© Siemens AG 2013

Process Analytics

Production of Synthetic Rubber

Process Gas Chromatograph MAXUM edition II controls and optimizes
Butyl Rubber production

Rubber These days, process gas chromatographs are part of the

standard instrumentation of most production plants for
Rubber is a collective term for macromolecular substances
synthetic rubber. Their objective is to continuously
of natural (natural rubber, NR) or synthetic (synthetic
monitor and control processing variables such as
rubber, SR) origin. Natural rubber was already used by
composition of the process streams. Measuring results
the Mayas but was recognized as technical material first
are essential to plant efficiency and product quality.
in 1851 when Charles Nelson Goodyear presented a new
material produced from the milk of rubber trees, which Siemens Process Analytics is well known worldwide for its
has been treated with more or less amounts of sulfur and excellent process analyzer technique, application know
vulcanized. how, service competence and expertise in engineering
and manufacturing turnkey solutions including those for
Years later, a number of reasons including political events
synthetic rubber production.
were responsible for the development of alternatives for
natural rubber.
Synthetic Rubber
In 1920, the German Hermann Staudinger succeeded in
determining the structure of natural rubber which was the
key to the subsequent development of synthetic rubber in
many countries. In Germany, this was followed by a patent
for a synthetic rubber in 1929 and by the first large-scale
industrial production beginning in 1939. The respective
product was called Buna, from Butadiene as raw material
and Natrium (sodium) as catalyst.

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 © Siemens AG 2013

Synthetic Rubbers Refinery

Synthetic rubbers are complex chemical compounds built
by means of polymerization of monomers. Synthetic rub- Crude Oil
ber production (fig. 1) starts with the refining process of
oil, coal or other hydrocarbons with naphtha as one of the
resulting products. The naphtha is then combined with
Refining
natural gas to produce monomers. As feed material, typi-
cally monomers such as butadiene, styrene, isoprene,
chloroprene, acrylonitrile, ethylene or propylene are used.
Naphta Natural Gas
These are then treated by polymerization using catalyst
and process steam to form chains of polymers which
finally results in rubber substances.
These substances are then processed to rubber products
by vulcanization.
Rubber plant
Monomers
In integrated plants, naphta or even the monomers and
process steam are delivered as raw materials from other
production facilities which are located close to the rubber Additives Steam
plant.
The synthetic rubber industry provides a high number of
different synthetic rubbers which are produced in chemi- Synthetic
cal plants world wide to reflect the different applications rubber
and the wide range of requirements from the market.
Examples are
• Styrene-Butadiene Rubber (SBR), To end product
• Polybutadiene Rubber (BR) processing
• Polyisoprene Rubber (IR)
• Butyl Rubber (IIR)
Fig. 1: Generic production process of synthetic rubber
• Nitrile Rubber (NBR)
• Halobutyl Rubber (HIIR)
• Ethylene Propylene Diene Monomer (EPDM) As they are most widely used to produce tires, the SBR and
BR varieties are the most widely consumed type of syn-
and many more.
thetic rubber.
The use of rubber is widespread, as the characteristics and
According to “International Rubber Study Group”, world
properties of these elastomers make them useful in almost
production of synthetic rubber grew from 12.8 to 13.6 mil-
all economic sectors such as automobiles, civil construc-
lion tons in 2006-2007.
tion, footwear or plastics so that they are of crucial impor-
tance in the daily life of society. As massive investments were required to develop these
different varieties, the production technology was heavily
concentrated in long-established global major chemical
companies such as BASF, Lanxess (formerly Bayer), DOW,
Shell, Exxon, DuPont or major players in the tire industry
like Goodyear, Firestone or Michelin.
Leading world manufacturers are located in Asia and
Europe, followed by Northern America and Russia.

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Purge Recycle Methyl Catalyst Recycle Gas Compressor

Tower Tower Chloride Dissolver
Tower
Recycle to
Isobuth.
plant

Drying

Drying
Purge 4 3

Calalyst 2
chillers Steam / H2O
Isoprene

Feed
Purification

Isobutylene blend
Drying

drum
5
1
Feed chillers Reactor Flash drum Stripper
Steam / H2O Butyl rubber
slurry to finishing

Fig. 2: Butyl rubber process

Butyl Rubber (IIR) production • Polymerization and stripping unreacted monomers

(Section 2)
Butyl Rubber is a solution copolymer of Isobutylene
Butyl rubber is produced by co-polymerizing isobutylene
with some percent of Isoprene (Isobutylene Isoprene
with a small amount of isoprene, in a solution with
Rubber, IIR).
methylchloride and a chilled catalyst. To achieve high
Polyisobutylene by itself is fully saturated; therefore, molecular weight, the exothermic reaction must be
isoprene is added to provide sufficient double bonds to controlled at low temperatures close to -100 °C.
allow vulcanization with sulphur. A slurry of fine particles of butyl rubber dispersed in ethyl
chloride is formed in the reactor.
The outstanding property of IIR is the very low
The methyl chloride and unreacted monomers are
permeability to air and other gases why it is used for tire
flashed and stripped overhead in a sequence of distilla-
inner tubes. Other specialities include very good resis-
tion columns by addition of steam and hot water.
tance to sunlight, ozone and aging and, when used in
tires, reduced rolling resistance and thus reduced fuel • Recycle compression and purification (section 3 and 4)
consumption for “green mobility”. Solvent and isobutylene are recovered and dried and
recycled to the polymerization section, while impurities
Production process
are purged out.
• Feed blending (fig. 2, section 1)
• Finishing (section 5)
Butyl Rubber typically consists of about 98% Isobutylene
Slurry aid and antioxidant are introduced to the hot
with 2% Isoprene distributed randomly in the polymer
water/polymer slurry to stabilize the polymer and prevent
chain. The most commonly used polymerization process
agglomeration. Then the polymer is screened from the
uses methyl chloride as reaction diluent. Chillers are used
hot water slurry and dried in a series of extrusion dewa-
to cool the blended feed stream before it is fed to the
tering and drying steps. Fluid bed conveyors are used to
reactor.
cool the product to acceptable packaging temperature.

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Inputs of MAXUM edition II to process optimization Key analytical devices

General objective A key element in process gas chromatography is the injec-
tion to introduce the sample into the system and the switch-
In production plants to produce synthetic rubber material
ing of the separation columns to recondition the system by
process gas chromatographs play a dominant role to con-
backflushing remaining components or to cut components
trol various process sections. They provide key data about
out of the system.
the composition of the feed, intermediates or the final
products. This enables the control system to increase the For standard vapor applications (component concentrations
productivity, reliability and availability of the production in the percentage level) the model 50 valve (10-port mem-
plant, to cut maintenance costs and to minimize potential brane valve) combines sample injection and column switch-
risks. ing into one unit. This simplifies the analytical train and
reduces maintenance requirements significantly. Due to its
Top technology ensures optimal process control
design, using a teflon coated stainless steel diaphragm is
Siemens Plant Reliability Solutions aims to detect potential very robust and allows switching cycles up to 10 million on
plant faults early on and safeguard availability as well as clean samples without maintenance.
productivity. Process Gas Chromatography (PGC) has been
In synthetic rubber plants a significant amount of process
used for decades in the chemical industry.
samples which has to be extracted out of the process and
Typically, a PGC will be running for multiple component analyzed by the online gas chromatograph are in the liquid
analyses of various hydrocarbons (from low boiling point phase due to the used raw materials such as styrene (SBR
up to high boiling fractions) but also inert gases such plants) or liquefied isobutylene (IIR or Nd-PBR plants).
as hydrogen. MAXUM edition II represents the top Therefore, the sample has to be vaporized before it can be
technology in process gas chromatography for analyzing analyzed. This indicates that the injection technology of
liquids and vapor process samples. Unparalleled product the analyzer gains in importance to guarantee that the
features deliver high versatility and the best possible measurement is accurate and the results are representa-
analytical results at the lowest cost. These are: tive for the actual process stage.
• Multiple analytical tools such as injectors, ovens, detec- Fig. 3 shows an automated injection module to introduce
tors or columns to adapt the hardware perfectly to the the liquid into the separately heated vaporization chamber
analytical needs and convert to the gas phase inside the analyzer. The
• Liquid injection modules to optimize the evaporation of module equipment is flexible in terms of injection volume,
liquid samples sealing, sample split ratio after vaporization or even the
• Broad range of column types and columns switching material of sample wetted parts. This guarantees best
technologies available to provide perfect customized adjustment according to the requirements of the sample
solutions for a reliable and accurate analysis.
• Sensitive detectors to determine trace components
C4/C5 hydrocarbon analysis using Analytical Setups
• Single and independent dual oven concept for
minimizing the number of analyzers In the core process of synthetic rubber production,
• Airless oven to reduce utility costs monomers are mixed in various proportions to be copoly-
merized to achieve products with a range of physical,
chemical and mechanical properties. The module equip-
ment is flexible in terms of injection volume, sealing, sam-
ple split ratio after vaporization or even the material of
sample wetted parts. This guarantees best adjustment
according to the requirements of the sample for a reliable
and accurate analysis. These monomers such as
1.3 butadiene (SBR plants), isobutylene and isoprene
(IIR plants) are hydrocarbons C4/C5.

Fig. 3: Key analytical devices for snythetic rubber applications

Left: model 50 injection & backflush valve,
Center: double oven with model 50 configuration (left) and valveless configuration (right),
Right: liquid injection valve

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Setup A Liquid injection, isothermal oven (airbath, airless opt.) (micro)packed columns, TCD Criteria:
Liquid
Sample
Components in %-level
Carrier Simple separation
Mod
Gas LIV TCD
50 Application example:
Styrene analysis (SBR plant)
Pre-separation Column Iso-Butylene analysis
Liquid injection Backflush switching Separation Detection (IIR plant)

Setup B Liquid injection, isothermal oven (airbath, airless optional), capillary columns, FID Criteria:
Liquid
Sample Trace analysis (ppm level);
Challenging separation
Carrier
Gas LIV Live FID Application example:
Selected C4 isomeres (ppm)
Pre-separation Column Other hydrocarbons
Liquid injection Backflush switching Separation Detection

Setup C Liquid injection, isothermal oven (airbath, airless opt.), (micro)packed columns, TCD
Criteria:
Liquid
Sample Components in %-level
Comp. need to be removed
Carrier from system to optimize
Mod Mod
Gas LIV 50 50 TCD separation

Application example:
Pre-sep. Column Pre-sep. Column Separation Detection
Various C4 isomeres
Liquid injection Backflush switching Cut switching

Setup D Gas injection, isothermal oven (airbath, airless optional), packed columns, TCD
Criteria:
Vapor
Sample Components in ppm level
(trace analysis)
Carrier Analysis of target components
Mod
Gas
50 FID Application example:
Pre- Ambient air monitoring of
Vapour Injection + separation butadiene-1.3
Backflush Separation Detection
Column Switching

Fig. 4: Analytical Setups (configurations) of MAXUM II

To date, gas chromatography based analyzers are most

widely used for the determination of these constituents
due to its high specificity. The analysis of individual
C4/C5 species requires GC columns which are specialized
in the separation of various C4-isomers (fig. 5). Typically
GC columns are used with different selectivity to increase
the overall separation power of the method. The columns
are coupled together with a switching device that trans-
fers a unseparated portion of the chromatogram eluting
from the first column to the second, where complete
separation can be realized. Most frequently used analyti-
cal configurations (Setups) are shown in fig. 4.
Combinations of the configurations allow also densifica- Fig. 5: Separation of C4 isomers
tion options to integrate applications into one analyzers
instead of using two.

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 © Siemens AG 2013

Measuring tasks MAXUM edition II benefits for plant optimization

Details of measuring tasks, sampling locations and con- MAXUM edition II process gas chromatograph provides a
centration values of the components differ from plant to number of extensive benefits for plant optimization:
plant according to process type and specific plant design.
• Offering an outstanding broad variety of analyti-
But the measuring components themselves will be very
cal possibilities and a consequent modular design,
similar in all cases. Fig. 7 shows a typical list with
MAXUM edition II can always be configured according
reference to the flow chart of fig. 2.
to the actual analytical needs and thus provide best
Most of the components are determined by gas chroma- possible results.
tography, but continuous gas analyzers are also used in
• The new software portal provides real-time information
applications like combustion optimization and exhaust gas
from all chromatographs and allows continuous control
emission control at different locations of the plant.
and immediate reaction to any changing situation.
• MAXUM edition II features variable networking possi-
bilities including Modbus/TCP and Ethernet. This allows
easy integration into plant automation systems.
• Due to its well-proven and multiple tested design and
the integrated diagnosis functions, MAXUM edition II
offers an outstanding availability which is of highest
importance in process plant control.
A large and well experienced team stands behind any
application and installation to provide any kind of user
support, if requested. This ranges from broad application
know how to efficient world wide service capabilities.

Fig. 6: MAXUM - Color Touch Screen Maintenance Panel

Section Product stream / Measuring task Component Section Product stream / Mesuring task Component

n-Butylene Combustion gas (1) CO

Isobutene-Isoprene fraction to basic charge Isobutylene Combustion optimization NO
Correct feed composition control Amylene Emission monitoring O2
Isoprene CO
1 n-Butylene Combustion gas (2)
CH4
Combustion optimization
Isobutylene NO
Charge Emission monitoring
Amylene O2
Correct feed composition control
Isoprene Isobutane
Methylchloride Isobutene
Isobutylene n-Butane
Mixed isobutene fraction 1.3-Butadiene
Methylchloride
Polymerization and Degassing
2 Correct polymerization process control
Isoprene ™Butylene
N-Butylene C5 - C9 hydrocarbon
Isobutene
Amylene C1 - C3 hydrocarbon
dehydro-
Hydrogen
genation
Oxygene Methane
Methylchloride C2 hydrocarbon
Returnable products processing (1) Isobutylene C3 hydrocarbon
Correct recycle steps control Isoprene Isobutane
n-Butylene Isobutene
Amylene n-butane
Isobutylene Contact gas ™Buthylene
3/4 Isoprene 1.3-Butadiene
Returnable products processing (2)
Methylchloride C5 - C9 hydrocarbon
Cirrect recycle steps control
n-Butylene Carbon Monoxide
Amylene Carbon dioxide
Returnable products distilling (1) Methylchloride Nitrogen
Correct recycle steps control Isobutylene Water
Returnable products distilling (2) Nitrogene
Correct recycle steps control Methylchloride

Fig. 7: Measuring tasks and measuring components

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 © Siemens AG 2013

Siemens Gas Chromatographs – Innovations Whether you are a new analyzer technician or a
GC veteran, the new display of the MAXUM is the ideal
Gas Chromatograph Portal Workstation Software
user interface. All the routine gas chromatograph opera-
The MAXUM (and MicroSAM) process gas chromatograph tion and maintenance functions are accessible with a sim-
product line is supported by the Gas Chromatograph ple touch of the 10-inch color display. Further simplifying
Portal workstation software to more easily monitor and access to the MAXUM GC, the touch screen display is fully
modify MAXUM (and MicroSAM) GCs on an Ethernet certified for direct use in hazardous Div. I and Zone 1
network. areas.
The new software upgrades the former System Manager Thanks to the MAXUM GC’s open design structure, it is
and EZ-Chrom software packages which now have been easy to add this color maintenance panel to existing
completely integrated and refined into a new single soft- MAXUM GCs by simply exchanging the door of the GC’s
ware package. The new software is fully compatible with electronics section. This is part of Siemens Process
existing MAXUM and MicroSAM GCs in the field. Analytics’ commitment to enhancing the product while
protecting our customer’s investment in their MAXUM GC
The Gas Chromatograph Portal software resides on a
system.
PC workstation (fig. 8) and gives the user the real-time
status for all the gas chromatographs on the network. Modular Oven
In the event of an alarm, interrogating the analyzer is as
An addition to the regular oven variants (airless, airbath
simple as clicking on the icon for the analyzer, automati-
and temperature programmable oven) another option is
cally calling up intuitive screens with all the analyzer’s key
available using the Modular Oven. This oven option is an
performance parameters displayed.
airless oven design where complete chromatograph
With the Gas Chromatograph Portal, every GC on the net- modules are snapped into place. Removal and replace-
work is continually updated to reflect the current analysis ment of a module can be performed in mere minutes,
and operating status. Analysis results, chromatograms and dramatically lowering operation and maintenance of the
alarm logs are just a simple click away. Furthermore, auto- gas chromatograph. The module can then be repaired at
matic data logging and reporting functions are completely the user’s convenience in their maintenance shop or
supported and each display takes full advantage of the returned for refurbishment at Siemens. And, as part of the
latest user interface features. MAXUM GC analysis platform, the modular configuration
is completely compatible with any MAXUM system for
data communication and reporting.
This oven option is part of Siemens Process Analytics’
commitment to the MAXUM GC platform as the ideal solu-
tion for process analysis for years to come.

Fig. 8: Gas Chromatograph Portal Workstation

Color Touch Screen Maintenance Panel

The newest addition to the MAXUM gas chromatograph
(GC) features is now a large color touch screen mainte-
nance display that blends the best features of the previous
menu-driven design with icons and graphical elements for
simple access to all the standard maintenance features of
the MAXUM. Fig. 9: MAXUM Modular oven with color touch screen

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 © Siemens AG 2013

Siemens Process Analytics at a glance Plant life-cycle support

Leading in process analytics As a result of our large service portfolio we are able to
support our customers throughout the complete product
Siemens is a leading provider of process chromatographs,
life cycle (fig. 10). We already develop cost-efficient and
process analyzers and process analysis systems and solu-
reliable analytical concepts during plant planning. Using
tions. We offer our global customers the best solutions for
customized service contracts and competent service onsite
their applications based on innovative analysis technolo-
we can help to reduce downtimes while simultaneously
gies, customized system engineering, sound knowledge
ensuring optimum operation of the analytical equipment.
of customer applications and professional support. From
Our range of services is extended with technical support
applications in the chemical and petrochemical industry
from experts over the hotline and a comprehensive selec-
to emission monitoring in waste incinerators and power
tion of on-site training courses for service personnel and
plants, the highly accurate and reliable Siemens analyzers
operators.
and chromatographs will always do a perfect job.
The chromatographs and analyzers are easily integrated
into the Totally Integrated Automation (TIA) concept Plant life cycle
making Siemens Process Analytics your qualified partner
for efficient solutions that integrate process analyzers into Planning & Engineering & Installation & Operation &
Modernization
design development commissioning maintenance
automation systems.
Online Support
Global presence
FEED for Process Analytics
The global presence of the Siemens service organization
Engineering
permits optimum support for our customers through fast
Installation and commissioning
response times onsite. Furthermore, our service specialists
are acquainted with the local and regional requirements, Repairs and spare parts

standards and directives. We can offer our customers tai- Field service / Service contracts
lored service products based on our specific knowledge of Optimization and modernization
the processes involved in the oil & gas, chemical, power,
Technical Support / Training
cement and other industries.
Fig. 10: Siemens Process Analytics: Plant life cycle services

The information provided in this Case Study

contains descriptions or characteristics of perfor-
mance which in case of actual use do not always
apply as described or which may change as a result
of further development of the products. An obliga-
tion to provide the respective features shall only
exist if expressly agreed in the terms of contract.
Siemens AG Availability and technical specifications are subject
Industry Sector to change without prior notice.
Sensors and Communication All product designations may be trademarks or
Process Analytics product names of Siemens AG or supplier
76181 KARLSRUHE Subject to change without prior notice companies whose use by third parties for their own
GERMANY © 01/2013, Siemens AG purposes could violate the rights of the owners.