Mutual Influences between Organic Matter and Minerals during Oil

Feb 4, 2019 - To better understand the mutual influence between organic matter and minerals during oil shale pyrolysis, Huadian oil shale was treated ...
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Mutual influences between organic matter and minerals during oil shale pyrolysis Zhenghua Lu, Xiaosheng Zhao, Zhenyu Liu, and Qingya Liu Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b03703 • Publication Date (Web): 04 Feb 2019 Downloaded from http://pubs.acs.org on February 7, 2019

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Energy & Fuels

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Mutual influences between organic matter and minerals during oil

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shale pyrolysis

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Zhenghua Lu, Xiaosheng Zhao, Zhenyu Liu and Qingya Liu

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State Key Laboratory of Chemical Resource Engineering, Beijing University of

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Chemical Technology, Beijing 100029

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Abstract: To better understand the mutual influence between organic matter and

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minerals during oil shale pyrolysis, Huadian oil shale was treated by HCl-HF acids

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and 8 dominant minerals were added separately into the resulting oil shale for

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pyrolysis. The pyrolysis experiment was performed on a thermogravimetric analyzer

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coupled with a mass spectroscopy (TG-MS) and the influence was discussed from the

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viewpoints of mass loss of organic matter and release of light volatile products (CH4,

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C2H6, C3H8, C4H10, C6H6, C7H8, C6H6O, H2, H2O, CO and CO2). Results indicate that

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the organic matter or pyrolysis products delay(s) the release of water in clays. All the

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minerals have little effect on the decomposition of organic matter and CaCO3,

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kaolinite and TiO2 also have little effect on the volatiles reaction; while K2CO3,

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Na2CO3, MnCO3, montmorillonite and Fe2O3 influence the volatiles reaction in

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different ways which were discussed in detail in this work.

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Key words: Oil shale; minerals; organic matter; mutual influence; TG-MS

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1. Introduction

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Oil shale is an important unconventional hydrocarbon resource with composition of

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approximately 15–50 wt % organic matter and 50–85 wt % inorganic mineral.1 The



Corresponding author. E-mail: [email protected] 1

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mineral consists mainly of carbonates, clays, metal oxides, quartz and pyrite.2

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Pyrolysis or retorting is a major technology to convert oil shale’s organic matter to

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shale oil and fuel gas. In this process, minerals were reported to have significant

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influences on the pyrolysis of organic matter.3-11

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The influences were studied mostly by demineralization and then evaluating the

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changes in mass loss, products yield or kinetics during pyrolysis. Espitalie et al.3

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found that the kerogen of Cameroon oil shale yielded more liquid hydrocarbons than

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the raw oil shale during pyrolysis in a fixed bed reactor, suggesting inhibiting effect

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of minerals. Yan et al.4 studied the overall effect of inherent minerals on Huadian oil

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shale pyrolysis using TG-FTIR and reported that the mass loss and the amount of gas

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product were reduced by demineralization. Aboulkas et al.5 found that the temperature

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of maximum devolatilization rate of kerogen was 10 °C lower than that of the raw oil

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shale (Morocca), concluding that the inherent minerals inhibited the decomposition of

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kerogen. The effects of different minerals were investigated mainly by stepwise

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demineralization. Karabakan et al.6 reported that alkali and alkaline earth carbonates

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promoted the pyrolysis of organic matters from Göynük and Green River oil shale by

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analyzing the change in pyrolysis activation energy before and after HCl treatment.

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Ballice et al.7 drawn the same conclusion as that of Karabakan et al. based on the

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phenomenon that the yield of volatile hydrocarbons was decreased by HCl treatment.

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However, Al-Harahsheh et al.8 found that the total oil and gas yield increased when

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Jordan oil shale was subjected to HCl treatment, which is clearly different from the

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observations of Ballice and Karabakan. Ballice et al.7 also reported that inherent 2

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silicates (clay minerals) had inhibiting effect on the pyrolysis of organic matter from

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Turkey oil shale at 450-650 °C based on an increased yield of volatile hydrocarbons

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after HF treatment. Chang et al.9 found that inherent clay minerals of Huadian oil

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shale inhibited the formation of shale oil but promoted the formation of gas and water

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by demineralization. We recently studied the influence of inherent minerals on

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pyrolysis of Yilan oil shale using a TG-MS and deduced that calcite and iron oxide

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promoted the decomposition of organic matter to form volatile and montmorillonite

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promoted the reaction of volatiles to form coke and gas.10

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In fact, treatment of oil shale with one acid usually removes a variety of minerals.

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For example, HCl treatment could remove carbonates as well as some metal oxides.

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Therefore, the results obtained by demineralization are generally the comprehensive

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effects of several minerals and it is difficult to distinguish the influence of each

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mineral. Although some conclusions have been drawn by demineralization method,

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they are more or less deductive. Since the organic matter is physically surrounded by

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minerals,1,12 addition of mineral to the organic matter were taken by some researchers

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to investigate the influence of individual mineral. Lai et al.13 introduced metal oxides

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into the organic matter of Yilan oil shale to study the effect of shale ash on pyrolysis.

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They reported that CaO and Na2O inhibited coke formation while Fe2O3 promoted the

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cracking of shale oil to form coke and gas. Hu et al.11 introduced calcite,

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montmorillonite, gypsum and kaolinite into kerogen at a mineral to kerogen ratio of 9

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in mass and studied their effects using an aluminum retort. They found that calcite

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decreased the oil yield by 9.3 wt % and increased the gas yield by 4.2 wt%, 3

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montmorillonite and gypsum increased the oil and gas yields, and kaolinite had little

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effect.

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Moreover, it was reported that coal char may promote decomposition of some

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carbonates14,15 and the initial decomposition temperature of Na2CO3 reduced from

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855 °C for pure Na2CO3 to 602 °C in the presence of char.15 If this observation

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applies to the oil shale pyrolysis, the decomposition of carbonates will contribute to

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the mass loss, which may be mistaken as the promoting effect of carbonates on

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organic matter pyrolysis. To our knowledge, the mutual influence between organic

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matter and minerals is rarely investigated during oil shale pyrolysis.

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Based on the above analysis, eight minerals were mixed individually with HCl-HF

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-treated Huadian oil shale and the mixtures were subjected to pyrolysis on a

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thermogravimetric analyzer coupled with a mass spectrometer (TG-MS) to understand

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mutual influence between organic matter and each mineral. The minerals and organic

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matter were also pyrolyzed separately and the results were taken as backgrounds to

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deduct interference of mineral decomposition on evaluation of the influence.

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2. Experimental section

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2.1. Materials

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The oil shale used in this work was from Dachengzi Mine located in Huadian of

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Jilin province in China and termed as HDOS. They were ground and sieved to 60-100

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mesh, and then demineralized by acid treatments. The acids used include HCl (18.5

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wt %) and a mixture of HCl (18.5 wt %) and HF (40 wt %). The oil shale and HCl

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solution were mixed at a ratio of 10 g to 100 mL in a flask, stirred for 5 h at 65 °C 4

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under a nitrogen atmosphere. The solid was then separated and rinsed with deionized

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water at 50-60 °C until the filtrate was neutral. The HCl-treated oil shale was termed

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as HDOS-C. HDOS-C was treated by a mixture of 50 ml HF and 50 ml HCl and the

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resulting sample was termed as HDOS-CF. The HNO3 treatment which is widely used

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to remove pyrite was not performed because this treatment may cause oxidation of

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organic matter.16

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Eight compounds with purities of higher than 98%: CaCO3, K2CO3, Na2CO3,

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MnCO3, kaolinite, montmorillonite, Fe2O3 and TiO2 were selected based on the

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analysis results of minerals in Huadian oil shale. They were ground and screened

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through a 100 mesh sieve and mixed with HDOS-CF at the ratio of 1:1 in mass to

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study their mutual influence during pyrolysis.

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2.2 Pyrolysis experiment

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Pyrolysis experiment was performed on a TG (Setsys Evolution 24, Setaram)

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coupled with a MS (Omnistar 200, Balzers). The mixture of HDOS-CF and mineral

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with total mass around 15 mg was loaded into the quartz crucible in TG, heated to

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110 °C in an Ar flow with a rate of 100 mL/min and maintained for 20 min to remove

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moisture. The mixture was then heated to 600 °C at a rate of 20 °C /min and

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maintained for 20 min. Each experiment was repeated at least twice to ensure

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repeatability and accuracy of the experimental data. Results indicate that the relative

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standard deviation of mass loss is less than 0.5%.

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The outlet of TG was connected with the MS through a hot stainless steel capillary

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at about 180 °C to monitor the gaseous products on-line. To eliminate the effect of 5

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baseline change in MS signal, the ion intensity of each product was divided by that of

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Ar (m/z = 40) at the same time-on-stream and the corrected intensity was normalized

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based on the total mass.

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2.3 Characterization

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Ultimate analysis was performed on an Elemental Analyzer (Vario EL, Germany).

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Proximate analysis was performed on the TG and the detailed procedure can be found

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in our previous work.10

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X-ray diffraction (XRD) was carried out on a D8FOCUS X-ray diffractometer

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(Brook) equipped with Cu Kα1 (λ = 0.15406 nm) radiation operated at 40 kV and 200

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mA. The samples were scanned over a 2θ range of 5-80° at a frequency of 2° min-1.

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X-ray fluorescence (XRF) was carried out on a S4-Explorer X-ray fluorescence

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spectrometer (Bruker) under the sequential scanning mode. The maximum voltage is

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60 KV and the maximum current is 170 mA.

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The filtrate obtained during the acid treatment of oil shale was characterized by

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inductively coupled plasma optical emission spectroscopy (ICP-OES, Perkin-Elmer

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Optima) to identify the main metal elements.

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3. Results and discussion

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3.1 Characterization of minerals

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Results of proximate and ultimate analyses of HDOS and HDOS-CF are

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summarized in Table 1. The ash content is as high as 70.27% for HDOS and reduced

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to 15.65% after demineralization process. Figure 1 shows the XRD spectra of HDOS

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and the acid treated samples. It can be seen that the minerals in HDOS include quartz 6

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(SiO2), montmorillonite {(Na,Ca)0.33(Al,Mg)2[Si4O10](OH)2·nH2O}, calcite (CaCO3),

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kaolinite [Al2Si2O5(OH)4], hematite (Fe2O3) and pyrite (FeS2). The HCl treatment

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removed calcite and hematite and had little influence on other minerals (see

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HDOS-C). The subsequent HCl+HF treatment eliminated quartz, montmorillonite and

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kaolinite as reported in literatures9,10 while the diffraction peaks of pyrite become

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sharper. Meanwhile, a broad peak appears between 15-25o which is assigned to

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amorphous carbon in organic matters, and several small peaks appear at 15o, 39o, 44o

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and 51o which are assigned to a fluoride compound (NaMgAlF6H2O).

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The contents of various minerals in the oil shale samples were determined by XRF.

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It is noted that XRF actually measures the amount of element in the sample and the

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data are usually presented in the form of oxides. The results shown in Table 2 indicate

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that the minerals in HDOS are dominated by Si and Al elements with minor Fe, Ca,

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K, Ti, Mg Na and Mn. According to the XRD results, the first two minerals in amount

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should be quartz and kaolinite. The contents of Fe, Ca, K, Na, Mn are obviously

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decreased after the HCl treatment. This observation is consistent with the ICP analysis

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to the HCl-washing filtrate which indicates the presence of metal elements in the

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order of Ca > Fe > K > Na > Mn. The Ca is mainly from calcite and the Fe is from

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hematite in oil shale as evidenced by the XRD results. The elements K, Na and Mn

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should be from their carbonates since HCl mainly dissolves these substances.17,18 It is

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notable that these substances are too little to be detected by XRD. The contents of Si

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and Al are significantly decreased and those of Ca Ti, Mg and Na are further

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decreased after the subsequent HCl+HF treatment. The phenomena except Ti are 7

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consistent with the XRD results. The Ti compound in minerals cannot be dissolved by

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HCl but by the HCl+HF mixture, suggesting that it is probably TiO2 as reported in

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literatures.10,18 Based on the above discussion, eight minerals (CaCO3, K2CO3,

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Na2CO3, MnCO3, kaolinite, montmorillonite, Fe2O3 and TiO2) are selected as model

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substances for the pyrolysis study. For clarity, the minerals are classified into three

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types: carbonates, clay minerals and metal oxides.

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3.2 Pyrolysis of organic matter in the presence of carbonates

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Effects of minerals on the organic matter pyrolysis are discussed from the

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viewpoints of mass loss (i.e. decomposition of organic matter) and light volatile

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products (i.e. volatile reaction). Since some minerals may cause mass loss due to

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self-decomposition, all the model substances were heated individually under the same

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conditions as those of pyrolysis, along with the individual pyrolysis of organic matter

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for comparison. Based on the individual results, the theoretical mass loss and release

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of light volatile products during co-pyrolysis of organic matter with each mineral

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were calculated via Eq. (1).

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Eq. (1)

𝑌T = 𝑌M × 𝑤M + 𝑌O × 𝑤O

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YT is the theoretical value, YM is the experimental data of one mineral during

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individual pyrolysis, wM is the mass ratio of the mineral during co-pyrolysis, and YO

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and wO are those of organic matter, respectively. According to the differences

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between the experimental and theoretical results, mutual influences between minerals

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and organic matter were evaluated.

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3.2.1 Co-pyrolysis of organic matter and calcium carbonate 8

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The TG/DTG and MS results collected during individual pyrolysis of HDOS-CF

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are shown in Figure 2. The DTG curve indicates that the main pyrolysis reaction starts

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at 400 °C and peaks at 465 °C. MS results indicate that the detectible light volatiles

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include CH4, C2H6, C3H8, C4H10, C6H6 (benzene), C7H8 (toluene), C6H6O (phenol),

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H2, H2O, CO and CO2 with mass-to-charge ratios (m/z) of 15, 27, 29, 43, 78, 91, 94,

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2, 18, 28 and 44, respectively.

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Figure 3 shows the experimental and theoretical results of TG/DTG and light

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volatile products during co-pyrolysis of HDOS-CF and CaCO3. It is noted that all the

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theoretical curves are suffixed with –t. The experimental TG curve (solid line)

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overlaps with the theoretical one (dotted line) before 500 °C and splits gradually after

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then, which is accompanied by a higher experimental mass loss rate after 500 °C (see

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DTG curves). MS results indicate that the amounts of all the light volatile products

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approximate their theoretical values except that the amount of CO2 formed in the

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experiment is clearly more than the theoretical value after 270 °C. Figure 2 indicates

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that HDOS-CF releases CO2 at 200-600 °C which is attributed to the cracking of

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carboxyl functional group in organic matter.19,20 Individual pyrolysis of CaCO3

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(Figure S1 in the supporting information) indicates that the pure CaCO3 cannot

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decompose in this temperature range as expectation. There are two possible reasons

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for more CO2 release: CaCO3 promotes the cracking of carboxyl functional group in

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organic matter;21 the organic matter or pyrolysis products promote(s) a small amount

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of CaCO3 to produce CO2. XRD result of the solid co-pyrolysis product (Figure S2 in

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the supporting information) indicates formation of a small amount of CaO. The more 9

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CO2 release at temperatures lower than 500 °C is probably attributed to the first

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reason while the more CO2 release at temperatures higher than 500 °C and the peak at

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550 °C are probably attributed to the second reason because the carboxyl in

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HDOS-CF is not very much22, 23 and reported to decompose at lower temperatures.24

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The above discussion and the results of organic volatile products indicate that CaCO3

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has little influence on the decomposition of organic matter and volatiles reaction. This

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finding is different from the literature work which showed a promoting effect by

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comparing raw and demineralized oil shale. 6,7,25 It is also different from Hu’s work at

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a lower pyrolysis temperature (520 °C) which showed a negative effect by adding a

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large amount of CaCO3 into kerogen (9:1 in mass).

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amount of CaCO3 in Hu’s work led to a long residence time and thus severe

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condensation of volatiles to form coke which results in an observed mass increase.

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3.2.2 Co-pyrolysis of organic matter and alkali metal carbonates

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It is possible that the large

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Figure 4 shows the experimental and theoretical results of TG/DTG and light

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volatile products during co-pyrolysis of HDOS-CF and K2CO3. The TG curves

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roughly overlap with each other, the experimental mass loss rate (DTG) is slightly

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higher than the theoretical value after 510 °C, and the amount of CO2 generated in the

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experiment is clearly more than the theoretical value. XRD result of the pyrolysis

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solid product indicates formation of K2O (Figure S2), although the pure K2CO3 is

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difficult to decompose at 600 °C. This phenomenon is similar to that of CaCO3 and is

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frequently mistaken as the promoting effect of alkali metal carbonates on organic

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matter pyrolysis. 6,25 10

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MS results indicate that all the organic volatiles generated during co-pyrolysis are

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more than the theoretical values except that the CH4 release after 510 °C is less than

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the theoretical. For clarity, the differences between the experimental and theoretical

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amounts of light volatile products were quantified according to the literatures 26,27 and

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the results are shown in Table 3. To understand the influence of K2CO3 on volatiles

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reaction in detail, generation of the organic volatiles during pyrolysis of fossil fuels

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was reviewed. CH4 is mainly attributed to the cracking of the end of Cal-CH3 and

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Cal/Car-O-CH3 at relatively low temperatures and to the cracking of Car-CH3 at high

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temperatures.28 C2-C4 hydrocarbons are mainly attributed to the cracking of the β site

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of alkyl side chain and methylene bridge linking aromatic rings, which is

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accompanied by the formation of C7H8.29,30 C2-C4 hydrocarbons can also be

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attributed to the cracking of long-chain aliphatic hydrocarbons (the primary pyrolysis

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products).29 C6H6O is mainly attributed to the cracking of Car-O-Cal29,30 and C6H6 may

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be generated by dehydrocyclization of long-chain aliphatic hydrocarbons and

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hydrogenation of phenyl-substituted compounds.31 The H2 release is mainly attributed

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to the dehydrogenation of aliphatic hydrocarbons at low temperatures and

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polycondensation of aromatic compounds at higher temperatures.32 The difference

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between the experimental and theoretical amounts of light volatile products in Table 3

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indicate that K2CO3 or its derivative lowers the cleavage temperature of Car-CH3

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bond, promotes the cracking, dehydrogenation and dehydrocyclization of aliphatic

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chain or hydrocarbons.

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Figure 5 shows the experimental and theoretical results of TG/DTG and light 11

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volatile products during co-pyrolysis of HDOS-CF and Na2CO3. The TG/DTG and

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CO2 release results indicate that Na2CO3, similar to K2CO3, has little effect on the

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decomposition of organic matter. MS results of organic volatile products indicate a

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slight effect of Na2CO3 on volatiles reaction. The experimental and theoretical

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differences of C2-C4 hydrocarbons, H2 and C6H6 in Table 3 indicate that Na2CO3

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promotes the cracking and dehydrocyclization of aliphatic hydrocarbons but the

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promoting extent is less than that of K2CO3.

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3.2.3 Co-pyrolysis of organic matter and manganese carbonate

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Figure 6 shows the experimental and theoretical results of TG/DTG and light

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volatile products during co-pyrolysis of HDOS-CF and MnCO3. The DTG curve of

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the experiment is obviously different from the theoretical one. It has shown that the

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peak at 465 °C is attributed to the decomposition of organic matter (Figure 2). The

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individual pyrolysis of MnCO3 (Figure S5) indicates that MnCO3 decomposition

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yields a peak at 425 °C. In the co-pyrolysis process, the decomposition peak of

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organic matter overlaps with the theoretical one while the decomposition peak of

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MnCO3 moves to 380 and 410 °C. These phenomena indicate that the organic matter

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or pyrolysis products promote(s) MnCO3 decomposition while MnCO3 (or MnO) has

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little effect on the decomposition of organic matter. The MS results of organic volatile

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products indicate that MnO has a slight influence on the volatiles reaction, and the

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data in Table 3 indicate that the effect of MnO is the weakest in comparison with

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K2CO3 and Na2CO3.

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3.3 Mutual influences between organic matter and clay minerals 12

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The clay minerals in Huadian oil shale are mainly kaolinite and montmorillonite.

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Kaolinite is rich in crystal water and the individual pyrolysis of kaolinite (Figure S6)

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indicates that the H2O release starts at 430 °C and peaks at about 525 °C. Figure 7

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shows the experimental and theoretical curves of TG/DTG and light volatile products

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during co-pyrolysis of HDOS-CF and kaolinite. The H2O release is clearly inhibited

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and postponed to higher temperatures during co-pyrolysis, suggesting that the

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pyrolysis products of organic matter inhibit the dehydration of kaolinite. The change

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in H2O release from kaolinite accounts for the change in the DTG curve and results in

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the less mass loss. These information further indicates that kaolinite has little effect on

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the pyrolysis of organic matter, as reported by Hu et al.11 The experimental results of

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all the organic volatiles are identical to the theoretical results, suggesting that the

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kaolinite has little effect on the volatiles reaction.

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Figure 8 shows the experimental and theoretical results of TG/DTG and light

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volatile products during co-pyrolysis of HDOS-CF and montmorillonite. It can be

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seen that the experimental mass loss is less than the theoretical value while the

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experimental volatile products is equal to or more than the theoretical value. These

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phenomena suggest that montmorillonite may promote the reaction of organic

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volatiles (likely heavy fraction) to form coke and light volatiles, as deduced from

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demineralization experiment.10 This result is contrary to the report of Hu et al.11

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(addition of montmorillonite yielded more oil and gas and less coke by an aluminum

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retort), which cannot be explained and needs a further study. In detail, CH4 and H2

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releases during co-pyrolysis roughly overlap with the theoretical releases, suggesting 13

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that montmorillonite has little effect on the dehydrogenation of aliphatic chain or

287

hydrocarbons. Co-pyrolysis yielded more C2-C4 hydrocarbons, aromatic compounds

288

and CO2 at temperatures lower than 450 °C, in comparison with the theoretical values,

289

indicating that the promoting effect of montmorillonite on the reaction of organic

290

volatiles starts at lower temperatures. This observation is consistent with the

291

experimental phenomenon reported by Borrego et al.33

292

3.4 Effects of metal oxides on pyrolysis of organic matter

293

The oxides detectible in Huadian oil shale are Fe2O3 and TiO2. Figure 9 shows the

294

experimental and theoretical results of TG/DTG and light volatile products during

295

co-pyrolysis of HDOS-CF and Fe2O3. It can be seen from the DTG curves that the

296

experimental mass loss rate is larger than the theoretical value at 375-440 °C, equal to

297

the theoretical value at 440-455 °C, and smaller at 455-510 °C. The overall result is

298

that Fe2O3 slightly increases the yield of solid product, which is consistent with the

299

report of Lai et al.13 However, the amounts of the organic volatile products except

300

CH4 generated in the experiment are similar to or larger than the theoretical

301

counterparts. This information suggests that Fe2O3, similar to montmorillonite, also

302

promotes the reaction of heavy organic volatiles to form coke and light volatile such

303

as C6H6, C7H8 and H2. The experimental curves of C2-C4 hydrocarbons, C6H6O

304

overlap with their theoretical curves, indicating that Fe2O3 has little effect on the

305

cracking of long-chain aliphatic hydrocarbons and Car-O-Cal.

306

Figure 10 shows the experimental and theoretical results of TG/DTG and light

307

volatile products during co-pyrolysis of HDOS-CF and TiO2. It is clear that all the 14

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experimental curves overlap with the theoretical counterparts, indicating that TiO2 has

309

little effect on the pyrolysis of organic matter in oil shale.

310

4. Conclusions

311

Effects of carbonates, clay minerals, Fe2O3 and TiO2 on pyrolysis of oil shale’s

312

organic matter were investigated by addition of these minerals into HCl-HF treated

313

Huadian oil shale on TG-MS. The TG result represents the decomposition of organic

314

matter and the MS result represents the volatiles reaction. It is found that the organic

315

matter or pyrolysis products delayed the release of crystal water in kaolinite. All

316

mineral compounds investigated show little influence on the decomposition of organic

317

matter but different effects on the volatiles reaction. In particular, CaCO3, kaolinite

318

and TiO2 have little effect on the volatiles reaction while K2CO3, Na2CO3 and MnCO3

319

promotes the volatiles reaction, including cracking of Cal-Cal bond in alkyl side chain

320

or methylene bridge to yield more C1-C4 hydrocarbons and toluene, and

321

dehydrocyclization of long-chain aliphatic hydrocarbons to form benzene and H2. The

322

effects of carbonates follow the order of K2CO3 > Na2CO3 > MnCO3.

323

Montmorillonite and Fe2O3 promote the condensation of volatiles to form coke and

324

C6H6, C7H8 and H2.

325

Acknowledgment

326

The authors gratefully acknowledge the financial support from the National Basic

327

Research Program of China (2014CB744301).

328

Appendix A. Supplementary material

329

Supplementary data associated with this article can be found, in the online 15

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version, at

331 332

References

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Petrochemical Press, Beijing, 2008. [2] Patterson, J. H. A review of the effects of minerals in processing of Australian oil shales. Fuel 1994, 73 (3), 321-327. [3] Espitalie, J.; Makadi, K.S.; Trichet, J. Role of the mineral matrix during kerogen pyrolysis. Org. Geochem. 1984, 6, 365-382. [4] Yan, J.; Jiang, X.; Han, X.; Liu, J. A TG–FTIR investigation to the catalytic

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effect of mineral matrix in oil shale on the pyrolysis and combustion of kerogen.

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demineralization of EI-Iajjun Jordanian oil shale on oil yield. Fuel Process.

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Technol. 2009, 90 (6), 818-824.

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[9] Chang, Z.; Chu, M.; Zhang, C.; Bai, S.; Lin, H.; Ma, L. Influence of inherent

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mineral matrix on the product yield and characterization from Huadian oil shale

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pyrolysis. J. Anal. Appl. Pyrolysis 2018, 130, 269-276.

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[10]Zhao, X.; Zhang, X.; Liu, Q.; Lu, Z.; Liu, Z. Organic matter in Yilan oil shale:

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characterization and pyrolysis with or without inorganic minerals. Energy Fuels

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[11]Hu, M.; Cheng, Z.; Zhang, M.; Liu, M.; Song, L.; Zhang, Y.; Li, J. Effect of

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Pyrolysis. Energy Fuels 2014, 28 (3), 1860-1867.

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[12]Wood, D. A.; Hazra, B. Characterization of organic-rich shales for petroleum

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exploration & exploitation: A review-part 2: Geochemistry, thermal maturity,

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isotopes and biomarkers. J. Earth Sci. 2017, 28 (5), 758-778.

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[13]Lai, D.; Chen, Z.; Lin, L.; et al. Secondary cracking and upgrading of shale oil from pyrolyzing oil shale over shale ash. Energy Fuels 2015, 29 (4), 2219-2226.

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[15]Guo, S.; Jiang, Y.; Liu, T.; Zhao, J.; Huang, J.; Fang, Y. Investigations on

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Fuel 2018, 214, 561-568. 17

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[17]Burnham, A.K. Chemistry and kinetics of oil shale retorting. Oil shale: A solution

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to the liquid fuel dilemma, American Chemical Society, Washington DC, 2010

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(Chapter 6).

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[18]Totten, M.W.; Hanan, M.A. Chapter 12 Heavy minerals in shales. Developments in Sedimentology 2007, 58, 323-341. [19]Wang, M.; Li, Z.; Huang, W.; Yang, J.; Xue, H. Coal pyrolysis characteristics by TG-MS and its late gas generation potential. Fuel 2015, 156, 243-253.

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[20]Arenillas, A.; Rubiera, F.; Pis, J.J. Simultaneous thermogravimetric-mass

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spectrometric study on the pyrolysis behaviour of different rank coals. J. Anal.

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Appl. Pyrolysis 1999, 50, 31-46.

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[21]Cypre, R.; Furfari, S. Hydropyrolysis of high-sulphur-high-calcite Italian Sulcis

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coal. 1. Hydropyrolysis yields and catalytic effect of the calcite. Fuel 1982, 61,

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[22]Zhao, X.; Liu, Z.; Lu, Z.; Shi, L.; Liu, Q. A study on average molecular structure

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of eight oil shale organic matters and radical information during pyrolysis. Fuel

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2018, 219, 399-405.

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[23]Tong, J.; Han, X.; Wang, S.; Jiang, X. Evaluation of structural characteristics of

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Huadian oil shale kerogen using direct techniques (solid-state

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FT-IR, and XRD). Energy Fuels 2011, 25, 4006-4013.

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NMR, XPS,

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analysis (TG-MS) of lignite coals from Southwest China. J. Energy Inst. 2016, 89,

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94-100.

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of oil shale: Self-heating effect and shale-oil production. Fuel 2014, 118,

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[26]Tiwari, P.; Deo, M. Compositional and kinetic analysis of oil shale pyrolysis using TGA-MS. Fuel 2012, 94, 333-341. [27]Pan, L.; Dai, F.; Huang, J.; Liu, S.; Li, G. Study of the effect of mineral matter on

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the thermal decomposition of Jimsar oil shale using TG-MS. Thermochim. Acta

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2016, 31-38, 627-629.

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[28]Shi, L.; Liu Q.; Zhou, B.; et al. Interpretation of methane and hydrogen evolution

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in coal pyrolysis from the bond cleavage perspective. Energy Fuels 2017, 31,

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429-437.

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[29]Lin, L.; Lai, D.; Guo, E.; Zhang, C.; Xu, G. Oil shale pyrolysis in indirectly

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heated fixed bed with metallic plates of heating enhancement. Fuel 2016, 163,

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48-55.

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[30]Porada, S. The reactions of formation of selected gas products during coal pyrolysis. Fuel 2004, 83, 1191-1196. [31]Piroska, S.; Gabor, V.; Ferenc, T.; Tamas, S. Investigation of subbituminous

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coals by thermogravimetry-mass spectrometry: Part 1. Formation of hydrocarbon

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products. Thermochim. Acta 1990, 170, 167-177.

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[32]Lu, Z.; Feng, M.; Liu, Z.; Zhang, X.; Liu, Q. Structure and pyrolysis behavior of 19

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418

the organic matter in two fractions of Yilan oil shale. J. Anal. Appl. Pyrolysis

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2017, 127, 203-210.

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[33]Borrego, A.G.; Prado, J.G.; Fuente, E.; Guillen, M.D.; Blanco, C.G. Pyrolytic

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behavior of Spanish oil shales and their kerogens. J. Anal. Appl. Pyrolysis 2000,

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Table captions

425

Table 1. Proximate and ultimate analyses of the raw and demineralized oil shale

426

samples

427

Table 2. The contents of main minerals in the raw and demineralized oil shale

428

samples

429

Table 3. The differences between the experimental and theoretical amounts of light

430

volatile products generated by co-pyrolysis of HDOS-CF and carbonates

431

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432

Figure captions

433

Figure 1. XRD patterns of the raw and demineralized oil shale samples.

434

Figure 2. Results of TG/DTG and light volatile products detected by MS during

435

pyrolysis of HCl-HF treated Huadian oil shale (HDOS-CF).

436

Figure 3. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

437

and light volatile products during co-pyrolysis of HDOS-CF and CaCO3.

438

Figure 4. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

439

and light volatile products during co-pyrolysis of HDOS-CF and K2CO3.

440

Figure 5. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

441

and light volatile products during co-pyrolysis of HDOS-CF and Na2CO3.

442

Figure 6. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

443

and light volatile products during co-pyrolysis of HDOS-CF and MnCO3.

444

Figure 7. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

445

and light volatile products during co-pyrolysis of HDOS-CF and kaolinite.

446

Figure 8. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

447

and light volatile products during co-pyrolysis of HDOS-CF and montmorillonite.

448

Figure 9. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

449

and light volatile products during co-pyrolysis of HDOS-CF and Fe2O3.

450

Figure 10. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

451

and light volatile products during co-pyrolysis of HDOS-CF and TiO2.

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Table 1. Proximate and ultimate analyses of the raw and demineralized oil shale

454

samples

455

Sample

Mad

Aad

Vad

FCad

Cdaf

Hdaf

Ndaf

O*

Sorg, daf

H/C

HDOS

2.83

70.27

22.30

4.51

60.16

8.13

1.44

30.03

0.24

1.62

HDOS-CF

1.20

15.65

60.85

22.30

66.96

8.03

1.7

20.81

2.50

1.44

*

by difference

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456

Table 2. The contents of main minerals in the raw and demineralized oil shale

457

samples Mineral content (wt.%) Sample SiO2

Al2O3

Fe2O3

SO3

CaO

K2O

TiO2

MgO

Na2O

MnO

HDOS

36.07

18.09

3.13

5.03

3.30

1.47

1.16

0.39

0.73

0.14

HDOS-C

35.16

17.74

1.94

4.77

0.31

0.11

1.13

0.33

0.34

0

HDOS-CF

0.68

0.81

1.61

4.58

0.15

0.13

0.55

0.09

0.01

0

458

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Table 3. The differences between the experimental and theoretical amounts of light

460

volatile products generated by co-pyrolysis of HDOS-CF and carbonates CH4

C2-C4

C6H6

C7H8

C6H6O

H2

(×10-4)

(×10-4)

(×10-4)

(×10-5)

(×10-5)

(×10-3)

CaCO3

0.10

0.20

0.12

0.04

0.03

0.02

K2CO3

-0.95

2.31

1.01

1.44

0.13

1.72

Na2CO3

-0.21

2.02

0.41

0.57

0.02

0.80

MnCO3

-0.40

1.10

0.38

0.61

0.05

0.32

Minerals

461 462

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464 465 466 467

Figure 1. XRD patterns of the raw and demineralized oil shale samples. (Q: quartz; K: kaolinite; M: montmorillonite; C: calcite; H: hematite; P: pyrite; N: NaMgAlF6H2O)

468

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Figure 2. Results of TG/DTG and light volatile products detected by MS during pyrolysis of HCl-HF treated Huadian oil shale (HDOS-CF).

472

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Figure 3. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and CaCO3.

476

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Figure 4. Experimental (solid lines) and theoretical (dotted lines) results of

479

TG/DTG and light volatile products during co-pyrolysis HDOS-CF and K2CO3.

480

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Figure 5. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and Na2CO3.

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Figure 6. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and MnCO3.

488

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Figure 7. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and kaolinite.

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Figure 8. Experimental (solid lines) and theoretical (dotted lines) results of

496

TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and

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montmorillonite.

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Figure 9. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG and light volatile products during co-pyrolysis of HDOS-CF and Fe2O3.

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Figure 10. Experimental (solid lines) and theoretical (dotted lines) results of TG/DTG

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and light volatile products during co-pyrolysis of HDOS-CF and TiO2.

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