scholarly journals β-Zeolite Assisted Lignin-First Fractionation in a Flow-Through Reactor

2021 ◽  
Author(s):  
Alexei Kramarenko ◽  
Deniz Etit ◽  
G. Laudadio ◽  
Fernanda Neira Dangelo
Keyword(s):  
Structural Changes ◽  
Catalyst Deactivation ◽  
Acid Sites ◽  
Catalyst Recycling ◽  
Mixed Regime ◽  
Rate Limiting Step ◽  
Lignocellulosic Feedstocks ◽  
One Step ◽  
Flow Through ◽  
Aromatic Monomer

<p>Lignin is one of the main constituents of lignocellulosic biomass, whose valorization is essential for an economically feasible biorefinery process scheme[1]. In the present work, a hydrogen-free one step catalytic fractionation of woody biomass using commercial b-zeolite as catalyst in a flow-through reactor was carried out, leading to a maximum aromatic monomer yield of 20.5 wt.%. Birch, spruce and walnut shells were used and compared as lignocellulosic feedstocks. Relevant insights in the reaction mechanism were obtained through 2D HSQC NMR analysis, revealing that b-O-4 cleavage is catalyzed by the zeolite. To optimize system operation, a rate limiting step analysis was performed by using different reactor configurations. It was found that the system operated in a mixed regime where the rates of both solvolytic delignification and zeolite-based depolymerization/dehydration affect the net rate of aromatic monomer production. Oxalic acid addition was found to enhance monomer production at moderate concentrations by improving solvolysis; however, it caused structural changes to the zeolite leading to lower monomer yields at higher concentrations. Zeolite stability was assessed through catalyst recycling and characterization using NH<sub>3</sub>-TPD, XRD, N<sub>2</sub> physisorption and TGA. Main catalyst deactivation mechanisms were found to be coking and leaching, respectively leading to larger pore size and lower concentration of acid sites.</p>

scholarly journals β-Zeolite Assisted Lignin-First Fractionation in a Flow-Through Reactor

2021 ◽  
Author(s):  
Alexei Kramarenko ◽  
Deniz Etit ◽  
G. Laudadio ◽  
Fernanda Neira Dangelo
Keyword(s):  
Structural Changes ◽  
Catalyst Deactivation ◽  
Acid Sites ◽  
Catalyst Recycling ◽  
Mixed Regime ◽  
Rate Limiting Step ◽  
Lignocellulosic Feedstocks ◽  
One Step ◽  
Flow Through ◽  
Aromatic Monomer

<p>Lignin is one of the main constituents of lignocellulosic biomass, whose valorization is essential for an economically feasible biorefinery process scheme[1]. In the present work, a hydrogen-free one step catalytic fractionation of woody biomass using commercial b-zeolite as catalyst in a flow-through reactor was carried out, leading to a maximum aromatic monomer yield of 20.5 wt.%. Birch, spruce and walnut shells were used and compared as lignocellulosic feedstocks. Relevant insights in the reaction mechanism were obtained through 2D HSQC NMR analysis, revealing that b-O-4 cleavage is catalyzed by the zeolite. To optimize system operation, a rate limiting step analysis was performed by using different reactor configurations. It was found that the system operated in a mixed regime where the rates of both solvolytic delignification and zeolite-based depolymerization/dehydration affect the net rate of aromatic monomer production. Oxalic acid addition was found to enhance monomer production at moderate concentrations by improving solvolysis; however, it caused structural changes to the zeolite leading to lower monomer yields at higher concentrations. Zeolite stability was assessed through catalyst recycling and characterization using NH<sub>3</sub>-TPD, XRD, N<sub>2</sub> physisorption and TGA. Main catalyst deactivation mechanisms were found to be coking and leaching, respectively leading to larger pore size and lower concentration of acid sites.</p>

scholarly journals β-Zeolite Assisted Lignin-First Fractionation in a Flow-Through Reactor

2021 ◽  
Author(s):  
Alexei Kramarenko ◽  
Deniz Etit ◽  
G. Laudadio ◽  
Fernanda Neira Dangelo
Keyword(s):  
Structural Changes ◽  
Catalyst Deactivation ◽  
Acid Sites ◽  
Catalyst Recycling ◽  
Mixed Regime ◽  
Rate Limiting Step ◽  
Lignocellulosic Feedstocks ◽  
One Step ◽  
Flow Through ◽  
Aromatic Monomer

<p>Lignin is one of the main constituents of lignocellulosic biomass, whose valorization is essential for an economically feasible biorefinery process scheme. In the present work, a hydrogen-free one step catalytic fractionation of woody biomass using commercial b-zeolite as catalyst in a flow-through reactor was carried out, leading to a maximum aromatic monomer yield of 20.5 wt.%. Birch, spruce and walnut shells were used and compared as lignocellulosic feedstocks. Relevant insights in the reaction mechanism were obtained through 2D HSQC NMR analysis, revealing that b-O-4 cleavage is catalyzed by the zeolite. To optimize system operation, a rate limiting step analysis was performed by using different reactor configurations. It was found that the system operated in a mixed regime where the rates of both solvolytic delignification and zeolite-based depolymerization/dehydration affect the net rate of aromatic monomer production. Oxalic acid addition was found to enhance monomer production at moderate concentrations by improving solvolysis; however, it caused structural changes to the zeolite leading to lower monomer yields at higher concentrations. Zeolite stability was assessed through catalyst recycling and characterization using NH<sub>3</sub>-TPD, XRD, N<sub>2</sub> physisorption and TGA. Main catalyst deactivation mechanisms were found to be coking and leaching, respectively leading to larger pore size and lower concentration of acid sites.</p>

An analytical microscopic study of metals in fluidized catalytic cracking catalyst

1986 ◽  
Vol 44 ◽  
pp. 854-855
Author(s):  
Clifford S. Rainey
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
Catalytic Cracking ◽  
Catalyst Deactivation ◽  
Coke Formation ◽  
Acid Sites ◽  
Y Zeolite ◽  
Fcc Catalyst ◽  
Fluidized Catalytic Cracking ◽  
High Regeneration

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.

European Welfare State Constitutions after the Financial Crisis

2020 ◽  
Keyword(s):  
Financial Crisis ◽  
Structural Changes ◽  
Social Protection ◽  
Welfare States ◽  
Constitutional Review ◽  
State Constitutions ◽  
Social Law ◽  
European Welfare State ◽  
One Step ◽  
Recent Financial Crisis

At a time when Europe is in the grip of a new crisis, it is especially useful to look back at the experiences of the European welfare states’ constitutions during the most recent financial crisis. This book provides unique insights by analysing social protection reforms undertaken in nine European countries, from both a social law and a constitutional law perspective. It highlights the mixture of short-term cuts in benefits and of structural changes in social protection schemes. The crisis might have helped to further the partial and temporary implementation of reforms, but it certainly cannot spare us from the debates and political compromises that are unavoidable in order to reform social protection thoughtfully and thoroughly. Moreover, the book records the outcome of relevant constitutional review proceedings and thereby demonstrates that, even if corrections remained restricted to relatively few cases, social rights matter. The financial crisis advanced their protection one step further, but left many questions open. One lesson is of paramount importance, also for helping us overcome the current pandemic crisis: we need a substantial and commonly accepted agreement in the Europe Union on how to balance the economy and social protection in the future.

scholarly journals Monolithic integration of nanorod arrays on microfluidic chips for fast and sensitive one-step immunoassays

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ye Wang ◽  
Jiongdong Zhao ◽  
Yu Zhu ◽  
Shurong Dong ◽  
Yang Liu ◽  
...  
Keyword(s):  
Troponin I ◽  
Specific Antigen ◽  
Monolithic Integration ◽  
Detection Sensitivity ◽  
Quantitative Detection ◽  
Plasmonic Nanostructures ◽  
Nanorod Arrays ◽  
Microfluidic Chips ◽  
One Step ◽  
Flow Through

AbstractHere, we present integrated nanorod arrays on microfluidic chips for fast and sensitive flow-through immunoassays of physiologically relevant macromolecules. Dense arrays of Au nanorods are easily fabricated through one-step oblique angle deposition, which eliminates the requirement of advanced lithography methods. We report the utility of this plasmonic structure to improve the detection limit of the cardiac troponin I (cTnI) assay by over 6 × 105-fold, reaching down to 33.9 fg mL−1 (~1.4 fM), compared with an identical assay on glass substrates. Through monolithic integration with microfluidic elements, the device enables a flow-through assay for quantitative detection of cTnI in the serum with a detection sensitivity of 6.9 pg mL−1 (~0.3 pM) in <6 min, which was 4000 times lower than conventional glass devices. This ultrasensitive detection arises from the large surface area for antibody conjugation and metal-enhanced fluorescent signals through plasmonic nanostructures. Moreover, due to the parallel arrangement of flow paths, simultaneous detection of multiple cancer biomarkers, including prostate-specific antigen and carcinoembryonic antigen, has been fulfilled with increased signal-to-background ratios. Given the high performance of this assay, together with its simple fabrication process that is compatible with standard mass manufacturing techniques, we expect that the prepared integrated nanorod device can bring on-site point-of-care diagnosis closer to reality.

Stability of carbon monoxide oxidation process on gold nanoparticles

2020 ◽  
Vol 8 (1) ◽  
pp. 116-124
Author(s):  
P. P. Kostrobij ◽  
◽  
I. A. Ryzha ◽  
Keyword(s):  
Carbon Monoxide ◽  
Gold Nanoparticles ◽  
Reaction Mechanisms ◽  
Structural Changes ◽  
Oxidation Process ◽  
Lyapunov Method ◽  
Catalyst Surface ◽  
Carbon Monoxide Oxidation ◽  
One Step ◽  
The Stability

The stability conditions for mathematical models of carbon monoxide oxidation on the surface of gold nanoparticles are investigated. The cases of reaction mechanisms of one-step and step-by-step transformation of reagents are consecutively considered. Using the stability analysis by Lyapunov method, it is shown that models which take into account the possibility of structural changes of the catalyst surface can predict the occurrence of oscillatory mode in the system as a result of Hopf instability.

Zeolite Supported Bimetallic Catalyst System: The Effect of Metal Loading for Catalytic Pyrolysis of Jatropha Residue

2017 ◽  
Vol 751 ◽  
pp. 494-499
Author(s):  
Vituruch Goodwin ◽  
Phanwatsa Amnaphiang ◽  
Pimpreeya Thungngern ◽  
Kong Kah Shin ◽  
Parncheewa Udomsap ◽  
...  
Keyword(s):  
Bimetallic Catalysts ◽  
Catalytic Pyrolysis ◽  
Bimetallic Catalyst ◽  
Supported Catalysts ◽  
Acid Sites ◽  
One Step ◽  
Step Loading ◽  
Loading Sequence ◽  
Xrd Patterns ◽  
The One

Two transition metals were loaded on H-ZSM-5 zeolite to produce bimetallic zeolite supported catalysts for catalytic pyrolysis reaction. Ni and Co metal were loaded on H-ZSM-5 via wet impregnation method. The loading sequence was applied using one-step and two-step loading method. The different loading sequence affect surface properties of catalyst and catalytic activity in pyrolysis reaction. The bimetallic catalysts were prepared at Ni+Co metal loading content of 10+10 wt% (Ni:Co=1:1) to 10+20 wt% (Ni:Co=1:2 or 2:1). All bimetallic catalysts supported on H-ZSM-5 were calcined and characterized by X-ray Diffraction (XRD), Surface area analysis (BET) and Temperature Programmed Desorption of ammonia (NH3-TPD). The XRD patterns of bimetallic zeolite supported catalysts revealed that loading of two metals at high content affect crystalline structural of ZSM-5 support. All XRD patterns illustrated peaks characteristic of ZSM-5, cobalt oxide and nickel oxide. The NH3-TPD results showed number of acid sites of the catalyst which revealed that the acid sites of ZSM-5 support was weakened with transition metal added. The two-step loading of 10+20 wt% metals on ZSM-5 reduced the peak intensities of NH3 desorption due to the metal particles aggregate on acid sites of ZSM-5. The two-step 10+20 wt% bimetallic catalysts has the lowest surface acidity, followed by the one-step 10+20 wt%, the two-step 10+10 wt% and the one-step 10+10 wt% bimetallic catalysts, respectively. Jatropha residue was used for catalytic pyrolysis study. Jatropha residue and bimetallic catalyst was pyrolyzed at 500 °C in a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The product vapor was analyzed by GC/MS for the different groups of organic products such as fatty acid, aldehydes, ketones, aliphatic hydrocarbons, aromatic hydrocarbons and nitrogen compounds. The product from catalytic pyrolysis of jatropha residue with bimetallic zeolite supported catalysts enhance deoxygenation reaction that resulted in high aliphatic and aromatic hydrocarbons product. The one-step loading at ratio Ni:Co = 1:1 (10+10 wt%) gave the highest hydrocarbons product yield at 57.81%.

Deterministic Tree Networks for River Drainage Basins

Fractals ◽  
1998 ◽  
Vol 06 (03) ◽  
pp. 245-261 ◽  
Author(s):  
M. R. Errera ◽  
A. Bejan
Keyword(s):  
Porous Medium ◽  
Flow Resistance ◽  
Drainage Basin ◽  
Drainage Basins ◽  
River Drainage ◽  
One Step ◽  
Local Properties ◽  
Flow Through ◽  
Internal Properties ◽  
Flow Medium

This paper shows that the dendritic patterns formed by low-resistance channels in a river drainage basin are reproducible and can be deduced from a single principle that acts at every step in the development of the pattern: the constrained minimization of global resistance in area-to-point flow. The river basin is modeled as a two-dimensional territory with Darcy flow through a saturated heterogeneous porous medium with uniform flow addition per unit area. From one step to the next, small elements of the porous medium are dislodged and removed in ways that minimize the global flow resistance. The removed elements are replaced by channels with lower flow resistance. The channels form a dendritic pattern that is deterministic, not random. The finest details of this structure are sensitive to internal properties and external forcing, i.e. variations in the local properties of the flow medium, and the manner in which the total area-to-point flow rate varies as the structure develops. Remarkably insensitive to such effects are the basic type and rough size of the flow structure (channels versus no channels, dendrite, number of branches) and the minimized global resistance to flow.

Regurgitant Commissure Flow Through a Closed Polymeric Heart Valve

2010 ◽  
Author(s):  
Scott C. Corbett ◽  
Hamid N.-Hashemi ◽  
Ahmet U. Coskun
Keyword(s):  
Heart Valve ◽  
Heart Valves ◽  
Structural Changes ◽  
Patient Survival ◽  
Improve Patient Survival ◽  
Flow Disturbances ◽  
Limited Life ◽  
Flow Through ◽  
Valve Prostheses ◽  
Improve Patient

While heart valve prostheses have been used successfully since 1960, outcomes are far from ideal. The underlying problem with bioprostheses is a limited life from structural changes such as calcification and leaflet wear, leading to valve failure. The underlying problem with mechanical heart valves is the presence of flow disturbances which necessitate anticoagulation. A polyurethane valve has the potential to improve upon the shortcomings of existing valves and ultimately improve patient survival.

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