Bifunctional Zeolite- and Aluminophosphate-Based Catalysts for Hydrocracking and Hydroisodeparaffinization. Part 1. The Influence of the Nature and Activity of the Hydrogenating and Acidic Components on the Activity and Selectivity of Hydrocracking Cataly

Sulfur resistance of nickel, platinum and palladium metals on acid supports was studied depending on the support nature. Catalysts comprising nickel, platinum, palladium metals and sulfides as hydro-dehydrogenating components were examined for hydrocracking of n-octane. HY, ZSM-5, ZSM-23, ZSM-12, as well as silicoaluminophosphates SAPO-11 and SAPO-31 were used as the supports. The sulfur resistance of the supported metals in the catalysts was shown different and independent of the properties of the acidic support under the reaction conditions. Hydrocracking follows two different pathways depending on the activity and nature of the hydro-, dehydrogenating component (a metal or the sulfide), as well as on the ratio of activities of the acidic and hydrogenating components. The first pathway is preferable cracking of the initial paraffin at the early stage, and the second is dehydrogenation of the initial paraffin.

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Sputtered Platinum Thin-films for Oxygen Reduction in Gas Diffusion Electrodes: A Model System for Studies under Realistic Reaction Conditions

Surfaces ◽

10.3390/surfaces2020025 ◽

2019 ◽

Vol 2 (2) ◽

pp. 336-348 ◽

Cited By ~ 6

Author(s):

Gustav W. Sievers ◽

Anders W. Jensen ◽

Volker Brüser ◽

Matthias Arenz ◽

María Escudero-Escribano

Keyword(s):

Fuel Cells ◽

Oxygen Reduction ◽

Specific Activity ◽

Early Stage ◽

Gas Diffusion ◽

Rotating Disk Electrode ◽

Membrane Electrode ◽

Catalyst Characterization ◽

Reaction Conditions ◽

Electrode Potentials

The development of catalysts for the oxygen reduction reaction in low-temperature fuel cells depends on efficient and accurate electrochemical characterization methods. Currently, two primary techniques exist: rotating disk electrode (RDE) measurements in half-cells with liquid electrolyte and single cell tests with membrane electrode assemblies (MEAs). While the RDE technique allows for rapid catalyst benchmarking, it is limited to electrode potentials far from operating fuel cells. On the other hand, MEAs can provide direct performance data at realistic conditions but require specialized equipment and large quantities of catalyst, making them less ideal for early-stage development. Using sputtered platinum thin-film electrodes, we show that gas diffusion electrode (GDE) half-cells can be used as an intermediate platform for rapid benchmarking at fuel-cell relevant current densities (~1 A cm−2). Furthermore, we demonstrate how different parameters (loading, electrolyte concentration, humidification, and Nafion membrane) influence the performance of unsupported platinum catalysts. The specific activity could be measured independent of the applied loading at potentials down to 0.80 VRHE reaching a value of 0.72 mA cm−2 at 0.9 VRHE in the GDE. By comparison with RDE measurements and Pt/C measurements, we establish the importance of catalyst characterization under realistic reaction conditions.

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Sulfur resistance of supported metals in 3-thiolene-1,1-dioxide hydrogenation

Reaction Kinetics and Catalysis Letters ◽

10.1007/bf02477525 ◽

1997 ◽

Vol 61 (1) ◽

pp. 133-138 ◽

Cited By ~ 2

Author(s):

N. T. Kulishkin ◽

A. V. Mashkina

Keyword(s):

Sulfur Resistance ◽

Supported Metals

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Prediction of Residual Curing Capacity of Melamine-Formaldehyde Resins at an Early Stage of Synthesis by In-Line FTIR Spectroscopy

Polymers ◽

10.3390/polym13152541 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2541

Author(s):

Regina Seidl ◽

Stephanie Weiss ◽

Rudolf W. Kessler ◽

Waltraud Kessler ◽

Edith M. Zikulnig-Rusch ◽

...

Keyword(s):

Chemical Structure ◽

Early Stage ◽

Least Squares Regression ◽

Melamine Formaldehyde ◽

Scanning Calorimetry ◽

Reaction Conditions ◽

Surface Finishes ◽

Initial Stage ◽

Batch Modelling ◽

Modelling Approach

Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as the exothermic curing enthalpy is integral to the liquid resin. After resin synthesis is completed, the resulting pre-polymer has a defined chemical structure with a corresponding residual curing capacity. Predicting the residual curing capacity of a resin batch already at an early stage during synthesis would enable corrective measures to be taken by making adjustments in the reaction conditions. Thereby, discarding faulty batches could be avoided. Here, by using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression. Not only is there a strong correlation (R2 = 0.89) between the infrared spectra measured at the end of MF resin synthesis and the residual curing capacity, but also the inline reaction spectra obtained already at the point of complete dissolution of melamine upon methylolation during the initial stage of resin synthesis are also well suited for predicting final curing performance of the resin and a valid regression model (R2 = 0.85) can be established using information obtained at a very early stage of MF resin synthesis.

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Empowering alcohols as carbonyl surrogates for Grignard-type reactions

Nature Communications ◽

10.1038/s41467-020-19857-9 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Chen-Chen Li ◽

Haining Wang ◽

Malcolm M. Sim ◽

Zihang Qiu ◽

Zhang-Pei Chen ◽

...

Keyword(s):

Functional Group ◽

Early Stage ◽

Grignard Reaction ◽

Synthetic Chemistry ◽

Reaction Conditions ◽

Type Reaction ◽

Pincer Complex ◽

Late Stages

AbstractThe Grignard reaction is a fundamental tool for constructing C-C bonds. Although it is widely used in synthetic chemistry, it is normally applied in early stage functionalizations owing to poor functional group tolerance and less availability of carbonyls at late stages of molecular modifications. Herein, we report a Grignard-type reaction with alcohols as carbonyl surrogates by using a ruthenium(II) PNP-pincer complex as catalyst. This transformation proceeds via a carbonyl intermediate generated in situ from the dehydrogenation of alcohols, which is followed by a Grignard-type reaction with a hydrazone carbanion to form a C-C bond. The reaction conditions are mild and can tolerate a broad range of substrates. Moreover, no oxidant is involved during the entire transformation, with only H2 and N2 being generated as byproducts. This reaction opens up a new avenue for Grignard-type reactions by enabling the use of naturally abundant alcohols as starting materials without the need for pre-synthesizing carbonyls.

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Undecagold labeling of tRNA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100084521 ◽

1991 ◽

Vol 49 ◽

pp. 44-45

Author(s):

James F. Hainfeld ◽

Kyra M. Alford ◽

Mathias Sprinzl ◽

Valsan Mandiyan ◽

Santa J. Tumminia ◽

...

Keyword(s):

High Resolution ◽

Transmission Electron Micrograph ◽

Anticodon Loop ◽

Electron Micrograph ◽

Reaction Conditions ◽

Scanning Transmission Electron ◽

Transmission Electron ◽

Scanning Transmission

The undecagold (Au11) cluster was used to covalently label tRNA molecules at two specific ribonucleotides, one at position 75, and one at position 32 near the anticodon loop. Two different Au11 derivatives were used, one with a monomaleimide and one with a monoiodacetamide to effect efficient reactions.The first tRNA labeled was yeast tRNAphe which had a 2-thiocytidine (s2C) enzymatically introduced at position 75. This was found to react with the iodoacetamide-Aun derivative (Fig. 1) but not the maleimide-Aun (Fig. 2). Reaction conditions were 37° for 16 hours. Addition of dimethylformamide (DMF) up to 70% made no improvement in the labeling yield. A high resolution scanning transmission electron micrograph (STEM) taken using the darkfield elastically scattered electrons is shown in Fig. 3.

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Alterations in the number of motoneurons containing immunoreactive calcitonin gene-related peptide(CGRP)& choline acetyltransferase(ChAT) in the cervical spinal cord of the wobbler mouse during the development of the motoneuron disease

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141226 ◽

1995 ◽

Vol 53 ◽

pp. 970-971

Author(s):

L. Vacca-Galloway ◽

Y.Q. Zhang ◽

P. Bose ◽

S.H. Zhang

Keyword(s):

Spinal Cord ◽

Early Stage ◽

Cervical Spinal Cord ◽

Wild Type Mouse ◽

Reflex Response ◽

Mouse Strains ◽

Behavioral Tests ◽

Wobbler Mouse ◽

Stage 4 ◽

Stage 1

The Wobbler mouse (wr) has been studied as a model for inherited human motoneuron diseases (MNDs). Using behavioral tests for forelimb power, walking, climbing, and the “clasp-like reflex” response, the progress of the MND can be categorized into early (Stage 1, age 21 days) and late (Stage 4, age 3 months) stages. Age-and sex-matched normal phenotype littermates (NFR/wr) were used as controls (Stage 0), as well as mice from two related wild-type mouse strains: NFR/N and a C57BI/6N. Using behavioral tests, we also detected pre-symptomatic Wobblers at postnatal ages 7 and 14 days. The mice were anesthetized and perfusion-fixed for immunocytochemical (ICC) of CGRP and ChAT in the spinal cord (C3 to C5).Using computerized morphomety (Vidas, Zeiss), the numbers of IR-CGRP labelled motoneurons were significantly lower in 14 day old Wobbler specimens compared with the controls (Fig. 1). The same trend was observed at 21 days (Stage 1) and 3 months (Stage 4). The IR-CGRP-containing motoneurons in the Wobbler specimens declined progressively with age.

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Automated high-resolution microscopy: the approaches so far

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125312 ◽

1987 ◽

Vol 45 ◽

pp. 58-61

Author(s):

W. O. Saxton

Keyword(s):

High Resolution ◽

Early Stage ◽

Automatic Recording ◽

Microprocessor Control ◽

Alternative Systems ◽

Electron Image ◽

Complete Automation ◽

Analysis System ◽

High Resolution Microscopy

Recent commercial microscopes with internal microprocessor control of all major functions have already demonstrated some of the benefits anticipated from such systems, such as continuous magnification, rotation-free diffraction and magnification, automatic recording of mutually registered focal series, and fewer control knobs. Complete automation of the focusing, stigmating and alignment of a high resolution microscope, allowing focal series to be recorded at preselected focus values as well, is still imminent rather than accomplished, however; some kind of image pick-up and analysis system, fed with the electron image via a TV camera, is clearly essential for this, but several alternative systems and algorithms are still being explored. This paper reviews the options critically in turn, and stresses the need to consider alignment and focusing at an early stage, and not merely as an optional extension to a basic proposal.

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Direct observation of Fe-Al-Zn ternary intermetallic compound and its transformation during the early stage of hot-dip galvanizing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151416 ◽

1993 ◽

Vol 51 ◽

pp. 1116-1117

Author(s):

C. S. Lin ◽

W. A. Chiou ◽

M. Meshii

Keyword(s):

Intermetallic Compound ◽

Reaction Rate ◽

Diffusion Rate ◽

Early Stage ◽

Zinc Bath ◽

Steel Sheets ◽

Direct Observations ◽

Solid Iron ◽

Iron And Zinc ◽

Ternary Intermetallic Compound

The galvannealed steel sheets have received ever increased attention because of their excellent post-painting corrosion resistance and good weldability. However, its powdering and flaking tendency during press forming processes strongly impairs its performance. In order to optimize the properties of galvanneal coatings, it is critical to control the reaction rate between solid iron and molten zinc.In commercial galvannealing line, aluminum is added to zinc bath to retard the diffusion rate between iron and zinc by the formation of a thin layer of Al intermetallic compound on the surface of steel at initial hot-dip galvanizing. However, the form of this compound and its transformation are still speculated. In this paper, we report the direct observations of this compound and its transformation.The specimens were prepared in a hot-dip simulator in which the steel was galvanized in the zinc bath containing 0.14 wt% of Al at a temperature of 480 °C for 5 seconds and was quenched by liquid nitrogen.

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Anisotropy of interfacial defects in the initial stage of MOVPE GaAs growth On Si

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176095 ◽

1990 ◽

Vol 48 (4) ◽

pp. 592-593

Author(s):

C. Vannuffel ◽

C. Schiller ◽

J. P. Chevalier

Keyword(s):

Early Stage ◽

Threading Dislocations ◽

Mbe Growth ◽

Detailed Mechanism ◽

Si Substrates ◽

Initial Stage ◽

Interfacial Defects ◽

Interfacial Dislocations ◽

Step Growth ◽

Essential Problem

Recently, interest has focused on the epitaxy of GaAs on Si as a promising material for electronic applications, potentially for integration of optoelectronic devices on silicon wafers. The essential problem concerns the 4% misfit between the two materials, and this must be accommodated by a network of interfacial dislocations with the lowest number of threading dislocations. It is thus important to understand the detailed mechanism of the formation of this network, in order to eventually reduce the dislocation density at the top of the layers.MOVPE growth is carried out on slightly misoriented, (3.5°) from (001) towards , Si substrates. Here we report on the effect of this misorientation on the interfacial defects, at a very early stage of growth. Only the first stage, of the well-known two step growth process, is thus considered. Previously, we showed that full substrate coverage occured for GaAs thicknesses of 5 nm in contrast to MBE growth, where substantially greater thicknesses are required.

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