Sulfated Zirconia Synthesized in a One Step Solvent-Free Method for

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Sulfated zirconia synthesized in one step solventfree method for removal olefins from aromatics Jianfei Liu, Naiwang Liu, Kaiqing Ren, Li Shi, and Xuan Meng Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b01660 • Publication Date (Web): 21 Jun 2017 Downloaded from http://pubs.acs.org on June 22, 2017

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Industrial & Engineering Chemistry Research

Sulfated zirconia synthesized in one step solvent-free method for removal olefins from aromatics Jianfei Liu, Naiwang Liu, Kaiqing Ren, Li Shi, Xuan Meng* The State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, People's Republic of China *Corresponding author: Xuan Meng, E-mail: [email protected], Tel: 021-64252274

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Abstract Sulfated zirconia was synthesized by one step solvent-free method, directly mixing Zr(OH)4 and (NH4)2SO4. Whole synthesis process produces no waste water, which is environment-friendly. Synthesis factor (mole ratio of (NH4)2SO4: Zr(OH)4) is the main point to test catalytic activity. Structural properties are characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms and Inductively Coupled Plasma (ICP). Acid property is characterized by pyridine-FTIR. S Coverage (× 10-6 mol S.m-2)-Lewis acidic sites density (mmol.m-2) relationship in sulfated zirconia reveals that the generation order of Lewis acidic sites is from weak ones to strong ones. Calculation of acid property reveals the positive structural – functional relationship (WL/SL – catalytic activity). Weak Lewis acidic sites (WL) promote the activity towards removal olefins, while strong Lewis acidic sites (SL) speed up the deactivation of catalysts. The superior catalytic performance as well as environment-friendly synthesis method demonstrate that solvent-free sulfated zirconia has bright application prospects in industry. Key words: S coverage; sulfated zirconia; solvent-free; S density; alkylation; acidic density

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1. INTRODUCTION BTX, (Benzene, toluene and xylene), are fundamental chemical products in modern industry. Aromatics produced in cracking process contain trace olefins, which are active enough to damage following products. Thus it is necessary to remove olefins from aromatics products. The most commercial method to remove olefins is clay-treatment1. Their powerful absorb properties towards olefins and low cost of production make them easy to be applied in industry. However, their weak thermal stability hinders their recycle usage, and deactivated clay has serious damage towards environment. Over researches in our Lab, modified clay 2 implanted by Lewis acids such as AlCl3, ZnCl2 and CuCl2 and zeolites such as USY

3

are used for removal olefins. The

mechanism of removal olefins over these catalysts can be seen in equation below, which is one kind of alkylation reactions4. The olefin molecule is protonated by the Lewis acid sites and generates a mono- or poly- alkylbenzenium ion 5.

CH R1 CH3

R1 CH CH3

Recently, Sulfated zirconia (SZ) has also shown excellent performance towards olefin removal in aromatics 6. Due to its properties of superior acidity, sulfated zirconia is widely used in alkylation 7, 8, isomerization 9, 10, acylation 11, 12, condensation 13, 14 and esterification reactions

15, 16

. Zirconium oxide (ZrO2) possesses both acid sites and

base sites and can convert to solid acid by supporting SO42- in the inductive effect promoting by S=O bonds17,

18

. Traditional synthesis method to prepare sulfated

zirconia is an impregnation-immersion one, which dips zirconium hydroxide into ammonia sulfate or sulfuric acid followed by calcination at 650 oC

19

. The most

common raw material resource of Zr is zirconium oxychloride (ZrOCl2.8H2O), which can be transferred into zirconium hydroxide (Zr(OH)4) in mixing with ammonium hydroxide (NH3.H2O). While raw Zr in nature is in the form of azurite which includes ZrSiO3 instead of ZrOCl2.8H2O. The industrial process for ZrOCl2.8H2O purification can be simplified as following chemical equations: 3



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ZrSiO3+4NaOH=Na2ZrO3+Na2SiO3+2H2O Na2ZrO3+3H2SO4=Zr(SO4)2+Na2SO4+3H2O Zr(SO4)2+4NH3.H2O=Zr(OH)4+2(NH4)2SO4 Zr(OH)4+2HCl+5H2O=ZrOCl2+8H2O When considering industrial application, two aspects can be improved towards traditional impregnation-immersion method. (1) The step of immersing would generate plenty of wasted sulfuric acid, which is agonizing to handle solvent wastes in industry. (2) As the resource of Zr, ZrOCl2.8H2O contains unessential ions of Cl-, which is corrosive towards equipment in industry and useless towards SZ. However, what can attract attention is the third step that generalizes both Zr(OH)4 and ammonia sulfate ((NH4)2SO4). It is green and economical to mix Zr(OH)4 and (NH4)2SO4 directly for composition of sulfated zirconia instead of reproducing Zr(OH)4 by ZrOCl2.8H2O. This one step synthesis method is environment friendly for solvent-free and non-impregnation liquid waste, which completely solves the two problems before. Hence, this paper focuses on environment friendly synthesis of sulfated zirconia instead of traditional impregnation-immersion method. Meanwhile the composition in sulfated zirconia is not simply full of Zr(SO4)2. Mass fraction of S in the sulfated zirconia is about 3.5% instead of 22.6% in zirconium sulfate

20, 21

. The unsolved problem of acidic properties is related to its special

structure and connection mode between S and Zr atoms 22, 23. Then S coverage (× 10-6 mol S.m-2) on the surface of ZrO2 and its compact in acidic sites are fundamental problems in revealing acidic properties in sulfated zirconia. Acidic properties are essential factors in affecting catalytic properties of alkylation. This paper now focuses on one-step solvent-free synthesis of sulfated zirconia and is devoted in figuring out the relationship of S coverage, acidic properties and catalytic properties in sulfated zirconia. The catalytic activity of this green catalysts is reflected by conversion of olefins in aromatics and this paper is valuable in further application of this novel and environmental-friendly catalyst towards alkylation reactions and industrial process. 2. EXPERIMENTAL SECTION 4


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2.1 Preparation of catalysts One step solvent-free synthesis of sulfated zirconia (S-ZrOH) was based on Zr(OH)4 and (NH4)2SO4. By mixing these two kinds of raw materials in the mortar, the mixture turned to be solid enough to concentrate as one. The mixture were calcined in 650 oC for 3 hours in the end. Hence, 0.213, 0.163, 0.094, 0.069, 0.063 and 0.060 represented the final S density (mol S/ mol Zr) in catalysts, which were detected by ICP. The initial S density (mole ratio of (NH4)2SO4 : Zr(OH)4) in precursors were 2 : 1, 1 : 1, 0.5:1, 0.33 : 1, 0.20 : 1 and 0.14 : 1 accordingly. 2.2 Catalytic performance The aromatic hydrocarbons used in the experiments were from the catalytic reforming unit of Sinopec Shanghai Petrochemical Company. Hourly bromine index (BI) of the raw materials was about 1000 and C8-C10 long-chain aromatic hydrocarbon occupied the majority of the raw materials. The detailed components of the aromatic hydrocarbons are showed in Table 1. The process of trace removal olefins from aromatics was proceeded in a fixed-bed reaction at the temperature of 175 oC and the pressure of 1 MPa with 2ml catalysts. The liquid hourly space velocity (LHSV) was kept in 30 h-1. A Bromine Index Analyzer (LC-2) was used to analyze BI of the raw materials and hourly products. The conversion of olefins was calculated following the equation below: Conversion = ൬1 −

‫ܫܤ‬ ൰ × 100% ‫ܫܤ‬଴

BI: Hourly bromine index of the aromatic hydrocarbons in the exit. BI0: Bromine index of raw aromatic hydrocarbons in the entrance. Guiding by ASTM standard D2710-92, BI is an indicator of olefins content for its definition, which is the milligrams number of bromine consumption in 100g hydrocarbon sample. 2.3 Characterization of catalysts The structures of catalysts were characterized by X-ray diffraction (XRD) patterns. 5



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The instrument used was a Siemans D500 diffractometer with Cu Kα radiation (40kV, 100mA). The powder diffraction patterns were recorded in the step of 0.02o at a rate of 1o/min in the range from 10o to 80o. N2 adsorption-desorption isotherms of catalysts were detected by ASAP 2010 N to estimate specific pore volume and surface area at the pressure of 3 MPa. The weight of catalysts for characterization was about 0.15 g. Fourier transform infrared (FTIR) spectroscopy was detected by model magna-IR550 of Nicolet Company. Pyridine was the probe molecule, which were absorbed in 80 oC for 30min and desorbed in 200oC and 450oC for 30min respectively. Inductively Coupled Plasma (ICP) Atomic Emission Spectrometer, Varian 710-ES form Agilent Technologies, was used for analyzing content of S and Zr in catalysts. 3. RESULTS AND DISCUSSION 3.1 Catalytic activity test of commercial solid acid catalysts Catalytic activities of different commercial solid acid catalysts are showed in Figure 1. Olefins removal ability of clay is attributed to physical absorption in porous structure, thus it is not abnormal that it shows the lowest activity. ZrO2 shows low conversion towards olefins for the similar reason. In comparison of ROC, USY and S-ZrOH-0.069, they all behave high activities towards olefins at first. Conversion of USY drops quickly after 3 h reveals low stability of USY in reaction. Catalytic properties of S-ZrOH-0.069 are superior to ROC over the whole eight hours, which are the widely used catalysts for removal olefins in industry. And S-ZrOH-0.069 appears to be obviously active towards olefins in comparison of ZrO2. Hence one step solvent-free synthesis method is useful for generating solid acid catalysts towards removal olefins. Sulfated zirconia in solvent-free synthesis is not only environment friendly and easy to realize in industry, but also shows high catalytic activity towards olefins. 3.2 relationship between S density and S coverage In order to find out the optimal sulfated zirconia of solvent-free synthesis (S-ZrOH), 6


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different S density (mol S/ mol Zr) of initial precursors are taken into account. With the assistance of ICP and N2 adsorption-desorption isotherms, the final S coverage (× 10-6 mol S.m-2 catalyst) is calculated by S density and surface area of catalysts. Figure 2 reveals the relationship between S density and S coverage. It is interesting to find that the curve turns out to be S shape. S coverage increases slowly when the S density is slow, and suddenly rise in the middle of S density. At the end, the curve turns out to rise slowly again. Two points are obvious in Figure 2. The first point is near S density=0.3 mol S/mol Zr, which is called “point a”. Before point a, the S coverage is near 8 × 10-6 mol S.m-2. The S atom is not enough for connection with Zr atom, and enough Zr atom makes the connection stable. The second point is between S density= 1 and 2 mol S/mol Zr, which is called “point b”. After point b, the S coverage is over 15 × 10-6 mol S.m-2. Between point a and point b, the S coverage increase with the S density. This reflects another kind of connection between S and Zr atom has informed. After “point b”, the second connection is near the position of saturation. The more addition of S, the fewer addition of S coverage on the surface of sulfated zirconia. 3.3 Catalytic activity test of S-ZrOHs different in S densities Figure 3 reveals catalytic properties of removing olefins from aromatics in S-ZrOHs of different S densities. In Figure 3, S-ZrOH-0.213 and S-ZrOH-0.163 have the lowest conversion, which means more additions of S (after “point b”) has negative impact on catalytic properties. When zirconium composition occupied more fractions (between “point a” and “point b”), S-ZrOH-0.094 shows more catalytic activity in removal olefins than S-ZrOH-0.213 and S-ZrOH-0.163. S-ZrOH-0.069 reveals to be optimal catalyst among S-ZrOHs of different S densities. S-ZrOH-0.060, S-ZrOH-0.063 and S-ZrOH-0.069 show similar conversions, which are higher than that of S-ZrOH-0.094. Therefore, a few of S coverage in S-ZrOH is obviously effective on developing catalytic function. Figure 2 also shows the relationship between conversion and S density in S-ZrOHs. In the curve of conversion and S density, “point a” is transferred to an extreme point. This reveals that the connection between S and Zr atoms (before “point a”) is effective in improving catalytic 7



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properties of S-ZrOHs. With the increase of S, the following connections between S and Zr atoms are not functional in changing the catalytic properties of S-ZrOHs. 3.4 X-ray Diffraction (XRD) In Figure 4, XRD patterns of S-ZrOH-0.213, S-ZrOH-0.163, S-ZrOH-0.094, S-ZrOH-0.069, S-ZrOH-0.063 and ZrO2 are divided into two kinds of basic phases-one is smooth and the other one is sharp. In general condition, pure zirconia crystal appears to be in monoclinic phase. S-ZrOH-0.213 and S-ZrOH-0.163 present only tetragonal phase, while S-ZrOH-0.094, S-ZrOH-0.069 and S-ZrOH-0.063 present both monoclinic and tetragonal phase. Transformation from monoclinic phases to tetragonal phases in zirconia is determined by many factors, especially temperature, environment during heat treatment and presence of contaminants or additives

24, 25

. Hence the present of SO42- brings out more tetragonal phase in the

comparison of ZrO2 and S-ZrOH in Figure 4. And this change is occurred to surface free energy that sulfate is in lower energy in stabilizing the tetragonal phase

26

. In

Figure 4, S-ZrOH-0.213 and S-ZrOH-0.163 have more fractions of tetragonal phase than the other which coincides with surface free energy theory above. This also reveals that the connection between S and Zr atoms (before “point b”) has relationship with the formation of tetragonal phases. In the other word, the connection between S and Zr atoms (from “point a” to “point b”) plays important roles in increasing tetragonal phase and restricting monoclinic phases in S-ZrOHs, since the monoclinic-to-tetragonal ratio steadily decreases with the S increase in Figure 4. While connection between S and Zr atoms before “point a” has not obvious impact on phase. Therefore, monoclinic phase in S-ZrOHs has impact on the activity of catalysts in comparison of data in Figure 3. Figure 5 shows the XRD patterns of fresh and deactivated S-ZrOH-0.069. The deactivated S-ZrOH-0.069 is got from the fresh S-ZrOH-0.069 which has been reacted after 8 hours. In figure 5, it is obvious that deactivated S-ZrOH-0.069 has less fractions of monoclinic phase than fresh S-ZrOH-0.069. Hence the decrease of the olefins removal efficiency correlates with the disappearance of monoclinic phase. 8


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3.5 N2 adsorption-desorption isotherms N2 adsorption-desorption isotherms plots of S-ZrOH in different S densities are presented in Figure 6. With the decrease of S density in S-ZrOHs, their isotherms turn from IV to II with hysteresis changing from H2 to H3. Therefore the pore size and volume diminish with the decrease of S fraction, which shows in Table 2. This reveals the exposure of surface of zirconia in S-ZrOHs when S coverage decreasing. Hence in Figure 6, curves of S-ZrOH-0.069, S-ZrOH-0.063 and S-ZrOH-0.060 increase when the pressure is high, which indicated the existence of macro-pores. These macro-pores can be formed by ZrO2. Reduction of micro- and meso-pores leads to the decrease of surface area, which coincides with the data of pore properties in Table 2. While the pore volume and pore size of S-ZrOH-0.069, S-ZrOH-0.063 and S-ZrOH-0.060 are similar with each other, and their surface area are similar as well. These similar properties of pores can be found between S-ZrOH-0.213 and S-ZrOH-0.163. Hence the S coverage on the surface of S-ZrOHs is related to the pore properties of catalysts. The more fraction of S coverage, the more micro- and meso-pores and the more surface area are formed. 3.6 Pyridine-FTIR spectra Pyridine is an indicator for acid sites analysis, which can distinguish Brønsted and Lewis acid in catalysts. In Figure 7, Brønsted acid sites are distinguishable from Lewis acid sites by IR band positions of pyridinium ion formed on Brønsted acid sites (~1540 cm-1) and pyridine coordinated to Lewis acid sites (~1450 cm-1). And the bands at 1490 cm-1 are considered as combined interaction by both of Brønsted and Lewis acids27. At desorption temperature of 200 oC and 450 oC, bands in different sites represent total and strong amount of acid accordingly. In most cases, addition of H2O brings about a decrease in the band intensity at about 1450 cm-1 and an increase in the band intensity at 1540 cm-1 28. Hence, samples are heated for hours before pyridine adsorption. Value of acid sites can be calculated by the equations below 29: C (pyridine on B sites) =1.88IA (B) R2/W; 9



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C (pyridine on L sites) =1.42IA (L) R2/W; C = concentration (mmol.g-1 catalyst); IA (B, L) = integrated absorbance of B or L bands (cm-1); R= radius of catalyst disk (cm); W= weight of disk (mg) Hence, the area of integrated absorbance bands is related to amount of acidic sites. In Figure 7, catalysts show obvious bands at 1450 cm-1 at 200oC, which means abundant amount of Lewis acid sites are distributed on catalysts. Due to the restriction of equipment in our Lab, bands at 1540 cm-1 are noisy. Hence, Lewis acidic sites are taken into account in this paper. At 450 oC, there are no obvious bands at 1540 cm-1 in S-ZrOH-0.060, S-ZrOH-0.063 and S-ZrOH-0.069. Hence the strong Lewis acid sites remain little at 450 oC. While the other three samples (S-ZrOH-0.094, S-ZrOH-0.163 and S-ZrOH-0.213) present obvious bands at 1450 cm-1 at 450 oC, which means the existence of strong Lewis acidic sites. Table 3 shows amounts of Lewis acidic sites. Compared with these results, the amount of total acidic sites increase with the S density. When strong Lewis acidic sites and weak Lewis acidic sites distinguished with each other, it can be found that the increase of strong Lewis acidic sites is slow when S density is low, and a huge upsurge exists with the increase of S density. While the amount of weak Lewis acidic sites present the opposite trend. When S density is low, the amount of weak Lewis acidic sites increase quickly. 3.7 relationship between S coverage and acidic sites density Meanwhile, surface area of catalysts is also an essential factor to be taken into consideration in acidic property. In Figure 8 and Table 4, Lewis acidic sites density (=amount of Lewis acid sites/surface area, mmol.m-2) is compared with S coverage 26 (× 10-6 mol S.m-2 catalyst). Before “point a”, the amount density of weak Lewis acidic sites increases quickly with S coverage, and the amount density of strong Lewis acidic sites remains stable. Between “point a” and “point b”, the amount density of weak Lewis acidic sites remains stable and the amount density of strong Lewis acidic sites increases quickly with S coverage. After “point b”, both amount density of Lewis 10


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acidic sites remain stable. Compared with Figure 2, it can be concluded that with the increase of S coverage, weak Lewis acidic sites gradually generate at first (before “point a”) and then the strong Lewis acidic sites generate later (between “point a” and “point b”). The catalytic property in Figure 2 is reflected by the conversion of olefins. Before “point a”, the conversion increase with S coverage. After “point a”, the conversion drops down. Hence it reveals the importance of weak Lewis acidic sites in catalysis property. Strong Lewis acidic sites bring in deactivation towards catalysts. The amount ratio of weak Lewis acidic sites and strong Lewis acidic sites (WL/SL) is calculated in Table 4. Figure 9 shows the relationship between S coverage and WL/SL. With the increase of S coverage, WL/SL arises first, and then drops down when S coverage > 8 × 10-6 mol S.m-2. It coincides with the conclusion in Figure 8. Figure 10 shows the linear relationship between WL/SL and catalysis property. Hence S coverage, WL/SL and catalytic properties are in obvious correlation. S-ZrOH-0.069 reveals to be the optimal catalysts towards olefins for its highest WL/SL. 4. CONCLUSIONS There are three kinds of connection between S and Zr atoms in S-ZrOHs. When S coverage is low on the surface of catalysts, weak Lewis acidic sites gradually generate at first. With the increase of S coverage, strong Lewis acidic sites generate later. At last, the Lewis acidic sites density trends to be stable. For removal olefins from aromatics, weak Lewis acidic sites have positive impact, while strong Lewis acidic sites have negative impact on catalytic properties. Hence S-ZrOH-0.069 with highest WL/SL are the optimal catalysts towards removal olefins, which presents higher conversion (55.94%) than that of commercial catalysts (clay-7.11%, ROC-46.93% and USY-2.18%). The optimum condition of synthesis of solvent-free sulfated zirconia is to mix (NH4)2SO4 and Zr(OH)4 in the ratio of 0.33 : 1. The solvent-free synthesis method ensures S-ZrOH-0.069 be more environment-friendly than commercial catalysts (clay, ROC and USY).

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Nanoparticles as Efficient Heterogenous Catalysts for Solvent-Free Synthesis of Xanthenediones under Microwave Irradiation. Ind. Eng. Chem. Res. 2013, 52, 5862-5870. (19) Horowitz, F.; Michels, A. F., Analysis of dip coating processing parameters by double optical monitoring. Appl. Optics 2008, 47, C185-C188. (20) Khan, N. A.; Mishra, D. K.; Ahmed, I.; Yoon, J. W.; Hwang, J. S.; Jhung, S. H., Liquid-phase dehydration of sorbitol to isosorbide using sulfated zirconia as a solid acid catalyst. Appl. Catal., A 2013, 452, 34-38. (21) Lloyd, R.; Hansen, T. W.; Ranke, W.; Jentoft, F. C.; Schlogl, R., Adsorption-desorption equilibrium investigations of n-butane on nanocrystalline sulfated zirconia thin films. Appl. Catal., A 2011, 391, 215-224. (22) Alves-Rosa, M. A.; Martins, L.; Hammer, P.; Pulcinelli, S. H.; Santilli, C. V., Structure and catalytic properties of sulfated zirconia foams. J. Sol-Gel Sci. Techn. 2014, 72, 252-259. (23) Song, H.; Cui, H. P.; Song, H. L.; Li, F., The effect of Zn-Fe modified S2O82-/ZrO2-Al2O3 catalyst for n-pentane hydroisomerization. Res. Chem. Intermediat. 2016, 42, 3029-3038. (24) Busto, M.; Shimizu, K.; Vera, C. R.; Grau, J. M.; Pieck, C. L.; D'amato, M. A.; Causa, M. T.; Tovar, M., Influence of hydrothermal aging on the catalytic activity of sulfated zirconia. Appl. Catal., A 2008, 348, 173-182. (25) Zhao, J.; Yue, Y. H.; Hua, W. M.; He, H. Y.; Gao, Z., Catalytic activities and properties of sulfated zirconia supported on mesostructured gamma-Al2O3. Appl. Catal., A 2008, 336, 133-139. (26) Liu, N. W.; Guo, X. F.; Navrotsky, A.; Shi, L.; Wu, D., Thermodynamic complexity of sulfated zirconia catalysts. J. Catal. 2016, 342, 158-163. (27) Popova, M.; Szegedi, A.; Ristic, A.; Tusar, N. N., Glycerol acetylation on mesoporous KIL-2 supported sulphated zirconia catalysts. Catal. Sci. Technol. 2014, 4, 3993-4000. (28) Loveless, B. T.; Gyanani, A.; Muggli, D. S., Discrepancy between TPD- and FTIR-based measurements of Bronsted and Lewis acidity for sulfated zirconia. Appl. Catal., B 2008, 84, 591-597. (29) Emeis, C. A., ChemInform Abstract: Determination of Integrated Molar Extinction Coefficients for IR Absorption Bands of Pyridine Adsorbed on Solid Acid Catalysts. Cheminform. 1993, 24, 347-354.

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Figure 1. Removal olefins conversions of different solid acid catalysts.

Figure 2. Relationship between S density and S coverage. a is “point a”; b is “point 14


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b”.

Figure 3. Removal olefins conversions of S-ZrOHs of different S densities.

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Figure 4. XRD patterns of S-ZrOHs and pure ZrO2, (◆) is monoclinic phase and (■) is tetragonal phase. a is “point a”; b is “point b”.

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Figure 5. XRD patterns of fresh and deactivated S-ZrOH-0.069, (◆) is monoclinic phase and (■) is tetragonal phase.

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Figure 6. N2 adsorption-desorption isotherms of S-ZrOHs.

Figure 7. Pyridine-FTIR spectra of S-ZrOHs at 200oC and 450oC.

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Figure 8. Relationship between S coverage and Lewis acidic sites density in S-ZrOHs. a is “point a”; b is “point b”.

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Figure 9. Relationship between WL/SL and S coverage in S-ZrOHs.

Figure 10. Relationship between WL/SL and conversion in S-ZrOHs 20


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Table 1. Components of the aromatic hydrocarbons Component

Non-aromat

Toluene

ics Content (wt%)

Ethylben

p-Xylene

C9

C10

zene

0.24

0.24

7.88

+ 52.21

32.62

6.81

Error range ± 1%

Table 2. Properties of pore structure Catalysts S-ZrOH-0.213 S-ZrOH-0.163 S-ZrOH-0.094 S-ZrOH-0.069 S-ZrOH-0.063 S-ZrOH-0.060

Surface area (m2/g) 93.364 80.176 72.337 67.347 63.175 61.827

Pore volume (cm3/g) 0.272 0.211 0.153 0.111 0.104 0.103

Pore size (nm) 11.643 10.536 8.027 6.574 6.428 6.368

Error range ± 3%

Table 3. Amount of Lewis acidic sites (× 10-6 mol.g-1) Catalysts S-ZrOH-0.213 S-ZrOH-0.163 S-ZrOH-0.094 S-ZrOH-0.069 S-ZrOH-0.063 S-ZrOH-0.060

TL 50.19 43.64 31.52 25.32 19.28 15.20

SL 17.49 15.68 6.76 2.28 2.13 2.10

WL 32.70 27.96 24.76 23.04 17.15 13.10

TL-total Lewis acid, SL-strong Lewis acid, WL-weak Lewis acid, error range ± 3%

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Table 4. S Coverage (× 10-6 mol S.m-2) and Lewis acidic sites density (mmol.m-2), WL/SL and Conversion (%) Catalysts S-ZrOH-0.213 S-ZrOH-0.163 S-ZrOH-0.094 S-ZrOH-0.069 S-ZrOH-0.063 S-ZrOH-0.060

S Coverage 16.28 14.91 9.91 7.97 7.72 7.58

SDL 187.36 195.60 93.49 33.88 33.72 34.02

WDL 350.19 348.69 342.30 342.09 271.41 211.87

WL/SL 1.869 1.783 3.661 10.097 8.050 6.228

Conversion 40.15 40.92 45.46 52.94 48.79 48.39

SDL-strong Lewis acidic sites density, WDL-weak Lewis acidic sites density, WL/SL-amount ratio of weak Lewis acidic sites and strong Lewis acidic sites, Conversion-conversion of olefins after 8h, error range ± 3%

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For Table of Contents Only

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Sulfated Zirconia Synthesized in a One Step Solvent-Free Method for

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