scholarly journals Conversion of Fructose to HMF in a Continuous Fixed Bed Reactor with Outstanding Selectivity

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1802 ◽  
Author(s):  
Eric Weingart ◽  
Sarah Tschirner ◽  
Linda Teevs ◽  
Ulf Prüße
Keyword(s):  
Large Scale ◽  
Continuous Process ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Water Addition ◽  
Batch Systems ◽  
Formation Conditions ◽  
High Yields ◽  
Optimized Conditions ◽  
By Products

5-Hydroxymethylfurfural (HMF) is a very promising component for bio-based plastics. Efficient synthesis of HMF from biomass is still challenging because of fast degradation of HMF to by-products under formation conditions. Therefore, different studies, conducted mainly in monophasic and biphasic batch systems with and without water addition have been published and are still under investigation. However, to produce HMF at a large scale, a continuous process is preferable. Until now, only a few studies have been published in this context. In this work, it is shown that fluorous alcohol hexafluoroisopropanol (HFIP) can act as superior reaction solvent for HMF synthesis from fructose in a fixed bed reactor. Very high yields of 76% HMF can be achieved in this system under optimized conditions, whilst the catalyst is very stable over several days. Such high yields are only described elsewhere with high boiling reaction solvents like dimethylsulfoxide (DMSO), whereas HFIP with a boiling point of 58 °C is very easy to separate from HMF.

Synthesis of [18F]FAZA Using Nosyl and Iodo Precursors for Nucleophilic Radiofluorination

2019 ◽  
Vol 12 (1) ◽  
pp. 49-57
Author(s):  
William Sun ◽  
Cheryl Falzon ◽  
Ebrahim Naimi ◽  
Ali Akbari ◽  
Leonard I. Wiebe ◽  
...  
Keyword(s):  
Large Scale ◽  
Side Reactions ◽  
Automated Synthesis ◽  
Complex Reaction ◽  
Chemical Structures ◽  
Standardized Protocol ◽  
High Yields ◽  
Automated Procedures ◽  
Optimized Conditions ◽  
By Products

Background: 1-&#945;-D-(5-Deoxy-5-[18F]fluoroarabinofuranosyl)-2-nitroimidazole ([18F]FAZA) is manufactured by nucleophilic radiofluorination of 1-&#945;-D-(2’,3’-di-O-acetyl-5’-O-toluenesulfonylarabinofuranosyl)- 2-nitroimidazole (DiAcTosAZA) and alkaline deprotection to afford [18F]FAZA. High yields (>60%) under optimized conditions frequently revert to low yields (<20%) in large scale, automated syntheses. Competing side reactions and concomitant complex reaction mixtures contribute to substantial loss of product during HPLC clean-up. Objective: To develop alternative precursors for facile routine clinical manufacture of [18F]FAZA that are compatible with current equipment and automated procedures. Methods: Two new precursors, 1-&#945;-D-(2’,3’-di-O-acetyl-5’-O-(4-nitrobenzene)sulfonyl-arabinofuranosyl)-2- nitroimidazole (DiAcNosAZA) and 1-&#945;-D-(2’,3’-di-O-acetyl-5’-iodo-arabinofuranosyl)-2-nitroimidazole (DiAcIAZA), were synthesized from commercially-available 1-&#945;-D-arabinofuranosyl-2-nitroimidazole (AZA). A commercial automated synthesis unit (ASU) was used to condition F-18 for anhydrous radiofluorination, and to radiofluorinate DiAcNosAZA and DiAcIAZA using the local standardized protocol to manufacture [18F]FAZA from AcTosAZA. Results: DiAcNosAZA was synthesized via two pathways, in recovered yields of 29% and 40%, respectively. The nosylation of 1-&#945;-D-(2’,3’-di-O-acetyl-arabinofuranosyl)-2-nitroimidazole (DiAcAZA) featured a strong competing reaction that afforded 1-&#945;-D-(2’,3’-di-O-acetyl-5’-chloro-arabinofuranosyl)-2- nitroimidazole (DiAcClAZA) in 55% yield. Radiofluorination yields were better from DiAcNosAZA and DiAcIAZA than from DiAcTosAZA, and the presence of fewer side products afforded higher purity [18F]FAZA preparations. Several radioactive and non-radioactive by products of radiofluorination were assigned tentative chemical structures based on co-chromatography with authentic reference compounds. Conclusion: DiAcClAZA, a major side-product in the preparation of DiAcNosAZA, and its deprotected analogue (ClAZA), are unproven hypoxic tissue radiosensitizers. DiAcNosAZA and DiAcIAZA provided good radiofluorination yields in comparison to AcTosAZA and could become preferred [18F]FAZA precursors if the cleaner reactions can be exploited to bypass HPLC purification.

scholarly journals Pyrolysis Characteristics of Undervalued Wood Varieties in the Portuguese Charcoal Sector

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2537
Author(s):  
Felix Charvet ◽  
Felipe Silva ◽  
Luís Ruivo ◽  
Luís Tarelho ◽  
Arlindo Matos ◽  
...  
Keyword(s):  
Large Scale ◽  
Fixed Bed ◽  
Management Control ◽  
Fixed Bed Reactor ◽  
Fuel Load ◽  
Charcoal Production ◽  
Pyrolysis Characteristics ◽  
Major Market ◽  
Burnt Wood ◽  
Fuel Particles

Charcoal production in Portugal is mostly based on the valorization of woody residues from cork oak and holm oak, the latter being considered a reference feedstock in the market. Nevertheless, since wildfire prevention became a priority in Portugal, after the recent dramatic wildfires, urgent actions are being conducted to reduce the fuel load in the forests, which is increasing the amount of biomass that is available for valorization. Additionally, biomass residues from agriculture, forest management, control of invasive species, partially burnt wood from post-fire recovery actions, and waste wood from storm devastated forests need also to be considered within the national biomass valorization policies. This has motivated the present work on whether the carbonization process can be used to valorize alternative woody biomasses not currently used on a large scale. For this purpose, slow pyrolysis experiments were carried out with ten types of wood, using a fixed bed reactor allowing the controlled heating of large fuel particles at 0.1 to 5 °C/min and final temperatures within 300–450 °C. Apart from an evaluation of the mass balance of the process, emphasis was given to the properties of the resulting charcoals considering its major market in Portugal—barbecue charcoal for both recreational and professional purposes.

Kinetics of Camphene Esterification to Isobornyl Acetate

2011 ◽  
Vol 233-235 ◽  
pp. 990-998 ◽  
Author(s):  
Dian Hua Liu ◽  
Ding Ye Fang ◽  
Qin Qin Guan ◽  
A Jian Tao
Keyword(s):  
Acetic Acid ◽  
Kinetic Model ◽  
Continuous Process ◽  
Fixed Bed ◽  
Space Velocity ◽  
Batch Process ◽  
Fixed Bed Reactor ◽  
Feed Ratio ◽  
Continuous Reaction ◽  
Kinetics Of

The conventional process for isobornyl acetate synthesis from camphene and acetic acid is a batch process. The purpose of this paper is to synthesize isobornyl acetate in continuous process in a fixed bed reactor. The continuous reaction conditions were studied. The experiment was put into practice under the following conditions: 35-45, camphene/acetic acid feed ratio(wt%) from 1 to 2 and space velocity from 0.6 to 1.8 h-1. A kinetic model was developed which describes the experimental data well. A pilot fixed reactor was simulated by using the kinetic model.

Effect of Steam Treatment on Catalytic Performance of La2O3-HZSM-5 for Methylation of Toluene with Methanol

2012 ◽  
Vol 629 ◽  
pp. 381-385 ◽  
Author(s):  
Jun Hui Li ◽  
Zhong Hua Hu ◽  
Ya Nan Wang ◽  
Hao Xiang ◽  
Zhi Rong Zhu
Keyword(s):  
High Selectivity ◽  
Fixed Bed ◽  
Shape Selectivity ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Fixed Bed Reactor ◽  
Steam Treatment ◽  
By Products ◽  
Poor Stability ◽  
Excellent Catalytic Performance

Methylation of toluene with methanol to synthesize p-Xylene was performed in a fixed-bed reactor. HZSM-5 zeolite as a catalyst was prepared by modification with La2O3. In addition, effect of steam treatment for La2O3-modified HZSM-5 on its catalytic performance was investigated as well. The properties of as-prepared catalysts were characterized by XRD, BET and NH3-TPD. The results indicate that modification with La2O3can narrow the size of HZSM-5 channel effectively. And more than 90% selectivity of p-Xylene is obtained over HZSM-5 with loading of 24% and 30% La2O3. However, above La2O3-modified HZSM-5 with high-selectivity exhibit a poor stability for time on-stream of the methylation reaction. Steam treatment of La2O3-modified HZSM-5 can improve its stability and shape selectivity, decreasing by-products. These effects can be attributed to distortion & narrowing of HZSM-5 channel and reduction of HZSM-5 strong Bronsted acid sites during steam treatment. As a result, the excellent catalytic performance is obtained over 24.0% La2O3-modified HZSM-5 by steam treatment at 773 K for 1.0 h, being 23% conversion of toluene, 93% selectivity of p-Xylene during time on-stream.

scholarly journals Condensation By-Products in Wet Peroxide Oxidation: Fouling or Catalytic Promotion? Part II: Activity, Nature and Stability

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 518 ◽  
Author(s):  
Asunción Quintanilla ◽  
Jose L. Diaz de Tuesta ◽  
Cristina Figueruelo ◽  
Macarena Munoz ◽  
Jose A. Casas
Keyword(s):  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Intrinsic Activity ◽  
Peroxide Oxidation ◽  
Air Oxidation ◽  
Carbonaceous Deposits ◽  
Wet Peroxide Oxidation ◽  
By Products

The deposition of condensation by-products onto the catalyst surface upon wet peroxide and wet air oxidation processes has usually been associated with catalyst deactivation. However, in Part I of this paper, it was demonstrated that these carbonaceous deposits actually act as catalytic promoters in the oxygen-assisted wet peroxide oxidation (WPO-O2) of phenol. Herein, the intrinsic activity, nature and stability of these species have been investigated. To achieve this goal, an up-flow fixed bed reactor packed with porous Al2O3 spheres was used to facilitate the deposition of the condensation by-products formed in the liquid phase. It was demonstrated that the condensation by-products catalyzed the decomposition of H2O2 and a higher amount of these species leads to a higher degree of oxidation degree The reaction rates, conversion values and intermediates’ distribution were analyzed. The characterization of the carbonaceous deposits on the Al2O3 spheres showed a significant amount of condensation by-products (~6 wt.%) after 650 h of time on stream. They are of aromatic nature and present oxygen functional groups consisting of quinones, phenols, aldehydes, carboxylics and ketones. The initial phenol concentration and H2O2 dose were found to be crucial variables for the generation and consumption of such species, respectively.

scholarly journals Direct synthesis of dimethyl carbonate and propylene glycol using potassium bicarbonate as catalyst in supercritical CO2

2015 ◽  
Vol 17 (1) ◽  
pp. 62-65 ◽  
Author(s):  
Yicun Wen ◽  
Rui Zhang ◽  
Yu Cang ◽  
Jianchao Zhang ◽  
Lixiao Liu ◽  
...  
Keyword(s):  
Propylene Glycol ◽  
Propylene Oxide ◽  
Large Scale ◽  
Dimethyl Carbonate ◽  
Direct Synthesis ◽  
Potassium Bicarbonate ◽  
One Pot ◽  
Optimized Conditions ◽  
First Time ◽  
By Products

Abstract The improved one-pot synthesis of dimethyl carbonate and propylene glycol from propylene oxide, supercritical carbon dioxide, and methanol with potassium bicarbonate as the catalyst has been reported in this paper. As far as we know, it is the first time to use potassium bicarbonate only as the catalyst in the production process which is simple and cheap. Satisfactory conversion rate of propylene oxide and yield of the products could be achieved at the optimized conditions with quite a small amount of by-products. Our new method offers an attractive choice for the production of dimethyl carbonate in large-scale industry efficiently and environmental friendly.

Design and Optimization of a Fixed Bed Reactor for Direct Dimethyl Ether Production from Syngas Using Differential Evolution Algorithm

2013 ◽  
Vol 11 (1) ◽  
pp. 147-158 ◽  
Author(s):  
Reza Vakili ◽  
Reza Eslamloueyan
Keyword(s):  
Differential Evolution ◽  
Dimethyl Ether ◽  
Large Scale ◽  
Homogeneous Model ◽  
Fixed Bed ◽  
Differential Evolution Algorithm ◽  
Operating Conditions ◽  
Fixed Bed Reactor ◽  
Scale Production ◽  
Design And Optimization

Abstract Dimethyl ether (DME) is traditionally produced by methanol dehydration in an adiabatic reactor. Recently, a more economical method has been proposed to produce DME in a reactor in which methanol production and dehydration take place simultaneously on a bi-functional catalyst. In the present study, the design and optimization of an industrial scale fixed bed reactor for the direct synthesis of DME from syngas are investigated. A steady state, pseudo-homogeneous model has been applied to simulate the proposed reactor. At first, the preliminary design of the reactor is done based on the reactor design heuristics for industrial reactors. Then, using differential evolution (DE) algorithm as a fast and efficient optimization method, the tentative reactor operating conditions and its internal configuration are optimized. The objective of the optimization is to maximize DME production in each tube of the reactor. The number of tubes, feed inlet and coolant water temperatures are considered as decision variables of the optimization algorithm. At the optimum conditions, the reactor size decreases due to increase of CO conversion and DME productivity in each tube. The results show that the proposed optimum reactor is more economical for large-scale production of DME in comparison to the conventional industrial DME reactor.

Cyclic CO2 Capture Behavior of Limestone Modified by Qinghai Lake Salt During Long-Term Calcium Looping Cycles

2017 ◽  
Author(s):  
Yongqing Xu ◽  
Haoran Ding ◽  
Cong Luo ◽  
Ying Zheng ◽  
Qiyao Wang ◽  
...  
Keyword(s):  
Co2 Capture ◽  
Large Scale ◽  
Salt Water ◽  
Fixed Bed ◽  
Cost Effective ◽  
Sem Analysis ◽  
Fixed Bed Reactor ◽  
Qinghai Lake ◽  
Impregnation Method

A modified sorbent was prepared by a novel hydration-impregnation method. Results indicated that hydrating with salt water can obtain enhanced capacity of the sorbents during multiple calcination/carbonation reactions. After 40 cycles, the modified limestone sorbent doped with 2wt% lake salt remained a CO2 capture capacity of 0.34 g of CO2 of sorbent, which was 150% higher than that of natural limestone. XRF and XRD were tested for analyzing the chemical component of the sorbents. A Fixed-bed reactor was applied to test the absorption characteristics of those sorbents. SEM analysis revealed that macropores in this novel sorbent were relatively stable during long-term cycles. A preliminary economic analysis of different modified calcium-based sorbents was conducted, and the results demonstrated that limestone modified by lake salt is a promising scheme for large-scale sorbent production, which is a well cost-effective and pollution free scenario suitable for industrial promotion. (CSPE)

Enhancement of DME Production in an Optimized Membrane Isothermal Fixed-Bed Reactor

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohammad Farsi ◽  
Abdolhossein Jahanmiri
Keyword(s):  
Membrane Reactor ◽  
Large Scale ◽  
Fixed Bed ◽  
Water Concentration ◽  
Methanol Conversion ◽  
Fixed Bed Reactor ◽  
Scale Production ◽  
Light Pressure ◽  
Steady State Condition ◽  
Catalyst Pellets

Dimethyl ether is a colorless gas at the ambient condition that is easily liquefied under light pressure. Currently, DME as a green fuel has been suggested as one of the most promising candidates for substitution of LPG and diesel fuel. In this paper, a water cooled membrane fixed bed reactor is proposed and modeled heterogeneously for large scale production of DME from methanol dehydration. The proposed reactor is modeled one-dimensionally based on mass and energy conservation laws at steady state condition. Also, the efficacy of the proposed membrane reactor is investigated and the results of the proposed reactor are compared with an isothermal and commercial adiabatic reactor. The simulation results of the proposed membrane reactor indicate that the methanol conversion is improved about 6.2 percent compared to the conventional industrial reactor. Also, water vapor removal from reaction zone in the membrane reactor yields lower water concentration over the catalyst pellets and higher quality of outlet product. These can lead to higher catalyst lifetime and lower cost in purification stage.

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