DOI: 10.3303/CET24114100 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Paper Received: 27 April 2024; Revised: 8 August 2024; Accepted: 17 November 2024 
Please cite this article as: Liu X., He L., 2024, The Development Review on Light Cycle Oil Upgrading Technology to Fuels and Petrochemicals, 
Chemical Engineering Transactions, 114, 595-600  DOI:10.3303/CET24114100 
  

 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 114, 2024 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.cetjournal.it 

Guest Editors: Petar S. Varbanov, Min Zeng, Yee Van Fan, Xuechao Wang 

Copyright © 2024, AIDIC Servizi S.r.l. 

ISBN 979-12-81206-12-0; ISSN 2283-9216 

The Development Review on Light Cycle Oil Upgrading 

Technology to Fuels and Petrochemicals 

Xia Liu*, Laibin He 

Sinopec Shanghai Research Institute of Petrochemical Technology, Shanghai 201208, China 

liuxia.sshy@sinopec.com 

Light cycle oil (LCO) is a middle distillate produced in the fluidized catalytic cracking (FCC) unit with a high 

content of aromatics, high sulfur and nitrogen, and low cetane number, which cannot meet the requirements of 

diesel blending requirement under the China National VI standard regulation. Hydrogenation is an important 

technology for LCO upgrading and utilization. By combining hydrotreating (HDT) process, desulfurization and 

denitrification steps are carried out, and the aromatic hydrocarbons with more than two rings are partially 

converted into cyclo-alkylbenzene. Combined hydrocracking (HYC) steps, cyclohexane undergoes ring 

opening, cracking, and isomerization reactions, LCO can be upgrading to producing high quality fuels 

including high-octane gasoline, and chemical products including light aromatic hydrocarbon rich in benzene, 

toluene, and xylenes. With the development of upgrading technology, integrating heavy oil hydrogenation with 

selective catalytic cracking, LCO can produce aromatics, ethylene and propylene, which providing an ideal 

pathway to valuable petrochemicals from LCO. The upgrading utilization of LCO is an important technological 

choice for refining enterprises to take their own advantages to enhance valuable products and achieve 

sustainable development. 

1. Introduction 

Fluid catalytic cracking (FCC) process is one of the important processes of crude oil in the refining industry, 

which has been widely used in China due to its high gasoline yield and product flexibility. At present, the 

domestic catalytic cracking processing capacity is about 200 million tons/year in China. In the future, it is 

expected that the catalytic cracking units in China will increase production capacity by 20-30 %. The 

widespread application of catalytic cracking technology has resulted in catalytic diesel accounting for over 30 

% of China's diesel fuel. The light cycle oil (LCO) is one of the main by-products of fluidized catalytic cracking 

units. The LCO yield is approximately 15-20 % of the total FCC products (Peng et al., 2016), while the current 

total LCO production in China is about 50 million tons/year. However, LCO has the characteristics of high 

density, low cetane number (15–25) (Peng et al., 2016), high aromatic content, and high impurity content such 

as sulfur (0.2-1.5 wt %) and nitrogen (100-1,000 ug/g) (Stanislaus et al., 2010). The typical commercial LCO 

properties are shown in Table1 (Dai,2017). 

Table 1: LCO typical properties 

Item  LCO-1 LCO-2 LCO-3 

Cetane number 22.7 27.8 20 

elementary composition    

Carbon, wt% 89.3 89.32 90.42 

Hydrogen, wt% 9.66 10.68 9.57 

Sulfur, wt% 7400 4100 1700 

Nitrogen, wt% 1300 700 200 

The difficulty for using LCO directly was finished products stems from the LCO physical and chemimcal 

properties. The mass fraction of aromatics in LCO is generally between 75-90 % (Laredoet al., 2018), and the 

typical distribution of LCO aromatics is shown in Figure 1. LCO is commonly used as blend stock for heating 

595



oil, industrial fuel oil, and diesel. Nevertheless, with the improvement of environmental protection requirements 

and continuous improvement of diesel quality standard, the China VI standard legislation on fuel quality has 

established the maximum polycyclic aromatic hydrocarbon (PAH) content decrease to below 7 % comparing 

with the previous China V standard legislation value of 11 wt%, the diesel demands for LCO has been 

reduced. 

 

Figure 1: The typical mass fraction distribution of LCO aromatic hydrocarbons 

With the proposal of the “Carbon Peak and Carbon Neutrality” goals, China’s energy structure is facing 

significant adjustment, and the proportion of renewable energy is constantly increasing. Afterwhile, the 

domestic fuel oil market volume will continue to decline after the peak of the gasoline and diesel in China. 

Optimizing the utilization of LCO to produce high value-added energy and chemical products is significant for 

the refining and chemical plants. 

Hydrogenation is an important technology to improve the quality of high polycyclic aromatic hydrocarbon (PAH) 

content LCO. LCO is typically upgraded by hydrotreating units under mild conditions to produce the feed of 

FCC units, or through severe hydrotreatment to produce high-octane gasoline or ultra-low sulfur diesel (ULSD) 

contains less than 10 or 15 ppm sulphur (Peng et al., 2016). Combining the hydrotreating and hydrocracking 

steps, benzene, toluene and xylenes (BTX) are enriched in products fraction (Laredo et al., 2018). With the 

development of upgrading technology, and integrating heavy oil hydrogenation with selective catalytic cracking, 

LCO can produce aromatics, ethylene, and propylene. The upgrading utilization of LCO is an important 

technological choice for refining enterprises to take their own advantages to enhance product value and 

achieve sustainable development. 

2. High quality fuels from LCO  

The technologies targeting for producing high-quality fuel using LCO can be divided into two categories: 1) 

LCO hydrotreating (HDT) and upgrading technology for ultra-low sulfur diesel production, with the target 

product is diesel. 2) LCO hydrotreating combines hydrocracking (HYC) technology for producing gasoline and 

ultra-low sulfur diesel, with the target products being gasoline and diesel.  

R1

R2

R1

R2

R1

R2

R1

R2

R1

R2(1)

(2)

(3)

(4)

(5)

(6)

 

Figure 2: The typical reaction pathways of LCO updating process 

The typical reaction pathway of hydrotreaing process is shown in Figure 2, LCO hydrotreating (HDT) pathway: 

(1)→(2) →(5). 

0

10

20

30

40

50

60

Alkanes Cycloalkanes Mono-aromatics Di-aromatics Tri-aromatics

LCO -1# LCO-2# LCO-3#

w
t 

%

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The UOP Unionfining process flow scheme for hydrotreating LCO is typically a once-through process, as 

shown in Figure 2. The LCO feed is processed over hydrotreating catalysts under hydrogen pressure to affect 

hydrodesulfurphurization, hydroenitrification and aromatic saturation. Operating conditions conductive for 

saturating aromatics in LCO are necessary to produce the hydrotreated ultra-low sulfur effluent. The 

hydrotreating process typically uses an active nickel-molybdenum catalysts with a reactor temperature ranging 

from 350 to 400 ℃. As a consequence, tremendous saturation reactions occurred during hydrotreating in the 

reactor.  

H2

LCO

Recycle H2

HDT

HDT

HDT

reactor
Seperator Off gas

LPG

Utra-low sulfur 

diesel

 

Figure 3: The flowsheet of UOP Unionfining process for LCO targeting utra-low sulphur diesel 

MHUG is typical process targeting for producing the diesel using LCO was patented by Sinopec RIPP (Lin, 

2019). The feed in MHUG process can be 100 % LCO, or mixture of diesel and LCO. Through hydrotreating 

and upgrading, polycyclic aromatic hydrocarbons are hydrogenated and saturated, and selective cycloalkane 

ring opening is carried out to obtained high quality diesel with low aromatic content, high cetane number, and 

low density.  

The LCO hydrotreating combined hydrocracking technology for producing gasoline and diesel is represented 

by UOP LCO Unicracking (Bisht and Petri, 2014), Sinopec RLG and FD2G technology (Han et al., 2022). The 

process is applying LCO as the feed, including two-bed catalytic process involving hydrogenation and 

hydrocracking for producing high-octane gasoline fuel. And relevant reaction pathways are shown in Figure 2, 

RLG/FD2G pathway: (1)→(2)→(3). 

H 2
recycle H 2

LC O

H D T
reactor

H Y C
reactor

Seperator
D istillation 
colum n

liquefied nature gas

light naphtha

gasoline

diesel
recycle diesel

 

Figure 4: The typical flowsheet of LCO HTD combined HYC process for targeting gasoline and diesel 

When LCO is hydrocracked under higher pressure and high conversion into naphtha, the aromatic rings are 

substantially hydrogenated forming naphtha with a high concentration of naphthenes and a low concentration 

of aromatics. In addition to reactions that are typical of hydrotreating, hydrocracking also performs alkyl chain 

cracking and ring opening. The desulphurization, saturation of rings, alkyl chain cracking and ring opening 

consume larger quantities of ‘make-up’ hydrogen compared to hydrotreating options. And the heat release 

from these reactions is greater than hydrotreating alone, meanwhile a higher capacity recycle gas compressor 

are required to manage the catalyst temperature rises.  

In the FD2G process, there is a high content of aromatics in the gasoline products, and aromatics can be 

obtained through aromatics extraction technology. This technology can produce 35-58 % clean diesel with a 

sulfur content is lower than 10 ppm, a cetane number between 29 and 35, and a cetane index of 36, at the 

597



same time, clean gasoline with 92-94 RON can be produced, with the yield of 35-55 %. The typical products 

distribution in commercial LCO upgrading process is shown in Table 2. 

The conventional catalysts required in the hydrotreating step are nickel-molybdenum on alumina (NiMo/Al2O3) 

(Fischer et al., 1988) and cobalt/molybdenum on alumina (CoMo/Al2O3) (Derr et al., 1991). Likewise, ultra-

stable zeolite Y (USY) with nickel-tungsten (NiW), NiMo or CoMo, as metal components, were used for the 

hydrocracking step (Laredo et al., 2018). 

Table 2: Products distribution in FD2G process for LCO upgrading (Zheng et al.,2017) 

Item  Once-through  Partial recycle Full recycle 

Pressure / Mpa 8.0 8.0 8.0 

Temperature /℃ 405 415 397 

Conversion ratio, % 51 55 50 

Gasoline yield, wt% 54.22 53.27 89.65 

Diesel yield, wt% 40.81 35.95 - 

Aromatics fraction in gasoline 62.01 - - 

Hydrogen consumption, wt% 3.31 3.48 3.99 

3. Valuable petrochemicals from LCO  

Currently, there is an excess of diesel, however the demand for aromatics and light olefins are increasing year 

by year. Light aromatics like benzene, toluene and xylene (BTX) are valuable and high demands 

petrochemicals. Obtaining chemical products from LCO is an ideal way to solve the problem of diesel excess 

and light aromatics shortage. The production of BTX aromatics from low-quality heavy LCO requires cracking 

the other aromatic rings while retaining one of the polycyclic aromatic hydrocarbons in the low-quality heavy 

aromatics, effectively controlling saturation depth and ring opening position, and maximizing the production of 

light aromatics at lower hydrogen consumption. The LCO hydrotreating combined hydrocracking, or fluidized 

catalytic cracking (FCC) technology also can targeting for producing valuable petrochemicals, including 

benzene, toluene and xylene , which is an attractive technology as well.  

The technologies targeting for producing light aromatics using LCO also can be divided into three categories: 

1) LCO hydrotreating combine hydrocracking technology for producing light aromatics, with the target products 

being BTX. The product structure of the LCO hydrotreating combine hydrocracking technology process is 

listed in Table 3. As shown in the table, the yield of high octane gasoline is about 54 %, of which aromatics 

account for about 60 %, which only requires adaptive modification of the aromatics separation process to be 

implemented to produce the BTX products. 

2) LCO hydrotreating integrated fluidized catalytic cracking technology for producing light aromatics and 

olefins. LCO is the diesel fraction product of the fluidized catalytic cracking unit, and after hydrogenation 

pretreatment, LCO is returned to the fluidized catalytic cracking unit, which is a LCO hydrotreating integrated 

fluidized catalytic cracking conversion. In this conversion scheme, it can reduce the output of low-quality LCO 

and increase high octane gasoline or aromatics product under low investment. 

3) The combination processing scheme of LCO hydrocracking integrated with aromatics maximization 

targeting for the maximization of BTX. The important step of the scheme is that produced naphtha is sent to 

the aromatics maximization reaction system and undergoes processes such as cyclohexane dehydrogenation, 

alkyl transfer, isomerization, xylene separation, and distillation to obtain benzene and xylene products. 

H D T
reactor

selective
H Y C
reactor

D istillation

C 2-C 5 light 
hydrocarbons

C 6-C 8 alkanes

B TX

 C 9A , C 10A  

diesel

LC O

H 2
H 2

 

Figure 5: The flowsheet of Sinopec SRIPT LCO HTD combined selective HYC process for chemical materials 

Zheng et al. from Sinopec SRIPT patented a process for producing chemical materials from LCO, the 

flowsheet of the process is shown in Figure 5 (Zheng et al., 2021). The technical solution of the present 

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invention includes hydrotreating and selective hydrocracking technology conversion reaction of LCO feed flow. 

The selective hydrocracking conversion catalyst includes β zeolite, VIB group metal sulfides, and binders. 

After separation, the products were sequentially separated into C2-C5 light hydrocarbons, C6-C8 alkanes, 

benzene, toluene, C8A, C9A, C10A aromatics, and diesel. After the diesel at the bottom of the distillation 

tower enters hydrotreating reactor. This technology can realize the full fraction conversion of chemical 

feedstocks from catalytic diesel production has a higher yield of BTX light aromatics, as well as the technical 

effect of producing chemical feedstocks such as C2-C5 light hydrocarbons and C6-C8 alkanes. 

HDT FCC

Ring openingAromatics 

saturation
 

Figure 6: The reaction pathways of LCO HTD combined FCC technology 

The LCO hydrotreating combine catalytic cracking reaction pathways are shown in Figure 6. The key of 

technology is to generated monocyclic aromatic hydrocarbons like tetralin compounds from polycyclic 

aromatic hydrocarbons in LCO by selective hydrogenation saturated reaction. Then by strengthening hydro-

LCO carried on catalytic cracking reaction and inhibiting the hydrogen transfer reaction, hydro-LCO can be 

converted to high octane number gasoline or light aromatics, ethylene, and propylene (Mao et al., 2020).  

FC C
unit

H ydrogenation 
unit

G asoline/ 
B TX

H ydro-LC O

LC O

LC O

H 2

H ydro-LC O

C 2-C 3 O lefins

 

Figure 7: The flowsheet of Sinopec LTAG process for aromatics and gasoline 

LTAG (LCO to Aromatics and Gasoline) and LTA (LCO to Aromatics and Gasline) technology is proposed by 

Sinopec RIPP (Gong et al., 2016). In the LTAG technology the di-aromatics in LCO is selectively hydrotreated 

in hydrotreating unit to mono-aromatics with tetralin structure. While ring opening reactions are taken place 

and hydrogen transfer reactions are inhabited in the followed fluidized catalytic cracking (FCC) unit. Applied 

an optimized combination of two units can achieve maximum production of high octane gasoline or light 

aromatics. The high octane number gasoline fraction or light aromatics are produced by hydro-LCO individual 

catalytic cracking. The flowsheet of the LTAG is shown in the Figure 7. The industrial results show that after 

LCO hydrogenation can achieve full conversion of LCO under full cycle conditions, achieving gasoline yield of 

55.87 %, C6-C8 aromatics yield of 16.89 %, and gasoline RON is 96.4 (Gong et al., 2016). 

H2

LCO

Recycle H2

HDT

HCY

Reactor
Seperator Off gas

LPG

Utra-low sulfur 

diesel

Aromatics
maximization

Light 

naphtha

BTX

 

Figure 8: The flowsheet of UOP LCO-X process targeting for the BTX products 

UOP company has developed a new process LCO-X for catalytic light cycle oil hydrogenation conversion 

selective alkyl transfer to produce maximization of xylene and benzene. The principle of LCO-X process is to 

first refine and remove sulfur and nitrogen impurities from the raw oil, selectively saturate the polycyclic 

599



aromatic hydrocarbons, and then enter a series of hydrocracking reactors for selective cracking reaction. The 

produced naphtha is sent to the aromatics maximization reaction system and undergoes processes such as 

cyclohexane dehydrogenation, alkyl transfer, isomerization, xylene separation, and distillation to obtain 

benzene and xylene products. The rest are by-products such as LPG, light naphtha, and utra-low sulfur diesel. 

Figure 8 shows the process flow diagram of LCO-X technology (Bisht and Petri, 2014). However, this process 

requires the construction of a series of reaction and the separation units after the hydrocracking reaction, and 

the whole process is very long. 

4. Conclusions 

The demand of producing fuels from low-quality diesel will continue to decrease in the future. At the same time, 

there is a shortage of basic petrochemicals such as benzene, toluene, and xylene (BTX), making it imperative 

to convert polycyclic aromatic hydrocarbons in LCO into high quality gasoline and light aromatic hydrocarbons 

to satisfy their increasing demand. Obtaining chemical products from LCO is an ideal way to solve the problem 

of diesel excess and light aromatics shortage. The production of petrochemicals from low-quality LCO requires 

cracking the other aromatic rings while retaining one of the polycyclic aromatic hydrocarbons in the low-quality 

heavy aromatics, effectively controlling saturation depth and ring opening position, and maximizing the 

production of light aromatics at lower hydrogen consumption. The keys for LCO upgrading are to optimizing 

the combination of different catalysts and units, maximizing the targeting products, avoiding loss of aromatics. 

With the development of hydrotreating (HDT) combined fluidized catalytic cracking (FCC) technology, LCO 

can produce aromatics, ethylene, and propylene, making it a promising choice for refining enterprises. 

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