment and control and clean up through regulation, and toward preventing pollution at its source. Rather than accepting waste generation and disposal as unavoidable, green chemistry seeks new technologies that are cleaner and economically competitive. Utilizing green chemistry for pollution prevention demonstrates the power and beauty of chemistry: through careful design, society can enjoy the products on which we depend while benefiting the environment. The economic benefits of green chemistry are central drivers in its advancement. Industry is adopting green chemistry methodologies because they improve the corporate bottom line. A wide array of operating costs are decreased through the use of green chemistry. When less waste is generated, environmental compliance costs go down. Treatment and disposal become unnecessary when waste is eliminated. Decreased solvent usage and fewer processing steps lessen the material and energy costs of manufacturing and increase material efficiency. The environmental, human health, and the economic advantages realized through green chemistry are serving as a strong incentive to industry to adopt greener technologies. Developing green chemistry methodologies is a challenge that may be viewed through the framework of the “Twelve Principles of Green Chemistry” [1] . These principles identify catalysis as one of the most important tools for implementing green chemistry. Catalysis offers numerous green chemistry benefits including lower energy requirements, catalytic versus stoichiometric amounts of materials, increased selectivity, and decreased use of processing and separation agents, and allows for the use of less toxic materials. Heterogeneous catalysis, in particular, addresses the goals of green chemistry by providing the ease of separation of product and catalyst, thereby eliminating the need for separation through distillation or extraction. In addition, environmentally benign catalysts such as clays and zeolites, may replace more hazardous catalysts currently in use. This paper highlights a variety of ways in which catalysis may be used as a pollution prevention tool in green chemistry reactions. The benefits to human health, environment, and the economic goals realized through the use of catalysis in manufacturing and processing are illustrated by focusing on the catalyst design and catalyst applications.

Oxidation reactivities of dibenzothiophenes in polyoxometalate/H2O2 and formic acid/H2O2 systems

Abstract: Dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene are typical thiophenic sulfur compounds that exist in diesel fuels Using toluene solutions of the model compounds, experiments were carried out to compare the reactivity of the different dibenzothiophenes in oxidation reactions, a key step for oxidative desulfurizations A series of polyoxometalate/H2O2 systems were evaluated for dibenzothiophene oxidation The H2O2 solutions of phosphotungstic acid and its salt were very active catalyst systems for the model compound oxidation, while their molybdenum counterpart systems were much less active The H2O2 solutions of silicotungstic and silicomolybdic compounds were the least active catalyst systems for the reaction Oxidation reactivities decreased in the order of dibenzothiophene>4-methyldibenzothiophene>4,6-dimethyldibenzothiophene, the same reactivity trend that exists in HDS However, the oxidation of the dibenzothiophenes was achieved under mild reaction conditions and it was easy to increase reaction temperature or reaction time to achieve high oxidation conversions, even for the least reactive 4,6-dimethyldibenzothiophene Apparent activation energies of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene oxidation were 538, 560, and 587 kJ/mol, respectively These activation energies indicated a decrease in reactivity of dibenzothiophenes as methyl substitutes increased at the 4 and 6 positions on dibenzothiophene rings Interestingly, in a formic acid/H2O2 system, the oxidation reactivity of the dibenzothiophenes showed the reverse trend, suggesting that steric hindrance might play a role when bulky polyoxoperoxo species, which likely form in a hydrogen peroxide solution, act as catalysts

Deactivation of supported copper metal catalysts for hydrogenation reactions

Abstract: Laboratory and industrial results are used to elucidate the general features of the deactivation of supported copper metal catalysts in hydrogenation reactions. Hydrogenations with copper catalysts are milder than with their nickel or platinum counterparts, and they have selectivities that are exploited commercially. They are used in single stream plants for production of hydrogen via the low-temperature water shift gas reaction, and for methanol manufacture from synthesis gas, and also in hydrogenation of speciality organic compounds. Common catalyst types are based on Cu/Cr 2 O 3 (copper chromite) or Cu/ZnO formulations that contain stabilisers and promoters such as alkaline earth oxides and Al 2 O 3 . These have several roles, including inhibition of sintering, and poison traps that prevent poisoning of the active metal surface. The best understood are Cu/ZnO formulations that have improved sulphur resistance due to formation of thermodynamically stable ZnS. Copper catalysts are susceptible to thermal sintering via a surface migration process and this is markedly accelerated by the presence of even traces of chloride. Care must be, therefore, taken to eliminate halides from copper catalysts during manufacture, and from the reactants during use. Operating temperatures must be restricted, usually to below 300°C when catalyst longevity is important with large catalyst volumes. Water can soften some Cu/ZnO formulations during use, and cause particle breakage that leads to high-pressure drop and maldistribution of flow through large catalyst beds and impaired performance. Commercial copper catalysts are not acidic, and since they operate under mild conditions, carbon deposition (coking) is uncommon. However, conventional site blocking poisoning with sulphur compounds, and particularly by H 2 S, is common. The initial phase involves interaction with surface hydroxyl groups and elimination of water. Sulphur is retained strongly on the catalyst, and when partially sulphided they can exhibit selectivity in hydrogenation of organic hydrogenations. A variety of other sulphur compounds, and some chlorinated organic compounds, can cause complete deactivation or enhanced selectivity.

Synthesis of dimethyl carbonate and glycols from carbon dioxide, epoxides, and methanol using heterogeneous basic metal oxide catalysts with high activity and selectivity

Abstract: This paper gives a comprehensive report on a two-step synthesis of dimethyl carbonate (DMC) from epoxides, carbon dioxide and methanol using various basic metal oxide catalysts. The first step is the reaction of ethylene oxide or propylene oxide with CO 2 to form the corresponding cyclic carbonates, and the second step is the transesterification reaction of the cyclic carbonates with methanol to DMC and glycols. Among the catalysts examined, MgO is the most active and selective for both these reactions. Other alcohols can be used for the second step, but the activity decreases as the carbon number of the alcohol increases. Although a one-pot synthesis of DMC, i.e. the sequential reaction of the epoxide, CO 2 and methanol, is also possible with MgO, the selectivity is low because of the alcoholysis of the epoxide. In contrast with the reactions of ethylene oxide and propylene oxide, when styrene oxide is used for the first reaction and for the one-pot synthesis, mandelic acid is produced. Basic properties of the metal oxide catalysts were measured by temperature programmed desorption of CO 2 . The relationship between the catalytic performance and the basic property is discussed.

The visible light induced photocatalytic activity of tungsten trioxide powders

Abstract: The preparation, characterization and photoreactivity of tungsten trioxide powders are presented. Tungsten trioxide powders were prepared by air annealing of various W precursors. The effects of W precursor type and pretreatment conditions on the physical properties, and photocatalytic performance of the obtained WO 3 powders were examined. The photooxidation of water to oxygen and protons in the presence of reducible additives Ce 4+ , using the luminous and near IR illumination was used as a test reaction to evaluate the activity of the powders. Increasing annealing temperatures gave materials with a high degree of crystallinity and red-shifted the onset of light absorption. The light absorption of the obtained powders in the long wavelength region versus the type of the W precursor increased in the order: H 2 WO 4 4 ) 6 W 12 O 39 4 ) 10 W 12 O 41 . The level of crystallinity of the obtained powders increased in the order: (NH 4 ) 10 W 12 O 41 ≈(NH 4 ) 6 W 12 O 39 2 WO 4 . The activity of the WO 3 powders depended on the type of W precursor used, annealing conditions, and the physico-chemical characteristics of the resulting powders. The activity according to the types of the W precursor increased in the order: (NH 4 ) 10 W 12 O 41 4 ) 6 W 12 O 39 2 WO 4 . The activity as a function of annealing temperature and duration of W precursors goes through a maximum at 700–800°C and 4–8 h, respectively. Increasing the specific surface area of WO 3 powders, did not alter the activity significantly. Addition of 0.1–1% Pt and RuO 2 as co-catalysts improved the initial rates and long-term activity by about 1.3–1.5 times. Small amounts of hydrogen were also produced from photochemical reactions involving the photoexcitation of Ce 3+ .

Technologies for large-scale gas conversion

Abstract: Indirect conversion of natural gas to liquid fuels via synthesis gas is more efficient than schemes presently known for direct conversion. Synthesis gas routes are capital intensive and hence there is a great interest in optimising process schemes based on steam reforming and autothermal reforming as well as exploring new principles for manufacture of synthesis gas. The paper reviews the requirements to the synthesis gas and the state-of-art of the technologies.

Kinetics of liquid-phase hydrogenation reactions over supported metal catalysts — a review

Abstract: The kinetics of liquid-phase hydrogenation reactions have been reviewed with a special emphasis on α, β-unsaturated aldehydes as reactants. These reactions can be complex and can be influenced by factors such as metal specificity, side reactions, and metal-support interactions as well as reaction parameters. The importance of results in the absence of heat and mass transfer limitations has been emphasized. Hydrogenation reactions are typically assumed to be structure-sensitive, but dependencies on metal crystallite size have been reported; however, this behavior has been attributed to side reactions which can inhibit activity. Finally, solvent effects can exist, but the effect of H2 concentration in the liquid phase has infrequently been isolated. Thermodynamic arguments indicate that a solvent effect can enhance the surface coverage of hydrogen on the catalyst surface at a constant H2 partial pressure, but in the absence of any solvent effects, surface coverage is independent of the liquid-phase H2 concentration.

Lubricant base fluids based on renewable raw materials: Their catalytic manufacture and modification

Abstract: Lubricants based on renewable raw materials and their derivatives are drawing increased attraction in various applications. Here, the environmental awareness is the key factor of success. The use of such rapidly biodegradable materials is especially favourable in loss-lubrication and hydraulic systems with increased risk of damage. Environmentally friendly, biodegradable alternatives are available for a large variety of mineral oil based lubricants. The substitution of mineral oil with biodegradable base oils is a primary objective. Vegetable oils are the major source of these base fluids. Compared to conventional mineral oil based fluids most of such substances exhibit lower thermal and oxidation stability and even worse low-temperature behaviour. These physical and chemical properties can be improved by chemical modification. This review covers chemical reactions performed on fatty compounds on both laboratory and industrial scale. Economic processes are presented as well as new reactions with potential market value. Alternative routes to improved rapidly biodegradable base fluids are mentioned too, e.g. breeding successes with high oleic sunflower oil.

Production of titanium containing molecular sieves and their application in catalysis

Abstract: This paper reviews several important issues related with industrial application of catalysts based on titanium silicalite-1 (TS-1). The catalyst preparation has been discussed, especially considering the most critical parameters for industrial application. Two processes already demonstrated on industrial scale (phenol hydroxylation and cyclohexanone ammoximation), and a process, under development by several industrial groups (propylene epoxidation), have been reported and discussed. The possibility to insert titanium in large pore zeolites, in order to widen the application field of this kind of materials, has been considered and the behaviour of several new materials has been reported and compared with the catalytic properties of TS-1.

Enantioselective catalysis in fine chemicals production

Abstract: This review describes the state of the art for the application of enantioselective catalysts for the industrial production of enantiomerically enriched chiral fine chemicals. In a certain sense it is an up-date of an overview written by Scott 10 years ago [1] . A comparison of the two articles reveals that certain aspects such as the difficulty to get precise information on industrial processes remained the same. As a consequence, many references relate to relatively informal sources such as C&EN, proceedings of commercial meetings and reviews. Other aspects, especially the state of the art in enantioselective catalysis but also the nature of the industrial players have changed significantly in the last decade. The present overview tries to cover all enantioselective catalytic processes that have been and/or still are used for the commercial manufacture of enantioenriched intermediates. In addition, we have also tried to get information on catalytic processes not (yet) used in actual production. Another goal of the review is to give the organic chemist working in process development an impression of the synthetic opportunities of enantioselective catalysis and to impart to the production manager some understanding of the potential problems when enantioselective processes are developed. After a short introduction to the world of chirality and enantioselective catalysis, the most important production methods for enantiopure chiral molecules are described. The relevant requirements for the application of enantioselective catalysis in fine chemicals production are then discussed in order to show what factors determine whether a catalytic method can be applied successfully or not. In the next paragraphs, the major industrial players in the field of enantioselective catalysis, existing processes in production and selected examples of processes in the bench scale and pilot stage are described. In a similar way, large scale ligands and chiral auxiliaries for enantioselective catalysis and their producers are tabulated and described.

Solid base catalysts: generation of basic sites and application to organic synthesis

Abstract: Studies of solid base catalysts on generation of basic sites and their catalytic behaviors in organic reactions performed in our group are summarized. For most of the materials called solid base, the catalytic activities appear on removal of water and carbon dioxide from the surfaces. The nature of the surface basic sites varies with severity of pre-treatment conditions. Besides removal of water and carbon dioxide, rearrangement of surface and bulk atoms occurs during pre-treatment, which changes the number and nature of the basic sites with increasing the pre-treatment temperature. Therefore, the optimum pre-treatment temperature varies with the type of reaction. Applications of solid base catalysts to the following reactions are described; (1) double bond isomerization, (2) hydrogenation, (3) amination, (4) dehydrocyclodimerization, (5) aldol addition, (6) nitroaldol reaction, (7) Michael addition, (8) conjugate addition of alcohol, (9) cyanoethylation, and (10) Tishchenko reaction. Characteristic features of the solid base catalysts toward these reactions are briefly explained. Finally, selected base-catalyzed reactions which have been industrialized by use of solid base catalyst are exemplified, and short comments on the catalysts used in these processes are made.

Methanol technology developments for the new millennium

Abstract: This contribution to the “special issue” of Applied Catalysis A: General entitled “Industrial catalytic processes” deals with the development of the methanol process during the last 10–15 years. Following a brief review of the history, the developments to improve methanol synthesis are presented along the lines of elements of catalyst system improvements and of reactor improvements.

Recent advances in processes and catalysts for the production of acetic acid

Abstract: Novel acetic acid processes and catalysts have been introduced, commercialized, and improved continuously since the 1950s. The objective of the development of new acetic acid processes has been to reduce raw material consumption, energy requirements, and investment costs. At present, industrial processes for the production of acetic acid are dominated by methanol carbonylation and the oxidation of hydrocarbons such as acetaldehyde, ethylene, n-butane, and naphtha. This paper discusses advances in acetic acid processes and catalysts according to the following routes: (1) methanol carbonylation; (2) methyl formate isomerization; (3) synthesis gas to acetic acid; (4) vapor phase oxidation of ethylene, and (5) other novel technologies.

Decomposition of methane over supported-Ni catalysts: effects of the supports on the catalytic lifetime

Abstract: Decomposition of methane into carbon and hydrogen over Ni catalysts supported on different supports was studied. The catalytic activities and the lifetimes of the catalysts for the reaction were examined and are discussed. Ni catalysts supported on SiO 2 , TiO 2 and graphite showed high activities and long lifetimes for the reaction, whereas the catalysts supported on Al 2 O 3 , MgO and SiO 2 ·MgO were inactive for the reaction. The relation between the catalytic performance of the supported-Ni catalysts and the structure or electronic state of Ni species is discussed on the bases of the results of X-ray diffraction (XRD) and Ni K-edge XANES/EXAFS. In the supported-Ni catalysts effective for the methane decomposition, Ni species were present as crystallized Ni metal particles. On the other hand, the Ni species on the inactive catalysts were present as nickel oxides mainly, suggesting the formation of a compound oxide between Ni and the supports. The catalytic performance of the Ni catalysts supported on silicas with different specific surface areas and pore structures indicated that the catalytic activity and lifetime for the methane decomposition depended significantly on the pore structures of the supports. The silica support with no pore structure was the most favorable one for enhancing the catalytic activity and lifetime of the supported-Ni catalysts.

Alloy catalysts: the concepts

Abstract: In this review basic concepts are discussed which in last 30 years formed the background of the research on alloy catalysts. An attempt is made to describe the present state of understanding of the real and potential effects induced by alloying metals. A brief discussion is also devoted to the quantum theory of alloys, practical applications and speculations about the future developments in catalysis by alloys.