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Industrial Chem (Week 9: Zeolites Also called molecular sieve …

- - - - Finding a catalyst to use
        
        Computational Modelling
        
        COMBINATORIAL CATALYSIS
        
        testing a whole heap of options to see if you get a hit
        
        higher throughput screening methods
        
        robots go through the best options to find the most efficient catalyst ratio
      - Catalysts & Manufacture
        
        Bulk Catalyst
        
        Raney Nickel used for hydrogenation
        
        __ catalyst for Ammonia oxidation
        
        CATALYST SUPORTS
        Purpose:
        
        EXPOSE MORE ACTIVE SITES
        
        need physical support to hold atom in place
        
        creates a highway for access meso, macro, micro
        
        endurances: must withstand temp and abuse (STRENGTH!!!!!)
        
        heat capacity, needs to remove the head
        
        Monolithic Structures
        
        Monoliths/ceramic foam (support structures)
        
        Catalyst active phase application???
        
        GENERAL CATALYST MANUFACTURE STEPS
        
        Dissolve components
        
        mix together (ensure homogenous mixing)
        
        precipitated and dried
        
        Calcinate (heat up in oven)
        
        need to teach customers how toReduce/Activate
      - Alumina/ Bayer process
        
        Digestion - dissolving bauxite's alumina content
        
        clarification settle how undissolved impurities
        
        Precipitation: forming alumina crystals
        
        calcination - high temp drying of alumina
      - Catalyst prep
        
        Impregnantion
        
        wetting with solution
        
        dried
        
        calcinated
        
        Co-precipitation
        
        mix materials but then raise pH to react out the insoluble catalyst material
        
        want to get the support and the actual catalyst to join together. The best way instead of just contacting the, together as solids, is to add them BOTH together inside solution to ensure the best homogeneity
        
        Drying
        
        Catalyst Shapes
        
        ring
        
        monolith
        
        wagonwheel
        
        Monolith:
        
        very strong
        
        low pressure and open structure
        
        like a meat minced (pushed extrusion)
        
        washcoat
    - - Biomass is heated in the presence of NO OXYGEN
        
        this heats the biomass into a vapour
        
        vapour is then condensed
        NOTE: Remove Oxygen = a less reactive bio-oil so that it stores longer
  - - - EXAM: know which industry is cleaner/ be able to work it out using Stoichiometric oxidation or catalyst oxidation
      - NOTE: you can't just use atom efficiency and E factors to determine the 'green-ness' of the process
  - - - sc- CO2
        EXTRACTION
        
        extraction of hops for brewing
        PROBLEMS
        
        moderate pressures req'd
        
        can be $$ for large scale work
        
        weak solvent
        
        energy considerations (compression of CO2 requires energy)
  - - - HOW TO MAKE ETHANOL FROM CORN
        
        mashed (corn meal + water + enzyme)
        
        cooked
        
        saccharification (convert the starch to sugar)
        
        fermented
        
        distilled
        
        separation
    - - Biomass harvested
        
        cut and pretreated to free up the cellulose so that enzymes can get them
        
        enzymes break down into sugar
        
        ferment
        
        purification through distillation
      - NOTE:
        Cellulose is super difficult to break down (lignin etc)
- - - - Acid/Base Catalysts
      - Transition Metal Compouns
  - - - Highly tailored
        
        Highly Specific
        highly efficient
        
        Catalyse very different reactions
    - - Catalysis through:
        
        shape selectivity
        
        acid/base
        
        incoroporation of metal particles
    - - High surface area supports Alumina, silica, AC, titania
      - Form: pellets or on monoliths
      - Cheap, high stability, catalyze many types of reaction
  - - - How fast the reaction takes in presence of catalyst
- - - - SCR
        
        from the economiser the flue gas passes through
        
        the NH3 is injected vapour that reduces the flue gas
        
        the flue gas then passses through the honeycomb catalyst
        
        NOx emisions REDUCE 80-90%
        
        (Too much NH3 = SO3 forming which damages eqmt)
        
        TYPES OF SCR CATALYSTS
        Low temp: Metal oxide spported platinum
        Medium Temp: Vanadia/tungsten
        High Temp Iron exchange zeolite
    - - Diesel engines
        
        diesel oxidation catalyst
        
        NOx traps
        
        Diesel particulate matter**
        
        mobile SCR
        
        MOBILE SCR
        
        the fluid goes through the catalytic converter
        
        combined with the flue gase
        
        the heat causes HYDROLYSIS (converts into ammonia)
        
        then goes int SCR where the ammonia creates water and N2
        
        DIESEL EXHAUST PURIFICATION
        
        Deisel fuel = high sulphur
        
        typical catalysts used in gas can't handle the sulphu
        
        Oxidation catalysts
        
        Huge amounts of air = easier to oxidis leftover CO (unburnt HC)
        
        Need to find a catalyst to fix all the emissions that come out during the 'cold start'
        
        Did alot of aging test (high temps long time)
        
        LEAN NOx TRAPS
        
        Absorber composition: Pt/Rh/Ba/Ce/Alumina
        
        Barium used to trap NOx surface, store NOx, inject extra fuel, run rich (so you can flood it with HC) and burn it off
        
        Not very fuel efficient tho
        AGING in NOx Traps
        
        Like a honeycomb structure
        -Catalyst gets coated inside the holes of honeycomb and gas goes through at a high velocity, this high velocity will allow turbulent flow and allows catalyst contact
      - Automotive vehicles
        
        three way catalyst
        
        Engine conditions
        
        want it to be as clost to stoichiometric 1 air:14.7 fuel
        
        THREE WAY CATALYSTIC CONVERTER
        
        ceramic honecomb
        
        put in a washcoat that contains the catalyst
        
        converts CO to CO2, NO to N2
        benefits
        
        withstands full acceleration
        
        good lifetime
        
        good temperature and vibration
        
        Catalyst composition
        1st stage = REDUCTION
        
        reduces all NO emissions
        
        NO ripped apart = freeing the O2
        2nd Stage = OXiDATOIN
        
        reduces unburned HC & CO by oxidising over platinum catalyst
        
        removes as much excess shit
- - - - POLYETHYLENE!!!
        Order of mechanical strength (Flexibility is the opposite)
        
        HDPE
        
        Short chained LLDPE (meaning less dense)???
        
        Long chained LDPE (more dense)?? is this meant to be the other way around???
      - POLYPROPYLENE (REFER TO PHOTO)
        
        atatic
        
        syndiotactic
        
        isotatic
    - - Titanium- based catalysts (ZIegler Natta)
      - Chromium - containing catalysts
      - Metallocene
- - - - BCC
        
        FCC
        
        HCP
    - - EXAM!!!!!!!
        
        On top sites (above a single metal atom)
        
        Bridging sites (between two atoms)
        
        Hollow sites (between four atoms)
    - - used to keep the surface atomically clean
        
        permit use od low energy electrons and ion based experiments without interference
      - i.e. 1 Torr = 133.3 Pa
        Rough (low) vacuum : 1 - 10-3 Torr
        Medium vacuum : 10-3 - 10-5 Torr
        High vacuum (HV) : 10-6 - 10-8 Torr
        Ultrahigh vacuum (UHV) : < 10-9 Torr
    - - expose the catalyst to some gas and does it *how much gas for how long) to see where it goes on the surface, and see what would would react
      - typically measured in Langmuir (exposure/L)
        (Exposure/L) = 10^6 x (Pressure/Torr) x (Time/s)
    - - Sticking Coefficient (S)
        likelihood of an incident moles to absorb onto the surface (from 0 not likely to 1 likely)
      - Surface Coverage
        
        If there's 100 sites, how many are actually covered? If 10 stick, therefor 0.1
        
        All sites are generally equal, however there are preferred seats (Langmuir)
    - - X-Ray Photoelectron Spectroscopy
        
        Shine X-rays on surface , electrons comes out. The energy of each electron coming off the atoms will be different energy (binding energy) levels
        
        Work function??
        
        Why the core electrons?
      - Auger effect
        
        when a core electron leaves a vacancy and electron with a higher energy will slip into the vacancy and the excess energy is released through photons or auger electrons
      - Temperature Program Desorption
        
        Gradually change the temperature and at different temperatures different shit will come off (this will tell you how strong it held)
      - Temperature Program Reduction
        
        a stream of hydrogen in a gas over the catalyst
        
        Follow amount of water produced as the surface OXIDES are REDUCED
      - Scanning Tunnelling Microscopy
      - Environmental Transmission Electron Microscopy
      - Fourier Transform Infared Spectroscopy