Light olefins such as ethylene, propylene and butylene are mainly used in the petrochemical industry. Due to the growing need for light olefins in the industry and the future shortage of petroleum resources, the process of converting methanol to olefins (MTO) using non-oil sources has been considered as an alternative. Coal and natural gas are abundant in nature and the methods of converting them to methanol are well known today. Coal gasification or steam reforming of natural gas to produce synthetic gas (CO and hydrogen gas) can lead to methanol production. Methanol can also be catalytically converted to gasoline or olefins depending on the effective process and catalyst factors used. Due to the use of crude methanol in the MTO unit and because the feed does not require primary distillation, if the MTO unit is installed alongside the methanol unit, its capital costs will be reduced. The use of methanol can have advantages such as easier and less expensive transportation than ethane. Among the available catalysts, SAPO-34 is the most suitable catalyst for this process due to its small cavities and medium acidity. One of the problems of MTO units is the rapid deactivation of SAPO-34, which can also be affected by the synthesis factors, so it is possible to optimize the catalyst performance by modifying the synthesis conditions. In this article, we will introduce the MTO process and the factors affecting the production of light olefins.
This review includes 70 monomeric high-spin complexes of the following general compositions: [Fe(II)(η3-pdc)(L)3], [Fe(III)(η3-pdc)(L)3]+, [Fe(II)(η3-pdc)2]2− and [Fe(III)(η3-pdc)2]− (pdc = pyridine-2,6-dicarboxylate (−2)). Each Fe(II) atom has a distorted octahedral geometry. The Fe(III) atoms have a distorted octahedral geometry (most common) and in some examples have a distorted pentagonal-bipyramidal geometry. The chelating donor ligands create varieties of n-membered metallocyclic rings: ONO, OCO, NC2N, OC2N, OC2NO and OC3O. Some cooperative effects between Fe(II) and Fe(III) complexes were found and discussed. There are complexes that are examples of distortion isomerism.
The present review aims to give a comprehensive survey about the chemistry of rhenium(V)-oxo complexes of general formula [ReOX2(N∩O)(EPh3)], where X=Cl, Br, I, E=P, As, and N∩O stands for uninegative chelating N∩O-ligand, carried out within the last four decades. In addition to the synthesis aspects, the available structural data as well as the results issued from techniques such as infrared and ultraviolet-visible spectroscopies are collected and discussed. Furthermore, a brief description of the applications of these compounds in catalysis is included.
The indium complexes are being used in many applications like catalysis, optoelectronics, sensors, solar cells, biochemistry, medicine, infrared (IR) mirrors and thin-film transistors (TFTs). In organometallic complexes of indium, it forms different types of complexes with single, double, triple and tetra linkages by coordinating with numerous elements like C, N, O and S and also with some other elements like Se and Ru. So, the present study comprises all the possible ways to synthesize the indium complexes by reacting with different organic ligands; most of them are N-heterocyclic carbenes, amines, amides and phenols. The commonly used solvents for these syntheses are tetrahydrofuran, dichloromethane, toluene, benzene, dimethyl sulfoxide (DMSO) and water. According to the nature of the ligands, indium complexes were reported at different temperatures and stirring time. Because of their unique characteristics, the organometallic chemistry of group 13 metal indium complexes remains a subject of continuing interest in synthetic chemistry as well as material science.
In this review, the structural parameters of distortion isomers of cis-monomeric Pt(II) coordination complexes with inner coordination spheres: Pt(PL)2X2 (X = OL, NL, SL, Br, I); Pt(PL)2(η2-X2L) (X = O2L, N2L, S2L, OSL, NSL, NSeL); Pt(η2-P2L)X2 (X = Br, I); Pt(η2-P2L)(η2-X2L) (X = O2L, OSL, NSL); Pt(η2-P2L)(NL)(Cl) and Pt(PL)(η2-P,SiL)(H) are analyzed. None of the distortion isomers with cis-configuration has a trans-partner. The distortion isomers differ mostly by the degree of distortion in the Pt-L and L-Pt-L angles. Some of the isomers also differ by crystal packing. The total mean values of Pt-P (monodentate) and Pt-P (bidentate) bond distances are 2.279 Å and 2.244 Å, respectively. The mean value of Pt-P (monodentate) (trans to H¯) of 2.320 Å is the highest one because of higher trans-influence of H¯ over PP3. The total mean values of Pt-X (trans to P) elongate quite well with the covalent radius of the X in the sequence: 1.57 Å (X = H) < 2.062 Å (O2L) < 2.095 Å (OL) < 2.108 Å (NL) < 2.154 Å (N2L) < 2.329 Å (Cl) < 2.342 Å (S2L) < 2.347 Å (SL) < 2.480 Å (Br) < 2.616 Å (I).
Tungsten is an elegant substance, and its compounds have great significance because of their extensive range of applications in diverse fields such as in gas sensors, photocatalysis, lithium ion batteries, H2 production, electrochromic devices, dyed sensitized solar cells, microchip technology, and liquid crystal displays. Tungsten compounds exhibit a more efficient catalytic behavior, and tungsten-dependent enzymes generally catalyze the transfer of an oxygen atom to or from a physiological donor/acceptor with the metal center. Furthermore, tungsten has an n-type semiconductor band gap. Tungsten forms complexes by reacting with several elements such as H, C, N, O, and P as well as other numerous inorganic elements. Interestingly, all tungsten reactions occur at ambient temperature, usually with tetrahydrofuran and dichloromethane under vacuum. Tungsten has extraordinarily high-temperature properties, making it very useful for X-ray production and heating elements in furnaces. Tungsten coordinates with diverse nonmetallic elements and ligands and produces interesting compounds. This article describes an overview of the synthesis of various organometallic compounds of tungsten.
Metallic and bimetallic nanosponges with well-defined size and form have attracted increasing attention due to their unique structural properties and their potential for many applications. In this chapter, the recently developed methods for the synthesis and preparation of metallic and bimetallic nanosponges are presented. These methods can be mainly cataloged in two groups: dealloying-based methods and reduction reaction-based methods. Different topographical reconstruction methods for the investigation of their structural properties are then reviewed briefly. The optical properties of the metallic nanosponges are clearly different from those of the solid counterparts due to the tailored disordered structure. The recent advances in the exploration of the distinct linear and non-linear optical properties of the nanosponges are summarized.
Rare earth metal oxide nanomaterials have drawn much attention in recent decades due to their unique properties and promising applications in catalysis, chemical and biological sensing, separation, and optical devices. Because of the strong structure-property correlation, controllable synthesis of nanomaterials with desired properties has long been the most important topic in nanoscience and nanotechnology and still maintains a grand challenge. A variety of methods, involving chemical, physical, and hybrid method, have been developed to precisely control nanomaterials, including size, shape, dimensionality, crystal structure, composition, and homogeneity. These nanostructural parameters play essential roles in determining the final properties of functional nanomaterials. Full understanding of nanomaterial properties through characterization is vital in elucidating the fundamental principles in synthesis and applications. It allows researchers to discover the correlations between the reaction parameters and nanomaterial properties, offers valuable insights in improving synthetic routes, and provokes new design strategies for nanostructures. In application systems, it extrapolates the structure-activity relationship and reaction mechanism and helps to establish quality model for similar reaction processes. The purpose of this chapter is to provide a comprehensive overview and a practical guide of rare earth oxide nanomaterial design and characterization, with special focus on the well-established synthetic methods and the conventional and advanced analytical techniques. This chapter addresses each synthetic method with its advantages and certain disadvantages, and specifically provides synthetic strategies, typical procedures and features of resulting nanomaterials for the widely-used chemical methods, such as hydrothermal, solvothermal, sol-gel, co-precipitation, thermal decomposition, etc. For the nanomaterial characterization, a practical guide for each technique is addressed, including working principle, applications, materials requirements, experimental design and data analysis. In particular, electron and force microscopy are illuminated for their powerful functions in determining size, shape, and crystal structure, while X-ray based techniques are discussed for crystalline, electronic, and atomic structural determination for oxide nanomaterials. Additionally, the advanced characterization methodologies of synchrotron-based techniques and in situ methods are included. These non-traditional methods become more and more popular because of their capabilities of offering unusual nanostructural information, short experiment time, and in-depth problem solution.