WhitePaper2 Final 10.24.17 - · PDF fileGT-BTX PluS® process scheme. ... Dependence of the...

GT-BTX PluS®

Reduce Sulfur–Preserve Octane Value-Produce Petrochemicals

Engineered to Innovate®

GTC TECHNOLOGY

WHITE PAPER

Engineered to Innovate®Richard Kolodziej PE, Joseph C. Gentry PE, and Sachin Joshi

GT-BTX PluS®: Reduce Sulfur–Preserve Octane Value-

Produce Petrochemicals

GTC Technology US, LLC Please send inquiries to [email protected] or visit GTC’s website at www.gtctech.com.

page 1

FCC Naphtha – Sulfur, Octane, and Petrochemicals

IntroductionSulfur reduction in � uid catalytic cracking (FCC) gasoline is an interesting, important topic to re� ners. Most worldwide speci� cations require sulfur to be reduced to very low levels. Traditional technologies use selective hydrodesulfurization, which results in an objectionable octane loss in the gasoline. GT-BTX PluS® technology is the best solution to address sulfur removal, while retaining ole� ns from undesired saturation by hydrogenation.

Many re� ners recover propylene from the light ends of the FCC, but they are less aware of the commercial process to recover aromatics or other products from the FCC Naphtha stream. GT-BTX PluS® enables recovery of aromatics, as well as an intermediate stream that is easily convertible into petrochemical-grade propylene.

SulfurSulfur reduction is a problem for many re� ners. It is an onerous requirement to stay in business, yet there is no economic bene� t gained. However, projects to accomplish sulfur reduction can be an opportunity to take advantage of innovative process technology to produce valuable petrochemicals that are otherwise missed.

Tier 3 (U.S.), Euro 5 (Europe, Middle East), and/or other similar regulations around the world are requiring the reduction of the sulfur content in � nished gasoline to <10 ppm. FCC Naphtha is the dominant source of gasoline sulfur, and as a result, methods are developed to pre-treat the FCC feed or post-treat the FCC gasoline. � e techniques for sulfur removal depend on the type of sulfur molecule. Mercaptans are easily removed by conversion to disul� des and extracted, or by mild hydrotreating. Sul� des are relatively easy to remove by hydrotreating, and thiophenes are removed by more severe hydrotreating. As the sulfur requirement decreases to lower levels, nearly all of the incremental sulfur removed is of the thiophenic type, which requires more severe hydrotreating and results in unintended ole� n saturation with commensurate octane loss. Each ole� n molecule converted to the corresponding para� n will lose approximately 20 octane numbers.





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Figure 1 provides details about the distribution of sulfur and ole� n species in FCC gasoline. Mercaptans are the dominant species in the lighter fraction, and thiophenes are dominant in the heavier cuts. Ole� ns are highest in the light fraction and lowest in the heavy fraction. Sulfur removal from the light cut is the easiest, and the heaviest fraction has hardly any ole� ns to matter in hydrodesulfurization. However, there are signi� cant thiophenic sulfur and ole� nic hydrocarbons boiling in the mid-cut napththa, which are the problem. � e mid-cut is most susceptible to ole� n saturation and octane loss via hydrodesulfurization, when going to the new lower levels required.

0

50 70

Sulfur Ole�ns

90 110 130 150 170 190

20

40

60

80

100

120

140

0

10

20

30

40

50

60

70

Sulfu

r, w

ppm

Ole

�ns,

wt%

Boiling Point, Dec C

Sulfur and Ole�ns Distribution by Boiling Point

Most susceptible tooctane loss in post hydrotreating

Figure 1: Sulfur and Ole� ns distribution by boiling pointReference: Shorey, S.W., D. A. Lomas, and W. H. Keesom (1999). Hydrocarbon Processing, v. 78, p. 11, 1999.





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Another representation of this e� ect is shown in Figure 2. Note the ole� ns and sulfur components in the mid-cut naphtha boiling range, nominally covering the C6-C8 components.

40 0

5

10

15

20

25

30

2

4

6

8

10

12

14

45 56 67 78 89 910 1011 1112

Ole�n Distribution

Perc

enta

ge %

Carbon Numbers Carbon Numbers

LIGHT LIGHTMEDIUM MEDIUMHEAVY HEAVY

Thiophene Distribution

Figure 2: FCC Gasoline – Ole� ns/Sulfur/RON Distribution

Sulfur Ole� ns RON

Light Low High High

Medium High High High

Heavy High Low Low





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C6-C9 Ole�ns

Octane Loss

Sulfur

Severe HDS

SHUFCC Naphtha

Hydrogen

Saturation(unavoidable)

Desulfurization(needed)

HCN

Hydrogen

LCN

C5-iC6-

ULS Gasoline

ULS Gasoline

Conventional sulfur removal processes for FCC gasoline use hydrodesulfurization, in a scheme shown in Figure 3. � e selective hydrogenation unit doesn't remove sulfur, but simply shifts some species into the higher boiling fraction. � e cut, which must have sulfur removed, also contains a large quantity of ole� ns that get saturated.

Similar to aromatics, the most di� cult sulfur species to be removed by HDS are the thiophenic type, which are ring-shaped components. � e novel method presented here is extraction of the sulfur along with the aromatics in the patented GT-BTX PluS® process using extractive distillation. � e ole� ns are rejected from the aromatics as well as the sulfur, allowing the extract stream to be desulfurized even to 1 ppm with insigni� cant saturation of the hydrocarbons.

FCC Naphtha HDS units often include a selective hydrogenation unit (SHU), which selectively hydrogenates di-ole� ns, isomerizes ole� ns, and alkylates ole� nic components with mercaptans into heavier disul� de compounds. � is can be used in conjunction with GT-BTX PluS®. � e heavier disul� des along with the extracted thiophenes combine together with the heavy-cracked naphtha for eventual desulfurization in the HDS reactor.

Figure 3: Conventional FCC gasoline desulfurization





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SHU GT-BTX PluS®

Severe HDS

FCC Naphtha

Hydrogen

DesulfurizedOle�n-rich NA Ra�nate

Aromatics/Sulfur-richExtract

C5-iC6-

LCN

160-300ºF

300ºF - EP

MCN

HCN

Majority of ole�nstaken away fromHDS, minimizingoctane loss fromsaturation

Less Hydrogen

ULS Gasoline

ULS Gasoline

ULS Gasoline

GT-BTX PluS® Process In GTC's design, we add a MCN draw (70-150º) from the naphtha splitter to feed into the GT-BTX PluS® process. � is extractive distillation process uses the proprietary TECHTIV® DS solvent, which selectively increases the boiling point of thiophenic sulfur and aromatic components over the ole� ns and para� ns. � is allows them to be rejected into a ra� nate stream. � e ra� nate is greatly reduced in sulfur and aromatics. � e extract, with aromatic and sulfur components, combines with the HCN (including the ole� n-alkylated sul� des and disul� des) which then feeds the more severe HDS to achieve ULS gasoline.

� e other advantage to the GT-BTX PluS® process is that ole� ns and H2S no longer co-exist in a hydrodesulfurization environment. � erefore, we avoid the chance of recombinant sulfur production, as is the case with the traditional FCC Naphtha hydrotreatment. Figure 3 below summarizes the GT-BTX PluS® process scheme.

Figure 4: GT-BTX PluS® scheme for FCC gasoline desulfurization





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Delta MON

Delta (R+M)/2

New regulationsrequire sulfurreduction > 99%

3.0

2.5

2.0

1.5

1.0

0.5

0.0

95 96 97 98 99 100

Oct

ane

Loss

Sulfur Reduction (%)

Octane� e obvious value proposition of GT-BTX PluS® is preservation of octane. Octane-barrel (bbl) costs are increasing. According to a recent report “Understanding Octane Value in America” by ADI Analytics’ Uday Turaga and Tyler Wilson, the value of an octane-bbl has risen signi� cantly in recent years, presently in the range of $2.50-$3.50/bbl. Some of the reasons for the increase in octane-bbl costs are higher use of para� nic crude oils having low octane, and higher compression automobile motors that require higher octane values. � ere is also a phase down on allowable aromatics in the gasoline pool, which otherwise would create more octane-bbls. � e GT-BTX PluS® economics are still reliable, even with octane-bbl cost below $1.00.

In order to hydrotreat the thiophenic sulfur from FCC gasoline to <10 ppm, there will be ole� n saturation resulting in an octane loss of 2-4 or more numbers.

At $3.00 per octane-bbl, a typical desulfurization unit would lose $20 million per year, for each drop in octane number. Selective HDS catalysts have undoubtedly improved over the years, but all of these will still saturate a signi� cant amount of the ole� ns with commensurate octane loss, when going to the ultra-low sulfur gasoline.

Figure 5: Dependence of the loss of octane number on the level of hydrosulfurization in HDS section of Prime G based on data by Axens





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PetrochemicalsAromatics are being phased down in motor gasoline, but there is a continued demand for BTX in the petrochemical sector. GT-BTX PluS® automatically produces high quality aromatics after the HDS section and is rich in toluene, xylenes, and C9 aromatics, which can all be converted into paraxylene.

Additionally, this process creates a new stream, rich in ole� ns, but essentially void of sulfur and aromatics. � e ole� nic-rich ra� nate from the GT-BTX PluS® process can go to any of three dispositions, each one having higher value than with the traditional processing scheme:

1) Process in a � xed-bed aromatization unit to generate additional aromatics. � e C4 and C5 fractions from the FCC can also go to this unit.

2) Recycle to the FCC unit to re-crack into mainly propylene, or use a segregated unit such as Gasol� nTM to re-crack into propylene and butylenes.

3) Blend into gasoline as a low-sulfur, low-benzene fraction having higher octane value than from traditional systems.

� e re� ner should not destroy these in order to reduce the sulfur.

More Severe HDS

SHU

Severe HDS B / T / X / C9A

GT-BTX PluS®

Gasol�nTM Unit forPropylene/Butylenes or Aromatization

ULSGasoline

ULSGasoline

LCN

C5-iC6-

MCN

70-150ºC

HCN

150ºC - EP

Hydrogen

FCC Naphtha

Less Hydrogen

Ole�n-richNA Ra�nate

Aromatics-rich Extract

Figure 6: GT-BTX PluS® for Petrochemical Production





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Ra�nate

Ra�nate

Solvent

H2O

Extract

HighOle�nicRecycle

Low Sulfur Low Ole�ns

HeavyLiquid Load,

PhaseSeparation

Issues

Solvent

Feed

Feed

Extract

LLE ED

Low Ole�ns

SRC

Low Sulfur

EDC

ApplicationRemoval of aromatics and sulfur from cracked gasoline cannot be easily done with liquid-liquid extraction because of objectionable internal recycles of the ole� ns, and problems with phase separation. Instead, GT-BTX PluS® uses extractive distillation with the proprietary TECHTIV® DS solvent. TECHTIV® DS is stable and non-reactive with the unsaturated components, capable to operate with feed impurities, environmentally acceptable, and performs well across a wide boiling range of feed, thus providing the highest level of sulfur removal, with simultaneous rejection of ole� ns.

SHU GT-BTX PluS®

Severe HDS

FCC Naphtha

Hydrogen

DesulfurizedOle�n-rich Ra�nate

Aromatics/Sulfur-richExtract

C5-iC6-

LCN

160-300ºF

300ºF - EP

MCN

HCN

Majority Ole�nstaken away fromHDS, minimizingOctane loss fromsaturation

Less Hydrogen

ULS Gasoline

ULS Gasoline

ULS Gasoline

Aromaticsplus Sulfur to HDS

Solvent RecoveryColumn (SRC)

Ole�ns RichRa�nate

Extractive Distillation Column (EDC)

Aromatics-rich Solvent

Lean Solvent

Techtiv® DS

MCN Feed Very low ole�ns

minimizes ole�n saturation, resulting in minimum octane loss

Majority Ole�nstaken away from HDS

Ole�ns Rich

taken away from HDS

Figure 7: Liquid-Liquid Extraction vs Extractive Distillation system for extraction of sulfur with rejection of ole� nic species. Objectionable recycles and phase separation problems occur with LLE.

Figure 8: An expanded rendition of the � ow scheme





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GT-BTX PluS®

1 MMTPA Unit, USGC Basis

CAPEX 23.0 MMUS$

OPEX 3.0 MMUS$

Figure 9: GT-BTX PluS® unit in Dongying, China

CAPEX and OPEX for a 1 MM ton per annum unit is:

Case StudyAt the beginning of 2016, a 400 KTA GT-BTX PluS® unit started up in Dongying, China. � is unit was added as a drop-in to the scheme with an existing FCC gasoline HDS unit. After the addition of the GT-BTX PluS® unit, octane loss was reduced from 4.0 to 0.6; � nal gasoline sulfur content was reduced from the level of 600 ppm to 2-7 ppm; and H2 consumption was reduced by 60%.





page 10

Light Gasoline

HydrotreatedGasoline

Treated FCCgasoline-to-gasolineblending

HydrogenHydrogen

FCCGasoline

New

Existing

Ra�nate

O�-gasExtracted Oil

Middle Gasoline

Heavy Gasoline

SHUGasoline

HDS

Light Column

Heavy Colum

n

EDC

SRC

Added Equipment

� e GT-BTX PluS® con� guration is quite simple. In this case, there were only three fractionating columns added, with re-use of the existing hydrodesulfurization reactor. Other schemes are also possible to conveniently retro� t. In the grassroots case, one may avoid the selective HDS section altogether and use a stand-alone GT-BTX PluS®.

SummaryRemoving sulfur from gasoline does not have to be a drain on re� nery pro� tability. � e key is to extract the sulfur species � rst, then hydrotreat only the extract. � is way, the ole� nic fraction does not go to hydrotreatment, which would cause substantial octane loss. � e hydrotreated extract is an excellent feedstock for paraxylene production. � e ole� nic ra� nate can go to simple aromatization to produce more aromatics; be cracked to produce propylene; or be blended into gasoline with very little change in octane value.

Reduce sulfur. Preserve octane value. Produce petrochemicals.

Figure 10: GT-BTX PluS® with three fractionating columns





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