Advances in Methanol Synthesis

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Advances in methanol synthesis

For many years, methanol has

been used primarily as achemical intermediate in

manufacturing plastics and resins,then more recently in the manufac-ture of methyl tertiary butyl ether

(MTBE) for use as a lead anti-knockreplacement and octane enhancer,allowing a methanol derivative toenter the transportation fuel chainin a signicant way for the rsttime. However, now methanol is

being seen as a product that can beintroduced directly into the gaso-line pool by blending, allowingindigenous resources to be usedand providing a diversity of supplythat can help to reduce dependence

on crude oil and attempt to breakthe cycle of apparently ever-escalating oil prices.

China has introduced a nationalM85 standard that sees gasoline

blended with 85% methanol, whichhas been manufactured usingChinas cheap and abundantsupplies of coal, helping to reduceits dependence on expensiveimported oil.

In the US, there is considerablesupport for the Open Fuel Standard

Act, which, if passed, would call forcar manufacturers to introduce ex-ible fuel vehicles that canrun on methanol/ethanol/gasolinemixtures. Currently, there is littlemethanol production left in NorthAmerica, but the development ofshale gas is set to reduce naturalgas prices signicantly in NorthAmerica. And, like China, the UShas abundant coal reserves, which,through methanol, could be

used to displace oil imported fromabroad.

In this article, we will look at

Ctlt wth hgh nd tbl ctvt nbl ct vng nd bt

utut n thnl ductn

Terry FiTzpaTriCk nd Tom HiCks

Johnson Matthey Catalysts

methanol synthesis catalysts anddiscuss the various changes thathave occurred in the Katalco rangeof catalysts against the backdrop ofchanging industry requirements.

mthnl ductnICI initiated work on catalysts formethanol synthesis in the 1920s,when the only commercial processoperated at high pressure. Follow-ing early research on copper-zinccatalysts, ICI announced the LowPressure Methanol (LPM) processin 1963 and the rst single-trainproduction unit started operation in1966.

JM Catalysts has recently devel-oped a new generation of copper

zinc methanol synthesis catalystscalled Katalco Apico. This extendsthe performance of the Katalco 51

series catalysts an improvementthat is a step change in methanolsynthesis catalysis.

mthnl nth ctltSince the initial development of the

rst copper-zinc low-pressuremethanol synthesis catalyst, Katalco51-1, continuing developmentprogrammes have improvedperformance in terms of activity,

by-products production, strength,shrinkage and overall life. The orig-inal catalyst was designed forapplication in the multi-bed ICIQuench lozenge converter, and anearly variant, Katalco 51-2, quickly

became the industry standard. Asadditional technologies were devel-

oped, different types of converterwere used, the most noteworthy

being gas-cooled and steam-raisingin both axial and radial ow cong-urations. These often imposedifferent requirements on the cata-lyst, so JM Catalysts has developeda range of synthesis catalysts.

It is worth considering the vari-ous changes that have occurred inKatalco catalysts against the back-drop of changing industry

requirements. These changes do notcome from any one aspect of thecatalyst. The enhancements have

www.eptq.com CATALYSIS2010 47

JM

CompetitorA

Brotitep

moC

Others

Fgu 1 Methano technoogy market shares

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bng n

duct tht cn b

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nt th gln lb blndng


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such as sulphur and, in some cases,iron and nickel carbonyls broughtinto the loop with fresh syngas alsocontribute to deactivation or die off.Thus, key formulation requirementsare stabilisation of the coppersurface area and self-guardingagainst poisons.

One of the major contributors toa signicantly increased in-serviceactivity was the incorporation ofmagnesia (MgO) into the formula-tion during the early 1990s. Thisgave rise to Katalco 51-7 and has

been incorporated in subsequentvariants Katalco 51-8 and Katalco51-9. The benet from incorporatingMgO is evident from Figure 4, andthe signicant improvement rela-tive to Katalco 51-2 in terms of bothinitial and nal activities is illus-

trated in Figure 5.Activity testing is a specialised

technique comparing aged activitiesto the catalyst Katalco 51-2. Ageingis reliably simulated by deactiva-tion in a controlled and reproduciblemanner using elevated tempera-tures and pressure plus arepresentative synthesis gasmixture, before measuring activityunder standard conditions. A typi-cal test regime measures the activity

after 144 hours on-line, represent-ing approximately three months inan operating methanol plant. Theresults have been validated over theyears using data from operatingcharges in plants and side-streamreactors on our own plants.

Activities are regularly comparedwith the leading competitive offer-ings, and the most recentcomparison in Figure 6 clearlyshows the relative benecialperformance of Katalco 51-9S. The

higher and, more critically, stableactivity allows operation at lowertemperatures, favouring the reac-tion thermodynamics and loopcarbon efciency, minimising ther-mal sintering and giving benets inincreased methanol output andreduced by-product formation. Thereduced rate of activity loss trans-lates into a longer period ofoperation between catalyst changes.

Ctlt tngth nd hngDeclining strength and activitywere originally the limiting factors

been generated by identifying and

understanding the role of the keycomponents in the formulation andthe catalyst manufacturing processitself, as well as improvements inmanufacturing control.

Ctlt ctvtThe methanol synthesis reaction isan example of a structure insensi-tive catalytic reaction one inwhich the activity is whollydependent on the total exposed

copper area and not affected by thestructure of the crystallites. Figure 2illustrates this direct relationship

between activity and copper surfacearea for catalyst operating underindustrial conditions.

This relationship led to sugges-tions that maximum activity would

be achieved with the highest CuO

content in the fresh formulation,but this ignored the impact offormulation. As Figure 3 shows,variations in the CuO:Al

2O

3 ratio

have a marked effect on therelative activity, as shown in accel-erated life tests.

High initial activity, while impor-tant, is not paramount, as theeffective useful life of the catalystwill be governed by its stabilitywith time, so the formulation must

also stabilise the copper surfacearea under the process conditionsto which it is exposed. Thermalsintering is a key mechanism forsynthesis catalyst deactivation withoperation at temperatures as highas 315C, depending on reactortype. Commonly found poisons

48 CATALYSIS2010 www.eptq.com

Fgu 2 Variation in synthesis catayst activity with copper surface area

Fgu 3 The impact of catayst formuation on catayst activity

Activity

Optimum ratio

Al2O3


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of the catalysts operational life.Due to the high copper content,initial catalyst reduction and devel-opment of the copper surface arealeads to major changes in the physi-cal structure, which is manifestedin terms of shrinkage and reducedstrength. Low strength during oper-ation, especially during upsetconditions, can lead to physical

breakage of the pellets, givingincreased pressure drop thatreduces efciency as well as affect-ing gas distribution through thecatalyst. High shrinkage also leadsto distribution problems and areduced volume of active copper inthe reactor. These properties arecritical, for instance, in a steam-raising reactor such as the axialow catalyst-in-tube design,

where the catalyst duty is quitearduous both in terms of thevolume of material charged and thecrushing forces to which the cata-lyst is exposed during thermalcycling.

Initially, in the oxidised state, thecatalyst must be strong enough towithstand the rigours of charginginto the chosen reactor design with-out breakage. Too high an initialas received strength derived from

a high pellet density can be a disad-vantage, leading to diffusionallimitations within the catalyst,affecting overall activity. Throughan understanding of the formula-tion and manufacturing parameters,Katalco 51-9S has been designedwith a high pellet density, giving amuch enhanced strength bothinitially and in operation withoutadding any diffusion limitations, asshown in Berty reactor tests andcommercial experience.

The most readily obtainablemeasure of strength is the meanhorizontal crush strength (MHCS),appropriately measured across theweakest pellet dimension. Occasion-ally, the mean vertical crushstrength (MVCS) is reported, butthis can be misleading, being anorder of magnitude higher in theas received state.

As a result of improvements tothe catalyst formulation and manu-

facturing process, pressure dropincrease is no longer a limitingfeature of normal plant operation.

Fgu 5 Kataco 51 series activity enhancement

Fgu 4 Effect of incorporating magnesia on copper surface area

Fgu 6 Comparison of commercia catayst activities



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Fgu 8 Pressure drop stabiity of Kataco 51-9S with time

reaction heat removal systems.

These include, but are not limitedto, the direct quench-cooled adia-

batic converter design, the axialsteam-raising catalyst-in-tubedesign or the catalyst-in-shell-side,gas-cooled design such as the tube-cooled converter. Furthermore, thesavings through economies of scalethat might be accrued from build-ing world-scale methanol plants canbenet from the use of radial owconverters such as the Davy Process

Technology radial steam-raisingconverter.

C tud: Ttn mthnlThis Lurgi-designed plant has anameplate capacity of 2500 tpd andthe synthesis loop comprises twoparallel steam-raising converters,

each charged with 60m3 of Katalco

51-9S. Experience has shown thatwith this type of reactor carefulinitial catalyst charging is essentialto ensure minimum pressure dropvariation between tubes, to give aneven ow distribution and maxi-mum use of the relatively smallvolume of catalyst. The catalyst has

been producing record productionlevels of 2600 tpd since May 2005,giving signicant nancial benet.

As a result of the enhanced

performance of the catalyst, anextended run of four years isplanned. JM Catalysts has provideddetailed technical support through-out, carrying out frequentperformance optimisations. Figure7 conrms the activity achieved,which is 20% greater than Katalco

Fgu 7 Activity of Kataco 51-9S


In particular, the introduction ofpost-pellet treatment to the manu-facturing process in 2001 hasresulted in catalysts that have muchgreater reduced strength and aslittle as 5% shrinkage on reduction.

Catalyst lives of four to six years,and occasionally as long as eightyears, are commonplace, even inthe arduous catalyst-in-tube steam-raising duty discussed in the casestudy below.

Chc f ctltJM Catalysts currently offers fourmethanol synthesis catalysts;namely, Katalco 51-8, Katalco 51-8PPT and Katalco 51-9S and thepremium product Katalco Apico.Providing a range of catalysts, andnot relying on a single universal

product, caters for the differentmethanol synthesis technologiesand enables a choice of product forthe specic duty. This is particu-larly pertinent in a climate wherefeedstocks are changing. Naturalgas has been the principal feed forsynthesis gas generation (account-ing for ~80% of world methanolproduction); synthesis gas genera-tion historically has largely been

based on pure steam methane

reforming, whereas more recentlythere are circumstances whencombined reforming, whichincludes an oxygen-red secondaryor ATR, has its merits.

Coal gasication is anothermethod of syngas generation seeingrapid expansion in the number ofmedium- and large-scale methanolprojects in China based on a rela-tively cheap and plentiful resource,with many more plants likely toappear in the future. The US,

Australia, India and Russia alsohave abundant supplies of coal. Inrelation to the actual converter type,and without going in to too muchdetail, the different syngas-generating technologies yielddifferent syngas compositions (forinstance, CO content), each compo-sition yielding different reactionrates over the synthesis catalyst.Consideration of the exothermicsynthesis reactions means that some

converter designs are better suitedthan others to the differentsynthesis gases, by virtue of their


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51-8 at end of life. Figure 8 showsthe pressure drop has remainedstable with time, conrming thehigh strength retention and resist-ance to breakage in this duty.

BntSince ICI rst developed the LPMprocess, copper-based catalystshave improved in small incrementalsteps at regular intervals until now.The immediate benets to methanolplant operators are signicant: Increased production Lower by-product formation Faster start-ups using pre-reduced catalyst

Fewer catalyst change-outs.Simply stated, in existing plants,

Katalco Apico will make the mostmethanol, give the longest lifeand the fastest start-up possible.For a newly designed plant, it

offers the smallest reactor and thehighest achievable efciency. Thefollowing sections show compara-tive data for Katalco Apico and thecurrent industry standard Katalco51-9S.

Hght nd t tblctlt ctvtComparative activity tests andprojections clearly show the higher

activity of Katalco Apico catalyst(see Figure 10).

As a direct result of the higheractivity and stability with time on-line, the catalyst can be operatedfor twice as long as any comparablecommercial catalyst, leading tofewer catalyst change-outs. On a2500 tpd plant currently achievingfour years between change-outs, thetypical time saved by doubling thecatalyst life is about nine-and-a-halfdays, equivalent to at least 23 750tonnes of product methanol. This isderived from savings on oxidationof the previous catalyst charge priorto discharge, time to discharge andrell and then reduce the newcatalyst charge.

B-duct ftn

The results of tests shown in Figure11 conrm an even lower level ofhigher alcohol and other oxygenate

by-products with Katalco Apico attypical operating conditions. Thebenet is further enhanced by beingable to operate the catalyst at thelowest temperature possible due tostable activity.

On a 2500 tpd unit, using thecurrent generation of catalysts,98.5% of the crude methanol

coming from the synthesis loop isconverted to product methanol.With a 50% reduction in higheralcohol by-products, this gure isincreased to 99.15% an increaseof 0.65% in methanol produced.

Gt tngthFigure 12 shows the measured in-situ radial pellet strength comparedwith the best currently availableproduct.

The 50% increase in operating

strength ensures the catalyst isbetter able to withstand upsetconditions without physical break-age. This results in a more stablepressure drop so that efciency andgas distribution are maintained.

p-ducd ctltKatalco Apico catalysts aresupplied in the reduced form,which ensures the catalyst has beenactivated to achieve maximum unit

activity. Since there is no shrinkageassociated with normal catalystreduction, this also maximises the

Pre-reducedcatalyst

Highestactivity

Strongestproductavailable

slowestdeactivation

Leastby-products

Apico

Fgu 9 Sources of benets to operators


Katalco Apico

Katalco 51-9S

Fgu 10 Enhanced activity of Kataco Apico


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Fgu 12 In-situ radia peet strength of Kataco Apico

Ftu Bnt t t ext moH, tnnPre-reduced catayst Faster start-up 3000Higher, stabe activity Additiona MeOH made 55 000Doubed catayst ife Eiminated change-out 23 75050% ower by-products Increased efciency 45 000 Tota 126 750

otng bnt f ktlc ac

Tbl 1

amount of active copper charged.By using a pre-reduced catalyst,there is a typical saving of around30 hours for a new charge, repre-senting at least 3000 tonnes ofproduct methanol on a 2500 tpdplant.

ovll bntAs indicated in the previoussections, the enhanced performanceof Katalco Apico leads to benets inmany aspects of plant operation.These are summarised in Table 1.

The total value of these benets isover $25 million in additional meth-anol sales (assumed methanol price$200/t). Additional savings relatedto manning and material costs ofshutdown may also be realised.

C tud: ktlc pfncA methanol plant in Asia using acombination of Katalco catalysts inthe tubular reformer contracted JMCatalysts to do a specialist reformersurvey to check the performanceand make recommendations for anypossible optimisation. The furnacewas found to be in need of balanc-ing and it was also shown thatthe process gas temperature could

be safely increased without compro-

mising tube life. Detailedrecommendations on balancing thefurnace were implemented on theplant, with a resultant increase of60 tpd of methanol make worthover $3 million/y.

KATAlCOjM

and APICOjM

are marks of the

johnson Matthey Group of Companies.

T Fttc is Methano Technoogy

Manager within the GTl group of johnsonMatthey Cataysts. His work has a particuar

emphasis on the deveopment of technoogy

and catayst appications for methano

chemistry. He oined the catayst business

(then ICI) over 20 years ago and has a

bacheors degree in chemica engineering from

Cambridge University, UK.

T Hc is a consutant with johnson

Matthey Cataysts. He has worked on steam

reforming cataysts and technoogy, shift and

methano cataysts, acetyene hydrogenation

cataysts and ammonia synthesis technoogy

for ICI and now johnson Matthey, and has abacheors degree in chemistry from Durham

University, UK.


Fgu 11 Seectivity improvement with Kataco Apico

Documents

Advances in Methanol Synthesis