Decomposition of Hydrogen Peroxide

Transcription

1 Decomposition of Hydrogen Peroxide over Gold and Palladium as Catalysts Katie Castroagudin Allyson Mackavage Miguel Ocampo Arpit Patel Advisors: Prof. S. Podkolzin and Prof. R. Besser

2 Contents Introduction Literature survey Experimental lset Up Catalyst characterization Determination of Reaction mechanism and rate law Project Updates

3 Introduction Objective To derive kinetic data for decomposition of hydrogen peroxide over gold as a catalyst. Weak acid,strong and cheap oxidizing agent. Application bleaching i and oxidizing i agent It is produced by auto oxidation of 2 alkyl anthrahydroquinone.

4 Introduction Economics of the process depend heavily on effective recycling of the quinone and it is very expensive million tonnes million tonnes.

5 Introduction Direct synthesis from hydrogen and oxygen? Problem Thermodynamically ll it favors the production of water. Hydrogen peroxide has a tendency to decompose on its own and catalyst can accelerate decomposition.

6 Introduction 2009 Catalyst development was announced by the workers at the Cardiff university specifically usinggold palladiumgold nano particles. Found that gold and nanoparticles reduces the decomposition with no acid required. Importance Environmental lfi friendly process,cheap and efficient process.

7 Background Literature: Gold as a Catalyst Gold is a poor catalyst in bulk, but effective in nanoparticle form Gold nanoparticles are effective catalysts in both Hydrogen Peroxide synthesis and decomposition Specifically when supported by oxides h l l Three previous experiments involving gold as a catalyst were reviewed:

8 Isihara et al Looked at oxidation of Hydrogen using gaseous Oxygen Used Au catalyst with various oxide supports Also found that the addition of Palladium (Pd) with the Au further increased the formation rate of Hydrogen Peroxide

9 Ishida et al Studied decomposition of Hydrogen Peroxide and glucose oxidation Used gold nanoparticles for catalysts Nanoparticles were supported on various polymer beads

10 Ma, Li, and Wang Studied the synthesis of Hydrogen Peroxide Used different sized gold nanoparticles il for catalysts Supported on Ti and TiO 2

11 Preparation of Catalyst Researcher Support of Catalyst Preparation of Catalyst Isihara et al SiO 2 and some variations Incipient Wetness technique (HAuCl 4 + SiO 2 ) Ishida et al Commercial plastics including PMMA, PS, PANI Direct deposition of gold nanoparticles onto polymer beads in water Ma, Li, and Homogenous Deposition i Precipitation i i Ti and TiO Wang 2 (HDP) Urea was the precipitator

12 Techniques Used Researcher Chemical Reaction Reaction Conditions Reaction took place in water that had the catalyst Isihara et al 2H 2 O 2 2H 2 O + O 2 suspended in it. Decrease in H 2 O 2 concentration was measured. Ishida et al 2H 2 O 2 2H 2 O + O 2 intervals, the concentrations were measured using Reaction took place in solution. At various titration to determine the reaction rate. Ma, Li, and Wang Synthesis occurred in an autoclave equipped to measure the pressure of the gases. Final H 2H 2 O + O 2 2H 2 O 2 O 2 2 concentration was determined using iodometric titration (starch as indicator).

13 Results Researcher 2H Variables Observations Noted 2 O 2 2H 2 O + O 2 Isihara et al Ishida et al Ma, Li, and Wang Catalyst (compared to previous experiments) Addition of Palladium to catalyst Size of Au nanoparticles Type of polymer support Au particle size Temperature p of calcination Urea concentration in catalyst preparation Au catalyst supported with SiO 2 is active without addition of halogen compound. Rather, determining factor tends to be the activation of Hydrogen on the catalyst The effectiveness of catalysts was more dependent on type of polymer supports than size of nanoparticle Increased temperature of calcination increases the catalysts particle il size Increased urea concentration decreases the catalysts particle size

14 Conclusions Drawn Researcher Isihara et al Ishida et al Conclusions Hydrogen Peroxide formation rate decreased with time because at the beginning of the reaction, the catalyst is performing optimally, but its performance decreases as the reaction ensues Adding Pd to the catalyst is effective because it improves the H 2 activation The strong correlation between the rate of decomposition and the type of polymer support is due to the strength of interactions between the gold nanoparticles and the atoms in the polymer backbone Ma, Li, and Wang Smaller catalyst size promotes higher catalytic activity (due to larger surface area for chemical interactions) In comparing different types of supports it was noted that varying the supports also has a large effect on the reaction rate.

15 Background Literature: Palladium as a Catalyst There is more research on Palladium than for Gold Palladium effective catalyst in both Hydrogen Peroxide synthesis and decomposition i Three previous experiments involving palladium as a catalyst were reviewed:

16 Voloshin, Lawal Looked at direct combination of H2 and O2 Simultaneous Process Synthesis of H2O2, synthesis of water, decomposition of H2O2 and reduction of H2O2 by H2 Tested the concentration of H2O2 and H2 on the rate of reaction Pd/SiO2 catalyst using Langmuir Hinshelwood method

17 Samanta, Choudhary Studied decomposition of Hydrogen Peroxide and hydrogenation to water Used Palladium catalyst coupled with the use of halides hlid in different concetrations

18 Preparation of Catalyst Researcher Support of Catalyst Preparation of Catalyst Voloshin, Lawal SiO 2 and some variations Sol gel method with PdCl2 (catalyst ground so that microparticles were used) Samanta, Choudhary Al 2 O₃ Fine powder form of Pd (5 wt.%)/al 2 O₃ catalyst which was prepared fromthe Pd/Al 2 O₃ by its oxidation in air

19 Techniques Used Researcher Chemical Reaction Reaction Conditions Voloshin, Lawal 2H 2 O + O 2 2H 2 O 2 The flow rate of the liquid solvent was controlled by an HPLC pump and the solvent was combined with a micromixer. Concentration was measured with potassium permanganate by way of titration. Samanta, Choudhary 2H 2 O 2 2H 2 O + O 2 Reaction took place in solution. At various intervals, the concentrations were measured using titration to determine the reaction rate.

20 Results Researcher 2H Variables Observations Noted 2 O 2 2H 2 O + O 2 Voloshin, Lawal Concentration of hydrogen peroxide Presence of sulfuric acid Au catalyst supported with SiO 2 is active without addition of halogen compound. Rather, determining factor tends to be the activation of Hydrogen on the catalyst Sulfuric acid inhibits the decomposition of hydrogen peroxide Samanta, Choudhary Type of halide used Concentration of hydrogen peroxide Oxidation state of Palladium Presence of acid Strong dependence on which halide was used Also, the oxidation state of the Palladium affected the rate. Pd rather than PdO yielded greater results The catalyst had little affect on the results

21 Conclusions Drawn Researcher Voloshin, Lawal Conclusions Hydrogen Peroxide formation rate decreased with time because at the beginning of the reaction, the catalyst is performing optimally, but its performance decreases as the reaction ensues The extra exposure to the catalyst reduce the rate of the reaction (primarily formation and reduction) Samanta, Choudhary The many variables affected the hydrogen peroxide decomposition and the halogen inhibition in order would be I > Br > Cl > F. With this many variables that have a strong influence on the rate of reaction, a combination must be arranged to optimize the reaction.

22 Experimental Setup Plan Plan: Start from setup from last summer, run and determine reaction rates using manganese dioxide, then implement complexities Complexities Add thermal bath for temperature variation and control Add hydrogen stream

23 Block Diagram Syringe Pump PC H2O2 in Reactor H2O2+H2O+O2 stream O2 out O2 out Sample Vial Aalborg Flowmeter Ice

24 Other setup considerations Steel Tubing Oil Bath Steel Tubing Syringe Pump H2O Bath H2 in 1 H2 cylinder Reactor 2 H2O2 in PC H2O Bath O2 out O2 out Sample Vial Ice Aalborg Flowmeter

25 Setup Ctd. Current Issue Planned Solution Cleaning Reactor after each trial with different catalysts Ensure that reactor is clean and flush it with methanol / distilled water Water buildup in flow meter causes erratic data Run air through flow meter after each use to dry it Hydrogen Peroxide decomposes in syringe dispenser This is not a big issue, as long as we maintain a steady flow rate Pressure buildup due to convergence of catalyst in reactor exit Use enough catalyst to not have blockage

26 Setup Ctd. Other considerations: Use 1/8 tubular reactor Easier catalyst prep and exchange (no morecleaning) Batch reactor Metal or glass container with stirrer to measure partial Metal or glass container with stirrer to measure partial pressures

27 Catalyst Characterization Catalyst preparation Preparation of primary solid(incipient wetness impregnation) Treatment of intermediate solids(calcination) Forming method( Crushing) Characterization of surface properties p by surface adsorption method(chemisorption or Physisorption)

28 Catalyst Characterization Spectroscopy(Used to measure physical property and chemical composition) Raman Spectroscopy (Used to determine vibrational,rotational and low frequency modes in a system) H O O H or H O O H (Split of the bond)

29 Determination of Reaction mechanism and rate law General mole balance equation Apply specific reactor design equations(plug flow reactor) Reaction mechanism Determine Rate law(based on the slowest step)

30 Determination of Reaction mechanism H 2 O 2 H 2 O+0.5O 2 and rate law Rate expression (C H2O2,in C H2O2,Out )/[(Weight of catalyst)*(time)] A B+C Determination of order of the reaction: Zero order A/ t (constant for differrent runs) First order (ln A)/( t) (constant for differrent runs) Second order ( /[A])/( t) (constant for different runs)

31 Determination of reaction mechanism and rate law Dependency of rate: Rate α k *[H 2 O 2 ] a *[H 2 ] b *[O 2 ] c k= A*exp ( Ea/R*T)(Temperature dependency) Determine rate law based on the order of the reaction and reaction mechanism Plot the graph of Rate of reaction Vs Concentration of H2O2 at various temperatures. Plot ln k Vs 1/T Determine activation energy at different rates.

32 Status Updates as of 06/05/09 Neslab RTE 111 heater is working Silicon dioxide water absorption experiment Leak tests conducted Some chemicals received (gold, palladium and hydrogen peroxide)

33 Experimental Plan for the coming weeks Experiments on basic setup Run H2O2 with different flowrates and catalayst amount Determine reaction rate from oxygen flowrate out [mol/min*g] Miguel Catalyst preparation Katie, Allyson Cut 1/8 tubular reactor We think this is an easier alternative to the old microreactor Add complexities to setup Start conductingexperiments with new catalysts

34 Any Questions?