Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

A critical review of the emerging field of MOF-based catalysis is presented. Discussed are examples of: (a) opportunistic catalysis with metal nodes, (b) designed catalysis with framework nodes, (c) catalysis by homogeneous catalysts incorporated as framework struts, (d) catalysis by MOF-encapsulated molecular species, (e) catalysis by metal-free organic struts or cavity modifiers, and (f) catalysis by MOF-encapsulated clusters (66 references).

Metal–organic framework materials as catalysts

3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

2.2. MOFs with Metal Active Sites 4614 2.2.1. Early Studies 4614 2.2.2. Hydrogenation Reactions 4618 2.2.3. Oxidation of Organic Substrates 4620 2.2.4. CO Oxidation to CO2 4626 2.2.5. Phototocatalysis by MOFs 4627 2.2.6. Carbonyl Cyanosilylation 4630 2.2.7. Hydrodesulfurization 4631 2.2.8. Other Reactions 4632 2.3. MOFs with Reactive Functional Groups 4634 2.4. MOFs as Host Matrices or Nanometric Reaction Cavities 4636

Engineering Metal Organic Frameworks for Heterogeneous Catalysis

Although homogeneous gold catalysis was known previously, an exponential growth was only induced 12 years ago. The key findings which induce that rise of the field are discussed. This includes early reactions of allenes and furanynes and intermediates of these conversions as well as hydroarylation reactions. Other substrate types addressed are alkynyl epoxides and N-propargyl carboxamides. Important vinylgold intermediates, the transmetalation from gold to other transition metals, the development of new ligands for gold catalysis, and significant contributions from computational chemistry are other crucial points for the field highlighted here.

Gold-Catalyzed Organic Reactions

http://digital.csic.es/bitstream/10261/159912/1/Energy%20Procedia%20114%2c302-308%2c2017.pdf

Evaluation of (MnxFe1-x)2TiyOz particles as oxygen carrier for chemical looping combustion

Life cycle assessment of power-to-methane systems with CO2 supplied by the chemical looping combustion of biomass

Siloxanes are a group of Si-based impurities, common in biogas. Although normally present in relatively small amounts, their presence could be highly problematic, as the generated Si could be a precursor to abrasion and wear in downstream components. In this work, the siloxane effect in biogas chemical looping combustion (CLC) was evaluated. CLC of biogas could be an efficient way of achieving CO2 negative emissions. Two oxygen carriers (CuO-based and Fe2O3-based residue) were used in the combustion of a simulated biogas stream in a batch fluidized bed reactor. Here one of the most common siloxane compounds (hexamethyldisiloxane, L2) was utilized together with methane, the most common combustible component in biogas. The siloxane decomposed in the batch reactor, forming gaseous compounds and Si-based particles. The gaseous compounds formed (mainly CO, H2, CH4, and C2) were able to react with the oxygen carrier, whereas the Si originating from the siloxane interacted with the oxygen carrier particles. Elemental analyses of samples obtained from the reactor bed after combustion experiments revealed that significant amounts of Si from siloxane could be found in the oxygen carrier. The X-ray photoelectron spectroscopy (XPS) analyses of the same samples showed that silica in the oxygen carrier was mainly found at the surface of the particles and in the form of SiO2 or silicates/aluminosilicates. The XPS results were in agreement with a theoretical thermodynamic analysis performed to determine the possible stable Si-based species that may be formed. Although the deposition/formation of silica compounds in the oxygen carrier may lead to the agglomeration of particles, such a phenomenon was not observed in the present work.

/pdf/effect-of-the-presence-of-siloxanes-in-biogas-chemical-34bmh6t51d.pdf

Alberto Abad

Papers

Evaluation of (MnxFe1-x)2TiyOz particles as oxygen carrier for chemical looping combustion

Life cycle assessment of power-to-methane systems with CO2 supplied by the chemical looping combustion of biomass

Effect of the Presence of Siloxanes in Biogas Chemical Looping Combustion

Air jet attrition measurements at hot conditions of oxygen carriers for chemical looping combustion

Capture of CO2 in coal combustion