Coal Liquefaction Catalysts Research Articles

Adsorption and transfer behaviors of hydrogen on Fe1-xS catalysts for direct coal liquefaction

Direct coal liquefaction (DCL) is an important and effective method to convert coal into chemicals and fuel oil. Pyrite catalysts play an important role in improving the hydrogenation and liquefaction efficiency of coal. There have been many studies on its active component Fe1-xS in promoting pyrolysis of coal and producing active hydrogen, but studies about the hydrogen migration on Fe1-xS catalyst and the interaction between hydrogen and Fe1-xS catalyst were rarely reported. It is significant to study the hydrogen transfer behaviors on Fe1-xS in DCL and understand the influence of Fe1-xS on the hydrogen migration process. In this study, the chemical adsorption and desorption of hydrogen on Fe1-xS were firstly proved experimentally. After pre-sulfidation of Fe1-xS, the maximum amount of H chemically adsorbed in Fe1-xS is 8.20 mmol/g at 360 °C and 1.5 h. The dehydrogenation of Fe1-xS in an anthracene (ANT) system and re-hydrogenation of that in the hydrogen supply systems, such as H2 and 1,2,3,4-tetrahydronaphthalene (THN), were explored at different experiment conditions, which gave some quantitative results of hydrogen transfer. Particularly, the dehydrogenation of Fe1-xS in the ANT system was analyzed in thermodynamics. The enthalpy of dehydrogenation of Fe1-xS in the ANT system is 117.6 kJ mol−1. The results break the traditional view about Fe1-xS only as a medium for active hydrogen transfer and provides a new perspective for further understanding the hydrogen transfer process.

The impact of nitrogen-containing compounds on the S-vacancies over the iron-based catalysts for direct coal liquefaction during the pre-sulfurization process

To advance the direct coal liquefaction (DCL) technology by a “Catalytic cycle of hydrogen donor solvents” pathway, it wasimportantfor the iron-based DCL catalyst to be pre-sulfurized under a suitable condition. In this report, the effect of liquid medium in the slurry bed pre-sulfurization process on iron-based catalyst was studied. Catalysts were pre-sulfurized under a variety of liquid mediums including alkanes, aromatics and heteroatom-containing compounds and the activity were evaluated according to their performance on hydrogenation of naphthalene. It was observed that, the nitrogen-containing medium give rise to the significant negative influence on the catalytic activity (with only 2.5 %-15.3 % of naphthalene conversions). Multiple spectroscopic and microscopic analyses of catalysts exhibited that the decrease of S vacancies was mainly responsible for the low activity. It was due to the promotion effect on Fe1-xS crystallization and troilite generation. S vacancies of the iron-based catalysts was considered as Lewis acid sites to catalyze the hydrogenation reaction. The new findings from this work is beneficial for the development and optimization of pre-sulfurization technology.

Effect of sulfidation temperature on component transformation and catalytic performance of direct coal liquefaction catalyst

A series of iron sulfide catalysts were prepared in 5% H2S/N2 atmosphere at different pre-sulfidation temperatures, and their catalytic activity for naphthalene hydrogenation was studied at 360°C in 1% H2S/H2 atmosphere at 5MPa. The component transformation of the catalyst under varied pre-sulfidation temperature and reaction conditions was researched using MES, XRD and XPS. The results revealed that the sulfidation process was in the form of sulfurizing from surface to interior in the order of FeS2→FeS, Fe1−xS→Fe3S4→Fe2O3 during which transferring sulfur to the body phase was benefited from the rise of temperature. After contacting 1% H2S/H2 gas, the particles rapidly transformed to Fe1−xS from outside to the inside. By adjusting sulfidation conditions, the Fe1−xS content was high while the particle size was small, which made it possible to obtain the greatest activity of the catalyst.

Research of hydrogen action during pre-sulfidation of direct coal liquefaction catalyst

A series of iron sulfide catalysts were prepared by pre-sulfidation at different temperatures and different hydrogen partial pressures, and their catalytic naphthalene hydrogenation activities were studied under 5 MPa 1% H2S-H2 atmosphere at 360 °C. By means of XRD, MES, SEM-EDS, ICP and GC-MS, the effect of hydrogen on the pre-sulfidation process at different temperatures is studied. The results show that the introduction of hydrogen during the pre-sulfidation process facilitates the transfer of sulfur, thereby promoting the sulfidation. Different temperatures are favorable for the formation of Fe1–xS, but the effect of hydrogen is different at different pre-sulfidation temperatures. When pre-sulfidation at 50 °C, the introduction of hydrogen can be beneficial to the transfer of sulfur, which increases the catalytic activity, a lot of elemental Fe and elemental S can be observed at this temperature; when pre-sulfidation at 150 °C, the catalytic activity is the best. The content of elemental Fe decreases and no elemental S is observed. With the increase of hydrogen partial pressure, the hydrogenation conversion rate of naphthalene increases from 60.6% to 69.1%. When pre-sulfidation at 300 °C, the catalytic activity decreased to varying degrees. Hydrogen reduces the sulfur on the catalyst surface to a low valence state and crystalline Fe3O4 is observed inside the catalyst particles, which is not conducive to the transfer of sulfur.

Room-Temperature Solid-State Preparation of CoFe2O4@Coal Composites and Their Catalytic Performance in Direct Coal Liquefaction

Iron-based catalysts are promising catalysts in the direct coal liquefaction (DCL) process as they are inexpensive and environmentally friendly. However, most such iron-based catalysts show relatively low activity in coal conversion and oil yield. Common techniques for the synthesis of these catalysts with excellent catalytic performance remain a substantial challenge. We present a simple solid-state synthesis strategy for preparing CoFe2O4 nanoparticles and CoFe2O4 nanoparticles supported on coal (CoFe2O4@coal) composites for DCL. The obtained bimetallic oxide CoFe2O4 nanoparticles show an enhanced catalytic performance in the DCL compared with monometallic components Fe2O3 and Co(OH)2 nanoparticles. The synergistic effect between Co and Fe of CoFe2O4 nanoparticles promotes the catalytic hydrogenation of coal during the DCL process. Moreover, the catalytic performance of CoFe2O4 nanoparticles is further improved when they are loaded on the coal. The conversion, oil yield, liquefaction degree, and gas yield of Dahuangshan lignite are 99.44, 56.01, 82.18 and 19.30 wt %, respectively, with the CoFe2O4@coal composites involved. The smaller particle size and high dispersion of CoFe2O4 supported on coal are of great benefit to full contact between coal and active components. The in-situ solid-state synthesis with coal as support shows great potential to prepare effective iron-based catalysts toward DCL in practice.

Colombian metallurgical coke as catalysts support of the direct coal liquefaction

A Colombian metallurgical coke was modified in its surface chemistry and was used as support of iron sulfide catalysts for direct coal liquefaction. The modification was made by treatments with diluted oxygen and HNO3 at different conditions. Changes in surface chemistry were studied by determining the point of zero charge (PZC), the isoelectric point (IEP), thermogravimetric analysis (TGA), temperature programmed decomposition-mass spectrometry (TPD-MS), Diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and nitrogen adsorption at 77 K. The results show that the materials obtained have a wide range of functional groups incorporated in a different proportion and quantity. The textural parameters indicate that treatment with diluted oxygen increases the surface area and incorporates micropores while the samples treated with HNO3 maintain the textural properties of the original material. The catalysts were also characterized by Raman spectroscopy. It was found that impregnation with the iron sulfide precursor does not significantly affect the Raman characteristics of the support. Additionally, XRD analysis shows smaller pyrite crystallites in the coke enriched with oxygenated groups of phenol and lactone indicating better dispersion of the active phase. The amount of oxygen chemisorbed per gram of catalyst shows that both, oxygen and nitric acid treatments, improve the relative dispersion of the active phase. It was found that the presence of the catalysts increases the conversion and yields towards oils and gases with respect to those of the tests without catalysts. Cokes modified by dilute oxygen gaseous treatment contain surface phenol and lactone groups and present the highest yield to oils.

Characterization of direct coal liquefaction catalysts by their sulfidation behavior and tetralin dehydrogenation activity

Direct coal liquefaction (DCL) involves complex catalytic reactions and catalyst transformation. These catalyst behaviors are not well revealed and correlated with the DCL results in the past due to large errors in conventional high-pressure autoclave experiments, which are slow in heating rate and complex in product separation and quantification. To better understand transformation of DCL catalysts and evaluate their activity, this paper studies activity of seven DCL catalysts in dehydrogenation of tetrahydronaphthalene (THN or tetralin) using a high throughput method and compare the results with the catalytic activity in DCL in a conventional high-pressure autoclave. The catalysts' activities in THN dehydrogenation and in DCL are correlated with their sulfidation behaviors observed in temperature-programmed heating in a 5%H2S/H2 atmosphere. It is found that the catalysts show the same activity order in THN dehydrogenation and in DCL. The rate constant of THN dehydrogenation and coal conversion and oil yield in DCL correlate well with S content of the catalysts at reaction conditions. Regardless of the metal forms and the catalysts' preparation methods, linear trends are observed: the higher the catalysts' S content, the lower the activation energy for THN dehydrogenation, and the higher the coal conversion and oil yield in DCL. This finding provides a general role as well as easy methods for assessing the catalysts' activity in the direct coal liquefaction, i.e. the catalysts' DCL activity can be evaluated by their S contents or by their activities in THN dehydrogenation.

Direct Coal Liquefaction with Fe3O4 Nanocatalysts Prepared by a Simple Solid-State Method

Fe3O4 nanoparticles were prepared by a simple solid-state method under ambient conditions. The obtained nanoparticles, with small size and large surface area, were used as a catalyst for direct coal liquefaction (DCL). The results display that high conversion and oil yield were achieved with the nanocatalysts in direct liquefaction of two kinds of coals, i.e., Heishan coal and Dahuangshan coal. The effects of the temperature, initial H2 pressure, and holding time on conversion and product distribution have been investigated in the catalytic hydrogenation of Dahuangshan coal. The optimal reaction condition for DCL in which conversion and oil yield are 96.6 and 60.4 wt % was determined with Fe3O4 nanocatalysts. This facile solid-state route is beneficial for scale-up synthesis of iron-based catalysts with good performance for DCL.

57.石炭液化触媒の実用化に関する検討 : 水酸化鉄系鉄鉱石の性状と液化反応特性

57.石炭液化触媒の実用化に関する検討 : 水酸化鉄系鉄鉱石の性状と液化反応特性

2-14.石炭液化反応における鉄触媒の低温活性発現機構(Session(2)石炭利用)

2-14.石炭液化反応における鉄触媒の低温活性発現機構(Session(2)石炭利用)

1-18.石炭液化触媒の実用化検討(2) : インドネシア産Ni含有リモナイトの性状と液化活性(Session 1 石炭・重質油)

1-18.石炭液化触媒の実用化検討(2) : インドネシア産Ni含有リモナイトの性状と液化活性(Session 1 石炭・重質油)

1-5.石炭液化反応における鉄触媒の活性(Session(1)石炭転換反応における触媒の役割)

1-5.石炭液化反応における鉄触媒の活性(Session(1)石炭転換反応における触媒の役割)

23.1t/d PSUにおける石炭液化誠験 : 生成物収率に及ぼす液化触媒種の影響

23.1t/d PSUにおける石炭液化誠験 : 生成物収率に及ぼす液化触媒種の影響

Coliquefaction behaviours of Shenhua coal and sawdust catalysed by different catalysts

AbstractColiquefactions of a subbituminous coal and sawdust over four different coal liquefaction catalysts were studied, and the coliquefied products were characterised by elemental analysis, Fourier transform infrared spectroscopy and gel permeation chromatogram measurements. It is found that FeS+S and Co–Mo/Al2O3 catalysts have the highest catalytic activity for the liquefaction of Shenhua coal and sawdust respectively. There exists synergistic effect in the coliquefaction of Shenhua coal and sawdust, and the main synergistic interaction is reflected by the promotion of preasphaltene formation. The catalytic activities of the four catalysts in the coliquefaction are quite different from their catalytic activities in the individual liquefaction of coal and sawdust. FeS gives the lowest catalytic activity for the coal liquefaction among the four catalysts but has the highest promotion to the synergistic effect in conversion in the coliquefaction of Shenhua coal and sawdust. diminishes this synergistic ef...

Humic acid-Fe as catalyst for coal liquefaction

Research to increase the activity of iron based catalysts focuses on decreasing the particle size, increasing catalyst dispersion. The chelate compound of iron with humic acid (HA), which macromolecules radii can range from 6 to 50 nm, is truly in a highly dispersed state. Fe2+ or Fe3+ were dispersed finely into the HA matrix through the ion exchange with -COOH groups or chelate with carbonyl group in humic acid macromolecules. X-ray diffraction (XRD) and FT-IR spectrophotometer were used to characterize iron species before or after chelating with humic acid. The results indicate that there exist α-FeOOH, ferrihydrite and amorphous iron in HA-Fe. Most of the work has been conducted on a laboratory scale, and the results show that HA-Fe catalyst was approved for its excellent catalytic activity in coal liquefaction, and the conversion and oil yield of coal have been greatly improved.

Preparation and Catalytic Performance of Fe-Cr-Si-Pillared Montmorillonite as Coal Liquefaction Catalyst

A set of pillared montmorillonite (PILM) catalysts were prepared by exchanging Na+ with iron pillars, chromium pillars, complexes pillars of iron and chromium with different proportion, as well as complexes pillar of silica sol and iron and chromium, respectively. X-ray diffraction (XRD), X-ray fluorescence (XRF), thermogravimetry (TG) and differential thermal analysis (DTA) were used to characterize the catalysts. The XRD results reveal that Fe-Cr complexes pillared montmorillonites (Fe/Cr-PILM) have the basal spacing of about 2.04 nm after calcination at 300 °C for 2 h, while sole metal PILM have that of about 1.0 nm; in particular, the basal spacing of silica sol complexes pillared montmorillonite (Fe-Cr-Si-PILM) are expanded up to 4.33 nm. The TG-DTA results show that both Fe-Cr-PILM and Fe-Cr-Si-PILM have high thermal stability up to 640 °C. Catalytic activity of Fe/Cr-Si-PILM in Longkou lignite (LL) and ShengLi coal residue (SCR) liquefaction was studied, which showed that PILM had a good catalytic performance in coal conversion field.

Co-liquefaction of rice straw and coal using different catalysts

Co-liquefactions of a Chinese Shenfu sub-bituminous coal (SFSBC) and rice straw (RS) over four different coal liquefaction catalysts were carried out and the co-liquefied product preasphaltene (PA) was characterized by elemental analysis, FTIR and gel permeation chromatograms (GPC) measurements. It was found that the four catalysts gave different catalytic activities in the liquefaction of SFSBC and RS alone. CoMo/Al2O3 and SO42-/ZrO2 promoted the oil formation for RS liquefaction due to their solid acidic property, but FeS+S gave the highest catalytic activity for the liquefaction of SFSBC among the four catalysts used in this study. There existed a positive synergistic effect in the co-liquefaction of SFSBC and RS, and the main synergistic interaction was reflected by the promoted formation of oil and PA. The catalytic activities of the four catalysts in the co-liquefaction were quite different from their catalytic activities in the individual liquefaction of SFSBC and RS. FeS gave the lowest catalytic activity for the coal liquefaction alone among the four catalysts, but had the highest promotion to the synergistic effect in the total yield of liquefaction products in the co-liquefaction of SFSBC and RS. SO42-/ZrO2 diminished this synergistic effect for the co-liquefaction of SFSBC and RS due to its solid acidic property. It was found that the four catalysts used have higher catalytic activity for the PA, which is from coal liquefaction and converting this part of PA into AS and oil fraction. The average molecular weights of PAs from SO42-/ZrO2 and CoMo/Al2O3 catalysts were lower than those of PAs from FeS and FeS+S catalysts, suggesting that the catalytic hydrogenation activities of SO42-/ZrO2 and CoMo/Al2O3 are higher than those of FeS and FeS+S catalysts.

Role of Iron-Based Catalyst and Hydrogen Transfer in Direct Coal Liquefaction

The aim of this research is to understand the major function of iron-based catalysts on direct coal liquefaction (DCL). Pyrolysis and direct liquefaction of Shenhua bituminous coal were carried out to investigate the effect of three solvents (wash-oil from coal-tar, cycle-oil from coal liquefaction, and tetralin) in a N2 or a H2 atmosphere and with or without catalyst. The hydrogen content in the solvent and liquid product and the H2 consumption for every run were calculated to understand the hydrogen transfer approach in DCL. The results showed that the iron-based catalyst promotes the coal pyrolysis, and the dominating function of the catalyst in DCL is to promote the formation of activated hydrogen and to accelerate the secondary distribution of H in the reaction system including the gas, liquid, and solid phases. The major transfer approach of the activated hydrogen is from molecular hydrogen to solvent and then from solvent to coal, and the solvent takes on the role of a “bridge” in the hydrogen tran...

Highly active limonite catalysts for direct coal liquefaction

The properties of limonite in Australia and Indonesia were examined by using X-ray diffraction, Mössbauer spectroscopy, Thermal gravimetric analysis (TGA) and TEM–EDX in relation to the catalytic activities in the liquefaction of low-rank coals. The molar ratio of H 2O/Fe in limonite was determined from the weight loss resulting from the dehydration reaction of FeOOH to Fe 2O 3 during heating from 120 to 400 °C in TGA. The H 2O/Fe molar ratio varied from 0.06 for hematite to 0.60 for limonite YY, depending on the hematite content. Results from the pulverization tests showed that the higher value of H 2O/Fe molar ratio resulted in lesser abrasion of medium balls. A unique limonite YY in Australia, containing no hematite, was easily pulverized to sub-micron particle size and showed an excellent oil yield in coal liquefaction. It appeared that H 2O/Fe molar ratio could be one of the most important factors to select the better limonite catalyst for coal liquefaction. Moreover, it was found that Ni containing limonite SO in Indonesia exhibited a higher liquefaction activity than YY catalyst, because of transformation into a smaller crystallite size of pyrrhotite (Fe 1− x S). The agglomeration of pyrrhotites may be suppressed by a strong interaction between FeOOH and Al(OH) 3 such as Fe–O–Al. TEM–EDX analysis suggests that Ni may be located near the Fe 1− x S structure. Oil yield was significantly increased from 43 to 62 wt% daf by CLB addition to the coal slurry in the liquefaction of Banko coal. Finely pulverized limonite catalyst (SO) can be advantageously used in a commercial plant for coal liquefaction in Indonesia due to the low catalyst cost and a high liquefaction activity to obtain a high oil yield.

Improvement and characterization of an impregnated iron-based catalyst for direct coal liquefaction

An impregnation method to prepare an active iron-based catalyst for direct coal liquefaction was improved. With the same catalytic activity, the water usage in the improved method is only 1% of that used in the unmodified method. The improved method not only simplifies the impregnation procedure and reduces cost, but also generates small catalyst particle size on coal surface. Water in the coal promotes thermal liquefaction, but deactivates the impregnated catalyst (possibly due to the adsorption of H 2O molecular on the catalyst surface). Electron probe microanalysis (EPMA), X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) analyses show that the catalyst precursors prepared by both methods are in nanometer size and highly dispersed on coal surface. The irons deposited on coal surface are not only in sulfide forms, but also coordinate with oxygen from moisture- and oxygen-containing groups of coal. The impregnated iron may be composed of FeOOH and FeS or in the forms of Fe–O–S or Fe–S–O. The iron transforms to crystalline pyrrhotite in coal liquefaction.