Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.

Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity

Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M4L6 supramolecular tetrahedron can encapsulate a variety of cationic guests with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated, and the C−H bond activation of aldehydes occurs with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

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Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

Meeting the growing global energy demand is one of the important challenges of the 21st century. Currently over 80% of the world's energy requirements are supplied by the combustion of fossil fuels, which promotes global warming and has deleterious effects on our environment. Moreover, fossil fuels are non-renewable energy and will eventually be exhausted due to the high consumption rate. A new type of alternative energy that is clean, renewable and inexpensive is urgently needed. Several candidates are currently available such as hydraulic power, wind force and nuclear power. Solar energy is particularly attractive because it is essentially clean and inexhaustible. A year's worth of sunlight would provide more than 100 times the energy of the world's entire known fossil fuel reserves. Photocatalysis and photovoltaics are two of the most important routes for the utilization of solar energy. However, environmental protection is also critical to realize a sustainable future, and water pollution is a serious problem of current society. Photocatalysis is also an essential route for the degradation of organic dyes in wastewater. A type of compound with the defined structure of perovskite (ABX3) was observed to play important roles in photocatalysis and photovoltaics. These materials can be used as photocatalysts for water splitting reaction for hydrogen production and photo-degradation of organic dyes in wastewater as well as for photoanodes in dye-sensitized solar cells and light absorbers in perovskite-based solar cells for electricity generation. In this review paper, the recent progress of perovskites for applications in these fields is comprehensively summarized. A description of the basic principles of the water splitting reaction, photo-degradation of organic dyes and solar cells as well as the requirements for efficient photocatalysts is first provided. Then, emphasis is placed on the designation and strategies for perovskite catalysts to improve their photocatalytic activity and/or light adsorption capability. Comments on current and future challenges are also provided. The main purpose of this review paper is to provide a current summary of recent progress in perovskite materials for use in these important areas and to provide some useful guidelines for future development in these hot research areas.

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment.

Wieslaw J. Roth,†,∥ Petr Nachtigall,‡ Russell E. Morris, and Jirí̌ Čejka*,† †J. Heyrovsky ́ Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejsǩova 3, CZ-182 23 Prague 8, Czech Republic ‡Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, Prague 2, 128 00, Czech Republic EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews KY16 9ST, Scotland Faculty of Chemistry, Jagiellonian University in Krakoẃ, ul. Ingardena 3,30-060 Krakoẃ, Poland

Two-dimensional zeolites: current status and perspectives.

The discovery of the dual aromatic- and olefin-based catalytic cycles in methanol-to-hydrocarbons (MTH) catalysis on acid zeolites has given a new context for rationalizing structure–function relationships for this complex chemistry. This perspective examines six major chemistries involved in the hydrocarbon pool mechanism for MTH—olefin methylation, olefin cracking, hydrogen transfer, cyclization, aromatic methylation, and aromatic dealkylation—with a focus on what is known about the rate and mechanism of these chemistries. The current mechanistic understanding of MTH limits structure–function relationships to the effect of the zeolite framework on the identity of the hydrocarbon pool and the resulting product selectivity. We emphasize the need for assessing the consequences of zeolite structure in MTH in terms of experimentally measured rates and activation barriers for individual reaction steps and in terms of speciation preferences within the dual olefin- and aromatic-catalytic cycles to alter their r...

Mechanism of the Catalytic Conversion of Methanol to Hydrocarbons

The transparent, double bridged-(R)-spiral three-dimensional polymeric complex K0.4 [Cr(CN)6 ][Mn(S)-pn](S)-pnH0.6 ((S)-pn=(S)-1,2-diaminopropane) has been synthesized and characterized (see X-ray structure; Cr: brown, Mn: red, C: gray, N: blue, K: green). Magnetic measurements on the complex show that the MnII and CrIII ions interact ferrimagnetically and magnetic transition occurs at 53 K (Curie temperature).

A Three-Dimensional Ferrimagnet with a High Magnetic Transition Temperature (TC) of 53 K Based on a Chiral Molecule

The effects of external surface and acid properties of desilicated H-type ZSM-5 zeolites (H-ZSM-5) on their catalytic performance in hexane cracking were investigated. H-ZSM-5 with two different crystallite sizes of 100 nm and 1 μm were treated with NaOH solution of different concentrations. The external surface area (SEXT) was increased with an increase in the NaOH concentration, because of the formation of mesopores inside the H-ZSM-5 crystallites as a result of desilication. The increase in the SEXT of the H-ZSM-5 catalysts contributed to mitigating the catalyst deactivation during the hexane cracking. Although the amount of coke deposited on the alkali-treated H-ZSM-5 was larger than that on the parent H-ZSM-5, the micropore volume of the alkali-treated H-ZSM-5 decreased less due to coke deposition than that of the parent. The deactivation rate and the decrease in the micropore volume of the small-sized H-ZSM-5 catalysts were smaller than those of the large-sized catalysts, because they had shorter average diffusion path lengths. Thus the activity of the alkali-treated H-ZSM-5, especially small-sized one is less sensitive to coke deposition. Lewis acid sites (LASs) were generated by treating with NaOH of high concentrations. The selectivities to benzene, toluene and xylene (BTX) in the hexane cracking were increased with an increase in the LASs amount at high reaction temperatures (≥873 K). The LASs on the alkali-treated H-ZSM-5 were selectively removed by acid treatment. The resultant H-ZSM-5 exhibited a slightly lower hexane conversion and a lower selectivity to BTX but a small amount of coke compared to the parent and alkali-treated H-ZSM-5 catalysts, suggesting that LASs on alkali-treated H-ZSM-5 accelerated the dehydrogenation including hydride transfer and aromatization, forming BTX, which would be precursors of coke.

Effect of desilication of H-ZSM-5 by alkali treatment on catalytic performance in hexane cracking

Facile control of crystallite size of ZSM-5 catalyst for cracking of hexane

Dark orange, hexagonal prism crystals of [Cr(CN)6] [Mn Dor L-NH2ala]3·(3H2O) were obtained by slow diffusion of MnCl2·4H2O (1.7 mmol), Dor L-aminoalanine hydrochloride (Dor L-NH2alaH·HCl, 2.6 mmol), and KOH (5.2 mmol) in H2O into K3[Cr(CN)6] (1.5 mmol) in H2O/iso-propanol (1:1) mixture under argon atmosphere after several weeks. X-ray crystal structure analyses of Dand L-isomers at 100 K reveal that compounds (1) crystallize in the chiral space group, hexagonal P63, and consist of leftand right-handed helical structures of MnII ions, respectively (Figure 1). Each aminoalanine ion employs two types of functional groups to bridge between two adjacent MnII ions (Mn– Mn separation is 5.923 Å.). Two amino moieties and one carboxyl group within the aminoalanine ion are coordinated to two MnII ions in monodentate and bidentate coordination mode, respectively. This unique coordination leads to the construction of two differing chelating rings around the MnII ion: fiveand six-membered rings. These rings align alternately resulting in the generation of extended helical chains along the c-axis. As expected, self-assemblies are formed between helical chains to aggregate three helical chains (Figure 2), in which the shortest Mn–Mn separation between chains is 6.517 Å. The channel structure is generated and disordered water molecules exist in the center of the triple helical strand structure (on the screw axis). On the other hand, each [Cr(CN)6] ion utilizes all cyanide moieties to connect between adjacent strands via cyanide bridges to MnII ions; as a result, a threedimensional cyanide network is formed. The shortest and longest adjacent Cr–Mn distances through cyanide bridges are 5.490 and 5.508 Å, respectively, which are slightly longer than those in the previous crystals. The cyanide bridged network also displays basic units comprised of a helical strand structure. Each cyanidebridged helical strand, which is composed of four metal centers (two MnII and two CrIII ions) and four cyanide groups as a repeating unit characterized by a reverse turn within the helical strand of MnII and NH2ala ions along the c-axis, shares the apex of the helical strand (CrIII ion) between three adjacent helical strands (Figure 1). This compound exhibits ferrimagnetic behavior essentially below 35 K. The magnetic transition temperature of this compound is relatively low despite formation of a three-dimensional cyanide network. This phenomenon is probably attributable to the comparatively long cyanide-bridged distance in this crystal. In addition, it may result consequent to the occurrence of spin frustration between manganese ions within the triple helical strand at high temperature. Below 35 K, the spin on manganese alone survives due to the ferrimagnetic coupling between manganese and chromium ions. From a physical standpoint, this phenomenon is the focus of interesting research, as the spin structure of this compound is also expected to possess triple helical nature. Some chiral molecule-based magnets have been prepared previously; however, at present, a chiral helical spin structure has not been documented. It is one of the reasons affording an explanation as to why a crystal forming a helical structure has never been synthesized. Thus, it is certain that this molecule is a suitable candidate for this endeavor. Magnetization measurements, μSR (muon spin resonance) spectroscopy and neutron diffraction of a single crystal will lead 115 Annual Review 2004

Hiroyuki Imai

Papers

A Three-Dimensional Ferrimagnet with a High Magnetic Transition Temperature (TC) of 53 K Based on a Chiral Molecule

Effect of desilication of H-ZSM-5 by alkali treatment on catalytic performance in hexane cracking

Facile control of crystallite size of ZSM-5 catalyst for cracking of hexane

Three-dimensional chiral molecule-based ferrimagnet with triple-helical-strand structure.

Diversification of RTH‐Type Zeolite and Its Catalytic Application