Ordered mesoporous materials in catalysis

4.4. Pd on Modified Silica 159 4.5. Pd on Clay and Other Inorganic Materials 159 5. Stille, Fukuyama, and Negishi Reactions 159 5.1. Stille Reactions 159 5.1.1. Pd on Carbon (Pd/C) 159 5.1.2. Palladium on KF/Al2O3 159 5.1.3. Pd on Modified Silica (SiO2/TEG/Pd) 159 5.2. Fukuyama Reactions 159 5.2.1. Pd on Carbon (Pd/C) 159 5.2.2. Pd(OH)2 on Carbon (Perlman’s Catalyst) 160 5.3. Pd/C-Catalyzed Negishi Reactions 160 6. Ullmann-Type Coupling Reactions 161 6.1. Pd/C-Catalyzed Aryl−Aryl Coupling 161 6.2. Pd/C-Catalyzed Homocoupling of Vinyl Halides 162

https://www.chem.ccu.edu.tw/~joyce/referance/ericyang/Chem.%20Rev/Chem.%20Rev.%202007,%20107,%20133-173.pdf

Carbon-Carbon Coupling Reactions Catalyzed by Heterogeneous Palladium Catalysts

The Hydrothermal Synthesis of Zeolites: History and Development from the Earliest Days to the Present Time

A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true “catalysts” in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano- and macroparticles, soluble palladium nanoparticles, soluble ligand-free palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review

Conjugated microporous polymers (CMPs) are a class of organic porous polymers that combine π-conjugated skeletons with permanent nanopores, in sharp contrast to other porous materials that are not π-conjugated and with conventional conjugated polymers that are nonporous. As an emerging material platform, CMPs offer a high flexibility for the molecular design of conjugated skeletons and nanopores. Various chemical reactions, building blocks and synthetic methods have been developed and a broad variety of CMPs with different structures and specific properties have been synthesized, driving the rapid growth of the field. CMPs are unique in that they allow the complementary utilization of π-conjugated skeletons and nanopores for functional exploration; they have shown great potential for challenging energy and environmental issues, as exemplified by their excellent performance in gas adsorption, heterogeneous catalysis, light emitting, light harvesting and electrical energy storage. This review describes the molecular design principles of CMPs, advancements in synthetic and structural studies and the frontiers of functional exploration and potential applications.

Conjugated microporous polymers: design, synthesis and application

ZSM-20 is a silicon-rich analog of the faujasite-structure, the synthesis of which is complicated. Starting from known synthesis recipes its crystallization in the system Na2O · Al2O3 · SiO2 · H2O is investigated in the presence of tetraethylammoniumhydroxyde as templating agent. The aim was to find the critical conditions for its synthesis. The synthesis products obtained are investigated by X-ray diffraction, thermal analysis and i.r. spectroscopy.



ZSM-20 ist ein neuer siliziumreicher Zeolith mit einer dem Faujasith ahnlichen Struktur, dessen Synthese unzureichend beherrscht wird. Ausgehend von bekannten Vorschriften wird seine Kristallisation im System Na2O · Al2O3 · SiO2 · H2O unter Zusatz von Tetraethylammoniumhydroxid als Templat untersucht. Die Zielstellung betrifft das Auffinden der fur die Synthese kritischen Bedingungen. Die erhaltenen Syntheseprodukte werden mittels Rontgenbeugung, thermischer Analyse und IR-spektroskopisch charakterisiert.

On the Synthesis and Characterization of Zeolite ZSM‐20

The nature of aluminum species in activated and dealuminated HZSM-20 type zeolites has been investigated by high-resolution one-dimensional solid state 27 Al MAS NMR and two-dimensional quadrupole nutation 27 Al MAS NMR spectroscopy. Additionally, IR spectra of adsorbed pyridine were recorded and the catalytic activity of samples was tested in the n-hexane conversion. From NMR experiments it is concluded that during activation and following dealumiation different kinds of 4-, 5- and 6-coordinated extraframework aluminum species are formed strongly depending on conditions of activation and dealumination. Namely, after activation monomeric extraframework Al of very high mobility or of high local symmetry (cubic) seems to appear. This sample exhibits the highest catalytic activity suggesting that monomeric or at least low-condensed extraframework Al plays an important role as active species in acid catalyzed reactions.

Study on the nature of aluminum in dealuminated zeolite ZSM-20

The invention relates to an improved catalyst for synthesizing dimethyl carbonate by reacting methanol, carbon monoxide, and oxygen in the gas phase as well as the use thereof. Said catalyst is composed of a copper-containing zeolite which is produced by admixing one or several halide-free copper(II) compounds to a zeolite in a liquid medium, drying the zeolite modified by means of the admixing process, and tempering the same at 400 to 900°C in inert conditions while substantially maintaining the crystallinity of the zeolite. The admixing process is selected among a group of processes comprising drenching of the zeolite, ion exchange, precipitation of copper(II) hydroxide in the presence of the zeolite, and a combination of said processes. The inventive catalyst is provided with a great space-time yield while remaining constant throughout the operating time without exhibiting corrosive effects.

Catalyst for the synthesis of dimethyl carbonate in the gas phase

Various cloverite samples containing a series of heteroatoms have been synthesized at optimized HF : Ga 2 O 3 ratios and characterized by XRD, adsorption measurements, infrared and ESR spectroscopy. The results show that the pure cloverite structure is only formed in the presence of Ti, Si, Zn, and Mg ions. However, no real evidence can be given for an isomorphous substitution of phosphorus or gallium by the heteroatoms. Conditions for the storage of detemplated cloverite samples are given, which avoid amorphization under the influence of moisture.

The Synthesis of the Molecular Sieve Cloverite in the Presence of Heteroatoms

The crystallization of Ga-ZSM 5 (Si/Ga = 50) in dependence on the synthesis time is examined using XRD, IR spectroscopy, TG/DTA and ammonia TPD. During the rapid crystal growth only a part of the gallium present in the sample is incorporated into the framework. During the following recrystallization process the crystal lattice becomes partially reconstructed where the residual gallium is being fully inserted into framework positions. The catalytic properties are characterized by the conversion of ethylbenzene and the m-xylene isomerization.

Rolf Fricke

Papers

On the Synthesis and Characterization of Zeolite ZSM‐20

Study on the nature of aluminum in dealuminated zeolite ZSM-20

Catalyst for the synthesis of dimethyl carbonate in the gas phase

The Synthesis of the Molecular Sieve Cloverite in the Presence of Heteroatoms

Genesis of Gallosilicates with Zsm-5 Structure. Insertion of Ga and Zeolitic Properties at Various Steps of Crystallization