钙基催化吸收剂对玉米秸秆热解气化制氢特性的影响

在一个2段式生物质热解气化装置上考察了钙基催化吸收剂对玉米秸秆制氢特性的影响,结果表明：CaO添加可原位吸收气化过程中生成的CO_2,强化制氢过程向生成更多H_2的方向移动。当热解气化温度为650℃、S/B为2、CaO/C摩尔比为1时,产气中H_2体积分数从28.7%上升至56.2%,H_2产率则从64.3 m L/g上升至195.8 m L/g,而CO_2体积分数由21.5%下降至1.1%。而且,CaO的CO_2吸收强化性能与气化温度密切相关,在600~700℃范围内,玉米秸秆热解气化可获得很高的H2体积分数和较高的H2产率。以CaO吸收剂为载体进一步引入Ni O活性组分,可降低产气中小分子碳氢气体,提高产气中的H2体积分数和产率。在NiO负载量为10%时,产气中H2体积分数可达63.7%,而H_2产率对比添加CaO时则接近翻倍,达到了341.3 m L/g。

Spectra analysis and O_2 evolution for TiO_2 photocatalyst compounded with indirect transition semiconductors

The photo absorbing, photo transmitting and photoluminescence performances of WiO2 photocatalysts compounded with V2O5 or WO3 were investigated by UV-Vis spectra, transmitting spectra, and PL spectra, respectively. The energy band structures of TiO2 photocatalysts were analyzed. The photocatalytic activities of the TiO2 photocatalysts were investigated by splitting of water for 02 evolution. The results indicate that the band gaps of WO3 and V205 are about 2.8 and 2.14 eV, respectively, and the band gap of rutile TiO2 is about 3.08 eV. Speeds of water splitting for 2%WO3-TiO2 and 8%V2O5-TiO2 photocatalysts are 420 and 110 μmol/（L.h）, respectively, under UV light irradiation. V2O5 and WO3 compounded with suitable concentration can improve the photocatalytic activity of TiO2 with Fe3＋ as electron acceptor.

Isolation of Pd atoms by Cu for semi-hydrogenation of acetylene: Effects of Cu loading

Cu‐alloyed Pd single‐atom catalysts exhibit excellent catalytic performance for the semi‐hydrogenation of acetylene;however,the limit of the Cu/Pd atomic ratio for forming the alloyed Pd single‐atom catalyst is ambiguous.Herein,silica‐supported Cu-Pd bimetallic catalysts with fixed Pd content and varied Cu loadings were synthesized using an incipient wetness co‐impregnation method.The X‐ray absorption spectroscopy results indicated that Pd formed an alloy with Cu after reduction at250°C and that the Pd atoms were completely isolated by Cu for Cu/Pd atomic ratios≥40/1.Notably,increasing the reduction temperature from250to400°C hardly affected the catalytic performances of the Cu-Pd/SiO2catalysts.This finding can be attributed to the similar chemical environments of Pd demonstrated by the X‐ray absorption spectroscopy results.

Conversion of Biomass to Hydrocarbon-rich Bio-oil via Microwave-assisted Catalytic Pyrolysis： A Review

The method for pyrolysis of biomass to manufacture hydrocarbon-rich fuel remains challenging in terms of conversion of multifunctional biomass with high oxygen content and low thermal stability into a high-quality compound, featuring high content of hydrocarbons, low oxygen content, few functional groups, and high thermal stability. This study offers a promising prospect to derive hydrocarbon-rich oil through microwave-assisted fast catalytic pyrolysis by improving the effective hydrogen to carbon ratio(H/Ceff) of the raw materials. The proposed technique can promote the production of high-quality bio-oil through the molecular sieve catalyzed reduction of oxygenated compounds and mutagenic polyaromatic hydrocarbons. This work aims to review and summarize the research progress on microwave copyrolysis and microwave catalytic copyrolysis to demonstrate their benefits on enhancement of bio-oils derived from the biomass. This review focuses on the potential of optimizing the H/Ceff ratio, the microwave absorbent, and the HZSM-5 catalyst during the microwave copyrolysis to produce the valuable liquid fuel. This paper also proposes future directions for the use of this technique to obtain high yields of bio-oils.

Effect of Mn Promoter on Structure and Performance of K-Co-Mo Catalyst for Synthesis of Higher Alcohols from CO Hydrogenation

A series of Mn-doped K-Co-Mo catalysts were prepared by a sol-gel method. The catalyst structure was well characterized by X-ray diffraction, N2 physisorption, NH3 temperature- programmed adsorption, in situ diffuse reflectance infrared Fourier transform spectroscopy, and X-ray absorption fine structure spectroscopy. The catalytic performance for higher alcohol synthesis from syngas was measured. It was found that the Mn-doped catalysts ex- hibited a much higher activity as compared to the unpromoted catalyst, and in particular the C2＋ alcohol selectivity increased significantly. The distribution of alcohol products de- viated from the Anderson-Schulz-Flory law. The portion of methanol in total alcohol was suppressed remarkably and the ethanol became the predominant product. Characterization results indicated that the incorporation of Mn enhanced the interaction of Co and Mo and thus led to the formation of Co-Mo-O species, which was regarded as the active site for the alcohol synthesis. Secondly, the presence of Mn reduced the amount of strong acid sites significantly and meanwhile promoted the formation of weak acid sites, which had a positive effect on the synthesis of alcohol. Furthermore, it was found that the incorporation of Mn can enhance the adsorption of linear- and bridge-type CO significantly, which contributed to the formation of alcohol and growth of carbon chain and thus increased the selectivity to C2＋OH.

Near-infrared absorbing 2D/3D ZnIn2S4/N-doped graphene photocatalyst for highly efficient CO2 capture and photocatalytic reduction

Hierarchical heterostructure photocatalysts with broad spectrum solar light utilization,particularly in the nearinfrared(NIR)region,are emerging classes of advanced photocatalytic materials for solar-driven CO2 conversion into value-added chemical feedstocks.Herein,a novel two-demensional/three-demensional(2 D/3 D)hierarchical composite is hydrothermally synthesized by assembling vertically-aligned ZnIn2 S4(ZIS)nanowall arrays on nitrogen-doped graphene foams(NGF).The prepared ZIS/NGF composite shows enhancement in photothermal conversion ability and selective CO2 capture as well as solar-driven CO2 photoreduction.At273 K and 1 atm,the ZIS/NGF composite with 1.0 wt%NGF achieves a comparably high CO2-to-N2 selectivity of 30.1,with an isosteric heat of CO2 adsorption of 48.2 kJ mol^-1.And in the absence of cocatalysts and sacrificial agents,the ZIS/NGF composite with cyclability converts CO2 into CH4,CO and CH3 OH under simulated solar light illumination,with the respective evolution rates about 9.1,3.5,and 5.9 times higher than that of the pristine ZIS.In-depth analysis using in-situ irradiated X-ray photoelectron spectroscopy(ISI-XPS)in conjunction with Kelvin probe measurements reveals the underlying charge transfer pathway and process from ZIS to NGF.

Boosted charge transfer and photocatalytic CO_(2) reduction over sulfurdoped C_(3)N_(4) porous nanosheets with embedded SnS_(2)-SnO_(2) nanojunctions

Two-dimensional porous nanosheet heterostructure materials,which combine the advantages of both architecture and components,are expected to feature a significant photocatalytic performance toward CO_(2) conversion into useful fuels.Herein,we provide a facile strategy for fabricating sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions(S-C_(3)N_(4)/SnO_(2)-SnS_(2))via liquid impregnation-pyrolysis and subsequent sulfidation treatment using a layered supramolecular structure as the precursor of C_(3)N_(4).A hexagonal layered supramolecular structure was first prepared as the precursor of C_(3)N_(4).Then Sn^(4+) ions were intercalated into the supramolecular interlayers through the liquid impregnation method.The subsequent annealing treatment in air simultaneously realized the fabrication and efficient exfoliation of layered C_(3)N_(4) porous nanosheets.Moreover,SnO_(2) nanoparticles were formed and embedded in situ in the porous C_(3)N_(4) nanosheets.In the following sulfidation process under a nitrogen atmosphere,sulfur powder can react with SnO_(2) nanoparticles to form SnO_(2)-SnS_(2) nanojunctions.As expected,the exfoliation of sulfur-doped C_(3)N_(4) porous nanosheets and ternary heterostructure construction could be simultaneously achieved in this work.Sulfur-doped C_(3)N_(4) porous nanosheets with embedded SnO_(2)-SnS_(2) nanojunctions featured abundant active sites,enhanced visible light absorption,and efficient interfacial charge transfer.As expected,the optimized S-C_(3)N_(4)/SnO_(2)-SnS_(2) achieved a much higher gas-phase photocatalytic CO_(2) reduction performance with high yields of CO(21.68μmol g^(−1)h^(−1))and CH_(4)(22.09μmol g^(−1)h^(−1))compared with the control C_(3)N_(4),C_(3)N_(4)/SnO_(2),and S-C_(3)N_(4)/SnS_(2) photocatalysts.The selectivity of CH_(4) reached 80.30%.Such a promising synthetic strategy can be expected to inspire the design of other robust C_(3)N_(4)-based porous nanosheet heterostructures for a broad range of applications.

Nitrogen-doped graphene supported Pd@PdO core- shell clusters for C-C coupling reactions

The introduction of nitrogen significantly decreases the metal particle size and improves the performance of metal-based graphene-supported catalysts. In this work, the density functional theory is used to understand the interaction between nitrogen-doped graphene and Pd@PdO clusters. Experiments show that small size Pd@PdO clusters （1-2 nm） can be grown uniformly on nitrogen-doped graphene sheets by a facile oxidation-reduction method. The nanoscale interaction relationship between nitrogen-doped graphene and Pd@PdO clusters is investigated through X-ray photoelectron spectroscopy （XPS） and X-ray absorption spectra （XAS）. The composite catalysts are applied in Suzuki-Miyaura reactions giving high yields and good structural stability. These results have potential impact in design and optimization of future high performance catalyst materials for cross coupling reactions.

Bonding interface boosts the intrinsic activity and durability of NiSe@Fe_(2)O_(3) heterogeneous electrocatalyst for water oxidation

The intrinsic activity and durability of oxygen evolution reaction(OER)electrocatalysts are mainly dominated by the surface and interface properties of active materials.Herein,a core-shell heterogeneous structure(NF/NiSe@Fe_(2)O_(3))is fabricated via two-step hydrothermal method,which exhibits a low overpotential of 220 mV(or 282 mV)at 10 mA/cm^(2)(or 200 mA/cm^(2)),a small Tafel slope of 36.9 mV/dec,and long-term stability(-230 h)in 1 mol/L KOH for OER.X-ray photoelectron spectroscopy and X-ray absorption spectroscopy reveal the(oxy)hydroxide-rich surface and strong coupling interface between NiSe and Fe_(2)O_(3)via the Fe-Se bond.Density functional theory calculation suggests that the d-band center and electronic state of NiSe@Fe_(2)O_(3)heterojunction are well optimized due to the formation of Fe-Se bond,which is favorable for the enhanced OER activity because of the easy adsorption of oxygen-containing intermediates and desorption of O^(2)in the OER process.In addition,the unique core-shell structure and robust bonding interface are responsible for the good stability for OER.This work provides fundamental insights on the bonding effect that determine the performance of OER electrocatalyst.

Low Temperature Growth of SWNTs on a Nickel Catalyst by Thermal Chemical Vapor Deposition

Single-walled carbon nanotubes （SWNTs） have been grown on a silica-supported monometallic nickel （Ni） catalyst at temperatures ranging from as low as 450℃to 800℃. Different spectroscopic techniques, such as Raman, photoluminescence emission （PLE）, and ultra violet-visible-near infrared （UV-vis-NIR） absorption spectroscopy were used to evaluate file diameter and quality of the SWNTs grown over the Ni catalyst at different temperatures. The analysis revealed that high quality SWNTs with a very narrow diameter distribution were obtained at a growth temperature of 500 ℃. In the PLE and absorption spectra, differences were observed between the SWNTs grown oil Ni and those grown on cobalt （Co）. This result expands the potential of growing a specific （n, m） tube species with relatively high abundance by tuning the catalyst composition. Furthermore, the prerequisites for the low temperature growth of SWNTs over a monometallic transition metal catalyst have been elucidated.

Controllable CO adsorption determines ethylene and methane productions from CO_(2) electroreduction

Among all CO2 electroreduction products,methane(CH4)and ethylene(C_(2)H_(4))are two typical and valuable hydrocarbon products which are formed in two different pathways:hydrogenation and dimerization reactions of the same CO intermediate.Theoretical studies show that the adsorption configurations of CO intermediate determine the reaction pathways towards CH4/C_(2)H_(4).However,it is challenging to experimentally control the CO adsorption configurations at the catalyst surface,and thus the hydrocarbon selectivity is still limited.Herein,we seek to synthesize two well-defined copper nanocatalysts with controllable surface structures.The two model catalysts exhibit a high hydrocarbon selectivity toward either CH4(83%)or C_(2)H_(4)(93%)under identical reduction conditions.Scanning transmission electron microscopy and X-ray absorption spectroscopy characterizations reveal the low-coordination Cu^(0)sites and local Cu^(0)/Cu^(+)sites of the two catalysts,respectively.CO-temperature programed desorption,in-situ attenuated total reflection Fourier transform infrared spectroscopy and density functional theory studies unveil that the bridge-adsorbed CO(CO_(B))on the low-coordination Cu^(0)sites is apt to be hydrogenated to CH4,whereas the bridge-adsorbed CO plus linear-adsorbed CO(CO_(B)+CO_(L))on the local Cu^(0)/Cu^(+)sites are apt to be coupled to C_(2)H_(4).Our findings pave a new way to design catalysts with controllable CO adsorption configurations for high hydrocarbon product selectivity.