Research ArticleEffect of Different Catalysts on Properties of Coal Tar PitchModified by Cinnamaldehyde

Wenjuan Zhang ,1 Wenhong Tian,2 Shihua Song,1 Xianren Zeng ,1 Peng Gao,1

Lili Mao,3 and Tiehu Li4

1School of Mechanical and Materials Engineering, Jiujiang University, Jiujiang 332005, China2Library of Jiujiang University, Jiujiang University, Jiujiang 332005, China3School of Electronic Engineering, Jiujiang University, Jiujiang 332005, China4Department of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China

Correspondence should be addressed to Wenjuan Zhang; zhangwj_312@163.com

Received 19 September 2018; Accepted 3 February 2019; Published 3 March 2019

Academic Editor: Jose S. Camara

Copyright © 2019 Wenjuan Zhang et al. -is is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Cinnamaldehyde- (CMA-) modified coal tar pitches (CTPs) are prepared in the presence of acids. In this paper, the effect of boricacid and p-toluene sulfonic acid on the pyrolysis and graphitization process of CMA-modified CTP was studied. -e pyrolysisprocess was studied by Fourier transform infrared spectroscopy, thermogravimetric analysis and derivative thermogravimetry,and polarized-light microscopy. In addition, the graphitization process was studied by X-ray diffraction and Raman spectroscopy.-e results indicate the carbon yield of CMA-modified CTP with boric acid as catalyst (B7C10) is higher than that of CMA-modified CTP with p-toluene sulfonic acid as a catalyst (P7C10). In addition, under the same experimental condition (heated at400°C and held for 1 h), the mesophase spheres of B7C10 are more regular than those of P7C10 and the largest diameter of themesophase spheres can reach to 40 um. Further, after the graphitization process, the graphitization degree of B7C10 is higher thanthat of P7C10. So, it is more effective to modify CTP with boric acid as a catalyst.

1. Introduction

Coal tar pitch (CTP) is a composite material composed ofaromatic compounds with wide molecular weight distri-bution [1]. As a low cost precursor and because of the abilityto produce graphitized carbon, CTP is a promising candi-date for the production of carbon materials and carbon-carbon composite materials. [2]. However, it has low carbonyield, low density, and large coking pore volume, whichrequire a series of impregnation/carbonization steps forsubsequent densification under high pressure. -erefore, itis time-consuming and expensive to treat carbon materialsor carbon-carbon composites with CTP as a matrix pre-cursor [3]. -erefore, the key to simplify and reduce the costof the preparation process is to improve the carbon yield ofCTP by specific treatment methods. [4].

It is well known that the carbonization yield of CTP canbe improved by physical separation and chemical modification.

Physical separation can be used to separate components withdifferent average molecular weights in CTP [5]. On the otherhand, chemical modifications involve chemical reactionsbetween CTP and polystyrene, rosin, lignin/silica hybrid,and so on [6–12]. Compared with physical separation,chemical modification has advantages in saving resources,reducing waste treatment, and simplifying the preparationprocess.-erefore, it has been the typical way to improve thecarbonization yield of CTP.

Cinnamaldehyde (CMA) is a kind of alpha, beta-unsaturated aldehyde, in which the benzene ring is conju-gated with C�O and C�C groups. -erefore, it is a potentialnatural crosslinker [13]. Hydrogenation reactions can occursimultaneously in C�O and C�C groups [14]. In our pre-vious study, CMA was used to modify CTP with boric acidand p-toluene sulfonic acid as catalysts, respectively [15, 16].Higher carbonization yield and better properties of modifiedCTP can be obtained because of the cross-linking reaction

HindawiJournal of SpectroscopyVolume 2019, Article ID 6040173, 6 pageshttps://doi.org/10.1155/2019/6040173

between CMA and CTP. However, the catalysts also playimportant roles in the modification of CTP with CMA. Inthis paper, we investigate the effect of the two catalysts on thepyrolysis and graphitization process of CMA-modified CTP.

2. Experiment

2.1. Materials. CTP was purchased from the Steel Co. Ltd.(Wuhan, China). CMA, toluene, quinoline, boric acid, andPTS were of analytical grade. Some properties of the CTP areincluded in Table 1.

2.2. Modification of CTP. In our previous research, theoptimal experimental condition for CMA-modified CTP is100 g CTP and 7 g PTS mixed with 10ml of CMA [16]. Forcomparison, CMA-modified CTPs with boric acid and p-toluene sulfonic acid as catalysts were prepared under thesame experimental conditions. -e detailed preparationmethod was described in references [15, 16]. -e pitchesstudied in this paper are the parent CTP (B0C0), the CTPmodified with 10ml of CMA with 7 g of boric acid as acatalyst (B7C10), and the CTP modified with 10ml of CMAwith 7 g of PTS as a catalyst (P7C10), respectively.

2.3. Preparation of Mesocarbon Microbeads. -e mesophasespheres of the parent CTP andmodified CTPs were preparedin a high-pressure reaction kettle. About 5 g of the samplewas heated to 400°C at a heating rate of 1°C·min−1 and keptfor 1 h at this temperature. In the whole process, nitrogen gaswas introduced into the kettle.

2.4. Graphitization of CTPs. -e graphitization experimentwas carried out in a graphitizing furnace. First, the sampleswere carbonized at 900°C. -en, the carbonized sampleswere placed in a graphite crucible and heated to 2400°C at aheating rate of 10°C·min−1 for 2 h. -e resultant graphitizedproducts of B0C0, B7C10, and P7C10 were denoted asB0C0–2400, B7C10–2400, and P7C10–2400, respectively.

2.5. Characteristics of CTP and CMA-Modified CTPs. -ecompositions of CTP and CMA-modified CTPs were ana-lyzed by standard methods: softening point (SP), ring andball method, ASTM D36-66; coking value (CV), ISO 6998;toluene insolubles (TI), ISO 6376-96; quinoline insolubles(QI), ISO 6791-81.

2.6. Measurements. Elemental analysis of C, H, and N wasperformed on a Vario EL-III analyzer. Fourier transforminfrared (FT-IR) spectroscopy was acquired on a BrukerTenser-27 FT-IR spectrometer with thin films of KBr in therange of 4000–400 cm−1. -ermogravimetric analysis (TG-DTG) was performed on a Mettler-Toledo 851e thermalanalyzer under N2 atmosphere with a heating rate of10°C·min−1.

-e optical textures of the semicokes were observedusing an OLYMPUS-B061 polarized-light microscope. X-raydiffraction (XRD) was measured on a PANalytical X’Pert

PRO X-ray diffractometer with CuKα (λ�1.5406 A) radia-tion at 40 kV and 35mA. Raman spectra were performed onthe Raman microscope (inVia, Renishaw, London, England)at 900–2000 cm−1. -e spectral excitation was provided byan Ar ion laser, using the 514.5 nm line and with properpower density on the sample surface.

3. Results and Discussion

3.1. Characteristics of the ParentCTPandTwoCMA-ModifiedCTPs. -e main characteristics of the parent CTP (B0C0)and two CMA-modified CTPs (B7C10 and P7C10) are listedin Table 1. It can be observed that B7C10 and P7C10 havelower softening points, TI content, and C/H ratio than thoseof B0C0. While the CV and QI content of B7C10 and P7C10are higher than that of B0C0.-e highest CV can be obtainedfor B7C10. So, after the modification of CTP with CMA in thepresence of acid, the CV of CTP is indeed improved.

3.2. FT-IRAnalysis. FT-IR spectra of B0C0, B7C10, and P7C10are shown in Figure 1.-e attribution of the peaks of B0C0 isdescribed in references [15–17]. For the FT-IR spectra ofB7C10 and P7C10, the disappearance of the peak at 3420 cm−1indicates the reaction between CMA and O–H. In addition,the peaks at 1670 cm−1, 1120 cm−1, and 700 cm−1 are thecharacteristic peaks of CMA [18]. In the FT-IR spectrum ofB7C10, the peak attributed to the O–H stretching vibration ofboric acid is at 3200 cm−1, while the peak at 1192 cm−1 is dueto the asymmetric stretching vibration of the tetrahedral BO4[19]. In the spectrum of P7C10, the characteristic peaks ofPTS are at 1226 cm−1, 1180 cm−1, 1035 cm−1, and 567 cm−1[20]. -e appearance of the peaks indicates the presence ofthe matter.

3.3. TG-DTG Analysis. -e TG curves of B0C0, B7C10 andP7C10 are shown in Figure 2. -e results show that bothparental CTP and modified CTP decompose at a mass lossstage in the temperature range of 25–800°C. Weight loss ismainly due to the removal of light compounds and gasesproduced by thermal polymerization and aromatic ring sidechain cracking [1]. -e carbonization yield of B0C0, B7C10,and P7C10 at 800°C are 41.04%, 46.68%, and 46.12%, re-spectively, indicating that the carbonization yield of CTPincreases after CTP is modified by CMA.

-e physical and chemical changes during the CTPpyrolysis can be well understood by the combination

Table 1: Physical properties of the parent CTP and two CMA-modified CTPs.

SP CV TI QIElemental

analysis (wt.%) C/H(°C) (wt.%) (wt.%) (wt.%) N C H

B0C0 120 57.75 55.95 7.90 2.50 93.07 4.09 1.90B7C10 114 67.58 46.42 14.62 1.78 85.46 4.29 1.66P7C10 112 65.02 51.54 11.24 0.64 89.82 3.99 1.88SP, softening point; CV, coking value; TI, toluene insolubles; QI, quinolineinsolubles.

2 Journal of Spectroscopy

analysis of TG and DTG results.�eDTG curves of the parentCTP and two CMA-modi�ed CTPs are shown in Figure 3.�eDTG curve of B0C0 is characterized by a single peak centered at362°C, indicating that the mass loss rate at this temperaturereaches amaximum.However, in the DTG curves of B7C10 andP7C10, two small peaks appeared at a temperature of about370°C, which may be caused by complex changes in thistemperature. In addition, in the DTG curve of B7C10, the peakat about 150°C is caused by dehydration of boric acid [21].Otherwise, at 500°C, the peak corresponding to the thermalpolymerization at this temperature is more pronounced in theDTG curves of B7C10 and P7C10 than in B0C0.

3.4. Optical Texture of Resultant Semicokes. �e opticaltexture observed by a polarizingmicroscope is closely relatedto the conductivity, thermal expansion, mechanical strength,and graphitization properties of carbon materials and is one

of the most relevant characteristics of carbon materials [22].When CTP is heated above 350°C, mesophase spheres willappear in its optical structure, which is a good precursor ofhigh-performance carbon materials [23].

�e optical structure of the product prepared from B0C0,B7C10, and P7C10 after heating at 400°C for 1 hour is shownin Figure 4. �e optical micrograph of the parent CTP(Figure 4(a)) shows that some small mesophase spheres areproduced.�ese spheres have a maximum diameter of about5 um and are very dispersed. Figure 4(b) shows the mes-ophase spheres obtained from B7C10 after heating at 400°Cfor 1 h. Compared to B0C0 (Figure 4(a)), the number ofmesophase spheres increases and the shape is more regular.�ese spheres have a maximum diameter of 40 um. �eoptical structure of P7C10 treated under the same conditionsis shown in Figure 4(c). Compared to B0C0 (Figure 4(a)), thenumber of mesophase spheres increases, but the shapes ofthese balls are less regular and the size is about 15 um. Fromthis, it can be seen that the number of mesophase spheresincreases after the modi�cation of CTP by CMA. But theB7C10 can get larger sizes and more regular spheres.

3.5. XRDAnalysis. To study the e�ect of boric acid and PTSon the graphitization process of CMA-modi�ed coal tarpitch, B0C0–2400, B7C10–2400, and P7C10–2400, which arethe graphitized products of B0C0, B7C10, and P7C10 heated at2400°C and held for 2 h, respectively, were prepared andcharacterized by XRD and Raman spectra.

Figures 5(a)–5(c) show the XRD patterns of the threeCTPs and their corresponding graphitized products.Figure 5(d) is the magni�ed XRD patterns of B0C0–2400,B7C10–2400, and P7C10–2400. By comparing the XRDpatterns of CTP with its corresponding graphitized products(Figures 5(a)–5(c)), it can be observed that the di�ractionpeak centered at 25°, which is generally indexed to (002)di�raction of graphite [24], becomes sharp after graphiti-zation while the other di�raction peaks of graphite loomed.Otherwise, in the XRD patterns of B7C10 (Figure 5(b)), the

B0C0B7C10P7C10

0 100 200 300 400 500 600 700 800

40

50

60Wei

ght (

%)

70

80

90

100

Temperature (°C)

Figure 2: TG curves of the parent CTP and two CMA-modi�edCTPs.

B0C0

B7C10

P7C10

0 100 200 300 400 500 600 700 800 900Temperature (°C)

Diff

eren

tial w

eigh

t los

s (%

min

–1)

Figure 3: DTG curves of the parent CTP and two CMA-modi�edCTPs.

4000 3500 3000 2500 2000 1500 1000 500

5671035

11801226

32007001120

11921670

P7C10

B7C10

B0C0

1441160029153030

3420

Wavenumber (cm–1)

Tran

smitt

ance

(%)

Figure 1: FT-IR spectra of the parent CTP and two CMA-modi�edCTPs.

Journal of Spectroscopy 3

peaks centered at 14.67° and 28.1° are the di�raction peaks ofboric acid [25]. To see clearly the small peaks of thegraphitized products of B0C0–2400, B7C10–2400, andP7C10–2400, the XRD patterns are magni�ed (Figure 5(d)).It is worth noting that (201) and (114) crystal planes ofgraphite can be obverted in the XRD patterns of B7C10–2400but cannot be found in the XRD patterns of B0C0–2400 andP7C10–2400, which indicates B7C10–2400 possesses a higherdegree of graphitization than B0C0–2400 and P7C10–2400.

According to the XRD patterns, the crystal structureparameters (d002, the interlayer spacing; Lc, the crystallitesizes along the c-axis; G, the graphitization degree) ofB0C0–2400, B7C10–2400, and P7C10–2400 are calculated bythe Bragg formula and the Debye-Scherrer equation, re-spectively [26], and the results are listed in Table 2. It can beobserved that d002 and Lc values of B7C10–2400 are smallerthan those of B0C0–2400, and the graphitization degree ofB7C10–2400 is larger than that of B0C0–2400. �is indicates

50μm

(c)(b)(a)

Figure 4: Optical micrographs of the products prepared from B0C0, B7C10, and P7C10 heated at 400°C for 1 h. (a) B0C0; (b) B7C10; (c) P7C10.

B0C0–2400

B0C0

10 20 30 40 50 60 70 80 90

Intensity

2θ (°)

(a)

B7C10–2400

B7C10

Intensity

10 20 30 40 50 60 70 80 902θ (°)

(b)

P7C10–2400

P7C10

Intensity

10 20 30 40 50 60 70 80 902θ (°)

(c)

B0C0–2400

P7C10–2400

B7C10–2400 (114)

(201)

(006)

(112)(110)

(004)

(101)

(100)

(002)

Intensity

0 10 20 30 40 50 60 70 9080 1101002θ (°)

(d)

Figure 5: XRD patterns of CTPs and their graphitized products.

4 Journal of Spectroscopy

the graphitization degree of CMA-modi�ed CTP can beincreased obviously with boric acid as a catalyst. ForP7C10–2400, the value of d002 is larger than that of B0C0–2400, but the values of Lc and G are smaller than those ofB0C0–2400. �is shows that the graphitization degree ofCMA-modi�ed CTP with PTS as a catalyst cannot be in-creased although the carbon yield is increased.

3.6. Raman Analysis. �e Raman spectrum of a singlegraphite crystal usually shows a very strong peak corre-sponding to the E2G mode at 1575 cm−1 (G band). Poly-crystalline graphite and disordered carbon exhibit additionalpeaks at 1355 cm−1 (D band). �e IG/ID intensity ratio isconsidered to be an indicator of the degree of sample dis-order. �e larger the IG/ID value, the lower the degree ofdisorder [27].

Figure 6 shows the Raman spectra of B0C0–2400,B7C10–2400, and P7C10–2400. �e two peaks of P7C10–2400is little di�erent from that of B0C0–2400. But for B7C10–2400, the two peaks shift to higher frequency and the in-tensity increases strongly.

Table 3 lists the IG/ID value of Raman spectra ofB0C0–2400, B7C10–2400, and P7C10–2400. It is obvious thatB7C10–2400 has higher IG/ID value than B0C0–2400 andP7C10–2400, which indicates B7C10–2400 has a higher degreeof graphitization. So, the result of the Raman spectroscopy isconsistent with the XRD.

From the XRD and Raman spectroscopy analysis, it canbe concluded that B7C10 has a higher graphitization degreethan P7C10.�e reasonmay be due to the good compatibilitybetween boron atoms and carbon atoms.�e covalent radiusof boron atoms and carbon atoms is 0.088 nm and 0.077 nm,respectively. In addition, the di�usion coe¢cient of boronatoms in the direction of the graphite crystal is as high as6320 cm2/S−1 [28]. �erefore, it is possible that boron atomsmay occupy the disordered carbon structure by the di�usionof solid solution, and the defects of the disordered structureare eliminated [29]. So, the modi�ed CTP with boric acid asa catalyst has a higher graphitization degree than that withp-toluene sulfonic acid as a catalyst.

4. Conclusions

�e e�ect of boric acid and p-toluene sulfonic acid on thepyrolysis and graphitization process of CMA-modi�ed CTPwas compared. �e results show that larger size and moreregular mesophase spheres can be obtained from B7C10compared with P7C10 under the same experimental condition.

Furthermore, the product of B7C10 graphitized at 2400°Cpossesses a higher graphitization degree than that of P7C10.�erefore, boric acid is better than p-toluene sulfonic acid as acatalyst in the modi�cation of CTP.

Data Availability

�e data used to support the �ndings of this study areavailable from the corresponding author upon request.

Conflicts of Interest

�e authors declare that they have no con¤icts of interest.

Acknowledgments

�is research was supported by the Science & TechnologyProject of Department of Education of Jiangxi Province(GJJ170948).

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2θ002 (°) d002 (nm) β002 (°) Lc G (%)B0C0–2400 26.376 0.3376 0.5651 14.2786 74.4B7C10–2400 26.516 0.3359 0.6169 13.0834 94.2P7C10–2400 26.277 0.3389 0.8042 10.0313 59.3d002� λ/2 sin θ002; Lc� 0.89λ/(β002 · cos θ002); β is the radian of full width athalf maximum intensity (FWHM in radian); λ� 0.15406 nm;G � (0.3440− d002)/(0.3440− 0.3354).

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Table 3: Raman spectrum parameters of B0C0–2400, B7C10–2400,and P7C10–2400.

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BioMed Research International Electrochemistry

International Journal of

Hindawiwww.hindawi.com Volume 2018

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Hindawiwww.hindawi.com Volume 2018

Journal ofNanomaterials

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