Inorganic Catalysis Research Articles

Reactive boiling of cellulose for integrated catalysis through an intermediate liquid

Advanced biomass processing technology integrating fast pyrolysis and inorganic catalysis requires an improved understanding of the thermal decomposition of biopolymers in contact with porous catalytic surfaces. High speed photography (1000 frames per second) reveals that direct impingement of microcrystalline cellulose particles (300 μm) with rhodium-based reforming catalysts at high temperature (700 °C) produces an intermediate liquid phase that reactively boils to vapors. The intermediate liquid maintains contact with the porous surface permitting high heat transfer (MW m−2) generating an internal thermal gradient visible within the particle as a propagating wave of solid to liquid conversion. Complete conversion to liquid yields a fluid droplet on the catalyst surface exhibiting a linear decrease in droplet volume with time leaving behind a clean surface absent of solid residue (char). Under specific interfacial conditions, conversion with large cellulosic particles on the length-scale of wood chips (millimeters) occurs continuously as generated liquid and vapors are pushed into the porous surface.

A New Bio‐Inspired Route to Metal‐Nanoparticle‐Based Heterogeneous Catalysts

Onion-type multilamellar vesicles are made of concentric bilayers of organic surfactant and are mainly known for their potential applications in biotechnology. They can be used as microreactors for the spontaneous and controlled production of metal nanoparticles. This process does not require any thermal treatment and, hence, it is also attractive for material sciences such as heterogeneous catalysis. In this paper, silver-nanoparticle-based catalysts are prepared by transferring onion-grown silver nanoparticles onto inorganic supports. The resulting materials are active in the total oxidation of benzene, attesting that this novel bio-inspired concept is promising in inorganic catalysis.

Catalysis by Enzymes: The Biological Ammonia Synthesis

Enzymes are nature’s own catalysts and fundamental for life, as they catalyze essentially all biological processes. Compared to inorganic catalysts, however, their structure and function is immensely more complicated. Computational modeling has played an increasing role in elucidating enzyme mechanisms, as it can provide information complementary to experimental techniques. Elucidating enzyme structure and mechanism is not only important to understand the basic functions of life, they can also help to find and develop inorganic catalysts. In this review, an overview of recent computational developments for the enzyme nitrogenase will be given. Nitrogenase catalyzes ammonia synthesis, which is also a very important reaction in inorganic catalysis, and insight on enzyme structure and function could provide understanding on how to design biomimetic catalysts for low temperature ammonia synthesis.

A simple and inexpensive method for investigating microbiological, enzymatic, or inorganic catalysis using standard histology and microbiology laboratory equipment: assembly, mass transfer properties, hydrodynamic conditions and evaluation

We introduce a generic, simple, and inexpensive method for performing microbiological, enzymatic, or inorganic catalysis with solids using standard histology and microbiology laboratory equipment. Histology cassettes were used to standardize hydrodynamic conditions and to protect the catalysts and their solid supports. Histology cassettes have the following advantages: they are readily available, inexpensive, solvent and acid resistant, automatable, and the slots in the cassette walls allow liquid to circulate freely. Standard Erlenmeyer flasks were used as reaction vessels. We developed a new camera to observe the movement and position of the histology cassettes as well as the liquid in the Erlenmeyer flasks. The camera produces a stable image of the rotating liquid in the Erlenmeyer flask. This visualization method revealed that in a 250 ml Erlenmeyer flask, stable operating conditions are achieved at a shaking frequency of 300 rpm and a fill volume of 30 ml. In vessels with vertical walls, such as beakers or laboratory bottles, the movement of the histology cassette is not reproducible. Mass transfer characterization using a biological model system and the chemical sulfite-oxidation method revealed that the histology cassette does not influence gas-liquid mass transfer.

H2-rich fluids from serpentinization: geochemical and biotic implications.

Metamorphic hydration and oxidation of ultramafic rocks produces serpentinites, composed of serpentine group minerals and varying amounts of brucite, magnetite, and/or FeNi alloys. These minerals buffer metamorphic fluids to extremely reducing conditions that are capable of producing hydrogen gas. Awaruite, FeNi3, forms early in this process when the serpentinite minerals are Fe-rich. Olivine with the current mantle Fe/Mg ratio was oxidized during serpentinization after the Moon-forming impact. This process formed some of the ferric iron in the Earth's mantle. For the rest of Earth's history, serpentinites covered only a small fraction of the Earth's surface but were an important prebiotic and biotic environment. Extant methanogens react H2 with CO2 to form methane. This is a likely habitable environment on large silicate planets. The catalytic properties of FeNi3 allow complex organic compounds to form within serpentinite and, when mixed with atmospherically produced complex organic matter and waters that circulated through basalts, constitutes an attractive prebiotic substrate. Conversely, inorganic catalysis of methane by FeNi3 competes with nascent and extant life.

Main Features of the Synthesis and Formation of Cement-Containing Catalysts for Various Processes of Organic, Inorganic, and Environmental Catalysis

The formation of copper-, manganese-, nickel–copper, and other cement-containing catalysts for organic, inorganic, and environmental catalysis are studied by physicochemical and physicomechanical methods. The catalysts are prepared by chemical mixing, impregnation, and mechanochemical activation with high-pressure water jets (30–300 MPa). Strong metal–support interaction during the preparation of the catalysts and the introduction of manganese compounds stabilize copper ions in oxides, hampers the reduction of oxides, and improves the thermal stability of samples and the stability to mechanical disintegration during performance. Deeper interaction between copper and zinc salts enhances the efficiency of copper catalysts. The technologies of the industrial syntheses of catalysts for various industries is developed and used.

Transport studies with porous alumina membranes

In recent years, there has been a growing interest in utilizing inorganic membranes, particularly microporous membranes, for numerous biotechnology applications, inorganic catalysis and separation processes. In order to conduct a fundamental study of any membrane process, a well defined membrane system is required. In this paper, results from characterization experiments performed on porous Anotec alumina membranes containing uniform, parallel pores are reported. Scanning electron microscopy was used to determine pore density and pore length. Solvent (water) flow measurements and benzoic acid diffusion experiments were used to determine the pore radius. The pore radius values determined from these measurements were in good agreement, indicating the validity of the methods as well as pore radius uniformity. The application of this work for preparing a well defined immobilization membrane system is discussed.

Temperature optimum of alkaline phosphatases in some homeothermic and poikilothermic species

1.1. Alkaline phosphatases, determined in biological material from different species in vitro, show specific differences in thermostability (after exposure to 56°C), while having a uniform temperature optimum of 37°C.2.2. Attempting the valid determination of an enzyme activity in vitro usually assumes an approach derived from inorganic catalysis; rather, it should be considered along with all the complexities of the physiological systems in living organisms. Thus, it is advisable to use caution in drawing conclusions about metabolism and enzyme activity in vivo from routine laboratory methods.

The effect of carbonate on the chromium (III)-EDTA reaction: An example of inorganic catalysis

The effect of bicarbonate on the formation of the chromium(III)-thiocyanate complex is an example of coordination catalysis by a secondary ligand and may be a vehicle for the study of elementary solution kinetics.