ID - A1655

Hydrocracking – Advances in catalyst systems, Hydrocracking catalyst TK-939 D-selTM Anuj Seth, Peter Nymann

Haldor Topsoe International A/S, India Liaison Office, 2nd Floor, Elegance Tower, Plot No.8 Jasola district

center, New Delhi-110025

Presenting author, Email: anse@topsoe.in

Abstract

Today the refining industry’s key challenges concern upgrading technologies and revamping of existing

refineries to produce products complying with new stringent environmental regulations. Investments in

clean fuel production facilities have been prominent in the investment portfolio of many refineries and at

the same time, refiners are pressed to demonstrate competitive rates of return on their total capital

expenditure. The main focus is on developing technologies for processing of heavier oil slates like

heavy/light vacuum gas oils and heavy residues while maximizing middle distillate production. One such

route is hydrocracking by hydrogen addition and Topsoe has invested years of fundamental research to

develop catalyst systems, which can further increase the yield of middle distillates using this route. This

paper covers the performance improvement demonstrated in commercial units using Topsoe’s latest

generation hydrocracking catalyst TK-939 D-selTM. It illustrates how Topsoe’s extensive R&D capabilities

and experience from commercial units processing vacuum gas oils has materialized in the development of

a hydrocracking catalyst with optimized cracking and hydrogenation function. Topsoe’s hydrocracking

catalysts are currently installed & running in 27 units around the world used for production of high quality

middle distillates.

Introduction

There are several hydrocracking process flow schemes which can meet a refinery’s need & process

objectives with a basic scheme consisting of a typical two reactor design with a pretreating reactor and a

hydrocracking reactor in series. A schematic is shown in Figure 1. Vacuum gas oil (VGO) conversion to

products is conducted in two steps. The first reactor performs pretreat function in the top/ middle beds,

followed by hydrocracking to moderate conversion (40–60%) in the consecutive reactor/ beds. Mostly

hydrocrackers are provided with a guard bed consisting of inert material on top followed by de-metallization

catalyst before the high activity pretreating catalyst. The pre-treatment stage in hydrocracker unit has

primary objective of removing organic nitrogen, particularly basic nitrogen compounds, and to saturate

aromatics in the feed. Nitrogen compounds have a significantly negative impact on the activity of the

hydrocracking catalyst and, consequently on the performance of the hydrocracker. Typically, the nitrogen

levels are brought down to 15-20 ppmw in the outlet of the pre-treatment reactor. The final reactor effluent

from the hydrocracking reactor is sent to a fractionator. The fractionator bottoms may be sent to a second

stage (if existing), where a full or partial conversion is achieved or can be routed as the unconverted oil

(UCO) from the unit, which can be sent to a downstream FCC or a Lube manufacturing unit.

Graded bed

Hydrocracking

Pretreatment

Figure.1

Commercial unit comparison between TK-939 D-selTM & TK-931

A European refiner (Refinery-1) used TK-931 in its hydrocracker unit where they focused primarily on VI of

the unconverted oil. The client was satisfied with the performance however due to certain changes they did

not need high VI of the UCO in the next cycle and they requested Topsoe to provide a catalyst with high

middle distillate yield selectivity. Therefore, Topsoe proposed TK-939 D-sel™ instead of TK-931 for the

next cycle. A comparison of the performance of TK-939 D-sel to Topsoe’s TK-931 which has the same

activity indicates that the D-sel™ series offers better middle distillate selectivity with lower levels of

gaseous by-products and improves the properties of the unconverted oil products. When applied in

hydrocracker services in combination with high activity Topsoe pretreatment, such as TK-609 HyBRIM the

demonstrated higher yield of mid-distillates as shown in figure 2. The feed characteristics were as

mentioned in table-1.

Figure.2

Feedstock type LVGO / Visbreaker

HVGO Operating conditions

SG/API 0.906/24.7 LHSV PT, hr-1 1.7

Final boiling point,

°C/°F 548/1018 LHSV HC, hr-1 1.4

S, wt % 0.7 Inlet pressure, bar/psig 145/2100

N, wt ppm 1000

Product properties Diesel S, wt ppm <10

UCO S, wt ppm <20 Diesel SG/API 0.845/36.0

Table-1

TK-939 D-sel™ achieves high diesel yield with even higher activity and at the same time improves the cold

flow properties of the diesel. Compared with the TK-931, the improvement in cloud point is at least 7 °C

more as shown in figure 3 below.

Figure.3

The new catalyst formulation technique enhances aromatics saturation capabilities and therefore improves

middle distillate yield and product quality while maintaining catalyst stability. This combination of properties

makes the catalyst especially suitable for converting high-boiling range feedstocks into high-quality middle

distillate products in once-through or full conversion hydrocracking units. Normalized weighted average

bed temperature (WABT) comparison can be seen in figure 3 for the same level of required conversion.

Figure.4

Commercial unit performances of TK-939 D-selTM

European refinery-1

This part elaborates the performance in detail for the European refinery-1 hydrocracker whose

performance comparison with TK-931 was shown in first part of this paper. The unit had a load of Topsoe’s

pretreatment catalyst TK-609 HyBRIMTM and hydrocracking catalyst TK-939 D-selTM installed in the unit

which started last year and has now completed more than one year of operation. The unit operates at a

hydrogen partial pressure of around 120 bar with an average HC LHSV of 0.98hr-1.

The hydrocracking unit consists of two reactors in series with inter-bed quenches. The first one is the

pretreater reactor R1 which has installed TK-609 HyBRIM™ and the second reactor, R2, is loaded with

TK-939 D-sel™ in three beds. The unit is also loaded with a comprehensive Topsoe grading system,

including our TK-10 and TK-26 Top Trap™ in the top of bed 1 of the PTR reactor in order to minimize the

amount of FeS, particles and scales to the bulk catalyst. The unit operates at a gross conversion of 80

wt%.

Figure.5

Figure.6

The pre-treatment stage in hydrocracker unit has primary objective of removing organic nitrogen,

particularly basic nitrogen compounds, and to saturate aromatics in the feed. Nitrogen compounds have a

significantly negative impact on the activity of the hydrocracking catalyst and, consequently on the

performance of the hydrocracker. Feed nitrogen content is displayed on figure 5, it can be seen that the

feed nitrogen content fluctuated by +/- 200 ppmw around the design normal feed (1600 wtppm), the blue

solid line in figure 5. This shows how much the variation occurred in feed while processing the VGO, which

is attributed to almost 10 different crude types processed by refinery. With Topsoe’s HyBRIMTM catalyst

TK-609 HyBRIM and TK-939 D-selTM, the unit demonstrated 40% higher activity for sulfur and nitrogen

removal while providing higher aromatic saturation and increased volume swell.

Figure.7

The HC catalyst installed in the above unit demonstrated exceptional stability and selectivity even when

feed properties changed to large extents throughout the cycle. In general the yields have been reached as

expected so far. It was worthwhile to note that most of the product properties were achieved as targeted

during the whole cycle till now and also demonstrated during the process guarantee test run (PGTR). The

middle distillates and UCO fractions maintained a sulfur content less than 5 wt ppm. The cetane index,

density, and cloud point of the diesel fraction were achieved as targeted.

European refinery-2

A second reference for Topsoe’s pretreatment catalyst TK-609 HyBRIMTM and hydrocracking catalyst TK-

939 D-selTM is also an European hydrocracker which started in November 2014 and completed more than

1 year of successful operation which is still running? The unit operates at an average HC LHSV of 1.43hr-1

at a hydrogen partial pressure of 90 bar. The unit consists of two reactors with two beds in each reactor.

The first reactor (R1) is loaded with TK-609 HyBRIM™ and the second reactor (R2) is loaded with TK-939

D-selTM. Comprehensive grading is installed on top of the first bed in the first reactor. The objective of the

unit is a 75 wt% conversion of the residue (Products>360°C TBP) to lighter products with a preference to

middle distillates (diesel + kerosene; 150-360°C, TBP).

It can be seen as per figures 7 & 8, that the unit ran better than expected performance while demonstrating

exceptional stability when looking at the normalized weighted average bed temperatures for the

hydrocracking catalyst TK-939 D-selTM. The middle distillate yields were as shown in figure 10.

Figure.8

Figure.9

Conclusion

A hydrocracker is one of the most profitable units in the refinery, partly due to the volume swell and partly

because it converts heavy feedstocks to lighter and more valuable products such as naphtha, kerosene

and diesel. The unconverted oil (UCO) may be used as feedstock for fluid catalytic cracking (FCC) units,

lube oil plants and ethylene plants. Any improvement in the hydrocracking unit operation significantly

improves the overall refinery economics. Topsoe’s maximum middle distillate TK-939 D-sel opens new

possibilities to increase conversion of heavy vaccum gas oil into valuable middle distillates due to its

higher hydrogenation and high selectivity. Topsoe’s three maximum middle distillate hydrocracking

catalyst series – the Red series for maximum hydrogenation, the Blue series for maximum cold-flow

properties of diesel, and the D-sel™ series for maximum diesel yields – combine, with our BRIM® and

HyBRIM™ pretreatment catalysts, to deliver unmatched performance and flexibility to provide maximum

middle distillate yields and higher refinery margins. The figure 11 below shows Topsoe’s hydrocracking

catalyst portfolio:

Figure.10

The D-sel™ series is Topsoe’s latest generation hydrocracking catalysts especially developed for

hydrocrackers where the primary objective is maximum middle distillate yield. They provide outstanding

yields of diesel, typically in the range of >4 vol % greater than similar catalysts available in the market for

the same hydrocracking segment. Currently, Topsoe’s D-sel™ series consists of the TK-939 D-sel™ and

TK-949 D-selTM and more products are in the pipeline.

In total Topsoe has more than 80 hydrocracking catalyst references worldwide till date. A profound

understanding of catalyst kinetics and hydrocracking processes enables Topsoe to provide hydrocracking

units that meet any market need – whether the requirement is maximum heavy naphtha yield, flexible

production of high-quality naphtha and diesel or customized seasonal variations in gasoline/diesel

production ratio.