Morphology and crystal-plane effects of Zr-doped CeO2 nanocrystals on the epoxidation of styrene with tert-butylhydroperoxide as the oxidant

The morphology effect of Zr-doped CeOwas studied in terms of their activities in the selective oxidation of styrene to styrene oxide using tert-butyl hydroperoxide as the oxidant. In the present work, Zrdoped CeOnanorods exhibited the highest catalytic performance（yield of styrene oxide and TOF value）followed by nanoparticles and nanocubes. For the Zr-doped CeOnanorods, the apparent activation energy is 56.3 k J/mol, which is much lower than the values of catalysts supported on nanoparticles and nanocubes（73.3 and 93.4 k J/mol）. The high resolution transmission electron microscopy results indicated that（100） and（110） crystal planes are predominantly exposed for Zr-doped CeOnanorods while（100）and（111） for nanocubes,（111） for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeOnanorods is mainly attributed to the higher percentage of Cespecies and more oxygen vacancies, which are associated with their exposed（100） and（110） crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeOnanorods did not lose its initial high catalytic activity after five successive recycles.

Styrene epoxidation with hydrogen peroxide over calcium oxide catalysts prepared from various precursors

A series of CaO samples were prepared by calcination of commercially available and synthesis of calcium salt precursors such as calcium acetate, carbonate, hydroxide and oxalate etc. CaO samples were found to be effective for the epoxidation of styrene using hydrogen peroxide as an oxidant in the presence of acetonitrile. To determine the influence of the physicochemical properties and surface basicity on the catalytic activity, the prepared CaO samples were characterized using thermogravimetry （TG）, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, N2-adsorption and temperature-programmed desorption of CO2 （CO2-TPD）. The results indicate that the amounts of very strong basic sites and high basicity strength on CaO sample are key factors for its excellent catalytic performance. In contrast, the surface area, porosity and the surface structure of CaO sample have a relatively minor effect on the catalytic activity. CaO sample, obtained by the decomposition of Ca（OH）2, prepared by precipitating calcium nitrate with sodium hydroxide in ethylene glycol solution, exhibits the highest amount of very strong basic sites and stronger strength of basic sites, and therefore it catalyses the epoxidation of styrene with the highest rate among the tested CaO samples. Under the selected reaction conditions, the selectivity of 97.5% to styrene oxide at a conversion in excess of 99% could be obtained.

Investigation of protein-styrene oxide adducts as a molecular biomarker of human exposed to styrene

Hemoglobin-styrene oxide adducts in blood have been studied as a molecular biomarker of worker exposed to styrene. Determination of protein-styrene oxide adducts in different biological samples with modified Raney-Ni procedure is described in this paper. The following biological samples have been investigated: fresh rat blood reacted with styrene oxide in vitro: rat blood reacted with styrene or styrene oxide in vivo: vein blood from workers exposed to styrene in two factories. The data showed that there was a good linear dose-response relationship between reacting dose of styrene oxide or styrene and amount of protein-styrene oxide adducts in both in vitro and in vivo experiments. For human samples, a dose-response relationship between protein adducts and styrene exposure can be found in glass fiber factory, but not in piano manufacture plant.

Analysis of styrene oxide-hemoglobin adducts at different binding sites

An assay was described for measures of adducts of styrene oxide (SO) with molecules of hemoglobin(Hb) which have been modified at residues containing either carboxylic acid or sulfhydryl groups. The method employs two steps. In the first, SO carboxylic acid adducts are hydrolyzed in basic medium to liberate styrene glycol(SG). Then, the remaining residues are reacted with a reductive catalyst (Raney nickel) to liberate the two positional isomers of SO cysteine adducts, i.e., 1 phenylethanol (1 PE) and 2 phenylethanol (2 PE). The liberated products are derivatized with pentafluorobenzoyl chloride and measured by GC NICI MS. The assay was evaluated with SO adducts of Hb which had been produced in the blood of Sprague Dawley rats following (a) in vitro modification(0—300m mol/L SO) or (b) i.p administration of either SO(0—1 mmol/kg) or styrene (0—3 mmol/kg). Levels of each of the three analytes (SG, 1 PE, and 2 PE) increased with dose in hemoglobin. The ratios of cysteine adducts to carboxylic acid adducts varied significantly among experiments. Ratios of 2 PE to 1 PE were much more consistent (2 PE/1 PE=6.9 (SE=1.5)) suggesting that binding of SO to cysteine residues of blood proteins is greatly preferred at the α position rather than the β position both in vitro and in vivo. The lowest detectable adduct concentration, using 10 mg of protein, was 8 pmol/g protein for SG,5 pmol/g protein for 1 PE, and 0.6 pmol/g protein for 2 PE. No significant change of adduct level was found during storage of proteins at -80℃ for 1 year.

SYNTHESIS AND CHARACTERIZATION OF POLY(STYRENE - ETHYLENE OXIDE) DIBLOCK COPOLYMERS

Well - defined diblock copolymers Of styrene (St ) and ethylene oxide (EO )have been prepared by sequential living anionic polymerization of the twocomonomers in THF. Diphenyl methyl potassium has been used as initiator. Theblock copolymers were characterized in detail by methods Of size exclusion chromatography (SEC ) , 1H - Nab, FT - IR, dynamic mechanical analysis(Daal ) and WAXD.

Synthesis of Ln-doped MCM-41 mesoporous materials and their catalytic performance in oxidation of styrene

Using cetyl-trimethyl-ammonium bromide （CTMAB） as the template agent and tetraethylorthosilicate （TEOS） as the silica source, the MCM-41 mesoporous materials were synthesized with La or Ce incorporated in the framework under hydrothermal conditions. The structure and the state of La or Ce were investigated through the analyses of XRD, nitrogen adsorption-desorption, FT-IR, and UV-Vis. XRD and N2 adsorption-desorption results showed that Ln-MCM-41 exhibited the loss of the lattice ordering of the MCM-41 construct, and larger unit cell parameter and pore diameter than pure silica MCM-41. The FT-IR and UV-Vis results indicated the presence of isolated tetra-coordinated La or Ce ions in the framework and other Ln species dispersed highly on the Ln-MCM-41 surface simultaneously. Furthermore, their catalytic behaviors in the oxidation of styrene were studied using H2O2 as the oxidant. The La-MCM-41 catalysts exhibited high reactivity and the reactivity increased with the increase of the La content in the La-MCM-41 samples. On the contrary, Ce-MCM-41 catalysts showed low reactivity in the oxidation of styrene and the conversion of styrene decreased with the increase of the Ce content in the Ce-MCM-41 samples.

Alumina-boron catalysts for oxidative dehydrogenation of ethylbenzene to styrene: Influence of alumina-boron composition and method of preparation on catalysts properties

Different mole ratio Al-B catalysts (Al-10B to Al-35B) were synthesized by using sol-gel (SG) method. Ethyl benzene (EB) dehydrogenation in the presence of oxygen and water steam was carried out on these catalysts at 450–500℃ with EB contact time of 0.54 gcat.s.cm^–3. Acidity of Al-B catalysts was estimated by using NH3-TPD-mass spectral analysis studies. SEM-mapping images revealed fine distribution of boron up to 15% of its loading in alumina (Al-15B), whereas, boron aggregation was observed in higher boron content (Al-25B and Al-35B) catalysts. Essentially, acid sites of very weak strength (Tmax ≤ 125℃) were observed for Al and Al-10B catalysts and resulted in low EB conversion and styrene yield. On the other hand, acid sites of weak strength (Tmax ≤ 180℃) were observed for Al-25B and Al-35B catalysts and resulted in high EB conversion. However, greater styrene yield (43.2%) with reasonable EB conversion (46%) was obtained on acid sites of weak moderate strength in Al-15B catalyst. Further, Al-15B catalyst was synthesized by using co-precipitation (COP) and impregnation (IMP) methods. Acid sites related to NOx formation during the NH3-TPD-mass analysis on IMP and COP catalyst essentially improved the EB conversion to 66% and 63% respectively at 500℃. However, these acid sites were diminished in Al-B SG catalyst and resulted in 50% of EB conversion at 500 ℃. At 50% of EB conversion level, styrene selectivity of 73%, 82.5% and 84% were observed on Al-B IMP, Al-B COP and Al-SG catalysts, respectively. Hence, different method of preparation of Al-B catalyst generated acid sites of different strength and density and thereby influenced the styrene formation.

Preparation of ZSM-5 containing vanadium and Br?nsted acid sites with high promoting of styrene oxidation using 30% H_2O_2

Design and synthesis of low cost and efficacious industrial catalyst for the oxidation of styrene has been an important research project.Herein,ZSM-5 zeolite containing tetrahedral vanadium(V)and Br?nsted acid sites(V-H-ZSM-5)was prepared,and identified by characterizations such as XRD,SEM,UV–vis,NH3-TPD,H2-TPR N2-adsorption/desorption and FTIR.V-H-ZSM-5 performed extremely enhanced catalytic activity for the oxidation of styrene with 30%H2O2 at 40°C.Moreover,in-situ FTIR spectrum was used to investigate the catalytic mechanism.The results demonstrate that Br?nsted acid site could not only increase the adsorption concentration of styrene in the micropores of V-H-ZSM-5 via theπcomplex interaction between double bond of styrene and Br?nsted acid sites,but also increase the oxidation potential of H2O2.The synergetic action of tetrahedral vanadium(V)and Br?nsted acid enhanced the catalytic activity for the oxidation of styrene with 30%H2O2.Impressively,V-H-ZSM-5 performed high reusability within five runs at a low reaction temperature(40°C)for the first time.

Synthesis and catalytic activity of SBA-15 supported catalysts for styrene oxidation

Cu(II) and Mn(II) metals embedded on mesoporous SBA-15 were synthesized by co-precipitation technique.The support and catalysts were characterized by SEM–EDX,TEM,BET,XRD and ICP-AES methods.The catalytic activity of these catalysts was evaluated for styrene oxidation at various reaction conditions such as styrene to TBHP mole ratio,temperature,catalyst amount by using TBHP as an oxidizing agent.Major reaction products were styrene oxide and benzaldehyde and highest styrene conversion(97.3%) was observed at styrene to TBHP mole ratio of 1:4,temperature at 80 °C and 20 mg of catalyst.Further,the recyclability of the catalysts was observed and found that they can be recycled three times without major loss in their activity and selectivity.

Synchronous Synthesis and Immobilization of Metal Phthalocyanine for Aerobic Oxidation of Styrene

In this study,the precursor 4-(4-carboxy-phenoxy)phthalonitrile(CPPN)was first bonded onto the silica gel surface modified with poly(glycidyl methacrylate)(PGMA)(PGMA/SiO2)to prepare CPPN-PGMA/SiO2,and metal phthalocyanine(MPc;M=Co,Fe,Cu,Mn)was supported on the PGMA/SiO2 surface to prepare MPc-PGMA/SiO2 by synchronous synthesis and immobilization with phthalonitrile and metal salt in the solution.The chemical composition and surface morphology were characterized by the Fourier transform infrared(FTIR)spectroscopy,UV-Vis spectroscopy,scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),and thermogravimetry analysis(TGA).The catalytic performance of MPc-PGMA/SiO2 in epoxidation of styrene was also investigated with molecular oxygen acting as the oxidant.The results show that MPc-PGMA/SiO2 can efficiently and selectively catalyze molecular oxygen for oxidation of styrene to styrene oxide under mild conditions.However,the catalytic activity differs substantially depending on the central metal,and a highest catalytic activity is achieved by CoPc-PGMA/SiO2.The CoPc-PGMA/SiO2 amount and temperature can also affect the catalytic oxidation of styrene,and at normal atmospheric pressure,a maximum conversion rate of styrene(99%)and selectivity of styrene oxide(53%)are obtained using 0.1 g of CoPc-PGMA/SiO2(22.61μmol of CoPc)at 100℃ for 6 h.CoPc-PGMA/SiO2 also has excellent reusability,and the conversion rate of styrene is still over 90%after 5 cycles.

Oxidation of Styrene with Molecular Oxygen in Supercritical CO_2

The oxidation of styrene with molecular oxygen catalyzed by PdCl2+CuCl2 has been investigated in supercritical CO2 with a batch reactor. The oxidative system of styrene contains four components at the beginning and seven components during the reaction. The critical temperature, critical pressure, and critical density at different conversions are determined by using a high-pressure view cell. The effect of phase behavior on the conversion and selectivity were studied. Experimental results showed that the critical parameters of the reaction mixture at fixed initial molar ratio changed with the conversion of reactant. The conversion of styrene reached maximum near the critical density of the reaction mixture. Product selectivity also varied with density of reaction mixture and could be tuned to some degree.

Oxidative Methylation of Toluene with Methane over Basic Zeolite Catalysts Promoted with Alkali Metal Bromides and Alkali Metal Oxides

The catalytic effects for the oxidative methylation of toluene with methane over the basic zeolite catalysts prepared by promoting KY, KX, KM, KZSM-5 or KP with alkali-metal bromides and alkali-metal oxides have been investigated comparatively. The alkali-metal bromides promoted substrates are more effective than the alkali-metal oxides promoted systems. Moreover, the NaBr promoted systems are more active than KBr promoted systems. The most effective catalytic system (8wt%NaBr)/KZSM-5 gave a toluene conversion as high as 76.3% and a total C-8 selectivity of 76.4% (styrene/ethylbenzene=9.76) resulting in a total C-8 yield of 58.3%.

Designing polyoxometalate-based metal-organic framework for oxidation of styrene and cycloaddition of CO_(2) with epoxides

A photoactive polyoxometalate-based metal-organic framework (POMOF),NiW-DPNDI,was synthesized by combination of Ni(Ⅱ) ions,[ZnW_(12)O_(40)]^(6–)anions,and N,N’-bis(4-pyridylmethyl)naphthalene diimide(DPNDI) molecules into one single framework.Ni W-DPNDI displays a three-dimensional structure by the strong anion···π interactions between the trapped[ZnW_(12)O_(40)]^(6–)anions and the electron-deficient naphthalenic ring centroids and theπ-πstacking interactions between DPNDI moieties.Ni W-DPNDI displayed a highly efficient hole-electron separation and ordered electron transfer under irradiation,thus ensuing its excellent photocatalysis in oxidation of styrene to produce benzaldehyde.In addition,it gave a high efficiency for styrene oxide under thermocatalytic conditions.Because the carbonic anhydrase (CA)-mimicking Ni sites and the negative electron-enriched[ZnW_(12)O_(40)]^(6–)anions are well aligned in the pores,it can promote the cycloaddition of CO_(2) with epoxides under mild conditions.

Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution

Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications,especially in catalysis,as compared with their conventional crystalline counterparts.It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications.Here,we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials,including PdRu,PdRh,and PdRuRh.The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated.Specifically,the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic(fcc)phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction,respectively.Moreover,when used as an electrocatalyst for hydrogen evolution reaction(HER),the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values,outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.

无有机模板法制备Cu-ZSM-5催化剂及其选择性催化氧化苯乙烯

不使用任何有机模板剂,硝酸铜和正硅酸四乙酯(TEOS)经过酸性水解、碱性陈化和水热晶化,制备得到四配位铜修饰ZSM-5沸石(Cu-ZSM-5)。考察凝胶的Si/Al摩尔比、pH值、晶化温度和晶化时间对Cu-ZSM-5的晶型和相对结晶度的影响。采用X射线衍射(XRD)、红外光谱(FT-IR)、紫外漫反射谱和X-射线光电子能谱等手段对Cu-ZSM-5进行分析表征。结果表明:Cu-ZSM-5沸石具有MFI结构,结晶度高,无其他杂晶;铜原子以四配位为主。四配位铜是催化氧化苯乙烯的活性位点;在m(Cu-ZSM-5-50)=0.1 g、n(TBHP)/n(Styrene)=1.5、T=60℃、t=5 h条件下,苯乙烯转化率和苯甲醛选择性分别为76.5%和69.4%,表明Cu-ZSM-5-50具有较高的催化活性和较好的重复利用性。该制备方法不使用有机模板剂,无需高温焙烧,Cu-ZSM-5催化剂的制备成本大大降低。

我国苯乙烯合成技术研究进展

苯乙烯是一种重要的有机化工产品,广泛应用于合成树脂和合成橡胶等领域。文章介绍了我国CO_(2)氧化乙苯脱氢、苯乙炔选择性加氢、甲苯和甲醇侧链烷基化等合成苯乙烯技术的研究进展,并提出了今后的发展建议。