Journal of Natural Gas Chemistry 13(2004)71–78

Methane — the Promising Career of a Humble Molecule

Serge Kioes, Waldemar Liebner∗

mg engineering-Lurgi AG, Lurgiallee 5, D-60295 Frankfurt am Main, Germany

[Manuscript received May 12, 2004]

Abstract: Methane, CH4, here represents natural gas (NG) of which it is the main constituent. Routes ofchemical utilisation of NG — as opposed to energy usage — are discussed. A main step is the conversion ofNG to synthesis gas, a mixture of CO and H2. Simple molecules derived from synthesis gas, like methanol,can be further reacted to longer-chained hydrocarbons like propylene and other olefins and even to gasolineand diesel.

Key words: CH4, natural gas conversion, methanol, propylene, MTP, MtSynfuels

1. Methane and more

Talking about natural gas and natural gas conver-

sion, we essentially consider methane, the main com-

ponent of all natural gases. This now as the simplest

hydrocarbon indeed is a “humble” molecule: CH4,

one carbon atom and four hydrogen atoms. Chemi-

cally speaking this molecule is rather inert. It does not

readily react, even with air as in combustion, where

its ignition temperature is high.

This unwillingness to undergo transformations is

one of the hurdles on its way to “higher ranks” of

chemicals like longer chain hydrocarbons. All routes

of direct coupling (direct oxidation) as ingeniously de-

scribed and developed so far have not surpassed the

experimental stage and shall be left aside here with

this honourable mention.

Instead we shall concentrate on the technically

feasible — or better even, the technically successful.

For all its stubborn inertia our humble molecule can

be induced, if not to say forced, to change shape and

appearance if we offer the right partners and condi-

tions. These may be steam and oxygen as in “Steam

Methane Reforming” or “Autothermal Reforming”.

By these the CH4 changes into CO and H2, i.e. a

mixture of carbon monoxide and hydrogen which is

called synthesis gas — or “syngas” for short.

With syngas now starts the veritable career of

our molecule: by a tendency to re-shape it becomes

H3COH, also known as methanol. From this it trans-

forms to H3COCH3, dimethyl-ether and then further

to longer chain hydrocarbons, the formerly elusive

goal. We will see products like the valuable propy-

lene and also transportation fuels like gasoline and

diesel: an impressive career indeed for the small, hum-

ble CH4!

Fully acknowledging that many companies, in-

stitutions and individuals are active in the field of

“methane transformation” or, as the title of this con-

ference states in “natural gas conversion”, the presen-

ter today will concentrate on what he knows best, his

companies portfolio.

What first comes to mind with natural gas con-

version is GTL, mostly meant to be Fischer-Tropsch,

the classic route from coal or natural gas to trans-

portation fuels (synfuels). Lurgi on the other hand

promotes methanol-based technologies for upgrading

of natural gas to value-added products. These pri-

marily would be DME (dimethyl ether), propylene,

synfuels and “gas-based petrochemicals”.

∗ Corresponding author. E-mail: dr−waldemar−liebner@lurgi.de

72 Serge Kioes et al./ Journal of Natural Gas Chemistry Vol. 13 No. 2 2004

Figure 1. Flared natural gas (2002)[1]

Since Lurgi introduced its new groundbreaking

MegaMethanol©R process for plants with a production

of 5,000 tons of methanol per day and more, methanol

will be available at a constant low price in the foresee-

able future. This development has an enormous im-

pact on downstream technologies for the conversion

of methanol to more valuable products.

The first derivative of methanol in this context

is DME which has a high potential as alternative to

conventional diesel fuel as feedgas for gas turbines in

power generation and as supplement to LPG. The

next step is the use of methanol as feedstock for

the production of olefins which is one of the most

promising new applications. Lurgi’s new Methanol-

to-Propylene (MTP©R) process presents a simple, cost-

effective and highly selective technology. Both routes

allow for the production of petrochemicals which then

would be gas-based. Lurgi also proposes a methanol-

based technology for production of synfuels which

compares well with the FT-processes.

2. Natural gas conversion—a solution for the

21st century

The total proven gas reserves amount to approx.

180 trillion cubic meters world-wide which translates

into a gas reserve-to-production ratio, i.e. a gas re-

serve lifetime of 70 years. Furthermore, estimated ad-

ditional gas reserves will cover a lifetime of 65 years

more [1]. Compared with the reserve lifetime of 41

years for petroleum and 230 years for coal, there is no

doubt that natural gas will be a key fuel component

in the 21st century.However, currently a considerable portion of this

reserve is wasted yearly: a brief look at Figure 1

“Flared Natural Gas” explains the main incentive for

engineers and environmentalists as well to come up

with novel ideas for the utilisation of this gas.

Existing technologies for natural gas conversion

are shown in Figure 2: via the conversion to syn-

gas, hydrogen and ammonia, Fischer-Tropsch prod-

ucts, methanol and DME are produced. Currently,

the production of chemicals requires only around 5%

of world gas consumption [2].

Figure 2. Uses of natural gas

Both, economic and environmental benefits from

the use of natural gas are driving and supporting the

continuous innovation of gas-based technologies.

Lurgi AG focuses on new routes from C1 to valu-

able products by combining a chain of proprietary

Lurgi technologies that are based on low cost natu-

ral gas supply and large scale methanol plants. These

are new DME and synfuels technologies and an excit-

ing new process for the highly selective conversion of

methanol to propylene. Certainly, there is healthy

competition already in these new fields: just to

name “single-step” DME synthesis and “Methanol to

Olefins”, MTO, which produces ethylene and propy-

lene together.

3. Lurgi MegaMethanol©R: basis for more valu-

able products

The term MegaMethanol©R refers to plants with

Journal of Natural Gas Chemistry Vol. 13 No. 2 2004 73

a capacity of more than one million metric tons per

year, the actual “standard” size being 1.7×106 t/a

(equivalent to 5000 t/d). To achieve such a large

capacity in a single-train plant a special process de-

sign is required. For this reason Lurgi focused on

the most efficient integration of syngas generation

and methanol synthesis into the most economical and

reliable technology for the new generation of future

methanol plants [3].

The unique advantages of the Lurgi

MegaMethanol©R technology result in “ex-gate”

methanol prices of about 65�/t or less and make

this process ideally suited as part of Lurgi’s route

from C1 to propylene and others. This year two such

plants of 5000 t/d capacity will be started up: At-

las/Trinidad in summer and Zagros/Iran by year’s

end. Conceptual studies and engineering activities

for MegaMethanol©R plants with single-train capaci-

ties of up to 7500 t/d and more have been successfully

finalised making these plant sizes ready for commer-

cialisation.

An environmental sidenote: 80 billion cubic me-

ters of natural gas are flared or vented annually, see

Figure 1 [1]. That amount would be sufficient to feed

about 60 MegaMethanol©R plants with a capacity of

102 million tons per year in total.

4. DME—a valuable product from methanol

Dimethyl Ether, DME, is industrially important

as the starting material in the production of the

methylating agent dimethyl sulphate and is used in-

creasingly as an aerosol propellant. In the future

DME can be an alternative to conventional diesel fuel

or a feedgas for power generation in gas turbines.

Both applications are based on large-scale production

facilities in order to achieve an economic fuel price.

Traditionally, DME was obtained as by-product of

the high-pressure methanol synthesis. Since the low-

pressure methanol synthesis was established, DME

has been prepared from methanol by dehydration in

the presence of suitable catalysts. The dehydration

is carried out in a fixed-bed reactor. The product is

cooled and distilled to yield pure DME.

A modification of the methanol synthesis would

allow for co-generation of DME within the methanol

synthesis loop. This technical path comprises two dis-

advantages. While dehydrating methanol, the water

vapour content increases, thus enhancing the water

gas shift reaction. By converting CO into CO2, the

quality of the synthesis gas deteriorates. The kinet-

ics of the reaction of CO2 and H2 is slower than the

one of CO and H2. As a result, the synthesis cata-

lyst volume and the recycle loop capacity have to be

increased. In addition, due to its low boiling point a

cryogenic separation is required in order to separate

DME from the synthesis recycle loop.

As a result of these disadvantages of the co-

generation of methanol and DME Lurgi favours the

concept of generating DME from methanol by dehy-

dration.

If a DME unit is added to the MegaMethanol©R

plant, the distillation of methanol is reduced from

a three-tower system to one tower at considerable

savings. Figure 3 shows the simple and inexpensive

flowsheet for the dehydration of methanol. In this

process all types and qualities of DME can be pro-

duced. The different specifications for fuel gas, power

generation or pure DME can be achieved just by vary-

ing size and design of the DME distillation towers.

Figure 3. DME production by methanol dehydration

Without going into the details of the economic

analysis which has been presented elsewhere it can

be summarised that DME can be produced at a ca-

pacity of 5000 t/d from natural gas priced at US�

0.5/MMBtu with a reasonable profit of 20%ROI at

93 US�/t. Delivered cost of DME after “trans-ocean”

transport from the production site, the stranded gas

location, will be about 4 US�/MMBtu.

From all this it follows that DME, a traditional

derivative of methanol, can be a promising alternative

fuel for power generation, diesel, LPG or the manu-

facture of olefins when produced in large capacities.

These uses of DME are promoted by a group of tech-

nology providers and contractors together with inter-

ested institutions in the International Dimethyl-Ether

Association, IDA, and its Japanese Equivalent, JDA.

See the website www.aboutdme.org.

5. Propylene—an attractive product with high

value

Demand growth of propylene till 2002 was above

74 Serge Kioes et al./ Journal of Natural Gas Chemistry Vol. 13 No. 2 2004

8% and after that is projected at higher than 5%.

Polypropylene is by far the largest and fastest grow-

ing of the propylene derivatives, and requires the ma-

jor fraction of about 60% of the total propylene. The

increasing substitution of other basic materials such

as paper, steel and wood by PP will induce a further

growth in the demand for PP and hence propylene.

Other important propylene derivatives are acryloni-

trile, oxo-alcohols, propylene oxide and cumene. The

average growth rate for propylene itself is estimated

very conservatively to be 4.5% per year for the next

two decades.

How to satisfy this demand for propylene?

Currently, steam crackers and FCC units supply

66% and 32%, respectively of propylene fed to petro-

chemical processes. However, as FCC units primarily

produce motor gasoline, and steam crackers mainly

ethylene, propylene will always remain a by-product

(e.g. 0.04–0.06 t/t of ethylene for steam crackers

with ethane feedstock and 0.03–0.06 t/t, respectively

of motor gasoline and distillates production for FCC

units). Current forecasts indicate an increasing gap

of propylene production that has to be filled by other

sources. Lurgi’s new MTP process directly aims to

fill that gap.

6. Lurgi’s methanol to propylene (MTP©R)

technology

Lurgi’s new MTP©R process is based on an efficient

combination of the most suitable reactor system and a

very selective and stable zeolite-based catalyst. Since

the process has been described in detail elsewhere [4],

suffice it to say here that Lurgi has selected a fixed-

bed reactor system because of its many advantages

over a fluidised-bed. The main points are the ease of

scale-up of the fixed-bed reactor and the significantly

lower investment cost.

Furthermore, Sud-Chemie AG manufactures a

very selective fixed-bed catalyst commercially which

provides maximum propylene selectivity, has a low

coking tendency, a very low propane yield and also

limited by-product formation. This in turn leads to

a simplified purification scheme that requires only a

reduced cold box system as compared to on-spec ethy-

lene/propylene separation.

With Figure 4 a brief process description reads:

methanol feed from the MegaMethanol©R plant is sent

to an adiabatic DME pre-reactor where methanol is

converted to DME and water. The high-activity,

high-selectivity catalyst used nearly achieves ther-

modynamic equilibrium. The methanol/water/DME

stream is routed to the first MTP©R reactor where also

the steam is added. Methanol/DME are converted

by more than 99%, with propylene as the predomi-

nant hydrocarbon product. Additional reaction pro-

ceeds in the second and third MTP reactors. Process

conditions in the three MTP©R reactors are chosen to

guarantee similar reaction conditions and maximum

overall propylene yield. The product mixture is then

cooled and the product gas, organic liquid and water

are separated.

Figure 4. MTP©R: simplif ied process f low diagram with production figures

The product gas is compressed and traces of wa-

ter, CO2 and DME are removed by standard tech-

niques. The cleaned gas is then further processed

yielding chemical-grade propylene with a typical pu-

rity of more then 97%. Several olefin-containing

streams are sent back to the main synthesis loop as

an additional propylene source. To avoid accumula-

tion of inert materials in the loop, a small purge is

Journal of Natural Gas Chemistry Vol. 13 No. 2 2004 75

required for light-ends and the C4/C5 cut. Gasoline

is produced as a by-product.Water is recycled to steam generation for the pro-

cess; the excess water resulting from the methanol

conversion is purged. This process water can be used

for irrigation after appropriate and inexpensive treat-

ment. It even can be processed to potable water where

needed.

An overall mass balance is included in Figure 4

based on a combined MegaMethanol©R / MTP©R plant.

For a feed rate of 5000 tons of methanol per day (1.667

million tons annually), approx. 519000 tons of propy-

lene are produced per year. By-products include fuel

gas (used internally) and LPG as well as liquid gaso-

line and process water.

Further integration and optimization of the total

plant complex including syngas, methanol, propylene

production and offsite facilities will again decrease the

capital investment and production costs.

The technological status of MTP©R in the areas

of process and catalyst can be summarized as follows:

The basic process design data were derived from more

than 9000 operating hours of a pilot plant at Lurgi’s

Research and Development Centre. Besides the opti-

mization of reaction conditions also several simulated

recycles have been analysed. Parallel to that Lurgi

decided to build a larger-scale demonstration unit to

test the new process in the framework of a world-scale

methanol plant with continuous 24/7 operation using

real methanol feedstock. After a cooperation agree-

ment with Statoil ASA was signed in January 2001

the Demo Unit was assembled in Germany and then

transported to the Statoil methanol plant at Tjeldber-

godden (Norway) in November 2001. Later in 2002

Borealis joined the cooperation.

The Demo Unit was started up in January 2002,

and the plant has been operated almost continuously

since then. As of March 2004, the Demo Unit com-

pleted the scheduled 8000 hours life-cycle test and an

additional 3000 hours with a new batch for counter-

checks. With that the main purpose of the test was

achieved: to demonstrate that the catalyst lifetime

meets the commercial target of 8000 hours on stream.

Cycle lengths between regenerations have been longer

than expected. Deactivation rates of the methanol

conversion reaction decreased with operation time.

Propylene selectivity and yields were in the expected

range for this unit with only a partial recycle. Also,

the high quality of the by-product gasoline and the

polymerisation grade quality of the propylene were

proven [5]. The catalyst development is completed and

the supplier commercially manufactures the catalyst.

7. GTP economics

Since propylene by itself is more an intermediate

than an end product, an economics estimate was per-

formed for a complete natural gas to polypropylene

complex. In this case of integrating a MegaMethanol©R

and a MTP©R plant we designate the resulting unit as

“Gas to Propylene”, GTP©R, as shown in Figure 5.

Figure 5. Block flow diagram-PP complex

Thus, the economic assessment included the GTP

route with a polypropylene unit for the production of

a more saleable, higher-value end product.

To summarise the extensive economic study pre-

sented elsewhere, it can be said that again based on

natural gas priced at US�

0.5/MMBtu, competitively

priced polypropylene with the side-product gasoline

can be produced at ROIs of 19% to 23% or, stated

differently, with IRRs before tax of 21% to 26%.

8. Fischer-Tropsch, FT, an “old” natural gas

conversion process

FT “simply” condenses the syngas derived from

the humble molecule CH4 into longer chains (-CH2-)n,

i.e. hydrocarbons like gasoline (medium long chains),

diesel (long chains) and waxes (very long chains).

Historically, Lurgi was one of the developers of

FT in the 1920–30ties. FT in the form of (fixed bed)

ARGE-synthesis was commercialised in 1952 in Sasol-

burg, RSA. All five original reactors are still in oper-

ation. A sixth one was started in 1987 as capacity ex-

tension. Modern FT reactor technology prefers slurry

phase reactors, either tubular or fluidised bed. Lurgi

has commercial experience in all these reactor de-

signs. Also, Lurgi has designed all syngas production

units of all currently operating industrial FT-plants:

Sasol/Secunda, RSA, utilising coal gasification; Moss-

gas, RSA, -combined reforming of NG and SMDS Bin-

tulu, Malaysia-partial oxidation of NG.

The syngas production route which among oth-

ers is used for MegaMethanol©R is offered by Lurgi as

MegaSyn©R and is available for FT syntheses also.

76 Serge Kioes et al./ Journal of Natural Gas Chemistry Vol. 13 No. 2 2004

9. A new route to transportation fuels:

MtSynfuels©R

Given the economically highly attractive tech-

nologies of MegaMethanol©R and MTP©R as described

above it nearly follows by itself to combine them with

an industrially proven process for the conversion of

olefins to diesel. A gas-based synfuels plant using

this process, then named COD (derived from Conver-

sion of low molecular weight Olefins to Diesel), was

developed and built by Lurgi for Mossgas (today: Pet-

roSA), RSA, in 1992 and is performing well since its

start-up in 1993.

Remarkably, the industrial design was based on

a scale-up factor of 3600 over the preceding demon-

stration plant. This basically was possible through

the use of fixed-bed catalysis (on zeolite basis) which

lends itself to easy scale-up. Other important pro-

cess features are semi-continuous operation and a 98%

conversion of C3- and C4- olefins.

The Lurgi route to synfuels, MtSynfuels©R shown

in Figure 6 is a combination of this type of process

with MegaMethanol©R and a simplified MTP©R. Exten-

sive engineering and estimating studies have been per-

formed to prove the feasibility and economic viability

of this new route. All studies show that MtSynfuels©R

compares well with FT processes. Investment costs

are lower and efficiencies are better than for FT.

MtSynfuels©R produces on-spec gasoline and diesel at

about 23 US�/bbl which makes this route attractive

at crude oil prices of 21 US�/bbl already [6].

Figure 6. Gas refinery via methanol—lurgi’s MtSynfuels©R

Admittedly MtSynfuels©R lacks full commerciali-

sation, but so do most of the other FT processes dis-

cussed currently. In contrast to these, MtSynfuels©R

is proven in three of four steps with the demo unit

for the third step (MTP©R) having confirmed the lab

results by a 11000 hours test run.

10. From gas to petrochemicals—the real ca-

reer of the humble molecule

It has been shown above that propylene produced

via MTP©R competes well with cracker-derived prod-

uct. In more general terms it develops that the chain

of Lurgi’s technologies described here provides an al-

ternative route to petrochemicals. Almost all steps

are technically proven and the economic competitive-

ness mainly depends on the natural gas price. This

again follows from market pressures and the need or

willingness to monetise gas reserves. Accidentally, the

technology chain described here also represents the

“career of the humble molecule”: methane becomes a

supplemental basis of the broad field of petrochem-

istry.

Figure 7 shows how the conventional cracker route

from crude oil through olefinic and aromatic inter-

mediates to highly valued petrochemical products is

complemented -and replaced possibly- by “gas-to-

methanol-and-others” processes. There is even the

possibility to use coal (or biomass!) as the primary

feedstock for this methanol-to-petrochemicals route,

an alternative seriously considered here in China

which lacks large oil or gas reserves but has an abun-

dance of coal.

11. Conclusions

There are abundant natural gas reserves provid-

ing low cost feedstock for methanol production and

aiming at better use of natural resources especially in

the case of associated gases being flared. DME and

propylene produced from methanol will increase the

value of natural gas considerably and offer an exciting

potential of growth and a high earnings level.

Journal of Natural Gas Chemistry Vol. 13 No. 2 2004 77

Figure 7. Gas-based petrochemistry

Lurgi’s MegaMethanol©R technology brings down

the net methanol production cost below US�

50 per

ton, wherever low cost natural gas is available. This

opens up a completely new field for downstream prod-

ucts like DME, propylene and synfuels. Based on sim-

ple fixed-bed reactor systems, conventional process-

ing elements and operating conditions including com-

mercially manufactured catalysts, Lurgi’s MegaDME,

MTP©R and MtSynfuels©R technologies provide attrac-

tive ways to “monetise” natural gas. Alert compe-

tition offers alternatives in several cases. Here, the

markets will have the last say.

Driven by the excellent market prospects and ad-

ditional environmental aspects, Lurgi has developed

its own technology chains starting from natural gas

via methanol to DME or propylene and polypropy-

lene, based on the combination of highly efficient

concepts at low investment costs. In the next step

these concepts lead to gas-based refineries and gas-

based petrochemicals. Figure 8 summarises the gas to

chemicals routes. With the exception of FT and MTO

which are offered as licensed technologies, all others

depicted here are Lurgi proprietary technologies—a

direct result of the high importance Lurgi always at-

tached to gas and syngas conversion. MtPower de-

picts the utilisation of methanol and DME as energy

carriers, made possible by the low production costs

associated with the “Mega-plants”.

Figure 8. Gas to chemicals processing routes

The many routes our humble molecule CH4 can wander, making a career of its own

78 Serge Kioes et al./ Journal of Natural Gas Chemistry Vol. 13 No. 2 2004

Eventually, financial, strategic and political in-

terests will determine the ultimate selection of any

“gas-to-value” technology. The task of the engineer-

ing company is to provide as many attractive alterna-

tives as possible to accommodate for all sorts of local

conditions. With the technology portfolio described

above Lurgi is up to this challenge.

References

[1] Cedigaz. “The 2002 Natural Gas Year in Review”,

April 2003, www.cedigaz.com

[2] Quigley Th M, Fleisch Th H. “Technologies for the

Gas Economy”, EFI—Gas to Market Conference, San

Francisco, October 11–13, 2000

[3] Streb S, Gohna H. “MegaMethanol©R—paving the way

for new down-stream industries”, World Methanol

Conference, Copenhagen (Denmark), November 8–10,

2000

[4] Rothaemel M, Holtmann H-D. “MTP, Methanol To

Propylene—Lurgi’s Way”, DGMK-Conference “Cre-

ating Value from Light Olefins–Production and Con-

version”, Hamburg, October 10–12, 2001

[5] Koempel H, Liebner W. “Gas to Liquids? Gas To

Chemicals? Gas to Value!”, ERTC Petrochemical

Conference, Amsterdam, February 20–22, 2002

[6] Rothaemel M, Koempel H, Liebner W. “Progress Re-

port on MTP with focus on DME”, AIChE Spring

National Annual Meeting, New Orleans, April 25–29,

2004, Session: Olefins Production