1,721,011 research outputs found
The chemistry of resorcinol carboxylation and its possible application to the CO2 removal from exhaust gases
No full textThe carbon dioxide uptake by resorcinol solutions has been investigated under different operational procedures and experimental conditions. Batch experiments have been carried out in aqueous and glycerol-water solutions of KOH, KHCO3 or K2CO3, and the yield of resorcinol carbonatation has been investigated as a function of the CO2 partial pressure as well as reaction temperature and time. The β-resorcylic acid (2,4-dihydroxy benzoic acid) has been isolated in the solid state and identified on the basis of its IR spectrum. The 13C NMR analysis has been applied to identify and quantify the carbonated species in solution upon CO2 uptake and after thermal resorcinol regeneration. The maximum yield of resorcinol conversion into β-resorcylic acid was 60% with 1.0 bar of CO2 and 120 min reaction time at 110 °C. A 34% yield of resorcinol conversion was also obtained with the resorcinol/K2CO3 solution in the absence of CO2. A relationship between the CO2 absorption capacity and the possible mechanism of CO2 capture has been proposed. The CO2 absorption efficiency from a simulated flue gases (15% CO2 in air) has been measured in continuous cycles of CO2 absorption-desorption carried out in packed columns and with a glycerol-water solution of resorcinol/KOH/KHCO3. The maximum absorption efficiency was 82% at absorption-desorption temperatures of 70 °C and, respectively, 170 °C. Oxidative conditions and the presence of H2S did not affect the yield of β-resorcylic acid and the resorcinol capacity of CO2 capture. Finally, a simple method for the selective separation of H2S from CO2 has been reported. © 2015 Elsevier Ltd. All rights reserved
Metodo di Cattura Selettivo della CO2
No full textLa resorcina, o resorcinolo, è un composto organico che è in grado di re
a
gire, in condizioni
piuttosto blande
, con la anidride carbonica
. Il prodotto della reazione è un acido idrossicarbossilico
dotato di apprezzabile stabilità. Questo prodotto è il risultato della fissazione della CO
2
nell’anello
aromatico della resorcina. Quando l’acido idrossi
carbossilico viene scaldato, rilascia la CO
2
e
ripristina la resorcina.
La sequenza ora brevemente descritta rappresenta l’oggetto della presente invenzione che propone
un nuovo metodo per assorbire la CO
2
presente negli effluenti gassosi provenienti dai g
rossi
impianti di combustione. L’invenzione propone un metodo selettivo per l’assorbimento della CO
2
che fornisce quindi, nella successiva fase di rilascio, un flusso di sola anidride carbonica. La
semplicità delle fasi del processo lo rendono particolarme
nte adatto all’impiego ciclico poiché alla
fine delle due fasi di assorbimento
-
desorbimento il reagente viene ripristinato.
Le fasi del processo oggetto del presente brevetto possono essere schematizzate alla seguente
maniera:
1.
Assorbimento della CO
2
median
te reazione a caldo (100
–
200 °C) con la resorcina sciolta in
una soluzione acquosa di un idrossido alcalino (NaOH o KOH).
Il prodotto della reazione è
un acido diidrossibenzoico chiamato acido resorcinico.
2.
Interruzione del flusso di CO
2
ed aumento della
temperatura (200
–
300 °C) per desorbire la
CO
2
e ripristinare la resorcina.
La reazione di desorbimento può essere effettuata sia nello stesso reattore della reazione di
assorbimento che in altro ambiente; inoltre può essere effettuata sia direttamente su
l prodotto della
carbossilazione (il sale dell’acido resorcinico) che sul’acido resorcinico (solido) ottenuto per
acidificazione della miscela di reazione
Kinetic parameter estimation for methanol dehydration to dimethyl ether over sulfonic and polymeric acid catalysts
No full textBACKGROUND: The methanol dehydration to dimethyl ether (DME) has received considerable attention in the literature, because of its potential use as a multipurpose fuel. A wide literature of kinetic studies is available for γ-Al2O3, reference commercial catalyst but only a few authors report a kinetic analysis of attractive and alternative catalysts to γ-Al2O3 in DME production. The aim of this work was to contribute in this direction, by performing a catalytic test focused on the determination of kinetic parameters for methanol dehydration over sulfonic acid catalysts and polymeric materials. RESULTS: The catalytic and kinetic behavior of these materials for the methanol to DME dehydration reaction has been investigated using a fixed bed reactor at total pressure of 1 bar within a temperature range of 50 to 450 °C. The sulfonated fluoropolymer (Aquivion) exhibited the highest activity and stability for the dehydration reaction at relatively low temperatures at which the γ-Al2O3 did not display any dehydration activity. The tested catalysts showed good time stability when both methanol and methanol/water mixtures were used as feed reactants. Good agreement was achieved between experimental data and the proposed model. CONCLUSION: The -SO3H groups enhanced the surface acidity and the catalytic performances. The sulfonated perfluorinated polymer (Aquivion) was able to catalyze the methanol/DME conversion at temperatures as low as 90 °C. The selectivity to DME at lower temperatures was 100%. Apparent activation energy for this reaction was experimentally evaluated to 110 KJ/mol and theoretical calculated to 96 KJ/mol: there was a comparable and good agreement with the experimental data. © 2020 Society of Chemical Industry
Chemically Enhanced Separation of H2S04/HI Mixtures from the Bunsen Reaction in the Sulfur−Iodine Thermochemical Cycle
No full textDevelopment of sulfonic supported acids and their application in power to gas systems
Full text linkDimethyl ether (DME) is an environmentally friendly fuel that is being widely considered as an alternative fuel to replace petroleum fuels. DME can be produced by dehydration reaction of methanol by using solid catalysts in catalytic reactions. This study shows the influence of catalyst's surface acidity on the catalytic activity in the dehydration of methanol to DME. In this work, the conversion of methanol to dimethyl ether has been investigated using a continuous flow fixed-bed reactor at temperatures between 60°C and 350°C and 1 bar. Sulfonated catalysts with-SO3H acid function were tested and compared with conventional catalysts as γ-Al2O3. SiO2, MCM-41 and fluoropolymer were used as inorganic and organic supports for sulfonic groups. The experimental results demonstrate a good catalytic activity for the functionalized MCM-41 and the fluoropolymeric material. Effects of H2O on the activity and deactivation of these catalysts were also studied
Effect of acidic MCM-41 mesoporous silica functionalized with sulfonic acid groups catalyst in conversion of methanol to dimethyl ether
No full textThe global issue of contamination and power reserves has given dimethyl ether (DME) considerable attention. It is an encouraging and clean green material for the future resulting from its clean combustion properties. In this paper, a novel MCM-41-propyl-SO3H catalyst was successfully prepared with tethering of the active sulfonic acid groups onto the support via covalent bonds. This material was investigated as catalyst for DME synthesis via methanol dehydration in a fixed bed flow reactor at different experimental settings. TGA, NH3-TPD, SEM, XRD and BET techniques were utilized to characterize the synthesized material. MCM-41 sulfonated catalyst showed great thermal stability, high surface area and significant acid loading. The catalytic tests also demonstrated that the maximum methanol conversion was observed at 350 °C and catalyst contact time of 8 s. In addition, the catalyst showed a total selectivity to DME; light hydrocarbons and higher oxygenated compounds were not formed at temperatures above 300° C
Comparison of diamond-like carbon films having similar hardness deposited by glow discharge and sputtering
No full textHydrogenated amorphous carbon thin films have attracted great interest because of their mechanical, electrical and optical properties. Many techniques have been used to produce films with good properties. The present work reports on a comparison between films of high hardness deposited both by glow discharge and sputtering. All the films have been characterized by structural, optical and electrical measurements. Analogies and differences in the structure of the samples obtained by the two methods are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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