Acidic-Basic Properties of Catalysts for Conversion of Biomass Dusan Stosic
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
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. -
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. -
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. -
Proton Affinity Changes Driving Unidirectional Proton Transport In
doi:10.1016/S0022-2836(03)00903-3 J. Mol. Biol. (2003) 332, 1183–1193 Proton Affinity Changes Driving Unidirectional Proton Transport in the Bacteriorhodopsin Photocycle Alexey Onufriev1, Alexander Smondyrev2 and Donald Bashford1* 1Department of Molecular Bacteriorhodopsin is the smallest autonomous light-driven proton pump. Biology, The Scripps Research Proposals as to how it achieves the directionality of its trans-membrane Institute, 10550 North Torrey proton transport fall into two categories: accessibility-switch models in Pines Road, La Jolla, CA 92037 which proton transfer pathways in different parts of the molecule are USA opened and closed during the photocycle, and affinity-switch models, which focus on changes in proton affinity of groups along the transport 2Schro¨dinger Inc., 120 West chain during the photocycle. Using newly available structural data, and Forty-Fifth Street, 32nd Floor adapting current methods of protein protonation-state prediction to the Tower 45, New York, NY non-equilibrium case, we have calculated the relative free energies of pro- 10036-4041, USA tonation microstates of groups on the transport chain during key confor- mational states of the photocycle. Proton flow is modeled using accessibility limitations that do not change during the photocycle. The results show that changes in affinity (microstate energy) calculable from the structural models are sufficient to drive unidirectional proton trans- port without invoking an accessibility switch. Modeling studies for the N state relative to late M suggest that small structural re-arrangements in the cytoplasmic side may be enough to produce the crucial affinity change of Asp96 during N that allows it to participate in the reprotonation of the Schiff base from the cytoplasmic side. -
Proton Affinity of SO3
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Proton Affinity of SO3 Cynthia Ann Pommerening, Steven M. Bachrach, and Lee S. Sunderlin Department of Chemistry, Northern Illinois University, DeKalb, Illinois, USA ϩ Collision-induced dissociation (CID) of the radical cation H2SO4 gives the product pairs ϩ ϩ ϩ ϩ H2O SO3 and HO HSO3 with a 1:3 ratio that is essentially independent of collision energy. Statistical analysis of the two channels indicates that the proton affinity of HO is 3 Ϯ ϭ Ϯ 4 kJ/mol lower than that of SO3. This can be used to derive PA(SO3) 591 4 kJ/mol at 0 K and 596 Ϯ 4 kJ/mol at 298 K. Previously, Munson and Smith bracketed the proton affinity as PA(HBr) ϭ 584 kJ/mol Ͻ PA(SO ) Ͻ PA(CO) ϭ 594 kJ/mol. The threshold of 152 Ϯ 16 ϩ 3 kJ/mol for formation of H O ϩ SO indicates that the barrier to CID is small or nonexistent, 2 3 ϩ in contrast to the substantial barriers to decomposition for H3SO4 and H2SO4. (JAmSoc Mass Spectrom 1999, 10, 856–861) © 1999 American Society for Mass Spectrometry he development of extensive scales of proton this work provide an independent measurement of the ⌬ affinity (PA), gas basicity (GB), and acidity ( Ha) PA of SO3. values has provided a framework for the quanti- The gas-phase addition of H2OtoSO3 to form T ϭϪ⌬ tative understanding of ion properties. (PA H for sulfuric acid has a substantial barrier, as indicated by addition of a proton, GB ϭϪ⌬G for addition of a reaction rate measurements [4–6] and computational ⌬ ϭ⌬ proton, and Ha H for deprotonation.) The history results [7, 8]. -
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. -
Probing the Structure and Reactivity of Gaseous Ions a DISSERTATION
Probing the Structure and Reactivity of Gaseous Ions A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Matthew Michael Meyer IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Professor Steven R. Kass Febuary 2010 © Matthew Meyer 2010 Acknowledgements I want to express my gratitude to my advisor Dr. Steven Kass for the opportunity to work with him during my time at Minnesota. I am grateful for his willingness to share not only his vast knowledge of chemistry, but his approach to addressing problems. I also would like to acknowledge professors, John Anthony and Mark Meier for their mentorship while I was at the University of Kentucky that led me to a career in chemistry. Due to the broad nature of the research contained herein I am grateful for the contributions of the many collaborators I had the opportunity to work with while at Minnesota. In particular, I would like to thank Professors Richard O’Hair, Steven Blanksby, and Mark Johnson for their wiliness to allow me to spend time in their labs. During my course of studies I have also had the opportunities to interacts with a variety of other scientist that have contributed greatly to my development and completing this document, including Dr. Dana Reed, Dr. Mark Juhasz, Dr. Erin Speetzen, Dr. Nicole Eyet and Mr. Kris Murphy. I am also grateful for the support of my brother and sister through out this process. Lastly, I want to expresses gratitude to my parents for their support in all my pursuits and encouraging my incessant asking why probably since I could talk. -
Gas-Phase Hydrogen/Deuterium Exchange As a Molecular Probe for the Interaction of Methanol and Protonated Peptides
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Gas-Phase Hydrogen/Deuterium Exchange as a Molecular Probe for the Interaction of Methanol and Protonated Peptides Eric Gard, M. Kirk Green, Jennifer Bregar, and Carlito B. Lebrilla Departmentof Chemistry, University of California, Davis, California, USA The gas-phase hydrogen/deuterium (H/D) exchange kinetics of several protonated amino acids and dipeptides under a background pressure of CH,OD were determined in an external source Fourier transform mass spectrometer. H/D exchange reactions occur even when the gas-phase basicity of the compound is significantly larger (>20 kcal/mol) than methanol. In addition, greater deuterium incorporation is observed for compounds that have multiple sites of similar basicities. A mechanism is proposed that involves a structurally specific intermediate with extensive interaction between the protonated compound and methanol. (r Am Sot Mass Spectrom 1994,5, 623-631) he production of ionic gas-phase macro- [ 10, 11,18,19]. Investigations by Ausloos and L.ias [lOI molecules allows the possibility of studying these have shown that for protonated compounds H/D ex- T complex systems in the absence of solvent. Al- change reactions do not occur when the proton affinity though the gas and solvated phases are intrinsically of the neutral base is greater than the deuterated different, there is evidence to suggest that conforma- reagent by more than 20 kcal/mol. The correlation tion may be retained by the molecule even in the gas between basicity and reactivity has led many people to phase [l-5]. -
Gas-Phase Basicities of Polyfunctional Molecules. Part 2 : Saturated Basic Sites Guy Bouchoux, Jean-Yves Salpin
Gas-phase basicities of polyfunctional molecules. Part 2 : saturated basic sites Guy Bouchoux, Jean-Yves Salpin To cite this version: Guy Bouchoux, Jean-Yves Salpin. Gas-phase basicities of polyfunctional molecules. Part 2 : saturated basic sites. Mass Spectrometry Reviews, Wiley, 2012, 31 (3), pp.353-390. 10.1002/mas.20343. hal- 00760015 HAL Id: hal-00760015 https://hal.archives-ouvertes.fr/hal-00760015 Submitted on 5 Oct 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. BOUCHOUX AND SALPIN POLYFUNCTIONAL MOLECULES WITH SATURATED BASIC SITES Gas-phase basicities of polyfunctional molecules. Part 2: saturated basic sites Guy Bouchoux1,2* and Jean-Yves Salpin3,4 (1) Ecole Polytechnique - Laboratoire des Mécanismes Réactionnels (DCMR) - Département de Chimie - 91120 Palaiseau. France. (2) CNRS – UMR 7651 (3) Université d'Evry Val d'Essonne - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement (LAMBE) – Bâtiment Maupertuis – Bd F. Mitterrand - 91025 Evry. France (4) CNRS – UMR 8587 * Correspondence to: Guy Bouchoux. Laboratoire des Mécanismes Réactionnels. Département de Chimie. Ecole Polytechnique. 91120 Palaiseau. France. E-mail address: [email protected] Telephone: (33) 1 69 33 48 42 FAX: (33) 1 69 33 48 03 -1- BOUCHOUX AND SALPIN POLYFUNCTIONAL MOLECULES WITH SATURATED BASIC SITES Table of contents I.