•TDSF is almost completely liquefied at 380 °C with high yield of oil + gas.•The model of hydro-liquefaction of TDSF includes series and parallel reactions.•The regressive reaction is ruled out in the model.•TDSF to PA and PA to oil + gas are the main reactions.•Oil + gas are mainly formed from the reaction of PA to oil + gas.Thermal dissolution (TD) of coal and hydro-liquefaction of the thermal dissolution soluble fraction (TDSF) with a high activity catalyst is one of effective high efficient hydro-liquefaction of coal techniques. In this study, a Chinese Shenfu (SF) sub-bituminous coal was thermally dissolved, and the TDSF obtained was further hydro-liquefied with Ni–Mo-S/Al2O3 catalyst. Based on the hydro-liquefaction results, a model including series and parallel reactions was established for the hydro-liquefaction of TDSF catalyzed by Ni–Mo-S/Al2O3, and the regressive reactions were ruled out in the model. From the kinetic parameters calculated, it suggested that the regressive reactions including the char formation reactions were negligible in the hydro-liquefaction of TDSF catalyzed by Ni–Mo-S/Al2O3. The reactions of TDSF to preasphaltene and preasphaltene to oil + gas predominated the formation of oil + gas. Ni–Mo-S/Al2O3 could decrease the activation energy of preasphaltene to oil + gas reaction, thus promoting the formation of oil and gas in the catalytic hydro-liquefaction of TDSF.

•EMIA shows high performance on the dissolution of lignites.•Extraction temperature and lignite type significantly affect extraction behaviors.•Extraction yield increases with the increase of carboxyl content of lignites.The extraction behaviors of three lignites with ionic liquid (IL)-1-ethyl-3-methylimidazolium acetate (EMIA) were studied in this work. The effects of extraction temperature and lignite type on extract yield and product compositions were primarily investigated. Also the relationship between the extract yield of lignites and the quantities of oxygen-containing functional groups in lignites was investigated. It was found that EMIA is a more efficient solvent for the dissolution of lignites compared to the performance of 1-butyl-3-methyl-imidazolium chloride (BMIC). Extraction temperature and lignite type significantly affect extraction behaviors of lignite with EMIA. The extract yield of lignites with EMIA increases with the quantity of carboxylic groups in lignite increases. Only a small amount of aliphatic alkyl structure components are extracted at low temperature. More aromatic structure components are extracted by EMIA at high extraction temperature.

•A fat coal was thermal dissolved giving TDSFs with different caking property.•TDSF from higher temperature contained more OH groups with lower caking property.•TDSF from nonpolar solvent had less aromatic compounds with higher caking property.•Addition of TDSF into coal blends can increase the quality of metallurgic coke.In the coal blending for coke-making, fat coal has a very important role for the caking and coking properties of the coal blends. In this study, a fat coal was thermally dissolved, and the caking and coking properties of the thermal dissolution soluble factions (TDSFs) from different solvents and temperatures were characterized. It was found that the caking properties of TDSFs were better than that of fat raw coal. The TDSFs obtained from non-polar solvents have a higher caking property than those obtained from polar solvents at the same thermal dissolution (TD) temperature. During TD process, polar solvents can thermally dissolve more polyaromatic compounds into TDSF, thus increasing the softening temperature and decreasing the caking property of the TDSF. For the same TD solvent, the TDSFs obtained from higher temperatures have a lower caking property compared to those obtained from lower temperatures because of more aromatic components and oxygen functional groups entering them. Crucible coking determinations were carried out to evaluate the coking property of the TDSFs. The result suggests that when 5% of TDSF and 5% of non-caking sub-bituminous coal were used instead of the same amount of fat coal and gas coal, respectively in the coal blends, the quality of the coke obtained could get to the level of the coke obtained from the standard coal blends (i.e. without TDSF and sub-bituminous coal). Therefore, the use of TDSF in coal blending for coke-making is one of the effective methods for opening the coking coal resources.

•A sub-bituminous coal was thermally dissolved with different solvents.•The liquefaction activities of TDSFs with different TDSY were evaluated.•The liquefaction activity of TDSF with high content of aromatic compounds is lower.•The recycle used catalyst has high hydro-liquefaction activity.•Carbon deposition in the reused catalyst slowly takes place.The thermal dissolution (TD) of a Chinese sub-bituminous coal was carried out with different solvents, and five thermal dissolution soluble fractions (TDSFs) with different thermal dissolution soluble yield (TDSY) were obtained. The catalytic hydro-liquefactions of the five TDSFs suggested that the TDSFs obtained have higher liquefaction activity compared to that of raw coal. There is no relation between the liquefaction activity of TDSF and its TDSY. The TDSF with high content of polycyclic aromatic (PCA) ring systems gives lower liquefaction activity. The reusability of a solid acidic catalyst BF3/SBA-15 used in the hydro-liquefaction of TDSF was measured. The results suggested that the reused catalyst has higher catalytic hydro-liquefaction activity compared to that of fresh catalyst. Carbon deposition in the reused catalyst slowly takes place, and the catalyst used in the catalytic liquefaction of TDSF has a good reusability. The recycled use of catalyst for the liquefaction of TDSF is capable at least 4 times. Therefore, it supplies a new pathway to realize high-efficiency coal liquefaction in economy due to the use of recycled high efficient catalyst in the liquefaction of TDSF.

In order to examine the effect of noncovalent bonds on the extraction yield of Xianfeng lignite (XL), XL is subjected to NMP extraction, acid treatment, and subsequent successive extraction with N-methyl-2-pyrrolididinone (NMP), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([Bmim]BF4) and 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl) at 200 °C. The extraction yields in each solvent and step are investigated, respectively. The residues and extracts obtained in each step are characterized by Fourier transform infrared (FTIR) spectra. The results show that there are only small amount of the thermally induced relaxation of the aggregate structure of XL during NMP extraction. Furthermore acid treatment significantly increases the extraction yield of XL with NMP about 41.4%, which results from the release of ionic cross-links. [Bmim]BF4 and [Bmim]Cl can break the weak and strong hydrogen bands in lignite, respectively. The extraction yield of XL is strongly dependent on noncovalent interactions, such as ionic cross-links and hydrogen bonds.Highlights► Effect of noncovalent bonds on the extraction yield of lignite was investigated. ► Four-step successive sequential extraction of lignite is carried out at 200 °C. ► There are large numbers of ionic forces in lignite. ► Ionic liquids can cleave hydrogen bands in lignite.

A Xianfeng lignite (XL) was dissolved in a series of ionic liquids (ILs) at 200 °C. It was found that the anions of the imidazolium-based ILs are one significant factor to affect the extraction yield of XL and the chemical characteristics of extracts obtained from ILs extraction. The dissolution of ILs to lignite is related to the destructive ability of ILs to hydrogen bonds widely existing in lignite. The analyses of residues by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) indicate that the nature of ILs has a significant effect on the disruption of hydrogen bonds existing in lignite. The effective extraction of lignite results from the fracture of the hydrogen bonding network in lignite during lignite dissolving in ILs. Ionic liquid 1-butyl-3-methyl-imidazolium chloride [Bmim]Cl can dissociate significantly almost all of hydrogen bonds existing in lignite.

The demand for metallurgical coke for blast furnaces is forcing the coke-making industry to look for new sources of coking coals. Noncoking coals are attractive for use in the coke-making coal blends, because they are cheaper and more available. In this study, a Chinese sub-bituminous coal with noncaking property was hydrothermally treated in order to modify its caking and coking properties to be used in coke-making coal blends as much as possible. The caking and coking properties of the hydrothermally treated coals were characterized by solvent extraction, caking index (GRI) measurement, and crucible coking determination. The results show that the solvent extraction yield and GRI of the sub-bituminous coal can be greatly increased by hydrothermal treatment at proper conditions and the removal of oxygen functional groups, especially the hydroxyl group, thus dissociating the aggregated structure of coal is responsible for the modification results. Crucible coking determinations suggest that hydrothermal treatment can greatly increase the coke strength and the particle coke strength after reaction toward CO2 and decrease the coke reactivity when the hydrothermally treated coals were used in the coal blends instead of the raw coal. Therefore, hydrothermal treatment is an effective method to modify the caking and coking properties of the sub-bituminous coal.

Based on thermal extraction (TE) and mild oxidation, a new two-step depolymerization method was presented to investigate the macromolecular structure of Xianfeng lignite (XL). The TE of XL was carried out at 320 °C in 1-methylnaphthalene. The residue was oxidized with 5% H2O2 aqueous solution at 40 °C under normal nitrogen atmosphere for 4 h. Most of organic matter in XL was solubilized by the TE and subsequent oxidation. FTIR analysis reveals that the extract from the TE of XL is rich in aliphatic moieties and carbonyl groups but poor in aromatic rings and hydroxyl groups, whereas the residue is enriched in macromolecular aromatics. The mild oxidation introduced carbonyl groups into the macromolecular matrix of XL. The high yields of malonic acid and succinic acid and without benzene polycarboxlic acids from the residue oxidation suggest that –CH2– and –CH2CH2– are main bridged bonds between aromatic rings and benzene ring should be an important aromatic ring in XL.Highlights► Most of organic matter in XF became soluble fraction by TE and oxidation. ► Main linkages between aromatic rings in XF structure are –CH2– and –CH2CH2–.► Benzene ring should be an important aromatic ring in the macromolecular structure. ► Some aliphatic and carbonyl group-containing species are trapped in the structure. ► The species trapped in the structure can be thermally extracted with 1-MN.

A Chinese sub-bituminous coal, i.e., Shengfu (SF) coal, was hydrothermally treated with and without CaO addition at different temperatures, and the extraction yields and caking indexes (GRI) of the treated coals were measured. The action of CaO during hydrothermal treatment was probed in this study. The results show that hydrothermal treatment can obviously increase the extraction yield and GRI of SF coal, and CaO can further promote this effect of hydrothermal treatment. The removal of oxygen functional groups, especially the hydroxyl group, dissociating the aggregated structure of coal, is responsible for the modifying results. CaO can supply a basic environment for the hydrothermal treatment, which is beneficial for the removal of acidic oxygen functional groups by acid–base interactions and promotes the effect of hydrothermal treatment for SF coal, resulting in additional increases in the extraction yield and GRI.

A series of Ni–W catalysts supported on SBA-15 with different pore sizes were prepared by incipient wetness impregnation method and characterized by N2 adsorption–desorption and X-ray diffraction. The hydrogenation of heavy oil (distillation temperature: 320–340 °C) derived from the direct coal liquefaction process using Shengli coal in the presence of sulfided Ni–W/SBA-15 catalysts with different pore sizes were evaluated at 400 °C and initial H2 pressure of 5.0 MPa. The results showed that the catalyst preparation method and the pore size of the support had a significant influence on the Ni/W crystallite size, hydrodenitrogenation (HDN) and hydrodearomatization (HDA) activities of coal-derived heavy oil. The larger pore could cause the Ni–W/SBA-15 to form larger Ni–W crystallite. The catalysts with largest pore in the range studied displayed highest HDN and HDA activities for upgrading of the coal-derived heavy oil.Highlights► Ni-W/SBA-15 catalysts with different pore sizes were prepared and characterized. ► Hydrogenation of heavy oil from the direct coal liquefaction process was evaluated. ► The catalyst preparation method significantly affects hydrogenation activities.

A Chinese sub-bituminous Shenfu (SF) coal was steam treated under atmospheric pressure and the caking and coking properties of the treated coals were evaluated by caking indexes (GRI) and crucible coking characterizations. The results show that steam treatment can obviously increase the GRI of SF coal. When the steam treated coals were used in the coal blends instead of SF raw coal, the micro-strength index (MSI) and particle coke strength after reaction (PSR) of the coke increased, and particle coke reactivity index (PRI) decreased, which are beneficial for metallurgical coke to increase the gas permeability in blast furnace. The quality of the coke obtained from 8% of 200 °C steam treated SF coal in coal blends gets to that of the coke obtained from the standard coal blends, in which there was no SF coal addition in the coal blends. The removal of oxygen groups, especially hydroxyl group thus favoring the breakage of the coal macromolecules and allowing the treated coal formation of much more amount of hydrocarbons, may be responsible for the modified results. The mechanism of the steam treatment was proposed based on the elemental analysis, thermo gravimetric (TG) and FTIR spectrometer characterizations of the steam treated coal.Highlights► Steam treatment can obviously increase the caking properties of sub-bituminous coal. ► The quality of the coke from the steam treated coal blends is greatly modified. ► The removal of oxygen functional groups is responsible for the modifying results.

The behavior of liquefaction of Shengli (SL) lignite with NaOH–methanol was studied. Based on high content of water in lignite and the economy of the process (amounts of NaOH used), the effects of NaOH concentration, methanol content and water content on the liquefaction behavior of SL lignite were preliminarily investigated. The results show that SL lignite has a good reaction activity, and its conversion and product yield reach 98% and 99% at 300 °C for 1 h respectively, when the ratio of SL lignite, NaOH and methanol is for 1 g:1 g:10 ml. NaOH participates in the reaction. The increase of the amount of NaOH significantly increases the amount of tetrahydrofuran soluble (THFS) fraction. Methanol plays a promotion role in the liquefaction, which makes the product yield increase for about 16–23%. Water content has little effect on the SL lignite conversion, product yield and the product distribution. Solvent-extraction components of liquefaction products of SL lignite with NaOH–methanol are mainly THFS, toluene soluble (TS), hexane soluble (HS) and water soluble fractions (WS). The FTIR analyses of solvent-extraction components show that all of the fractions contain OH group, aromatic structure, carbonyl group and aromatic ether oxygen group.

Upper Freeport (UF) coal was pretreated with various solvents with or without additive tetracyanoethylene (TCNE), and the residues were further extracted and characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) measurements in this study. It was found that pretreatments of UF coal by N-methyl-2-pyrrolidinone (NMP) with TCNE and CS2/NMP mixed solvent (4:1 by volume) gave almost the same extraction yields. However, the two soluble residues RNT and RCN, which were obtained from the extraction of UF coal with NMP + TCNE and the CS2/NMP mixed solvent (4:1 by volume), respectively, demonstrated quite different extraction yields in the CS2/NMP mixed solvent (1:1 by volume). FTIR indicated that a large amount of the −OH groups was extracted by NMP + TCNE solvent extraction. An endothermic peak at 350 °C in the difference DSC thermogram of RNT had been observed as that seen in UF raw coal. However, this endothermic peak at 350 °C in the difference DSC thermogram of RCN disappeared. The results show that the aggregation states of the two residues RNT and RCN are different. RNT with a less aggregated state gave a much higher extraction yield in CS2/NMP mixed solvent (1:1 by volume) than that of RCN. The mechanism of the effect of solvent pretreatments on the aggregation behavior of coal was discussed.

Based on the structural inhomogeneities of coal and intermediate products of coal liquefaction, a new kinetic model was advanced to simulate the Shenhua coal liquefaction catalyzed by SO42=/ZrO2 solid acid catalyst using kinetic lump method. It was found that coal was hydrocracked to preasphaltene, asphaltene, oil and gas directly, and preasphaltene and asphaltene were further hydrocracked into oil and gas products in coal liquefaction. Certain regressive reactions existed in the process. The liquefaction conversions calculated from the model agreed well with the experimental data for Shenhua coal liquefaction catalyzed by SO42=/ZrO2 solid acid at the range of experimental conditions, and the activation energies were 69–136 kJ mol−1. There existed obvious regressive reactions at higher liquefaction temperatures. However, besides the regressive transformation of oil and gas to asphaltene at 450 °C liquefaction, there also existed condensation processes of preasphaltene and asphaltene to coke.

The effects of pre-swelling treatment of Shenhua coal at mild temperatures (less than 160 °C) on its hydro-liquefaction properties were determined in this paper. It was found that with the increase of pre-swelling temperature in tetralin (THN) up to 120 °C, the liquefaction conversions of swollen coals increased. However, when N-methyl-2-pyrrolidinone (NMP) was used as swelling solvent, the liquefaction conversion decreased with the increase of pre-swelling temperature. The liquefied product distributions were very much dependent on the pre-swelling pretreatment conditions, and the mechanism was discussed. Based on the results obtained, a new swelling-liquefaction combining technology (SLCT) was advanced, in which the liquefaction conversion and oil + gas yield were enhanced.

The roles of CS2 in the CS2/NMP mixed solvent to coal extraction and solubilization were investigated in this study. There was little effect of removing of CS2 from the solutions on the solubilities of UF coal extract and pyridine insoluble (PI) of the extract in the NMP/CS2 mixed solvent, suggesting that NMP has high enough solubilities to the UF coal extract and PI. Six Argonne different rank coals were extracted with the CS2/NMP mixed solvent and NMP, respectively. It was found that the extraction yield difference between NMP and CS2/NMP mixed solvent for UF coal is largely deviated from the curve obtained for the other 5 coals, suggesting that the pre-swelling of CS2 in the mixed solvent may be one of important roles for high extraction yield of UF coal in the CS2/NMP mixed solvent. FTIR indicated that there was a strong interaction between CS2 and NMP in the CS2/NMP mixed solvent of 1 : 1 volume ratio, which made the strong absorbance at 2156 cm− 1 in the FTIR spectra, and this interaction may disrupt the dipole based association of NMP thus making the CS2/NMP mixed solvent lower viscosity, to penetrate more quickly into the network structure of coal, resulting in the larger solvent partner (NMP) to enter and break the stronger coal–coal interactions.

The change of solution viscosity with time for one kind of coal solubles PI-1, which was obtained from the pyridine insoluble (PI) fractions of Upper Freeport (UF) coal extracts with carbon disulfide–N-methyl-2-pyrrolidinone (CS2/NMP) mixed solvent (1:1 by volume) by solvent treatment of PI in NMP with additive, tetrabutylammonium acetate (TBAA), was investigated in this study. The fractal dimensions of PI-1 aggregates in solutions were calculated from Pal-Rhodes equation. The results show that the fractal concept can be used to study the aggregation of coal molecules in solution. The aggregation of PI-1 in solution at low temperature is a reaction-limited aggregation (RLA) mechanism, and the fractal dimension of PI-1 aggregates decreases with the increase of temperature, suggesting that the aggregation kinetic process is faster for higher temperature.

The co-pyrolysis and co-liquefaction behaviors of Shenfu coal (SC) and rice straw (RS) were investigated. The synergistic interaction between SC and RS was examined by comparing the pyrolysis and liquefaction performances of each material with those of their mixtures. TG analysis suggests that the pyrolysis temperature of RS is low. Pyrolysis of RS can form free radicals at lower temperatures, which can promote the pyrolysis of coal when it is co-pyrolyzed with SC, resulting in larger weight losses of their mixture compared to the arithmetic mean values from individual pyrolysis of SC and RS. Co-liquefaction results indicate that there exists an obvious synergistic effect between SC and RS, which is depend on liquefaction conditions. At high liquefaction temperatures and for long reaction time, the synergistic effect decreases because of the increased pyrolysis rate and lack of hydrogen donating ability, resulting in the increased retrogressive condensation reactions. The largest synergistic effect of SC and RS is obtained at 400°C and 60 min with 50% blending of RS. The liquefaction conversion, 14.8%, and hexane soluble fraction, 9.7%, of the co-liquefaction at this optimal condition are higher than the corresponding arithmetic mean values from the individual liquefaction of SC and RS, respectively.

The depolymerization behaviors of Xianfeng lignite (XL) in ionic liquid 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate ([Bmim]OTf) was studied in this paper. Also, the thermal extracts and residues obtained from thermal depolymerization of XL at different extraction conditions were analyzed. It was found that [Bmim]OTf had good performance in the depolymerization of XL when the extraction was carried out at 280°C for 4 h with [Bmim]OTf/XL at 3.5. The extraction yield of XL with [Bmim]OTf defined as tetrahydrofuran solubles (THFS) reached to 20.1%. The depolymerization of XL with [Bmim]OTf was promoted markedly with the addition of tetralin (THN), H2 and ZnCl2 catalyst, and the yield of THFS reached to 30.0%, 36.9% and 46.8%, respectively. The results showed that the amount of hydrogen bonds in thermal extracts increased significantly with the addition of THN. The contents of aromatics and aliphatic hydrocarbon were enhanced greatly under the existence of H2 and ZnCl2.

With nickel nitrate and nickel acetate as nickel precursors, a series of Ni/SBA-15 catalysts were prepared by using the impregnation method and activating in air or hydrogen atmosphere. The Ni/SBA-15 catalysts were characterized with XRD, H2-TPD, N2 physisorption and online mass spectroscopy. Their catalytic properties were evaluated with hydrogenation of naphthalene as a model reaction. It was shown that activation in hydrogen greatly increased the Ni dispersion and catalytic activity of Ni/SBA-15 prepared with nickel nitrate, while activation in air significantly improved the sample prepared with nickel acetate. In terms of the thermal decomposition products of the catalyst precursors activated in different atmospheres, the affecting mechanism of the activation atmosphere on the Ni/SBA-15 catalysts prepared with different nickel precursors was proposed.

The liquefaction properties and mechanism of Xiaolongtan (XLT) lignite were studied. On the basis of high content of water in lignite, the liquefaction behavior of XLT lignite under different atmospheres using water as solvent was preliminarily probed. The results show that XLT lignite has a good liquefaction activity, and its liquefaction conversion gets to 94.5% at 420°C, H2 atmosphere, and tetralin (THN) used as solvent. During coal liquefaction, the active H stabilizing free radicals formed during coal pyrolysis is mainly from hydrogen donor solvent. H2 Gas has no hydrogenation activity, and it cannot directly provide active H for coal liquefaction. When water was used as solvent instead of THN in liquefaction of XLT lignite, high liquefaction conversion occurs under CO atmosphere compared to H2 or N2 atmosphere. This suggested that the water gas shift reaction produced active H under CO atmosphere. The active H stabilized the free radicals formed from coal pyrolysis to form lower molecular weight liquefaction products, and therefore, increasing liquefaction conversion. Because of the low primary pressure of CO in the experiment, the active H formed from the water gas shift reaction is limited. Thus, the liquefaction conversion of XLT lignite is not high when water is used as solvent. But our preliminary study shows that it is new lignite liquefaction technology using water as solvent under CO atmosphere and has remarkable market value and utilization prospects.

The co-thermal dissolution (CTD) properties of Shenfu coal (SC) and rice straw (RS) in 1-methylnaphthalene (1-MN) at different temperatures were studied. It is found that RS gives much higher of thermal dissolution yield (TDY), suggesting its high thermal dissolution (TD) activity. But much amount of gas is produced in the TD process of RS, resulting in the low thermal soluble yield (TSY). For the TD of SC, although the TDYs of SC are much lower than those of RS, but the differences between TDY and TSY from the TD of SC are much smaller than those from the TD of RS. CTD of SC and RS shows that there exists synergistic effect which is the function of temperature. At 320 to 340°C the TSYs have positive synergistic effect. The experimental results are larger than corresponding calculated weighted mean values of the individual TD of SC and RS. While at all the TD temperatures studied, TDYs give negative synergistic effect. The largest enhancements in TSY of 7.9% comparing with corresponding calculated weighted mean values of the individual TD of SC and RS are obtained at 320°C. The mechanism of synergistic effect produced in CTD was discussed based on the characterization of TD soluble fractions.

The liquefaction behaviors of Xianfeng lignite (XL) in ionic liquid 1-butyl-3-methyl-imidazolium tetrafluoroborate ([Bmim]BF4) under mild condition −350°C were studied. The effect of catalysts (FeS, ZnCl2, AlCl3 and FeCl3) on the XL liquefaction in [Bmim]BF4 were investigated and the liquefaction products obtained were analyzed by FT-IR spectra. It is found that the XL has a good hyrogenation activity in the presence of [Bmim]BF4, catalysts and tetralin (THN). XL liquefied product yield reaches to about 66.2% and the main liquefaction product is heavy fraction-tetrahydrofuran soluble (THFS) and tetrahydrofuran insoluble/N-methyl-2-pyrrolididinone soluble fractions (NS). The analyses of liquefied product by FT-IR show that the type of catalyst significantly affects the distribution and structure of liquefied product.

The activities of nickel supported on SBA-15 catalysts, which were prepared by pretreatment with ammonia/water vapour, were investigated by hydrogenation of naphthalene. Comparing with the un-pretreated catalysts, the pretreated catalysts exhibited significant activity, and naphthalene conversion was improved approximately 100% over the un-pretreated catalysts. The formation of NH4NO3 during pretreatment, which helped to reduce NO2/O2 generation thus enhancing the dispersion of NiO, was considered to be the main reason for the increased Ni0 dispersion and the enhanced activity of the catalyst pretreated with ammonia/water vapour.Ni/SBA-15 catalysts prepared by pretreatment with ammonia/water vapour have much higher naphthalene conversions than those of the catalysts without pretreatment (Figure below), indicating that the catalytic activity of Ni/SBA-15 catalyst can be strongly enhanced by ammonia/water vapour pretreatment.Download full-size imageResearch Highlights►The hydrogenation activity of nickel supported on SBA-15 catalysts, which are prepared by pretreatment with ammonia/water vapour, is improved approximated 100%. ►The formation of NH4NO3 during pretreatment, which helped to reduce NO2/O2 generation thus enhancing the dispersion of NiO, was considered to be the main reason for the increased Ni0 dispersion and the enhanced activity of the catalyst pretreated with ammonia/water vapour. ►Pretreatment with ammonia/water vapour is a novel and interesting method to prepare other supported catalysts.