A Porous Brønsted Superacid As an Efficient and Durable Solid Catalyst
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Topic 5: Acids and Bases
Topic 5: Acids And BAses Topic 5: Acids and Bases C12-5-01 Outline the historical development of acid-base theories. Include: the Arrhenius, Brønsted-Lowry, and Lewis theories C12-5-02 Write balanced acid-base chemical equations. Include: conjugate acid-base pairs and amphoteric behaviour C12-5-03 Describe the relationship between the hydronium and hydroxide ion concentrations in water. Include: the ion product of water, Kw C12-5-04 Perform a laboratory activity to formulate an operational definition of pH . C12-5-05 Describe how an acid-base indicator works in terms of colour shifts and Le Ch âtelier’s principle. C12-5-06 Solve problems involving pH. C12-5-07 Distinguish between strong and weak acids and bases. Include: electrolytes and non-electrolytes C12-5-08 Write the equilibrium expression ( Ka or Kb) from a balanced chemical equation. C12-5-09 Use Ka or Kb to solve problems for pH, percent dissociation, and concentration. C12-5-10 Perform a laboratory activity to determine the concentration of an unknown acid or base, using a standardized acid or base. C12-5-11 Predict whether an aqueous solution of a given ionic compound will be acidic, basic, or neutral, given the formula. suggested Time: 14 hours Grade 12 C hemistry • Topic 5: Acids and Bases SpeCifiC Learning OutCOmeS Topic 5: C12-5-01: Outline the historical development of acid-base theories. Acids and include: the arrhenius, Br ønsted-Lowry, and Lewis theories Bases C12-5-02: Write balanced acid-base chemical equations. include: conjugate acid-base pairs and amphoteric behaviour (2 hours) 1 2 uggesTions for nsTrucTion 0 0 s i - - 5 5 - - Entry-Level Knowledge 2 2 1 1 In Grade 10 Science (S2-2-08), students experimented to classify acids and bases C C : : according to their characteristics. -
The Strongest Acid Christopher A
Chemistry in New Zealand October 2011 The Strongest Acid Christopher A. Reed Department of Chemistry, University of California, Riverside, California 92521, USA Article (e-mail: [email protected]) About the Author Chris Reed was born a kiwi to English parents in Auckland in 1947. He attended Dilworth School from 1956 to 1964 where his interest in chemistry was un- doubtedly stimulated by being entrusted with a key to the high school chemical stockroom. Nighttime experiments with white phosphorus led to the Headmaster administering six of the best. He obtained his BSc (1967), MSc (1st Class Hons., 1968) and PhD (1971) from The University of Auckland, doing thesis research on iridium organotransition metal chemistry with Professor Warren R. Roper FRS. This was followed by two years of postdoctoral study at Stanford Univer- sity with Professor James P. Collman working on picket fence porphyrin models for haemoglobin. In 1973 he joined the faculty of the University of Southern California, becoming Professor in 1979. After 25 years at USC, he moved to his present position of Distinguished Professor of Chemistry at UC-Riverside to build the Centre for s and p Block Chemistry. His present research interests focus on weakly coordinating anions, weakly coordinated ligands, acids, si- lylium ion chemistry, cationic catalysis and reactive cations across the periodic table. His earlier work included extensive studies in metalloporphyrin chemistry, models for dioxygen-binding copper proteins, spin-spin coupling phenomena including paramagnetic metal to ligand radical coupling, a Magnetochemi- cal alternative to the Spectrochemical Series, fullerene redox chemistry, fullerene-porphyrin supramolecular chemistry and metal-organic framework solids (MOFs). -
Tailoring the Surface Area and the Acid–Base Properties of Zro2 for Biodiesel Production from Nannochloropsis Sp
www.nature.com/scientificreports OPEN Tailoring the surface area and the acid–base properties of ZrO2 for biodiesel production from Nannochloropsis sp. Nurul Jannah Abd Rahman1, Anita Ramli1*, Khairulazhar Jumbri1,3 & Yoshimitsu Uemura2,3 Bifunctional heterogeneous catalysts have a great potential to overcome the shortcomings of homogeneous and enzymatic catalysts and simplify the biodiesel production processes using low-grade, high-free-fatty-acid feedstock. In this study, we developed ZrO2-based bifunctional heterogeneous catalysts for simultaneous esterifcation and transesterifcation of microalgae to biodiesel. To avoid the disadvantage of the low surface area of ZrO2, the catalysts were prepared via a surfactant-assisted sol-gel method, followed by hydrothermal treatments. The response surface methodology central composite design was employed to investigate various factors, like the surfactant/ Zr molar ratio, pH, aging time, and temperature on the ZrO2 surface area. The data were statistically analyzed to predict the optimal combination of factors, and further experiments were conducted for verifcation. Bi2O3 was supported on ZrO2 via the incipient wetness impregnation method. The catalysts were characterized by a variety of techniques, which disclosed that the surfactant-assisted ZrO2 nanoparticles possess higher surface area, better acid–base properties, and well-formed pore structures than bare ZrO2. The highest yield of fatty acid methyl esters (73.21%) was achieved using Bi2O3/ ZrO2(CTAB), and the catalytic activity of the developed catalysts was linearly correlated with the total densities of the acidic and basic sites. The mechanism of the simultaneous reactions was also discussed. Biodiesel is an attractive alternative source of energy owing to its renewability, biodegradability, sustainability, and non-toxicity1. -
140. Sulphuric, Hydrochloric, Nitric and Phosphoric Acids
nr 2009;43(7) The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals 140. Sulphuric, hydrochloric, nitric and phosphoric acids Marianne van der Hagen Jill Järnberg arbete och hälsa | vetenskaplig skriftserie isbn 978-91-85971-14-5 issn 0346-7821 Arbete och Hälsa Arbete och Hälsa (Work and Health) is a scientific report series published by Occupational and Enviromental Medicine at Sahlgrenska Academy, University of Gothenburg. The series publishes scientific original work, review articles, criteria documents and dissertations. All articles are peer-reviewed. Arbete och Hälsa has a broad target group and welcomes articles in different areas. Instructions and templates for manuscript editing are available at http://www.amm.se/aoh Summaries in Swedish and English as well as the complete original texts from 1997 are also available online. Arbete och Hälsa Editorial Board: Editor-in-chief: Kjell Torén Tor Aasen, Bergen Kristina Alexanderson, Stockholm Co-editors: Maria Albin, Ewa Wigaeus Berit Bakke, Oslo Tornqvist, Marianne Törner, Wijnand Lars Barregård, Göteborg Eduard, Lotta Dellve och Roger Persson Jens Peter Bonde, Köpenhamn Managing editor: Cina Holmer Jörgen Eklund, Linköping Mats Eklöf, Göteborg © University of Gothenburg & authors 2009 Mats Hagberg, Göteborg Kari Heldal, Oslo Arbete och Hälsa, University of Gothenburg Kristina Jakobsson, Lund SE 405 30 Gothenburg, Sweden Malin Josephson, Uppsala Bengt Järvholm, Umeå ISBN 978-91-85971-14-5 Anette Kærgaard, Herning ISSN 0346–7821 Ann Kryger, Köpenhamn http://www.amm.se/aoh -
Isomerization of Alpha-Pinene Oxide Over Solid Acid
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by ScholarBank@NUS ISOMERIZATION OF ALPHA-PINENE OXIDE OVER SOLID ACID CATALYSTS D. B. R. A. DE SILVA (B.Sc. (Hons.), UNIVERSITY OF PERADENIYA, SRI LANKA) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE 2003 Acknowledgements First and foremost, I would like to thank my supervisor A/P G.K. Chuah, for her constant encouragement, invaluable guidance, patience and understanding throughout the length of my candidature in NUS. I am also grateful to A/P Stephan Jaenicke, for his invaluable guidance. I would also like to thank all the other members of our research group for their kind help and encouragement during my candidature. Thanks are due to my parents and wife for their understanding, encouragement and support. Finally, I wish to express my gratitude to the National University of Singapore for awarding me a valuable research scholarship. i TABLE OF CONTENTS PAGE Acknowledgement i Table of Contents ii Summary v List of Tables vii List of Figures ix Chapter I Introduction 1.1 Mesoporous Molecular Sieves 1 1.1.1 Catalytic Application of Mesoporous Materials 2 1.1.2 Modification of Mesoporous Materials 2 1.1.3 Micro- and Mesoporous Materials 4 1.2 Environment Impact of Solid Catalysts 6 1.3 Solid Acid and Catalysts 8 1.4 Supported Oxide Catalysts 9 1.4.1 Metal Oxide Supported Boron Oxide 13 1.4.2 SiO2-Supported ZrO2 Catalysts 15 1.4.3 InCl3-Supported Solid Acid Catalysts 16 1.5 Methodology -
Notes Acids and Bases
Notes Acids and Bases Arrhenius Acid Base Theory: In 1884 Svante Arrhenius proposed the first theoretical model for acids and bases. Prior to that time, these chemically opposite substances were described in properties such as their taste; their effects on metals, carbonates, and dyes (called indicators); their feel to the touch, and their ability to react with each other. According to the Arrhenius theory , pure water dissociates to some extent to produce hydrogen ions, H + and hydroxide ions, OH -. When this occurs, equal amounts of H + and OH - ions are produced: + - H2O(l) H (aq) + OH (aq) An acid, according to Arrhenius, is any substance that liberates H + ions when placed in water. When the H + concentration is elevated the OH - concentration decreases, this solution is said to be acidic. Similarly, a base is defined as any substance that liberates OH - ions when placed in water. The resulting solution has a higher concentration of OH - ions than H + ions and is said to be basic, or alkaline. + - ACID: HCl (aq) H (aq) + Cl (aq) + - BASE: NaOH (aq) Na (aq) + OH (aq) Brønsted - Lowry Acid Base Theory: A more general and realistic theory was proposed by two chemists working independent of the other, Johannes Nicolaus Brønsted of Denmark and Thomas Martin Lowry of England. Both chemists are given credit; the theory is named the Brønsted-Lowry theory . Acids are defined as substances that donate H + ions, protons and therefore are called proton donators, while bases are substances that accept protons and are defined as proton acceptors. On this basis, the autoionization of water is given as follows: + - H2O(l) + H 2O(l) H3O (aq) + OH (aq) In this reaction, one water molecule donates a proton, H +, and behaves as an acid, while the other water molecule accepts the proton and behaves as a base. -
Rational Design of Metal Oxide Solid Acids for Sugar Conversion
catalysts Review Rational Design of Metal Oxide Solid Acids for Sugar Conversion Atsushi Takagaki Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan; [email protected]; Tel.: +81-92-802-6711 Received: 15 October 2019; Accepted: 24 October 2019; Published: 29 October 2019 Abstract: Aqueous-phase acid-catalyzed reactions are essential for the conversion of cellulose-based biomass into chemicals. Brønsted acid and Lewis acid play important roles for these reactions, including hydrolysis of saccharides, isomerization and epimerization of aldoses, conversion of d-glucose into 5-hydroxymethylfurfural, cyclodehydration of sugar alcohols and conversion of trioses into lactic acid. A variety of metal oxide solid acids has been developed and applied for the conversion of sugars so far. The catalytic activity is mainly dependent on the structures and types of solid acids. Amorphous metal oxides possess coordinatively unsaturated metal sites that function as Lewis acid sites while some crystal metal oxides have strong Brønsted acid sites. This review introduces several types of metal oxide solid acids, such as layered metal oxides, metal oxide nanosheet aggregates, mesoporous metal oxides, amorphous metal oxides and supported metal oxides for sugar conversions. Keywords: Sugars; cellulose; glucose; 5-hydroxymethylfurfural; lactic acid; solid acid; Brønsted acid; Lewis acid; metal oxide; water-tolerant catalyst 1. Introduction The fundamental features of solid acid catalysts are the reusability of the catalysts, their easy separation from the products and solvents and unnecessary neutralization, which are beneficial to saving energy and cost. Besides these, special requirements of the catalysts for sugar conversion are high recognition ability of sugar molecules and high tolerance against water. -
Acid-Base Catalysis Application of Solid Acid-Base Catalysts
Modern Methods in Heterogeneous Catalysis Research Acid-Base Catalysis Application of Solid Acid-Base Catalysts Annette Trunschke 18 February 2005 Outline 1. Introduction - basic principles 2. Substrates and products 3. Kinds of acid / base catalysts - examples 4. Characterization of surface acidity / basicity - examples 5. Acid catalyzed reactions 6. Base catalyzed reactions 7. Acid-base bifunctional catalysis 8. Summary and outlook Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 2 1. Introduction - Basic definitions concept acid base - + Brønsted H2O OH + H - - Lewis FeCl3 + Cl [FeCl4] Hydrogen transfer reactions intermediates acid-catalyzed + H+ carbenium ions base-catalyzed + H+ carbanions Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 3 1. Introduction - Basic definitions specific acid / base general acid / base catalysis catalysis + - active H3O or OH undissociated acid or base species groups; a variety of species may be simultaneously active reaction •in solution •gas phase reactions medium / •on the surface of •high reaction temperatures conditions a hydrated solid Advantages of solid acid-base catalysts: • Easier separation from the product • Possible reuse and regeneration • Fewer disposal problems • Non-corrosive and environmentally friendly (but not always!) Modern Methods in Heterogeneous Catalysis Research : 18/02/2005 4 2. Substrates and products solid acid catalysis solid base catalysis substrates •Alkanes, aromatics •Alkenes (components of crude •Alkynes petrolium) •Alkyl aromatics •Alkenes (products of •Carbonyl compounds petrolium cracking (FCC, steam cracking)) products •Gasoline components •Chemical intermediates •Chemical intermediates •Fine chemicals •Fine chemicals Industrial processes in 1999: 103 solid acids worldwide production by catalytic cracking: 500x106 tonnes/y 10 solid bases 14 solid acid-base bifunctional catalysts K.Tanabe, W.F.Hölderich, Applied Catalysis A 181 (1999) 399. -
Acid Dissociation Constant - Wikipedia, the Free Encyclopedia Page 1
Acid dissociation constant - Wikipedia, the free encyclopedia Page 1 Help us provide free content to the world by donating today ! Acid dissociation constant From Wikipedia, the free encyclopedia An acid dissociation constant (aka acidity constant, acid-ionization constant) is an equilibrium constant for the dissociation of an acid. It is denoted by Ka. For an equilibrium between a generic acid, HA, and − its conjugate base, A , The weak acid acetic acid donates a proton to water in an equilibrium reaction to give the acetate ion and − + HA A + H the hydronium ion. Key: Hydrogen is white, oxygen is red, carbon is gray. Lines are chemical bonds. K is defined, subject to certain conditions, as a where [HA], [A−] and [H+] are equilibrium concentrations of the reactants. The term acid dissociation constant is also used for pKa, which is equal to −log 10 Ka. The term pKb is used in relation to bases, though pKb has faded from modern use due to the easy relationship available between the strength of an acid and the strength of its conjugate base. Though discussions of this topic typically assume water as the solvent, particularly at introductory levels, the Brønsted–Lowry acid-base theory is versatile enough that acidic behavior can now be characterized even in non-aqueous solutions. The value of pK indicates the strength of an acid: the larger the value the weaker the acid. In aqueous a solution, simple acids are partially dissociated to an appreciable extent in in the pH range pK ± 2. The a actual extent of the dissociation can be calculated if the acid concentration and pH are known. -
57(2)-08(Priyanka Singh 069).Fm
Korean Chem. Eng. Res., 57(2), 164-171 (2019) https://doi.org/10.9713/kcer.2019.57.2.164 PISSN 0304-128X, EISSN 2233-9558 Study of Protonation Behaviour and Distribution Ratios of Hydroxamic Acids in Hydrochloric and Perchloric Acid Solutions Through Hammett Acidity Function, Bunnett-Olsen and Excess Acidity Method Manisha Agarwal*, Priyanka Singh** and Rama Pande***,† *School of Studies in Chemistry, Pt. Ravishankar Shukla University, Raipur-492010, Chhattisgarh, India **Rungta College of Engineering & Technology, Bhilai-490024, Chhattisgarh, India ***Department of Chemistry, Govt. Digvijay PG Autonomous College,Rajnandgaon-491441 Chhattisgarh, India (Received 4 July 2018; Received in revised form 20 December 2018; accepted 21 December 2018) Abstract − The protonation parameters, dissociation constants (pKBH+) of conjugate acid, slope values (m, ϕ and m*) and correlation coefficients (r) of hydroxamic acids were determined by Hammett acidity function method, Bunnett- Olsen method and excess acidity method in hydrochloric and perchloric acid solutions. Effect of acid concentration on partition and percentage protonation was also studied. pKBH+ values show that hydroxamic acids do not behave as Ham- mett bases, but hydroxamic acids behave as weak bases in strong acidic solutions. The values of pKBH+ obtained through Bunnett-Olsen method and excess acidity method were compared with the Hammett acidity function. ChemAxon’s Mar- vinSketch 6.1.5 software was also used for determining pKa, pI and microspecies distribution (%) of hydroxamic acids with pH. Hydrogen donor and acceptor values and logD were also obtained. The results show that N-p-chlorophenyl-4- bromobenzohydroxamic acid has the highest pKa and lowest logD values. On the contrary, N-phenyl-3,5-dinitrobenzo- hydroxamic acid has lowest the pKa and highest logD values. -
Efficient Biodiesel Production Via Solid Superacid Catalysis
RSC Advances REVIEW Efficient biodiesel production via solid superacid catalysis: a critical review on recent breakthrough Cite this: RSC Adv.,2016,6,78351 Peter Adeniyi Alaba,*a Yahaya Muhammad Sanib and Wan Mohd Ashri Wan Daud*a Biodiesel produced from triglycerides and/or free fatty acids (FFAs) by transesterification and esterification has attracted immense attention during the past decades as a biodegradable, renewable and sustainable fuel. Currently, the use of solid superacid catalysts has proved a more efficient and “green” approach due to avoidance of environmental and corrosion problems and reduced product purification procedures. However, it is less viable economically because the reusability is low due to the lack of a hydrophilic/ hydrophobic balance in the reactions that involve the use of inedible feedstock with a high water content. Therefore, this study gives a critical review on recent strategies towards efficient and “green” production of biodiesel via solid superacid catalysis. The strategies discussed include alkyl-bridged Received 1st April 2016 organosilica moieties functionalized hybrid catalysis to improve the hydrothermal stability of superacid Accepted 2nd August 2016 catalysts, pre- and in situ water removal, and process intensification via temperature profile reduction. DOI: 10.1039/c6ra08399d The strategies enabled well-defined porosity and an excellent hydrophobicity/hydrophilicity balance, www.rsc.org/advances which suppressed deactivation by water and glycerol. 1. Introduction posed by fossil diesel. Some studies have revealed that biodiesel has become the most interesting alternative.1–3 The two major There is urgent need for alternative sources of energy due to the precursors of biodiesel are triglycerides and free fatty acids unrenewability, unsustainability and environmental threat (FFAs), which are obtained from edible oil, nonedible oil,4,5 animal fats and used vegetable oils.6 Previously, the most popular biodiesel produced was from edible oil. -
Acid Strength Measurements of Amberlyst 15 Resin, P-Xylene-2
Reaction Kinetics, Mechanisms and Catalysis https://doi.org/10.1007/s11144-019-01551-7 Acid strength measurements of Amberlyst 15 resin, p‑xylene‑2‑sulfonic acid and chlorosulfonic and sulfuric acid treated SiO2, Al2O3, TiO2 and MgO Marek Marczewski1 · Monika Aleksandrowicz1 · Ewelina Brzezińska1 · Maja Podlewska1 · Mateusz Rychlik1 · Sandra Żmuda1 · Urszula Ulkowska1 · Marek Gliński1 · Osazuwa Osawaru2 Received: 22 November 2018 / Accepted: 11 February 2019 © The Author(s) 2019 Abstract The measurements of the minimum acid strength (H Omin) required for the ini- tiation of cis-stilbene at 303 K and tert-butylbenzene at 313 K, 323 K and 333 K have enabled the establishment of a much more precise acid strength scale based on test reactions. HOmin values obtained were: − 9.0 (cis-stilbene, 303 K), − 9.3, − 9.5 and − 9.9 (tert-butylbenzene, 313 K, 323 K, 333 K). The updated method was used for the determination of the acid strength of diferent catalysts obtained in the reaction of chlorosulfonic and sulfuric acid on diferent oxide carriers. It was found that the acid strength values depended on the basicity of the studied supports. For the supports treated with chlorosulfonic acid the values of acid strength were: − 11.5 < HO ≤ − 10.8 in the case of the less basic SiO 2 and − 9.3 < HO ≤ − 9.0 for the more basic TiO2, Al2O3 and MgO. For the supports treated with sulfuric acid the acid strength was: -9.3 < HO ≤ -9.0 for the less basic SiO2 and TiO2, − 9.0 < HO ≤ − 7.9 for the more basic Al 2O3 and − 7.9 < HO ≤ − 6.9 for the most basic MgO.