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Kinetics, Catalysis, and Reaction Engineering

Catalytic Decarboxylation and Aromatization of Oleic Acid over Ni/AC without an Added Hydrogen Donor Zihao Zhang, Zhe Chen, Xin Gou, Hao Chen, Kequan Chen, Xiuyang Lu, Pingkai Ouyang, and Jie Fu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b01768 • Publication Date (Web): 04 Jun 2018 Downloaded from http://pubs.acs.org on June 8, 2018

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Catalytic Decarboxylation and Aromatization of Oleic Acid over Ni/AC without an Added Hydrogen Donor Zihao Zhanga, Zhe Chena, Xin Goua, Hao Chena, Kequan Chenb, Xiuyang Lua, Pingkai Ouyanga,b, Jie Fua* a

Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of

Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China b

State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology

and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, China * Corresponding author Jie Fu, Tel: +86 571 87951065, E-mail address: [email protected]

Abstract: Ni/AC (nickel on active carbon) catalysts with different Ni loadings were synthesized and studied for the decarboxylation and aromatization of oleic acid in the absence of H2 or hydrogen donors. Without the use of hydrogen source, the whole deoxygenation process became more economical. Moreover, oleic acid can be saturated using the H2 derived from the production of aromatics, which were also considered as the critical component in aviation biofuels. The structure and properties of the catalysts were investigated using X-ray diffraction, transmission electron microscopy, and temperature-programmed desorption of CH3COOH and CO. The experimental and characterization results revealed that 30% Ni/AC had a higher adsorption capacity of CH3COOH among the other Ni/AC catalysts, and highly dispersed and small Ni particles, providing a heptadecane yield of 40.7%. It also contained 13.8% aromatics, which fulfils the requirement of aviation fuels. This Ni/AC catalyst showed good stability even

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after being reused thrice. Keywords: Oleic acid; Decarboxylation and aromatization; Ni-based catalysts; Aviation fuels

1. Introduction The rapid development of the aviation industry has contributed to the energy crisis and greenhouse effect due to the emission of carbon compounds.1 The development of alternative fuel candidates has become increasingly important in the aviation industry and hence has attracted intensive attention in recent years.2-4 Aviation fuels, which are a mixture of aromatics, paraffins, and naphthenes, are only one of the many products derived from crude oil.5,6 The aromatics content in aviation fuels should be less than 25 vol %, due to the better burning properties of paraffins, and higher than 8 vol %, for fear of leakage and pressure discharge from the system.7 Therefore, the production of a mixture of paraffins and aromatics with a certain percentage of aromatics from renewable biomass is becoming increasingly important and useful. Triglycerides, which are the main components of waste cooking oils, microalgae lipids, vegetable oils, and animal fats, have been widely used for the production of paraffins and aromatics.8, 9 The hydrodeoxygenation process or decarboxylation with hydrogen inevitably consumes a considerable amount of molecular H2, limiting its large-scale applications. 10, 13-19 Therefore, in recent years, attention is being paid to the decarboxylation of oils and lipids to produce aviation fuel, without hydrogen or hydrogen donors; the decarboxylation of saturated fatty acids and corresponding derivatives has especially made good progress.2,

20-23

However, the

decarboxylation of the unsaturated fatty acids present in the triglycerides or their hydrolysis products, has proven challenging.21, 24, 25 For instance, while a selectivity of 90% to heptadecane

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could be achieved from stearic acid over Pt/C, oleic acid showed low yields of 9.2 and 1.3% for heptadecane and aromatics, respectively, under the same reaction conditions.26 Consequently, numerous efforts have been made to improve the decarboxylation and/or aromatization of unsaturated fatty acids without using H2 or a hydrogen donor. Murizin et al. reported that saturated hydrocarbons could be produced by the deoxygenation of unsaturated fatty acids over Pd/C; however, the concentration of n-heptadecane was very low.27 Savage and co-workers developed a bimetallic PtSnx/C catalyst for the decarboxylation of unsaturated fatty acids in hydrothermal media, with different Sn-containing alloys; they obtained two to three times higher heptadecane yields than those obtained with Pt/C at the same conditions.4 In our previous work, yields of 71% heptadecane and 19% aromatics were obtained simultaneously from the decarboxylation and aromatization of oleic acid over Pt/C under nonsolvent reaction conditions.6 However, the selectivities to heptadecane over non-noble CoMo and Ni/MgO-Al2O3 catalysts were only 6 and 13%, respectively.28, 29 Although the noble metal Ptbased catalyst exhibited good catalytic activity for decarboxylation and/or aromatization of unsaturated fatty acids without using H2 or a hydrogen donor, the catalytic performance of nonnoble catalysts still needs to be improved. In this study, Ni/AC catalysts with different Ni loadings (10, 20, 30, and 40%) were synthesized using the wetness-impregnation method, and the decarboxylation and aromatization of oleic acid were investigated in the absence of a hydrogen donor. The structure and properties of these catalysts were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature-programmed desorption (TPD) of CH3COOH and CO. The influence of catalyst loading, Ni loading, reaction temperature, reaction time, and the reusability of the catalysts were investigated. The product distribution was recorded, as molar-carbon yield

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including by-products, to identify the carbon balance after the reaction.

2. Experimental 2.1 Materials Ni(NO3)2·6H2O (> 98.0% purity) was obtained from Sinopharm Chemical Reagent Co., Ltd. Active carbon (AC), oleic acid (> 99% purity), and stearic acid (> 99% purity) were obtained from Sigma-Aldrich, USA. 1-heptadecene (> 99.5% purity) and undecylbenzene (> 98% purity) were obtained from Tokyo Chemical Industry Co., Ltd. Deionized water was prepared in our laboratory. Heptadecane was obtained from Aladdin Industrial Corporation, Shanghai, China. Acetone (analytic reagent grade) was purchased from Hangzhou Chemical Reagent Co., Ltd, China. All chemicals were used without further purification. 2.2 Catalyst preparation All catalysts were synthesized using the incipient-wetness impregnation method. First, the AC carrier was added to a certain concentration of a Ni(NO3)2·6H2O solution. Second, these samples were ultrasonically treated for 0.5 h, and then aged overnight at room temperature. Finally, the resulting samples were dried at 110 °C for 12 h, followed by calcination at 500 °C for 2 h, under N2. Before the reaction, all catalysts were activated with H2 at 400 °C for 2 h. The theoretical Ni loading ranged from 10 to 40%. 2.3 Catalyst characterization XRD patterns of the samples were obtained on a Bruker D8 Advance X-ray diffractometer with a Cu Kα source. The TEM images of the samples were captured using a JEOL JEM-2100 instrument. X-ray photoelectron spectra (XPS) were taken on a VG ESCALAB MARK II (ESCALAB), and the data was calibrated by the standard peak of C1s (284.8 eV). The N2

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adsorption-desorption isotherms (BET) were collected using a Micromeritics 3Flex adsorption instrument. Prior to the measurements, each sample was degassed under N2 at 300 °C for 12 h. Brunauer-Emmett-Teller (BET) equation was used for the calculation of the specific surface areas. The total amount of N2 adsorbed at p/p0=0.99 was used to calculate the total pore volume. The CO-TPD determination was carried out on FineSorb-3010 (Zhejiang Finetec Instruments Co. Ltd.) with a thermal conductivity detector. Prior to analysis, all the samples were treated with H2 at 400 °C for 2 h. Typically, 50 mg of reduced catalyst was pretreated for 2 h at 120 °C in He, following which the temperature was decreased to 40 °C. Thereafter, the adsorbed gas, 5% CO in 95% N2, was injected into the furnace at a flow rate of 20 mL min-1. The TPD profile was collected as the temperature increased to 700 °C. For the CH3COOH-TPD measurement, a certain amount of acetic acid was added to soak the samples. The samples were then pre-treated from 30 °C, in He for 1 h. Finally, the TPD profile was collected while increasing the samples’ temperature to 650 °C at a heating rate of 10 °C min-1. The thermogravimetric characteristics of the catalysts were evaluated by thermogravimetric analysis (TGA) using TA-Q500 instrument. The samples were heated to 600 °C at 10 °C min-1 under a flow of air of 50 cm3 min-1). The metal element contents of all catalysts were obtained by inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent 730 device). Prior to the analysis, the catalysts were dissolved in a mixture of HCl and HNO3. ICP results are shown in Table S1; the actual Ni loadings of 10, 20, 30, and 40% Ni/AC were 11.3, 22.1, 31.5, and 43.2%, respectively, which are very close to the theoretical values. Therefore, we used the theoretical values to represent the actual Ni loading of Ni/AC catalysts. The leaching of Ni after reaction was also analyzed by ICP analysis. Typically, 50 mg of oleic acid was reacted with 30 mg of 30% Ni/AC at 350 °C for 4 h and washed using deionized water to 50 mL for the next ICP

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measurement. 2.4 Experimental procedure and analytical method All reactions were carried out in a 1.67 mL micro-batch reactor (Swagelok, USA). In each experiment, 50 mg of oleic acid and 30 mg of catalyst with no hydrogen or solvents were loaded into the reactor. Subsequently, the sealed reactor was heated in a fluidized-sand bath (Techne SBL-2) at the desired temperature. At the end, the reaction was quenched using cold water. The quantification and identification of the products were performed with an Agilent 7890B gas chromatography/5977A mass spectrometry instrument (GC/MS) equipped with a flame ionization detector (FID) and HP-5 capillary column. Quantitative analysis of the samples was carried out using calibration curves for every compound. Identification analysis was performed by matching the gas chromatograph retention times against known standards. The results were the average of values obtained from three independent measurements. The molar conversion was calculated by dividing the moles of stearic acid consumed by the moles of stearic acid added into the reactor. Selectivity was calculated by dividing the moles of the product obtained by the moles of stearic acid consumed. The product yield was calculated by multiplying the conversion efficiency and selectivity. 3. Results and discussion 3.1 Characterization of the catalysts The crystal phases of Ni and carrier AC in 10, 20, 30, and 40% Ni/AC were investigated by XRD analysis. As shown in Fig. 1, the prominent peak at the 2θ value of 24° was attributed to the reflection of the amorphous carbon support.30 The (111), (200), and (220) diffraction peaks of Ni metal (JCPDS 04-0850) at 2θ values of 44.5°, 51.8°, and 76.4° were observed in all the catalysts and assigned to metallic Ni with a face-centered-cubic lattice.31 With the increase in the

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loading of Ni in Ni/AC, the intensity of the diffraction peaks assigned to Ni gradually increased at the cost of the peak signals of the AC carrier. XRD results suggested that the crystallite size of Ni calculated by Scherrer equation and the AC coverage changed as the Ni loading increased. To further confirm this change, TEM images and particle size distributions of 10, 20, 30, and 40% Ni/AC are presented in Fig. 2. For all catalysts, most of the nanoparticles were found to be spherical and highly dispersed on the AC carrier. The average particle size of Ni was about 8.7 nm in 10% Ni/AC, which is slightly lesser than that the 9.6 nm for 20% Ni/AC and 9.4 nm for 30% Ni/AC. Additionally, 40% Ni/AC had the highest average particle size (12.5 nm), much higher than the other three catalysts. These particle-size distributions are very consistent with the XRD results. N2 adsorption-desorption isotherms (BET) of 30% Ni/AC was show in Fig. S1. This catalyst exhibited a plateau starting at a very low relative pressure and a type IV isotherm with a remarkable hysteresis loop, which indicated that the existence of hierarchical porous structure. Therefore, Ni/AC catalysts exhibited a rich mesoporous and microporous structure for the highly dispersion of Ni particles. Additionally, 30% Ni/AC possess high specific surface area of 606 m2/g with the large pore volume of 0.25 cm3/g calculated by BJH desorption branch. XPS results in Fig. S2 exhibited that Ni oxidation state as the main Ni species and a small amount of Ni0 was discovered on the surface of Ni/AC. Fig. 3 shows the CO-TPD profiles for the 10, 20, 30, and 40% Ni/AC catalysts after H2 pre-treatment. The curves between 100 and 300 °C correspond to the physically adsorbed CO on Ni/AC. The peaks located between 400 and 600 °C can be attributed to the desorption of chemisorbed CO on metallic Ni.32 Among these catalysts, 40% Ni/AC showed the highest desorption temperature, indicating the strongest CO adsorption ability. However, the lowest CO desorption amount was also found on this catalyst, according to the

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desorption peak areas. These results are due to the agglomeration of particles and their low dispersion, which can be confirmed by the XRD and TEM results. The low CO desorption amount of 10% Ni/AC is ascribed to its low Ni loading. The decarboxylation of fatty acids was due to the removal of CO2 from the carboxyl group (-COOH). Therefore, the study of the adsorption ability of -COOH on the different catalysts appears to be particularly important. Fig. S3 presents the CH3COOH-TPD results for different catalysts. The spectra of all the catalysts show two main peaks around 150 and 330 °C. The lower-temperature peak should be attributed to the acetic acid still physically adsorbed on the catalysts. The second peak, at higher temperature, was ascribed to the desorption of chemisorbed CH3COOH or its decomposition products from the catalysts.31 As shown in Fig. S3, the desorption amount of 40% Ni/AC at high temperature was much less than that of 20 and 30% Ni/AC, which was further proof of the agglomeration of Ni particles and their low dispersion in 40% Ni/AC. 3.2. Decarboxylation and aromatization of oleic acid 3.2.1. Effect of nickel loading The control experiment, the conversion of oleic acid without a catalyst, was carried out. The results showed that only oleic acid was detected and no products were produced. Fig. S4 shows the GC/FID chromatogram of the products obtained over 30% Ni/AC at 350 °C. The results showed that heptadecane and undecylbenzene were obtained as the major products, and a little cracking paraffin was also obtained. The reaction route including hydrogen transfer, decarboxylation, aromatization, and cracking, was very similar to that in our previous work.6 Subsequently, the deoxygenation of oleic acid over the four Ni/AC catalysts, with 10, 20, 30, and 40% Ni loading, was carried out at 350 °C for 4 h. The results are shown in Fig. 4. The

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deoxygenation of oleic acid went up remarkably from 76.7 to 100% with the increase of Ni loading from 10 to 20%, and subsequently, it remained stable. At the same time, the total yield of heptadecane and aromatics first increased from 8.4% over 10% Ni/AC to 44.8% over 30% Ni/AC, and then decreased to 39.8% over 40% Ni/AC. The 30% Ni/AC catalyst showed the best catalytic performance for the production of heptadecane and aromatics. The characterization results showed that it had a relatively high Ni dispersion, small particle size and the mixed Ni species of Ni and NiO on the surface of catalyst, which should be responsible for its good decarboxylation and aromatization activity. It is worth noting that stearic acid, an intermediate product, was not completely converted over all catalysts. 3.2.2. Effects of catalyst loading, reaction temperature, and time Fig. 5 shows the deoxygenation of oleic acid and the yield of products over four different temperatures, 330, 350, 370, and 390 °C, for 4 h with 0.176 mmol of oleic acid and 30 mg of 30% Ni/AC. It was found that the conversion of oleic acid was 100% at all temperatures. The total yield of heptadecane and aromatics went up from 21.8 to 48.9% with the increase of temperature from 330 to 370 °C, and then decreased to 31.4% at 390 °C. The yield of stearic acid decreased continuously as the reaction temperature increased. Although the total yield of heptadecane and aromatics at 370 °C was higher than that at 350 °C, more cracking products were also formed at 370 °C. Therefore, the influence of reaction time on the decarboxylation and aromatization of oleic acid was investigated at 350 °C, with the results shown in Fig. 6. The total yield of heptadecane and aromatics increased slightly from 44.8 to 46.2% with reaction time prolonged from 4 to 5 h. For further enhancing the intermediate conversion, the effects of catalyst loading, reaction temperature, and time were examined over 30% Ni/AC. The test results of catalyst loading at 350 °C for 4 h are shown in Fig. S5. The total yields of heptadecane and aromatics

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increased continuously from 44.8 to 54.5% when the catalyst loading increased from 30 to 70 mg. Meanwhile, the yield of the stearic acid intermediate went down with the increase of the heptadecane and aromatics yields. 3.2.3. Product distribution We analyzed the product distribution from the conversion of 0.176 mmol of oleic acid over 70 mg of 30% Ni/AC catalyst, at 350 °C for 4 h. The product distribution (molar carbon yield) was calculated as the molar ratio of the carbon in a specific product to the carbon in stearic acid added to the reactor. Fig. S6 shows the TGA results from the spent 30% Ni/AC recycled after the first reaction. The approximately 14% weight loss before 400 °C should be ascribed to carbon deposition from the reactant or products. Another peak at higher temperature was due to the oxidation of carrier AC. The 14% weight loss obtained from the TGA results corresponds to approximately 29.9% of molar carbon yield. Table 1 summarizes the molar carbon yields of all products; the total molar carbon yield was up to 92.2%. Heptadecane, aromatics, and coke were the main products with a molar carbon yield of 38.4, 13.0, and 29.9%, respectively. The total molar carbon yield of heptadecane and aromatics was 51.4%, slightly less than their mole yield of 54.2%. Coke was the major by-product because of the high-temperature reaction conditions. 3.2.4. Catalytic activity maintenance The stability of the catalyst is of great importance for commercial processes. Therefore, recycling studies of the 30% Ni/AC catalyst were carried out at 350 °C for 4 h with 0.176 mmol oleic acid and 70 mg catalyst. The spent catalysts were recovered by filtration and washed thoroughly with acetone, and then dried in a vacuum drying oven at 110 °C for 12 h followed by reducing with H2 at 400 °C for 4 h. As shown in Fig. 7, the conversion of oleic acid and the total yield of heptadecane and aromatics over fresh Ni/AC (1st use), Ni/AC used once previously (2nd

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use), and Ni/AC used twice previously (3rd use) were almost the same. The total yield of heptadecane and aromatics of 30% Ni/AC remained around 51.2% even at the 3rd use, and the yield of stearic acid remained at only 5%. The ICP-OES results showed that about leaching of 0.02 mg Ni was observed after reaction, which is much slower than the Ni content added in the reactor (9.45 mg). Therefore, there are almost no Ni leaching after reaction, contributing a good reuse performance of Ni/AC. Conclusions Ni/AC catalysts with different Ni loadings were synthesized and used for the decarboxylation and aromatization of oleic acid without an added hydrogen donor. Without the use of hydrogen source, the whole deoxygenation process became more economical. Moreover, oleic acid can be saturated using the H2 derived from the production of aromatics. The 30% Ni/C catalyst exhibited good activity and maintenance for the decarboxylation and aromatization of oleic acid. XRD, TEM, CH3COOH-TPD, and CO-TPD results revealed that among the other Ni/AC catalysts, 30% Ni/AC had a higher adsorption capacity of CH3COOH, with highly dispersed small Ni particles, resulting in a heptadecane yield of 40.7% with 13.8% aromatics, complied with the critical specification of aviation fuels. TGA results indicated that carbon deposition was the major reaction by-product. The Ni/AC catalyst also showed good stability after being reused thrice.

Acknowledgments This work was supported by the Zhejiang Provincial Natural Science Foundation of China (No. LR17B060002), the National Natural Science Foundation of China (Nos. 21436007, 21676243, 21706228), and the Fundamental Research Funds for the Central

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Universities (No. 2018QNA4038).

Supporting Information. Details about the characterization results (ICP, N2 adsorptiondesorption, XPS, CH3COOH-TPD, TGA), typical GC/FID chromatogram and the effect of catalyst loading.

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deoxygenation of C18 free fatty acids. Appl. Catal. A-Gen. 2010, 375, (1), 134-139. 26. Fu, J.; Lu, X.; Savage, P. E., Hydrothermal decarboxylation and hydrogenation of fatty acids over Pt/C. ChemSusChem 2011, 4, (4), 481-6. 27. Snåre, M.; Kubičková, I.; Mäki-Arvela, P.; Chichova, D.; Eränen, K.; Murzin, D. Y., Catalytic deoxygenation of unsaturated renewable feedstocks for production of diesel fuel hydrocarbons. Fuel 2008, 87, (6), 933-945. 28. Shim, J.-O.; Jeong, D.-W.; Jang, W.-J.; Jeon, K.-W.; Kim, S.-H.; Jeon, B.-H.; Roh, H.-S.; Na, J.-G.; Oh, Y.-K.; Han, S. S.; Ko, C. H., Optimization of unsupported CoMo catalysts for decarboxylation of oleic acid. Catal. Commun. 2015, 67, 16-20. 29. Roh, H.-S.; Eum, I.-H.; Jeong, D.-W.; Yi, B. E.; Na, J.-G.; Ko, C. H., The effect of calcination temperature on the performance of Ni/MgO-Al2O3 catalysts for decarboxylation of oleic acid. Catal. Today 2011, 164, (1), 457-460. 30. Yu, W.; Zhao, J.; Ma, H.; Miao, H.; Song, Q.; Xu, J., Aqueous hydrogenolysis of glycerol over Ni-Ce/AC catalyst: Promoting effect of Ce on catalytic performance. Appl. Catal. A-Gen. 2010, 383, (1-2), 73-78. 31. Zhang, Z.; Yang, Q.; Chen, H.; Chen, K.; Lu, X.; Ouyang, P.; Fu, J.; Chen, J. G., In situ hydrogenation and decarboxylation of oleic acid into heptadecane over a Cu-Ni alloy catalyst using methanol as a hydrogen carrier. Green Chem. 2018, 20, (1), 197-205. 32. Kim, D.; Kwak, B. S.; Min, B.-K.; Kang, M., Characterization of Ni and W co-loaded SBA15 catalyst and its hydrogen production catalytic ability on ethanol steam reforming reaction. Appl. Surf. Sci. 2015, 332, 736-746.

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Industrial & Engineering Chemistry Research 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 1. Product distribution from the conversion of oleic acid over 30% Ni/AC catalyst at 350 °C for 4 h Compound

Yield (%)

Heptane

0.1

Octane

0.1

Nonane

0.2

Decane

0.3

Undecane

0.4

Dodecane

0.5

Tridecane

0.6

Tetradecane

1.7

Pentadecane

1.1

Hexadecane

1.2

Heptadecane

38.4

Aromatic

13.0

Stearic acid

4.7

Coke

29.9

Total

92.2

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♦

40% Ni/AC 30% Ni/AC 20% Ni/AC 10% Ni/AC

♦ Ni

♦ ♦

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

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10

20

30

40

50

60

70

80

2θ Fig. 1. Wide-angle XRD patterns of 10, 20, 30, and 40% Ni/AC catalysts

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Fig. 2. TEM images and particle size distributions of (a) 40% Ni/AC; (b) 30% Ni/AC; (c) 20% Ni/AC; (d) 10% Ni/AC catalysts

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o

Temperature ( C)

10% Ni/AC 20% Ni/AC 30% Ni/AC 40% Ni/AC

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

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100

200

300

400

500

600

700

o

Temperature ( C) Fig. 3. CO-TPD profiles of 10, 20, 30, and 40% Ni/AC catalysts

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60

100

50 40

Heptadecane and Aromatic Stearic acid

60

30 40

20 10

20

0

0 10% Ni/AC

20% Ni/AC

30% Ni/AC

Conversion (%)

80

Yield (%)

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

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40% Ni/AC

Fig. 4. Conversion of oleic acid and yield of different products over Ni/AC catalysts with different Ni loadings. Reaction conditions: T = 350 °C; t = 4 h; catalyst loading = 30 mg; oleic acid loading = 0.176 mmol

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60

100

40 60 Heptadecane and aromatics Stearic acid Cracking paraffins

20

40

Conversion (%)

80

Yield (%)

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

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20 0

0 330

350

370

390

o

Temperature ( C) Fig. 5. Conversion of oleic acid and yield of different products with different temperatures. Reaction conditions: T = 330–390 °C; t = 4 h; catalyst loading = 30 mg; oleic acid loading = 0.176 mmol

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100

Conversion or yield (%)

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

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80 Oleic acid Heptadecane and aromatics Stearic acid

60 40 20 0 1

2

3

4

5

Time (h) Fig. 6. Conversion of oleic acid and yield of different products with different times. Reaction conditions: T = 350 °C; t = 1~5 h; catalyst loading = 30 mg; oleic acid loading = 0.176 mmol

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100 60

Heptadecane and aromatics Stearic acid

40

60

40

Conversion (%)

80

Yield (%)

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

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20 20

0

0 1st

2nd

3rd

Fig. 7. Conversion of oleic acid and yield of different products with different times. Reaction conditions: T = 350 °C; t = 4 h; catalyst loading = 70 mg; oleic acid loading = 0.176 mmol

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Catalytic Decarboxylation and Aromatization of Oleic Acid over Ni/AC without an Added Hydrogen Donor Zihao Zhanga, Zhe Chena, Hao Chena, Kequan Chenb, Xiuyang Lua, Pingkai Ouyanga,b, Jie Fua*

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