scholarly journals Shape-selective methylation of naphthalene with methanol over SAPO-11 molecular sieve modified with hydrochloric acid and citric acid

RSC Advances ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 243-250 ◽  
Author(s):  
Xiaoxiao Wang ◽  
Zhenmin Liu ◽  
Fang Guo ◽  
Yingchun Wang ◽  
Xianxian Wei ◽  
...  
Keyword(s):  
Citric Acid ◽  
Hydrochloric Acid ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Shape Selective

Herein, a series of SAPO-11 molecular sieves were modified by hydrochloric acid and citric acid.

scholarly journals An Efficient Synthesis of Ginsenoside Rg5 via Conversion of PPD Type Saponins: Unusual Application of 4A Molecular Sieves

2021 ◽  
Vol 16 (4) ◽  
pp. 1934578X2110076
Author(s):  
Cheng Le-qin ◽  
Ye An-qi ◽  
Zhang Hao-ran ◽  
Zhang Yue-wei ◽  
Li Ling
Keyword(s):  
Hydrochloric Acid ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Large Scale ◽  
High Yield ◽  
Experimental Conditions ◽  
Large Scale Preparation ◽  
Reaction Solution ◽  
Ginsenoside Rg5 ◽  
Scale Preparation

Ginsenoside Rg5 is a rare secondary ginsenoside with good pharmacological activity. However, preparation of Rg5 is time consuming, gives a low yield and has poor selectivity and efficiency. Therefore, the current study describes an efficient method of preparing ginsenoside Rg5 through conversion of Protopanaxadiol (PPD) type saponins in the presence of a molecular sieve and hydrochloric acid. The PPD type saponins were transformed on the surface of a molecular sieve to obtain ginsenoside Rg5 and most of the generated secondary ginsenoside was dissociates into the reaction solution, avoiding further decomposition. In addition, the optimal experimental conditions were identified to be as follows; 0.5 ml of absolute ethanol, 0.2 mol/L of hydrochloric acid, 12.5 mg of a 4A molecular sieve, a reaction time of 2.5 hours and a reaction temperature of 70 ℃. Under these experimental conditions, yields of upto 63.2% were obtained for ginsenoside Rg5. Moreover, the hydrochloric acid-catalyzed preparation of ginsenoside Rg5 effectively inhibited its decomposition in the presence of a molecular sieve. The method is therefore suitable for laboratory and industrial production with the advantages of large-scale preparation and high-yield.

Molecular Sieve Based Chemical Sensors

1994 ◽  
Vol 371 ◽  
Author(s):  
Kenneth J. Balkus ◽  
Laura J. Sottile ◽  
Hoan Nguyen ◽  
Scott J. Riley ◽  
Bruce E. Gnade
Keyword(s):  
Chemical Sensors ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Chemical Sensor ◽  
Selective Adsorption ◽  
Capacitance Measurements ◽  
Saw Devices ◽  
Signature Change ◽  
Shape Selective ◽  
Target Molecules

AbstractMolecular sieves, are attractive materials for discriminating chemical sensors. These microporous metal oxides offer shape selective adsorption as well as chemical and thermal stability. Molecular sieves have shown promise in SAW devices, however, these sensors rely only on a weight change upon adsorption of target molecules. We have developed a molecular sieve based capacitance type chemical sensor. Such a device should discriminate between molecules of similar size and shape because the signature change depends on the polarity of the adsorbate which in turn affects the dielectric properties of the molecular sieve. In this paper we describe the deposition of AIPO4 and MeAPO molecular sieve thin films on titanium nitride coated silicon wafers by laser ablation. A subsequent hydrothermal treatment followed by a Pd/Au coating and standard microlithography techniques generate the capacitors. The results for capacitance measurements in the presence of CO2, CO, NO, N2, O2, H2O and toluene indicate clear differences in selectivity between small, medium and large pore molecular sieves.

Preparation and Characterization of Ni-Containing Aluminophosphate Molecular Sieves

2011 ◽  
Vol 418-420 ◽  
pp. 617-620
Author(s):  
Ying Sun ◽  
Lan Ying Ge
Keyword(s):  
Oxidation State ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Crystalline Form ◽  
Spectroscopic Techniques ◽  
Tetrahedral Coordination ◽  
Tetrahedral Geometry ◽  
Nickel Ions ◽  
Aluminophosphate Molecular Sieves

Aluminophosphate molecular sieve and Ni(II)-containing APO-5 materials were synthesized hydrothermally and characterized by various analytical and spectroscopic techniques. It indicates that the nickel ions with a divalent oxidation state can incorporate into the tetrahedral coordination in mesoporous aluminophosphate very well. The better crystallizing temperature is explored. A stronger crystalline form is obtained with the addition of HF. Further, microporous aluminophosphate molecular sieves and Ni(II) ions remain in a tetrahedral geometry even after calcination at 550 °C.

Two-step demineralization of shrimp (Pandalus Borealis) shells using citric acid: An environmentally friendly, safe and cost-effective alternative to the traditional approach

2021 ◽  
Author(s):  
Julia Pohling ◽  
Deepika Dave ◽  
Yi Liu ◽  
Wade Murphy ◽  
Sheila Trenholm
Keyword(s):  
Citric Acid ◽  
Hydrochloric Acid ◽  
Environmental Health ◽  
Traditional Approach ◽  
Health And Safety ◽  
Cost Effective ◽  
Environmental Health And Safety ◽  
Pandalus Borealis ◽  
Chitin Extraction ◽  
Cost Effective Alternative

Removal of minerals from crustacean shells during chitin extraction is traditionally achieved using hydrochloric acid. However, the environmental, health and safety concerns of hydrochloric acid have led to investigation of...

Effect of pH, Acidulant, Time, and Temperature on the Growth and Survival of Listeria monocytogenes

1989 ◽  
Vol 52 (8) ◽  
pp. 571-573 ◽  
Author(s):  
KENT M. SORRELLS ◽  
DAVIN C. ENIGL ◽  
JOHN R. HATFIELD
Keyword(s):  
Antimicrobial Activity ◽  
Acetic Acid ◽  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Citric Acid ◽  
Hydrochloric Acid ◽  
Malic Acid ◽  
Incubation Temperature ◽  
Growth And Survival ◽  
Ph Values

The effect of different acids, pH, incubation time, and incubation temperature on the growth and survival of four strains of Listeria monocytogenes in tryptic soy broth was compared. Hydrochloric acid (HCl), acetic acid (AA), lactic acid (LA), malic acid (MA), and citric acid (CA) were used to acidify tryptic soy broth to pH values 4.4, 4.6, 4.8, 5.0, and 5.2 pH. Incubation times were 1, 3, 7, 14, and 28 d at 10, 25, and 35°C. The inhibition of L. monocytogenes in the presence of high acidity appears to be a function of acid and incubation temperature. Based on equal pH values, the antimicrobial activity is AA > LA > CA ≥ MA > HCl at all incubation times and temperatures. When based on equal molar concentration, the activity appeared to be CA ≥ MA > LA ≥ AA > HCl at 35 and 25°C, and MA > CA > AA ≥ LA > HCl at 10°C. Greatest antimicrobial activity occurred at 35°C. Greatest survival occurred at 10°C and greatest growth occurred at 25°C. Final pH of the medium was as low as 3.8 in HCl at 28 d. All strains grew well at pH values lower than the minimum previously reported (5.5–5.6).

Progress in Synthesis of Micro- and Mesoporous Composite Molecular Sieve

2011 ◽  
Vol 396-398 ◽  
pp. 1151-1156
Author(s):  
Wen Yuan Wu ◽  
Chun Wei Shi ◽  
Xue Bian
Keyword(s):  
Hydrothermal Synthesis ◽  
Microwave Radiation ◽  
Vapor Phase ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Vapor Phase Transport ◽  
Mesoporous Composite ◽  
Composite Molecular Sieve ◽  
Potential Applications ◽  
Phase Transport

Micro- and mesoporous composite molecular sieves enable to achieve grades distribution of pore sizes and appropriate collocation of acidity,which have potential applications in catalysis and adsorption of large molecules.This review focus on some of the most recent results during the last decades.The techniques applied to synthesize different micro-mesoporous composite molecular sieves includes single template, dual template, crystallization of mesoporous walls, alkaline desilication, vapor-phase transport synthesis,and microwave radiation hydrothermal synthesis.

Para-directed aromatic reactions over shape-selective molecular sieve zeolite catalysts

1979 ◽  
Vol 101 (22) ◽  
pp. 6783-6784 ◽  
Author(s):  
N. Y. Chen ◽  
W. W. Kaeding ◽  
F. G. Dwyer
Keyword(s):  
Molecular Sieve ◽  
Zeolite Catalysts ◽  
Shape Selective

scholarly journals Advances in the Radiocarbon Analysis of Carbon dioxide at the NERC Radiocarbon Facility (East Kilbride) using Molecular sieve Cartridges

Radiocarbon ◽  
2019 ◽  
Vol 61 (6) ◽  
pp. 1855-1865
Author(s):  
M H Garnett ◽  
Josephine-Anne Newton ◽  
P L Ascough
Keyword(s):  
Carbon Dioxide ◽  
Molecular Sieves ◽  
Molecular Sieve ◽  
Content Standards ◽  
Sieve Methods ◽  
Scientific Investigations ◽  
Consensus Values ◽  
Anthropogenic Processes ◽  
Automated Procedures ◽  
Quality Assurance Standards

ABSTRACTRadiocarbon (14C) analysis of carbon dioxide (CO2) provides unique information on the age, turnover and source of this important greenhouse gas, raising the prospect of novel scientific investigations into a range of natural and anthropogenic processes. To achieve these measurements, cartridges containing zeolite molecular sieves are a reliable and convenient method for collecting CO2 samples. At the NERC Radiocarbon Facility (East Kilbride) we have been refining our molecular sieve methods for over twenty years to achieve high-quality, reproducible and precise measurements. At the same time, we have been developing novel field sampling methods to expand the possibilities in collecting gas from the atmosphere, soil respiration and aquatic environments. Here, we present our latest improvements to cartridge design and procedures. We provide the results of tests used to verify the methods using known 14C content standards, demonstrating reliability for sample volumes of 3 mL CO2 (STP; 1.6 mg C) collected in cartridges that had been prepared at least three months earlier. We also report the results of quality assurance standards processed over the last two years, with results for 22 out of 23 international 14C standards being within measurement uncertainty of consensus values. We describe our latest automated procedures for the preparation of cartridges prior to use.

Development of taste responses in the rat parabrachial nucleus

1987 ◽  
Vol 57 (2) ◽  
pp. 481-495 ◽  
Author(s):  
D. L. Hill
Keyword(s):  
Citric Acid ◽  
Hydrochloric Acid ◽  
Age Groups ◽  
Developmental Differences ◽  
Average Response ◽  
Chorda Tympani Nerve ◽  
Ontogenetic Changes ◽  
Quinine Hydrochloride ◽  
Sodium Saccharin ◽  
Parabrachial Nuclei

Extracellular responses from neurons in the parabrachial nuclei (PBN) were studied in rats 4 days old to adulthood during chemical stimulation of the tongue with monochloride salts, citric and hydrochloric acids, sucrose, sodium saccharin, and quinine hydrochloride. Multiunit taste responses were recorded in rats at 4-7 days of age and single-unit responses were recorded from 121 neurons in four other age groups of 14-20 days, 25-35 days, 50-60 days, and adults. PBN neurons in rats 4-7 days old consistently responded to 0.1 M solutions of NH4Cl and NaCl, to 0.5 M solutions of NH4Cl, NaCl, and KCl, and to 1.0 M sucrose, 0.1 M sodium saccharin, 0.1 M citric acid, and 0.1 N HCl. They often did not respond, however, to 0.1 M KCl and 0.01 M quinine hydrochloride. Single PBN neurons in rats 14 days old and older characteristically responded to all stimuli, which consisted of 0.1 and 0.5 M salts, acids, sucrose, sodium saccharin, and quinine hydrochloride. Thus no developmental differences occurred in the number of stimuli to which neurons responded after rats were 14 days old. With the exception of responses to hydrochloric acid, there were significant increases in response frequencies to all stimuli after 14 days of age. Average response frequencies to NH4Cl and citric acid increased after 20 days of age and those to NaCl, LiCl, KCl, sucrose, sodium saccharin, and quinine hydrochloride increased after 35 days of age. Average response frequencies for hydrochloric acid did not alter after 14 days of age. The proportion of single PBN neurons that responded maximally to specific monochloride salts did not change during development. Most single neurons in all age groups responded equally well to NH4Cl, NaCl, and LiCl. No PBN neuron responded maximally to KCl. Developmental differences in response frequencies of third-order gustatory neurons in the PBN generally reflect developmental response changes in first-order neurons of the chorda tympani nerve and second-order neurons of the solitary nucleus. However, unique developmental changes are evident in the PBN. Thus the ontogenetic changes that occur in PBN responses likely relate to modifications of lower-order peripheral and central nervous system afferents and peripheral receptor sensitivities.

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