Abstract: The Ni-W/SBA-15 catalysts prepared by incipient-wetness impregnation method and controlled by the pH value were developed. Potassium hydroxide and citric acid regarded as the pH value regulators were added to the solution before impregnation to provide an acidic or basic condition at different pH values (0.83, 1.00, 3.09, 5.00, 7.03, 8.97 and 11.0). The 74.5% yield of total low carbon (C2, 3) polyols including ethylene glycol (EG), 1, 2-propylene glycol (1, 2-PG) and glycerol (Gly) was obtained over 10%Ni-20%W/SBA-15 catalyst prepared at pH value of 1.00 and 518 K under H2 pressure of 5.0 MPa. Furthermore, the physical properties of this series of nickel-tungsten catalysts were characterized by BET and SEM. The results demonstrated that the catalysts showed excellent thermal stability and the surface area was mainly in range of 330-450 m2/g. The particles had a good dispersion on the surface of SBA-15 but some aggregations were existed which could be characterized by TEM and SEM-EDX. However, the reduction of metallic oxides especially for NiO was obviously influenced by pH value control and some metallic species characterized by XRD. According to XRD results, the impregnation pH value influenced the reduction of NiO and the phase states of nickel and tungsten species.
Abstract: Dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) is one of the pivotal reactions in conversion of biomass towards valuable platform compounds. In this work, Nb/SBA-15 was prepared via incipient wetness impregnation with self-made SBA-15 as support; Nb/SBA-15 was further treated with phosphoric acid and calcined at 450℃, to obtain the Nb-P/SBA-15 catalyst. The Nb-P/SBA-15 catalyst was characterized by SEM, TEM, BET, XRD and NH3-TPD; its performance in the dehydration of fructose to 5-HMF was then investigated. The results indicate that the microscopic structure of SBA-15 is well preserved in Nb/SBA-15 with an internal channel diameter of about 10 nm and the niobic species are highly dispersed on the surface of the channels; the wall of channels became thinner after impregnation of Nb and treatment with phosphoric acid. After the treatment with phosphoric acid, the weak acid sites are increased, moreover, the medium and strong acidic sites are generated in Nb-P/SBA-15; as a result, for the dehydration of fructose in a water/MIBK biphasic system, Nb-P/SBA-15 exhibits higher catalytic activity and selectivity to 5-HMF. By reaction at 160℃ for 1.5 h, with a water/MIBK volume ratio of 1/2, the conversion of fructose and the yield of 5-HMF reach 96.1% and 92.6%, respectively. Moreover, the Nb-P/SBA-15 catalyst also exhibits excellent stability in view of water tolerance; it still demonstrates high catalytic activity and selectivity to 5-HMF even after successive recycling for four times.
Abstract: The direct liquefaction of cornstalk cellulose in sub-supercritical methanol using an autoclave was investigated under reaction temperature range of 240-320℃, methanol dosage range of 0-200 mL and reaction time range of 0-200 min. The effects of various liquefaction parameters on the yields of bio-oil and dominant components (alkanes, esters, acids and alcohols, etc.) obtained from cornstalk cellulose liquefaction were investigated combining with GC/MS. The results show that the cellulose is transformed to alkanes, esters and alcohols, and the increasing of reaction temperature and methanol dosage can result in an increase in the yields of water soluble organic matter, heavy oil and various chemicals. The yield of bio-oil reaches to 25.1% under the optimum operating conditions:methanol dosage is 160 mL; reaction temperature is 320℃; reaction time is 30 min. The relative contents of dominant components in bio-oil are in the order:alkanes > alcohols > esters > acids, with the highest relative contents of 77.2%, 19.0%, 30.9%, 20.8%, respectively. The reaction temperature and methanol dosage have an obvious influence on the distribution and yields of dominant chemicals. As the reaction temperature and methanol dosage further increases, the concentration and activity of free radical will increase, and the components of alcohols and esters can be oxidized and condensed to transform into acids and so on when the reaction temperature and methanol usage are more than 160 mL and 300℃, respectively, leading to a decline in the yields of chemicals and bio-oil.
Abstract: A series of alumina-promoted sulfated zirconia catalysts were prepared by precipitation-impregnation method. The catalysts were characterized by N2 sorption, pyridine adsorption Fourier transform infrared spectroscopy (Py-FTIR), X-ray diffraction (XRD). Their catalytic performance in n-butane isomerization was evaluated in a continuous flow type fixed-bed micro-reactor at atmospheric pressure, 200℃, and H2:C4=2:3, with a weight hourly space velocity of n-butane (WHSV) of 3 h-1. The structure-reactivity relationship between surface acidity and catalytic behavior was revealed. Py-FTIR indicates that the sulfated treatment enhances the strength and density of catalytic Brønsted acid sites, which are essential for n-butane isomerization. Therefore, sulfated treatment can significantly improve the activity of n-butane isomerization, and Lewis acidity has no direct effect on it.
Abstract: The MCM-41/MOR composite molecular sieves with multiple micro-mesoporous structure were hydrothermally synthesized by using the alkali-treated MOR seriflux as partial silica-alumina source and cetyltrimethylammonium bromide(CTAB) as the template in self-assembly process. The synthesized samples of molecular sieves were characterized by XRD, HRTEM, BET and Py-FTIR, respectively. The results showed that the samples exhibit a hierarchical micro-mesoporous structure, large specific surface area and good hydrothermal stability as well. The isomerization performance of the composite zeolite catalyst was evaluated in a fixed bed microreactor. The results showed that the appropriate B and L acid coordinated with each other to act as the active center of alkane isomerization, while Ni species were not only active site for this reaction, but also played a good role in the modification of acidity. Compared with Ni-MOR, Ni-MCM-41 and HMCM-41/MOR, the Ni-MCM-41/MOR catalyst had better catalytic performance for isomerization reaction, the conversion of n-hexane is 34.40%, and the selectivity of i-C60 is 40.38%.
Abstract: Cobalt-based catalysts supported on ordered mesoporous carbon (Co/OMC) were modified with Mn and Zr promoters by the co-impregnation method. The cobalt-based catalysts were characterized by XRD, N2 sorption, H2-TPR, H2/CO-TPD and XPS; the promoting effects of Mn and Zr on the catalytic performance of Co/OMC in Fischer-Tropsch synthesis (FTS) were investigated in a fixed-bed reactor. The results indicate that the addition of either Mn or Zr can greatly reduce the selectivity to CH4 for FTS over Co/OMC. Moreover, Mn as a promoter can enhance the selectivity to C2-4 hydrocarbons and the olefin/paraffin ratio, whereas Zr promotes the dispersion of cobalt species and increases the number of active Co sites, leading to a significant increase in the FTS activity and selectivity to C5+ hydrocarbons.
Abstract: The effects of H2O on the performance of the sulfur-resistant Mo-based methanation catalysts were investigated by adding vapor into the reactant gas at the reaction conditions of 550℃, 5 500 h-1, 1.2% of H2S concentration. The results indicate that water caused irreversible deactivation of Mo-based catalyst supported on Al2O3, while additive Co and cerium-aluminum composite carrier can enhance the activity and improve the stability of the Mo-based catalyst for methanation of syngas. The promoter Co protects the active phase MoS2 of Mo-based catalyst, inhibits the irreversible deactivation caused by the addition of water. When the water content in reactant gas is increased, the water gas shift reaction increases and becomes the main reaction on catalysts, and the increase of water leads to further decrease of the catalyst activity and stability.
Abstract: In this work, a flower-like CeTiOx composite oxide, predominantly exposing CeO2{100} plane, was synthesized by a simple hydrothermal method. The SEM and XRD results revealed the growth mechanism of CeTiOx composite oxide can be divided into two stages, including the rapid growth of amorphous and the following crystallization. The ratio of Ce/Ti, KOH concentration, crystallization time and calcination temperature are the key factors for the synthesis of the flower-like CeTiOx composite oxide. Au catalyst supported on this composite oxide exhibited superior activity for CO oxidation at room temperature. The TEM and H2-TPR results suggested that the exposed CeO2{100} plane and the strong interaction between Au and CeTiOx composite oxide are responsible for the high activity.
Abstract: A series of ceria oxide catalysts doped with Fe, Ni and Cu were prepared by hydrothermal method and they characterized by N2 sorption, XRD, H2-TPR, Raman spectra and XPS; the relationship between the structure of Ce-M mixed oxides and their catalytic performance in low temperature CO oxidation were then investigated. The results reveal that the incorporation of Fe, Ni and Cu metal ions into CeO2 can remarkably increase the amount of oxygen vacancies in the doped samples, which is beneficial to the migration of the lattice oxygen; as a result, the doped Ce-M mixed oxides exhibit much higher reducibility and catalytic activity than the pure CeO2. Among them, the CeCu catalyst with most oxygen vacancies exhibits the highest activity in CO oxidation, with a complete CO conversion at 130℃; over CeNi catalyst, in the next, a complete CO conversion is obtained at 180℃. On the contrary, CeFe catalyst is least active and the conversion of CO is only 92% at 200℃.
Abstract: A Pt/HZSM-5 catalyst was prepared by atomic layer deposition (ALD) for aqueous-phase hydrogenation of levulinic acid (LA) to valeric acid (VA). 5Pt/HZSM-5 produced with 5 cycles of Pt ALD was identified as a highly active and stable bifunctional catalyst, and a high yield of VA (91.4%) was achieved in aqueous solution. A close interaction between Pt and acid sites of HZSM-5 is favor for the selective generation of VA. The microporous structure and the acid sites of HZSM-5 were not changed after Pt ALD, and some Pt nanoparticles were located in the micropore channel of HZSM-5. This reveals that the Pt ALD has the advantage to protect the structure of zeolite. The average particle size of Pt nanoparticles, electric state of surface Pt, and surface acid sites are nearly not changed with the increase of Pt ALD cycle number. However, the ratio of Pt in the pore channel to that out of the pore decreases with the increase of ALD cycle numbers, resulting in a decrease of TOF of VA yield. For comparison, Pt nanoparticles supported on HZSM-5 were also produced by impregnation. But the pore structure of HZSM-5 was damaged, and more micropore were formed by impregnation method for Pt loading. Moreover, it exhibited very low catalytic activity, selectivity of VA, and stability.
Abstract: A series of Ce-La/MgAl2O4-x catalysts were prepared by the incipient wetness impregnation method and characterized by BET, XRD, H2-TPR, CO-TPR and in situ FT-IR. The results demonstrate that the catalyst with a Mg/Al molar ratio of 0.5 yields the most uniform dispersion of CeO2 and greatly enhances formation of Ce-O-La solid solution, resulting in the increase of oxygen vacancy and surface Ce3+ content. Thereby, the synergistic effect between surface Ce3+ and oxygen vacancy gives rise to the best catalytic performance of NO reduction. Moreover, introduction of Mg species suppresses tranformation of CeO2 to Ce(SO4)2/Ce2(SO4)3 and then improves the SO2 resistance performance of Ce-La/MgAl2O4-0.5.
Abstract: A series of Mn-Ce-Co-Ox/PPS composite filter materials with different mass ratios were obtained by modifying the pristine polyphenylene sulfide (PPS) filter material with sodium dodecyl sulfate (SDS) and then treated by a redox precipitation method. The Mn-Ce-Co-Ox/PPS composite filter materials were characterized by XRD, FESEM, TEM and XPS; their catalytic performance in the low-temperature selective catalytic reduction (SCR) of NOx was then investigated. The results show that the Mn-Ce-Co-Ox/PPS composite filter materials obtained by the redox method presents higher low-temperature SCR activity than the Mn-Ce-Co-Ox/PPS-UM composite filter material fabricated via the ultrasonic method; over the former material, the NOx conversion reaches 86%-100% at 120-160℃. Among them, the 1.2Mn-Ce-Co-Ox/PPS composite filter material displays the highest SCR activity, which is probably ascribed to the high Ce3+/(Ce3++Ce4+) ratio and high concentration of Co; moreover, honeycomb-like MnO2, Ce2O3, CeO2, CoO and Co3O4 are uniformly distributed on the PPS filter material in the weak crystalline structure. In comparison with Mn-Ce-Co-Ox/PPS-UM, the 1.2Mn-Ce-Co-Ox/PPS composite filter material also exhibits higher resistance to H2O and SO2.
Abstract: Sb-V2O5-TiO2 catalysts were prepared by wet impregnation method. The effect of antimony loadings and calcination temperatures on the activity of catalysts were investigated on the basis of 3%V2O5-TiO2. The results indicate that the catalyst with 11% Sb loading, calcined at 500℃, has the best activity of SCR. The NOx conversion could reach 92% at 170℃ with the inlet NOx concentration of 0.07%, the O2 volume fraction of 5%, and the space velocity of 27 000 h-1. The H2-TPR data reveal that the increase of activity can be attributed to the promotion of the catalyst oxidation ability by the modifying of antimony. Sb is mainly in the pentavalent antimony form on the surface of the catalyst, and the increase in surface acidity of the catalyst is identified by means of XPS and NH3-TPD. The effects of SO2 and H2O on the catalyst is also studied, showing that the Sb-V2O5-TiO2 has an excellent catalytic activity in the presence of H2O and SO2. FT-IR, TG and pore structure test results suggest that the addition of Sb can effectively inhibit the aggregation of ammonium sulfate on the catalyst surface, thereby improving the service life of the catalyst.
Abstract: The selective reduction of NO in an oxygen-rich environment with biomass-derived activated carbon supported potassium catalyst was investigated. The. results show that in comparison with coal (lignite) based activated carbon supported potassium catalyst, biomass (sawdust) based activated carbon supported potassium catalyst exhibits a high selectivity for the reduction of NOx to N2, keeping a high and stable activity with NO reduction of about 80% during 2 h-isothermal experiment as well as a relatively low activity with the oxygen-carbon reaction of 18%. XRD, BET, XPS and TPD results indicate that the excellent catalytic performance of the biomass-derived activated carbon supported potassium catalyst is associated with the highly dispersion of active potassium species, which might result from the high surface area and the large amount of surface oxygen groups. Furthermore, the selective emission of CO2 with regard to CO is an additional benefit of using biomass-derived activated carbon as the support for NO reduction.
Abstract: Given the easy reduction of Hg2+ in wet desulfurization slurry in a power plant, migration mechanism of Hg2+ in a simulated system was studied. Influences of several experimental parameters including slurry temperature, pH value and concentrations of SO32-, Cl-, Ca2+ and Mg2+ were investigated separately. The results indicate that the increase of SO32- concentration lowers the reduction rate of Hg2+, while the rise of slurry temperature leads to an opposite result. The effect of pH value shows a trend of first increase and then decrease, and reaches the highest reduction rate at pH value of 5.5. Moreover, the rise of Ca2+, Mg2+ and Cl- concentrations could inhibit the reduction of Hg2+.
Abstract: The influence of the gasification temperature(650, 750 and 850℃)and sludge types on the yield and chemical compositions of tar produced by the air gasification of sewage sludge in a fluidized bed gasifier was studied by GC-MS analysis. The results show that the yields of tar decrease with gasification temperature increasing, and the yields of tar from anaerobic digestion sludge gasification are lower than that from indigested sludge gasification. The chemical compositions of tar can be divided into five categories:aliphatic compounds, alicyclic compounds, aromatic hydrocarbons, aromatic hydrocarbon derivatives and heterocyclic compounds. When the gasification temperature increases, the yields of aliphatic and alicyclic compounds in the tar from the gasification of indigestion sludge produced by Anaerobic-Anoxic-Oxic (A2/O) process decrease; the yields of aromatic hydrocarbon derivatives in the tar increase; and the yields of aromatic hydrocarbons and heterocyclic compounds firstly increase and then decrease. At 650℃, the yields of all the organic compounds in the tar from the gasification of digestion sludge produced by activated sludge process are lower than that from the indigestion sludge gasification; the yields of aromatic hydrocarbons in the tar from the gasification of the digestion sludge produced by A2/O process are higher than that from the indigestion sludge gasification; and the yields of the other organic compounds are lower than that for the indigestion sludge gasification.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
