Comparisons of Fcc Product Yields and Qualities Between Reactors Using Canadian Heavy Feeds

Fuel Processing Technology 86 (2005) 1335–1350

www.elsevier.com/locate/fuproc

Comparisons of FCC product yields and qualities

between reactors using Canadian heavy feeds

Siauw H. Nga,T, Adrian Humphriesb, Craig Fairbridgea, Yuxia Zhuc,

Chandra Khulbea, Thomas Y.R. Tsaid, Fuchen Dinge,

Jean-Pierre Charlandf, Sok Yuig

aNational Centre for Upgrading Technology, 1 Oil Patch Drive, Devon, Alberta, Canada T9G 1A8bAkzo Nobel Catalysts LLC., 2625 Bay Area Boulevard, Suite 250, Houston, TX 77058, USA

cResearch Institute of Petroleum Processing, 18 Xue Yuen Road, PO Box 914, Beijing 100083, ChinadNational Dong Hwa University, Hualien 974, Taiwan, ROC

eUniversity of Petroleum, Beijing 102249, ChinafCANMET Energy Technology Centre-Ottawa, 1 Haanel Drive, Ottawa, Ontario, Canada K1A 1M1

gSyncrude, Research Centre, 9421-17 Avenue, Edmonton, Alberta, Canada T6N 1H4

Accepted 1 January 2005

Abstract

This study describes the effects of two catalysts, an octane-barrel and a bottoms-cracking catalyst,

on the catalytic cracking of 10 oil-sands bitumen-derived feeds in fixed- and fluid-bed microactivity

test (MAT) units, an Advanced Cracking Evaluation (ACE) unit, and a continuous riser pilot unit.

This is part of a comprehensive study of the cracking behavior of Canadian vacuum gas oils. In

general, at an equivalent catalyst/oil ratio, conversions decreased in the order ACEN fixed-bed

MATN fluid-bed MAT among the batch reactors. Between a batch reactor and the continuous riser,

there existed a good correlation for a given product yield as well as for a given product quality, at a

specific conversion. For the oil-sands-derived vacuum gas oils, the bottoms-cracking catalyst

containing rare-earth-exchanged Y zeolite (REY) with a large-pore active matrix was more effective

than the catalyst containing the rare-earth-exchanged ultrastable Y (REUSY) and ZSM-5 zeolites

with an active matrix. The overall distribution of feed sulfur in cracked products, and the relationship

0378-3820/$ -

doi:10.1016/j.

T Correspon

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see front matter. D 2005 Elsevier B.V. All rights reserved.

fuproc.2005.01.020

ding author. Tel.: +1 780 987 8709; fax: +1 780 987 5349.

ress: [email protected] (S.H. Ng).

S.H. Ng et al. / Fuel Processing Technology 86 (2005) 1335–13501336

of the sulfur content of feed with that of light cycle oil (LCO), confirmed the findings reported in the

literature.

D 2005 Elsevier B.V. All rights reserved.

Keywords: FCC yields; Canadian heavy feeds; Oil-sands bitumen; Microactivity test (MAT) unit; Advanced

Cracking Evaluation (ACE) unit

1. Introduction

Canadian oil-sands bitumen is a mixture of immature and complex hydrocarbons rich in

chemical impurities (e.g., sulfur, nitrogen, nickel, and vanadium) and low in hydrogen-to-

carbon ratio (i.e., very aromatic). Canadian heavy crudes are delivered from western

provinces (mostly Alberta) to other regions, including the United States, through pipelines.

Because of the high viscosity, the bitumen can only be transported through pipelines after

being mixed with suitable diluents such as natural gas condensates and naphthas.

Alternatively, the bitumen can be upgraded to a light and bottomless synthetic crude oil

(SCO) that is of pipeline quality as far as the viscosity and contents of sediment and water

are concerned. Syncrude Canada Ltd. is the world’s largest oil-sands bitumen upgrader,

producing an SCO called bSyncrude Sweet BlendQ or bSSB.Q Over the years, Syncrude hasbeen striving for a better quality of SSB, with specific interest in the heavy gas oil (HGO) or

vacuum gas oil (VGO), which is usually used by refiners as a fluid catalytic cracking (FCC)

feed. In 1998, Syncrude evaluated 10 existing and potential VGOs in a riser pilot plant. Riser

results were reported previously [1]. With parts or all of the same feeds, a comprehensive

FCC program consisting of several series of microactivity (MAT) tests in fixed- and/or fluid-

bed reactors was conducted at the National Centre for Upgrading Technology (NCUT). The

objectives of the test program were threefold: (1) to provide guidance for the pilot plant

operation; (2) to compare cracking yields obtained from different reactor systems including

riser, MAT (with fixed- and fluid-bed reactors), and an Advanced Cracking Evaluation

(ACE) unit; [2] and (3) to develop analytical techniques for determination of aromatics,

sulfur, and nitrogen in MAT liquid product fractions and compare these values with those

obtained from the pilot plant. This paper focuses on objectives (2) and (3).

2. Experimental

The test program was composed of three studies, which are described below.

2.1. Study 1—establishing riser operating conditions and comparison of cracking

performances between riser and fixed-bed MAT

This study involved the following 10 feeds:

1. HCB—hydrocracker bottoms VGO

2. HT-VIR—hydrotreated virgin VGO

S.H. Ng et al. / Fuel Processing Technology 86 (2005) 1335–1350 1337

3. RZ—Rainbow Zama crude VGO

4. HT-LCF—hydrotreated LC-Finer VGO

5. HT-C—hydrotreated coker VGO

6. HT-DA—hydrotreated DA-BIT (see bfeed 10Q below)7. VIR—untreated virgin VGO

8. LCF—untreated LC-Finer VGO

9. DA-LCF—deasphalted oil VGO from LC-Finer resids

10. DA-BIT—deasphalted oil VGO from bitumen.

Table 1 summarizes the feed properties. Based on concentrations of gasoline precursors

[3], total nitrogen, and microcarbon residue (MCR), the feed qualities in terms of the

capacities to produce gasoline were ranked [4] in a descending order from feed 1 to feed

10, as shown above. More detailed characteristics and history of the feeds, and an

intensive discussion on feed properties, can be found elsewhere [1,4]. Table 2 gives the

properties of the equilibrium catalysts, HRO 610 (HRO) and catalyst A (CAT-A), used in

this program.

A fixed-bed MAT unit (Zeton Automat IV), equipped with collection systems for gas

and liquid products was used to crack the 10 feeds. For each feed, three runs were

conducted at 510 8C and one and two runs at 500 and 520 8C, respectively. However,some runs were repeated later. Since the reaction temperature range was rather small

(F10 8C at 510 8C), it was assumed that the temperature effect on MAT yields was

negligible and that one regression could be applied to the same set of data points obtained

at three different temperatures. The omission of the temperature effect can be justified by

the rather low sensitivity of the MAT yields to temperature in this study. This is shown in

Table 3, which illustrates that a decrease of 20 8C will cause less than 10% absolute

change in yield (relative to the yield at 520 8C and 5.5 C/O), except for dry gas due to its

small yield. Note that the majority of the MAT runs were performed at 510 8C. Thereactor was loaded with 4 g of CAT-A with 30 s catalyst contact time for all runs. Coke

deposited on the catalyst after cracking was determined by in situ combustion through the

use of a CO2 absorber. Some of the cracking characteristics in Study 1 have been

reported previously [4–7].

2.2. Study 2—comparison of cracking performances between fixed- and fluid-bed MAT

reactors and method development to characterize MAT liquid

Five feeds of various ranks (HCB, HT-C, HT-DA, VIR, and DA-BIT) were cracked

in the MAT unit using both fixed- and fluid-bed reactors at 510 8C and 30 s oil injection

time with 5 g of CAT-A. The fixed-bed version is based on ASTM D 5154, which is

more widely used by the catalyst industry, while the fluid-bed version is being

developed by ASTM. In this study, a specially designed liquid receiver with extra large

volume (300 mL) was used to collect over 99 wt.% of liquid products that were free of

contamination by wash solvents (e.g., CS2). Total liquid products (TLPs) from fixed-bed

runs involving HT-C and DA-BIT, and fluid bed runs involving HT-DA, were

characterized (without prior separation) for: (1) simulated distillation (ASTM 2887);

(2) hydrocarbon types of gasoline [PIONA analyzer, a specially configured gas

Table 1

Feedstock properties

Feed number 1 2 3 4 5 6 7 8 9 10

Feed name HCB HT-VIR RZ HT-LCF HT-C HT-DA VIR LCF DA-LCF DA-BIT

Density at 15 8C,g/ml

0.8643 0.9252 0.8988 0.9284 0.9511 0.9430 0.9712 0.9562 0.9642 0.9776

Hydrogen, wt.% 13.7 12.3 12.8 12.1 11.5 11.8 11.1 11.2 11.2 11.1

H/C atomic ratio 1.892 1.669 1.764 1.638 1.562 1.619 1.549 1.532 1.536 1.556

Total nitrogen,

wppm

0 460 800 1090 2150 2450 1930 3370 4020 3050

Total sulfur, wppm b10 981 9170 880 4290 7040 32,500 13,500 15,200 35,400

MCR, wt.% 0.04 0 0.08 0.02 0.50 2.61 0.33 0.24 3.40 5.37

Ni, wppm 0 0 0 0 0 4.1 0 0 4.5 11.6

V, wppm 0 0 0 0 0 6.8 0.1 0 8.1 25.0

Aromatic carbon,

%

4.4 17.6 14.6 20.2 24.7 20.9 25.4 30.1 28.8 24.4

Aniline point, 8C 99.8 74.2 89.4 71.8 63.6 81.0 50.8 58.0 65.8 62.8

Refractive index at

20 8C1.4747 1.5130 1.4967 1.5153 1.5323 1.5269 1.5397 1.5324 1.5370 1.5393

343 8C� by

simdist, wt.%

19.6 7.4 2.0 5.5 4.5 1.5 6.0 7.7 11.0 10.8

524 8C+ by

simdist, wt.%

1.4 1.3 2.5 1.2 8.3 36.9 2.0 1.4 25.0 38.1

Hydrocarbon type by MSD, wt.%

Saturates 90.1 46.8 61.0 45.7 34.4 35.4 28.7 35.5 29.1 23.0

Paraffins 21.7 4.1 22.8 7.4 4.7 5.0 1.8 5.2 4.3 1.4

Cycloparaffins 68.4 42.7 38.2 38.3 29.7 30.4 26.9 30.3 24.8 21.6

Aromatics 9.3 52.3 36.1 52.3 61.8 57.5 65.6 58.4 59.1 61.8

Mono- 6.9 29.1 16.6 27.6 29.5 29.5 22.5 20.6 26.3 24.7

Di- 1.2 10.5 7.7 11.9 13.6 12.7 14.4 13.6 13.1 14.0

Tri- 0.3 3.9 3.7 4.9 6.3 5.4 7.2 7.3 6.0 5.7

Tetra- and greater 0.5 4.0 3.4 3.7 6.1 5.1 8.0 8.4 6.6 6.3

Aromatic sulfur 0.3 2.8 3.7 2.6 4.2 3.4 10.7 6.8 5.4 9.1

2-Ring

compounds

0.2 0.9 1.5 0.7 0.7 1.2 5.0 2.3 1.9 4.5

3-Ring

compounds

0.1 1.7 1.8 1.7 3.0 2.0 4.6 3.9 3.1 3.9

4-Ring

compounds

0.0 0.2 0.4 0.2 0.5 0.2 1.1 0.6 0.4 0.7

unidentified 0.1 2.0 1.0 1.6 2.1 1.4 2.8 1.7 1.7 2.0

Polar compounds 0.7 0.9 2.9 2.0 3.8 7.1 5.7 6.1 11.8 15.2

Gasoline precursorsa 97.0 75.9 77.6 73.3 63.9 64.9 51.2 56.1 55.4 47.7

a Saturates+monoaromatics.


chromatograph (GC) with a prefractionator]; and (3) boiling-point distributions of

aromatics (GC with a mass-selective detector—GC-MSD), nitrogen (GC with an Antek

nitrogen chemiluminescence detector—GC-NCD), and sulfur (GC with Sievers sulfur

chemiluminescence detector—GC-SCD). Partial results from Study 2 have been orally

presented [8,9] and published [9–11].

Table 2

Equilibrium catalyst properties

Catalyst HRO 610 CAT-A

X-ray diffraction

Unit cell size (fresh), 2 24.66 n/a

Unit cell size (equilibrium), 2 24.35 24.28

Zeolite content, wt.% n/a 13

Nitrogen adsorption–desorption

Total surface area, m2/g 148 150

Zeolite surface area, m2/g 65 100

Matrix surface area, m2/g 83 50

Zeolite/matrix (Z/M) 0.78 2.00

Micropore volume, mL/g n/a 0.05

Zeolite content, wt.% 10.6 15.6

Hg porosimetry

Pore volume, mL/g 0.37 0.22

Pore area, m2/g 101 61

Average pore diameter, 2 147 109

Water absorption

Pore volume, mL/g 0.45 0.31

Average particle size, Am 67.9 79.5

SiO2, wt.% n/a 55.7

Al2O3, wt.% 49.7 39.7

RE2O3, wt.% (on catalyst) 1.85 1.21

RE2O3, wt.% (on zeolite) 17.5 7.8

Na2O, wt.% 0.31 0.19

TiO2, wt.% n/a 1.62

Fe2O3, wt.% 0.66 0.67

Ni, wppm 242 291

V, wppm 434 314


2.3. Study 3—catalyst effects on product yields and qualities

Three feeds of special interests (HT-C, HT-DA, and VIR) were cracked at 30 s catalyst

contact time with 7 g of equilibrium catalysts (CAT-A and HRO) at 510 8C (530 8C for

HT-DA) in the MAT unit using the fluid-bed reactor. TLPs collected with the improved

liquid receiver were characterized as in Study 2. In addition, the three feeds were also

Table 3

Sensitivity of fixed-bed MAT yields to temperature

Yield at 520 8C and 5.5 C/O

(average of 10 feeds), wt.%

Absolute differencea relative to yield at

520 8C and 5.5 C/O (average of 10 feeds), %

Dry gas 2.56 15.9

LPG 13.5 9.5

Gasoline 44.1 1.1

LCO 18.4 6.4

HCO 16.0 6.4

Coke 5.53 5.1

Conversion 65.7 2.2

a Based on yields at 500 and 520 8C in Study 1 using CAT-A.


cracked with the same two catalysts in the ACE unit [2]. Recently, the ACE unit has

gained popularity as a tool for laboratory FCC studies.

HRO is a large-pore catalyst developed by Akzo Nobel Catalysts LLC based on a special

catalyst assembly technology to give a high Akzo accessibility index [12], which measures

the relative mass transfer rates of hydrocarbons into and out of the catalyst pores (i.e., the

adsorption and desorption rates of hydrocarbons). Table 2 shows that, compared with CAT-

A, HRO was characterized by: (1) higher rare-earth content on zeolite (17.5 vs. 7.8 wt.% for

CAT-A) that increased its stability and activity; (2) lower zeolite content and lower zeolite

surface area, but higher matrix surface area with a much lower zeolite/matrix (Z/M) ratio

(0.78 vs. 2.00 for CAT-A); and (3) larger matrix opening (147 vs. 109 2 average pore

diameter for CAT-A) that provided greater access to heavy molecules that needed to be pre-

cracked. These properties suggested that HRO was a bottoms-cracking catalyst containing

rare-earth-exchanged Y zeolite (REY) while CAT-A was an octane-barrel catalyst

containing rare-earth ultra-stable Y zeolite (REUSY) mixed with a small amount of

ZSM-5 for octane enhancement. Partial results from Study 3 have been reported [5,13,14].

3. Results and discussion

3.1. Comparison of product yields between MAT unit and riser reactor

In spite of fundamental differences in reactor design and operations, the MAT unit can

be a useful tool to predict riser performance. In Study 1, MAT data at 55, 65, 70, and 81

wt.% conversion were plotted against their riser counterparts reported previously [1]. Fig. 1

R2 = 0.971

R2 = 0.946

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10

RISER DRY GAS OR COKE YIELD, wt %

MA

T D

RY

GA

S O

R C

OK

E Y

IELD

, wt %

HCB

RZ

HT-VIR

HT-LCF

HT-DA

HT-C

VIR

LCF

DA-LCF

DA-BIT

1:1 line

Fig. 1. Correlation of MAT dry gas (open symbols) or coke (closed symbols) yield with their corresponding riser

counterpart at the same conversion (from Study 1 involving fixed-bed MAT and CAT-A).


depicts the linear relationship for dry gas or coke yield between riser and fixed-bed MAT

with R2 values greater than 0.946. The similar plot for gasoline or heavy cycle oil (HCO)

gave R2N0.920 (Fig. 2). The correlation of MAT liquefied petroleum gas (LPG) or light

cycle oil (LCO) yield with their respective riser counterpart was less impressive, with R2

value being ~0.650. The imperfect linear correlations have been explained before [6,7]. In

all cases, the trend lines, representing the data points, did not overlap the 1:1 line due to the

differences in unit operation and design. But from the linear relationships, one can

calculate the individual predicted riser yields from their corresponding MAT yields. Fig. 3

shows a good linear relationship, with 0.992 R2 value, for all products between the

predicted and actual riser yields. Similarly, a good correlation was also observed in Study 3

involving fluid-bed MAT and riser for feeds HT-C, HT-DA, and VIR [13].

3.2. Cracking performances in MAT and ACE units

Fig. 4 shows the increase in conversion with catalyst/oil ratio (C/O) for five feeds

(HCB, HT-C, HT-DA, VIR, and DA-BIT) cracked in both fluid- and fixed-bed MAT units

(Study 2), and two feeds (HT-C and VIR) cracked in the ACE unit (Study 3). Both studies

involved CAT-A at 510 8C. At a given C/O ratio, fixed-bed MAT (from which the results

represented by thick trendlines) gave, in general, higher conversion than fluid-bed MAT

(from which the results represented by thin trendlines) for all feeds because of the more

intimate contact between oil molecules and catalyst particles within a reaction period in a

fixed-bed reactor. However, at about or below 4 C/O ratio, fixed-bed MAT gave lower

conversion for the three feeds (HCB, HT-C and VIR) that were low in microcarbon residue

(MCR). This indicated that the catalyst poisoning (by coke) was less severe in a fluidized

R2 = 0.961

R2 = 0.920

5

10

15

20

25

30

35

40

45

50

55

60

65

5 10 15 20 25 30 35 40 45 50 55 60 65

RISER GASOLINE OR HCO YIELD, wt %

MA

T G

AS

OLI

NE

OR

HC

O Y

IELD

, wt %

HCB

HT-VIR

RZ

HT-LCF

HT-C

HT-DA

VIR

LCF

DA-LCF

DA-BIT

1:1 line

Fig. 2. Correlation of MAT gasoline (closed symbols) or HCO (open symbols) yield with their corresponding riser

counterpart at the same conversion (from Study 1 involving fixed-bed MAT and CAT-A).

R2 = 0.992

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70ACTUAL RISER YIELD, wt %

PR

ED

ICT

ED

RIS

ER

YIE

LD, w

t %

DRY GAS

LPG

GASOLINE

LCO

HCO

COKE

trend line and 1:1 line

predicted riser yield = a x MAT yield + b

all feed:

dry gasLPGgasolineLCOHCOcoke

1.14 0.75 1.08 0.75 1.08 1.23

-0.30 3.34 -5.60 5.83 -2.86 0.78

0.946 0.651 0.961 0.655 0.920 0.971

a b R2

Fig. 3. Correlation of predicted riser yield with actual riser yield at the same conversion (from Study 1 involving

fixed-bed MAT and CAT-A.

302 4 6 8 10 12 14

40

50

60

70

80

90

C/O RATIO, g/g

CO

NV

ER

SIO

N, w

t%

HCB (Fluid)

HCB (Fixed)

HT-C (Fluid)

HT-C (Fixed)

HT-C (ACE)

HT-DA (Fluid)

HT-DA (Fixed)

VIR (Fluid)

VIR (Fixed)

VIR (ACE)

DA-BIT (Fluid)

DA-BIT (Fixed)

VIR (Fluid)

VIR (Fixed)

HCB (Fixed)HCB (Fixed)

HCB (Fluid)

HT-DA (Fixed)

HT-DA (Fluid)

HT-C (Fixed)

HT-C (Fluid)

DA-BIT (Fixed)

DA-BIT (Fluid)

VIR (ACE)

HT-C (ACE)

Fig. 4. Variation of conversion with C/O ratio for feeds cracked in MAT (Study 2) and ACE (Study 3) reactors

with CAT-A at 510 8C.



bed with even distribution of poisons than in a fixed bed with accumulation of poisons at

the top of the bed. For the two high-MCR feeds (HT-DA and DA-BIT), the reduced

poisoning effect on the fluid bed was masked. Fig. 4 also shows that, at the same C/O

ratio, ACE (from which the results represented by trendlines of medium thickness) gave

the highest conversion for the same feed, with the conversion curves parallel to their

counterparts from the fixed-bed MAT. In any reactor, the order of conversion corresponded

with that of the feed rank [4], except for the two deasphalted oils (HT-DA and DA-BIT)

with high MCR and sulfur.

Table 4 shows a yield comparison at 65 wt.% conversion among the three reactors for

HT-C and VIR. In general, for the same feed, ACE gave the highest yields of converted

products (except coke) and HCO, and the lowest yields of coke and LCO. Both fixed- and

fluid-bed MATs had much higher coke yields than ACE due partially to some imperfect

conditions of MAT reactors in the early stage of operations. It was found later that after

cracking, some minute but consistent amount of heavy product (HCO) was condensed and

not recovered at the bcoldQ spot near the exit of the reactor. This was picked up later as

bcokeQ at a higher reactor temperature (600 8C) during catalyst in situ regeneration.

Another reason for coke differences was that ACE was operated at a shorter catalyst

contact time (b15 s) than MATs, resulting in lower coke deposit on catalyst according to

the Voorhies equation [15]. Between the two MAT units, the fixed-bed reactor gave higher

yields in dry gas and LCO, slightly higher or equivalent yield in coke, lower yields in

gasoline and HCO, and equivalent yield in LPG. In general, relative to the fixed-bed MAT

yields, the corresponding fluid-bed MAT yields and the yields of LPG and gasoline from

ACE could be maintained within 15% relative.

3.3. Comparison of product qualities between MAT unit and riser reactor

Table 5 shows that in Study 2, the product analyses (S, N, and aromatics) of HT-C, HT-

DA, and DA-BIT from the MAT compared reasonably well, with a few exceptions, with

their individual counterparts from the riser at 55 and 65 wt.% conversion. Nitrogen in the

LCO fractions from the MAT was consistently lower by about 50% for the three feeds,

possibly caused by the calibration problem in the analysis of MAT samples.

Table 4

Comparison of yields (wt.%) at 65 wt.% conversion among reactors using CAT-A

Reactor Dry gas LPG Gasoline LCO HCO Coke

HT-C VIR HT-C VIR HT-C VIR HT-C VIR HT-C VIR HT-C VIR

MAT (fixed bed)a 2.2 4.3 14.1 13.8 41.3 37.7 21.3 22.2 13.7 12.8 7.2 8.8

MAT (fluid bed)a 1.9 3.1 14.2 13.6 42.0 38.7 19.3 21.7 15.7 14.2 7.0 8.8

ACEb 2.8 4.7 15.7 14.5 43.9 43.1 16.7 18.0 18.8 17.0 2.7 2.8

Bias 1c, % �13.8 �27.7 0.4 �1.5 1.6 2.5 �9.3 �2.3 14.6 10.6 �3.9 �0.2

Bias 2d, % 31.2 9.8 11.0 5.1 6.3 14.2 �21.5 �19.0 37.5 33.0 �62.7 �68.7

a Study 2.b Study 3.c Bias 1 (%)=[MAT (fluid bed)�MAT (fixed bed)] /MAT (fixed bed)�100.d Bias 2 (%)=[ACE�MAT (fixed bed)] /MAT (fixed bed)�100.

Table 5

Comparison of product qualities between MAT unit and riser reactor using CAT-A

Product Gasoline LCO HCO

Analyses S, wppm S, wt.% N, wppm Aromatics, wt.% S, wt.% N, wppm

Reactor MAT Riser MAT Riser MAT Riser MAT Riser MAT Riser MAT Riser

55 wt.% conversiona

HT-C 72 53 0.55 0.41 540 1110 88.0 88.0 1.16 1.09 3500 3400

HT-DA 632 570 0.66 0.63 461 1000 79.3 78.9 0.92 0.96 3210 2990

DA-BIT 6971 6600 3.67 3.10 541 900 84.7 84.7 4.81 4.06 3815 2980

65 wt.% conversiona

HT-C 50 64 0.50 0.49 520 1040 90.1 94.2 1.70 1.22 4000 3100

HT-DA 646 410 0.75 0.76 333 1060 83.8 89.2 1.15 1.14 3621 3530

55 wt.% conversionb

HT-C 70 53 0.42 0.41 1437 1110 0.76 1.09 4238 3400

HT-DA 710 570 0.62 0.63 1750 1000 0.71 0.96 4286 2990

VIR 4600 5500 3.28 3.37 916 750 3.57 3.92 3399 2500

65 wt.% conversionb

HT-C 50 64 0.44 0.49 1282 1040 0.81 1.22 4378 3100

HT-DA 610 410 0.65 0.76 1603 1060 0.85 1.14 4639 3530

VIR 3900 4900 3.43 4.10 839 760 3.92 4.15 3517 2000

a Study 2 (fixed-bed MAT for HT-C and DA-BIT but fluid-bed MAT for HT-DA).b Study 3 (fluid-bed MAT for all feeds).


A good agreement in product analyses between the fluid-bed MAT and the riser was

also obtained for HT-C, HT-DA, and VIR in Study 3 [14] (Table 5).

3.4. Variation of product qualities with conversion

With the low cost and simple operation of the MAT unit, one could afford to perform a

detailed study that might reveal useful information. Figs. 5–8 show the effects of

conversion on product qualities for feed DA-BIT, cracked in a fixed-bed MAT reactor in

Study 2. The following summarizes the interesting observations:

! The enrichment of aromatics in the three fractions of DA-BIT liquid product as

conversion increased (Fig. 5): At a given conversion, LCO always gave the highest

aromatics concentration due to the more stable nature of its precursors (mostly

diaromatics) compared with those of HCO, which might form coke.

! The unique concave sulfur curves for DA-BIT (much less pronounced for HT-DA), a

nonhydrotreated feed, in a sulfur vs. conversion plot (Fig. 6): This observation indicates

the balances, in three liquid fractions, between the sulfur removal (by decomposition of

sulfur species, to yield H2S, or molecular reduction, or coke formation) and the sulfur

augmentation (through enrichment of sulfur-containing aromatics or molecular

reduction).

2000

4000

6000

8000

10000

12000

14000

16000

56 58 60 62 64 66 68

MAT CONVERSION, wt %

SU

LPH

UR

, wpp

m

15000

20000

25000

30000

35000

40000

45000

50000

Gasoline

LCO

HCO

Fig. 6. Effect of conversion on sulfur concentration of product cut for DA-BIT cracked in fixed-bed MAT with

CAT-A at 510 8C (Study 2).

55

60

65

70

75

80

85

90

95

56 58 60 62 64 66 68


AR

OM

AT

ICS

, wt %

Gasoline

LCO

HCO

Fig. 5. Effect of conversion on aromatics concentration of product cut for DA-BIT cracked in fixed-bed MATwith




! Similar balances among the reactions involving nitrogen compounds in the three liquid

fractions of DA-BIT (Fig. 7).

! The increase in density of DA-BIT gasoline at higher conversion, showing the gradual

depletion of crackable saturates and unsaturates (olefins) in this fraction (Fig. 8).

3.5. Effect of catalyst pore size on product yields

Modern commercial FCC catalysts are formulated with 10–50 wt.% of highly active

zeolites [16] containing a maximum pore size of about 7.5 2 [17]. However, in

bitumen feeds, some heavy hydrocarbon species with boiling points 850 8F+ (454

8C+) have kinetic diameters ranging from 10 to over 100 2 [17]. These molecules are

precluded, for steric reasons, from entering the zeolite cage for cracking. Thus, modern

design of FCC catalysts requires a wide-pore non-zeolitic component, a matrix with

mesopores (30–500 2) or macropores (500 2+), for pre-cracking the large oil

molecules.

In Study 3, a specially designed catalyst, Akzo Nobel HRO, with high accessibility to

large hydrocarbon molecules demonstrated the important role of the large-pore catalyst in

cracking Canadian bitumen feeds. Here, HT-C and VIR were cracked at 510 8C, and HT-

DAwas cracked at 530 8C, using both catalysts HRO and CAT-A. Table 6 shows that at 65

wt.% conversion, compared with CAT-A, HRO significantly increased the yield of liquid

fuels (gasoline+LCO) by 7.1–9.5 wt.% and decreased HCO yield by 3.0–3.6 wt.%. Dry

0

100

200

300

400

500

600

700

56 58 60 62 64 66 68


NIT

RO

GE

N, w

ppm

500

1000

1500

2000

2500

3000

3500

4000

Gasoline

LCO

HCO

Fig. 7. Effect of conversion on nitrogen concentration of product cut for DA-BIT cracked in fixed-bed MAT with


0.810

0.815

0.820

0.825

55 57 59 61 63 65 67 69


DE

NS

ITY

@ 1

5.6

°C, g

/mL

Fig. 8. Effect of conversion on gasoline density for DA-BIT cracked in fixed-bed MAT with CAT-A at 510 8C(Study 2).


gas yield was also decreased by 0.3–0.6 wt.%, and coke yield by 0.7–1.3 wt.%. The

corresponding LPG yield, however, was lower by 2.6–3.9 wt.%.

3.6. Feed sulfur distribution in FCC products

The amounts of sulfur in H2S and coke are usually difficult to determine accurately due

to (1) the abundance of olefins in product gas, which may react with H2S, and (2) the

restricted small amounts of samples (i.e., spent catalysts with less than 1 wt.% coke)

Table 6

Catalyst effect on product yield at 65 wt.% conversiona

Feed HT-C HT-DA VIR

Catalyst HRO CAT-A Difference HRO CAT-A Difference HRO CAT-A Difference

C/O ratio 8.92 10.84 �1.92 3.82 6.35 �2.53 9.07 12.66 �3.59

Dry gas, wt.% 1.77 2.11 �0.34 1.82 2.44 �0.63 2.84 3.14 �0.30

LPG, wt.% 9.4 12.4 �3.1 9.3 13.1 �3.9 9.4 12.1 �2.6

Gasoline, wt.% 46.5 42.5 4.0 48.2 42.4 5.8 45.3 41.2 4.1

LCO, wt.% 21.5 18.5 3.1 21.3 17.6 3.6 23.1 20.0 3.0

Gasoline+LCO, wt.% 68.0 60.9 7.1 69.5 60.0 9.5 68.3 61.2 7.1

HCO, wt.% 13.5 16.5 �3.1 13.7 17.4 �3.6 11.9 14.9 �3.0

Coke, wt.% 7.28 7.97 �0.69 5.82 7.10 �1.28 7.43 8.61 �1.18

Delta coke, wt.% 0.82 0.71 0.11 1.45 1.13 0.32 0.83 0.68 0.15

a Study 3 (fluid-bed MAT for all feeds).

Table 7

Feed sulfur distributions in FCC products for virgin VGOa (wt.%)

Catalyst Conversion Coke H2S Gasoline LCO HCO

HRO 610 60 5.0 45.3 5.0 23.7 21.0

CAT-A 60 5.0 47.7 4.4 20.9 22.0

HRO 610 65 5.0 48.9 4.9 24.0 17.2

CAT-A 65 5.0 51.5 4.3 21.3 17.9

a Study 3 (fluid-bed MAT for all feeds).


required by modern analytical instruments for sulfur analysis. High sulfur in coke was

found for hydrotreated feeds by Huling et al. [18]. Thus, in Study 3, uncertainty existed in

estimating the feed sulfur distribution in coke for HT-C and HT-DA, but it was safe to

assume 5 wt.% for VIR, a nonhydrotreated feed [19]. The feed sulfur distributed in

gasoline, LCO, and HCO could be readily calculated, while the balance was counted as the

sulfur in H2S. Table 7 shows the feed sulfur distributions at 60 and 65 wt.% conversion,

respectively. In general, the results agreed with the findings reported in the literature [19].

3.7. LCO sulfur concentrations

Letzsch and Ashton [20] reported that, as a rule of thumb, LCO has approximately the

same sulfur content as the feed for many FCC units. This was also observed in our work,

regardless of the cracking units and catalysts used (Table 8).

Table 8

Sulfur concentration in LCO (wt.%)

Feed name HCB HT-VIR RZ HT-LCF HT-C HT-DA VIR LCF DA-LCF DA-BIT

Feed sulfur, wt.% b0.001 0.10 0.92 0.09 0.43 0.70 3.25 1.35 1.52 3.54

MAT at 55 wt.%

concentrationaCAT-A 0.55 0.66 3.67

MAT at 65 wt.%

concentrationaCAT-A 0.50 0.75

Averagea 0.53 0.71 3.67

MAT at 65 wt.%

concentrationbCAT-A 0.44 0.66 3.43

MAT at 65 wt.%

concentrationbHRO 0.57 0.73 3.46

Averageb 0.51 0.70 3.45

Riser at 55 wt.%

concentration

CAT-A 0.41 0.63 3.37 1.54 1.42 3.10

Riser at 65 wt.%

concentration

CAT-A 0.13 0.87 0.10 0.49 0.76 4.10

Riser at 70 wt.%

concentration

CAT-A 0.13 1.03 0.10

Riser at 81 wt.%

concentration

CAT-A b0.01

Average b0.01 0.13 0.95 0.10 0.45 0.70 3.74 1.54 1.42 3.10

a Study 2 (fixed-bed MAT for HT-C and DA-BIT, but fluid-bed MAT for HT-DA).b Study 3 (fluid-bed MAT for all feeds).


4. Conclusions

! MATyields, irrespective of reactor types and catalysts used, could be correlated with the

corresponding riser pilot plant results, although their absolute values could be different.

! At a given C/O ratio, fixed-bed MAT gave higher conversion than fluid-bed MAT for

all feeds except at low C/O for the low-MCR feeds. Compared with the MAT, ACE

gave the highest conversion for the same feed. In any reactor, the order of conversion

corresponded with that of the feed rank except for the deasphalted oils. At a given

conversion, correlations existed among the fixed- and fluid-bed MAT units and the

ACE for each product yield.

! In general, at the same conversion and for the same feed, contents of aromatics, sulfur,

and nitrogen of each product fraction from the MAT were comparable in magnitude

with their individual counterparts from the riser. Aromatics concentration increased

with conversion in all three liquid product fractions, among which LCO had the highest

aromatics concentration. The observed changes in sulfur and nitrogen with conversion

were the net results from the reaction balances involving sulfur- and nitrogen-

containing species, respectively.

! To achieve higher yields of valuable distillates when cracking oil-sands-derived VGOs,

HRO–a bottoms-cracking catalyst containing REY zeolite and a large-pore active

matrix–was more suitable than CAT-A, an octane-barrel catalyst containing REUSY/

ZSM-5 zeolites and an active matrix.

! The feed sulfur distribution in cracked products for VIR feed agreed well with those

reported in the literature.

! Regardless of the cracking units and catalysts used, the LCO produced had

approximately the same sulfur content as the feed.

Acknowledgments

The authors wish to thank the analytical laboratory of the National Centre for

Upgrading Technology (NCUT) for its technical support. Partial funding for this research

has been provided by Syncrude Research, the Canadian Program for Energy Research and

Development (PERD), the Alberta Research Council, and the Alberta Energy Research

Institute.

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Comparisons of Fcc Product Yields and Qualities Between Reactors Using Canadian Heavy Feeds

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