**3.1. Decomposition of AR**

Catalytic cracking of AR was conducted using a downflow-type fixed-bed reactor loaded with 1.5 g of catalyst at 748 K under atmospheric pressure [9, 12]. A 10 wt% solution of AR with toluene was fed to the reactor at flow rate (*F*) of 1.1 g/h using a syringe pump. AR was diluted with toluene to reduce the viscosity of AR, and the catalyst was confirmed to be


**Table 1.** Properties of AR.

almost inactive to toluene. Total flow rate of mixture of steam and nitrogen was adjusted to 80 cm3 (STP)/min. After 2 h of operation, the pump of AR solution was stopped, and the reactor was cooled. The gas products were separated through an ice trap and analyzed by gas chromatography (GC-12A and GC-14A, Shimadzu Corp.) with thermal conductivity and flame ionization detectors equipped with Porapak-Q and Unibeads 3S columns, respectively. The boiling point distribution was determined by the gas chromatographic distillation. The residue deposited on the catalyst was analyzed by elemental analysis (EA1110, Finningan Mat).

**3. Activity of** *α***-Fe2**

180 Iron Ores and Iron Oxide Materials

O3

in a steam atmosphere.

**Composition [wt%]**

Density [g/cm<sup>3</sup>

Metals [ppm]

Reproduced from elsewhere [11].

**Table 1.** Properties of AR.

**Elemental analysis [wt%]**

**3.1. Decomposition of AR**

**of heavy oil**

The *α*-Fe<sup>2</sup>

**O3**

Light oil 7 VGO 49 VR 44

C 85.7 H 11.6 N 0.16 S 2.48 H/C [mol/mol] 1.63 **Conradson carbon residue [wt%]** 5.8

V 10 Ni 4 Fe 10

] 0.944

 **catalyst containing Zr and Al for decomposition** 

**AR**

catalyst containing Zr and Al was used for catalytic cracking of atmospheric

residual oil (AR) derived from Middle East crude [9]. **Table 1** showed the properties of AR [11]. Composition of light oil (boiling point <623 K), vacuum gas oil (VGO, boiling point 623–773 K), and vacuum residue (VR, boiling point >773 K) was determined by the gas chromatographic distillation (HP6890, Agilent Technologies) with a wide-bore capillary column according to ASTM D 2887. AR has high viscosity, low H/C ratio, and high content of highboiling-point components. This section describes the activity of the catalyst to decompose AR

Catalytic cracking of AR was conducted using a downflow-type fixed-bed reactor loaded with 1.5 g of catalyst at 748 K under atmospheric pressure [9, 12]. A 10 wt% solution of AR with toluene was fed to the reactor at flow rate (*F*) of 1.1 g/h using a syringe pump. AR was diluted with toluene to reduce the viscosity of AR, and the catalyst was confirmed to be **Figure 3** showed the composition of AR and product yield of the AR cracking at flow rate ratio of steam to AR solution (*F*<sup>S</sup> /*F*) of 0.42 g/g [9]. The high-boiling-point components, such as VGO and VR, decreased, producing light oil, CO<sup>2</sup> , organic gas (C<sup>1</sup> –C<sup>4</sup> ), and residue. Generation of CO<sup>2</sup> indicated that the heavy oil fraction was oxidatively cracked.

**Figure 4** showed the XRD patterns of the used catalysts after the catalytic cracking of AR with and without steam [9]. The patterns of reagent iron (III) oxide (*α*-Fe<sup>2</sup> O3 ) and iron (II, III) oxide (Fe<sup>3</sup> O4 , Strem Chemicals, Inc.) were shown for comparison. The patterns of both used catalysts consisted of *α*-Fe<sup>2</sup> O3 and Fe<sup>3</sup> O4 . The peaks of Fe<sup>3</sup> O4 mainly appeared in the patterns of the used catalyst without steam. These results indicated that part of lattice oxygen of *α*-Fe<sup>2</sup> O3 reacted with heavy oil fractions to produce light hydrocarbons and CO<sup>2</sup> at first [12]. Then, oxygen species generated from steam were incorporated into the iron oxide lattice and reacted with heavy oil fractions. Hence, the *α*-Fe<sup>2</sup> O3 structure was partially maintained after the reaction with steam. Consequently, the heavy oil fractions were oxidatively cracked using oxygen species derived from steam.

When dodecylbenzene was used as a model compound of heavy oil, a small amount of oxygen containing compounds, such as phenol, acetophenone, undecanone, and hydroxybiphenyl, was produced in the catalytic cracking of dodecylbenzene [9]. Kondoh et al. reported that the catalytic cracking of heavy oil with heavy oxygenated water (H<sup>2</sup> <sup>18</sup>O) produced CO<sup>2</sup> containing

**Figure 3.** Product yield of catalytic cracking of AR with steam (*F*<sup>S</sup> /*F* = 0.42) and composition of AR (reproduced from elsewhere [9]).

**Figure 4.** XRD patterns of used catalysts for catalytic cracking of AR with and without steam (*F*<sup>S</sup> /*F* = 0, 0.42), regent *α*-Fe<sup>2</sup> O3 , and reagent Fe<sup>3</sup> O4 (reproduced from elsewhere [9]).

heavy oxygen (CO<sup>18</sup>O) [13]. Accordingly, most of oxygen species were supplied to form CO<sup>2</sup> , and a small amount of oxygen species was supplied to oxygen –containing compounds.

The *α*-Fe<sup>2</sup> O3 catalyst containing Zr showed the higher activity than the *α*-Fe<sup>2</sup> O3 catalyst without Zr because ZrO<sup>2</sup> in the catalyst promotes the generation of oxygen species from steam [3]. Addition of Al to the catalyst enhanced the durability of the catalyst. The activity of the ZrO<sup>2</sup> -supporting *α*-Fe<sup>2</sup> O3 catalyst without Al decreased after the sequence of reaction and regeneration because of phase change of iron oxide and subsequent peeling of ZrO<sup>2</sup> [7].

#### **3.2. Effect of steam on product of AR cracking**

To examine the effect of steam flow rate on product yield of AR cracking, catalytic cracking of AR was conducted at various steam flow rates (*F*<sup>S</sup> /*F* = 0–3.0), and the product yield was shown in **Figure 5** [9]. The yields of light oil, VGO, VR, and residue little changed, suggesting that steam concentration hardly affected the decomposition of heavy oil. The heavy oil fractions reacted with oxygen species incorporated from steam to the iron oxide lattice after the lattice oxygen of *α*-Fe<sup>2</sup> O3 reacted with heavy oil fractions. The CO<sup>2</sup> yield increased with increase in the flow rate ratio of steam to AR solution due to increase in oxygen species derived from steam.

were supplied to form C1

–C<sup>4</sup>

1 mole of C1

–C<sup>4</sup>

**Figure 6.** Consumed amount of steam for catalytic cracking of AR with steam (*F*<sup>S</sup>

**Figure 5.** Product yield of catalytic cracking of AR with and without steam (*F*<sup>S</sup>

might be supplied to liquid hydrocarbons and residue.

hydrocarbons if two moles of hydrogen species were supplied to

/*F* = 3.0).

/*F* = 0–3.0) (reproduced from elsewhere [9]).

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183

hydrocarbons. Hence, the remaining hydrogen species (approximately 67%)

Supplies of hydrogen species from steam to liquid hydrocarbons and residue resulted in decrease in alkene generation and increase in H/C of residue [9]. **Figure 7** showed the alkene/alkane ratio of aliphatic hydrocarbons and H/C ratio of residue produced by the catalytic cracking of AR with and without steam. The aliphatic hydrocarbons in the liquid

When oxygen species were generated from steam and reacted with heavy oil, hydrogen species were simultaneously generated from steam [9]. Consumed amount of steam was calculated from the CO<sup>2</sup> yield in the catalytic cracking of AR at flow rate ratio of steam to AR solution (*F*<sup>S</sup> /*F*) of 3.0 g/g and shown in **Figure 6**. If half of the sulfur compounds in AR were converted to H<sup>2</sup> S by the reaction of hydrogen species and sulfur compounds, approximately 14% of hydrogen species were supplied to form H2 S. Approximately 19% of hydrogen species

**Figure 5.** Product yield of catalytic cracking of AR with and without steam (*F*<sup>S</sup> /*F* = 0–3.0) (reproduced from elsewhere [9]).

**Figure 6.** Consumed amount of steam for catalytic cracking of AR with steam (*F*<sup>S</sup> /*F* = 3.0).

heavy oxygen (CO<sup>18</sup>O) [13]. Accordingly, most of oxygen species were supplied to form CO<sup>2</sup>

catalyst containing Zr showed the higher activity than the *α*-Fe<sup>2</sup>

steam [3]. Addition of Al to the catalyst enhanced the durability of the catalyst. The activ-

reaction and regeneration because of phase change of iron oxide and subsequent peeling

To examine the effect of steam flow rate on product yield of AR cracking, catalytic cracking

shown in **Figure 5** [9]. The yields of light oil, VGO, VR, and residue little changed, suggesting that steam concentration hardly affected the decomposition of heavy oil. The heavy oil fractions reacted with oxygen species incorporated from steam to the iron oxide lattice after

increase in the flow rate ratio of steam to AR solution due to increase in oxygen species

When oxygen species were generated from steam and reacted with heavy oil, hydrogen species were simultaneously generated from steam [9]. Consumed amount of steam was cal-

reacted with heavy oil fractions. The CO<sup>2</sup>

yield in the catalytic cracking of AR at flow rate ratio of steam to AR

/*F*) of 3.0 g/g and shown in **Figure 6**. If half of the sulfur compounds in AR were

S by the reaction of hydrogen species and sulfur compounds, approximately

in the catalyst promotes the generation of oxygen species from

catalyst without Al decreased after the sequence of

/*F* = 0–3.0), and the product yield was

S. Approximately 19% of hydrogen species

and a small amount of oxygen species was supplied to oxygen –containing compounds.

**Figure 4.** XRD patterns of used catalysts for catalytic cracking of AR with and without steam (*F*<sup>S</sup>

(reproduced from elsewhere [9]).

The *α*-Fe<sup>2</sup>

*α*-Fe<sup>2</sup> O3

of ZrO<sup>2</sup>

ity of the ZrO<sup>2</sup>

[7].

O3

, and reagent Fe<sup>3</sup>

182 Iron Ores and Iron Oxide Materials

O4

without Zr because ZrO<sup>2</sup>

the lattice oxygen of *α*-Fe<sup>2</sup>

derived from steam.

culated from the CO<sup>2</sup>

solution (*F*<sup>S</sup>

converted to H<sup>2</sup>


**3.2. Effect of steam on product of AR cracking**

of AR was conducted at various steam flow rates (*F*<sup>S</sup>

O3

14% of hydrogen species were supplied to form H2

O3

,

catalyst

O3

/*F* = 0, 0.42), regent

yield increased with

were supplied to form C1 –C<sup>4</sup> hydrocarbons if two moles of hydrogen species were supplied to 1 mole of C1 –C<sup>4</sup> hydrocarbons. Hence, the remaining hydrogen species (approximately 67%) might be supplied to liquid hydrocarbons and residue.

Supplies of hydrogen species from steam to liquid hydrocarbons and residue resulted in decrease in alkene generation and increase in H/C of residue [9]. **Figure 7** showed the alkene/alkane ratio of aliphatic hydrocarbons and H/C ratio of residue produced by the catalytic cracking of AR with and without steam. The aliphatic hydrocarbons in the liquid

**4.1. Desulfurization of AR**

steam atmosphere (*F*<sup>S</sup>

a steam atmosphere.

with heavy oil.

Catalytic cracking of AR with the *α*-Fe<sup>2</sup>

AR at 3.1. Produced amounts of H<sup>2</sup>

tal analysis (EA1110, Finningan Mat.)

zothiophene was decomposed producing CO<sup>2</sup>

**4.2. Effect of steam on desulfurization of AR**

ducted at various steam flow rates (*F*<sup>S</sup>

of AR without steam produced little H<sup>2</sup>

rate ratio of steam to AR solution. The CO<sup>2</sup>

O3

S and SO<sup>2</sup>

to 1.4 wt% compared to the 2.5 wt% of sulfur in AR, and H<sup>2</sup>

catalytic cracking of AR at flow rate ratio of steam to AR solution (*F*<sup>S</sup>

some hydrogen species derived from steam to produce H<sup>2</sup>

**Figure 8.** Sulfur yield of catalytic cracking of AR with and without steam (*F*<sup>S</sup>

Corp.). Sulfur content in liquid products was determined by oxidative microcoulometry according to JIS K 2541-2. Sulfur contents deposited on the catalyst were measured by elemen-

Catalytic cracking of AR produced approximately 61 mol%-C of oil product, 4 mol%-C of gas product, and 35 mol%-C of residue. Sulfur concentration in the product oil decreased

that sulfur compounds in AR were decomposed [10]. When desulfurization was conducted using dibenzothiophene as a model compound of a cyclic sulfur compound in AR, diben-

[10]. Hence, acyclic and cyclic sulfur compounds might be decomposed with the catalyst in

To examine the effect of steam on desulfurization of AR, catalytic cracking of AR was con-

yield of oil and residue was almost constant as shown in **Figure 5**. The catalytic cracking

S, and the H<sup>2</sup>

ratio of steam to AR solution. These results indicated that sulfur compounds reacted with

, H<sup>2</sup>

catalyst containing Zr and Al was conducted in a

were measured by gas detecting tube (GASTEC

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185

S was generated, indicating

/*F*) of 0–2.7. The carbon

S, hydrocarbons, and sulfur compounds

S yield increased with increase in flow

S when oxygen species reacted

/*F* = 0–2.7) (reproduced from elsewhere [10]).

/*F* = 0–2.7) [10]. **Figure 8** showed the sulfur yield of

yield also increases with increase in the flow rate

/*F* = 2.7) [10]. The reaction conditions were the same as decomposition of

**Figure 7.** Alkene/alkane ratio of aliphatic hydrocarbons and H/C ratio of residue produced by the catalytic cracking of AR with and without steam (*F*<sup>S</sup> /*F* = 0–3.0) (reproduced from elsewhere [9]).

product were analyzed by gas chromatography with a flame ionization detector (GC-FID, 6890N, Agilent Technologies) and mass spectrometry (GC-MS, HP6890-HP5973, Agilent Technologies) with capillary columns. The alkene/alkane ratio of light hydrocarbons (C9 –C13) decreased with increase in flow rate ratio of steam to AR solution, suggesting that hydrogen transfer from steam to light hydrocarbons suppressed alkene generation. The H/C ratio of residue produced by the AR cracking with steam was higher than that produced by the AR cracking without steam. Some hydrogen species supplied from steam to the residue and others supplied to light hydrocarbons.

#### **4. Activity of** *α***-Fe2 O3 catalyst containing Zr and Al for desulfurization of heavy oil**

The petroleum residual oil including AR contains sulfur. Hydrodesulfurization is the useful method to remove sulfur from petroleum, producing high-quality oil. The residual oil contains acyclic sulfur compounds, such as thiols and disulfides, and cyclic compounds including thiophene ring. The decomposition of the cyclic sulfur compounds was harder than acyclic compounds [14].

The catalytic cracking of heavy oil with steam using the *α*-Fe<sup>2</sup> O3 catalyst containing Zr and Al produced the hydrogen species during the reaction of heavy oil with the oxygen species derived from steam [9]. Some hydrogen species were supplied to hydrocarbons and residue. The remaining hydrogen species might react with sulfur compounds in AR and be supplied to form H2 S [10]. Hence, desulfurization of AR with the catalyst in a steam atmosphere was examined in this section.

### **4.1. Desulfurization of AR**

Catalytic cracking of AR with the *α*-Fe<sup>2</sup> O3 catalyst containing Zr and Al was conducted in a steam atmosphere (*F*<sup>S</sup> /*F* = 2.7) [10]. The reaction conditions were the same as decomposition of AR at 3.1. Produced amounts of H<sup>2</sup> S and SO<sup>2</sup> were measured by gas detecting tube (GASTEC Corp.). Sulfur content in liquid products was determined by oxidative microcoulometry according to JIS K 2541-2. Sulfur contents deposited on the catalyst were measured by elemental analysis (EA1110, Finningan Mat.)

Catalytic cracking of AR produced approximately 61 mol%-C of oil product, 4 mol%-C of gas product, and 35 mol%-C of residue. Sulfur concentration in the product oil decreased to 1.4 wt% compared to the 2.5 wt% of sulfur in AR, and H<sup>2</sup> S was generated, indicating that sulfur compounds in AR were decomposed [10]. When desulfurization was conducted using dibenzothiophene as a model compound of a cyclic sulfur compound in AR, dibenzothiophene was decomposed producing CO<sup>2</sup> , H<sup>2</sup> S, hydrocarbons, and sulfur compounds [10]. Hence, acyclic and cyclic sulfur compounds might be decomposed with the catalyst in a steam atmosphere.

### **4.2. Effect of steam on desulfurization of AR**

product were analyzed by gas chromatography with a flame ionization detector (GC-FID, 6890N, Agilent Technologies) and mass spectrometry (GC-MS, HP6890-HP5973, Agilent Technologies) with capillary columns. The alkene/alkane ratio of light hydrocarbons (C9

**Figure 7.** Alkene/alkane ratio of aliphatic hydrocarbons and H/C ratio of residue produced by the catalytic cracking of

/*F* = 0–3.0) (reproduced from elsewhere [9]).

decreased with increase in flow rate ratio of steam to AR solution, suggesting that hydrogen transfer from steam to light hydrocarbons suppressed alkene generation. The H/C ratio of residue produced by the AR cracking with steam was higher than that produced by the AR cracking without steam. Some hydrogen species supplied from steam to the residue and oth-

The petroleum residual oil including AR contains sulfur. Hydrodesulfurization is the useful method to remove sulfur from petroleum, producing high-quality oil. The residual oil contains acyclic sulfur compounds, such as thiols and disulfides, and cyclic compounds including thiophene ring. The decomposition of the cyclic sulfur compounds was harder than

Al produced the hydrogen species during the reaction of heavy oil with the oxygen species derived from steam [9]. Some hydrogen species were supplied to hydrocarbons and residue. The remaining hydrogen species might react with sulfur compounds in AR and be supplied

S [10]. Hence, desulfurization of AR with the catalyst in a steam atmosphere was

 **catalyst containing Zr and Al for desulfurization** 

O3

catalyst containing Zr and

ers supplied to light hydrocarbons.

**O3**

The catalytic cracking of heavy oil with steam using the *α*-Fe<sup>2</sup>

**4. Activity of** *α***-Fe2**

AR with and without steam (*F*<sup>S</sup>

184 Iron Ores and Iron Oxide Materials

acyclic compounds [14].

examined in this section.

**of heavy oil**

to form H2

–C13)

To examine the effect of steam on desulfurization of AR, catalytic cracking of AR was conducted at various steam flow rates (*F*<sup>S</sup> /*F* = 0–2.7) [10]. **Figure 8** showed the sulfur yield of catalytic cracking of AR at flow rate ratio of steam to AR solution (*F*<sup>S</sup> /*F*) of 0–2.7. The carbon yield of oil and residue was almost constant as shown in **Figure 5**. The catalytic cracking of AR without steam produced little H<sup>2</sup> S, and the H<sup>2</sup> S yield increased with increase in flow rate ratio of steam to AR solution. The CO<sup>2</sup> yield also increases with increase in the flow rate ratio of steam to AR solution. These results indicated that sulfur compounds reacted with some hydrogen species derived from steam to produce H<sup>2</sup> S when oxygen species reacted with heavy oil.

**Figure 8.** Sulfur yield of catalytic cracking of AR with and without steam (*F*<sup>S</sup> /*F* = 0–2.7) (reproduced from elsewhere [10]).

The SO<sup>2</sup> was detected only in the reaction without steam. The lattice oxygen of iron oxide reacted with sulfur compounds, producing SO<sup>2</sup> in the catalytic cracking of AR without steam. The SO<sup>2</sup> has high solubility in water (1.4 mol/kg at 25°C [15]). Hence, no SO<sup>2</sup> might be detected in the catalytic cracking of AR with steam, even if oxygen species generated from steam reacted with sulfur compounds to form SO<sup>2</sup> . Some H2 S produced in the reaction also could be dissolved in water. When nitrogen was injected into the water collected in this reaction, H<sup>2</sup> S was detected [10]. The difference was approximately 23 mol%-S because of sulfur content, such as H<sup>2</sup> S and SO<sup>2</sup> , in water and measurement errors of sulfur concentration.

**Author details**

**References**

Technology, Tsukuba, Japan

2015;**27**:12-24

2015;**100**:70-78

2016;**179**:17-24

2006;**35**:998-999

Eri Fumoto\*, Shinya Sato and Toshimasa Takanohashi \*Address all correspondence to: e-fumoto@aist.go.jp

Wiley & Sons, Ltd; 2001. pp. 32-78

lyst. Energy & Fuels. 2004;**18**:1770-1774

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Sulfur content in residue decreased with increase in flow rate ratio of steam to AR solution. Larger amounts of hydrogen species were generated at higher ratio of steam to AR solution and reacted with heavy sulfur compounds deposited on the catalyst to produce light sulfur compounds and H2 S. Sulfur concentration in the oil decreased because sulfur compounds were decomposed to produce H2 S. Increase in sulfur concentration in the oil at *F*<sup>S</sup> /*F* = 2.7 was resulted from production of light sulfur compounds by the reaction of heavy sulfur compounds with large amounts of oxygen and hydrogen species.
