Efficient Synthesis of Polyoxymethylene Dimethyl Ethers on Al-SBA-15

Subscriber access provided by University of Otago Library

Article

Efficient Synthesis of Polyoxymethylene Dimethyl Ethers on Al-SBA-15 Catalysts with Different Si/Al Ratios and Pore Sizes Zhenzhen Xue, Hongyan Shang, Zailong Zhang, Chunhua Xiong, Changbo Lu, and Gaojun An Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02255 • Publication Date (Web): 01 Dec 2016 Downloaded from http://pubs.acs.org on December 8, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 30

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

Energy & Fuels

Efficient Synthesis of Polyoxymethylene Dimethyl Ethers on Al-SBA-15 Catalysts with Different Si/Al Ratios and Pore Sizes Zhenzhen Xue1, Hongyan Shang1*, Zailong Zhang1, Chunhua Xiong2, Changbo Lu2 and Gaojun An2 1. College of Science, China University of Petroleum, Qingdao 266580, Shandong, P. R.China 2. Chinese People’s Liberation Army Oil Research Institute, Beijing 102300, P. R.China Key words: Polyoxymethylene dimethyl ethers, Al-SBA-15, Mesoporous molecular sieve, Acid catalysis, Product distribution, Pore size

Abstract: As a kind of excellent diesel blending component, polyoxymethylene dimethyl ethers (PODEn) have received a widespread attention. Herein, Al-SBA-15 molecular sieves with different Si/Al ratios and pore sizes were synthesized and used to investigate the catalytic performance for the synthesis of polyoxymethylene dimethyl ethers from methylal (DMM) and trioxane (TOX). X-ray diffraction (XRD), N2 adsorption-desorption, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray fluorescence (XRF) and 27

Al NMR were used to characterize the structures of obtained catalysts. Ammonia temperature-

programmed desorption (NH3–TPD) and pyridine adsorption were carried out to investigate the

ACS Paragon Plus Environment

1

Energy & Fuels

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 2 of 30

acid properties of the catalysts. Through the comparison of the catalysts with different Al contents, it was found that the relatively weak acid was more suitable for the synthesis of PODEn than the relatively strong acid in the catalytic system of Al-SBA-15. On the Al-SBA15(2)-150 catalyst which only has weak acid and with the acid amount of 0.163mmol/g, the highest TOX conversion rate and highest PODEn yield and selectivity were achieved, showing the best catalytic performance. It was seemed that the PODEn synthesis not only can be catalyzed by Brönsted acid, but also catalyzed by Lewis acid. The catalysts with strong acid and/or with a large number of acids will cause the generation of great amount of methyl formate by-product. Through the comparison of the catalysts with different pore sizes, it was found that a relative larger pore size of catalysts was beneficial for the PODEn synthesis to a certain extent under the catalysts with strong acid and/or large acid amount, but on the catalyst which had only weak acid and relative less acid amount, the change of pore size almost had no effect on the yield and selectivity of PODEn products.

1 Introduction The issues of sustainable development of environment and energy have driven the research of clean fuel. Therefore, energy technology workers have been looking for a kind of renewable alternative fuel which have rich resource, low cost, environmentally friendly, and high security performance. Polyoxymethylene dimethyl ethers(PODEn), which have the linear structure of CH3-O-(CH2-O)n-CH3(n≥2)1, are colorless or light yellow combustible liquid. Its physical and chemical properties are very similar to that of diesel oil and can be blended with diesel in any proportion. PODEn are excellent diesel blending components with high cetane number2, high oxygen content3 and without sulfur and aromatics that can achieve high efficient and clean combustion4,5 which reduce soot emission, PM emission and without changing the engine


2

Page 3 of 30

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

Energy & Fuels

infrastructure6,7. PODEn can be synthesized from the methyl end group (-CH3) provider such as methylal or methanol and the chain group (-CH2O) provider such as trioxane, paraformaldehyde, or formaldehyde deriving from the product of methanol which is based on the coal gasification technology. Catalysts play a crucial role in the process of synthesis reaction. It has been well known that the synthesis process is a kind of acid catalysis. Up to now, different types of catalysts such as ZSM-58,MCM-229, ion-exchanged resin10,11, ionic liquids12,13, Zr−Alumina14, heteropolyacids15, graphene oxide16, solid superacid17 et al were studied for the synthesis of PODEn. Li17et al found that the SO42−/Fe2O3 catalyst had a good catalytic performance for the synthesis of PODEn, they indicated that the rate of carbon chain growth and termination was vital to the PODEn production process, and trioxane dissociation process was crucial step which has been proved to have a close relationship with the acid property of the catalysts. Unfortunately, the conversion rate of TOX and selectivity of PODE2-8 were not satisfied as for SO42−/Fe2O3 catalyst. Moreover, few papers8, 17 studied the effect of catalyst acidity (including acid strength, acid amount and acid type) and catalyst pore size on the selectivity and distribution of PODEn. Therefore, there is still a lot of work to do for the study of synthesis catalysts of PODEn. SBA-15 molecular sieve has been widely studied in different catalytic fields because of the good hydrothermal stability and high surface area and variable pore sizes as well as highly ordered mesoporous system18-29. In addition, the acidic property of Al-SBA-15 can be adjusted in a relatively wide range because the aluminum can replace Si atoms in the framework to form Brönsted acid and non-skeleton structure for Lewis acid18. In this paper, mesoporous Al-SBA-15 molecular sieve with different Si/Al ratios were prepared to study the catalytic performance of PODEn, to verify the influences of acid strength and acid amounts and acid type on the yield,


3

Energy & Fuels

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 4 of 30

selectivity, product distribution and chain length. Moreover, Al-SBA-15 molecular sieve with different pore sizes were also synthesized to research the effect of pore size on the diffusion of formaldehyde monomer as well as the yield and selectivity of PODEn. 2. Experimental methods 2.1. Catalyst preparation Preparation of SBA-15. Pure silica SBA-15 materials were prepared according to the procedure provided by Chen et al30 and Zhao et al31. Three kinds of different pore sizes of SBA-15 were synthesized by different hydro-thermal treatment process with the same compositions of the reaction mixtures. Typically, 4 g P123 (Aldrich, EO20-PO70-EO20) was dispersed in 30ml of deionized water and 120 ml of 2 M HCl solution with sufficient stirring, then 9 g TEOS (Aldrich, Si(OC2H5)4) was added to the above solution drop wise. The mixtures were fully stirred for 24 h at room temperature. The remaining steps were slightly different depending on the pore size. The material with relative narrow pore size, which denoted as SBA-15(1), was prepared without any hydro-thermal treatment process. Two other kinds of silica with relative larger pore sizes, which denoted as SBA-15(2) and SBA-15(3), were treated in a Teflon autoclave for crystallization at 100 °C and 130°C for 24h, respectively. The products were all filtered, washed with deionized water, and dried at room temperature in air and then calcined at 550°C for 6 h. Preparation of Al-SBA-15. The synthesis of Al-SBA-15 was carried out by post-synthesis method as previous reports32. 2g pure silica SBA-15 we synthesized above was firstly activated at 450°C for 3h and then was dispersed in 50 mL anhydrous hexane (hexane was dried by sodium) containing aluminum isopropoxide, the amounts of aluminum isopropoxide were 2.720, 0.680, 0.170, 0.068, 0.045 and 0.034g corresponding to the Si/Al ratio of 2.5, 10, 40, 100, 150, 200, respectively. The mixture was stirred at room temperature for 12h and then was


4

Page 5 of 30

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

Energy & Fuels

filtered, washed by anhydrous hexane and calcined at 550°C for 6 h. The catalysts were denoted as Al-SBA-15(n)-X with “n” standing for 1, 2 or 3 and “X” referring to the Si/Al ratio. 2.2. Catalyst characterization X-ray diffraction (XRD) was tested on an X’Pert Pro MPD equipment (Panalytical, NLD) with CuKα radiation. The scan range was set between 0.5°to 5°for small angle measurements. N2 adsorption-desorption experiments were carried out on a TriStar II instrument (micromeritics, USA) using nitrogen as adsorption agent at −196◦C. The specific surface areas were calculated according to the BET equation and the pore volumes were obtained from the BJH desorption cumulative volume of pores. The average pore sizes were obtained from the BJH desorption. Scanning electron microscope (SEM) images were observed on a FEI Quanta200 apparatus. Transmission electron microscopy (TEM) images were obtained on a JEM2100 microscope operated at 200 kV. X-ray fluorescence (XRF) was carried out on a PANalyticalaxios instrument to determine the Si/Al ratio of the catalysts. The solid state NMR spectra were detected on a MSL 300 NMR spectrometer (Bruker, GER) with resonance frequencies of 104.3 MHz for 27Al detection. Ammonia temperature-programmed desorption (NH3–TPD) was carried out on a Micromeritics RS 232 instrument. 200 mg samples were firstly treated for dehydration by heating to 500◦C at a rate of 10 ◦C min-1, and held at the same temperature for 0.5 h under Helium flow. After cooling down to 343 K, the gas circuit was changed to ammonia and kept for 30 min to complete the adsorption process of ammonia. The physical adsorption of ammonia was


5

Energy & Fuels

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 6 of 30

desorbed by purging the sample with Helium for 1 h, and subsequently the sample was heated to 700◦C at a rate of 10 ◦C min−1 under Helium flow. The adsorption of pyridine was detected on a DRIFTS chamber (Thermo fisher Nicloet-6700, USA). The catalysts were calcined at 300◦C for 3h under vacuum for dehydration treatment and adsorbed pyridine for 12h at room temperature and then dried at 150◦C for 2h to remove physical adsorbed pyridine. The blank samples were treated under the same conditions except for the process of pyridine adsorption to insure the accuracy of the analysis. The quantitative method for the calculation of Brönsted acid and Lewis acid was based on the literature33. 2.3. Catalysis performance analysis The reactions were carried out in a 0.5-L stirred autoclave reactor. The reaction conditions were set as follows: 100◦C for temperature, 1.0MPa for pressure, 1:1 for the DMM/CH2O molar ratio, 60min for reaction time, 2wt% for catalyst loading and 200 rpm/min for stirring speed. Before starting the reaction, the air inside the reactor was replaced by nitrogen. In the initial stage, the pressure of the reactor was set about 0.6-0.7MPa, due to a certain autogenous pressure with the increasing temperature. Synthetic products were analyzed by Agilent 7820 gas chromatograph. An Agilent HP-5 capillary column (30m×0.32mm×0.25µm) with a FID detector was used. Internal standard method was used as quantitative methods and n-heptane was used as internal standard substance. Formaldehyde was analyzed via titration by the sodium sulfite method34. The conversion of DMM (XDMM) and TOX (In terms of formaldehyde monomer, XCH2O) and yield of PODEn and selectivity of PODEn were determined by the following expressions:

XDMM =

mDMM, feed − mDMM , product ×100% mCH 2O , feed


6

Page 7 of 30

XCH 2 O =

mCH 2 O , feed − mCH 2 O , product × 100% mCH 2 O , feed

YPODEn =

m PODEn , product × 100% m CH 2 O + DMM , feed

SPODEn =

mPODEn × 100% ∑ mPODEn n＞1

3. Results and discussions 3.1. Structures of the catalysts The typical small angel X-ray diffraction patterns of pure silica SBA-15(n) and Al-SBA-15(2) with different Si/Al ratios are shown in Fig.1. The diffraction pattern of pure silica SBA-15(n) with different pore sizes all show three peaks in the range of 0.5°~2.0°, corresponding to (100), (110), (200) diffraction planes of hexagonal symmetry which are in agreement with the presence of a two-dimensional hexagonal P6 mm structure with a large unit-cellparameter35. Three obvious diffraction peaks also can be found in all Al-SBA-15(2) catalysts, indicating that their pristine order structure is not changed by the introduction of aluminum to SBA-15(2) catalysts. SBA-15(1) SBA-15(2) SBA-15(3) Al-SBA-15(2)-2.5 Al-SBA-15(2)-10 Al-SBA-15(2)-40 Al-SBA-15(2)-100 Al-SBA-15(2)-150 Al-SBA-15(2)-200

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

Energy & Fuels

0.9

1.2

1.5 1.8 2 Theta(°)

2.1

2.4

Fig.1 XRD patterns of pure SBA-15 silica with different pore sizes and Al-SBA-15(2) with different Si/Al ratios


7

Energy & Fuels

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 8 of 30

The nitrogen adsorption-desorption isotherms and pore size distribution of SBA-15(n) and AlSBA-15(2) are shown in Fig.2. SBA-15(n) and Al-SBA-15(2) samples all belong to type IV isotherm with H1 hysteresis capillary at 0.50 ＜ P/P0 ＜ 0.85 which are associated with the presence of mesoporous structure35, and through the different hydrothermal treatment process, the pore size distribution is obviously different. It can be seen form Table 1 that the average pore size of pure silica SBA-15(1), SBA-15(2) and SBA-15(3) are 4.68, 5.70 and 7.95nm, respectively, and all of the materials have relative large specific surface area. It should be noted that, the introduction of aluminum leads to the decrease of specific surface area and pore volume, and the decrease amplitude will increase with the increasing of aluminum content, indicating that the introduction of aluminum causes to a certain degree of hole blockage (Table.1). This decrease in the specific surface area may be caused by the formation of aluminum oxide species, which has been proved by SEM and TEM characterization. Table 1 The physical properties of the catalysts.

Catalyst

a

Si/Ala

SBETb

Vpb

Dpb

m2g-1

cm3g-1

nm

SBA-15(1)

~

491

0.81

4.68

SBA-15(2)

~

747

1.04

5.70

SBA-15(3)

~

765

1.09

7.95

Al-SBA-15(2)-2.5

3.7

485

0.79

5.97

Al-SBA-15(2)-10

9.1

509

0.84

5.92

Al-SBA-15(2)-40

36.5

589

0.90

5.88

Al-SBA-15(2)-100

91.2

639

0.95

5.82

Al-SBA-15(2)-150

134.6

658

0.97

5.76

Al-SBA-15(2)-200

175.4

685

1.01

5.72

Detected by XRF


8

Page 9 of 30

b

SBET: specific surface area; Vp: Pore volume; Dp: Pore diameter Al-SBA-15(2)-200

a Quanitity Adsorbed (cm3g-1)

Al-SBA-15(2)-150 Al-SBA-15(2)-100

Al-SBA-15(2)-40 Al-SBA-15(2)-10 Al-SBA-15(2)-2.5 SBA-15(3) SBA-15(2)

SBA-15(1)

0.0

0.5

Pore Volume(cm3g-1)

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

Energy & Fuels

0.2

0.4 0.6 0.8 Relative Pressure(P/P0)

b

1.0

1.2

SBA-15(1) SBA-15(2) SBA-15(3) Al-SBA-15(2)-2.5 Al-SBA-15(2)-10 Al-SBA-15(2)-40 Al-SBA-15(2)-100 Al-SBA-15(2)-150 Al-SBA-15(2)-200

0.4 0.3 0.2 0.1 0.0 3

6

9 Pore Diameter(nm)

12

15

Fig.2 N2 adsorption-desorption isotherms (a) and pore size distribution (b) of SBA-15(n) and AlSBA-15(2) The 27Al MAS NMR spectra of the Al-SBA-15(2) catalysts are shown in Fig.3. Two obvious characteristic peaks can be seen in each catalyst, the resonance peak at 50ppm corresponds to aluminum species in tetrahedral coordination, which indicates that Al species have been entered in the framework of SBA-15. The resonance peak at 0ppm corresponds to octahedral aluminum species36,37. With the increase of Si/Al ratio, the peak at 0ppm decreases, which shows that the


9

Energy & Fuels

aluminum atom is more easily accessible into the skeleton structure with the decrease of the aluminum content. Thus more Brönsted acid sites are formed.

Al-SBA-15(2)-150

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

Page 10 of 30

Al-SBA-15(2)-100

Al-SBA-15(2)-40

Al-SBA-15(2)-2.5

200

150

100

50 0 -50 -100 Chemical shift(ppm)

-150

-200

Fig.3 27Al MAS NMR spectra of Al-SBA-15 The TEM images of SBA-15 and Al-SBA-15 are given in Fig.4. The TEM images of SBA15(2) and Al-SBA-15(2)-10 and Al-SBA-15(2)-100 all show well-ordered hexagonal arrays of mesopores indicating a kind of two dimensional hexagonal (p6mm) structures with uniform pore size, which is in good agreement with the XRD results. This confirms that the two dimensional hexagonal (p6mm) structures are not changed because of the introduction of aluminum species. The large pores (about 5.90nm) can be clearly seen in the TEM images, which is in accordance with the N2 adsorption-desorption analysis. In addition, some small dispersed particles can be found in the TEM images of Al-SBA-15, showing the presence of Al2O3 particles. It can be seen from the SEM image (Fig.5) that the SBA-15 sample exhibits a typical rod-like morphology with good long range order structure. Al-SBA-15(2)-10 catalyst shows a


10

Page 11 of 30

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

Energy & Fuels

similar morphology and some Al2O3 particles are well dispersed on the surface of material with no agglomeration observed. b

a

c

Fig.4 TEM images of (a) SBA-15(2) (b) Al-SBA-15(2)-10(c) Al-SBA-15(2)-100

b)

a)

Fig.5 SEM images of (a) SBA-15(2) (b) Al-SBA-15(2)-10 3.2. Acidities of the catalysts


11

Energy & Fuels

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 12 of 30

The temperature programmed desorption of ammonia (NH3-TPD) is carried out to determine acid properties of the catalysts. NH3-TPD profiles of Al-SBA-15(2) with different Si/Al ratio are shown in Fig.6. It can be seen from the figure that the acidity of the catalyst increases obviously with the increase of aluminum content. Al-SBA-15(2)-2.5 and Al-SBA-15(2)-10 have two obviously peaks at about 151◦C and 451◦C, corresponding to the desorption of NH3 from the weak and strong acid sites, respectively, while the NH3-TPD profiles of catalysts from Al-SBA15(2)-40 to Al-SBA-15(2)-200 have only one peak at 151◦C which indicating to the desorption of NH3 from the weak acid sites38. The amounts of acid sites are shown in Table 2, it can be seen from the data that Al-SBA-15(2)-2.5 has the highest acid amount which reached 0.435mmol/g, and the total acid amounts also decrease with the increase of Si/Al ratio. The pyridine adsorption measured by IR spectroscopy is used to investigate the types of acid sites of Al-SBA-15 catalysts. IR spectra of pyridine adsorbed on Al-SBA-15(2) with different Si/Al ratios are shown in Fig.7. The peaks at 1455 and 1623 cm-1 attribute to pyridine adsorbed on the Lewis acid sites and the peaks at 1547 and 1640 cm-1 attributes to pyridine adsorbed on the Brönsted acid sites39. All of the catalysts we prepared have both Brönsted acid and Lewis acid, and the proportion of Lewis acid amounts is much higher than Brönsted acid, probably because of the formation of alumina particles on the catalyst surface. With the increase of Si/Al ratio, the proportion of Brönsted acid increases, which is also verified by

27

Al NMR data as

shown in Figure 6. It is well known that PODEn synthesis is a kind of acid catalytic reaction. So, the study of the influence of acid strength and acid type (Brönsted acid and Lewis acid) and acid amounts on the methylal and trioxane conversion rate as well as the competitive reaction of main products and by-products is of high research value.


12

Al-SBA-15(2)-2.5 Al-SBA-15(2)-10 Al-SBA-15(2)-40 Al-SBA-15(2)-100 Al-SBA-15(2)-150 Al-SBA-15(2)-200

100

200

300 400 T(°C)

500

600

Fig.6 NH3-TPD profiles of Al-SBA-15(2)-2.5, Al-SBA-15(2)-10, Al-SBA-15(2)-40, Al-SBA15(2)-100, Al-SBA-15(2)-150 and Al-SBA-15(2)-200

Al-SBA-15(2)-200 Al-SBA-15(2)-150

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

Energy & Fuels

Intensity(a.u.)

Page 13 of 30

Al-SBA-15(2)-100 Al-SBA-15(2)-40 Al-SBA-15(2)-10 Al-SBA-15(2)-2.5

1650

1600 1550 1500 Wave number(cm-1)

1450

Fig.7 FT-IR spectra of pyridine desorption of Al-SBA-15 Table 2 Acid properties of the catalysts Amount of acid sites, mmol g-1

catalyst Total

Brönsted

Lewis

Al-SBA-15(2)-2.5

0.435

0.035

0.400

Al-SBA-15(2)-10

0.246

0.025

0.221


13

Energy & Fuels

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 14 of 30

Al-SBA-15(2)-40

0.207

0.028

0.179

Al-SBA-15(2)-100

0.188

0.064

0.124

Al-SBA-15(2)-150

0.163

0.077

0.086

Al-SBA-15(2)-200

0.112

0.055

0.057

3.3. Catalytic performance 3.3.1 Effect of Si/Al ratio on the catalytic performance The Al-SBA-15(2) catalysts with the middle pore size are chosen to evaluate the effect of Si/Al ratio on the catalytic performance. The conversion rate of DMM and TOX and the yield and selectivity of the products under the catalysis of Al-SBA-15(2) catalysts with different Si/Al ratio are shown in Table 3. There is great influence of Si/Al ratio on the conversion rate of DMM and TOX and the yield of PODE2-8. It can be found that the conversion rate of DMM and TOX and the yield of PODE2-8 reach maximum value of 48.44%, 92.66% and 56.04% respectively when the Si/Al ratio increases from 2.5 to 150. However, when Si/Al ratio further increases to be 200, the DMM and TOX conversion rate and the yield of PODE2-8 is only 28.99%, 34.41% and 26.29% respectively. Fortunately, the selectivity of the by-product methyl formate decreases from 10.53% to 1.03% with the increase of Si/Al ratio from 2.5 to 150. So, the catalyst with Si/Al ratio of 150 has the best catalytic performance for PODEn synthesis. Table 3 Catalytic activity of catalysts with different Si/Al ratios

Catalyst

Conversion,%

Selectivity of the products,% a

a

Yield of PODE2-8,%

DMM

TOX

MeOH

MF

FA

PODE2-8

Al-SBA-15(2)-2.5

38.33

88.53

1.32

10.53

0.47

87.68

45.08

Al-SBA-15(2)-10

42.10

89.65

0.73

7.27

0.43

91.57

47.05

Al-SBA-15(2)-40

45.20

90.32

0.54

5.34

0.42

93.70

51.49


14

Page 15 of 30

Al-SBA-15(2)-100

45.55

92.43

0.42

3.34

0.39

95.85

54.59

Al-SBA-15(2)-150

48.44

92.66

0.37

1.03

0.41

98.19

56.04

Al-SBA-15(2)-200

28.99

34.41

0.35

0.95

0.47

98.23

26.29

a

MF, methyl formate; FA, formaldehyde

Reaction conditions: n (DMM)/n (CH2O) =1; catalyst loading: 2%; 100°C; 60min; 1MPa. 100 100 80 Selectivity(%)

80

selectivity of PODEn conversion rate of TOX conversion rate of DMM selectivity of MF

60

40

60

20

conversion rate(%)

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

Energy & Fuels

40

0 0.10

0.15

0.20 0.25 0.30 0.35 0.40 acid amount (mmol g-1)

0.45

Fig.8 The influence of acid amount on the conversion rate of TOX and DMM and products distribution There is a close relationship between Si/Al ratio and acid strength and acid amount and acid type of the Al-SBA-15 catalysts. The influence of acid amount on the conversion rate of TOX and DMM and products distribution is presented in Fig.8. It can be seen that the selectivity of PODEn and the conversion rate of TOX decrease with the increases of acid amount. However, the selectivity of by-product methyl formate increases with the increase of acid amount, under the catalysis of Al-SBA-15(2)-2.5, the selectivity of methyl formate is 10 times higher than that of Al-SBA-15(2)-150. In order to improve the selectivity of PODEn and the conversion rate of TOX, meanwhile suppresses the formation of by-product methyl formate, the reaction mechanism of PODEn and by-product methyl formate formation mechanism should be discussed. In the acidic environment, trioxane firstly adsorbs on the acid sites for ring-opening reaction to


15

Energy & Fuels

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 16 of 30

generate formaldehyde monomer, and then PODEn are generated by the condensation reaction of formaldehyde monomer and methylal, while methyl formate is formed by two molecules of formaldehyde in a Tischenko reaction40(Scheme 1). The depolymerization rate of trioxane, which determined by the acid property of catalysts, plays a key role on the selectivity of main products and by-products. The greater of the acid strength and the more acid amounts of the catalysts, the faster of the depolymerization rate of trioxane. When the depolymerization rate of trioxane is far greater than its condensation rate with methylal, the competitive reaction of the by-product methyl formate formation will be greatly promoted. This explains why a large number of methyl formate is generated under the catalyst with the lowest Si/Al ratio of 2.5 which has both weak and strong acid sites and has the highest acid amount of 0.435mmol/g. With the decrease of acid strength and acid amounts, the depolymerization rate of formaldehyde will slow down, thus the selectivity and yield of PODE2-8 are both increase. On the contrary, the byproduct methyl formate formation rate is greatly suppressed. In case of this PODEn synthesis system, the experimental data indicates that acid strength and acid amounts of catalysts should be in an appropriate range, and the formation of PODEn requires relatively weak acid sites in the surface of Al-SBA-15 mesoporous molecular sieve.

: Refers to the pore channel of catalyst : Refers to acid sites Scheme 1 Schematic diagram of reactions in catalyst channel


16

Page 17 of 30

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

Energy & Fuels

As a typical acid catalytic reaction, the effect of acid type on the PODEn synthesis is worth to be discussed. Zhang14et al reported that untreated parent γ-Al2O3 catalyst, which had only Lewis acid site, can catalyze the synthesis of PODEn. Meanwhile, Amberlyst 36 and Amberlyst 4641 and NKC-911 macroporous cation exchange resins, which had only strong Brönsted acid site, also had very good catalytic activity on the PODEn synthesis, indicating that the PODEn synthesis can be catalyzed by Brönsted acid independently. In this paper, the pyridine-IR adsorption results have proved that all of the catalysts we prepared have both Brönsted acid and Lewis acid, and the proportion of Lewis acid amounts is much higher than Brönsted acid on the surface and channel of Al-SBA-15 catalysts. It is suggested that the PODEn synthesis reaction can probably be catalyzed by Lewis acid independently in the Al-SBA-15 catalysts. More reasonably, the PODEn synthesis reaction may be not only can be catalyzed by Brönsted acid, but also can be catalyzed by Lewis acid. In fact, it is uncertain that whether there is a synergistic effect between Brönsted acid and Lewis acid on the PODEn synthesis process. The effect of acidic property of Al-SBA-15 on the product distribution and chain length or polymerization degree is shown in Fig.9. When the Si/Al ratio increases, the selectivity of PODE2 decreases firstly and then increases while the selectivity of PODE3-10 increases firstly and then decreases on the contrary. According to the reaction mechanism, this reaction is a kind of cascade series reaction, DMM reacts with monomer formaldehyde to generate PODE2, and PODEn-1 react with formaldehyde to generate PODEn11, as seen in Eq.(1-3). Product distribution conforms to the Flory rule. Both the decomposition of TOX and the chain growth reaction are equilibrium process12,42. The concentration of formaldehyde in the pore of catalysts determines the product distribution of PODEn to a certain extent. To be brief, when the condensation reaction rate is slower than the rate of trioxane decomposition, there will be predominantly


17

Energy & Fuels

higher methyl formate content in the products as evidenced by Al-SBA-15(2)-2.5, therefore inhibiting the chain growth reaction of PODEn. On the other hand, when the condensation reaction rate is faster than the rate of trioxane decomposition, there are mainly products with shorter chain length as proved by Al-SBA-15(2)-200. When the depolymerization rate and PODEn chain growth rate is basically the same, the selectivity and yield of PODEn will reach the maximum value as evidenced by Al-SBA-15(2)-150.

(CH2O)3

H+

3CH2O (1)

CH3OCH2OCH3

+

H+

CH2O

CH3O(CH2O)n-1CH3 + CH2O

CH3O(CH2O)2CH3(2)

H+

CH3O(CH2O)nCH3(3)

70 60 Selectivy of products(%)

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 18 of 30

Al-SBA-15(2)-2.5 Al-SBA-15(2)-10 Al-SBA-15(2)-40 Al-SBA-15(2)-100 Al-SBA-15(2)-150 Al-SBA-15(2)-200

50 40 30 20 10 0 0

1

2

3

4

5

6

7

8

9

10

n of PODEn

Fig.9. The selectivity of products with different polymerization under the catalysis of different Si/Al ratios 3.3.1 Effect of pore size on the catalytic performance As for Al-SBA-15 mesoporous molecular sieve, the influence of the inner diffusion of PODEn products and DMM and TOX in the channel of the catalysts on the selectivity of PODEn and the side reaction of MF must be taken into account. Li17 et al suggested that the reaction results were


18

Page 19 of 30

not affected by the pore sizes of the catalysts, meaning that the reaction rate was not limited by the internal pore diffusion as for SO42 /Fe2O3-SiO2 （with pore size range from 4.3 to 25.7nm） −

solid acid catalysts. On the contrary, Burger41 et al discussed the differences of two kinds of resin catalysts in the formation of by-product methyl format, and they thought that the different behavior can be explained according to their different degree of sulfonation. Amberlyst 46（with average pore size of 23.5nm44 ） , was sulfonated only on the surface of catalysts while Amberlyst 36（with average pore size of 24nm43）was not only sulfonated on the surface of catalyst but also sulfonated inside of the pores. Under the catalysis of Amberlyst 36, about 1-2 mass% methyl formate were generated while under the catalysis of Amberlyst 46, the by-product methyl formate could not be detected at any time. 60 55 Yield of PODE2-8(%)

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

Energy & Fuels

50 45 pore size of 4.68nm pore size of 5.70nm pore size of 7.95nm

40 35 30 25 2.5

10

40 100 Si/Al ratio

150

200

Fig.10. The yield of PODE2-8 under the catalysis of different pore sizes with Si/Al ratio from 2.5 to 200


19

Energy & Fuels

100 98 Selectivity of PODE2-8(%)

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 20 of 30

96 94 92

pore size of 4.68nm pore size of 5.70nm pore size of 7.95nm

90 88 86 84 2.5

10

40 100 Si/Al ratio

150

200

Fig.11. The selectivity of PODE2-8 under the catalysis of different pore sizes with Si/Al ratio from 2.5 to 200 In order to study the effect of pore size on the yield and selectivity of the products, SBA-15 material with three different pore sizes are prepared, and the corresponding modification by aluminum incorporation are carried out. The yield and selectivity of PODE2-8 under the catalysis of different pore sizes are shown in Fig.10 and Fig.11, respectively. It can be seen that the catalysts with different pore sizes show the same changing tendency that the yield of PODEn first increases and then decreases with the increase of Si/Al ratio, and the yield reaches the maximum value when the Si/Al ratio is 150. The selectivity of PODEn first increases and then remains basically unchanged with the increase of Si/Al ratio, and the selectivity reaches the miximum when the Si/Al ratio is 150 as well. By comparing the catalytic performance of the three kinds of catalysts with different pore sizes, it is found that the yield and selectivity of PODE2-8 increase with the increase of pore sizes in the Si/Al ratio range from 2.5 to 100, and within this Si/Al ratio range, Al-SBA-15(3) catalysts which have the largest pore size (7.95nm) show the best catalytic performance. When the Si/Al ratios are 150 and 200, the yield and selectivity of PODE2-8 almost have no change with the change of pore sizes.


20

Page 21 of 30

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

Energy & Fuels

It can be seen from the experimental results that the pore size can influence the PODEn synthesis to a certain extent under the catalysts with strong acid and/or large acid amount. By discussing the influence of the acidity of the catalyst on the catalytic performance, we know that the great acid strength and high acid amounts of the catalysts are in favor of the depolymerization rate of trioxane, when the depolymerization rate of trioxane is far greater than its condensation rate with methylal, the enrichment of formaldehyde monomer on the acidic sites will lead to the formation of a large number of by-product methyl formate. Under these circumstances, a relative larger pore size is more conducive to the diffusion of formaldehyde monomer compared with relative smaller pore size, thereby inhibiting the formation of byproduct methyl formate. However, the yield and selectivity of PODEn almost have no change with the change of pore sizes under the catalysts with relatively less acid amount. That is because when the depolymerization rate and PODEn chain growth rate is basically the same, or the condensation reaction rate become more faster than trioxane decomposition rate, formaldehyde monomer will not accumulate in acidic sites, so the influence of pore size on the reaction system will be very small. Based on the discussion above, we know that the optimal Si/Al ratio is 150, in which three catalysts with different pore sizes all show almost the same and best catalytic performance. 4 Conclusions Herein, Al-SBA-15 catalysts with various Si/Al ratios and pore sizes were successfully prepared for the synthesis of PODEn from DMM and TOX. In the study of the effect of different Si/Al ratios on the catalytic performance, it was found that the Al-SBA-15(2)-150 catalyst which had only weak acid sites and with the acid amounts of 0.163mmol/g showed the best catalytic performance, the conversion rate of DMM and TOX and the yield of PODE2-8 reached


21

Energy & Fuels

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 22 of 30

maximum value of 48.44%, 92.66% and 56.04% respectively. The experimental data indicated that acid strength and acid amounts of catalysts should be in an appropriate range, and the formation of PODEn required relatively weak acid sites in the surface of Al-SBA-15 mesoporous molecular sieve as proved by Al-SBA-15(2)-150. It was seemed that the PODEn synthesis not only can be catalyzed by Brönsted acid, but also can be catalyzed by Lewis acid. The trioxane dissociation rate and condensation reaction rate which determined by the acid strength and acid amounts had a decisive effect on the selectivity of main products and by-products and the distribution and chain length of PODEn. Through the adjustment of the Si/Al ratio from 2.5 to 150, the selectivity of by-product methyl formate was suppressed from 10.53% to 1.03%. It was showed that the catalysts with strong acid and/or with a large number of acids will cause the generation of great amount of by-product methyl formate. In the study of the effect of different pore sizes on the catalytic performance, it can be seen that under the catalysts with strong acid and/or large acid amount in the Si/Al ratio range from 2.5 to 100, Al-SBA-15(3) catalysts which had the largest pore size(7.95nm) showed the best catalytic performance, it can be concluded that the catalysts with relative larger pore size were in favour of the diffusion of formaldehyde monomer, thus inhibiting the production of methyl formate, and improving the yield and selectivity of PODEn accordingly. However, under the catalysts with weak acid and/or less acid amount in the Si/Al ratio of 150 and 200, the pore size of catalysts almost had no effect on the PODEn synthesis. When the Si/Al ratio was 150, the three catalysts with different pore sizes all showed almost the same and best catalytic performance.

■ AUTHOR INFORMATION


22

Page 23 of 30

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

Energy & Fuels

Corresponding Author *E-mail: [email protected] ACKNOWLEDGMENTS This work was supported by the National Key Technology R&D Program (No.2013BAB11B03). ■ ABBREVIATIONS DMM, Methylal; TOX, trioxymethylene; MeOH, methanol; FA, formaldehyde; MF, methyl formate ■ REFERENCES 1.

Boyd., R. H., Some physical properties of polyoxymethylene dimethyl ethers. Journal of

Polymer Science 1961, 50 (153), 133-141. 2.

Burger, J.; Siegert, M.; Ströfer, E.; Hasse, H., Poly(oxymethylene) dimethyl ethers as

components of tailored diesel fuel: Properties, synthesis and purification concepts. Fuel 2010, 89 (11), 3315-3319. 3.

Lei, Y. S., Q.; Chen, Z.; Shen, J., Theoretical Calculations on the Thermodynamics for

the Synthesis Reactions of Polyoxymethylene Dimethyl Ethers. Acta Chimica Sinica 2009, 67 (8), 767-772. 4.

Liu, H.; Wang, Z.; Wang, J.; He, X.; Zheng, Y.; Tang, Q.; Wang, J., Performance,

combustion and emission characteristics of a diesel engine fueled with polyoxymethylene dimethyl ethers (PODE3-4)/ diesel blends. Energy 2015, 88, 793-800.


23

Energy & Fuels

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

5.

Page 24 of 30

Liu, J.; Wang, H.; Li, Y.; Zheng, Z.; Xue, Z.; Shang, H.; Yao, M., Effects of

diesel/PODE (polyoxymethylene dimethyl ethers) blends on combustion and emission characteristics in a heavy duty diesel engine. Fuel 2016, 177, 206-216. 6.

Fleisch, T. H. S., R. A., Large-scale gas conversion through oxygenates: beyond GTL-FT.

In Natural Gas Conversion Vii 2004, 147, 31-36. 7.

Pellegrini, L.; Marchionna, M.; Patrini, R.; Beatrice, C.; Del Giacomo, N.; Guido, C.,

Combustion Behaviour and Emission Performance of Neat and Blended Polyoxymethylene Dimethyl Ethers in a Light-Duty Diesel Engine. 2012, 1. 8.

Wu, J.; Zhu, H.; Wu, Z.; Qin, Z.; Yan, L.; Du, B.; Fan, W.; Wang, J., High Si/Al ratio

HZSM-5 zeolite: an efficient catalyst for the synthesis of polyoxymethylene dimethyl ethers from dimethoxymethane and trioxymethylene. Green Chem. 2015, 17 (4), 2353-2357. 9.

Zhao, Q.; Wang, H.; Qin, Z.-f.; Wu, Z.-w.; Wu, J.-b.; Fan, W.-b.; Wang, J.-g., Synthesis

of polyoxymethylene dimethyl ethers from methanol and trioxymethylene with molecular sieves as catalysts. Journal of Fuel Chemistry and Technology 2011, 39 (12), 918-923. 10.

Wang, L.; Wu, W.-T.; Chen, T.; Chen, Q.; He, M.-Y., Ion-Exchange Resin–Catalyzed

Synthesis of Polyoxymethylene Dimethyl Ethers: A Practical and Environmentally Friendly Way to Diesel Additive. Chemical Engineering Communications 2014, 201 (5), 709-717. 11.

Zheng, Y.; Tang, Q.; Wang, T.; Liao, Y.; Wang, J., Synthesis of a Green Fuel Additive

Over Cation Resins. Chemical Engineering & Technology 2013, 36 (11), 1951-1956. 12.

Wang, F.; Zhu, G.; Li, Z.; Zhao, F.; Xia, C.; Chen, J., Mechanistic study for the

formation of polyoxymethylene dimethyl ethers promoted by sulfonic acid-functionalized ionic liquids. Journal of Molecular Catalysis A: Chemical 2015, 408, 228-236.


24

Page 25 of 30

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

Energy & Fuels

13.

Wu, Y.; Li, Z.; Xia, C., Silica-Gel-Supported Dual Acidic Ionic Liquids as Efficient

Catalysts for the Synthesis of Polyoxymethylene Dimethyl Ethers. Industrial & Engineering Chemistry Research 2016, 55 (7), 1859-1865. 14.

Zhang, J.; Fang, D.; Liu, D., Evaluation of Zr–Alumina in Production of

Polyoxymethylene Dimethyl Ethers from Methanol and Formaldehyde: Performance Tests and Kinetic Investigations. Industrial & Engineering Chemistry Research 2014, 53 (35), 1358913597. 15.

Fang, X.; Chen, J.; Ye, L.; Lin, H.; Yuan, Y., Efficient synthesis of poly(oxymethylene)

dimethyl ethers over PVP-stabilized heteropolyacids through self-assembly. Science China Chemistry 2014, 58 (1), 131-138. 16.

Zhu S, C. C., Xue Y, et al, Graphene Oxide: An Efficient Acid Catalyst for Alcoholysis

and Esterification Reactions. Chemcatchem 2014, 6 (11), 3080-3083. 17.

Li, H.; Song, H.; Chen, L.; Xia, C., Designed SO42−/Fe2O3-SiO2 solid acids for

polyoxymethylene dimethyl ethers synthesis: The acid sites control and reaction pathways. Applied Catalysis B: Environmental 2015, 165, 466-476. 18.

Meloni, D.; Perra, D.; Monaci, R.; Cutrufello, M. G.; Rombi, E.; Ferino, I.,

Transesterification of Jatropha curcas oil and soybean oil on Al-SBA-15 catalysts. Applied Catalysis B: Environmental 2016, 184, 163-173. 19.

Wu, S.; Huang, J.; Wu, T.; Song, K.; Wang, H.; Xing, L.; Xu, H.; Xu, L.; Guan, J.; Kan,

Q., Synthesis, Characterization, and Catalytic Performance of Mesoporous Al-SBA-15 for Tertbutylation of Phenol. Chinese Journal of Catalysis 2006, 27 (1), 9-14.


25

Energy & Fuels

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

20.

Page 26 of 30

Gao, D.; Duan, A.; Zhang, X.; Zhao, Z.; E, H.; Li, J.; Wang, H., Synthesis of NiMo

catalysts supported on mesoporous Al-SBA-15 with different morphologies and their catalytic performance of DBT HDS. Applied Catalysis B: Environmental 2015, 165, 269-284. 21.

Li, Y.; Feng, Z.; Vansanten, R.; Hensen, E.; Li, C., Surface functionalization of SBA-15-

ordered mesoporous silicas: Oxidation of benzene to phenol by nitrous oxide. Journal of Catalysis 2008, 255 (2), 190-196. 22.

Zeng, S.; Blanchard, J.; Breysse, M.; Shi, Y.; Shu, X.; Nie, H.; Li, D., Post-synthesis

alumination of SBA-15 in aqueous solution: A versatile tool for the preparation of acidic AlSBA-15 supports. Microporous and Mesoporous Materials 2005, 85 (3), 297-304. 23.

Handjani, S.; Marceau, E.; Blanchard, J.; Krafft, J.-M.; Che, M.; Mäki-Arvela, P.; Kumar,

N.; Wärnå, J.; Murzin, D. Y., Influence of the support composition and acidity on the catalytic properties of mesoporous SBA-15, Al-SBA-15, and Al2O3-supported Pt catalysts for cinnamaldehyde hydrogenation. Journal of Catalysis 2011, 282 (1), 228-236. 24.

Restrepo-Garcia, J. R.; Baldovino-Medrano, V. G.; Giraldo, S. A., Improving the

selectivity in hydrocracking of phenanthrene over mesoporous Al-SBA-15 based Fe–W catalysts by enhancing mesoporosity and acidity. Applied Catalysis A: General 2016, 510, 98-109. 25.

Al Alwan, B.; Salley, S. O.; Ng, K. Y. S., Hydrocracking of DDGS corn oil over

transition metal carbides supported on Al-SBA-15: Effect of fractional sum of metal electronegativities. Applied Catalysis A: General 2014, 485, 58-66. 26.

Li, Q.; Wu, Z.; Tu, B.; Park, S. S.; Ha, C.-S.; Zhao, D., Highly hydrothermal stability of

ordered mesoporous aluminosilicates Al-SBA-15 with high Si/Al ratio. Microporous and Mesoporous Materials 2010, 135 (1-3), 95-104.


26

Page 27 of 30

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

Energy & Fuels

27.

Xiong, H.; Zhang, Y.; Liew, K.; Li, J., Fischer–Tropsch synthesis: The role of pore size

for Co/SBA-15 catalysts. Journal of Molecular Catalysis A: Chemical 2008, 295 (1-2), 68-76. 28.

Muthu Kumaran, G.; Garg, S.; Soni, K.; Kumar, M.; Sharma, L.; Muralidhar, G.;

Ramarao, K., Effect of Al-SBA-15 support on catalytic functionalities of hydrotreating catalysts I. Effect of variation of Si/Al ratio on catalytic functionalities. Applied Catalysis A: General 2006, 305 (2), 123-129. 29.

Zhu, L.; Qu, H.; Zhang, L.; Zhou, Q., Direct synthesis, characterization and catalytic

performance of Al–Fe-SBA-15 materials in selective catalytic reduction of NO with NH3. Catalysis Communications 2016, 73, 118-122. 30.

Chen S Y, T. C. Y., Chuang W T, et al. , A Facile Route to Synthesizing

Functionalized

Mesoporous

SBA-15

Materials

with

Platelet

Morphology

and Short

Mesochannels. Chem. Mater. 2008, 20, 3906-3916. 31.

Dongyuan Zhao, J. F., Qisheng Huo,; Nicholas Melosh, G. H. F., Bradley F. Chmelka,;

Stucky, G. D., Triblock Copolymer Syntheses of Mesoporous Silica with Periodic 50 to 300 Angstrom Pores. SCIENCE 1998, 279, 548-552. 32.

Baca, M.; de la Rochefoucauld, E.; Ambroise, E.; Krafft, J.-M.; Hajjar, R.; Man, P. P.;

Carrier, X.; Blanchard, J., Characterization of mesoporous alumina prepared by surface alumination of SBA-15. Microporous and Mesoporous Materials 2008, 110 (2-3), 232-241. 33.

Michael R. Basila , T. R. K., The Nature of the Acidic Sites on Silica-Alumina. A

Revaluation of the Relative Absorption Coefficients of Chemisorbed Pyridine . The Journal of Physical Chemistry 1966,70,1681-1682. 34.

Kuhnert, C. A., M.; Breyer, S.; Hahnenstein, I.; Hasse, H.;Maurer, G., Phase Equilibrium

in Formaldehyde Containing Multicomponent Mixtures:Experimental Results for Fluid Phase


27

Energy & Fuels

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 28 of 30

Equilibria of (Formaldehyde + (Water orMethanol) + Methylal)) and (Formaldehyde + Water + Methanol + Methylal) and Comparison with Predictions. Ind. Eng. Chem. Res. 2006, 45, 51555164. 35.

D. Zhao, J. F., Q. Huo, N.et al, Nonionic Triblock and Star Diblock Copolymer and

Oligomeric Surfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures. J. Am. Chem. Soc. 1998, 120, 6024-6036. 36.

Gallo, J. M.; Bisio, C.; Gatti, G.; Marchese, L.; Pastore, H. O., Physicochemical

characterization and surface acid properties of mesoporous [Al]-SBA-15 obtained by direct synthesis. Langmuir 2010, 26 (8), 5791-800. 37.

Amir Goldbourt, M. V. L., and Shimon Vega, Characterization of Aluminum Species in

Alumina Multilayer Grafted MCM-41 Using 27Al FAM(II)-MQMAS NMR. J. Phys. Chem. B 2003, 107, 724-731. 38.

Katada, N.; Tsubaki, T.; Niwa, M., Measurements of number and strength distribution of

Brønsted and Lewis acid sites on sulfated zirconia by ammonia IRMS–TPD method. Applied Catalysis A: General 2008, 340 (1), 76-86. 39.

Tamura, M.; Shimizu, K.-i.; Satsuma, A., Comprehensive IR study on acid/base

properties of metal oxides. Applied Catalysis A: General 2012, 433-434, 135-145. 40.

Burger, J.; Ströfer, E.; Hasse, H., Production process for diesel fuel components

poly(oxymethylene) dimethyl ethers from methane-based products by hierarchical optimization with varying model depth. Chemical Engineering Research and Design 2013, 91 (12), 26482662.


28

Page 29 of 30

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

Energy & Fuels

41.

Burger, J.; Ströfer, E.; Hasse, H., Chemical Equilibrium and Reaction Kinetics of the

Heterogeneously Catalyzed Formation of Poly(oxymethylene) Dimethyl Ethers from Methylal and Trioxane. Industrial & Engineering Chemistry Research 2012, 51 (39), 12751-12761. 42.

Schmitz, N.; Homberg, F.; Berje, J.; Burger, J.; Hasse, H., Chemical Equilibrium of the

Synthesis of Poly(oxymethylene) Dimethyl Ethers from Formaldehyde and Methanol in Aqueous Solutions. Industrial & Engineering Chemistry Research 2015, 54 (25), 6409-6417. 43.

AMBERLYST 36. http://www.dow.com/assets/attachments/business/process_chemicals/

amberlyst/amberlyst_36wet/tds/amberlyst_36wet.pdf. 44.

AMBERLYST 46. http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08d9/

0901b803808d9c67.pdf?filepath=liquidseps/pdfs/noreg/177-03028.pdf&fromPage=GetDoc.


29

Energy & Fuels

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 30 of 30

Efficient Synthesis of Polyoxymethylene Dimethyl Ethers on Al-SBA-15

Recommend Documents