Catalytic hydroconversion of derivates from Naomaohu lignite over an active and recyclable bimetallic catalyst

doi:10.1016/j.fuproc.2020.106388

Fuel Processing Technology

Volume 204, July 2020, 106388

https://doi.org/10.1016/j.fuproc.2020.106388 Get rights and content

Highlights

•
Fe-Ni-S/AP is effective for catalyzing the cleavage of bridged linkages.
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More organic matter in R₁ was converted into SP_II via CHC procedure.
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SP_CHC is rich in arenes and arenols, while SP_NCHC is dominated by non‑nitrogen ketones.

Abstract

Fe/attapulgite powder (AP), Ni/AP, and Fe-Ni/AP were prepared by thermally decomposing iron pentacarbonyl (IPC), nickel tetracarbonyl (NTC), and different molar ratios of IPC to NTC onto AP in ethoxyethane, respectively. Their activities for the catalytic hydrocracking of di(1-naphthyl)methane (DNM) were compared under the same conditions. As a result, the activity of Fe-Ni-S/AP (Fe:Ni = 2:1) for DNM hydrocracking is significantly higher than that of other catalysts used. DNM conversion is near 100% over Fe-Ni-S/AP with Fe:Ni = 2:1. Over the catalyst, H₂ can be effectively split to H radical dot , which attacks the ipso-position of DNM to cleave the C_ar-C_alk bridged bond in DNM. Naomaohu lignite was subjected to thermal dissolution/ethanolysis in ethanol to afford soluble portion 1 (SP₁, yield 56.0%) and residue 1 (R₁) followed by non-catalytic hydroconversion (NCHC) and catalytic hydroconversion (CHC) of SP₁ and R₁ at 300 °C using Fe-Ni-S/AP with Fe:Ni = 2:1 as the catalyst to afford SP_NCHC, SP_CHC, SP₂ (yield 2.3%), and SP_II (yield 11.2%). According to gas chromatography/mass spectrometric analysis, arenes are the most abundant in SP_CHC, accounting for 21.9%, while the most abundant group component in SP_NCHC are non‑nitrogen ketones, accounting for 20.0%.

Graphical abstract

Introduction

Lignites are abundant in natural resources over the world [1,2]. In spite of their large-scale exploitation and low transportation costs, they are not used as widely as higher-rank coals owing to their high contents of moisture, mineral matter, and organic oxygen [3]. Lignites are also rich in aromatic rings (ARs), most of which are connected by bridged linkages (BLs). Since many aromatics are value-added chemicals, cleaving the BLs facilitates producing the aromatics and achieving the value-added utilization of lignites.

Thermal dissolution (TD), especially TD in an alkanol, is an important approach for obtaining more soluble portion (SP) [4] from lignites compared to room-temperature (RT) extraction. In fact, at elevated temperatures, TD in an alkanol involves in both TD and alkanolysis. However, such a SP is still rich in macromolecular species, including heteroatom-containing components, in which many ARs could be connected by BLs. Therefore, for value-added use of the SP, cleaving the BLs and removing the heteroatoms are needed. On the other hand, different from both lignites themselves and their derived SP, organic matter in the residues from the TD/alkanolysis of lignites only consists of insoluble macromolecular species. So, using a residue as the reactant can avoid the disturbance of inherent soluble species on the product analysis.

Catalytic hydroconversion (CHC) of coals in non-polar solvents at low temperatures attracts wide attention in recent years [[5], [6], [7]]. Transition metals, especially precious metals [[8], [9], [10]], are applied for catalyzing AR hydrogenation at lower temperatures [11], but the high price and difficulty in recycling limit the practical application of precious metals. A series of sulfided bimetallic catalysts, such as nickel‑tungsten and nickel‑molybdenum sulfides, were used for hydrocracking, hydrodearomatization, and hydrodesulfurization [[12], [13], [14], [15], [16]]. Nickel tetracarbonyl (NTC) proved to be an important precursor for preparing highly dispersed metallic nickel loaded on a support [17], while attapulgite powder (AP) is an unusual support owing to its microfibrous morphology, high specific surface area (SSA), remarkable thermal stability, and low price [18,19]. Similar to NTC, iron pentacarbonyl (IPC) can also be thermally decomposed in situ on a support for preparing highly dispersed metallic iron loaded on a support. So, in-situ thermally decomposing both NTC and IPC on AP could prepare an active bimetallic catalyst.

Di(1-naphthyl)methane (DNM) contains 2 naphthalene rings connected by 2 C_ar-C_alk bonds, which are strong covalent bonds (SCVBs). So, DNM is well used as a coal-related model compounds and H radical dot transfer proved to be an effective approach for cleaving the SCVBs, especially over a metal‑sulfur system [20,21] or an activated carbon (AC)‑sulfur system [22].

Taking the above consideration into account, we tried to prepare Fe-Ni/AP by in-situ thermally decomposing both NTC and IPC on AP. Using the catalyst with sulfur addition, we examined DNM hydrocracking under different conditions and compared the CHC and non-CHC (NCHC) of both SP and residue from TD/ethanolysis (E).

Section snippets

Catalyst preparation

AP was added into a 500 mL round flask with 0.5 mol L⁻¹ aqueous HCl solution with agitation for 4 h followed by centrifugating the mixture with deionized water several times to remove unreacted HCl. Then the AP was calcined in a tubular furnace at 350 °C for 4 h and pulverized to pass through a 200-mesh sieve followed by desiccation in vacuum at 80 °C for 24 h before use.

IPC and NTC were synthesized in a 100 mL stainless-steel autoclave. Iron or nickel powders were added into the autoclave.

Catalyst characterization

As observed in Fig. 2, Fig. 3, the surface of AP is very smooth, while the surfaces of Fe/AP, Ni/AP, and Fe-Ni/AP (Fe:Ni = 2:1) are rough. Besides, according to the analysis with inductively coupled plasma mass spectrometer, the contents of Fe and Ni in Fe-Ni/AP are 21.1% and 9.0%, respectively (Table S2), indicating that Fe and Ni nanoparticles (NPs) are supported on the AP surface.

As for AP, the diffraction peaks (DPs) of Si-O-Si crystal layer at 8.5^o and 16.9^o and the DPs of quartz at 35.1^o,

Conclusions

Fe-Ni-S/AP proved to be active for catalyzing the cleavage of BLs connecting ARs and has a good stability and recylability. By the TD/E of NL and subsequent CHC of the resulting SP₁ and R₁ over Fe-Ni-S/AP, the total yield of the SPs, i.e., SP₁ and SP_II reaches 67.2%. More NAs^I, BAs^I, cyclanes, arenes (especially ASBs^I), and ASPs^II exist in SP_CHC, while NNKs and esters are abundant in SP_NCHC and most of the NNKs contain ARs.

Declaration of competing interest

Mei-Ling Xu, Xian-Yong Wei, De-Wu Meng, Feng-Hai Li, Yun-Peng Zhao, Yu-Hong Kang, Zhi-Min Zong, Guang-Hui Liu, Sheng Li, Yan Xue, Fang-Jing Liu, Xing Fan, Jing-Pei Cao, Wei Zhao, Feng-Yun Ma, and Jing-Mei Liu declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was financially supported by the Key Project of Joint Fund from National Natural Science Foundation of China and the Government of Xinjiang Uygur Autonomous Region (Grant U1503293) and the National Key Research and Development Program of China (Grant 2018YFB0604602).

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Research articleCatalytic hydroconversion of derivates from Naomaohu lignite over an active and recyclable bimetallic catalyst

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Catalyst preparation

Catalyst characterization

Conclusions

Declaration of competing interest

Acknowledgements

Appl. Energ.

Fuel

Fuel

Fuel Process. Technol.

Fuel

J. Catal.

Catal. Today

Fuel

Catal. Today

Fuel Process. Technol.

Fuel Process. Technol.

Fuel

Fuel

Fuel

Fuel Process. Technol.

Research article
Catalytic hydroconversion of derivates from Naomaohu lignite over an active and recyclable bimetallic catalyst