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by: Malcolm Glover


Malcolm Glover
GPA 3.85


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Class Notes
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This 14 page Class Notes was uploaded by Malcolm Glover on Tuesday October 13, 2015. The Class Notes belongs to CHEM 2001 at Louisiana State University taught by Staff in Fall. Since its upload, it has received 13 views. For similar materials see /class/223112/chem-2001-louisiana-state-university in Chemistry at Louisiana State University.




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Date Created: 10/13/15
Catalysis Intro 1 Summary of Industrial Catalytic Processes Process Typical Catalysts l l i gjl 17H Cracking PtRe on alumina Zeolites Reforming PtReGeSn on alumina dehydrogenation Hydrocracking alumina zeolites Pt Alkylation H2SO4 HF Hydrodesulfurization MoCo oxides MoNi oxides Hydrodenitrogenation W N i oxides u39w l Natural Gas desulfurization ZnO Cu Fe on activated C Hydrogenations Raney Ni Raney Co Pt Rh Ammonia synthesis promoted Fe Methanol synthesis CuZnO Dehydrogenation Butadiene Fe203 PtRe on alumina styrene Zn Cr Fe or Mn oxides Oxidations ethylene oxide Ag nitric acid PtRh meshgauze sulfuric acid V205 maleic phthalic anhydrides V205 formaldehyde Ag or Cu Mo Fe V oxides Polymerizations ZieglerNatta polypropylene Al alkyls TiCl3 Dow single site polypropylene Ti metallocene Phillips Cr oxide on silica Polyethylene low density peroxides peresters Polystyrene benzoyl peroxide Urethanes amines organotin phosphine oxides Hydroformylation Union CarbideHoechstBASF RhPPh3 ExxonBASF HCoCO4 Shell HCoCO4PR3 R bulky alkyl Catalysis Intro 2 Catalytic Production of the Top mm Industrial Chemicals Ranking Chemical Production 4 Etherne Steam Cracking of Hydrocarbons larger hydrocarbon gt smaller hydrocarbon H2 CzH6g gt CzH4g H2g 33 b11110 le Catalyst Zeolites PtRe on A1203 support Conditions 850 C 20 50 atm 10 Properne Steam Cracking of Hydrocarbons C3Hsg gt C3H6g C2H4g CH4g H2g 18 Km lb Catalyst Zeolites PtRe on A1203 support 1 0 5 Conditions 850 C 20 50 atm 12 Dichloroethane Direct Chlorination C2H4g C12g gt ClCHzCH2C1g Catalyst FeCl3 or AlCl3 15 billion lbs Oxychlorination 2C2H4g 4HClg 02 gt 2ClCH2CH2Clg 2H20 Catalyst Cu salts on Si02 or A1203 supports 16 Benzene Hydrocarbon Reforming dehydrogenation C6H14g gt C6H12g H2g Endothermicl C6H12g gt C6H6g 3H2g Endothermicl 10 blulon lbs toluene gt benzene methane Catalyst PtReGeSn on A1203 support 17 Ethyl Benzene C6H6g C2H4g gt C6H5C2H5 1 Catalyst Liquid phase system with AlCl3 9 billion lbs 2 Catalyst Zelolite Lewis Acid based gas phase process Classic Friedel Crafts rxn 19 VinyI Choride ClCHzCH2C1g gt H2CCHClg HClg This reaction is often coupled with the oxychlorination reaction to produce dichloroethane this allows recycling of the HCl 8 billion lbs 20 Styrene Dehydrogenation of ethyl benzene Catalyst Fe oxides on A1203 support 8 billion lbs Conditions 550 600 C 21 Terephthalic Acid Amoco Process 8 billion lbs p CH3 C6H4 CH3 302 gt p HOOC C6H4 COOH H20 Catalyst CoMn salts with some heavy metal bromides Conditions liquid acetic acid solution 200 C 20 atm Ti or Hastelloy C lined reactor very corrosive Catalysis Intro 3 22 Methanol C0 H2 gt CH3OH Catalyst ZnOCu salt 7 billion lbs Conditions gt 100 atm 200 300 C 24 Ethylene Oxide C2H4g 1202 gt ethylene oxide Catalyst Ag 6 billion lbs Conditions 300 C 26 Toluene Catalytic Reforming of methyl cyclohexane and derivatives Catalyst PtRe on A1203 support 6 billion lbs Conditions 500 C and 25 atm 27 Xylenes Catalytic Reforming of 14 dimethylcyclohexane Catalyst PtRe on A1203 support 55 billion lbs Conditions 500 C and 25 atm 28 Ethylene Glycol ethylene oxide HZO gt HOCHZCHZOH Catalyst H2S04 05 1 50 70 C 5 billion lbs Conditions Thermal 195 C and 15 atm 29 Butylaldehyde Hydroformylation Union CarbideCelaneseBASF propylene H2 CO gt CH3CH2CH2CHO 5 billion lbs Catalyst homogeneous RhPPh3 catalyst Conditions 100 125 C 8 25 atm 31 Cummene benzene propene gt C6H5CHCH32 1 Liquid phase catalysts H2S04 AlCl3 HF 3397 billion lbs 2 Gas phase catalyst H3PO4 on SiOz Friedel Crafts reaction Conditions 35 40 C 7 bar liquid 200 300 C 20 40 bar gas Cumene is mainly used to produce phenol and acetone 32 Acetic Acid CH3OH CO gt CH3COOH 35 billion lbs Catalyst homogeneous Rh12CO2 Monsanto Acetic Acid process Conditions 150 C 35 atm Catalysis Intro 4 Homogeneous Catalysis catalyst A B gt C Remember that thermodynamics and equilibrium still rule A catalyst only speeds up the rate at which a chemical reaction reaches equilibrium The actual equilibrium constant thermodynamics is NOT affected by the catalyst Therefore nonspontaneous reactions are usually NOT suitable for catalytic applications AdvantagesDisadvantages of Homogeneous Catalysts Relative to Heterogeneous Catalysts Good homogeneous catalysts are good generally far more selective for a single product far more active far more easily studied from chemical amp mechanistic aspects far more easily modi ed for optimizing selectivity bad far more sensitive to permanent deactivation far more dif cult for acheiving productcatalyst separations Heterogeneous catalysts dominate chemical and petro chemical industry 95 of all chemical processes use heterogenous catalysts Homogenous catalysts are used when selectivity is critical and productcatalyst separation problems can be solved Catalysis Intro 5 Homogeneous or Heterogeneous Because many homogeneous catalysts decompose to form heterogeneous catalysts and some heterogeneous catalysts can dissolve to form homogeneous catalysts one should always be careful about making assumptions on what type of catalyst one is using in any new catalytic experiment There are several general ways to test whether a catalyst is homogeneous or heterogeneous 1 2 3 4 Exposure to elemental Hg will generally poison a heterogeneous catalyst Exposure to polythiols will poison most homogeneous catalysts Light scattering studies to identify the presence of colloids heterogeneous Product selectivity studies eg polymer bound alkenes Catalyst Polymer H2 gt Polymer Catalyst HomoHetero Yield RhClPPh33 homo 100 NiOAc2 NaBH4 hetero RhnbdPR32 homo 90 PdC hetero IrcodPipr3 py homo 100 Catalysis Intro 6 Some Catalysis Terminology Turnover T 0 one loop through the catalyst cycle Typically one equivalent of reactant is converted to one equivalent of product per equivalent of catalyst Turnover Frequency T 0F 0r Turnover Rate the number of passes through the catalytic cycle per unit time typically sec min or hrs This number is usually determined by taking the of moles of product produced dividing that by the of moles of catalyst used in the reaction then dividing that by the time to produce the given amount of product The units therefore are usually just lime1 Note that the rate of a batch catalytic reaction is fastest at the very beginning of when the reactant concentration is the highest and generally slows down as the reaction proceeds stopping when all the reactant is used up Note the graph below for the production of aldehyde product from the homogeneously catalyzed reaction of vinyl acetate H2 and CO Vinyl Acetate Hyd roformylation samp ng from 2000 03mM catalyst 85 Cl90 pSl lg ICO autoclave causes pressure glitches 1800 Zquot i a 45 Upt ke curve 1600 k a 4 1400 X a 35 5 1quot 1200 l kobs00076mln1 Aldehyde 1000 I 3 LnA P Prod Lquot F I t 800 my a 25 600 Initial TOF 7 2 400 8TOImin 476TOIhr 7 15 200 W 0 5 10 1 Time hours a N z The TOF therefore will vary throughout the course of a batch reaction The Initial T 0F is de ned as the initial part of a catalytic reaction where the rate is the fastest and essentially linear A far better measure of rate is the observed rate constant kobs which allows one to reproduce Catalysis Intro 7 the entire product production curve given a set of reactant amp catalyst concentrations In the above graph the reaction is pseudof1rst order in excess reactant alkene vinyl acetate concentration 06 M catalyst 03 mM and kobs is determined from a In plot of the change in HzCO pressure reactant concentration versus time for this rxn When reporting kobs chemists often normalize it to a certain catalyst concentration 1 mM for example Turnover Number TON the absolute number of passes through the catalytic cycle before the catalyst becomes deactivated Academic chemists sometimes report only the turnover number when the catalyst is very slow they don t want to be embarassed by reporting a very low TOF or decomposes quite rapidly Industrial chemists are interested in both TON and TOP A large TON eg 106 1010 indicates a stable very longlived catalyst TON is de ned as the amount of reactant moles divided by the amount of catalyst moles times the yield of product Authors often report mole of catalyst used This refers to the amount of catalyst relative to the amount of reactant present 10 mole 10 TO 1 mole 100 TON 001 10000 TON ee enantioselectivity this de nes the enantioselectivity of an asymmetric catalyst that produces more of one optically active enantiomer R enantiomer for example than the other S enantiomer ee is defined as IRSl ee gtlt100 RS A catalyst that makes an equal amount of R and S enantiomers has 0 ee a racemic mixture 85 or higher is generally considered a good ee although that depends on what the best known catalyst can do relative to that being reported Catalysis Intro 8 Catalysis Data in Publications There is a lot of mediocrebad catalysis reported all the time in chemistry publications One often has to dig into the data to gure this out The things one wants to typically look for to tell whether there is good catalysis or not include 1 of turnovers performed more is better 2 TOF turnover frequency faster is better 3 Good selectivity for the product this includes chemoselectivity regioselectivity and enantioselectivity if applicable 4 Reaction conditions harsh Mild Unusual Concentrations To gure out the number of turnovers you need to know the amount of substrate reactant and catalyst moles equivalents reactant substrate moles equivalents catalyst Turnovers But authors often list these values in different ways and you may have to do some interpreting The most common alternate way of representing the substratezcatalyst ratio is mole This is especially common for organic chemists doing Pdcatalyzed coupling reactions 10 mole catalyst means that there is 10 as much catalyst as substrate on a molar basis This is equivalent to 10 turnovers 10 mole catalyst 10 turnovers These represent the theoretical maximum ofturnovers One also has to note the yield or the 0 conversion of 1 mole turnovers substra e into product to gure out the actual of 01 mole catalyst 1000 turnovers turnoversl 5 mole catalyst 20 turnovers 001 mole catalyst 10000 turnovers Table I Hydrocarboxylation of plsobutylstyrene l and Hydro carboxylation 2Vinyl6methoxynaphthalcne 2 Catalysis Intro 9 Example Consider the following catalytic data reported in a J Am Chem Soc communication very prestigious a number of years ago 0 R co H20 gt J HO R 1 or 2 product optical substrate L LPdC12 yield yield l SBNPPA 77038l0 89 83 S SBNPPA 7707710 80 55 S RBNPPA 7703310 39 81 84 R 2 SBNPPA 4204210 46 72 S SBNPPA 100510 71 85 S RBNPPA 4204210 48 76 R RBNPPA 77O3810 64 91 R Yield of pure material 1 Determined by optical rotation measure ments relative to those for the pure enantiomers reported in the liter ature9quot and confirmed by independent measurements of authentic pure S enantiomers in the authors laboratory Let s look at the last line of data from the table since that had the highest ee The third column contains the important information about the ratio of reactant often referred to as substrate chiral chelating ligand L and PdClZ The authors had 77 equivalents of reactant 038 equivalents of chiral ligand and 1 equivalent of Pd This means that the maximum number of turnovers they could do is de ned by the amount of reactant moles or equivalents divided by the amount of catalyst moles or equivalents equivalents reactant 77 maX turnovers equivalents catalyst Catalysis Intro 10 77 turnovers is small and not at all impressive Hydrocarboxylation however is a difficult catalytic reaction and doing it asymmetrically is even more impressive Of course 77 turnovers assumes 100 yield which they did not get The actual number of turnovers needs to be reduced by the yield which they report as 64 so the actual number of turnovers is actual turnovers 77 x 064 49 49 turnovers is barely catalytic What about the TOP Well you have to read a little footnote to nd how long they ran the reaction to get their 64 yield 18 hours at 1 atm of CO The TOF is the number of turnovers divided by the time 49 turnovers TOF 027hr 1 18 hr Well 027 tumovershr is also barely catalytic But that 91 ee is quite impressive isn t it Or is it The authors only added 038 equivalents of chiral ligand to 1 eq of PdC12 to generate at most 038 equivalents of chiral catalyst assuming one ligand per Pd This is rather unusual since one usually adds a little excess of chiral ligand to generate a chiral catalyst even when dealing with a chelating ligand There are examples where one can add less ligand than metal complex due to the fact that the metalligand catalyst generated is much more active than the starting metal complex itself But one almost always adds enough ligand or extra since the ligand can dissociate to generate as much of the presumed catalytically active species as possible Catalysis Intro 11 The ligand that the author is using is DO OH CO BNPPA This is being used under rather acidic conditions typically needed for Pdcatalyzed hydrocarboxylation and under these conditions it is highly unlikely that it would be able to function as a ligand Remember that the late transition metals don t particularly like oxygen donor ligands weaker bonding This fact makes the high ee s rather suspect And a number of research groups Hoechst Celanese Union Carbide etc have found although not published that the actual ee for this catalyst is close to 0 So it is often important to read the experimental conditions very carefully and with a critical eye Catalysis Intro 12 Consider the following catalytic data reported in a recent publication What information is missing Table 1 Biphasic hydrogenation reactions of arenes in the bmimBF4 ionic liquid and water with H4Ru4n5C6H54BF42 as the catalyst precursor Con Catalytic Reaction Reaction version turnovera Substrate system conditions mol mol 1 hrl Benzene Ionic liquid 60 atm H2 91 364 90 C 25 h Water 60 atm H2 88 352 90 C 25 h Toluene Ionic liquid 60 atm H2 72 240 39 90 C 3 h Water 60 atm H2 78 261 90 C 3 h Cumene Ionic liquid 60 atm H2 34 136 90 C 25 h Water 60 atm H2 31 124 90 C 25 h 0 Catalytic turnover is calculated on the assumption that the tetra ruthenium catalyst does not break down into monoruthenium fragments which is entirely consistent with the data Notes and references T The ionic liquid bmimBF4 was prepared using the literature method6 H4Ru4nC6H6BF42 is very soluble and stable in this ionic liquid and is readily characterised in the ionic liquid using IH N MR spectroscopy which revealed and spectrum similar to that in conventional solvents Hydrogenations were carried using a Parr stainless steel autoclave 300 ml fitted with either a glass or PTFE liner The catalyst HaRu4n5 C6H5BF42 was added together with the required amount of bmimBF4 ionic liquid The autoclave was then sealed and purged with hydrogen gas 999995 purity and the appropriate reaction pressure was then set at room temperature The autoclave was then sealed and heated to the required reaction temperature and stirred for the time period required After reaction the contents were then separated into organic and ionic liquid phases and the products analysed by 1H NMR spectroscopy and GC The only products observed were the perhydrogenated cycloalkanes there was no evidence for the formation of partially hydrogenated products or polymeric by products Catalysis Intro 13 Beller and coworkers have reported Angew Chem 2001 40 34083411 on hydroformylation catalysis using HRhCONaphos The table of catalytic data from their paper is shown below For experiment 1 how many turnovers did the authors do Clearly show how you calculate your number Is there any important data missing from this table Table 1 Hydroformylation of 1 and 2pentene with NAPHOSW Entry Olefin p T Yield 1 n i TOF bar l Cl l 11quot 1 1pentene 10 120 76 991 475 2 1pentene 50 120 88 973 550 3 2 pentene 10 120 22 8911 138 4 2pentene 50 120 7 5545 44 a Reaction conditions olefin 700 mmol 40 mL solution Rhacac CO2 001 mol 207 ppm Rh NAPHOSRh 51 16 h b No significant amounts gt 1 of other products apart from isomerized olefin were detected Catalysis Intro 14 What information is missing from the following Table of catalytic results they de ned the ligands used elsewhere in the paper How many turnovers are they doing Table 1 Asymmetric hydrogenation of methyl xacetamido cinnamatea 0 o H2 Ph OMe ph OMe NHAC NHAc 2a 3a Entry Ligand Solvent Conv Ee t2 min L 1 1a toluene 100 47 R 6 2 1b toluene 100 46 R 4 3 1c toluene 100 20 R 52 4 1d toluene 100 90 R 50 5 1e toluene 100 74 R 12 6 1f toluene 100 82 R 36 7 1g toluene 100 67 R 17 aConditions 1 mmol substrate 001 mmol RhCOD2BF4 catligand 12 15 ml solvent 25 C


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