Data SudChemie 7

7/31/2019 Data SudChemie 7

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MODERN REFINING CONCEPTS –No Oil Refining without Hydroprocessing

Dr. Hartmut Weyda, Dr. Ernst Köhler - SÜD-CHEMIE AG

Keywords: Aromatics Removal, Catalyst, Dewaxing, Diesel, Gas Oil, Gasoline, HDS, Hydrogen,Hydroprocessing, Hydrotreating, Oil Refining, PNA Removal, Pour Point, Zeolite

ABSTRACT

This paper provides an overview of the range of hydroprocessing applications especially for middledistillate range feedstocks, based on SÜD-CHEMIE’s catalysts. Key process is catalytic hydrodewaxing. Itis gaining increasing importance in terms of producing high quality diesel fuels and improving refiningeconomics. SÜD-CHEMIE provides to the refining industry various hydroprocessing catalyst packages,including catalytic hydrodewaxing, dearomatization, deep desulphurization and MHC-catalysts. All thesecatalyst packages mainly focus on the economic benefits of implementing these catalysts into existinghydrotreating units.

1. INTRODUCTION

The reformulation of transportation fuels, including diesel oils, is presently being discussed all over theworld. By the year 2005, based on the initiatives of the EU countries, especially the Scandinaviancountries, the third stage of the reformulation phase will be finalised. For diesel fuels this means a sulphurcontent less than 50 ppm, a lift-up of the cetane number, reduction in polyaromatics content and a densityand T95-point limitation. (Germany, for instance, is introducing so-called “Sulphur Free - Premium Fuels,i.e. less than 10 ppm sulphur, already beginning 2001.) This will, of course, also be linked with a decreasein distillation endpoint. Furthermore, there is a speciality interest to substantially improve cold flowproperties (Cloud Point, Pour Point and CFPP) of the diesel fuel, which means catalytic hydrodewaxing ofparaffinic feedstock components. Therefore, to fulfil all these legislative and regional requirements, therefineries have either to revamp existing units or invest into new hydroprocessing units. All in all, newconcepts using modern hydroprocessing technology will be required to meet future product specifications.

2. HYDROPROCESSING OPTIONS

General hydroprocessing in oil refining for upgrading refinery feedstocks largely is based on the presenceof heterogeneous catalysts being introduced into speciality designed reactors. The role ofhydroprocessing is to upgrade naphtha, distillates, heavy fuels and residual stocks by reducing orcompletely removing sulphur, nitrogen, metals or other contaminants. The most substantial variable insuch feed upgrading is the “Hydrogen” , especially the hydrogen partial pressure is effecting operationpredominantly. To date and on a world-wide basis there is a current hydroprocessing capacity installed of2 billion tons per year – an increasing capacity with the fuels specifications are becoming more restrictive.

Besides the adaptation of distillation, the specifications of today’s diesel fuels call for a number of catalyticbased hydroprocessing options, such as deep hydrodesulphurization (HDS) and catalytic hydrodewaxing

(HDX). Furthermore, to improve the refining margins and/or to increase the diesel pool, there also can bea need to add mild hydrocracking (MHC) or even hydrocracking (HC) to the existing process portfolio. Inthe near future it is already foreseeable that this list will be extended by dearomatization (HDAr).Specifications imposed by the Auto Oil Programme call for new processes enabling refiners to meet thearomatics targets, cetane improvement and a reduced gravity. Thus, a combination of HDS/HDX andHDAr will enlarge definitely the process portfolio not too far in the future. However, modern catalystsolutions are required for a well balanced performance of all the component reactions:

“HDX” ! “Deep HDS” ! “HDAr” ! “MHC/HC”.



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The diesel fuel yield is quite often limited by the need to comply with Cloud Point/Pour Point and densityspecifications, such that it is very common not to make full use of the boiling point range but to cut lessdeep than would be possible without the constraints. Other popular means to meet specifications arekerosene blending, addition of CFPP improvers (Cold Filter Plugging Point) which have a negligible effecton the Cloud Point only. It is quite obvious that all these methods have a negative impact on the productslate and the overall economy of a refinery.

Although, catalytic hydrodewaxing (HDX) has for several years been well established in the refiningindustry as an efficient tool to produce low Cloud Point/Pour Point diesel fuels as well as for lube oils, thegreat potential of this technology for improving refinery margins is by far not exhausted yet. In today’srefinery scene the most advantageous use of hydrodewaxing can be seen in complex configurations withother catalysts / processes, rather than in straightforward dewaxing to extreme cold flow properties - apartfrom arctic countries. Thus, the main focus of hydrodewaxing is not only on cold flow improvement but onmaking better use of refinery feedstocks and to improve the overall balance of refinery products in order tomaximise profits per barrel.

The numerous benefits of cold-flow-improvement technology depend largely on the application, and mayeven be very specific for each refinery due to different requirements in terms of middle distillates andgasoline production. Operating conditions also differ over a wide range. Lowest severity is normally seen

for combinations of catalytic dewaxing with hydrodesulphurization, which can consequently be operated atvery high space velocity - an LHSV of 6 h-1 in the dewaxing bed is not unusual (HDS: LHSV = 3 - 6 h-1).

While dewaxing was formerly confined to stand-alone applications mainly, the interest has now shiftedtowards the combination of hydrodewaxing and other hydrorefining processes in the same reactor due toobvious economic advantages. A number of commercial operations are in use since the beginning of the1990’s. The heart of these processes is the hydrodewaxing catalyst, which is of highly zeolite nature. Iteither selectively cracks or isomerizes normal-paraffins, which have poor cold flow properties, withoutsubstantially affecting other compounds like iso-paraffins, naphthenes or aromatics. Cracking typecatalysts are also selective to paraffinic side chains to naphthenic rings, so also providing dewaxingcapabilities for naphthenic crudes. An intrinsic feature of cracking type catalysts is the formation of lightproducts from heavier components, resulting in high octane gasoline and C1 - C4 gases. Depending on therefinery scheme, also these light products can also make an appreciable contribution to improved refinery

margins.

Operating Conditions Deep HDS Deep HDX HDX & HDS HDX & MHC

Temperature [°C] 300 – 420 350 – 420 330 – 420 370 – 420

Pressure [bar] > 27 > 30 > 35 > 50

H2 /Oil-Ratio [Nm³/m³] > 100 > 200 > 200 > 350

LHSV [h-1] up to 6 up to 4 up to 6 up to 1.5

Table 1 - Typical Operating Conditions – Upgrading of Diesel

SÜD-CHEMIE’s commercial dewaxing experience is based on its HYDEX-G, HYDEX-C and HYDEX-Lcatalysts, which are novel zeolite based catalysts for Gas Oil and Lube applications, respectively. All areextremely tolerant feedstock poisons (such as sulphur, nitrogen and water) and having a high selectivity tocracking of waxy n-paraffins. Operation of HYDEX-catalysts substantially improve the product quality interms of Cloud Point, Pour Point and Cold Filter Plugging Point characteristics. In most cases HYDEX-catalysts can be introduced to existing units without any massive capital investment.



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3. STAND-ALONE HYDRODEWAXING

Used in a single stage dewaxing reactor, the HYDEX-catalyst provides a tremendous potential for cloudand pour point improvement at moderate temperatures (Fig. 1). Resulting Pour Point is almost a linearfunction of operating temperature and, depending on the paraffinic content of the crude oil, the Pour Pointlimits are set by economics rather than by the capabilities of the catalyst. Yields, however, are veryreasonable within a wide range of operating conditions.

Catalytic hydrodewaxing technology is also effecting the gasoline pool. A major part of the cracked waxyparaffinic product is in the gasoline boiling range. Gasoline from this kind of operation provides high RONdue to its olefinic character and an appreciable share of iso-paraffins which is close to 25 %. Aromaticsare typically low and are of no concern regarding the blending pool.

TEMPERATURE FORTDELTA PP = 45 °CDELTA PP = 45 °C

P o u r P o i n t [ ° C ]

-60-55-50-45

-40-35-30-25-20-15-10

-50

335 340 345 350 355 360 365 370 375 380

HGO Feedstock:

IBP/FBP = 252/438 °CDensity = 896 g/lPP = + 10 °CSulphur = 2.54 %wt.

TEMPERATURE [°C]

400

21,4

24,2

6,9

43,2

2,8

0

10

20

30

40

50

C o

m p o u n d s [ % w t . ]

n-Paraffins

i-Paraffins

Naphthenes

Olefins

Aromatics

Gasoline Compounds Figure 1 - Deep Hydrodewaxing of HGO and the By-Product “Gasoline”

4. HYDRODEWAXING & DESULPHURIZATION

A major benefit of the HYDEX-G is that the catalyst can be implemented into existing reactors in caseswhere the target is both HDX and HDS. This keeps investment costs at a very moderate level and allowsfor revamps within a relatively short period of time. In those cases where the Cloud Point target ismoderate (∆CP/ ∆PP < 30 °C), HYDEX-G can be used as a simple retrofit without any further downstream

modifications in the product separation section in order to cope with the somewhat larger amount of lightproducts. Thus, the normal hydrotreater flow scheme is virtually unchanged (Fig. 2):

HDS

HDX

HDS R e a c t o r

Make-up Hydrogen

Feedstock

Recycle HydrogenPurge Gas

LPG

Gasoline

Diesel, Kerosene

L T - F l a s h

H

T - F l a s h

P r o d u c t S t r i p p e r

Figure 2 - Flow Scheme for combined processing HDX & HDS

Of course it is of utmost importance to maintain the desulphurization performance at the same level asbefore or lift it up even in view of future sulphur specifications, e.g. 350 ppm. Fortunately, new generationHDS catalysts, having about 30 % higher activity open up new opportunities in raising the space velocityand replacing part of the HDS catalyst by dewaxing catalyst. However, in most cases this is even possible

with the conventional HDS catalyst.



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There are a number of factors determining the performance of the process in terms of dewaxingcapabilities, temperature required for a certain CP/PP/CFPP-improvement as well as deactivation rates.Some of the more important factors are:

• Catalyst properties, such as zeolite acidity and crystallinity• Reactor design• Catalyst loading scheme

• Feedstock origin• Hydrogen supply (H2 /Oil-Ratio and Hydrogen Partial Pressure)• Flow Rate – Space velocity

Table 2 exhibits performance data from commercial operation confirming the relation between cold flowimprovement and yield as outlined above. The effect on density and cetane depends very much on thefeedstock. For this commercial installation the pay-back time has been 1.5 months only!

FEED PRODUCT

Sulphur %wt. 0.6-2.5 0.01-0.05Gravity g/l 860 855Distillation ASTM D-86 °C 5 % 279 180

50 % 333 32590 % 373 370

Cloud Point °C 17 7Colour ASTM D-1500 1.0 0.5Cetane Index 55 55Yield on DGO 180°C+ % 100 90

Winter Mode Delta CP = 10-20°C, Deep HDSFlexible Operation

Summer Mode HDS with maximum Gas Oil Yield

Table 2 - HYDEX-G Commercial Performance

Summarising the advantages of the integrated HDX/HDS-process, the following facts can be stated:"#HDX/HDS-processing allows to cut deeper into HGO. Additionally Kerosene blending can be avoided,thus increases yields on jet fuel/kerosene and diesel.

"#Replacement of CFPP improvers or, alternatively, better response to them, results in furthercontributions to improved overall economy.

"#The conversion of heavy paraffinic fractions into gasoline and LPG generates additional margins,depending on the refinery scheme and the markets.

However, the above performance is achieved without adversely affecting the HDS performance (e.g.product sulphur less than 350 ppm). This extremely flexible retrofit technology is currently getting a greatboost due to its attractiveness in economics. Commercial figures achieved with HYDEX-G are a clearproof of the convincing performance at minimum investment. A payback time within some months ispossible, provided the revamp can be limited to catalyst change and minor equipment changes like piping

or adaption in the product separation.

5. HYDRODEWAXING & MILD HYDROCRACKING

A combination of Hydrodewaxing with Mild Hydrocracking is of particular interest to refineries having noconversion processes like FCC or Hydrocracking. Feedstocks being used in these cases are heavy gasoils and vacuum gas oils that normally are sold as low cost fuel oil. A dewaxing function integrated into amild hydrocracker not only provides conversion in order to shift the whole boiling point curve towards lowerboiling components, but considerably increases the fractions to be used as low cloud point transport fuelssuch as diesel and kerosene. In all, the tremendous dewaxing power of the HYDEX catalyst along with theconversion capabilities of a MHC catalyst, can yield a convincing result in terms of a shift towards morevaluable products.

6. HYDRODEWAXING & DESULPHURIZATION & DEAROMATIZATION To fulfil strongest 2005+ requirements for diesel, apart from regional requirements in cold-flow-properties,mainly the aromatics have to be saturated. This process step of dearomatization is improving also T95



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boiling point, specific gravity and cetane in addition. Due to manifold benefits of our diesel rangehydroprocessing catalysts portfolio a unique and simple process scheme can be found (Figure 3). In a firststage HDS & HDX catalysts can be implemented into an existing reactor obtaining best results indesulphurization & cold-flow properties. Downstream a hot-flash separator the dearomatization reactor willensure that all diesel requirements can be fulfilled: such as deep HDS, deep HDAr, complete PNA-saturation, cetane enhancement and SG- & T95- improvements.

Make-up Hydrogen

Recycle Hydrogen

Gas Oil Blendor Diesel Fuel

High QualityDiesel Fuel

Gasoline

Product

LPG/Fuel Gas

Hydrogen

H2S + NH 3 + H 2

Amine Unit

HDS/HDX/MHC

DeepHDAr

Figure 3 - Flow Scheme for combined processing HDX & HDS & HDAr

Feedstock Product EU: 2005

Type LCO „2005“-Diesel „Diesel-Spec.“Density. [kg/m³] 869 825 825 – 845Cetane Number [#] 43 54 53 – 58

IBP/FBP [°C] 171/353 150/335 T95 < 340-350CP/PP/CFPP [°C] --- < - 15 to - 55 < - 15 to - 55Flashpoint [°C] 95 > 70 > 60

Sulphur [ppmwt.] 400 < 10 < 50Total Nitrogen [ppmwt.] 127 < 0.1 ---Total Aromatics [%wt.] 42.5 < 4 ---

PNA [%wt.] 15 < 0.1 < 1 – 8

Table 3 - Diesel Fuel Product obtained via HDX/HDS & HDAr processing

The above table 3 reflects the concept on the capability of the before discussed process scheme. It isobvious that all figures that are under discussion for the reformulation of diesel for the year 2005 can beachieved. For the year 2000+ diesel specifications there are even less constraints: sulphur, PNA-content,cetane number and T95 distillation point. An investment into such unit scheme guarantees profitabilityfrom SOR to EOR - even today. Of course, it is of utmost importance to introduce modern catalystsolutions into such scheme. Today, there is already a wide range of such middle distillate hydroprocessingcatalysts being available. Modern generations of middle distillate catalysts are as follows:



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"#HDS C20-6-01 TRX Sulphur down to less than 200 ppm"#Deep HDS C20-6-05 TRX Sulphur down to less than 50 ppm"#HDT C20-7 Series Broad Range Saturation & Stabilization"#MHC T-4542 Conversation with severity 10 – 60 %"#HDX HYDEX-Family PP/CP/CFPP down to less than – 60 °C"#

HDAr ASAT Series Deep HDS, Deep HDAr, complete HDN,T95- & SG Decrease, High Cetane Boost(for feedstock with up to 1000 ppm sulphur)

As today it is not possible anymore to achieve high quality fuel products without operating both moderncatalysts and tailored optimised technology schemes. Flexibility in process configuration and availability ofa wide range of modern catalysts afford optimal designs to achieve the desired process and productobjectives – for the profit to the refiners.

7. CONCLUSIONS

Hydroprocessing plays an increasingly important role in oil refining and is the key for production of cleantransportation fuels. As on a world-wide basis with the fuels specifications are becoming more restrictive

the total hydroprocessing capacity installed is becoming more importance and accordingly is increasingcontinuously. The key of each refining process is the catalyst – beside the technology being used.Therefore, it is most important for the refiner to chose he utmost optimum catalyst and modern technologyto ensure profitability from right of SOR.

It has been demonstrated that catalytic hydrodewaxing with a robust and sulphur tolerant zeolite catalystlike HYDEX-G is an extremely versatile tool to upgrade middle distillates and improve refinery margins.Apart from stand-alone dewaxing, the catalyst can be used for a great variety of integrated systemscomprising its combination with hydrotreating, mild hydrocracking and hydrocracking catalysts in a singlereactor. This technology is particularly suited for retrofits. For all types of applications, the degree of coldflow improvement is mainly determined by the operating temperature, hydrogen supply and feedstockproperties (n-paraffin content).

The main features determining the superior overall economy of integrated dewaxing in hydroprocessingunits are as follows:⇒ Meeting all today’s and future distillate fuels specifications.⇒ Use of heavy cuts (LVGO) for distillate fuels production.⇒ Additional margins from converting paraffinic fractions to Gasoline/LPG.⇒ Direct production of low CP/PP winter/arctic Diesel Fuel without blending.⇒ Considerable savings by replacement of CFPP improvers;⇒ Upgrading of distillates into high quality transportation fuels with various process options provide new

solutions to refiners: “HDX” ! “Deep HDS” ! “HDAr” ! “MHC/HC”.⇒ Generally, short payback times (2-12 months on average) are equivalent to best refining economics.

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Data SudChemie 7