Abstract: Catalytic hydrogenation of CO2 is considered to be one of the most practical ways to produce value-added chemicals and fuels. However, due to the extreme chemical inertness, the high C–C coupling barrier and the many competing reactions, it is of vital important to develop the efficient catalysts for achieving the activation and transformation of CO2 into a variety of chemical products. In recent years, indium oxide has aroused great interest in CO2 hydrogenation due to its abundant oxygen vacancies, high selectivity of methanol and high activity of CO2 conversion. In this paper, the structure of In2O3 and the catalytic performance of In2O3-supported or metal-doped composite catalysts for CO2 hydrogenation to methanol are reviewed. The effects of the proximity of In2O3 to different zeolites and the migration of elements on the products of CO2 hydrogenation to hydrocarbons are also discussed. Finally, the challenges and development directions of selective hydrogenation of CO2 over In2O3-based catalysts are summarized.
Abstract: Nitrogen oxides (NOx) from diesel engine exhaust is one of the main sources of environmental pollution. Zeolite-based NH3-SCR catalysts have extensively investigated and have shown great promise for the efficient reduction of NOx because of their excellent NH3-SCR performance, robust hydrothermal stability and outstanding N2 selectivity. However, with the increasingly stringent environmental regulations and the implementation of the requirement of “zero emission” of diesel engine exhaust, it is particularly important to develop zeolite-based catalysts with more excellent catalytic activity and anti-poisoning performance, especially core-shell structure catalyst. In this review, we mainly focus on the recent research progress of the core-shell structure zeolite-based catalysts for NH3-SCR reactions with three commonly used Beta, ZSM-5, and SSZ-13 zeolite as the cores, the reaction mechanism of resistance to hydrothermal aging, sulfur poisoning, hydrocarbon poisoning, and alkali metal poisoning, as well as the future development and application prospects of zeolite-based core-shell structure catalysts.
Abstract: The slow and fast co-pyrolysis characteristics of cellulose and oxalic acid were investigated by thermogravimetric-Fourier transform infrared spectroscopy and horizontal fixed-bed pyrolysis setup. The weight loss curve of slow co-pyrolysis showed oxalic acid decomposition and cellulose decomposition stages. As the decomposition of oxalic acid and cellulose was not synchronous, oxalic acid affected the decomposition of cellulose mainly through the volatiles formed by its decomposition, which was not obvious. Differently, in fast co-pyrolysis, oxalic acid and cellulose were simultaneously pyrolyzed, and sufficient interaction could occur between raw materials and volatile components. Therefore, oxalic acid had a significant impact on the pyrolysis products of cellulose. Compared with the fast pyrolysis of cellulose, the contents of levoglucosan and levoglucosenone decreased, while the content of 1,4∶3,6-dianhydro-α-D-glucopyranose increased significantly in the bio-oil during fast co-pyrolysis process. The volume fraction of CO in pyrolysis gas decreased, whereas that of CO2 increased. In addition, the decomposition of cellulose was more thorough, and more aromatic structures were formed in biochar.
Abstract: This work investigated the conversion characteristics of iron-based oxygen carrier (70%Fe2O3/30% Al2O3) with TMCs in a two-stage fixed-bed reactor using tar model compounds (TMCs) of biomass/coal, and evaluated the reactivity of different TMCs and the factors affecting their conversion. It was found that the reaction degree of TMCs with oxygen carrier was phenol>anthracene>naphthalene, and the conversion of phenol to carbon deposition was the highest (64%), while the conversion of naphthalene to carbon deposition was the lowest (40%); the degree of reaction between oxygen carriers and naphthalene was relatively high, but easily led to the sintering of oxygen carrier. Besides, activity characterization of the carbon deposition showed that the carbon deposition generated from naphthalene had the highest stability among the three TMCs. Increasing the amount of oxygen carrier and reaction temperature was beneficial to the further conversion of naphthalene and anthracene, and could also increase the fraction of CO2 in gaseous products. The high reaction activity and strong cracking effect of phenol led to a small change in the conversion rate with increasing the amount of oxygen carrier and reaction temperature. However, high reaction temperature (1000 ℃) could lead to severe cracking of the tar to generate a large amount of carbon deposition. The results of the cycle experiment showed that the oxygen carrier reacting with naphthalene was most severely deactivated.
Abstract: The Cu/SiO2 catalysts were prepared by co-precipitation and tested for hydrogenation of furfural to furfuryl alcohol in a fixed bed reactor. The deactivation mechanism of the catalysts was investigated by characterization of H2-TPR, ICP-OES, XPS, TG, Raman and TEM. Under the conditions of atmospheric pressure, reaction temperature of 140 ℃, mass space velocity of 2.4 h−1 and the molar ratio of hydrogen to furfural of 9.7, the furfural conversion was higher than 97% in the first 5 h. However, the conversion of furfural decreased rapidly from 96% to 32% after 21 h of reaction, indicating that Cu/SiO2 catalyst was rapidly deactivated. The factors for the deactivation of Cu/SiO2 catalyst were the agglomeration and sintering of the active component copper. Moreover, the carbon deposition on the catalyst surface resulted in the covered active site Cu0.
Abstract: Mesoporous carbon supported Ni-Mo hydrodesulfurization (HDS) catalysts have been successfully prepared with Anderson polyoxometalate (NH4)4[NiMo6O24 H6]·5H2O, thiourea, citric acid, and sodium chloride to evaluate the HDS performance with dibenzothiophene. The catalysts were prepared by one-step vacuum freeze-drying, followed by calcination under nitrogen and washing off the template, and then structurally characterized via many devices, including XRD, Raman, low temperature N2 adsorption-desorption isotherm, SEM, HRTEM, XPS, and TPR. The results show these catalysts possess weaker metal-support interaction, shorter MoS2 particles (4.9 nm) and appropriate stacking number (4.8), and higher percent of NiMoS active phase. The dibenzothiophene conversion, overall pseudo-first order rate constant and the turnover frequency can reach 94.1%, 1.7 × 10–6 mol/(g·s) and 2.8 × 10–3 s–1, respectively. By using in-situ formed NaCl and H2S as hard template and sulfidizing agent respectively, this methodology opens a new avenue for the simple and environmental friendly fabrication of HDS catalysts via the synchronization and riveting of mesoporous carbon support and MoS2 particles.
Abstract: Different morphologies of CeO2 supports (including CeO2-R rod, CeO2-C cube, and CeO2-P polyhedron) were synthesized by hydrothermal method and were used to develop Ni3Fe/CeO2 catalysts by impregnation method for dry reforming of methane (DRM). The structures of the resultant catalysts before and after DRM were characterized by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetry analysis. The results showed that Ni3Fe/CeO2-R exhibited good catalytic activity in DRM, where CH4 as well as CO2 conversion reached to 82% and 91%, respectively, at 800 ℃, owing to its large specific surface area and high oxygen vacancy concentration. The catalytic performance of Ni3Fe/CeO2-R was relatively stable and graphitic degree of coke deposition was low after 10 h. Meanwhile, the oxidative resistance of Ni3Fe/CeO2-R was improved as confirmed by the existence of stable Ni3Fe alloy after reaction, which mitigated the facile oxidation of more oxyphilic Fe species on the alloy by the promotion of CO2 activation on the vacancies of CeO2-R.
Abstract: H2S and CO2, two harmful acid waste gases, often co-exist in important chemical production such as coal-chemical industry, natural gas chemical industry and petrochemical industry, causing corrosion of industrial equipment and pipelines, and must be treated innocuously. Co-conversion of H2S-CO2 mixed acid gas to syngas has been carried out using dielectric barrier discharge (DBD) plasma-catalysis, which renders the highly corrosive and toxic H2S and greenhouse gas CO2 harmless, and produces syngas. The effects of various parameters of the DBD plasma on the reaction of one-step conversion of H2S-CO2 to syngas were studied. Moreover, a comparative study of the different parameters of DBD plasma was carried out. The intrinsic correlation between the reaction performance of syngas production via H2S-CO2 conversion and these parameters, including specific energy input (SEI), discharge shape, discharge frequency, discharge gap and discharge length, was investigated and revealed. On this basis, a multi-tube parallel DBD plasma reaction system was designed and constructed.
Abstract: Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO2 and a series of Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH3-TPD, CO2-TPD, etc. It was found that the addition of MOx weakened the Pt-CeO2 interaction and promoted the generation of Ptδ + species with lower valence state, which contribute to the C−H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH4 selectivities were obtained over the Pt-MgO/CeO2, while the highest CH4 selectivity was obtained over the Pt-CrOx/CeO2 (2.21%). Over the Pt/CeO2 and Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts, CO2/CH4 ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H2O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.
Abstract: A combination of impregnation and physical mixing methods was used to modulate the sites of the metal active center Pt, which were individually settled onto ZSM-22 molecular sieves or cerium oxide carriers, resulting in Pt-ZSM-22/CeO2 catalysts with atomic-level contacts at the spacing of the metal-acid bicenter sites and Pt-CeO2/ZSM-22 catalysts that maintained nanoscale spacing, respectively. The physical and chemical properties of the two catalysts were characterized by means of spherical differential electron microscopy, XRD, BET, H2-TPR and XPS, and their n-heptane isomerization reaction performance was investigated. In addition, the changes of the physicochemical properties and reaction performance of Pt-CeO2/ZSM-22 catalysts at different reduction temperatures were investigated. The results showed that the metal-acid center maintained nanoscale spacing Pt-CeO2/ZSM-22 catalyst had higher n-heptane isomerization activity and isomeric hydrocarbon yield, which could be attributed to the atomic-level dispersion of Pt on the CeO2 carrier. During the reduction of Pt-CeO2/ZSM-22 catalyst, the release of more oxygen vacancies from the CeO2 carrier helps to retard the aggregation of metal Pt and facilitates the adsorption of heptane molecules. When the reduction pretreatment temperature was 300 ℃, the heptane conversion and heptane isomerization hydrocarbon yield were 79.2% and 75.4%, respectively, and the isomerization selectivity reached 95.2%.
Abstract: The oxidation of styrene to benzaldehyde has advantages of mild conditions and no chlorine impurities in the product, and the design of highly active catalyst is the core. As a solid acid catalyst, WO3 has excellent performance in thermal oxidation reaction, but its activity is limited by small specific surface area and high B acid content. In this work, the Cr3 + cation was introduced as a modifier during the preparation of WO3. The adsorption of Cr3 + cations on non-(001) crystal plane realized the transformation of WO3 from nanorods to ultrafine nanowires (UNWs), and the specific surface area of obtained Cr-WO3 UNWs increased to 297 m2/g. In addition, Cr3 + cation could dope into the lattice of WO3 and slow down its crystallization, both of which effectively enriched the surface oxygen vacancies (L acid sites) of WO3. In the reaction of selective oxidation of styrene to benzaldehyde, Cr-WO3 UNWs effectively increased the conversion of styrene and the selectivity of benzaldehyde from 19.0% and 49.6% of pure WO3 nanorod to 72.0% and 84.6% respectively under the optimized condition of 70 ℃, r(nH2O2/nstyrene)=2.0, 6 h and m=30 mg. The improvement of catalytic performance can be attributed to the following two reasons:(1) the large specific surface area can provide sufficient active site for reaction; (2) the L acid site can activate H2O2 into active W-OOH, and an increase in the concentration of L acid site is beneficial for the production of more active species.
Abstract: The photocatalysis of direct dehydrogenation of benzyl alcohol to benzaldehyde is an energy saving way to synthesize fine chemicals and pure hydrogen by using solar energy. The CdS-based catalysts were one of the typical kinds of photocatalysts for this reaction. The morphology of CdS could be easily tuned, which could greatly influence the photocatalytic performances. However, the morphology effect of CdS on the photocatalytic behaviour of the direct dehydrogenation of benzyl alcohol has not been investigated yet. In this work, we synthesized CdS with two different morphologies (nanosheet (NS) and nanowire (NW)) and found the CdS-NS showed much higher photocatalytic activity for converting the benzyl alcohol than the CdS-NW, but the selectivity to benzaldehyde over the two supports was very low. By depositing Au25 nanoclusters on the CdS-NW and CdS-NS, the morphology effect of the CdS support could be mitigated and their catalytic activity and selectivity could be greatly boosted for the photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde and H2. The results of this work would provide new insight into the design of efficient photocatalysts for synthesizing fine chemicals.
Abstract: It is a great challenge for the selective hydrogenation of phenylacetylene to styrene over non-noble metal catalyst under mild reaction conditions. Carbon-modified TiO2 supported nickel nanoparticles catalyst was prepared using impregnation-reduction method, which exhibited excellent photocatalytic performance in selective hydrogenation of phenylacetylene under visible light irradiation. The photo-excited hot electrons over Ni nanoparticles promoted the activation of reactants. The electron-rich Ni nanoparticles inhibited the adsorption of phenylethylene on the surface of Ni/TiO2, which increased the selectivity of phenylethylene. This work provides an environmentally-benign and efficient method for photocatalytic hydrogenation of phenylacetylene.
Abstract: The selective catalytic reduction (SCR) NH3 catalyst is mainly used in industrial production and automobile exhaust cleaning. In this study, a novel α%Fe2O3/ZrTiO4 (α=0, 8, 12, 15) catalyst was prepared by the coprecipitation impregnation method. The results show that the NOx conversion rate of 12%Fe2O3/ZrTiO4 catalyst with the optimal composition is high above 80% at 250−400 °C, close to 100% at 300 °C, and N2 selectivity is high above 90% at 200−450 °C. The redox properties, surface acidity, and Oβ/(Oα + Oβ) ratio of ZrTiO4 catalysts are improved after loading Fe2O3 on the ZrTiO4 surface, which is attributed not only to the porous structure of α%Fe2O3/ZrTiO4 catalyst but also to the synergistic interaction between the active component Fe2O3 and the support ZrTiO4. In addition, in-situ DRIFT reactions show that the NH3-SCR reaction of 12%Fe2O3/ZrTiO4 catalyst follows the Eley-Rideal mechanism. A clear reaction mechanism is conducive to a deeper understanding of the reaction process of NOx conversion during SCR. This work provides a feasible strategy for Fe-based SCR catalysts to replace V-based catalysts in the medium temperature range in the future.
Abstract: In this study, CuMn2O4/MO2 (M=Mn, Ti, Ce) catalysts with different support loads were prepared by sol-gel spontaneous combustion at low temperature, and the removal performance of toluene and NOx was evaluated. The results showed that the addition of CeO2 carrier could significantly alleviate the mutual inhibition of toluene oxidation and NH3-SCR over CuMn2O4. Therefore, CuMn2O4/CeO2 catalyst showed the best removal efficiency of toluene and NOx simultaneously. The physicochemical properties of the catalyst and the reaction mechanism of CuMn2O4 were analyzed by BET, XRD, NH3-TPD, O2-TPD and combined XPS and in-situ DRIFTs. The results showed that the introduction of CeO2 increased the proportion of Mn4 + /Mnn + in the catalyst, and promoted the formation of rich acid sites and oxygen vacancies on the surface of CuMn2O4/CeO2 catalyst. In addition, the strong interaction between Cu, Mn and Ce accelerated electron transfer and enhance the redox cycle for Cu + + Ce4 + ↔Cu2 + + Ce3 + 、Mn4 + + Ce3 + ↔Mn3 + + Ce4 + . It has been confirmed by in-situ DRIFTs that NH3-SCR reaction on CuMn2O4 catalyst follows Langmuir-Hinshelwood mechanism and oxidation of toluene follows Mars-van Krevelen mechanism. Therefore, CuMn2O4/CeO2 catalyst with CeO2 as the support has excellent reoxidation ability to promote the complete oxidation of toluene, so it shows excellent removal ability of toluene and NOx simultaneously. This work can provide guidance for the development of catalysts for simultaneous removal of toluene and NOx.
Abstract: A series of Mn/CeO2 catalysts modified with different Fe contents were prepared by impregnation method and tested for their low-temperature performance for simultaneous de-nitrification and toluene removal. It was found that the Fe5Mn/CeO2 catalyst showed the best catalytic performance and the conversion efficiency of toluene reached 90% at 175 ℃ and NO conversion reached 90% at 95−300 ℃. The physical and chemical properties of the catalysts were characterized by BET, SEM, XRD, XPS, H2-TPR, NH3-TPD and O2-TPD. XPS results showed that the increased content of Ce3+ and Mn4+ in the Fe5Mn/CeO2 catalyst promoted the formation of oxygen vacancies and unsaturated chemical bonds, providing more active sites, thus facilitating the efficient removal of NO and toluene at low temperatures. Compared with other catalysts, H2-TPR, NH3-TPD and O2-TPD indicate that Fe5Mn/CeO2 catalyst has great redox ability, stronger acidity and better oxygen migration ability. In addition, this paper explores the effects between selective catalytic reduction (NH3-SCR) and catalytic oxidation reaction of toluene over Fe5Mn/CeO2 catalyst. NH3 preferentially reacts with the active site on the catalyst to inhibit the toluene oxidation process, while NO promotes the toluene removal process. Toluene can promote the NH3-SCR process in a certain temperature range. While NO promotes the formation of NO2, NO2 effectively promotes the combination of toluene and active sites, which is conducive to the catalytic oxidation of toluene; The inhibition of toluene on the NH3-SCR process weakens with the increase of temperature. At 100 ℃, the inhibition of toluene on the NH3-SCR process disappears. When the temperature exceeds 225 ℃, toluene reacts with NO as a reducing agent and promotes the formation of NO2, thus promoting the NH3-SCR reaction.
Abstract: To develop adsorbents suitable for the storage of natural gas by adsorption, activated carbon SAC-02, HKUST-1 and MIL-101(Cr) were synthesized and characterized in terms of structural morphology observation, nitrogen physisorption at 77.15 K, and methane adsorption at 293.15–313.15 K and 0–4 MPa. The methane adsorption isotherms were comparatively correlated with the Toth, D-A and Ono-Kondo equations and the performances of the adsorbent samples were evaluated in terms of the isosteric adsorption heat and the adsorbed phase density. The results indicate that in comparison with the D-A and Ono-Kondo equations, the Toth equation displays much smaller relative errors in correlating the methane adsorption data and is then more suitable for the adsorption equilibrium analysis on the adsorbed natural gas (ANG) system. MIL-101(Cr) exhibits the largest mean isosteric heat for methane adsorption and the density of the adsorbed methane phase is smaller than that of the liquid methane but increases with the equilibrium pressure; overall, MIL-101(Cr) with highest adsorption capacity is more suitable for methane adsorption than activated carbon and HKUST-1.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
