Comparison of Superacid-Catalyzed Depolymerization and Thermal Depolymerization of Bituminous CoalCatalysis by Superacid HF/BF₃ and Synthetic Pyrite

Abstract

Depolymerization of bituminous coal by conventional thermal reaction, both with and without a synthetic pyrite catalyst, and a superacid-catalyzed reaction using a mixture of hydrogen fluoride and boron trifluoride were examined to study differences between radical and ionic reactions in coal depolymerization. All reactions took place under hydrogen without any solvent. Depolymerization of bituminous Miike coal was comparatively homogeneous following the superacidcatalyzed reaction with HF/BF 3 , but was heterogeneous following the thermal reaction using the synthetic pyrite catalyst. Because a reaction temperature of 440 °C was required to cleave the linkages between the coal molecules, the thermal reaction probably promoted dealkylation (removal of alkyl side chains) as well as simultaneously promoting negative reactions such as condensation. In contrast, the superacid-catalyzed reaction at 150 °C predominantly promoted coal depolymerization and did not cause significant dealkylation, providing a highly soluble product. The synthetic pyrite catalyst accelerated deoxygenation of coal, resulting in higher extractability than that following the thermal reaction without a catalyst although the synthetic pyrite catalyst does not have substantial hydrogenation catalytic activity in the presence of gaseous hydrogen.

A Novel Magnetic Solid Acid for Specially Cleaving the C‐O Bridged Bond in Dibenzyl Ether

“…The attack of H + to oxygen atom produces an intermediate (IM1) in which the oxygen atom owns positive charge, then generates a transition state (TS1) and the instable transition state will be broken into benzyl alcohol and benzyl cation (IM2) . In acid environment, benzyl alcohol is attacked by H + to afford protonated benzyl alcohol intermediate which subsequently loses H 2 O to produce benzyl cation again . The benzyl cation combines with H − to generate toluene (P1) …”

“…[21] In acid environment, benzyl alcohol is attacked by H + to afford protonated benzyl alcohol intermediate [22] which subsequently loses H 2 O to produce benzyl cation again. [23] The benzyl cation combines with H À to generate toluene (P1). [24] A part of benzyl cation attacks the benzene ring orthoposition of benzyl alcohol to produce intermediate (IM3).…”

Direct liquefaction techniques on lignite coal: A review

“…Nevertheless, to obtain useful fuels or low-molecular-weight chemicals from low-ranking coals in reduction reactions, high reducing gas pressures and active catalysts to stabilize small fragments have been found to be indispensable [54][55][56]. Suitable sufficiently cheap catalysts are mainly iron-based (hydroxide, sulfate, pyrite), although other metals and their oxides, halides, or sulfides have been used [57]. To minimize the catalyst deactivation, it is desirable to use coals containing low concentrations of nitrogen and sulfur [56] and to remove inorganic components and other impurities prior to the reaction [58].…”

Compositional Features of the Light Fraction from One/Two‐Step Effective Cascade Catalytic Hydroconversion of the Extraction Residue from Naomaohu Lignite

“…In recent years, significant efforts have been devoted to directional degradation of coals and coal‐related model compounds (CRMCs) over heterogeneous catalysts because they meet the requirements of high‐performance and eco‐friendly features [19–24] . In particular, solid superacids and supported metals were currently paid attention for catalyzing H + transfer, leading to the cleavage of some bridged bonds, especially CCBBs [25–34] . Many researchers explored the reaction of di(1‐naphthyl)methane catalyzed over SSAs and proposed the hydroconversion mechanism was attributed to the cationic reaction.…”