Fischer-Tropsch Refining (DE KLERK:FISCHER-TROPSCH O-BK) || German Fischer-Tropsch Facilities

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Part IIIIndustrial Fischer–Tropsch Facilities

Fischer–Tropsch Refining, First Edition. Arno de Klerk. 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2011 by Wiley-VCH Verlag GmbH & Co. KGaA.

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6German Fischer–Tropsch Facilities

6.1Introduction

Construction of the first industrial-scale Fischer–Tropsch facility by Ruhrchemie AG,started in 1935 in Germany [1]. It was soon thereafter followed by the construction of moreFischer–Tropsch-based facilities, which can broadly be grouped into two categories based on theoperating pressure of the Fischer–Tropsch synthesis section. The first industrial installations op-erated at below 0.1 MPa using the ‘‘normal-pressure synthesis’’ (Ger. ‘‘Normaldruck-Synthese’’)or atmospheric process. Later on, a ‘‘medium-pressure synthesis’’ (Ger. ‘‘Mitteldruck-Synthese’’)process was employed, which operated at 0.5–1.5 MPa (75–220 psi). The operating temperatureof synthesis was usually in the range 180–200 ◦C [2], making these both low-temperatureFischer–Tropsch (LTFT) processes.

The German Fischer–Tropsch facilities all employed coal as the raw material and a totalof nine plants were constructed in Germany (Table 6.1) [1, 3, 4]. A further five plants wereconstructed under license outside Germany, one in France, three in Japan, and one in China. Atthe beginning of 1944, the coal-to-liquids industry provided close to two-thirds of the Germanfuel and oil consumption, with Fischer–Tropsch synthesis producing 7%, coal hydrogenation40%, benzene 5%, and coal tar distillation 12% [1].

Many of the plants were damaged by the Allied bombing offensive during the latter half of1944 and early 1945. After the Second World War, only Brabag, Essener, and Krupp started upagain and the last of these were shut down for economic reasons in 1962 [5].

There is diversity in the design of the different Fischer–Tropsch facilities. All produced trans-portation fuels and some additionally produced lubricant base oils and chemicals. The subsequentdiscussion gives an overview of the technology associated with the German Fischer–Tropschtechnology. Rather than discuss each plant separately, the refining of the syncrude is discussedgenerically.

6.2Synthesis Gas Production

The majority of facilities produced their synthesis gas from coke, not coal [2]. Specifically, theplants in the Ruhr area employed coke and coker gas for syngas production, whereas the plantsin central Germany directly employed brown coal for the production of syngas [6].

Fischer–Tropsch Refining, First Edition. Arno de Klerk. 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Published 2011 by Wiley-VCH Verlag GmbH & Co. KGaA.

120 6 German Fischer–Tropsch Facilities

Table 6.1 German Fischer–Tropsch facilities constructed in the period 1935–1939.

Plant Location Coal type as feed Production (kt a−1)a Products

Normal- Medium-pressure pressure

Brabag Ruhland-Schwarzheide Lignite 164.6 0 FuelEssener Bergkamen Bituminous 80.0 0 FuelHoesch Dortmund Bituminous 0 46.0 Fuelb

Kruppc Wanne-Eickel – 48.3 11.9 FuelRheinpreussen Homberg Bituminous 67.2 0 Fuel, acidsb

Ruhrchemie Sterkrade-Holten Bituminous 18.1 44.5 Fuel, lubricantSchaffgotsch Deschowitz-Beuthen Lignite 0 26.4 FuelViktor Castrop-Rauxel Bituminous 37.7 0 FuelWintershall Lutzkendorf-Mucheln Lignite 11.5 0 Fuel

aBased on actual production figures for 1942.bSmall amount of lubricants coproduced.cFirst stage of synthesis is normal-pressure, second stage is medium-pressure.

The first step in synthesis gas production was to convert the coal into coke using a cokingoven (Figure 6.1) [7]. The coke obtained from the coking oven was then gasified with O2 andsteam to produce a syngas with H2:CO ratio around 1 : 1. For example, at the Rheinpreussenfacility, coke gasification took place in Koppers high-temperature-entrained flow gasifiers(Section 3.4.4) [2].

In almost all of the German facilities, the syngas was cleaned in a two-step process. Thefirst ‘‘coarse purification’’ step employed the standard iron oxide process, which was a standardprocess for H2S removal at that time. The H2S was removed by passing the raw syngas over alarge bed of iron oxide (Fe2O3) at 40–50 ◦C and near atmospheric pressure [8]. The iron oxidewas usually dispersed on a porous material such as wood shavings. Regeneration took placeby reoxidation with air and subsequent extraction of the sulfur [9]. This was an unwieldy, butwidely adopted technology, which required a large plot space owing to the size of the multipleiron oxide boxes. In the second ‘‘fine purification’’ step, the organic sulfur compounds wereremoved by passing the syngas over an Fe2O3 –Na2CO3 catalyst (100 : 16 mixture by mass [9])at a temperature of 175 ◦C and increasing the temperature with catalyst age up to 280 ◦C. Theaddition of around 0.2 vol% O2 to the synthesis gas was beneficial for both sulfur removal steps[2]. The target specification for sulfur was less than 2 mg·m−3 syngas [9].

The water gas shift (WGS) catalyst employed for syngas conditioning was a typicalFe2O3 –Cr2O3-based high-temperature WGS catalyst. The WGS catalyst contained 38.5%Fe2O3, 18.2% CaO, 5.4% Cr2O3, 5.2% MgO, 18.0% H2O, and various other minorconstituents [2].

It was reported that coking the coal beforehand had some additional advantages. Thecarbonization of coal in a coke-oven produced two important by-products apart from coke.When the coal is pyrolyzed, the coal pyrolysis liquids (coal tar) could be recovered as a lightoil rich in aromatic compounds. A typical light oil obtained by condensation from coke-oven

6.3 Fischer–Tropsch Synthesis 121

Coke-oven Syncrudeand tail gas

Light oil(coal tar)

Coker gas

Coal

Gasifier

Iron oxide process

Fischer−Tropschsynthesis

Coal tarseparation

Final purifier(Fe2O3−Na2CO3)

H2:CO = 1:1

Coke

Sulfur removal

Water gas shift

Thermal reformer(noncatalytic)

H2:CO > 2:1

Aromatic oil

O2steam

Figure 6.1 Generic process flow diagram of synthesis gas production in German Fischer–Tropschfacilities.

gas contained 57% benzene and 13% toluene as the major components, the remainder beingsulfur compounds, aliphatic hydrocarbons, and heavier aromatics [10]. These coal liquids werevaluable blending components in fuels production (Sections 6.4.2 and 6.4.3).

Coker gas consisted mainly of H2 (50–55%), CO (5–10%), and CH4 (25–30%) on a dry basis,the rest being combustion gases and inerts [11]. The coke-oven gas could be thermally reformedin a noncatalytic process with steam at high temperature (1200 ◦C) to produce a hydrogen-richsyngas. By doing so, it reduced the amount of gas from coke gasification that had to be subjectedto WGS in order to obtain an H2:CO ratio of 2 : 1 for Fischer–Tropsch synthesis [2].

6.3Fischer–Tropsch Synthesis

Much of the development leading to the industrial application of Fischer–Tropsch synthesis hasto be credited to Otto Roelen. He was responsible for the development of the cobalt-based catalystthat became the standard Fischer–Tropsch catalyst in all Fischer–Tropsch facilities based on theGerman Ruhrchemie technology [1].

The initial Co-LTFT catalyst consisted of a mixture of Co, ThO2, and kieselguhr in a ratio of100 : 18 : 100. The composition was modified in 1938 to include magnesium oxide, to become thestandard catalyst throughout the Second World War. This catalyst employed Co, ThO2, MgO,and kieselguhr in a ratio of 100 : 5 : 8 : 200 [12]. The particle size of the catalyst was 2–3 mm [13].The bulk density of the catalyst was such that the Co content was about 0.1 kg·m−3 of reactorvolume [9].


Three modes of deactivation were identified, namely, pore blockage by the product wax,poisoning by sulfur and carbon deposits, and sintering. No oxidation or cobalt silicate formationwas observed [12]. The absence of oxidation is likely a consequence of the low-temperatureand low water partial pressure operation of the German Fischer–Tropsch technology. Themedium-pressure process also experienced metal leaching [13], which is further discussedin Section 6.3.2.

6.3.1Normal-Pressure Synthesis

Fischer–Tropsch synthesis by the normal-pressure process was carried out in the operatingrange 180–200 ◦C and 30 kPa. The gas hourly space velocity (GSHV) was on the order of 100 h−1

at the inlet.The normal-pressure Fischer–Tropsch reactors were about 5 m long, 2.5 m wide, and 1.5 m

high. Each reactor consisted of tubes and heat transfer plates, with the catalyst being loaded onthe shell-side between the heat transfer plates (Figure 6.2) [2, 9, 13]. Water was circulated inthe tubes to regulate the temperature. The catalyst bed was typically operated at a temperature5–8 ◦C higher than that inside the tubes. The reactor temperature could be controlled to within1 ◦C in the range 170–200 ◦C by regulating the water pressure, using a boiler principle. The tubescould withstand a pressure of 3 MPa. The heat release during normal-pressure Fischer–Tropschsynthesis was about 150 kJ·m−3 synthesis gas, which is equivalent to about 1.5 MJ·kg−1 ofproduct [9]. Each reactor had a total internal volume of 12 m3 for catalyst and tubes, and eachreactor contained 900 kg of Co [1].

In order to achieve a reasonable synthesis gas conversion, normal-pressure plants employed twoor three Fischer–Tropsch synthesis stages in series. After each reaction stage, the condensableproducts were removed by direct condensation in a spray cooler (Figure 6.3), through whichwater formed during synthesis was also removed that in turn reduced oxidation of the catalystin the later stages of synthesis [9]. Another advantage was that the volume of the gas feed to thefollowing stage was reduced, which improved the utilization of reactor volume (Table 6.2) [9].

Water tubes

Catalyst(between plates)

PlateOutside 34 mm

Inside 29 mm

Figure 6.2 Internals of a normal-pressure Fischer–Tropsch reactor.


Tail gas

Catalyst wax

Syngas

LTFT

LTFT

LTFT

First-stagesynthesis

Second-stagesynthesis

Carbon gasoline

Condensate oil

Aqueous product

Crude LPG

Carbonabsorber

Figure 6.3 Synthesis section of a typical two-stagenormal-pressure German Fischer–Tropsch facility. Dashedlines indicate discontinuous flow.

Table 6.2 Performance of two-stage normal-pressureFischer–Tropsch synthesis over a Co–ThO2 –MgO–kieselguhrcatalyst at the Ruhrchemie facility.

Description Inlet After stage 1 After stage 2

Gas volume (m3)a 100 50.7 34.7Syngas volume (m3) 79.9 26.1 8.9Overall syngas conversion (%) – 67 89Overall CO conversion (%) – 78 96Gas composition (vol%)

H2 53.2 33.7 16CO 26.7 17.8 9.7CO2 14.4 29.6 44.2CH4 0.4 7 13.2N2 5.3 10.4 14.9Hydrocarbons 0 1.5 2

aAll data arbitrarily expressed on the basis of 100 m3 total gas feed to the first stage.

More reactors were required for the first stage of conversion than were needed for the secondstage of conversion. For example, at Ruhrchemie plant, the normal-pressure synthesis sectionemployed 18 reactors for the first stage and 9 reactors for the second.

Under normal-pressure operation, the Co-LTFT catalyst typically had a lifetime of aboutfour to six months. Deactivation because of blockage by wax required rejuvenation every


700 h. Rejuvenation entailed catalyst washing at 100 ◦C by spraying it with kerosene toextract the wax. The product thus obtained was called catalyst wax. The catalyst could alsobe treated with H2 at 200 ◦C to extend its useful operating lifetime [13]. At the normalrate of catalyst deactivation, a temperature increase of 1 ◦C was needed to maintain constantconversion.

The product recovery section at the end of the last synthesis stage entailed condensation andabsorption. The product was first cooled down by a spray cooler to yield an oil and a waterfraction, before the uncondensed gas was passed over a bed of activated carbon. The gaseoushydrocarbons were adsorbed onto the activated carbon bed from which the product was recoveredbatch-wise by steaming (Figure 6.3). The desorbed product from activated carbon adsorption wasthen stabilized by pressure distillation to yield an ‘‘active carbon gasoline’’ and a ‘‘crude liquidpetroleum gas (LPG).’’

The composition of the syncrude fractions from a typical normal-pressure process is given inTable 6.3 [9]. In addition to the hydrocarbon products, the syncrude also contained oxygenates,mostly alcohols and carboxylic acids, which gave it a characteristic smell. The amount of syncrudethat dissolved into the aqueous product was very little (<1%).

The aliphatic hydrocarbons in the naphtha fraction from normal-pressure Co-LTFT synthesishave been analyzed in detail by Friedel and Anderson (Table 6.4) [14]. The high degree of linearityof the acyclic aliphatic hydrocarbons is typical of Fischer–Tropsch synthesis. The 1-alkenecontent is quite low for Fischer–Tropsch synthesis, and the composition of the alkene fractionindicates that a significant amount of secondary reactions took place during the normal-pressureprocess.

Table 6.3 Composition of the various syncrude streamsobtained from German normal-pressure Fischer–Tropsch syn-thesis. The aqueous product contains <1% of the syncrude.

Description Catalyst wax Condensate oil Carbon gasoline Crude LPG

Mass of total syncrude (%) 2 40 50 8Composition (%)

H2, CO, and CO2 – – – 15–40Methane – – – 2–3Ethane and ethene – – – 1–2Propane and propene – – 1 15–20C4 hydrocarbons – – 5–15 20–40C5 hydrocarbons – – 15–20 10–20C6-180 ◦C fraction – 1–3 70–75a 3–5180–230 ◦C fraction (Kogasin I) – 35–40 – –230–320 ◦C fraction (Kogasin II) – 30–35 – –320–460 ◦C fraction (Slack wax) 20–30 20 – –>460 ◦C fraction (Hard wax) 70–80 1 – –

aIn the source reference the carbon gasoline did not add to 100%; only the C6 fraction (20–25%) was tabulated and theheavier gasoline was omitted from the table.


Table 6.4 Composition of the acyclic aliphatic hydrocarbonsin the C5 –C8 naphtha from the German normal-pressureFischer–Tropsch process.

Composition C5 C6 C7 C8

Alkane selectivity (vol%)Linear 95 90 88 85Methyl branched 5 10 12 15

Alkene selectivity (vol%)1-Alkene – a 36 28 18cis-Alkene (internal) – a 25 30 30trans-Alkene (internal) – a 39 42 52

aNot reported.

6.3.2Medium-Pressure Synthesis

The yield of wax and liquid products from Co-LTFT synthesis improved when the pressurewas increased (Table 6.5) [7]. The medium-pressure process was developed to exploit this yieldincrease by operating at 180–200 ◦C and 0.5–1.5 MPa. The GSHV was on the order of 100 h−1

at the inlet. It was also found that the catalyst lifetime improved to six to nine months byoperating at a higher pressure, because of the solvent action of the condensed products in thereactor [13].

The medium-pressure Fischer–Tropsch reactor (Figure 6.4) was of a different design comparedto the normal-pressure reactor (Figure 6.2). The reactor consisted of a vertical pressure vessel,4.5 m in height and 2.7 m in diameter. On the inside it was fitted with 2044 double jacketed

Table 6.5 Effect of pressure on the product yield obtainedwith a Co–ThO2 –kieselguhr catalyst averaged over afour-week period.

Pressure (MPa) Product yield (g·m−3 of CO + H2)a

C5-200 ◦C >200 ◦C oil Oil-free wax Wax and liquidsb

0 35 35 9 1090.15 46 40 14 1220.5 30 48 56 1391.5 30 34 66 1355 19 34 50 12815 19 32 24 98

aSyngas volume at normal conditions.bAll solid and liquid products, including LPG.


Water

Catalyst(in annulus)

24 mm

48 mm

Detail of double tube

Figure 6.4 Internals of a medium-pressure Fischer–Tropsch reactor.

tubes. The catalyst was loaded into the annular space between the shell and the inner tube[2, 13]. Each medium-pressure reactor had space for about 10 m3 of catalyst, which was equivalentto about 1 ton of Co [9].

The configuration of the synthesis section was otherwise very similar to that of thenormal-pressure process (Figure 6.3). Multiple stages were employed for the same reasonsas in the case of the normal-pressure process, thus achieving a high syngas conversion (Table 6.6)[13]. The GHSV was increased in each stage, with the last stage having double the space velocityof the first stage. The lower H2:CO ratio was also found to be beneficial in compensatingfor the lower alkene selectivity and to improve the overall conversion efficiency of the process(Section 6.3.4).

Table 6.6 Performance of three-stage medium-pressure(0.9–1.0 MPa) Fischer–Tropsch synthesis over aCo–ThO2 –MgO–kieselguhr catalyst at the Ruhrchemiefacility.

Description Inlet After stage 1 After stage 2 After stage 3

Gas volume (m3)a 100 49.6 26.9 18.9Syngas volume (m3) 87.4 34.2 11.3 4.8Overall syngas conversion (%) – 61 87 94Overall CO conversion (%) – 61 91 98Gas composition (vol%)

H2 52.7 33.9 18.2 11.5CO 34.7 35 23.9 14CO2 6.9 14.7 28 36.3CH4 0.4 5 11.3 15.7N2 5.2 10.5 17.4 21Hydrocarbons 0 0.9 1.15 1.25

aAll data arbitrarily expressed on the basis of 100 m3 total gas feed to the first stage.


The higher operating pressure required some changes to the detailed design of the synthesissection. Many of these changes were necessitated by the corrosiveness of the short-chaincarboxylic acids that were formed during medium-pressure Fischer–Tropsch synthesis. Partsof the plant were constructed with mild steel, which is not resistant to corrosion by aqueoussolutions of carboxylic acids. In order to prevent such corrosion, condensation of the aqueousproduct phase had to be prevented. The gas lines leaving the synthesis reactor were insulated toprevent condensation and the gas from interstage spray coolers was preheated to 160 ◦C [13].

After 90 h time on stream at 180 ◦C and 1 MPa, the wax produced during the medium-pressureprocess turned black. With increasing time on stream, the ash content of the wax went througha maximum, decreasing to zero after 360 h from the start of the run. The ash contained carbonand mineral matter derived from the catalyst. In parallel, some cobalt leached into the aqueousproduct and remained at a level of 25–50 µg·g−1 even though the ash content in the waxdecreased [13].

The increase in operating pressure resulted in a change in the syncrude composition betweenthe normal- and medium-pressure processes (Table 6.7) [7, 9]. The increased pressure resultedin the formation of heavier and more hydrogenated products. The medium-pressure process wasbetter suited for diesel fuel, chemicals, lubricants, and wax, whereas the quantity and quality ofthe gasoline deteriorated significantly.

6.3.3Gas Loop Design

High conversions of syngas (90–95%) were obtained in both the normal- and themedium-pressure Fischer–Tropsch processes (Tables 6.2 and 6.6). The use of an open gas loopdesign is therefore not surprising.

There was a desire to increase alkene production from the medium-pressure process, whichwould improve the quality of the gasoline, as well as its synthetic uses. It was found that byrecycling the syngas after the first-stage conversion, the alkene content could be significantlyincreased without a loss in the overall product yield. In fact, the space–time yield was increasedduring recycling (Ger. ‘‘Kreislauf’’) operation. Despite the advantages of this closed loop designemploying an internal recycle, it happened too late to be generally introduced [9].

Table 6.7 Product distribution obtained from Germannormal- and medium-pressure Fischer–Tropsch processes.

Product fraction Normal-pressure process Medium-pressure process

Yield (%) Alkenes (%) Yield (%) Alkenes (%)

Tail gas 16 – 14 –C3 –C4 (LPG) 12 43 9 40C5-180 ◦C (Gasoline) 39 37 22 24180–230 ◦C (Kogasin I) 14 18 20 10230–320 ◦C (Kogasin II) 9 8 11 –320–460 ◦C (Slack wax) 7 – 15 –>460 ◦C (Hard wax) 3 – 9 –


Table 6.8 Carbon efficiency of the German three-stagemedium-pressure Fischer–Tropsch process under differentoperating conditions.

Description Feed gas H2:CO ratio

2 : 1 1.6 : 1

Coke requirement (kg/kg product recovered) 4.99 4.35H2 + CO volume in feed (%) 81 86.5Overall syngas conversion (%) 90.8 95Average catalyst lifetime (h) 4015 2745Product yield (g/m3)a of CO + H2

Total liquids and solids 126.2 156.6Liquids and solids, excluding LPG (C3 –C4) 138.4 144.4

aSyngas volume at normal conditions.

The following specific advantages of introducing an internal recycle in the first conversionstage have been noted [4]:

1) Higher concentration of alkenes in the product.2) Synthesis less sensitive to operating disturbances and variation in the syngas feed.3) Increased yield of products per volume of syngas.4) Lower catalyst cost and requirement of a small number of units for the same production.5) Shorter start-up period required to bring a synthesis reactor on line.

6.3.4Carbon Efficiency

The US Navy Technical Mission in Europe has reported the carbon efficiencies of the three-stageGerman medium-pressure process using different operating conditions (Table 6.8) [4]. Operatingat a lower H2:CO ratio was beneficial for carbon efficiency, but the Co-LTFT catalyst lifetime wasshortened.

It is important to reiterate that the feed material is coke (Section 6.2). On a coal feed basis,the overall carbon efficiency of the process is higher, since additional liquid products from coalpyrolysis are coproduced in the coke-oven during coke production.

6.4Fischer–Tropsch Refining

The main product fractions obtained from stepwise cooling after Fischer–Tropsch synthesis isindicated in Figure 6.3. It is convenient to discuss the refining of the Co-LTFT syncrude bytracing the upgrading pathway of each of these fractions. Some of the main design features foundin the Fischer–Tropsch refineries associated with the normal- and medium-pressure processes

6.4 Fischer–Tropsch Refining 129

Catalyst waxLTFT

Carbon gasoline

Condensate oil

Aqueous product

Crude LPG

Carbonabsorber

Spraycooler

NaOHwash

SolventrecoverySyngas

Medium wax

Hard wax

Waste water

Fatty acids

Diesel fuel

Gasoline

LPG

Paraffinoxidation

Steamstripping(vacuum)

Diesel fuelKogasin I (180−230 °C)

Kogasin II (230−320 °C)

Slack wax(>320 °C)

Sweating /deoiling

Tm > 90 °C

Tm = 50−70 °C

Oligomerizationor hydration

GasolineOligomers

Alcohols

Tail gas

Medium wax

Figure 6.5 Generic German Fischer–Tropsch refinery. Dashed lines indicate discontinuous flow.

are illustrated in Figure 6.5; it is a generic refinery design and does not represent any specific

refinery design.

6.4.1Refining C3 –C4 Crude LPG

The German Fischer–Tropsch facilities upgraded the C3 –C4 syncrude fraction (crude LPG or

‘‘Gasol’’) in different ways. The alkene content in this fraction was very important, because it

enabled two important upgrading pathways, namely, oligomerization and hydration.

Some of the Fischer–Tropsch facilities, such as the Viktor-plant, made use of liquid phosphoric

acid (H3PO4)-catalyzed oligomerization to convert the C3 –C4 alkenes into heavier alkenes. The

method practised in Germany used a reactor consisting of three silvered tubes connected

in series in a single water-cooled reactor. The tubes were 5 m high and had a diameter of

0.18 m. Each tube was loaded with 40 kg of acid and 70 kg of oligomer to about one-third of


its height. The lighter alkenes were then pumped through the tubes. The process had an inletpressure of 6 MPa and outlet pressure of 4 MPa. Reaction took place at 180–200 ◦C and analkene conversion of 90% was achieved. Entrained phosphoric acid was separated from theproduct and recycled.

Phosphoric acid catalyzed oligomerization is an important Fischer–Tropsch refining technol-ogy and it is discussed in detail in Section 19.3.1. Despite the high quality of the gasoline derivedfrom this process, it was not practised on a large scale for the conversion of Fischer–Tropschsyncrude. The production of gasoline by Fischer–Tropsch synthesis was not favored in Germanyat that time, and much of the gasoline was produced by direct coal liquefaction [2].

The C3 –C4 alkenes could, in principle, also be oligomerized using AlCl3, as was done in the caseof lubricant manufacturing. However, the quality of the lubricating oil deteriorates when lightermaterials are employed [15]. Although these alkenes could, in principle, be coprocessed with thealkenes derived from thermal cracking of heavier Fischer–Tropsch fractions (Section 6.4.3), it isnot clear whether this was done in practice.

The C3 –C4 fraction was also employed as a feedstock for the production of alcohols by indirecthydration using the sulfuric acid process. In this process, the sulfuric acid solution dissolves thealkenes resulting in the formation of sulfuric acid esters (Equation 6.1), which is then hydrolyzedin a subsequent step to yield the alcohols (Equation 6.2) [16].

2CnH2n + H2SO4 → (CnH2n+1)2SO4 (6.1)

(CnH2n+1)2SO4 + 2H2O → 2CnH2n+1OH + H2SO4 (6.2)

Oligomerization of the alkenes is a side reaction during this process. These olefinic oligomersmake a good-quality gasoline blending stock, and the oligomers thus produced were blendedinto the gasoline. This is a nice example to demonstrate the synergy between hydration andFischer–Tropsch refining. In isolation, alkene oligomerization as a side reaction may be viewedas a drawback, but in the context of refining it is not a drawback at all.

The alkane-rich C3 –C4 fraction that remained after alkene conversion by either oligomerizationor hydration was compressed and bottled as LPG.

6.4.2Refining Carbon Gasoline

The straight-run properties of the carbon gasoline, also called ‘‘A-K’’ gasoline, were very dependenton the operating conditions of the Fischer–Tropsch reactors. The degree of branching inFischer–Tropsch naphtha is generally low and the naphtha from the German Fischer–Tropschprocess was no exception (Table 6.4). The n-alkanes have very low octane numbers and make poorgasoline. The only components in the straight-run material that had high octane numbers were thealkenes and specifically the internal alkenes, which were a major product in the normal-pressureprocess. The alkene content of the carbon gasoline was higher in the normal-pressure processthan in the medium-pressure process (Table 6.7), and this was reflected in the octane numbersof gasoline from the two processes (Table 6.9) [2, 4, 13, 17, 18].

The German motor-gasoline specifications at that time required a motor octane number(MON), after tetraethyl lead (TEL) addition, of at least 72 and a minimum density of 720 kg·m−3.The minimum density specification increased to 740 kg·m−3 if both TEL and aromatics were


Table 6.9 Research octane number (RON), motor oc-tane number (MON), and density of different fractionsfrom the straight-run naphtha of German normal- andmedium-pressure Fischer–Tropsch synthesis.

Naphtha fraction Normal-pressure process Medium-pressure process Density (kg·m−3)

RON MON RON MON

C5-90 ◦Ca – 73 – – 656C5-110 ◦C – 67 – – –C5-110 ◦Ca – 66–68 – – 670–671C5-130 ◦Ca – 58 – – 683C5-140 ◦C – 62 – – –C5-150 ◦C 57 55 38 – 660C5-160 ◦Ca – 49 – – 694C5-180 ◦C (bauxite treated) – 50 – 25 –C5-200 ◦C 43 40 25 – 704C4 –C10 (175 ◦C) 52 – 28 – 689C4 –C11 (200 ◦C) 49 – 25 – 693

aRange based on T95 distillation temperature; the end point is typically 10–20 ◦C higher.

added to the gasoline [3]. The straight-run Fischer–Tropsch gasoline fell short of both octanenumber and density specifications. It was therefore a common practice to blend the poor-qualitysynthetic gasoline from Fischer–Tropsch synthesis with the aromatic-rich coal tar (‘‘benzole’’)and alcohols in line with the then-existing German motor-gasoline specifications [2]. A mildcaustic washing step was also required as a polishing step to remove the dissolved carboxylicacids from the gasoline [2].

The Fischer–Tropsch gasoline was of too poor quality to be considered for aviation-gasoline.Different refining strategies were evaluated at that time to improve the quality of the gasoline

from the German Fischer–Tropsch processes. The studies focused on the heavy naphtha fraction,because the lighter boiling fraction inherently was of a better quality (for an explanation seeChapter 13). In fact, the heavy naphtha was sometimes employed as a blending component fordiesel fuel (Section 6.4.3) in order to avoid degrading the quality of the gasoline.

Universal Oil Products (UOP) investigated the upgrading of the syncrude from a Germannormal-pressure process [17]. The origin of the Fischer–Tropsch syncrude was not disclosed, butat that stage only normal-pressure facilities were in operation. The light naphtha fraction (C5,110 ◦C) was removed by distillation to leave the heavier C8 –C11 naphtha for further upgrading.The C8 –C11 naphtha had an MON of 40 and density of 732 kg·m−3 and could clearly benefitfrom further refining. It was thermally reformed (catalytic reforming had not yet been invented)at 550 ◦C and 5 MPa to increase its octane number to 57–62 depending on the residence time.Reforming was accompanied by cracking, and the reformate yield was 69–74 vol% of the feed.The production of ‘‘polymer gasoline’’ from the lighter alkenes by oligomerization over solidphosphoric acids was also reported (Section 19.3.1).

Thermal cracking at temperatures above 650–700 ◦C by the true-vapor-phase (T-V-P) processwas evaluated for the conversion of the heavy naphtha into a more olefinic, higher octane


number product [18]. The design of the T-V-P process is such that it uses thermal cracking toproduce light alkenes, but then allows the alkenes to react by thermal oligomerization (Section19.3.6) to produce a heavier, higher octane number gasoline. This allowed the C3 –C4 fractionfrom Fischer–Tropsch synthesis to be co-fed to the T-V-P process, in which the C3 –C4 alkeneswere converted to heavier olefinic products during thermal oligomerization of the process. Thefinal gasoline blend between carbon gasoline and gasoline from T-V-P process cracking had anMON (before TEL addition) in the range 63–70 depending on the ratio of the blend. Despite thedemonstrated ability of this process to upgrade naphtha, the cracking plant that was installed atthe Ruhrchemie facility was not used for this purpose [2].

Hot clay treating of the naphtha was found to increase the octane number, and an increaseof up to 20 units could be achieved by Ruhrchemie [3]. This improvement was obtained bydouble bond isomerization of the 1-alkenes to internal alkenes (Section 16.4.1), a process that isespecially well suited for the upgrading of Fischer–Tropsch-derived olefinic naphtha.

6.4.3Refining of Condensate Oil

The condensate oil contained little naphtha (Table 6.3), and in this respect the stepwise cooling ofthe Fischer–Tropsch products resulted in useful pre-fractionation of the syncrude. The distillatewas recovered from the heavier wax fraction by atmospheric distillation (Figure 6.5). Threeproducts were obtained: Kogasin I, a kerosene fraction (180–230 ◦C); Kogasin II, a distillatefraction (230–320 ◦C); and slack wax, a waxy paraffinic bottom product from atmosphericdistillation.

Oxygenate partitioning between the condensate oil and aqueous product was not at equilibrium.A caustic wash step was included to neutralize (Equation 6.3) and remove carboxylic acids fromthe condensate oil before atmospheric distillation.

R – COOH + NaOH(aq) → R – COO−Na+(aq) + H2O (6.3)

The cutpoint of the Kogasin II fraction was typical of a light diesel fuel (equivalent to the USD-1 diesel fuel). By operating the boiler of the atmospheric distillation column at a temperatureclose to 320 ◦C, problems with thermal cracking of the reactive Fischer–Tropsch syncrude in theboiler was avoided.

Two types of diesel fuel were prepared from the Fischer–Tropsch synthesis, namely, a lightand a heavy diesel fuel (Table 6.10) [2, 3, 19]. The light diesel fuel was a mixture of heavynaphtha (Section 6.4.2) and Kogasin I and was used as a winter diesel fuel. The heavy diesel wasa mixture of Kogasin I and Kogasin II and was used as a summer diesel fuel. The heavy dieselfuel contained 2% oxygenates, mainly alcohols, carbonyls, and carboxylic acids, with some estersand phenolic compounds [19]. It was found that after removal of the polar compounds the cetanenumber of the heavy Fischer–Tropsch diesel fuel increased from 80 to 88 [19]. This is likely dueto the removal of the phenolic compounds. Phenolic compounds are known to improve storagestability by inhibiting oxidation. The phenolic compounds form stable free radical species toprevent the propagation of free radicals [20], and in the same way it inhibits compression ignition(for an explanation see Chapter 15).

Owing to the high n-alkane content of the diesel fuel, it generally had a highcetane number. Under laboratory test conditions, the cetane numbers obtained with the


Table 6.10 Selected properties of light and heavy diesel fuelfrom German Fischer–Tropsch synthesis and the German‘‘Sonder Diesel Kraftstoff’’ (SDK) specifications in the 1940s.

Fuel property Light diesel fuel Heavy diesel fuel SDK specification

Distillation range (◦C) 155–250 165–255a 195–310b 200–300a –Cetane number 75–78 >70 80 85 45 min.Density at 15 ◦C (kg·m−3) 743–749 745 772c 762 810–865Flash point (◦C) 27–49 >57 78 75 55 min.Cloud point (◦C) – – 0 – –10 max.Pour point (◦C) <–37 −38 −1 −9 –30 max.Viscosity at 40 ◦C (cSt) – – 2.1d – –Alkene content (g Br/100 g) – – 6.9 – –

aLight diesel (1943) and heavy diesel (1938) from the Ruhrchemie facility.bHeavy diesel fuel from German medium-pressure Fischer–Tropsch process operated under license by CarrieresKuhlmann in Harnes, France.cDensity reported at 20 ◦C is 768 kg·m−3.dSource value in Saybolt Second Units (SSU) at 100 ◦F: 1 cSt = 1 mm2 ·s−1 = [0.0022·(SSU) − 1.8/(SSU)]·100.

Table 6.11 Comparison of distillate fractions obtained dur-ing laboratory evaluations of the Co–ThO2 –MgO–kieselguhrcatalyst at 175–200 ◦C and H2:CO ratio of 2 : 1 for thenormal- (near atmospheric) and medium-pressure (0.7 MPa)processes.

Fuel property Normal-pressure process Medium-pressure process

C11 –C18 C12 –C19 C11 –C18 C12 –C19

Cetane number 100 100 100 105Density at 15 ◦C (kg·m−3) 760 766 760 766Pour point (◦C) −18 −9 −7 −2Alkene content (vol%) 15 13 10 8

Co–ThO2 –MgO–kieselguhr catalyst was even higher and the main difference betweenthe products from normal- and medium-pressure syntheses was the cold-flow properties(Table 6.11) [13].

As in the case of gasoline, the diesel fuel produced by Fischer–Tropsch synthesis fellshort of the German diesel fuel specifications of that time. Compared to a 47 cetane numbercrude-oil-derived diesel fuel, the Fischer–Tropsch-derived diesel fuel led to a 5% highervolumetric fuel consumption and had a 25% higher exhaust gas temperature [3]. TheCo-LTFT-derived diesel fuel on its own was not considered a good diesel fuel [2]. TheFischer–Tropsch material was blended with crude oil or coal-derived distillates. Such blendstypically contained around 40–45% Co-LTFT material.


In some of the German Fischer–Tropsch facilities, Kogasin II was also employed as a feedmaterial for the production of lubricating oil [21]. Converting this material into lubricating oilwas not just a war-time expedient, but it was considered to be its proper use [6]. Two processeswere primarily applied to convert the Kogasin II into feed material for lubricating oil production,namely, thermal cracking and chlorination.

Thermal cracking was performed at the Ruhrchemie facility. The Kogasin II was cracked in aDubbs thermal cracking unit at 500–520 ◦C and 0.4 MPa. Steam was passed into the crackingunit after heating and before it entered the expansion chamber, to limit thermal oligomerization.The alkene-rich product was then dried and oligomerized with AlCl3 in a batch reactor. Thequality of the product was controlled by gradually increasing the oligomerization temperature.Spindle oil was produced by oligomerization at 40–100 ◦C and aviation bright stock was producedby oligomerization at 15–60 ◦C (Table 6.12) [21]. These oils were recovered after posttreatmentby vacuum distillation. The Kogasin II from the German normal-pressure process was preferredfor the production of lubricating oil, because the Kogasin II from the medium-pressure processcontained more branched material [21]. It was also pointed out that the Kogasin II had tobe treated before cracking to remove traces of Co derived from the Fischer–Tropsch catalyst,because the Co catalyzed undesirable side reactions [2].

At the Rheinpreussen facility, the Kogasin II was batch-wise chlorinated at 80–120 ◦C atnear atmospheric pressure. The chlorinated oil was then used as an alkylating agent for theFriedel–Crafts alkylation of naphthalene. Aromatic alkylation was carried out in a batch reactor at70–100 ◦C using AlCl3 as the catalyst. After posttreatment, different oil fractions were recoveredby vacuum distillation (Table 6.12) [21]. Higher viscosity index (VI) oils were reportedly preparedby alkylation with chlorinated paraffins having an average carbon number of C16 [3]. These oilshad a VI of 105 and pour point of −7 ◦C. Lubricant base oils were also prepared from thermallycracked Fischer–Tropsch products in Japan. The properties were very similar, with a VI of 101,density of 865 kg·m−3, and pour point of −22 ◦C [22].

Table 6.12 Properties of lubricating oils prepared fromKogasin II by thermal cracking followed by AlCl3-catalyzedoligomerization and by chlorination followed byAlCl3-catalyzed alkylation of naphthalene.

Property Cracking–oligomerization Chlorination–alkylation

Spindle oil Aviation bright stock Spindle oil Turbine oil Cylinder oil

Density at 20 ◦C (kg·m−3) 845 865 901 928 965Pour point (◦C) −51 −26 −4 −26 −4Flash point (◦C) 193 321 171 202 274Viscosity index – ∼110 53 49 61Viscosity (cSt)a

At 38 ◦C (100 ◦F) – – 16 45 52At 50 ◦C (122 ◦F) 15 290 – – –At 99 ◦C (210 ◦F) – – 3 5 10

aSource values in Saybolt Second Units (SSU) – see Table 6.9 for conversion.


In the Ruhrchemie facility, some of the alkenes produced by cracking were converted by the‘‘OXO’’ process to alcohols [2]. The process entails hydroformylation of alkenes obtained bycracking with H2 and CO to produce aldehydes (Equation 6.4), which is then hydrogenated toalcohols (Equation 6.5).

R–CH=CH2 + H2 + CO → R–CH2 –CH2 –CH=O (6.4)

R–CH2 –CH2 –CH=O + H2 → R–CH2 –CH2 –CH2 –OH (6.5)

In the hydroformylation step, the alkenes were converted to aldehydes at 135–150 ◦C and15–20 MPa using the standard Fischer–Tropsch catalyst, but without MgO. The alkenes werepre-fractionated into different carbon number cuts (C11 –C12, C13 –C14, C15 –C16, and C17) thatwere converted separately to enable separation of the alkenes and aldehydes after reaction bydistillation. The hydrogenation step could also be performed with the Fischer–Tropsch catalyst,but a cheaper Ni-based hydrogenation catalyst was preferred.

Some of the distillate range material was sold and was employed as feed for the production of‘‘mersol’’ detergents. The detergents were obtained by light-induced free radical sulfochlorination(Equation 6.6) followed by saponification [6, 9].

R–H + SO2 + Cl2 → R–SO2Cl + HCl (6.6)

With Kogasin II feed, it was also possible to carry out sulfochlorination in the dark [9]. TheKogasin II apparently contained sufficient hydroperoxides to initiate the free radical reaction.Hydroperoxide formation does not take place during Fischer–Tropsch synthesis, but it is anatural consequence of exposing the reactive syncrude to air during transport and storage.

Other uses and applications of distillate range Fischer–Tropsch products that have beenconsidered in Germany at that time, have been discussed by Freerks [3].

6.4.4Refining of Waxes

The major portion of the waxes produced during normal-pressure Fischer–Tropsch synthesiswas obtained by the periodic removal of waxes from the catalyst by solvent washing. In themedium-pressure process, this wax fraction was removed because of the solvent action of theproduct that was present at high pressure. Slack wax was also recovered by atmospheric distillationof the condensate oil. The heavy wax product was separated by steam stripping, and the wax fromthe lighter fractions was recovered by sweating. Typical properties of Fischer–Tropsch waxesthus obtained are given in Table 6.13 [23].

Detailed analysis of the Fischer–Tropsch waxes revealed that the hard wax contained n-alkaneswith carbon numbers over C150 and a melting point of about 117 ◦C [24].

The slack wax fraction from atmospheric distillation and the waxy paraffins (Gatsch) thatremain after sweating to recover the heavier waxes, served as feed materials for the production ofchemicals. These conversions were not necessarily performed in the Fischer–Tropsch refinery.The material was mainly used for two processes, namely, cracking and oxidation.

Cracking of the slack wax fraction was performed in a way similar to Kogasin II cracking(Section 6.4.3). The aim was to produce lighter linear 1-olefins for the manufacture of lubricantsand detergents and oxidation. For example, slack wax was sold and converted in the I.G.-Politzplant to a lubricating oil by thermal cracking and AlCl3 oligomerization [21].


Table 6.13 Properties of different waxes obtained fromFischer–Tropsch synthesis at the Ruhrchemie facility. Cata-lyst wax is from normal-pressure synthesis. The other waxeswere obtained by distillation and/or sweating of product frommedium-pressure synthesis.

Properties Catalyst wax Soft wax Medium wax (Block wax) Hard wax

Congealing point (◦C) 87–91 42.5 50–52 90–93Clear melting point (◦C) – 44 53 110Density at 15 ◦C (kg·m−3) 904 – 899 921Mean molecular mass (g·mol−1) ∼550 – 380 600Acid content (mg KOH/g) – 0.14 0.03 0.1Alkene content (g I/100 g) 3.5 – 2.5 2.0

One of the important uses of the 320–460 ◦C slack wax fraction was as a crude paraffin feedfor the production of fatty acids by atmospheric oxidation [25]. The fatty acids were used as rawmaterials for the production of other products such as soaps and edible fats [2, 6]. Oxidation wasperformed in a special wax oxidation kettle that was constructed using aluminium with an alloysteel head to limit oxidation by the corrosive short-chain carboxylic acids. Manganese (such asKMnO4) and other metal carboxylates were employed as oxidation catalysts and oxidation wascarried out at 140–160 ◦C with air as the oxidant.

The heavier waxes were refined by bleaching and activated carbon absorption to removecolor components. The application of these waxes, which were substitutes for ceresin waxes(Tm = 68–72 ◦C, ρ = 920–940 kg·m−3 [26]), were dependent on their congealing point. Typicalapplications included the manufacturing of candles, insulation materials, and polishes.

Part of the heavier wax fractions was also oxidized to produce emulsifiable waxes [6]. The aimof this type of oxidation is to incorporate oxygenate functionality into the wax without degradingthe chain. Autoxidixation without chain degradation requires less severe conditions than arerequired for oxidation of slack waxes to produce fatty acids. Autoxidation of waxes and lighteralkanes is discussed later in more detail (Section 23.3).

6.4.5Aqueous Product Refining

The German Fischer–Tropsch processes did not produce much water-soluble oxygenates. At theRuhrchemie facility, the amount of water-soluble light alcohols produced was 1.16 g/kg of C3 andheavier products. The most abundant oxygenate class in the aqueous product was the alcohols(Table 6.14) [13]. In addition to the alcohols, carboxylic acids, aldehydes, and esters were alsofound in the aqueous product, but in smaller amounts.

The aqueous product was refined only in the Hoesch facility. The combined aqueous productfrom steam desorption of the activated carbon gasoline and wash coolers was distilled tocondense the oil. This concentrated the organic material from 0.5 mass% in the aqueous productto 70% in the overhead products from the column, of which 8–10% was nonalcohol oxygenates.

6.5 Discussion of the Refinery Design 137

Table 6.14 Alcohol composition of the Fischer–Tropschaqueous products from the Ruhrchemie and Hoesch facilities.

Compound Alcohol composition (%)

Ruhrchemie Hoesch

Methanol 10 10Ethanol 15 25Propanols 20 30Butanols 40a 25C5 –C6 alcohols – 10

aC4 –C6 alcohols.

The alcohol thus recovered was about 0.6% of the total syncrude and about 45% of the totalorganic matter in the aqueous product [13].

The carboxylic acids were also recovered at the Hoesch facility. The neutralized carboxylic acidsobtained from the oil condensate and from the bottom of the alcohol recovery columns wereacidified with H2SO4 to regenerate the carboxylic acids, and were extracted with a light aromaticsolvent. The carboxylic acid mixture consisted of 30% C2 –C4, 30% C5 –C9, 35% C10 –C20, and 5%heavier carboxylic acids. This constituted a recovery of 0.4% of the total syncrude and about 30%of the total organic matter in the aqueous product [13].

6.5Discussion of the Refinery Design

The diversity in the German Fischer–Tropsch refinery designs make it quite clear that there aremany ways to refine syncrude. Some design decisions make sense only in historic context. Therefinery designs must be evaluated in terms of the product specifications at that time. One shouldalso bear in mind that in the late 1930s very few catalytic processes were available (Table 2.2). Asa consequence, a fair number of the refining technologies that were selected for upgrading theFischer–Tropsch syncrude employed free radical mechanisms.

Despite the limitations imposed by the technology at that time, there are valuable lessons tobe learnt from these designs, which are also applicable to modern Fischer–Tropsch refinerydesign [27].

1) The refineries were designed to produce transportation fuels, chemicals, and lubricatingoils. The ratio of liquid fuels to chemicals and speciality products were 72 : 28 [6]. Thisresulted in considerable product diversity. The value of syncrude as a clean raw material forchemical production was realized, and many of the senior German officials involved withFischer–Tropsch technology were at pains to point out that syncrude has far more potentialfor chemical production than for fuels [2].

2) Alkenes are valuable. The alkenes were important for gasoline quality, chemical man-ufacturing and for the production of lubricating oils. It was not that alkanes were not


useful, but apart from the heavy waxes, much effort was expended on activating the alkanesby processes such as cracking and chlorination to enable transformations that could beperformed directly with alkenes.

3) The quality of the fuels produced from Co-LTFT synthesis was generally poor and failed tomeet the German fuel specifications. The naphtha and distillate fractions may have beenreferred to as gasoline and diesel fuel, but were actually only blending components for finalfuels.

4) The coal liquids coproduced in the coke-ovens during syngas production was quite valuablein providing an aromatic blending stock to upgrade the Fischer–Tropsch liquids. Therewas synergy between the coal liquids and Co-LTFT syncrude for fuels and lubricating oilproduction.

5) The German normal-pressure process with its lighter product (lower α-value) and higheralkene content was better suited for fuels production than the medium-pressure pro-cess. About 75% of the normal-pressure Co-LTFT syncrude was naphtha and distillate,and an even higher liquid fuel yield (>80%) was possible by conversion of the C3 –C4

olefins.6) The stepwise cooling of the syncrude as the first refining step pre-fractionated the syncrude

in a sensible way that simplified refinery design. Intermediate syncrude recovery also en-abled the use of Fischer–Tropsch reactors in series, which improved the syngas conversionand allowed a less complex gas loop design.

7) When comparing the Fischer–Tropsch refinery with a generic second-generation crudeoil refinery (Section 2.4.2) of that time, different refining technologies were important.In the refining of Fischer–Tropsch syncrude, the key technologies were oligomerization,aromatic alkylation, hydration, and cracking. Of these, only oligomerization and crackingwere employed in more advanced conventional crude oil refineries, such as those thatproduced aviation-gasoline.

8) The refinery design had to make provision for dealing with oxygenates. Oxygenates werealso considered valuable and oxygenate production was increased by processes such asoxidation, hydration, and hydroformylation. However, despite their value, much care had tobe taken in processing carboxylic acid containing streams. The carboxylic acids also dictatedmaterial selection for process equipment.

9) Metals and metal carboxylates from Fischer–Tropsch catalyst degradation ended up inrefinery streams. In processes where such materials were detrimental, specific provisionhad to be made for pretreating the feed.

10) Although the Fischer–Tropsch aqueous product contained <1% of the syncrude, part ofthe oxygenates, including carboxylic acids, was recovered in one of the refineries.

References

1. Stranges, A.N. (2007) A history of theFischer-Tropsch synthesis in Germany1926−45. Stud. Surf. Sci. Catal., 163,1–27.

2. Weil, B.H. and Lane, J.C. (1949) The Technologyof the Fischer-Tropsch Process, Constable,London.

3. Freerks, R. (2003) Early efforts to upgradeFischer-Tropsch reaction products into fuels,lubricants and useful materials. AIChE SpringNational Meeting, New Orleans, 2 April, Paper86d.

4. U. S. Navy Technical Mission in Europe (1945)The synthesis of hydrocarbons and chemicals

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7. Komarewsky, V.I., Riesz, C.H., and Estes, F.L.(1945) The Fischer-Tropsch Process. An Anno-tated Bibliography, Institute of Gas Technology,Chicago.

8. Gollmar, H.A. (1945) in Chemistry of Coal Uti-lization (ed. H.H. Lowry), John Wiley & Sons,Inc., New York, pp. 947–1007.

9. Asinger, F. (1968) Paraffins Chemistry and Tech-nology, Pergamon, Oxford.

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13. Storch, H.H., Golumbic, N., and Anderson, R.B.(1951) The Fischer-Tropsch and Related Syntheses,John Wiley & Sons, Inc., New York.

14. Friedel, R.A. and Anderson, R.B. (1950) Com-position of synthetic liquid fuels. I. Productdistribution and analysis of C5 –C8 paraffin iso-mers from cobalt catalyst. J. Am. Chem. Soc., 72,1212–1215.

15. Asinger, F. (1968) Mono-Olefins Chemistry andTechnology, Pergamon, Oxford.

16. Fielding, J.C. (1973) in Propylene and Its In-dustrial Derivatives (ed. E.G. Hancock), ErnestBenn, London, pp. 214–272.

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19. Ward, C.C., Schwartz, F.G., and Adams,N.G. (1951) Composition of Fischer-Tropschdiesel fuel. Cobalt catalyst. Ind. Eng. Chem., 43,1117–1119.

20. Scott, G. (1965) Atmospheric Oxidation andAntioxidants, Elsevier, Amsterdam.

21. Horne, W.A. (1950) Review of German syntheticlubricants. Ind. Eng. Chem., 42, 2428–2436.

22. Givens, E.N., LeViness, S.C., and Davis, B.H.(2007) Synthetic lubricants: Advances in Japanup to 1945 based on Fischer-Tropsch derivedliquids. Stud. Surf. Sci. Catal., 163, 29–36.

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25. Withers, J.G., West, H.L., and Ruhr-Chemie,A.G. (1946) Sterkrade Holten Interrogation ofDr. O. Roelen at Wimbleton November 15thand December 20th 1945. British IntelligenceObjective Sub-Committee Target No. 30/5.01,1946.

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