Enhanced Catalytic Performance of the FCC Catalyst with an Alumina

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Materials and Interfaces

Enhanced Catalytic Performance of FCC catalyst with Alumina Matrix Modified by Zeolite Y Structure-directing Agent Mengjie Xie, Yifang Li, Ubong Jerome Etim, He Lou, Wei Xing, Pingping Wu, Xiaohe Liu, Peng Bai, and Zifeng Yan Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b04890 • Publication Date (Web): 15 Mar 2019 Downloaded from http://pubs.acs.org on March 21, 2019

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Industrial & Engineering Chemistry Research

Enhanced Catalytic Performance of FCC catalyst with Alumina Matrix Modified by Zeolite Y Structure-directing Agent Mengjie Xiea, Yifang Lic, Ubong Jerome Etima, He Louc, Wei Xingb, Pingping Wua, Xiaohe Liua, Peng Baia,*, Zifeng Yana,* a State

Key Laboratory of Heavy Oil Processing, Key Laboratory of Catalysis CPNC, College of

Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, China b School

c

of Science, China University of Petroleum (East China), Qingdao 266580, China

Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85748 Garching Munich, Germany

* Corresponding authors. Tel: +86-532-86981812. E-mail address:[email protected] (P. Bai), [email protected] (Z. Yan)

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Abstract: The surface acid property of γ-Al2O3 has been modified by a zeolite Y structuredirecting agent (SDA). Thus modified γ-Al2O3 as a matrix material was used in fluid catalytic cracking (FCC) catalysts, and its performance of cracking vacuum gas oil (VGO) was evaluated. In comparsion with unmodified γ-Al2O3, the modified matrix material exhibited superior catalytic performance with heavy oil conversion increased by 5.64%, enhancing gasoline yield by 2.19% and LPG yield by 3.00%. Characterization results indicated that the zeolite Y SDA modification effectively introduced Si species into the framework of γ-Al2O3. The interaction between hydroxyl groups on silanol and Al-OH led to the formation of bridged hydroxyl groups (Si-OH-Al), which are the origin of medium-strength Brönsted acid sites on modified alumina matrix accounting for the enhanced catalytic performance of FCC catalysts.


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1. INTRODUCTION Up to now, fluid catalytic cracking (FCC) is still the mainstream technology of petroleum refining owing to its high economic benefits and operational adaptability according to market variations.1 A growing demand for the FCC products in the last few years, especially liquefied petroleum gas (LPG), light distillate gasoline and diesel in middle fractions, has become significantly evident. On the other hand, FCC feedstocks are gradually shifting from light oils towards heavy ones.2 These changes impose a driving force to further improve the traditional FCC catalysts. The typical FCC catalysts commonly contain zeolite Y or ultra-stable zeolite Y (USY), active matrices and binders.3 As an important matrix material and a binder for FCC catalysts, the unique texture and acidity of γ-Al2O3, suitable for conversion of large hydrocarbon molecules, have been extensively studied.4 However, the sole Lewis acid sites on calcined γ-Al2O3 make the cracking reactions susceptible to excessive hydrogen transfer, which in turn leads to high coke formation.5 In addition, the increase in acid site density is beneficial to the improvement of cracking activity, and a stronger acidity helps to improve the selectivity of gasoline.6, 7 However, it has been well-known that the acidity of γ-Al2O3 is weaker than that of zeolite or even amorphous silica-alumina (ASA).4,

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Therefore, it is desired to tune the acidity of γ-Al2O3 by surface

modification, introducing new Brönsted acid sites while reducing the amount of Lewis acidity. A common solution for modifying surface acidity of γ-Al2O3 is to introduce silicon atoms into its structure, resulting in the formation of ASA materials.9-11 It has been recognized that ASA with more moderate acidity than zeolites tends to enhance the selectivity of gasoline fractions.12-16 To date, much effort has been devoted to incorporating silicon atoms into γ-Al2O3 to create acid sites. However, under some circumstances, especially the strong acidic synthesis system with pH 0.9), implying that these two materials had large and slit shaped pores with mean diameter >7 nm and wide pore size distributions, reflecting the existence of non-uniform pores formed by agglomeration or aggregation of ASA and plate-like γ-Al2O3 particles.11, 28 The ASA agglomerates arised from neighboring ASA particles by binding of surface silanol (Si-OH).29 In addition, the isotherms of Y-12.0 and Y-12.0-7.0 show high nitrogen adsorption capacity in the range where P/P0 is higher than 0.8, implying that more interparticle mesopores existed in these materials as a result of the interparticle void spaces in the ASA agglomerates.3, 30 In contrast, less N2 adsorption in Y-1.0 and Y-1.0-7.0 suggests their low pore volumes (0.34 and 0.38 cm3/g, respectively). It can be seen from the data in Table 2 that except for the sample Y-12.0, BET surface areas of Y-1.0, Y-1.0-7.0 and Y-12.0-7.0 (343, 360, and 337 m2/g, respectively) are higher than that (271 m2/g) of γ-Al2O3. This should be attributed to the low pH value provided for the zeolite Y SDA to facilitate the formation of a highly porous ASA layer around pseudoboehmite in these three modified samples. 3.3. Surface Acidity. The Py-FTIR spectra (Fig. 3) in the region of 1700-1400 cm-1 were obtained to provide more information on Brönsted and Lewis acid sites. It can be seen that in all spectra, four bands at ~ 1445, 1577, 1596 and 1614 cm-1 corresponding to C-C stretching vibrations of pyridine molecules adsorbed onto Lewis acid sites can be observed.11 It is widely recognized that 10 ACS Paragon Plus Environment

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Lewis acid sites on alumina were derived from partially uncoordinated Al atoms, which are generated by the loss of surface hydroxyl groups upon dehydration of adjacent hydroxyl groups at high calcination temperatures. In addition, the sharp 1492 cm-1 band generally arises from both Lewis and Brönsted acid sites.5 However, two peaks centered at ~ 1547 and 1640 cm-1 generated by Brönsted acid sites protonating pyridine molecules (pyridinium ions, PyH+) are only observed on modified samples, and become more evident when the second process of pH-adjustment was applied. In other words, Brönsted acid sites can be generated by introducing zeolite Y SDA to the initial pseudoboehmite precursor. The quantity of Brönsted (1547 cm-1) and Lewis (1445 cm-1) acid sites according to calculation procedures elsewhere,31 is shown in Table 3. Generally, compared with pure γ-Al2O3, the modified samples present Brönsted acid sites with a considerable amount. It was previously reported the increase in Brönsted acid sites on modified γ-Al2O3 with silica is largely ascribed to bridged SiOH-Al,32 which is a strong evidence that the silicates- and aluminosilicates-contained zeolite Y SDA were indeed introduced into the skeleton of γ-Al2O3, and occupied the coordinatively unsaturated Al3+ sites. The amount of Brönsted acid sites in Y-12.0 and Y-12.0-7.0 synthesized at higher pH in the first process of hydrothermal treatment is higher than that in Y-1.0 and Y-1.0-7.0. This can be interpreted that Al oxo species (Al-O-Al) was dispersed homogeneously in the alkaline medium, and Si-OH groups formed from the hydrolysis of Si-O-Si bonds in the neutral or alkaline medium. Therefore, more Si-O-Al bonds would be generated by Al-O-Al condensating with SiOH in the second process of hydrothermal treatment.33 In addition, for modified γ-Al2O3 synthesized in neutral media, the amount of Lewis acid sites reduce dramatically due to the neutral synthesis system favored the interaction between silicates (aluminosilicates) and coordinatively unsaturated Al3+. Furthermore, upon adjusting the pH of reaction system from strong alkaline to 11 ACS Paragon Plus Environment


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neutral and undergoing a second hydrothermal treatment, Lewis acid sites decrease significantly, while Brönsted acid sites increase. The reason for this phenomenon is that in a strong alkaline medium, the further condensation of silicates and aluminosilicates decreased silanol concentration, leading to less free Al oxo species available for grafting by Si-OH; however, the hydrolysis of SiO-Si produced Si-OH in a neutral medium.33 As a consequence, the Brönsted to Lewis acid sites (B/L) ratio of sample Y-12.0-7.0 increase. NH3-TPD characterization was used to quantitatively determine the amount of total acid sites, nature and their strengths.24, 34 The obtained NH3-TPD profiles of all samples in the range of 50550 °C are presented in Fig. 4. As the precracking extent during catalytic cracking hydrocarbon macromolecules is mainly determined by the acidity of alumina matrix, including the quantity and strength of acid sites,23 the TPD curves were analyzed by Gaussian deconvolution method. All TPD curves were deconvoluted into four Gaussian peaks (for example, the inset in Fig. 4 shows the deconvolution result of sample Y-1.0): Peaks I and II are related to physically adsorbed NH3 arising from weak acid sites of surface OH attached to Si, whereas peak III is assigned to weak Brönsted and Lewis acid sites, medium acid sites corresponding to terminal silanol groups, peak IV is ascribed to the strong Brönsted acid sites and some Lewis ones.2, 24, 33 The total acidity, acid strength together with their distributions are summarized in Table 4. As is seen, the modification by zeolite Y SDA obviously increases the total acid concentrations of modified γ-Al2O3, except for sample Y-12.0. A significant decrease of specific surface area with less acid sites exposed, led to relatively less acid sites on Y-12.0. The acid sites of medium strength were reported to have a strong ability to crack hydrocarbon macromolecules and to achieve a high light oil selectivity.7,

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And for all modified samples, compared with the parent γ-Al2O3, the

proportion of the medium-strength acid sites increases, while both weak and strong ones decrease. 12 ACS Paragon Plus Environment

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It is noteworthy that sample Y-1.0-7.0 with the largest number of medium-strength acid sites bears the strongest acidity, which is derived from a large amount of bridged hydroxyl groups (Si-OHAl) generated through binding Si species with the Al species under such specific synthesis conditions. In addition, in comparison with unmodified γ-Al2O3, the shifting of peak positions corresponding to medium- and strong-strength acid sites to higher temperatures suggests the stronger acidity of modified samples. This fact implies the formation of new strong acid sites at the interface of γ-Al2O3 phase and zeolite Y SDA, where more interconnected pores created higher acid density and stronger acidity, compared with unmodified γ-Al2O3.35-38 Meanwhile, the evidently increased number of surface aluminum atoms resulted in the insufficiency of atomic coordination with high surface energy, leading to more chemical bonds between surface active aluminum atoms and silicon atoms.39 In addition, because the small Si radius and high charge can polarize OH to produce H+, the modification process of introduced silicon atoms could also generate stronger Brönsted acid sites.15 3.4. 27Al and 29Si MAS NMR Analysis. For each 27Al MAS NMR spectrum of pure and modified γ-Al2O3 (depicted in Fig. 5), the strong resonance signals at -7.8~ -6.1 ppm and 5.8 ~ 6.4 ppm are ascribed to the Al atoms coordinated octahedrally (AlVI (1) and AlVI (2)), and the other intense signal at 58.7 ~ 60.8 ppm to Al atoms in the tetrahedral coordinations (AlIV),40 while a very weak signal at 26.3~30.9 ppm is attributed to the five-fold coordinated Al atoms (AlV), typically as the interface species between alumina and silica-alumina.12 To reveal the relative intensities of various components and accurate isotropic chemical shifts, all spectra were simulated with Gaussian line shape using appropriate parameters (the inset in Fig. 5 shows sample Y-1.0 for example), and ratios of the aluminum atoms with different chemical environments are presented in Table 5. Compared to unmodified γ-Al2O3, the increased proportion 13 ACS Paragon Plus Environment


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of tetrahedrally coordinated Al in all modified samples suggests that the zeolite Y SDA modification and pH-adjustment method allowed silicon species to be grafted into γ-Al2O3 framework in the tetrahedrally coordinated position, which contributes to the formation of Brönsted acid sites based on that only tetrahedrally coordinated Al atoms are considered as the origin of Brönsted acidity.12, 33 In addition, aluminum species with tetrahedral environment are generally related to the proton-bonded aluminum atoms (Brönsted acid sites) that provides the ASA material surface acidity.4 As a consequence, the trend for the fraction of tetrahedrally coordinated Al follows the same trend as the change in the quantity of Brönsted acid sites. Furthermore, the AlIV/AlVI ratios increase, implying that after modification, the silicon atomswere apt to interact with tetrahedrally coordinated Al, or the addition of silicon speciesproduced more aluminum species existing in the form of tetrahedral coordination. Meanwhile, compared with that of the unmodified γ-Al2O3, the percentage of penta-coordinated aluminum species increases by 2.3% for Y-12.0-7.0 and by 6.2% for Y-1.0-7.0. It has been reported that AlVspecies are associated with strong acidity, arising from dehydration at high temperatures, which promotes the transformation of Al atoms from pentahedral coordination sites to lower-coordination centers, contributing to the enhanced acid strength of adjacent bridged -OH groups.12 29Si

MAS NMR was measured to elucidate chemical environment of silicon atoms on modified

alumina surface. The spectra in Fig. 6 indicated that the resonance at ca. -102 ~ -110 ppm may be associated with Si(OSi)4 sites or SiO2 domains.41 The intensity of this resonance is much higher on sample Y-1.0 prepared at a low pH than ones prepared at a high pH, indicating that the dispersion of Si over sample Y-1.0 is relatively lower than that over the other three samples, which agrees well with XRD results. The XRF data from Table 6 also confirm that sample Y-1.0 has the highest Si/Al ratio. When a poor dispersion of Si was achieved, the aggregation of silicon species 14 ACS Paragon Plus Environment

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would be expected to result in a non-acidic surface, which is in line with the fact that sample Y1.0 has the least amount of Brönsted acid sites among all modified samples. Peaks at -86, -89, and -92 ppm are assignable to different framework silicon Q4 environments, namely Si(OAl)4, Si(OSi)(OAl)3 and Si(OSi)2(OAl)2, respectively.40 Morever, peaks at ca. -78 and -83 ppm originate from Si(OSi)2(OH)2 and Si(OAl)3OH type silicons respectively,41 which contributes to Brönsted acid sites on modified samples. 3.5. Catalytic Cracking Performance. To further compare catalytic ability of modified and unmodified γ-Al2O3 as a matrix component for FCC catalysts, the catalytic performance of catalysts was measured in a model reaction system using a high-density feedstock (VGO). Containing a considerable amount of aromatics and resins, this feedstock was typically chosen as a raw material for MAT test.19 Catalytic results presented in Table 7 indicate that compared with catalyst using unmodified γAl2O3 as matrix, the modified γ-Al2O3 derived catalysts CatY-1.0, CatY-12.0, CatY-1.0-7.0, and CatY-12.07.0

have increased ability for cracking heavy hydrocarbons, exhibiting increased VGO conversions

and enhanced total yields,. The similar trends are observed for gasoline and LPG yields (Fig. 7). It is well recognized that the cracking of hydrocarbon through the formation of carbonium/carbenium ions can be initiated by both the Lewis and Brönsted acid sites on FCC catalysts.42, 43 This process involves C-C bond breaking in a series of β-scission and hydrogen transfer reactions, which converts macromolecular hydrocarbons into gases, light distillates and cokes.44 The Lewis acid sites are the location of coke formation because of dehydrogenation or hydrogen-transfer reactions of hydrocarbons,5, 44 while Brönsted acid sites conduce to the increased useful products yields such as gasoline and LPG. Therefore, the synergistic effects of both acid sites are favorable for facilitating the production of more gasoline and LPG by the cracking of hydrocarbons. As expected 15 ACS Paragon Plus Environment


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(Fig. S2), the increased Brönsted acid concentration on the surface of matrix is beneficial for improving the VGO conversion, and LPG yield sensibly. However, the coke yield also increases with the increased Brönsted acid concentration, which is probably ascribed to high acid density giving rise to excessive hydrogen transfer reactions.6 In addition, as Lewis acid concentration increases, the VGO conversion, gasoline and LPG yields exhibit opposite trends to those of Brönsted acid sites. Surprisingly, the Y-1.0-7.0 derived catalyst CatY-1.0-7.0 shows better catalytic performance than the Y-12.0-7.0 derived catalyst CatY-12.0-7.0 (Fig. 7), especially catalyst CatY-1.0-7.0 effectively increase the conversion of VGO from 69.83% to 75.47%, the gasoline yield from 52.34% to 54.53% and the LPG yield from 9.99% to 12.99% when compared with Catγ-Al2O3, despite the fact that Y-12.0-7.0 has more Brönsted acid sites than Y-1.0-7.0. This phenomenon coincides with the fact that matrix Y-1.0-7.0 had sufficient medium-strength acid sites for the cracking of macromolecular hydrocarbons. Furhermore, the moderate Brönsted acid sites are favorable for olefin saturation through hydrogen transfer reaction, not for secondary cracking of lower carbon molecules in gasoline/LPG.19 Therefore, an increase in the concentration of Brönsted acid sites would not result in the reduced yield of gasoline/LPG. Since coke formation is driven by the secondary cracking and condensation/polymerization reactions of product molecules, it is considered that more acid sites are considered to be responsible for higher coke yield, while good accessibility of reactants to active sites on catalyst is usually the key in reactions with diffusion limitations.33 With regards to this, the modified γ-Al2O3 derived catalysts have almost identical coke yields, which are higher than that of catalyst Catγ-Al2O3, except for CatY-1.0. A relatively low yield of coke has been obtained for CatY-1.0, which can be explained by the fact that matrix Y-1.0 had more weak acid sites, weaker medium-strength and strong16 ACS Paragon Plus Environment

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strength acid sites. In addition, by correlating textural properties with catalytic performances, the effect of pore structure is obvious. It proves to be the most effective for the pre-cracking of large molecules using the matrix Y-12.0 with the largest pore size although bearing the lowest acidity.42 In other words, the induced accessibility by large pore size can compensate the low acidity, resulting in the improved catalytic performance. Therefore, through the above analysis, the modified γ-Al2O3 synthesized by a combination of the hydrothermally treated zeolite Y SDA and pH-adjustment improved the FCC performance as compared to the unmodified matrix material. pH adjustment conducted in the secondary hydrothermal treatment and Si species introduced into the structure of γ-Al2O3 led to the generation of the medium-strength Brönsted acid sites with enhanced acidity, which account for the increased conversions and gasoline/LPG yields. 4. CONCLUSIONS In this study, we introduced silicon atoms of zeolite Y SDA into γ-Al2O3 structure through hydrothermal treatment of γ-Al2O3 combined with the pH-adjustment. As a result of the interaction of ASA components with the γ-Al2O3 phase by chemical bonding, the acidity properties of modified γ-Al2O3 samples Y-1.0-7.0 and Y-12.0-7.0, were quite different from those of pure γAl2O3. The Si-OH-Al formed by the interation of Si-OH and Al-OH, generated Brönsted acid sites and reduced Lewis acid sites in modified samples. With the modified γ-Al2O3 as matrix, the FCC catalysts performed better in catalytic cracking of VGO, attaining higher conversion of VGO (75.47% vs. 69.83%) and higher yields of gasoline and LPG (12.99% vs. 9.99% and 54.53% vs. 52.34%, respectively) as compared to the unmodified γ-Al2O3, which is attributed to the generated Brönsted acid sites with medium-strength acidity. This work not only sheds light on the effect of 17 ACS Paragon Plus Environment


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matrix acidity on catalytic performance, but also provides theoretical guidance on design of more efficient FCC catalysts for converting heavy feed into gasoline/LPG. ACKNOWLEDGEMENTS This work was financially supported by the National Key Research and Development Program of China (2017YFB030660), the Joint Funds of the National Natural Science Foundation of China and China National Petroleum Corporation (U1362202), Natural Science Foundation of China (51601223, 21206195, U1510109), the Fundamental Research Funds for the Central Universities (17CX05018, 17CX02056, 14CX02050A, 14CX02123A), Shandong Provincial Natural Science Foundation (ZR201702160196) and State Key Laboratory of Heavy Oil Processing Fund (SKLZZ-2017008). SUPPORTING INFORMATION The supporting information is available free of charge on the ACS Publications website. Pore size distributions calculated from adsorption branches of γ-Al2O3 modified by zeolite Y SDA, effect of Brönsted and Lewis acid concentration of matrices on the catalytic performance of catalysts. REFERENCES (1) Etim, U. J.; Xu, B.; Zhang, Z.; Zhong, Z.; Bai, P.; Qiao, K.; Yan, Z. Improved Catalytic Cracking Performance of USY in the Presence of Metal Contaminants by Post-Synthesis Modification. Fuel 2016, 178, 244.


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(25) Groen, J. C.; Peffer, L. A. A.; Pérez-Ramı́rez, J. Pore Size Determination in Modified Micro-and Mesoporous Materials. Pitfalls and Limitations in Gas Adsorption Data Analysis. Microporous Mesoporous Mat. 2003, 60, 5. (26) Zhu, Y.; Murali, S.; Stoller, M. D.; Ganesh, K. J.; Cai, W.; Ferreira, P. J.; Pirkle, A.; Wallace, R. M.; Cychosz, K. A.; Thommes, M.; Su. D.; Stach, E. A.; Ruoff, R. S. Carbon-Based Supercapacitors Produced by Activation of Graphene. Science 2011, 332, 1539. (27) Hartman, R. L.; Fogler, H. S. Understanding the Dissolution of Zeolites. Langmuir 2007, 23, 5482. (28) Leofanti, G.; Padovan, M.; Tozzola, G.; Venturelli, B. Surface Area and Pore Texture of Catalysts. Catal. Today 1998, 41, 211. (29) Triantafillidis, C. S.; Vlessidis, A. G.; Evmiridis, N. P. Dealuminated H-Y Zeolites: Influence of the Degree and the Type of Dealumination Method on the Structural and Acidic Characteristics of H-Y Zeolites. Ind. Eng. Chem. Res. 2000, 39, 312. (30) Zheng, J.; Zhang, X.; Zhang, Y.; Ma, J.; Li, R. Structural Effects of Hierarchical Pores in Zeolite Composite. Microporous Mesoporous Mat. 2009, 122, 266. (31) Emeis, C. A. Determination of Integrated Molar Extinction Coefficients for Infrared Absorption Bands of Pyridine Adsorbed on Solid Acid Catalysts. J. Catal. 1993, 141, 353. (32) Daniell, W.; Schubert, U.; Glöckler, R.; Meyer, A.; Noweck, K.; Knözinger, H. Enhanced Surface Acidity in Mixed Alumina-Silicas: A Low-Temperature FTIR Study. Appl. Catal. AGen. 2000, 196, 257. (33) Liu, H.; Wang, L.; Feng, W.; Cao, L.; Gao, X.; Liu, H.; Xu, C. Hydrothermally Stable Bimodal Aluminosilicates with Enhanced Acidity by Combination of Zeolite Y Precursors Assembly and the pH-Adjusting Method. Ind. Eng. Chem. Res. 2013, 52, 3620. 22 ACS Paragon Plus Environment

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(34) Shakhtakhtinskaya, A. T.; Mamedova, Z. M.; Mutallibova, S. F.; Alieva, S. Z.; Mardzhanova, R. G. TPD Study of Catalyst Surface Acidity. React. Kinet. Catal. Lett. 1989, 39, 138. (35) Zhang, Y.; Liu, Y.; Li, Y. Synthesis and Characteristics of Y-Zeolite/MCM-48 Biporous Molecular Sieve. Appl. Catal. A-Gen. 2008, 345, 78. (36) Liu, H.; Bao, X.; Wei, W.; Shi, G. Synthesis and Characterization of Kaolin/NaY/MCM-41 Composites. Microporous Mesoporous Mat. 2003, 66, 124. (37) Huo, Q.; Dou, T.; Zhao, Z.; Pan, H. Synthesis and Application of a Novel Mesoporous Zeolite L in the Catalyst for the HDS of FCC Gasoline. Appl. Catal. A-Gen. 2010, 381, 105. (38) Zheng, J.; Zhang, X.; Wang, Y.; Bai, Y.; Sun, W.; Li, R. Synthesis and Catalytic Performance of a Bi-Phase Core-Shell Zeolite Composite. J. Porous Mat. 2009, 16, 736. (39) Meng, Q.; Liu, B.; Piao, J.; Liu, Q. Synthesis of the Composite Material Y/ASA and Its Catalytic Performance for the Cracking of n-Decane. J. Catal. 2012, 290, 60. (40) Gore, K. U.; Abraham, A.; Hegde, S. G.; Kumar, R.; Amoureux, J. P.; Ganapathy, S. 29Si and 27Al MAS/3Q-MAS NMR Studies of High Silica USY Zeolites. J. Phys. Chem. B 2002, 106, 6119. (41) Cui, Y.; Liu, N.; Xia, Y.; Lv, J.; Zheng, S.; Xue, N.; Peng, L.; Guo, X.; Ding, W. Efficient Self-Metathesis of 1-Butene on Molybdenum Oxide Supported on Silica Modified OneDimensional γ-Al2O3. J. Molec. Catal. A. 2014, 394, 4. (42) Mahgoub, K. A.; Al-Khattaf, S. Catalytic Cracking of Hydrocarbons in a Riser Simulator: The Effect of Catalyst Accessibility and Acidity. Energy Fuels 2005, 19, 329. (43) Cumming, K. A.; Wojciechowski, B. W. Hydrogen Transfer, Coke Formation, and Catalyst Decay and Their Role in the Chain Mechanism of Catalytic Cracking. Catal. Rev. 1996, 38, 104. 23 ACS Paragon Plus Environment


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(44) Feng, R.; Bai, P.; Liu, S.; Zhang, P.; Liu, X.; Yan, Z.; Zhang, Z.; Gao, X. The Application of Mesoporous Alumina with Rich Brönsted Acidic Sites in FCC Catalysts. Appl. Petrochem. Res. 2014, 4, 369.


Page 25 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


List of Tables Table 1. Synthesis Conditions for γ-Al2O3 Samples Modified by Zeolite Y SDA samples

1st pH-adjustment

1st hydrothermal treatment

2nd pH-adjustment

2nd hydrothermal treatment

Y-1.0

pH adjusted from 12.0 to 1.0 by HCl solution after the addition of zeolite Y SDA

120 oC, 20 h

-

-

Y-12.0

-

120 oC, 20 h

-

-

Y-1.0-7.0

pH adjusted from 12.0 to 1.0 by HCl solution after the addition of zeolite Y SDA

120 oC, 20 h

pH adjusted to 7.0 by ammonia solution

120 oC, 24 h

Y-12.0-7.0

-

120 oC, 20 h

pH adjusted to 7.0 by HCl solution

120 oC, 24 h



Page 26 of 38

Table 2. Textural Properties of the Samples samples

SBET/(m2/g)a

V/(cm3/g)b

D/(nm)c

Y-1.0

343

0.34

3.7

Y-12.0

183

0.55

3.7, 12.9

Y-1.0-7.0

360

0.38

3.6

Y-12.0-7.0

337

0.66

3.6, 10.1

γ-Al2O3

271

0.70

10.3

a

Total surface area calculated by the standard Brunauer-Emmett-Teller (BET) equation between nitrogen relative pressure range 0.05 < P/P0 < 0.25. b

Total pore volume obtained from single point adsorption at P/P0 =0.99.

c

Pore diameter calculated from desorption branch.


Page 27 of 38


1 2 3 Table 3. Acidity of Pure γ-Al2O3 and Zeolite Y SDA Modified γ-Al2O3 Measured by Pyridine 4 Adsorption FT-IR 5 6 samples Ntotal LAS (μmol/g)a Ntotal BAS (μmol/g)b B/L ratioc 7 8 γ-Al2O3 30.38 0.00 0.00 9 10 Y-1.0 12.40 2.70 0.22 11 Y-12.0 18.31 3.90 0.21 12 13 Y-1.0-7.0 11.25 3.40 0.30 14 15 Y-12.0-7.0 11.76 4.43 0.38 16 17 a The amount of pyridine absorbed on Lewis acid sites (1445 cm-1), μmol/g. 18 19 b The amount of pyridine absorbed on Brönsted acid sites (1547 cm-1), μmol/g. 20 c The ratio of Brönsted to Lewis acid sites. 21 22 23 24 Table 4. Acidity Properties of Pure γ-Al2O3 and Zeolite Y SDA Modified γ-Al2O3 Measured 25 by NH3-TPD 26 27 weak acid sites medium acid sites strong acid sites total acid sites 28 samples Tdi (°C)a Tdi (°C) a Tdi (°C) a 29 (μmol/g) (μmol/g) (μmol/g) (μmol/g) 30 86.0 (47.5%) 127/169 44.3 (24.5%) 228 50.7 (28.0%) 322 181 31 γ-Al2O3 32 111.0 (43.2 %) 125/165 71.7 (27.9%) 228 74.3 (28.9%) 322 257 33 Y-1.0 34 Y-12.0 78.7 (44.2%) 126/165 51.8 (29.1%) 234 47.5 (26.7%) 335 178 35 36 Y-1.0-7.0 112.6 (43.8%) 128/169 91.5 (35.6%) 244 52.9 (20.6%) 363 257 37 38 Y-12.0-7.0 98.2 (42.5%) 126/166 66.8 (28.9%) 227 66.1 (28.6%) 329 231 39 a The temperature of desorption peak with maxima. 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 27 57 58 59 ACS Paragon Plus Environment 60


Page 28 of 38

Table 5. 27Al MAS NMR Data of the Different Aluminum Environment in γ-Al2O3 and γAl2O3 Modified by Zeolite Y SDA samples

AlIV

AlV

AlVI

AlIV/AlVI

δiso (ppm)

%

δiso (ppm)

%

δiso (ppm)

%

γ-Al2O3

60.74

28.6

30.83

10.6

6.38/-6.13

60.8

47.0

Y-1.0

60.53

31.5

28.13

16.0

6.08/-7.13

52.5

60.0

Y-12.0

60.43

31.3

28.88

15.1

6.02/-6.98

53.6

58.4

Y-1.0-7.0

58.88

32.0

26.33

16.8

5.81/-7.03

51.2

62.5

Y-12.0-7.0

58.78

34.0

27.03

12.9

6.18/-7.13

53.1

64.0

Table 6. The Si/Al Ratio of γ-Al2O3 Modified by Zeolite Y SDA Obtained from XRF samples

Al2O3 (wt%)

SiO2 (wt%)

Si/Al (molar)

Y-1.0

71.80

24.07

0.28

Y-12.0

76.80

21.48

0.24

Y-1.0-7.0

78.23

21.10

0.23

Y-12.0-7.0

76.90

21.44

0.24


Page 29 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 7. Catalytic Performance of Catalysts Prepared with Unmodified and Modified γAl2O3 catalysts

CatY-1.0

CatY-12.0

CatY-1.0-7.0

CatY-12.0-7.0

Catγ-Al2O3

dry gas

1.24

1.25

1.25

1.21

0.99

C3= + C4=

6.02

5.54

6.50

6.07

4.70

LPG

11.99

12.48

12.99

12.45

9.99

H2

0.08

0.06

0.07

0.07

0.04

gasoline

54.31

53.56

54.53

53.76

52.34

diesel

22.62

21.67

21.27

21.99

24.82

heavy oil

3.55

4.28

3.26

3.66

5.35

light oil yield

76.93

75.23

75.80

75.75

77.16

coke

6.29

6.75

6.69

6.92

6.51

conversion

73.83

74.05

75.47

74.35

69.83

total yield

88.92

87.72

88.79

88.21

87.15

products/wt%



Page 30 of 38

List of Figure Captions Figure 1. XRD patterns of pure γ-Al2O3 and γ-Al2O3 modified by zeolite Y SDA. Figure 2. N2 adsorption-desorption isotherms (a) and pore size distributions (b) of γ-Al2O3 modified by zeolite Y SDA. Figure 3. FT-IR spectra of pyridine adsorption on pure γ-Al2O3 and γ-Al2O3 modified by zeolite Y SDA. Figure 4. NH3-TPD profiles of γ-Al2O3 and γ-Al2O3 modified by zeolite Y SDA. Figure 5. 27Al MAS NMR spectra of γ-Al2O3 and γ-Al2O3 modified by zeolite Y SDA. Figure 6. 29Si MAS NMR spectra of γ-Al2O3 modified by zeolite Y SDA. Figure 7. Differences in the conversion, yields of gasoline and LPG using the catalyst Catγ-Al2O3 as a reference.


Page 31 of 38

List of Figures

Figure 1

 amorphous SiO2  γ-Al2O3

Y-12.0-7.0 









Y-1.0-7.0

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Y-12.0 Y-1.0

γ-Al2O3

10

20

30

40

50

60

70

2 Theta (degree)



Figure 2

Y-1.0 Y-12.0 Y-1.0-7.0 Y-12.0-7.0

400

(a)

3

Quantity Adsorbed (cm /g STP)

500

300 200 100 0 0.0

0.2

0.4

2.0

3

0.6

0.8

1.0

Relative Pressure (P/P0)

2.4

dV/dD (cm /g nm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 38

(b)

1.6

Y-1.0 Y-12.0 Y-1.0-7.0 Y-12.0-7.0

1.2 0.8 0.4 0.0 0

5

10

15

20

25

Pore Diameter (nm)


Page 33 of 38

Figure 3

1640 1614 Y-12.0-7.0 1596 1577 1547

1492

1445

Y-1.0-7.0

Reflectance (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Y-12.0

Y-1.0 γ-Al2O3

1700

1650

1600

1550

1500

1450

1400

-1

Wavenumber (cm )



Figure 4

0.03 TCD Signal (a.u.)

0.03

TCD (signal)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 38

0.02 0.01

I

II

III IV

0.00

0.02

Y-1.0

100 200 300 400 500 o

Temperature ( C)

γ-Al2O3 Y-1.0 Y-12.0 Y-1.0-7.0 Y-12.0-7.0

0.01

0.00 100

200

300

400

500

o

Temperature ( C)


Page 35 of 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5

27

Al MAS NMR Al

Y-12.0-7.0

Al

IV

Al

VI

Y-1.0

V

150 100

50 0 ppm

-50 -100

Y-1.0-7.0 Y-12.0 Y-1.0 γ-Al2O3

150

100

50

0

-50

-100

-150

ppm



Page 36 of 38

Figure 6

-86 -89 -92 -83 -78 -102 -110

29

Si MAS NMR

Y-12.0-7.0

Y-1.0-7.0

Y-12.0

Y-1.0

-20

-40

-60

-80

-100

-120

-140

-160

ppm


Page 37 of 38

Figure 7

80 70

conversion +4.00 Ref.

60

gasoline +4.22

+1.97

LPG +5.64

+1.22

+2.19

+4.49

+1.42

50 wt%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


40 30 20 +2.00

10 0 Catγ-Al2O3

CatY-1.0

+2.49

+3.00

+2.46

CatY-12.0 CatY-1.0-7.0 CatY-12.0-7.0



Page 38 of 38

For Table of Content Use Only


Enhanced Catalytic Performance of the FCC Catalyst with an Alumina

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