Catalysts in Aqueous Phase Reactions
45 Questions
2 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the typical temperature range for the reactor in the AIR PLANT?

  • 200-300 °C (correct)
  • 300-400 °C
  • 400-500 °C
  • 100-200 °C

    • The process stream exiting the reactor contains 10-15 mol% of EO.

    False

    What is the primary function of the purge reactor?

    To maintain a constant N2 concentration in the gas recycled to the reactor.

    The catalyst must be replaced when the __________ temperature is reached.

    <p>maximum</p> Signup and view all the answers

    Match the components of the process with their functions:

    <p>Reactor = Conducts the ethylene conversion Desorber = Removes EO from water Stripper = Removes lighter gases and impurities Purge Absorber = Recovers additional EO</p> Signup and view all the answers

    What is the per-pass ethylene conversion rate in the reactor?

    <p>20-30%</p> Signup and view all the answers

    The AIR PLANT uses a mixture of __________ and ethylene.

    <p>purified air</p> Signup and view all the answers

    The oxygen plant has a higher ethylene loss compared to the air plant.

    <p>False</p> Signup and view all the answers

    Why is it necessary to use a water-based absorber in the process?

    <p>To absorb EO from the gas mixture exiting the reactor.</p> Signup and view all the answers

    What is a significant difference between the air plant and the oxygen plant?

    <p>The need for a purge zone</p> Signup and view all the answers

    Which compound serves as the reaction catalyst in the aqueous phase?

    <p>Tungstate anions</p> Signup and view all the answers

    The absence of a solvent makes this chemical process highly viable on an industrial scale.

    <p>False</p> Signup and view all the answers

    What is the first compound produced when glucose is converted in the biotechnological process discussed?

    <p>Cis-cis-muconic acid</p> Signup and view all the answers

    The __________ is often a phase transfer catalyst in the described reaction.

    <p>Aliquat 336</p> Signup and view all the answers

    Match the following terms related to green chemistry with their descriptions:

    <p>Green Chemistry = A movement promoting reduced use of hazardous substances Adipic Acid = Product of oxidation of cis-cis-muconic acid H2O2 = Oxidant used in the aqueous phase Industrial Sustainability = Continuous improvement using cleaner technologies</p> Signup and view all the answers

    Why is the biotechnological method of producing adipic acid from glucose not competitive in terms of costs?

    <p>The fermentation batch and separation steps are costly.</p> Signup and view all the answers

    Green chemistry aims to eliminate the generation of hazardous substances in chemical processes.

    <p>True</p> Signup and view all the answers

    What reaction occurs after producing cis-cis-muconic acid to create adipic acid?

    <p>Hydrogenation</p> Signup and view all the answers

    A highly likely catalyst used in this reaction is __________ anions.

    <p>tungstate</p> Signup and view all the answers

    What is the primary function of the VaporSep unit?

    <p>To recover Ethylene vapors from Argon</p> Signup and view all the answers

    Ethylene glycol is primarily used for the production of antifreezing mixtures.

    <p>True</p> Signup and view all the answers

    What unit is necessary to remove CO2 to prevent its adverse influence on catalyst activity?

    <p>CO2 Absorber Unit with Basic Washing</p> Signup and view all the answers

    The product generated from the reaction with Ethylene glycol is a better __________ than water.

    <p>nucleophile</p> Signup and view all the answers

    At what temperatures can the reaction be performed without a catalyst?

    <p>140-230°C</p> Signup and view all the answers

    Match the chemical process with its purpose:

    <p>Ethylene Glycol = Production of PET Teraphthalic Acid = From petroleum refineries Vanillin = From biorenewable lignin CO2 Absorber = To remove CO2</p> Signup and view all the answers

    The VaporSep unit flares the Ethylene-enriched residue.

    <p>False</p> Signup and view all the answers

    What is the selectivity percentage for the ring opening reaction in the production of Ethylene Glycol?

    <p>90%</p> Signup and view all the answers

    The mixture of water and EO is sent to the __________ for the production of Ethylene Glycol.

    <p>EG Reactor</p> Signup and view all the answers

    What is the role of acid catalyst in the Ethylene Glycol reaction?

    <p>To prevent oligomer generation</p> Signup and view all the answers

    What does a high value of the selectivity constant KXYSel indicate?

    <p>High competition between anions for Q+</p> Signup and view all the answers

    Anions with higher electronegativity are more favorably partitioned into the organic phase.

    <p>False</p> Signup and view all the answers

    List one factor that affects the partitioning of anions between aqueous and organic phases.

    <p>Charge-to-Volume Ratio, Electronegativity, Hydration Energy, Structure</p> Signup and view all the answers

    Anions that are more __________, less electronegative, weakly hydrated, and with an organic structure are more favorably partitioned into the organic phase.

    <p>polarizable</p> Signup and view all the answers

    Match the factors affecting anion partitioning with their descriptions:

    <p>Charge-to-Volume Ratio = Influences the size and reactivity of ions Electronegativity = Tendency of an ion to attract electrons Hydration Energy = Energy released when an ion is surrounded by water molecules Structure = Influences the spatial arrangement of the molecule</p> Signup and view all the answers

    Which of the following anions would likely have the greatest affinity for association with Q+?

    <p>An ion with high polarizability and low electronegativity</p> Signup and view all the answers

    What is the primary effect of chlorine as a promoter in the reaction with silver catalyst?

    <p>Decreases the valence charge on oxygen</p> Signup and view all the answers

    C-H cleavage has a lower activation energy than O-insertion into the C=C bond.

    <p>False</p> Signup and view all the answers

    What intermediate can be produced from O-insertion into the C=C bond?

    <p>Ethene oxide</p> Signup and view all the answers

    The activation energy for the C-H cleavage reaction is _____ kJ/mol.

    <p>184</p> Signup and view all the answers

    Match the following reactions with their respective activation energies:

    <p>C-H cleavage = 184 kJ/mol O-insertion = 0 kJ/mol Direct combustion of propene = 67 kJ/mol Desorption of epoxide = 42 kJ/mol</p> Signup and view all the answers

    Which of the following conditions decreases epoxidation selectivity?

    <p>Higher temperatures</p> Signup and view all the answers

    The barrier for desorption of the epoxide is significantly high.

    <p>False</p> Signup and view all the answers

    What is the main product when ethene undergoes complete combustion?

    <p>Carbon dioxide and water</p> Signup and view all the answers

    An increase in propene's selectivity for combustion is related to the production of an _____ intermediate.

    <p>allylic</p> Signup and view all the answers

    What reaction proceeds without a significant activation energy in the context of ethene?

    <p>O-insertion</p> Signup and view all the answers

    Study Notes

    Aqueous Phase Reactions

    • Aqueous phase reactants include reaction catalyst (tungstate anions), phase transfer catalyst (Aliquat 336), and oxidant (H2O2).
    • Ionic form of catalyst interacts with H2O2 to create a coordination bond.
    • Aliquat 336 facilitates the transport of the complex to the organic phase for adipic acid production through four oxidation steps.
    • The absence of a solvent makes the process environmentally friendly, but industrial scalability is hindered by H2O2-related hazards and costs.

    Adipic Acid from Biomaterials

    • Adipic acid can be derived from biobased materials through fermentation pathways using specific enzymes.
    • Glucose is converted into cis, cis-muconic acid, which requires hydrogenation to yield adipic acid.
    • While this green technology is appealing, it is currently not cost-competitive with traditional production methods due to fermentation control and separation costs.

    Green Chemistry Principles

    • Green chemistry aims to innovate chemical technologies to minimize the generation of hazardous substances.
    • Focuses on sustainability with cleaner, safer technologies to reduce pollution and utilize resources efficiently.
    • Industrial sustainability has improved since the 1990s, driven by social pressure and legislation.

    Reactor and Process Conditions

    • In an air plant, purified air and ethylene are mixed, sent to the reactor at 200-300 °C and 10-30 atm.
    • Per-pass ethylene conversion ranges from 20-30%, yielding high selectivity (70-80%).
    • The process produces a mixture containing 1-3 mol% of ethylene oxide (EO), which is absorbed in water for purification.
    • The exit gas contains ethylene, split into two streams for recycling and to maintain nitrogen concentration in the reactor.

    Ethylene and Oxygen Plants

    • Oxygen plants require similar reactor conditions and recovery systems but avoid purge zones, reducing ethylene loss.
    • VaporSep technology removes impurities, allowing a higher ethylene concentration, thus increasing catalyst selectivity.
    • CO2 adversely affects catalyst activity; a CO2 absorber unit with basic washing is necessary to mitigate this issue.

    Ethylene Oxide Applications

    • Ethylene oxide is flammable and typically processed further through ring-opening reactions to create various chemicals, notably ethylene glycol.
    • Ethylene glycol is a key monomer for producing PET, used for plastics with excellent thermal properties.
    • Synthetic methods include reactions with terephthalic acid or vanillin derived from renewable lignin.

    Ethylene Glycol Production

    • Ethylene glycol synthesis involves ring-opening reactions with a water excess at 60 °C and in the presence of 1% H2SO4 to prevent oligomer formation.
    • Alternative synthesis occurs at 140-230 °C and 20-40 atm without a catalyst, carefully controlling pressure and residence time.

    Epoxidation Process Mechanisms

    • Ethene reacts with oxygen via two pathways: C-H cleavage (high activation energy) or O-insertion into the C=C bond (low activation energy).
    • The presence of chlorine as a promoter decreases valence charge on oxygen, favoring ethylene epoxidation.
    • Propene's reactions follow a similar pattern, with direct H abstraction yielding lower epoxidation selectivity.

    Aliphatic Nucleophilic Substitution

    • In aqueous-organic phasing systems, quaternary salt and excess metal salt facilitate the transfer of anions into the organic phase.
    • The extraction equilibria determine the capability of anions to partition between aqueous and organic phases.
    • High selectivity constant (KX→Y sel) indicates favorable reactant competition and anion association.

    Partitioning Factors

    • Anion partitioning between phases is influenced by charge-to-volume ratio, electronegativity, hydration energy, and structure.
    • More polarizable, less electronegative, weakly hydrated anions with organic structures are preferentially partitioned into the organic phase.
    • Anions with greater affinity for association with quaternary cation Q+ demonstrate higher potential for substitution in reactions.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Adipic Acid Production - Simplified Overview PDF

    Description

    Explore the role of various reactants in aqueous phase reactions, focusing on tungstenate anions, Aliquat 336, and H2O2. Learn about the ionic/non-ionic equilibrium and the mechanism that facilitates the transfer of complexes to the organic phase with oxidation steps. This quiz will enhance your understanding of complex chemical interactions and catalysts.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser