Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quater...Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.展开更多
Some highly active η5-pentamethylcyclopentadienyltribenzyloxy titanium complexes [Cp Ti（OBz）3] activated by modified methylaluminoxane （mMAO） were prepared and used as the catalyst for styrene syndiospecific poly...Some highly active η5-pentamethylcyclopentadienyltribenzyloxy titanium complexes [Cp Ti（OBz）3] activated by modified methylaluminoxane （mMAO） were prepared and used as the catalyst for styrene syndiospecific polymerization and propene atactic polymerization. Styrene could be copolymerized with propene when the propene was prepolymerized for a period, to which styrene and tri-isobutylaluminum （TIBA） were then added. The titled block copolymer together with the related homopolymers was obtained. The copolymerization porducts can be divided into the homopolymers and the copolymer by successive solvent extraction with boiling butanone, heptane and tetrahydrofuran （THF）, and each fraction was characterized by 13C NMR, DSC and WAXD. It was found that aPS and aPP were soluble in boiling butanone and heptane respectively. The block copolymer （sPS-b-aPP） composed of syndiottactic polystyrene segment was soluble in boiling THF and the residue was chiefly sPS.展开更多
Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were c...Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were characterized by an array of techniques including NMR,GPC,TEM,WAXD and DSC.The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units,and their M_W is in the range of 10~5-10~6.By enhancing the electron withdrawing of th...展开更多
The polymerization behaviors of Styrene (St) in the presence of CuX/L [X=Cl or Br; L= 2,2 bipyridine (bpy), 1,10 phenanthroline (phen) or 4,7 diphenyl 1,10 phenanthroline (DPP) ] and R X (R=trichloromethyl, benzyl o...The polymerization behaviors of Styrene (St) in the presence of CuX/L [X=Cl or Br; L= 2,2 bipyridine (bpy), 1,10 phenanthroline (phen) or 4,7 diphenyl 1,10 phenanthroline (DPP) ] and R X (R=trichloromethyl, benzyl or allyl; X=Cl or Br) have been studied and examined. In a CuCl/bpy/RCl/St system, a bimodal GPC peak at the early stage of polymerization was observed, and a concept of multi active species was proposed to explain this phenomenon. In a CuCl/phen (DPP)/RCl/St system, the \%M\%\-n of polystyrene (PS) increased linearly with St conversion and ln[M] o/[M] also increased linearly with time, indicating the living nature of this system. Furthermore, the stability of the propagating active species in a CuBr/phen/RBr/St system is higher than that in the CuBr/phen/RBr/St system.展开更多
The copolymerization of styrene (St) with maleic anhydride (MAh) under gamma radiation at room temperature inthe presence of benzyl dithiobenzoate (BDTB) was found to display 'living' nature evidenced by const...The copolymerization of styrene (St) with maleic anhydride (MAh) under gamma radiation at room temperature inthe presence of benzyl dithiobenzoate (BDTB) was found to display 'living' nature evidenced by constant concentration ofchain radicals during the copolymerization, linear evolution of molecular weights with conversion and narrow molecularweight distribution (Mw/Mn ＝ 1.23-1.35). The compositional analysis and the sequence structural information of thecopolymers obtained from DEPT (Distortionless Enhancement by Polarization Transfer) experiments demonstrate that thecopolymers obtained also possess strictly alternating structure.展开更多
The oil-in-water microemulsion containing N-butyl maleimide（NBMI. M1） and styrene（St, M2） was prepared. The complexation properties of NBMI and St in microemulsion were investigated by means of 1H-NMR. With the pa...The oil-in-water microemulsion containing N-butyl maleimide（NBMI. M1） and styrene（St, M2） was prepared. The complexation properties of NBMI and St in microemulsion were investigated by means of 1H-NMR. With the participation of charge-transfer complex（CTC）. four reactivity ratios and the relative reactivity of free monomers and CTC were obtained. The result was compared with that measured by Mayo-Lewis method.展开更多
Thermoregulated phase-separable Ru3(CO)12/PETPP (PETPP=P[p-C6H4O (CH2CH2O)n H]3, n=6) complex catalyst was first applied in the hydrogenation of styrene. Under the conditions: P(H2)=2.0MPa, T=90C, styrene could be com...Thermoregulated phase-separable Ru3(CO)12/PETPP (PETPP=P[p-C6H4O (CH2CH2O)n H]3, n=6) complex catalyst was first applied in the hydrogenation of styrene. Under the conditions: P(H2)=2.0MPa, T=90C, styrene could be completely transferred and the yield of ethylbenzene reached up to 99.5%. After simple decantation, the catalyst could be reused for ten times without decreasing in activity.展开更多
The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCI) (50/50 V/V) solvent mixture at -80℃. The initiator 1,1-diphen...The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCI) (50/50 V/V) solvent mixture at -80℃. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCI) was formed in situ in conjunction with titanium tetrachloride (TiCl4). The Lewis acidity of TiCl4 was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)4) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.展开更多
The morphology effect of Zr-doped CeO_2 was 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 CeO_2...The morphology effect of Zr-doped CeO_2 was 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 CeO_2 nanorods exhibited the highest catalytic performance(yield of styrene oxide and TOF value)followed by nanoparticles and nanocubes. For the Zr-doped CeO_2 nanorods, 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 CeO_2 nanorods while(100)and(111) for nanocubes,(111) for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeO_2 nanorods is mainly attributed to the higher percentage of Ce^(3+)species and more oxygen vacancies, which are associated with their exposed(100) and(110) crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeO_2 nanorods did not lose its initial high catalytic activity after five successive recycles.展开更多
Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ...Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ethylbenzene and xylene.In this study,a new way is introduced to improve the catalytic performance by means of assisting basic compounds as co-catalysts during the toluene side-chain alkylation with methanol to styrene.As a result,high activity of side-chain alkylation appears over the basic Cs-modified zeolite catalysts prepared by ion exchange and impregnation methods.This high performance should be mainly attributed to two co-catalysis actions:(1)the promotion of basic compounds for methanol dehydrogenation to formaldehyde as the intermediate for side-chain alkylation;(2)the suppression of the styrene transfer hydrogenation on basic Cs-modified zeolites to avoid the formation of ethylbenzene.Especially for Cs_(2)O/CsX-ex catalyst,the addition of 2%mol/mol 2-picoline in reaction mixture could achieve both 12.3%toluene conversion and 84.1%styrene selectivity.Whereas the higher concentration of 2-picoline(>6%mol/mol)caused an inhibition to the catalytic activity because the excessive basic compound poisoned the combined acid-base pathway required for the side-chain alkylation process.In addition,two possible side-chain alkylation reaction routes on Cs-modified zeolite under the different 2-picoline absorption were described.展开更多
Disubstituted oxazoles were prepared conveniently by treatment of aromatic -methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in one-pot process.
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 phthalocy...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.展开更多
Styrene is extensively used in industry,but its ototoxicity,in particular in the pregnant female and the offspring,is still not well understood.In the current study,young adult male rats and pregnant female rats were ...Styrene is extensively used in industry,but its ototoxicity,in particular in the pregnant female and the offspring,is still not well understood.In the current study,young adult male rats and pregnant female rats were exposed to styrene by gavage at different doses.The young adult male rats received a total of 12g/kg styrene within different periods (800 mg/kg/day for 5 days/week for 3 weeks,400 mg/kg/day for 5 days/week for 6 weeks,200 mg/kg/day for 5 days/week for 12 weeks,and 100 mg/kg/day for 5 days/week for 24 weeks) and the pregnant female rats received styrene at a dose of 400 mg/kg/day for 5 days/week for 6 weeks starting from the gestation day-4.Hearing loss and hair cell loss were assessed 5 days after the styrene treatment in the young adult male rats and in the mother rats.The cochlear impairments in the rat pups were examined 2 months after their birth.The styrene exposure caused hearing loss and hair cell loss starting from the mid-frequency region in the third row of outer hair cells (OHCs) and the impairments appeared to be related to the dosing level in each single day.Significantly,the styrene exposure to the pregnant rats interfered with auditory functional development of their fetus,leading to a deficit of cochlear amplification,although the OHCs appeared to develop well.The results indicate that a short-term high-level styrene exposure may be more ototoxic than a long-term low-level exposure for a similar total styrene dose and the styrene in the pregnant woman's body may interfere with auditory development of their fetus.展开更多
Waste tire powder, as waste rubber WR was subjected to grafting with styrene (St) and maleic anhydride (MA). Hydrogen peroxide H2O2 was used to initiate the free radical copolymerization of St onto WR. A thermal initi...Waste tire powder, as waste rubber WR was subjected to grafting with styrene (St) and maleic anhydride (MA). Hydrogen peroxide H2O2 was used to initiate the free radical copolymerization of St onto WR. A thermal initiation was used in case of grafting of MA onto WR. Effect of initiator and monomer concentrations together with the influence of reaction temperature and reaction time were investigated. The grafting was estimated by weight, and the grafted copolymers were characterized by FT/IR, DSC and SEM to prove the grafting. It has found that the grafting increases with increase monomer and initiator concentrations. The increase in the reaction temperature and time also causes increasing levels of the grafted St and MA.展开更多
With the advent of plastics and the wide range of fillers that are available have made modifications as precise as the tailored resins themselves. To modify the properties of polymer either by using fillers or by prep...With the advent of plastics and the wide range of fillers that are available have made modifications as precise as the tailored resins themselves. To modify the properties of polymer either by using fillers or by preparation of polymer blends gives rise to new materials with tailored properties. More complex, three-component systems, obtained by the addition of polymeric modifier to polymer filled composites may be of interest. Use of Fly ash cenospheres is very attractive because it is inexpensive and its use can reduce the environmental pollution to a significant extent. In the present study, Poly (Methyl Methacrylate) (PMMA)-Fly ash cenospheres composites were prepared using extrusion followed by Injection molding. The effect of matrix modification with Methyl methacrylate– acrylonitrile -butadiene–styrene (MABS) on the performance of PMMA- Fly ash cenospheres compositions was also, studied. It was found that with the addition of Fly ash cenospheres particulate as filler in PMMA showed marginal reduction in Tensile Strength, % Elongation and Impact strength and improvement in Flexural Strength, Heat Deflection Temperature and Vicat Softening Point. Compared with PMMA-cenospheres composites, the notched Impact Strength of the PMMA/MABS/cenospheres composites showed marginal enhancement in values at higher loading of cenospheres. The optimum performances in mechanical and thermal properties were obtained when the ratio of MABS to cenospheres was 1:2.展开更多
Radiation induced grafting of viscose rayon fabrics, consisting mainly of cellulose fibers, with some acrylic acid derivatives, namely methyl acrylate, acrylamide and acrylonitrile, and also styrene, has been studied....Radiation induced grafting of viscose rayon fabrics, consisting mainly of cellulose fibers, with some acrylic acid derivatives, namely methyl acrylate, acrylamide and acrylonitrile, and also styrene, has been studied. The resultant graft yields have been determined as a function of the applied different experimental parameters. The impact of the graft yields on the physicochemical properties of viscose rayon fabrics such as swelling, moisture absorption, tensile strength, elongation at break, crease recovery angle and also dyeing ability of the grafted fabrics, has been also studied.展开更多
Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group fr...Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group from Comilla region in Bangladesh. Three sets of samples were prepared for three different wt% (5%, 10% and 20%) of fiber contents. The mechanical (tensile strength, flexural stress, micro hardness, Leeb’s rebound hardness) and physical (bulk density and water absorption) properties were measured. The observed result reveals that the tensile strength (TS) and flexural stress (FS) were decreased with increasing fiber contents in the PF-ABS composites except 10% fiber content.展开更多
The neodymium complex supported on styrene-maleic anhydride copolymer （SMA·Nd） has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA·Nd...The neodymium complex supported on styrene-maleic anhydride copolymer （SMA·Nd） has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA·Nd polymeric complex is characterized by IR and its catalytic activity, and the polymerization features have been investigated in comparison with that of the conventional Ziegler-Natta catalysts. When [Nd]=1×10<sup>-3</sup> mol/L, [M]=5mol/L, Al/Nd=170（mol ratio） and CCl<sub>4</sub>/Nd=50（mol ratio）, the polymerization conversion of styrene gets to 51.6% in six hours, and the catalytic activity reaches 1852 gPS/gNd, which is much higher than that of conventional rare earth catalysts. The polymerization reaction has an induction period and shows some characteristics of chain polymerization. The polymerization rate is the first order with respect to the concentration of styrene monomer. Addition of FeCl<sub>3</sub> does not suppress the polymerization.展开更多
基金financial supported by the National Natural Science Foundation of China (22078065)Key Program of Qingyuan Innovation Laboratory (00221001)Quanzhou City Science & Technology Program of China (2020C008R)。
文摘Catalytic epoxidation of alkenes is an important type of organic reaction in chemical industry,and the deep insight into catalyst deactivation will help to develop new epoxidation process.In this work,series of quaternary ammoniums bearing different cationic sizes,i.e.MTOA+(methyltrioctylammonium,[(C_(8)H_(17))_(3)CH_(3)N]+),HTMA+(hexadecyltrimethylammonium,[(C_(16)H_(33))(CH_(3))_(3)N]+) and DMDOA+(dimethyldioctadecylammonium,[(C_(18)H_(37))_(2)(CH_(3))_(2)N]+) were incorporated with polyoxometalate (POM) anions to prepare phase transfer catalysts (PTCs),which were used in the styrene epoxidations.Among them,(MTOA)_(3)PW_(4)O_(24)exhibits the best catalytic performance judged from the highest styrene conversion rate(52%) and styrene oxide selectivity (93%),during which the styrene epoxidation conditions were optimized.Meanwhile,the deactivation mechanism of this kind of PTCs was proposed firstly,i.e.in the case of low H_(2)O_(2) content,the oxidant can only be used in the styrene epoxidation,in which the catalyst can transform into stable Keggin-type POM.But when the content of H_(2)O_(2) is higher,the excess H_(2)O_(2) can reactivate the Keggin-type POM into active (PW_(4)O_(24))_(3)-anions,which can trigger the ring-opening polymerization of styrene oxide.Consequently,the catalyst is deactivated by adhered poly(styrene oxide)irreversibly,which was determined by NMR spectra.In this situation,the active moiety{PO_(4)[WO(O_(2))_(2)]_(4)}_(3)-in phase-transfer catalytic system can break into some unidentified species with low W/P ratio with the presence of epoxides.This work will be beneficial for the design of new PTCs in alkene epoxidation in fine chemical industry.
文摘Some highly active η5-pentamethylcyclopentadienyltribenzyloxy titanium complexes [Cp Ti（OBz）3] activated by modified methylaluminoxane （mMAO） were prepared and used as the catalyst for styrene syndiospecific polymerization and propene atactic polymerization. Styrene could be copolymerized with propene when the propene was prepolymerized for a period, to which styrene and tri-isobutylaluminum （TIBA） were then added. The titled block copolymer together with the related homopolymers was obtained. The copolymerization porducts can be divided into the homopolymers and the copolymer by successive solvent extraction with boiling butanone, heptane and tetrahydrofuran （THF）, and each fraction was characterized by 13C NMR, DSC and WAXD. It was found that aPS and aPP were soluble in boiling butanone and heptane respectively. The block copolymer （sPS-b-aPP） composed of syndiottactic polystyrene segment was soluble in boiling THF and the residue was chiefly sPS.
文摘Emulsion copolymerization of styrene and ethylene catalyzed by a series of neutral nickel(Ⅱ) complexes was carried out in an aqueous system to give high-molecular-weight copolymers.The copolymers and emulsions were characterized by an array of techniques including NMR,GPC,TEM,WAXD and DSC.The results indicate that the copolymers obtained are mostly block copolymers of polyethylene with random insertion of styrene units,and their M_W is in the range of 10~5-10~6.By enhancing the electron withdrawing of th...
文摘The polymerization behaviors of Styrene (St) in the presence of CuX/L [X=Cl or Br; L= 2,2 bipyridine (bpy), 1,10 phenanthroline (phen) or 4,7 diphenyl 1,10 phenanthroline (DPP) ] and R X (R=trichloromethyl, benzyl or allyl; X=Cl or Br) have been studied and examined. In a CuCl/bpy/RCl/St system, a bimodal GPC peak at the early stage of polymerization was observed, and a concept of multi active species was proposed to explain this phenomenon. In a CuCl/phen (DPP)/RCl/St system, the \%M\%\-n of polystyrene (PS) increased linearly with St conversion and ln[M] o/[M] also increased linearly with time, indicating the living nature of this system. Furthermore, the stability of the propagating active species in a CuBr/phen/RBr/St system is higher than that in the CuBr/phen/RBr/St system.
文摘The copolymerization of styrene (St) with maleic anhydride (MAh) under gamma radiation at room temperature inthe presence of benzyl dithiobenzoate (BDTB) was found to display 'living' nature evidenced by constant concentration ofchain radicals during the copolymerization, linear evolution of molecular weights with conversion and narrow molecularweight distribution (Mw/Mn ＝ 1.23-1.35). The compositional analysis and the sequence structural information of thecopolymers obtained from DEPT (Distortionless Enhancement by Polarization Transfer) experiments demonstrate that thecopolymers obtained also possess strictly alternating structure.
文摘The oil-in-water microemulsion containing N-butyl maleimide（NBMI. M1） and styrene（St, M2） was prepared. The complexation properties of NBMI and St in microemulsion were investigated by means of 1H-NMR. With the participation of charge-transfer complex（CTC）. four reactivity ratios and the relative reactivity of free monomers and CTC were obtained. The result was compared with that measured by Mayo-Lewis method.
基金We are grateful for the financial support from the National Natural Science Foundation of China(Grant no.29906001).
文摘Thermoregulated phase-separable Ru3(CO)12/PETPP (PETPP=P[p-C6H4O (CH2CH2O)n H]3, n=6) complex catalyst was first applied in the hydrogenation of styrene. Under the conditions: P(H2)=2.0MPa, T=90C, styrene could be completely transferred and the yield of ethylbenzene reached up to 99.5%. After simple decantation, the catalyst could be reused for ten times without decreasing in activity.
基金supported by the Beijing Municipal Project for Developing Advanced Human Resources for Higher Education(Elastomers and Biomaterials).
文摘The living cationic polymerization of 4-[2-(tert-butyldimethylsiloxy)ethyl]styrene (TBDMES) was studied in methylcyclohexane (MeChx)/methylchloride (MeCI) (50/50 V/V) solvent mixture at -80℃. The initiator 1,1-diphenylethylene (DPE) capped 2-chloro-2,4,4-trimethylpentane (TMPCI) was formed in situ in conjunction with titanium tetrachloride (TiCl4). The Lewis acidity of TiCl4 was decreased by the addition of titanium(IV) isopropoxide (Ti(OiPr)4) to accomplish living polymerization of TBDMES. Hydrolysis of poly(TBDMES) in the presence of tetra-butylammonium fluoride yielded poly[4-(2-hydroxyethyl)styrene] (poly(HOES)). FT-IR, NMR and DSC demonstrated the hydrolysis was complete.
基金the financial support from NNSFC(Project 21373054,21303023,21173052)the Natural Science Foundation of Shanghai Science and Technology Committee(08DZ2270500)
文摘The morphology effect of Zr-doped CeO_2 was 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 CeO_2 nanorods exhibited the highest catalytic performance(yield of styrene oxide and TOF value)followed by nanoparticles and nanocubes. For the Zr-doped CeO_2 nanorods, 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 CeO_2 nanorods while(100)and(111) for nanocubes,(111) for nanoparticles. The remarkably increased catalytic activity of the Zrdoped CeO_2 nanorods is mainly attributed to the higher percentage of Ce^(3+)species and more oxygen vacancies, which are associated with their exposed(100) and(110) crystal planes. Furthermore, recycling studies proved that the heterogeneous Zr-doped CeO_2 nanorods did not lose its initial high catalytic activity after five successive recycles.
基金Supported by the National Natural Science Foundation of China(#91534115).
文摘Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ethylbenzene and xylene.In this study,a new way is introduced to improve the catalytic performance by means of assisting basic compounds as co-catalysts during the toluene side-chain alkylation with methanol to styrene.As a result,high activity of side-chain alkylation appears over the basic Cs-modified zeolite catalysts prepared by ion exchange and impregnation methods.This high performance should be mainly attributed to two co-catalysis actions:(1)the promotion of basic compounds for methanol dehydrogenation to formaldehyde as the intermediate for side-chain alkylation;(2)the suppression of the styrene transfer hydrogenation on basic Cs-modified zeolites to avoid the formation of ethylbenzene.Especially for Cs_(2)O/CsX-ex catalyst,the addition of 2%mol/mol 2-picoline in reaction mixture could achieve both 12.3%toluene conversion and 84.1%styrene selectivity.Whereas the higher concentration of 2-picoline(>6%mol/mol)caused an inhibition to the catalytic activity because the excessive basic compound poisoned the combined acid-base pathway required for the side-chain alkylation process.In addition,two possible side-chain alkylation reaction routes on Cs-modified zeolite under the different 2-picoline absorption were described.
文摘Disubstituted oxazoles were prepared conveniently by treatment of aromatic -methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in one-pot process.
基金This work was supported by the Natural Science Foundation of the Shanxi Province of China(No.201801D121069).
文摘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.
文摘Styrene is extensively used in industry,but its ototoxicity,in particular in the pregnant female and the offspring,is still not well understood.In the current study,young adult male rats and pregnant female rats were exposed to styrene by gavage at different doses.The young adult male rats received a total of 12g/kg styrene within different periods (800 mg/kg/day for 5 days/week for 3 weeks,400 mg/kg/day for 5 days/week for 6 weeks,200 mg/kg/day for 5 days/week for 12 weeks,and 100 mg/kg/day for 5 days/week for 24 weeks) and the pregnant female rats received styrene at a dose of 400 mg/kg/day for 5 days/week for 6 weeks starting from the gestation day-4.Hearing loss and hair cell loss were assessed 5 days after the styrene treatment in the young adult male rats and in the mother rats.The cochlear impairments in the rat pups were examined 2 months after their birth.The styrene exposure caused hearing loss and hair cell loss starting from the mid-frequency region in the third row of outer hair cells (OHCs) and the impairments appeared to be related to the dosing level in each single day.Significantly,the styrene exposure to the pregnant rats interfered with auditory functional development of their fetus,leading to a deficit of cochlear amplification,although the OHCs appeared to develop well.The results indicate that a short-term high-level styrene exposure may be more ototoxic than a long-term low-level exposure for a similar total styrene dose and the styrene in the pregnant woman's body may interfere with auditory development of their fetus.
文摘Waste tire powder, as waste rubber WR was subjected to grafting with styrene (St) and maleic anhydride (MA). Hydrogen peroxide H2O2 was used to initiate the free radical copolymerization of St onto WR. A thermal initiation was used in case of grafting of MA onto WR. Effect of initiator and monomer concentrations together with the influence of reaction temperature and reaction time were investigated. The grafting was estimated by weight, and the grafted copolymers were characterized by FT/IR, DSC and SEM to prove the grafting. It has found that the grafting increases with increase monomer and initiator concentrations. The increase in the reaction temperature and time also causes increasing levels of the grafted St and MA.
文摘With the advent of plastics and the wide range of fillers that are available have made modifications as precise as the tailored resins themselves. To modify the properties of polymer either by using fillers or by preparation of polymer blends gives rise to new materials with tailored properties. More complex, three-component systems, obtained by the addition of polymeric modifier to polymer filled composites may be of interest. Use of Fly ash cenospheres is very attractive because it is inexpensive and its use can reduce the environmental pollution to a significant extent. In the present study, Poly (Methyl Methacrylate) (PMMA)-Fly ash cenospheres composites were prepared using extrusion followed by Injection molding. The effect of matrix modification with Methyl methacrylate– acrylonitrile -butadiene–styrene (MABS) on the performance of PMMA- Fly ash cenospheres compositions was also, studied. It was found that with the addition of Fly ash cenospheres particulate as filler in PMMA showed marginal reduction in Tensile Strength, % Elongation and Impact strength and improvement in Flexural Strength, Heat Deflection Temperature and Vicat Softening Point. Compared with PMMA-cenospheres composites, the notched Impact Strength of the PMMA/MABS/cenospheres composites showed marginal enhancement in values at higher loading of cenospheres. The optimum performances in mechanical and thermal properties were obtained when the ratio of MABS to cenospheres was 1:2.
文摘Radiation induced grafting of viscose rayon fabrics, consisting mainly of cellulose fibers, with some acrylic acid derivatives, namely methyl acrylate, acrylamide and acrylonitrile, and also styrene, has been studied. The resultant graft yields have been determined as a function of the applied different experimental parameters. The impact of the graft yields on the physicochemical properties of viscose rayon fabrics such as swelling, moisture absorption, tensile strength, elongation at break, crease recovery angle and also dyeing ability of the grafted fabrics, has been also studied.
文摘Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group from Comilla region in Bangladesh. Three sets of samples were prepared for three different wt% (5%, 10% and 20%) of fiber contents. The mechanical (tensile strength, flexural stress, micro hardness, Leeb’s rebound hardness) and physical (bulk density and water absorption) properties were measured. The observed result reveals that the tensile strength (TS) and flexural stress (FS) were decreased with increasing fiber contents in the PF-ABS composites except 10% fiber content.
文摘The neodymium complex supported on styrene-maleic anhydride copolymer （SMA·Nd） has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA·Nd polymeric complex is characterized by IR and its catalytic activity, and the polymerization features have been investigated in comparison with that of the conventional Ziegler-Natta catalysts. When [Nd]=1×10<sup>-3</sup> mol/L, [M]=5mol/L, Al/Nd=170（mol ratio） and CCl<sub>4</sub>/Nd=50（mol ratio）, the polymerization conversion of styrene gets to 51.6% in six hours, and the catalytic activity reaches 1852 gPS/gNd, which is much higher than that of conventional rare earth catalysts. The polymerization reaction has an induction period and shows some characteristics of chain polymerization. The polymerization rate is the first order with respect to the concentration of styrene monomer. Addition of FeCl<sub>3</sub> does not suppress the polymerization.
