Pd catalysts supported on rGO-TiO2 composites for direct synthesis of H2O2: Modification of Pd2 +/Pd0 ratio and hydrophilic property

The use of nanostructured composites as catalyst supports is a promising route to prepare catalysts with high selectivity and productivity. In this work, reduced graphene oxide-TiO_2(rGP-x) composites with a variation of reduced graphene oxide(rGO) content were synthesized by hydrothermal method. Pd/rGP-x catalysts were prepared in incipient-wetness impregnation method for the direct synthesis of H_2O_2 from H2 and O_2. The morphology and electronic properties of catalysts were investigated by XPS, TEM, and Raman spectroscopy.The ratio of Pd~(2+)/Pd~0 and the hydrophobicity of the catalysts were increased with the rising content of rGO. As the amount of rGO in the catalysts varied in the range of 0.025 wt%–2 wt%, the selectivity of H_2O_2 exhibited a tendency of increasing firstly and then decreasing from 0.1 wt% to 2 wt%. It indicates that good catalytic performance for H_2O_2 synthesis can be achieved only when appropriate amount of rGO is introduced. The H_2O_2 selectivity and productivity of Pd/r GP-0.025 both improved remarkably compared with Pd/P25. This enhancement originated from the combined effects of the proper ratio of Pd~(2+)/Pd~0 and hydrophobicity of the catalyst.     

Controllable synthesis of polyoxymethylene dimethyl ethers by ionic liquids encapsulated in mesoporous SBA-16

The promising combustion and emission properties of polyoxymethylene dimethyl ethers(PODE_n) are of significant interest. However, the synthesis of PODE_n products with desired chain lengths is still a problem facing synthetic PODE_n. Herein, a series of unique IL@SBA-16-Cx solid catalysts are prepared by encapsulation of ionic liquids(ILs) within the nanocage of SBA-16 through a silylation method. The structure of the encapsulated catalyst was characterized by UV–vis spectra, Fourier transform infrared(FT-IR),N_2 adsorption–desorption isotherms, Powder X-ray diffraction(XRD), Transmission electron microscopy(TEM) and Elemental analysis. The encapsulated catalysts show similar catalytic activity to the homogeneous counterparts and display higher selectivity to the targeted PODE_(3–5) products than their homogeneous counterparts in the synthesis of PODE_n from methanol(MeOH) and trioxymethylene(TOM). The encapsulated catalysts exhibit a superior PODE_(3–5) selectivity and could be the promising catalysts for PODE_n synthetic reaction.     

液相合成甲醇催化剂活性的研究

The effects of reduction procedure, reaction temperature and composition of feed gas on the activity of a CuO-ZnO-Al2O3 catalyst for liquid phase methanol synthesis were studied. An optimized procedure different from conventional ones was developed to obtain higher activity and better stability of the catalyst. Both CO and CO2 in the feed gas were found to be necessary to maintain the activity of catalyst in the synthesis process. Reaction temperature was limited up to 523K, otherwise the catalyst will be deactivated rapidly. Experimental results show that the catalyst deactivation is caused by sintering and fouling, and the effects of CO and CO2 on the catalyst activity are also investigated. The experimental results indicate that the formation of water in the methanol synthesis is negligible when the feed gas contains both CO and CO2. The mechanism for liquid-phase methanol synthesis was discussed and it differed slightly from that for gas-phase synthesis.     

非均相催化一步合成碳酸二苯酯及溶胶凝胶法制备催化剂载体合成条件的优化

The support of catalyst for the direct synthesis of diphenyl carbonate （DPC） by heterogeneous catalytic reaction was prepared by the sol-gel method. Compared with activated charcoal, molecular sieve, porous ceramics, hopcalite, the support prepared by the sol-gel method has higher activity. The characterization of the support by X-ray diffraction （XRD） and transmission electron microscope （TEM） show that the mare crystal phase is Co2MnO4 and the average particle diameter is about 40 nm. The optimum conditions for synthesis of the support were determined by orthogonal experiments, which indicate that the proportion of Cu, Mn, and Co is the first important factor influencing the yield and selectivity of DPC. Temperature of calcination is the second one. The optimum conditions are： molar proportion of Cu, Mn, and Co being 1 ： 1 ： 1, temperature of calcination 700℃, drying at 100~C, temperature of water bath 85~C. The yield and selectivity of DPC in the process can reach 38% and 99% in the batch operation, respectively. The copper cobalt manganese mixed oxides chosen as the support contribute more to the high catalytic activity than the sol-gel method.     

钌基氨合成催化剂氢氮吸附性能的研究

The effects of promoters K, Ba, Sm on the chemisorption and desorption of hydrogen and nitrogen, dispersion of metallic Ru and catalytic activity of active carbon (AC) supported ruthenium catalyst for ammonia synthesis have been studied by means of pulse chromatography, temperature-programmed desorption, and activity test. Promoters K, Ba and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly, and particularly, potassium exhibited the best promotion on the activity because of the strong electronic donation to metallic Ru. Much higher activity can be obtained for Ru/AC catalyst with binary or triple promoters. The activity of Ru/AC catalyst is dependent on the adsorption of hydrogen and nitrogen. The high activity of catalyst could be ascribed to strong dissociation of nitrogen on the catalyst surface. Strong adsorption of hydrogen would inhibit the adsorption of nitrogen, resulted in decrease of the catalytic activity. Ru/AC catalyst promoted by Sm2O3 shows the best dispers     

抑制碳负载钌基氨合成催化剂甲烷化的研究

The effects of promoters K, Ba, Sm on the resistance to carbon-methanation and catalytic activity of ruthenium supported on active carbon (Ru/AC) for ammonia synthesis have been studied by means of TG-DTG (thermalgravity-differential thermalgravity), temperature-programmed desorption, and activity test. Promoters Ba,K, and Sm increased the activity of Ru/AC catalysts for ammonia synthesis significantly. Much higher activity can be reached for Ru/AC catalyst with bi- or tri-promoters. Indeed, the triply promoted catalyst showed the highest activity, coupled to a surprisingly high resistance to methanation. The ability of resistance of promoter to methanation of Ru/AC catalyst is dependent on the adsorption intensity of hydrogen. The strong adsorption of hydrogen would enhance methanation and impact the adsorption of nitrogen, which results in the decrease of catalytic activity.     

固体超强酸催化剂SO2-4/TiO2-MoO3的制备及其催化合成缩醛（酮）

SO4^2-/TiO2-MoO3, a novel solid superacid, has been prepared and its catalytic activity at different synthetic conditions was examined with esterification of n-butanoic acid and n-butyl alcohol as probing reaction.The optimum conditions were also found, that is, the mass ratio of MoO3 used in the compound is 25%, the calcination temperature 450℃, and the soaked consistency of H2SO4 is 0.5mol.L^-1. Then it was applied in the catalytic synthesis of six similar important ketals and acetals as catalyst and revealed high catalytic activity. Under the condition that the molar ratio of aldehyde/ketone to glycol was 1:1.5, the mass ratio of the catalyst to the reactants was 0.5% and the reaction time 1.0 h, the yield of ketals and acetals reached up to 63.2%. The catalyst can be easily recovered and reused.     

The cooperation effect of Ni and Pt in the hydrogenation of acetic acid

The catalytic hydrogenation of carboxylic acid to alcohols is one of the important strategies for the conversion of biomass.Herein,a series of Ni-doped PtSn catalysts were prepared,characterized and studied in the hydrogenation of acetic acid.The Ni dopant has a strong interaction with Pt,which promotes the hydrogen adsorption,providing an activated hydrogen-rich environment for the hydrogenation.Meanwhile,the presence of Ni also improves the Pt dispersion,giving more accessible active sites for hydrogen activation.The cooperation of Pt and Ni significantly promotes the catalytic activity of the hydrogenation of acetic acid to ethanol.As a result,the catalyst with 0.1%Ni exhibits the best reaction activity,and its space time yield is twice as that of the PtSn/SiO2 catalyst.It provides a meaningful instruction on the catalyst design for the carboxylic acid hydrogenation.     

Application of kinetics and computational fluid dynamics in pinene isomerization

A reliable kinetic model to describe the effects of various factors on the reaction rate and selectivity of pinene isomerization is developed. Furthermore, computational fluid dynamics(CFD) is applied to simulate the solid–liquid dispersion in reactor. The catalyst Ti M is obtained by improving the composition and structure of hydrated titanium dioxide. The kinetic equation of pinene isomerization is deduced based on reaction mechanism and catalyst deactivation model. The kinetic equation of pinene isomerization reaction is fitted, and the results show that the fitted equation is correlated with the experimental data. The rate and selectivity of pinene isomerization reaction are affected by the amount of catalyst, deactivation of catalyst, structure of catalyst, reaction temperature and water content of catalyst. The solid–liquid distribution of the reactor is calculated by computational fluid dynamics numerical simulation, and the solid–liquid dispersion in commercial scale reactor is more uniform than that in lab-scale reactor.     

甲苯与叔丁醇在补铝HM沸石催化剂上的烷基化反应

The realuminated H-mordenite catalysts (HM1-4) treated with different concentrations of NaOH and NaAlO2 aqueous solutions were prepared, and characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and temperature-programmed desorption of ammonia, They are of lower Si/Al ratio and higher acid amount while keeping a high relative crystallinity. Their catalytic performances were evaluated with the liquid-phase tert-butylation of toluene with tert-butyl alcohol in a 100 ml stainless steel batch reactor equipped with a stirrer. HM2 zeolite catalyst, obtained by treating HM in 0.1 mol•L－1 NaOH followed by 0.05 mol•L－1 NaAlO2 aqueous solution, shows a higher catalytic activity because of its highest acid amount. For HM2 catalyst the influences of reaction conditions on catalytic performance were investigated. The conversion of toluene is 50.3% and the selectivity of p-tert-butyltoluene is 74.7% at a temperature of 180°C, 2 of molar ratio of tert-butyl alcohol to toluene, 4h of reaction time and 0.2 of M(catalyst)/M(toluene).     

双组分Cu催化硅和氯甲烷直接合成甲基氯硅烷简

A bi-component catalyst comprising CuC1 and metallic copper was used in the direct synthesis of me- thylchlorosilane to study the catalytic synergy between the different copper sources. The catalyst exhibited high ac- tivity and high selectivity of dimethyldichlorosilane （M2） in the stirred bed reactor. The effect of the proportion of CuC1 used was studied and 10%-30% CuC1 gave the best yield of M2. The use of CuC1 decreased the induction pe- riod of reaction, improved the selectivity in the induction stage, and gave a longer stable stage. These results sug- gest that bi-comoonent catalyst has advantazes in the direct synthesis reaction.     

Synthesis and characterization of BZSM-5 and its catalytic performance in the methanol to hydrocarbons reaction

Five kinds of BZSM-5 molecular sieve with different Si/B ratio and a SiZSM-5 molecular sieve were prepared by hydrothermal synthesis method followed by acid exchange and pelletization.The samples were characterized by XRD,SEM,FT-IR,ICP,low temperature N_2 physical adsorption and desorption,NH3-TPD and Py-IR.The catalytic performance in the reaction of methanol to hydrocarbons was evaluated in the fixed bed reactor.Compared with SiZSM-5,the amount and strength of Bronsted(B) acid were enhanced by introducing skeleton boron and the activity of the catalyst was greatly improved.The characterization and evaluation results indicated that the BZSM-5 catalyst synthesized from the gel of SiO_2/B_2 O_3 20 with Si/B ratio 74.48 had modest acidity strength,acid amount of 0.18 mmol NH_3·g~(-1) and large mesopore volume of 0.23 cm~3·g~(-1).The B acid ratio was higher and the acid strength of BZSM-5 was weaker than that of AIZSM-5,which could inhibit the deep coke formation and increase the activity stability.B-2 had the best lifetime which could reach 672 h under the same evaluation reaction conditions,due to the best matching of moderate acidity and good diffusion properties.     

非均相催化一步合成碳酸二苯酯的研究（VI）Sn 的添加量对Pd-Sn催化性能的影响

The compound metal oxide LaxPbyMnzO used as support was prepared by the sol-gel method, and the catalyst in which Pd was used as active component and Sn as co-active component for direct synthesis of diphenyl carbonate (DPC) with heterogeneous catalytic reaction was obtained by co-calcination and precipitation respectively.The catalyst was characterized by XRD, SEM and TEM respectively. The specific surface area of catalysts was measured by ChemBET3000 instrument, and the activity of the catalysts was tested by the synthesis of DPC in a pressured reactor. The results showed that when the co-active component Sn was added by co-calcination method A, its loading content was equal to 14.43% and active component Pd was loaded by precipitation, the yield and selectivity of DPC could reach 26.78% and 99% respectively.     

非均相羰基氧化一步合成碳酸二苯酯的研究(Ⅴ)筛选催化剂及优化合成条件

Pd/LaxPbyMnOz, Pd/C, Pd/molecular sieve and Pd-heteropoly acid catalysts for direct synthesis of diphenyl carbonate (DPC) by heterogeneous catalytic reaction were compared and the results of DPC synthesis indicated that the catalyst Pd/LaxPbyMnOz had higher activity. The Pd/LaxPbyMnOz catalyst and the support was characterized by XRD, SEM and TEM, the main phase was Lao.szPbo.asMnOa and the average diameter could be about 25.4nm. The optimuna conditions for synthesis of DPC with Pd/LasPbyMnOz were determined by orthogonal experiments and the experimental results showed that reaction temperature was the first factor of effect on the selectivity and yield of DPC, and the concentration of O2 in gas phase also had significant effect on selectivity of DPC. The optimum reaction conditions were catalyst/phenol mass ratio l to 50, pressure 4.5MPa, volume concentration of O2 25%, reaction temperature 60℃ and reaction time 4 h. The maximum yield and average selectivity could reach 13% and 97% respectively in the     

晶格氧用于轻烃的选择氧化

In this paper, selective oxidation of n-butane to maleic anhydride (MA) and partial oxidation of methane to synthesis gas with lattice oxygen instead of molecular oxygen are investigated. For the oxidation of butane to MA in the absence of molecular oxygen, the Ce-Fe promoted VPO catalyst has more available lattice oxygen and provides higher conversion and selectivity than that of the unpromoted one. It is supposed that the introduction of Ce-Fe complex oxides improves redox performance of VPO catalyst and increases the activity of lattice oxygen.For partial oxidation of methane to synthesis gas over LaFeO3 and Lao.8Sro.gFeO3 oxides, the reaction with flow switched between 11% O2-Ar and 11% CH4-He at 900℃ was carried out. The results show that methane can be oxidized to CO and H2 with selectivity over 93% by the lattice oxygen of the catalyst in an appropriate reaction condition, while the lost lattice oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of the LaFeO3 and La0.8Sr0.2FeO3 catalyst instead of molecular oxygen to react with methane to synthesis gas in the redox mode.     

Cobalt catalysts for Fischer–Tropsch synthesis: The effect of support,precipitant and pH value

In this report,Co-based catalysts supported on ZnO,Al_2O_3 and ZrO_2 as well as the ZrO_2 derived from different precipitants and different pH values were prepared by co-precipitation method.Their catalytic Fischer–Tropsch synthesis(FTS)performance was investigated in a fixed-bed reactor.The results revealed that Co catalyst supported on ZrO_2 exhibited better FTS catalytic performance than that supported on ZnO or Al_2O_3.For the Co/ZrO_2catalyst,different precipitants showed the following an activity order of NaOHNa_2CO_3NH_4OH,and the best pH value is 13.The catalysts were characterized by N_2adsorption–desorption,XRF,XRD,H_2-TPR,H_2-TPD and TEM.It was found that the main factor affecting the CO conversion of the catalyst was the amounts of low-temperature active adsorption sites.Moreover,the selectivity of C_5~+hydrocarbons had a positive relationship with the peak temperature of the weak hydrogen adsorption sites.The higher the peak temperature,the higher the C_5~+selectivity is.     

非均相催化一步合成碳酸二苯酯的研究(VI)Sn的添加方法及添加量对Pd-Sn催化性能的影响

The compound metal oxide Lax Pby Mnz O used as support was prepared by the sol-gel method, and the catalyst in which Pd was used as active component and Sn as co-active component for direct synthesis of diphenyl carbonate (DPC) with heterogeneous catalytic reaction was obtained by co-calcination and precipitation respectively. The catalyst was characterized by XRD, SEM and TEM respectively. The specific surface area of catalysts was measured by ChemBET3000 instrument, and the activity of the catalysts was tested by the synthesis of DPC in a pressured reactor. The results showed that when the co-active component Sn was added by co-calcination method A, its loading content was equal to 14.43% and active component Pd was loaded by precipitation, the yield and selectivity of DPC could reach 26.78% and 99% respectively.     

One-step synthesis of Ni@Pd/NH2-Fe3O4 nanoparticles as affordable catalyst for formic acid dehydrogenation

Currently, one of the critical issues in the world is finding an appropriate green alternative to fossil fuels due to the concerns about global warming. As a hydrogen source, formic acid has been given particular attention owing to the attractive features such as high-energy density, no toxicity, high stability at ambient temperature and high hydrogen content. Introducing an affordable and highly efficient catalyst with easy recovery from the reaction mixture for selective dehydrogenation of formic acid is still demanding.In this report, we used a simple one-step process to synthesize Ni@Pd core shell nanoparticles on 3-aminopropyltriethoxysilane modified Fe_3O_4 nanoparticles. The existence of Ni and Pd results in a synergic effect on the catalytic activity. The —NH_2 groups play an important role for obtaining well-dispersed ultrafine particles with high surface area and active sites. In addition, Fe_3O_4 lead to convenient magnetic recovery of the catalyst from reaction mixture. Our results indicate that the as-prepared catalyst give the superb turnover frequency of 5367.8 h~(-1) with no additive, which is higher than most of the previously reported catalysts.     

Cs交换Y沸石超笼中的磷钼杂多酸的制备、表征和催化性能

In order to solve the serious leaching problem of supported heteropoly acid catalysts in polar reaction media,12-molybdophosphoric acid encapsulated in the supercage of Cs⁺-exchanged Y zeolite was prepared by the "ship in the bottle" synthesis.The influence of ion-exchange conditions and the synthesis parameters on the encapsulation of PMo₁₂ were investigated.The obtained solid sample was characterized by X-ray diffraction(XRD),³¹P magic angle spin nuclear magnetic resonance(MAS NMR) and Fourier Transform Infrared Spectroscopy(FT-IR),and its catalytic activity in the esterification of acetic acid and n-butanol was tested.The ion-exchange time,concentration of aqueous Cs⁺ solution,pH value,and amount of Mo added in the synthesis mixture were revealed to influence the encapsulation very remarkably.Under the optimal conditions,12-molybdophosphoric acid could be successfully encapsulated in the supercage of CsY zeolite,and the samples showed considerable catalytic activity and excellent reusability in the esterification reaction.     

滴流床中乙醛液相氧化合成过氧乙酸新工艺

In this paper,shorter residence time（a few minutes）with high yield in the trickle bed process for per- acetic acid synthesis by acetaldehyde liquid phase oxidation can be realized on the selected packing material SA-5118.For acetaldehyde in acetone with ferric ion as catalyst,the optimized process conditions were presented. The main factors influencing the yield,selectivity and conversion are residence time,temperature and acetaldehyde concentration,respectively.The temperature range checked is from 30 to 65℃.High yield of 81.53%with high se- lectivity of 91.84?n be obtained at higher temperature of 55℃when the residence time is 5.5min and the acet- aldehyde concentration is 9.85%（by mass）.And there is a critical acetaldehyde concentration point（Cccp）between 18%and 19.5%（by mass）.At temperature less than 55℃,the highest yield to peracetic acid at each temperature level increases with temperature when the acetaldehyde concentration is below Cccp and decreases with temperature when the acetaldehyde concentration is above Cccp.