Propylene oxide The Evonik-Uhde HPPO technology

Innovative · Profitable · Clean

Thys

senK

rupp

A companyof ThyssenKrupp

TechnologiesUhde

Table of contents2

1. Company profile 3

2. Overview 5

3. Fundamentals of propylene oxide 7

4. General process description 8

5. Process highlights 9

6. Process description of the new Evonik-Uhde HPPO technology 10

6.1 Reaction 10

6.2 Propene recycling 10

6.3 PO purification 10

6.4 Methanol processing 11

6.5 Purification of chemical-grade propene 11

Page

The Evonik-Uhde HPPO technologyInnovative · Profitable · Clean Innovative · Profitable · Clean

31. Company profile

The new hydrogen peroxide to propylene oxide (HPPO) process using propene andhydrogen peroxide as the feedstocks is the result of co-operation between EvonikIndustries and Uhde.

Uhde’s head officein Dortmund, Germany

Uhde, the Dortmund-based engineeringcontractor, with its highly specialised work-force of more than 4,900 employees andits international network of subsidiaries andbranch offices, has, to date, successfullycompleted over 2,000 projects through-outthe world.

Uhde’s international reputation has beenbuilt on the successful application ofEngineering with ideas to yield cost-effect-ive high-tech solutions for its customers. The ever-increasing demands placed upon process and application technology in thefields of chemical processing, energy andenvironmental protection are met througha combination of specialist know-how,all-round service packages, top-qualityengineering and impeccable punctuality.

The extensive international experience inthe design and construction of chemicalplants makes Uhde the ideal engineeringcontractor for PO plants using the newprocess and for the respective hydrogenperoxide plants.

Evonik is a leading international manu-facturer of hydrogen peroxide (H2O2).With an annual capacity of more than600,000 metric tons, Evonik’s IndustrialChemicals Business Unit is the world’ssecond-largest producer of this environ-mentally-safe bleaching and oxidisingagent. Extensive experience with boththe product and the new process makesEvonik the preferred supplier of H2O2for this application.

Evonik is the creative industrial groupfrom Germany which operates in threebusiness areas: Chemicals, Energy andReal Estate. Evonik is a global leader inspecialty chemicals, an expert in powergeneration from hard coal and renewableenergies, and one of the largest privateresidential real estate companies inGermany. The strengths are creativity,specialization, continuous self-renewal,and reliability. Evonik is active in over100 countries around the world. In itsfiscal year 2007 about 43,000 employeesgenerated sales of about €14.4 billionand an operating profit (EBITDA) of morethan €2.2 billion.

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Evonik and Uhde have jointly developed a co-product free process for the production ofpropylene oxide (PO) via hydrogen peroxide.Apart from the economic benefits, it offersnumerous further advantages compared withcurrent state-of-the-art processes.

In 2001, Evonik and Uhde announced an exclusivepartnership for the development of the new process. Evonik investigated the process anddeveloped a catalyst optimised for the particularpurpose, while Uhde contributed its expertise inprocess engineering and the design and con-struction of chemical and other industrial plants.At Evonik’s site in Hanau-Wolfgang (Germany),experts from the two companies further opti-mised the process parameters in a mini plantwhich included all recycle streams and reflectedthe complete production process. Since 2008 theEvonik-Uhde HPPO technology has been in suc-cessful commercial operation and has provenitself in the first plant of its kind.

The Evonik-Uhde process yields PO from propene and hydrogen peroxide (H2O2) using a special titanium silicalite (TS-1) catalyst. The advantages of the new process are clearlyapparent. Operation will be more cost-efficientthan the production processes currently used for PO, especially in view of significantly lowercapital investment costs which allow the investorto be more flexible in his investment decisions.In addition, the new process is environment-friendly, it is highly efficient and the only co-product obtained is water. Moreover, feedstockconsumption is low due to high specific yields(> 95% of propene).

The advantages of the Evonik-Uhde HPPO technology:

• co-product free

• efficient raw material consumption

• high performance catalyst with long lifetime

• low investment costs

The new technology is licensed by Evonik andUhde and the PO plants will be built by Uhde asthe contracting and engineering partner for thistechnology. As the preferred supplier, Evonik willsupply the H2O2 “over the fence” to the PO plant.

2. Overview

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Figure 1: Main applications of PO/world consumption of PO in percent

65 % Polyether polyols

polyurethanes (PUR), flexible and rigid foam

20 % Propylene glycols (PG)

polyester, pharmaceuticals, cosmetics

15 % Others

Propylene oxideMain applications

3. Fundamentals of propylene oxide 7

Propylene oxide (PO), C3H6O, is a colourless,low-boiling liquid of high reactivity and is nowone of the most important chemical intermediates,especially for the polyurethane and solvents in-dustry. Its polarity and strained three-memberedepoxide ring allows it to be opened easily byreaction with a wide variety of substances. Since the early 1950s it has become increasinglyimportant for the chemical industry. At present,more than 6 million metric tons of PO is producedworldwide, with consumption rates outstrippingGDP growth rates.

PO is a bulk chemical primarily used for theproduction of polyurethane precursors namelypolyether polyols, as well as for propylene glycoland glycol ethers. Polyurethanes are used in awide range of applications, including automobilecomponents, furniture upholstery, thermalinsulation, coating materials, sports shoes andsporting goods.

At present, two thirds of PO output is used forthe production of polyether polyols, followed byabout 20% for propylene glycols (PG) and about15% for propylene glycol ether solvents andothers.

Since 2008 the world’s first commercial scaleplant for the production of propylene oxidebased on the innovative HPPO process has

been in successful operation

4. General process description8

system which operates at elevated pressureand moderate temperature. The special designcombines an intense heat transfer with analmost ideal plug-flow characteristic, resulting ina high PO selectivity.

The quality and characteristics of the hydrogenperoxide have a substantial influence on theprocess parameters. Evonik has developed agrade of hydrogen peroxide specifically designedfor use as an oxidising agent in the epoxidationof propene.

Polymer-grade or chemical-grade propene canbe used as feedstock. If chemical-grade propeneis used, propane is separated from propene inan integrated propene rectifier.

The propene cycle of the PO plant is totally closed and the surplus propene recovered isreturned to the reaction section.

The crude PO contains some impurities whichare removed in the PO purification section bystate-of-the-art rectification under moderateconditions.

Water and small amounts of by-products areremoved in the methanol processing sectionand the purified solvent is recycled to the reactor.

The new Evonik-Uhde HPPO technology for theproduction of propylene oxide via H2O2 is shownin figure 2. The highly exothermic process takesplace under relatively mild process conditions.

In the reaction unit, the catalytic epoxidation ofpropene is carried out in the presence of a titaniumsilicalite catalyst using hydrogen peroxide (H2O2)in methanol as the solvent. The focal point ofthe development was the epoxidation reactor forthe synthesis of PO using a fixed-bed reaction

POpurification

Methanolprocessing

Reactionunit

Propene H2O2

Propene

recycle

MeOH

recycle

PO Waste water

Decompressing/Propene recyling

Figure 2: New Evonik-Uhde HPPO technology

5. Process highlights 9

Advantages of the new technology:

• Co-product free process

• Epoxidation reactor specially designed forhighly exothermic reaction conditionscombines an efficient heat transfer with analmost ideal plug-flow characteristic

• High performance catalyst with a long lifetime

• The process is free of chlorine

• Optional use of polymer-grade orchemical-grade propene feedstock

Economic benefits:

• Lower capital investment and energyconsumption compared with state-of-the-artPO technologies

• High specific yields resulting in low feedstockconsumption

• Stand-alone technology: no marketdependency on co-products

Environment-friendly production:

• Totally closed solvent and feedstock cycles

• The waste water, which contains smallamounts of by-products, can be sent to abiological or a thermal treatment unit

• All off-gas streams from the PO plant can be treated using state-of-the-art technologies. If chemical-grade propene is used, the surplus propane can be used as an additionalenergy source.

Expected consumption figures:

• Propene (at 100%) <0.77 kg/kgPO

• Hydrogen peroxide (at 100%) <0.75 kg/kgPO

Propylene oxide product specification:

• PO purity by GC(dry basis) weight-% min. 99.97

• Water (wt.ppm) max. 200

• Aldehydes, total (wt.ppm) max. 50

• Colour, Pt-Co (APHA colour) max. 10

6.1 Reaction

In the PO reaction process, the reaction ofpropene (C3H6) and hydrogen peroxide (H2O2)takes place in a methanol/water mixture using afixed-bed reactor with a special titanium silicalitecatalyst (TS-1 type).

6.2 Propene recycling

The product mixture leaving the reaction unit is decompressed and heated, resulting in apropene-rich gas phase which is compressed,condensed and returned to the reaction section.

The off-gas, which mainly contains inert com-pounds and a small quantity of oxygen from the decomposition of the hydrogen peroxide, is withdrawn and delivered to the battery limits.

6.3 PO purification

The depressurised liquid product mixture is thentransferred to the pre-separation section wherePO and dissolved propene are separated frommethanol and water. A C3 stripper removes theremaining C3 hydrocarbons from the PO/methanolmixture.

The PO distillate is purified in the PO columnand the remaining methanol and water as wellas the small quantities of impurities are takenoff in the bottom product. The PO distillatemeets the highest quality standards.

6. Process description of the new Evonik-Uhde HPPO technology

Product mixture

CWReaction section

Propene

H2O2

Methanol Offgas tobattery limits

Recycle propene toreaction section

Purge gas systemCompressor system

from PO purificationsection

CW

Steam

Flash system

Product mixture

Recycle propene

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C3H6 + H2O2 C3H6O + H2O propene hydrogen peroxide propylene oxide water

The process is characterised by mild processconditions with temperatures below 100°C leadingto low formation of by-products. The pressure inthe reaction unit is about 30 bar.

Due to the optimised process parameters, ahigh propene-based PO selectivity of more than95% can be obtained.

The heat of the highly exothermic reaction isremoved by an integrated cooling system. Afterreaction, the product mixture containing mainlymethanol, water, propene and PO is withdrawnfrom the reactor and depressurised to a pressureslightly above atmospheric pressure.

Reaction section Propene recycling section

to Propenerecycling section

PO product

to tankfarm

Methanol/Water

Pre-separation C3 stripping PO purification

Recycle methanol

Waste water

Methanol processing

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6.4 Methanol processing

The methanol in the methanol/water mixturewithdrawn from the bottom of the pre-separationcolumn and from the bottom of the PO columnis separated from the water in the methanolprocessing section. The emanating overheadmethanol stream is returned to the PO reactionsection.

The bottom product from the methanol column,which contains water and small amounts ofhigh-boiling by-products, is delivered to the battery limits.

6.5 Purification of chemical-grade propene

If polymer-grade propene is used as the feed-stock, the recycled propene is fed directly to thereaction section. Where chemical-grade propeneis used, considerable amounts of propane arecontinuously introduced into the process withthe fresh propene stream. Propane acts as aninert diluent in the reaction system. In order tokeep the propane concentration at a constantlevel, the surplus propane is removed in thepropene purification column.

The column increases the propene concentrationin the overhead product while the bottom productaccounts for the propane balance. The bottomproduct is sent to the battery limits while thepropene stream is returned to the PO reactionsection.

PO purification section Methanol processing section

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