Karl-Winnacker-Institut

Direct synthesis of hydrogen peroxide with

CO2 as solvent in a membrane micro reactor

A. Pashkova1, U. Krtschil2, C. Hofmann2, V. Hessel2, D. Kirschneck3, W. Linhart3

1 Karl-Winnacker-Institut, DECHEMA e.V2 Institut für Mikrotechnik Mainz GmbH

3 Microinnova Engineering GmbH

10th December 2009Osnabrück

Technical Chemistry

Outline

Motivation

Hydrogen peroxide direct synthesis: a brief

overview of concepts

Project idea, goals, partners and responsibilities

Catalyst preparation

Double membrane micro reactor

Experimental set-up

First test measurements

Summary and outlook

Technical Chemistry

H2O2 – efficient and environmentally friendly

Annual global consumption of H2O2 is ca 3·106

t/y[1]

Expected growth (just for the

HPPO-Process) ‏

is ca 2·105 t/y[1]

[1] C. Brasse und B. Jaeger, Elements 17 (2006) 4-7[2] J.Fierro et al., Angew. Chemie 118 (2006) 7116-7139[3] S. Schlag et al.„Hydrogen peroxide“, Report, SRI Consulting (2009)

Applications in Europe [2]World consumption [3]

+ “Green” chemical, the only by-product is water

+ Higher activity and selectivity than molecular oxygen

H2O2 benefits

– Relative high manufacturing price 0.53-0.80 € /kg

– Complicated industrial synthesis according to the “Anthraquinone Process”:

• expensive and complex solvent system • waste of solvent due to side reactions• energy intensive separation and concentration steps• economically viable only for large scale production

units (>40 kt/a)

H2O2 limitations

Technical Chemistry

Direct synthesis of H2O2: a brief overview of concepts

+ Separate H2 and O2 supply ⇒ improved safety– Dense Pd layer ⇒ limited mass transfer of H2

– Complicated membrane preparation

Dense palladium - membrane

V. Choudhary et al., Angew. Chemie Int. Ed. 40 (2001) 1776S. Abate et al., Catalysis Today 104 (2005) 323*L. Wang et al., Applied Catalysis B 79 (2008) 157

Productivity*: 9,5 [gH2O2 m-2 h-1]

Support: tubular ceramic membranes (Al2O3/TiO2 etc.)

Safety: Wide explosion range of H2/O2mixtures (4-94 vol.%)

Activity: Low reactant concentrations dueto low solubility of H2 and O2 ⇒ high

pressure; organic solvents; additives

Selectivity:water is thermodynamically more stable

Pd or PdX (X = Au, Pt) supported catalyst

*C. Samanta, Appl. Catal. A 350 (2008) 133 Productivity*: 43,5 [gH2O2 gPd

-1 h-1]

Support: inorganic powder (Al2O3/TiO2 /zeolites etc.)Porous palladium - membrane: catalytic

membrane contactor

Pashkova A. et al., Chem. Eng. J. 139 (2008) 165

+ Separated H2 and O2 supply ⇒ improved safety

+ Highly dispersed Pd nanoparticles (no dense Pd layer ⇒ increased productivity

? Moderate mass transfer limitations

Productivity:43,2 [gH2O2 gPd

-1 h-1] / 206 [gH2O2 m-2 h-1]

Liquid

Gas

Gas

Membrane length

Mem

bran

e ra

dius

Gas/liquidcontact

Liquid

Active material(e.g. Pd; Pd/X)

H2O2

(H2O)

thickness: 5 – 50 µmpore-Ø: 100 nm

thickness: 10 – 100 µmpore-Ø: 0,2 – 0,8 µm

Support

Intermediatelayer(s)

thickness: 1 – 3 mmpore-Ø: 3 µm

1 – 10 µm

Gas (overpressure)

Surface Layer/Catalytic zone

H2

O2

Technical Chemistry

Project ideaLimitations of the membrane contactor concept

Limited H2 transport only by diffusion from the centre of the channel (din = 7 mm) to the catalytic zone (channel wall) in the conditions of laminar flow

Use of organic solvents (methanol, ethanol) and presence of additives (acid, halide) may not be favourable for a lot of H2O2 applications

CO2 as mediumnon toxic, non flammable easy separable from theproducts by simple expansion of the reaction mixtureenhanced transport propertiesof the reactants

Aqueous solutions preferred ⇒search for alternative solvents

Use of membranesenhanced process safety –separate supply of H2 and O2direct supply and even distribution of H2 und O2along the micro channel

Keep the benefits of a membrane

Aim of the projectTo develop a compact and efficient continuous process for “on site” production of aqueous hydrogen peroxide solutions, based on the direct oxidation of H2 with O2 in liquid or supercritical CO2 over Pd

supported catalysts in a special micro structured double membrane reactor

Micro reaction technologyenhanced heat- and mass-transfer and reduced limitations on reaction kineticsimproved process safetyrelative simple scale-up(numbering up)

Smaller channel sizes are preferred

Technical Chemistry

Project partners and responsibilities

Milestones19 Months: Collect positive results from the laboratory experiments (with

catalyst activity and selectivity relevant for a technical process) 24 Months: Choose one preferable H2O2 application 29 Months: Finish with the scale-up und design of the prototype

support for the automation of the experimental set-up techno economical analysis of the process

MicroinnovaEngineering GmbH

catalyst preparation design and manufacture of the double membrane micro reactorfor the laboratory experiments scale-up and design of a prototype reactor

IMM Mainz GmbH

design, construction and putting into operation of the experimental set-up proof of concept at a laboratory scalecatalyst screening experiments and characterisationprocess simulation demonstration of a prototype process (scale-up)

KWI/DECHEMA e.V.(coordinator)

Technical Chemistry

Catalyst preparation / IMM

air80 mgPd(NH3)4(NO3)21% Pd/TiO24

N287 mgPd(NO3)21% Pd/Al2O35

air94 mgPd(NO3)21% Pd/Al2O31

N287 mgPd(NH3)4(NO3)21% Pd/Al2O36

air78 mgPd(NO3)21% Pd/TiO23

air82 mgPd(NH3)4(NO3)21% Pd/Al2O32

Calcinationatmosphere

Catalyst mass

Pd precursorCatalyst

One test micro reactor = one catalyst typeChannel geometry (l, w, h): 150 x 0,5 x 0,6 mmNumber of channels per plate: 20After coating two plates are welded togetherMaximal pressure: 150 bar; Maximal temperature: 50°CVolume flow: 5 to 20 ml min-1

Aim of the catalyst screening experimentsTo identify the most suitable catalyst for the direct synthesis reaction in an earlier project phase.

thickness of one coating layer is 50 – 60 µm

can be varied through multiple coatings

Wash coating procedure

catalyst powder

support material

Al2O3, TiO2

precursorPd(NH3)4(NO3)2,Pd(NO3)2

catalyst suspension

stabilizerAcetic acid

binderPVA

coating of the channels

drying and calcination

impregnation

450°C, 6 hoursin air or N2

Pd content0,5; 1; 2%

Technical Chemistry

Double membrane micro reactor / IMM

Reactor components and dimensions

Plates: 316 L ssO-Rings: Viton

Channel dimensions (l,w,h) ca 500 x 0,5 x 2 mm

Reactor dimensions (l,w,h) ca 600 x 60 x 60 x mm

Reactor volume 2 x ca 10 ml

Weight: ca 20 kg

Possible membrane materialsmicro sieves polymer membranes planar porous ceramics

CatalystsSupported Pd or PdX (X = Au, Pt) in the form of wall coating or a packed bed

membrane(O2)

O2

O2

H2

reactionmedium

catalyst

membrane(H2)

gasdistributor

coolingchannel

spacing frame (optional)

catalyst plate/ CO2channels

spacing frame (optional)

H2 membraneH2 supply

O2 supply

cooling

cooling

O2 membrane

Technical Chemistry

H2O2, H2O(CO2, O2)

CO2

(O2/H2)

expansionvalve I

preheater

liq.

gassepa

rato

rCO2 tank

CO2

pump

cooling

N2

O2

MFCfilter

H2

PI

expansionvalve II

rotameter

Gas analysis

filter

filter

check valve

check valvePI

microreactor

MFC

MFC

MFC

PM -101 PE - 103

pressure module expansion module

reactive module

gas supply

Experimental set-up / KWI designed and constructed together with NWA analytische Messgeräte GmbH, Lörrach/Dsuitable for experiments with both liquid and supercritical CO2

P = 60 to 200 bar; T = -10 to + 50°C; F(CO2) = 50 to 350 nL h-1 = 100 to 700 g h-1

Technical Chemistry

H2O2 direct synthesis experiment in liquid CO2 / KWI

Gas supplyMFC(N2) = 30 ml min-1 = 8,72x10-2 mol min-1

MFC(O2) = 20 ml min-1= 5,81x10-2 mol min-1

MFC(H2) = 10 ml min-1= 2,91x10-2 mol min-1

H2/O2/N2/CO2 = 7,1/14,2/21,3/57,4 %

System parametersT1(heater) = 20°CP1(system) = 69 barT2(exp.valve I) = 80°CP2(separator) = 16,9 bar

0 5 10 15 20 25 30 35 40 45 50 55 60 65 700

10

20

30

40

50

60

70

80

CO

2 gas flow [L m

in-1]

Pre

ssur

e [b

ar]

Time [min]

P1 System

0

2

4

6

8

10

CO2 Flow /gas/

P2 Separator

F(CO2-g) = 5,7 L min-1

F(CO2-l) = 14 ml min-1

Catalyst 5: 1%Pd/Al2O3, 87 mg

Inactive catalystExperiments with conventional solvent (MeOH) required

Decomposition inside the set-upTry to separate the products before the expansion (cooling trap?)Find a suitable chemical reaction for online H2O2 consumption (e.g. “in

situ” H2O2 generation for an oxidation process)

+ stable operation

- no H2O2 or H2O in the separator after one hour

Technical Chemistry

H2O2 direct synthesis with conventional solvent / KWI

N2

O2

MFCfilter

H2

filter

filter

check valve

check valve

microreactor

MFC

MFC

MFCPI

saturator

H2/O2/N2

expansionvalve

MeOH/H2O2/H2O

air

N2

air

air

Calcination atmosphere

1,35,7Pd(NO3)21% Pd/Al2O3

63,58

14,9

10,32

Productivity[gH2O2 gPd

-1 h-1]

9,4

10,1

9,7

Selectivity[%]

Pd(NO3)21% Pd/Al2O3

Pd(NO3)21% Pd/TiO2

Pd(NH3)4(NO3)21% Pd/Al2O3

Pd precursorCatalyst

Experimental conditionsSolvent MeOH without additives (acid and bromide)Psystem = 60 barH2/O2/N2 = 5/32/63 vol %

Single pass experiments

+ active catalysts for the direct synthesis of H2O2 with a conventional solvent

- low selectivity probably due to the lack of additives ⇒ catalyst modification with halide during preparation

- low productivity due to low Pd amount ⇒ multiple coating

Results summary

Technical Chemistry

H2O2/CO2 interactions

H2O2 solubility in CO2T = 40°C; P = 80 – 160 barVery low solubility: from 1,46x10-4 g/g CO2 for 80 bar to 1,37x10-4 g/g CO2 for 160 bar

VTP, Ruhr Universität Bochum

No data was found on solubility of H2O2 in CO2 (liquid/supercritical)

Carbagas

Experiments in a high pressure view cellFirma NWA/Prof. Krez , Center for Isolation of Natural Substances, Maribor,Slovenia

Phase observationsfor 4 – 6 % H2O2/H2O; T = 30°C; 40°C; P = 50 – 170 barCO2 is always upper phase

H2O2 Extraction with scCO2 from aqueous solutionFor 4 – 6 % H2O2/H2OT = 30/40°CP = 50 – 170 barS/F = 2,0 – 4,7 kg CO2/kg Feed

0 20 40 60 80 100 120 140 160 1800

1

2

3

4

5

6

S/F = 2 kg CO2/kg Feed; 30°C S/F = 4,7 kg CO2/kg Feed; 40°C

H2O

2 [Gew

. %]

Druck [bar]

H2O2 /CO2 behaviour

+ beneficial for product separation

- unfavourable concerning the homogeneity in the

reaction channel

Technical Chemistry

Summary and outlook

Summary

completed and put into operation the

experimental set-up; recompression of the CO2

still has to be implemented

successfully prepared catalysts (micro reactors)

for screening experiments

Identified promising catalytic system Pd/TiO2 in

a conventional solvent

gathered first knowledge about the behaviour

of the system H2O2/scCO2

Outlook

catalyst optimisation: higher Pd loadings;

modification with halide groups

catalyst characterisation: BET, porosity,

Pd particle size, Pd dispersion

further experiments with CO2 as solvent

and optimisation of the experimental set-up

Technical Chemistry

Acknowledgements

Prof. Roland Dittmeyer*Laurent Bortolotto

Wolfgang RüthHorst Fiege

Technical chemistry group at KWI

* now at Karlsruhe Institute of Technology

Thank you for the attention !

Time for discussion ....

Financial support Project partner