Study on Modification and Sulfur-Resistance Characteristics of

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Kinetics, Catalysis, and Reaction Engineering

Study on Modification and Sulfur-Resistance Characteristics of Dolomite Catalysts over Wash Oil Catalytic Cracking Juan Yu, Dechang Meng, Huawei Zhang, Junqiang Gao, Yaqing Zhang, Tiantain Jiao, and Peng Liang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b02545 • Publication Date (Web): 03 Aug 2018 Downloaded from http://pubs.acs.org on August 13, 2018

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Study on Modification and Sulfur-Resistance Characteristics of Dolomite Catalysts over Wash Oil Catalytic Cracking ∗

∗

Juan Yu1,2, Dechang Meng1, Huawei Zhang1, , Junqiang Gao1, Yaqing Zhang1, Tiantain Jiao1, Peng Liang1, 1 College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, The People’s Republic of China 2 School of Chemical and Biological Engineering, Qilu Institute of Technology, Jinan, Shandong 250200, The People’s Republic of China

Peng Liang, e-mail: [email protected]; tel.: +86 13678890728; fax: +86 532 86057718 Huawei Zhang, e-mail: [email protected]; tel.: +86 13806399945; fax: +86 532 86057718

1


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Abstract: 0.5%Ni/1%Fe-dolomite catalyst and 1%Fe-dolomite catalyst were used to explore wash oil catalytic cracking process on a fixed-bed reactor. The experimental results were evaluated by yield distributions of gas, liquid and solid phases; gas composition distributions; and components variety of cracked oil. Catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG) and an automatic sulfur analyzer. Cracked oil was analyzed by gas chromatography-mass spectrometry (GC-MS). XRD analyses revealed that fresh 0.5%Ni/1%Fe-dolomite catalyst behaved Ni-Fe and NiO crystal phase, while the used catalyst behaved CaS and NiS phase when there was sulfur-containing compounds with simple structure in wash oil. TG results showed that H2S contributed to the heavy aromatics adsorption on catalyst, and aggravated carbon deposition. GC-MS showed that cracked oil become lighter as a result of acenaphthene cracking into alkanes, biphenylene and pyrolysis gas. In addition, catalytic cracking of sulfur-containing compounds did not affect the contents of other liquid components.

2



1. Introduction Nowadays, with the rapid development of human society, there is an increasing demand in petroleum and natural gas sources for industrial production and social life. Unfortunately, fossil energy, especially petroleum oil, is known as the non-renewable resources, so that it is necessary to find other alternative liquid fuels in order to meet the need. Tar, produced by coal and biomass pyrolysis, is regarded as one of the most suitable substitutes to obtain the high-quality liquid fuels.1,2 The composition of tar is very complicated, containing more than 10000 kinds of polynuclear aromatic hydrocarbons (PAHs), sulfur-containing and oxygen-containing hydrocarbons.3,4 Heavy tar could lead to clogging pipes,5,6 corroding equipment in production, which causes resources waste and environmental pollution. Besides, sulfur-containing hydrocarbons cracking and incomplete combustion could lead to equipment corrosion and catalyst poisoning, which is contrary to green chemistry concept. Thus, conventionof heavy tar into high-quality liquid fuels with low sulfur content is crucial for efficient utilization of tar. Catalytic cracking of heavy tar is considered as one of the most excellent methods to achieve tar utilization. Cracking catalysts for tar decomposition mainly contain natural dolomite, alkali metals, nickel-based catalysts, noble metal catalysts, etc. Dolomite7-9 and nickel-based catalysts10,11 have been widely investigated and proven with good activity in terms of tar convention. Since natural dolomite is a cheaper choice with greater tar conversion activity, it has attracted more attention. Dolomite after calcined could provide acid-alkali active center named CaO-MgO, which not only behave good cracking activity, absorb toxic gas (SO2, H2S, etc.), 12 but also effective to suppress coking over acidic sites.13,14 Additionally, modified dolomite catalysts behaved superior activity, especially the Ni-dolomite catalysts. Wang et al.

15

studied that Ni-dolomite catalyst could get 95% one-way 3


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conversion of naphthalene with experimental parameters of temperature 700 °C and space velocity 0.8 h-1. However, there is more heavy tar in cracked oil after dolomite cracking though its amount decreased compared to the raw oil. Liang et al. 16 discovered that anthracene oil got higher C/H and become more condensed through natural dolomite cracking. Moreover, dolomite catalysts behave low mechanical strength and reactivity, and this problem is still a nodus in industrial production now. Nickel-based catalysts, such as Ni-Al2O3, 17 and Ni/Fe-Al2O3, 18 have widely been studied and reported to behave good catalytic performance toward aromatic hydrocarbon decomposition. Takeo Kimura et al. 19cleared that Ni/Ce-Al2O3 catalyst produced by an impregnation method behaved high catalytic and anti-carbon deposition activity. Wang et al.20,21reported that Ni-based catalyst can get 89% conversion of light hydrocarbons above 800 °C. Though nickel-based catalysts maintain good activity in tar conversion, they also suffer deactivation as the result of coke deposition, metal sintering22 and sulfur poisoning23,24 during a long experimental cycle. There are diverse reports which show a precipitous drop in the activity of the Ni catalyst when exposed to H2S, especially the higher H2S concentration.25,26Besides, according to Li et al.,27 deactivation of Ni/γ-Al2O3 due to H2S was instantaneous and the regeneration was a slow process. However, previous researches on the sulfur poisoning of nickel-based catalysts are mainly about H2S rather than catalytic cracking of sulfur-containing compounds in tar, which cannot reflect the integrity and authenticity of catalyst sulfur poisoning comprehensively. In this work, three kinds of catalysts, natural dolomite catalysts, 0.5%Ni/1%Fe-dolomite catalyst and 1%Fe-dolomite catalyst, were selected as object catalysts aiming to investigative wash oil cracking process on a fixed bed reactor. Besides, four sulfur-containing compounds, such as 1-octanethiol, methylthio-benzene, diphenyl disulfide and benzo[b]thiophene (BT)were added into wash oil to study the sulfur-resistance characteristic of 0.5%Ni/1%Fe-dolomite catalyst. In addition, wash oil, a special 4



representative of heavy tar, was the tar fraction of 230–300 °C, with density of 1.04–1.06 g/cm3. It mainly contains naphthalene and its homologues, antimony, hydrazine, oxygen hydrazine, phenol, nitrogen-containing compounds, etc. This present work can provide reference to reveal heavy tar cracking possible mechanism, and clear up catalyst sulfur poisoning deactivation rules. 2. Experimental Section 2.1 Experimental material preparation. Natural dolomites were supplied from Shijiazhuang, Hebei province, China. And the X-Ray fluorescence (XRF) analysis of its relevant components was shown in Table S1.0.5%Ni/1%Fe-dolomite catalyst and 1%Fe-dolomite catalystwere prepared by an impregnation method. Natural dolomite (0.42– 0.84 mm) was first impregnated at room temperature overnight with a mixed aqueous solution of Ni(NO3)2·6H2O and Fe(NO3)3·9H2O, followed by drying at 110 °C for 10 h, and finally calcined at 450°Cfor 2 h, and 800°C for 5 h in the muffle furnace with an air atmosphere, respectively. After calcination, the catalyst sample was sieved to obtain particles with diameter of 0.42–0.84 mm. These steps were shown in Figure 1.Wash oil used in this study was a distillate oil selected from Shanxi Coking Plant. The GC-MS analysis of wash oil was shown in Figure 2. 2.2 Equipment and procedures. Catalytic cracking reaction was carried out on a fixed-bed reactor (Figure 3),which comprised two peristaltic pumps, a preheater, an inner reactor (internal diameter = 20 mm, overall length = 1000 mm), an ice-cooled condenser, and other parts. The preheater temperature was set at 260 °C aiming to facilitate the evaporation of water and wash oil, which were injected into the preheater with the peristaltic pumps at feeding rates of 0.062 and 0.064 g/min, respectively. Catalyst samples (10 g) were loaded into the middle of the fixed-bed reactor and heated to a predetermined temperature under nitrogen atmosphere. 5


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During the cracking process, the feeding rates of H2 and N2 were 20 and 40 mL/min, respectively. And the space velocity was adjusted by modifying the N2 feeding rate in each run. After each reaction, the pyrolysis gases were separated by ice-water condensation, and the noncondensable gases and condensable oil were collected for gas chromatography (GC) analysis and gas chromatography–mass spectrometry (GC-MS) analysis, respectively. The gas, solid, oil yields and gas hourly space velocity were calculated as follows: g a s y i e l d ( % ) : YG =

∑ m × t ×100% ,

(1)

ms ×100% , moil0

(2)

i

moil0

solid yield (%): YS =

oil yield (%): YO =

moil f moil0

× 100% ,

ga s ho u rl y s p ac e ve l oc it y ( h – 1 ): V =

(3)

(Voil + V water + V N2 + V H 2 ) × 60 , Vcatalysts

(4 )

where, mi , ms , moil f , m oil , and t denoted the mass flow rate of pyrolysis gas component i (g/min), 0

the mass increase of the dolomite catalyst after cracking (g), the quantity of cracked oil (g), the quantity of raw oil (g), and the reaction time (min), respectively. Voil , V water , V N2 , and V H2 were related to the volume feed rate (mL/min) of raw oil, water, N2, and H2, respectively. Vcatalysts denoted the volume (mL) of the 10 g catalysts sample. In addition, all experiments were performed in triplicate, with the results reported as average values, and the mass balance before and after pyrolysis exceeded 95%. 2.3 Product analysis and characterization. Gaseous products were analyzed by GC. Small-molecule gases such as H2, N2, CO, CH4, and CO2 were analyzed by a thermal conductivity detector (GC-TCD, Ruihong, SP-6800A, China), whereas gaseous hydrocarbons such as CH4, C2H6, C2H4, C3H8, C3H6, and C4+ were analyzed by a flame 6



ionization detector (GC-FID, Fuli, SP-6890, China). And the molar amounts of gaseous products produced by per gram of wash oil were calculated based on the content of CH4. The separation of oil and water in pyrolysis oil was performed with n-hexane, for the different solubility of water and tar. Cracked oil after diluted was analyzed by GC-MS (Agilent, 7890A/5975C, USA). The chromatograph was equipped with an HP-5MS capillary column (30 m × 250 µm × 0.25 µm), and helium was used as a carrier gas. The sample (0.2 µL) was injected with splitless mode. The column oven temperature was set at 250 °C, with heating performed from 60 to 250 °C at a heating rate of2.5 °C/min. The solvent delay time was 4.5 min. Mass spectra were recorded in electron ionization mode at 70 eV for m/z = 35–500. The sulfur content of catalyst after reaction was measured by an automatic sulfur measuring instrument (Zhisheng Technology Co. Ltd, ZCL2003, China), which was determined by coulometric titration in the national standard GB/T214-2007. The compositions of catalysts were determined by X-ray diffraction (XRD, Rigaku, D/max-2550, Japan) using Cu Kα radiation. The XRD patterns were recorded at 200 mA and 40 kV for 2θ = 20-85 ° at a scan rate of 5 °/min. The amount of carbon deposited on the catalyst was determined by a thermogravimetric and differential thermal analyzer (TG, Sigammeter, LABSYS EVO TG-DTA/DSC, France). The catalyst was calcined from 25 °C to 800 °C with a heating rate 10 °/min and a gas flow rate 20 mL/min. The test atmosphere were nitrogen and air, respectively. 3. Results and Discussions 3.1 Catalyst characterization results. The XRD patterns of catalysts before and after cracking shown in Figure 4 revealed that the fresh 0.5%Ni/1%Fe-dolomite catalyst exhibited CaO diffraction peaks at 2θ = 32.2 °, 37.6 °, 53.8 °, 64.2 °, 7


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67.5 °, and 79.7 °; MgO-FeO diffraction peaks at 2θ = 42.9 °, 62.4 °, and 78.6 °; Fe2O3 diffraction peak at 2θ = 35.7 °; NiO diffraction peak at 2θ =45.1 °; and Ni-Fe alloy diffraction peak at 2θ = 26.6 °. Based on curve b, these diffraction peaks of catalyst after reaction did not changed a lot with decreasing intensity slightly. This phenomenon indicated that catalyst was not inactivated after 5 h reaction. A comparison of curves a and c showed that diffraction peaks of Ni-Fe alloy, Fe2O3 and NiO disappeared, while CaS diffraction peak appeared at 2θ = 29.3 °, and NiS diffraction peak appeared at 2θ = 45.3 °.This illustrated that H2S from sulfur-containing compounds catalytic reaction could react with 0.5%Ni/1%Fe-dolomite catalyst, especially the Ni active component, resulting in catalyst deactivation. Carbon deposited on catalyst is composed of carbon species with different C/H ratios. 28 The weight loss curve can determine the type of carbon species roughly. As seen in Figure 5, there were two weight loss peaks in the nitrogen atmosphere(curve 1), and the corresponding temperature range were 400–500°C and 600–800 °C, respectively. It is known that the carbon deposited on catalyst was mainly the heavy aromatics and coke produced during the reaction. 29,30 Therefore, in the temperature range of 400–500 °C, endothermic volatilization of heavy aromatics adsorbed on catalyst surface and in the large catalyst pores could lead to catalyst mass reduction. And heavy aromatics located in catalyst lattice structure started to volatilize above 600 °C due to the high C/H ratio and diffusion rate. Besides, the values of these two lost peaks were 11 wt% and 5 wt% respectively, indicating that heavy aromatics are mainly adsorbed in the middle and large pore channels of the catalyst. The catalyst weight loss shown Figure 5-a was 18.09 wt%, higher than that of Figure 5-b 15.98 wt%, indicating that H2S can promote the adsorption of heavy aromatics on the catalyst and increase the catalyst coke deposition. Different from curve 1, there was not only the heavy aromatics volatilization, but also the redox reactions in the air atmosphere. Curve 2 in Figure 5-a showed that the catalyst mass first rose 8



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and then falled in the first temperature range. This was because that part of Fe2O3 in catalyst reduced by CO and generated FeO during wash oil catalytic cracking reaction.31,32And then FeO was oxidized into Fe2O3 when calcined in air atmosphere, resulting in a temporary catalyst mass increase. On the other hand, CaO and NiO were poisoned by H2S into CaS and NiS during the catalytic reaction, respectively. CaS and NiS were oxidized back into CaO and NiO by O2 in TG experiment, and then resulted in a decrease in catalyst mass. The changes of the heat flow value in curve 3 fully verified the experimental phenomenon about oxidation-reduction reaction. When the temperature increased to 600 °C, the coke in the pores of the catalyst reacted with O2, resulting in a drop in catalyst mass. 3.2 Influence of different additives on natural dolomite cracking wash oil. A series of comparative experiments were carried out in order to find out the advantages of Ni and Fe additives on dolomite catalysts. Experimental conditions were reaction temperature (T) 600 °C, water/oil mass ratio 1.0: 1.0, and space velocity 300 h-1. From the products distribution shown in Figure 6-a, it can be seen that catalytic cracking had more gas yield and less cracked oil yield compared to thermal cracking. Corresponding to Figure 6-b, there were more H2, CO and CH4 generation with 0.5%Ni/1%Fe-dolomite

catalyst

than

dolomite

and

1%Fe-dolomite

catalysts.

Therefore,

0.5%Ni/1%Fe-dolomite catalyst behaved the best gas generation owing to Ni-Fe alloy, and NiO phase shown in Figure 3. The catalyst activity and resistance performance toward carbon were efficiently promoted in hydrocarbon reforming reactions.33,34As for 1%Fe-dolomite catalyst, there were more CO2 generation, and less H2 and CO generation, owing to thespecial activity of iron oxides in the water gas shift reaction. 35,36 According toTable S2, there are 11 kinds of components in the wash oil, i.e., alkanes, alkyl-substituted

aromatics,

nitrogen-containing

compounds,

9


oxygen-containing

compounds,

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naphthalene and its homologues, benzothiophene and its homologues, biphenyl and its homologues, biphenylene, fluorene and its homologues, acenaphthene. Compared to raw oil, the content of acenaphthene decreased evidently with alkanes and biphenylene content in cracked oil increased obviously. This was consistent with previous report,37 saying that acenaphthene had been cracked in reactions. The major products with the selectivity of acenaphthene were ring opening (bicyclic and monocyclic compounds), alkylation products (tricyclic compounds of C13 or lager), and dimerization products (biacenaphthene). Moreover, the contents of acenaphthene, alkanes and biphenylene were also significant between thermal cracking and catalytic cracking. It can be summarized that Ni-Fe and Ni supported on dolomite promoted the catalysts activity efficiently on aromatic hydrocarbon decomposition, especially on C-C and C-H bond cleavage.38 Based on Table S2 and Figure 6, catalytic cracking reaction through 0.5%Ni/1%Fe-dolomite catalyst got higher H/C liquid product and more hydrogen-rich gas products. It implies that Ni together with Fe additive could improve dolomite characteristics more obviously than Fe additive individually. Due to the complex composition of wash oil, model compound composed of 16.67 wt% acenaphthene and 83.33 wt% toluene was selected to clarify the cracking mechanism of wash oil. Besides, 0.5%Ni/1%Fe-dolomite catalyst was chosen as the object working in the same experimental condition with Table S2. The experimental data was exhibited in Table S3. It can be seen that acenaphthene was cracked and changed into alkanes and biphenylene mostly. And the catalytic cracking of toluene mainly result in increasing content of alkanes. The content of biphenyl changed slightly, indicating that it was probably the intermediate products during the reaction.39 3.3 Cracking of 0.5%Ni/1%Fe-dolomite catalyst over different sulfur-containing compounds. There are many kinds of sulfur-containing compounds in tar, which not only damage pyrolysis gas 10



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quality, but also do harm to catalyst activity. Thence, there was a series of comparative experiments to test

sulfur-resistance

activity

of

0.5%Ni/1%Fe-dolomite

catalyst.

1-octanethiol

(R-SH),

methylthio-benzene (R-S-R’), diphenyl disulfide (R-S-S-R’), and BT were selected to work as sulfur-containing compounds with 5wt% mixed up with wash oil respectively. Based on Figure 7-a, there was less gas yield and more solid yield compared to wash oil catalytic reaction. Besides, there were less H2 generation and more CO andCO2 generation in the corresponding gas products (Figure 7-b). According to XRD characterization results, it may due to the weakened activity of 0.5%Ni/1%Fe-dolomite catalyst with sulfur poisoning (H2S + H2 + NiO→ NiS,40CaO + H2S → CaS) and carbon deposition. Since H2S has an unshared electron pair on the electronic structure, which can easily form strong coordination bonds with the electrons of the Ni metal d orbital, reducing the adsorption and dissociation rate of the reaction molecules on the catalyst surface. 41 As seen in Table S4, the related experiment GC-MS analyses, it can be seen that 1-octanethiol and methylthio-benzene were cracked completely in cracked oil. In contrast, diphenyl disulfide was cracked partially and BT was almost no cracking. This result showed that 0.5%Ni/1%Fe-dolomite catalystbehaved different selective activities towards 1-octanethiol, methylthio-benzene, diphenyl disulfide and BT. thus, sulfur-containing compounds with simple structure(1-octanethiol, methylthio-benzene) may generated toxic gas H2S damaging the catalyst activity. On the contrary, sulfur-containing compounds (diphenyl disulfide and BT) with complex structure was not easy to undergo cleavage reaction, which made catalyst remaining better activity. In order verify this statement, the sulfur content of the catalyst was measured and shown in Table S5. It can be seen that the sulfur content of 0.5%Ni/1%Fe-dolomite catalyst after reaction decreased one by one with gradually complex structure of sulfur-containing compounds. Catalyst with 1-octanethiol gotmaximum sulfur content of 11


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0.065 wt% and catalyst with BT got minimal content of 0.005 wt%. Moreover, the contents of other compounds in Table S4 were same as that in Table S2. Thus, it can be summarized that catalytic cracking of sulfur-containing compounds did not affect the cleavage reaction of other substances. 4. Conclusions In this study, natural dolomite and modified dolomite catalysts, 0.5%Ni/1%Fe-dolomite catalyst, 1%Fe-dolomite catalyst were introduced to investigate the catalytic cracking of wash oil on a fixed-bed reactor. The advantages of Ni and Fe additives on dolomite were studied by comparing catalytic products to thermal cracking products. Besides, cracking mechanism of wash oil and the sulfur resistance ability of 0.5%Ni/1%Fe-dolomite catalyst were also discussed. Major conclusions are as follows: 0.5%Ni/1%Fe-dolomite catalyst performed better activity with more hydrogen-rich gas and higher H/C ratio of cracked oil. Ni additive together with Fe additive behaved a better activity on aromatic hydrocarbon decomposition than Fe additive separately. 0.5%Ni/1%Fe-dolomite catalyst with Ni-Fe alloy and NiO phases behaved superior stability and anti-carbon ability. H2S produced by catalytic cracking of sulfur-containing compounds could convert NiO and CaO into NiS and CaS, causing irreversible deactivation of catalyst. Furthermore, H2S can promote heavy aromatics adsorption on catalyst and increase carbon deposition. Acenaphthene in wash oil was the major cracking substances and cracked into alkanes and biphenylene mostly, with alkyl-substituted aromatics and biphenyl as the intermediate

products.

0.5%Ni/1%Fe-dolomite

catalyst

behaved

different

activity

toward

sulfur-containing functional groups with different chemical structure. Compounds with simple structure (1-octanethiol and methylthio-benzene) tended to undergo cleavage reactions and release H2S easily, but compounds with complex structure (diphenyl disulfide and BT) were not. And catalytic 12



cracking of sulfur-containing compounds had little effect on other compounds contents of cracked oil. Associated Content Supporting Information The component compositions of natural dolomite, the related GC-MS results of catalysts with different additives(0.5%Ni/1%Fe-dolomite catalyst, and 1%Fe-dolomite catalyst), the sulfur-resistance activity of 0.5%Ni/1%Fe-dolomite catalyst with 4 kinds of sulfur-containing compounds(1-octanethiol, methylthio-benzene, diphenyl disulfide, and benzo[b]thiophene). Author Information Corresponding Authors Peng Liang *Tel.: +86 13678890728; fax: +86 532 86057718; e-mail: [email protected]. ORCID: Peng Liang, 0000-0003-2808-865X. Huawei Zhang *Tel.: +86 13806399945;fax: +86 532 86057718; e-mail: [email protected]. NOTES The authors declare no competing financial interest. Acknowledgment The authors are grateful to the National Science Foundations of China (Grant No. 21376142 and Grant No. 21776164) for financial support.

Figures Caption Figure 1.Flowchart for catalysts preparation. Figure 2.GC-MS analysis of wash oil fractions. Figure 3.Schematic diagram of the fixed-bed reaction equipment. 13


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Figure 4. XRD patterns of 0.5%Ni/1%Fe-dolomite catalyst before and after reaction. Figure 5. TG patterns of 0.5%Ni/1%Fe-dolomite catalyst after reaction in different reaction conditions. Figure 6. Catalytic cracking situation between thermal cracking and catalytic cracking (300 h-1space velocity, 600 °C temperature, 1.0:1.0 water/oil ratio). Figure 7. Catalytic cracking situation of different sulfur-containing compounds (300 h-1space velocity, 600 °C temperature, 1.0:1.0 water/oil ratio).

Figure 1. Flowchart for catalysts preparation.

1: naphthalene; 2: quinoline; 3,4: 2-methylnaphthalene; 5: biphenyl; 6:2,7-dimethylnaphthalene;

7: 1,3-dimethylnaphthalene; 8: acenaphthene; 9: dibenzofuran; 10: fluorene; 11: phenanthrene

Figure 2. GC-MS analysis of wash oil fractions.

14



1: hydrogen; 2: nitrogen; 3: water; 4: raw oil; 5: preheater; 6: preheater furnace;

7: reactor furnace; 8: catalysts; 9: reactor; 10:heat exchanger; 11: condenser; 12:beaker; 13:airbag

Figure 3. Schematic diagram of the fixed-bed reaction equipment.

a: fresh catalyst; b: catalyst after reaction with wash oil; c: catalyst after reaction with wash oil and 5wt% 1-octanethiol

Figure 4. XRD patterns of 0.5%Ni/1%Fe-dolomite catalyst before and after reaction.

a: catalyst after reaction with wash oil and 5 wt% 1-octanethiol ; b: catalyst after reaction with wash oil

Figure 5. TG patterns of 0.5%Ni/1%Fe-dolomite catalyst after reaction in different reaction conditions.

15


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a: effect of additive types on the yield distribution of wash cracking products;

b: effect of additive types on generation of wash oil cracking gas-phase products

Figure 6. Catalytic cracking situation between thermal cracking and catalytic cracking (300 h-1space velocity, 600 °C temperature, 1.0:1.0 water/oil ratio).

a: effect of sulfur-containing compounds types on the yield distribution of wash cracking products;

b: effect of sulfur-containing compounds types on generation of wash oil cracking gas-phase products

Figure 7. Catalytic cracking situation of different sulfur-containing compounds (300 h-1space velocity, 600 °C temperature, 1.0:1.0 water/oil ratio).

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Study on Modification and Sulfur-Resistance Characteristics of

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