Comparison of ethylene-propylene copolymers obtained with Ti,V and Zr catalyst systems

Summary Ethylene and propylene were copolymerized in n-heptane in the presence of high activity heterogeneous MgCl₂/TiCl₄ catalyst and homogeneous VOCl₃ and Cp₂ZrCl₂ catalysts to study the effect on the catalyst to the microstructure and molecular weight distribution of the copolymer. The copolymer obtained with the zirconium catalyst was much more random in structure than that obtained with the vanadium and titanium catalysts and the molecular weight distribution was very narrow. Ethylene and propylene were also copolymerized in liquid propylene with MgCl₂/TiCl₄ and VOCl₃ catalyst systems. These copolymers were column fractionated and the fractions were analysed by NMR spectroscopy and DSC. The fractions of the copolymer obtained with the titanium catalyst was found to have broader distribution in composition than the copolymer obtained with the vanadium catalyst. This probably explains the traces of crystallinity in the copolymer prepared with the titanium catalyst. However, no effect was seen on the glass transition temperature.     

Mechanical properties of alternating copolymers of acrylonitrile and butadiene

The alternating copolymer was prepared from butadiene (BD) and acrylonitrile (AN) with ethylaluminum dichloride as a complexing agent and with vanadyl chloride as a catalyst, and was investigated to explain effects of composition and sequence distribution on the physical properties, especially the viscoelastic properties and the ultimate mechanical properties. In the unvulcanized state, the viscoelastic properties of the alternating rubber is not essentially different from the random one, except for a slight difference in the relaxation spectra. However, the vulcanized rubbers show different shift factors. The latter depends upon the glass transition temperature (T_g.) Since the alternating copolymer possesses a T_g lower than the random one, the nature of the alternating copolymer corresponds to that of the random copolymer having an AN content of 40%. The difference in dynamic properties can be expressed with the different shift factors. In the isofree-volume state or at the temperature T_g + 25°C, the rubbers having various acrylonitrile contents and various degrees of alternation exhibit almost the same dynamic properties. However, the strain at break of the alternating rubber is higher than that of the random one. The temperature of maximum strain increases with increasing degree of alternation. The alternating rubber shows higher stress at break than the random one. The stiffness of the chain of the alternating copolymer is smaller than the random copolymer; in other words, the molecular chain of the former is more flexible than the latter. It can be said that the alternating copolymer is an excellent rubber having high tensile strength and elongation at break.     

VO_x/焦磷酸镧催化剂的丙烷氧化脱氢制丙烯催化性能

以嵌段共聚物P188为模板剂制备VO_x/焦磷酸镧催化剂。采用比表面分析仪、透射电镜、X射线光电子能谱和H_2-TPR对催化剂结构进行表征,并评价其丙烷氧化脱氢制丙烯的催化性能。结果表明,焦磷酸镧有一定的催化活性,但催化性能不高。当负载钒氧物种后,VO_x/焦磷酸镧催化剂催化活性有所增加,反应温度600℃时,丙烯产率达16.6%。原因主要是钒氧物种和可移动氧在丙烷氧化脱氢过程中起到重要作用。     

A novel supported salenCrIIICl catalyst for alternating copolymerization of cyclohexene oxide with carbon dioxide

A novel heterogeneous catalyst was prepared by immobilizing salenCr^IIICl on a modified poly (aniline-co-o-aminophenol) (MPOAP). The FT-IR, TEM, XRD, XPS and ICP results indicated that salenCr^IIICl was successfully supported on MPOAP. The resulted catalyst (MPOAP-salenCr^IIICl) exhibited excellent catalytic performance for alternating copolymerization of cyclohexene oxide (CHO) with carbon dioxide (CO₂). Moreover, the supported catalyst had an obvious effect on the microstructures of the copolymerization and the obtained polymer was found to be a linear alternating copolymer with narrower molecular weight distribution. The TG and DTG results indicated that the product prepared by the supported catalyst possessed higher decomposition temperature.     

钒对FCC催化剂脱除噻吩类硫化物性能的影响

催化裂化过程(FCC)中使用催化剂脱硫对生产清洁燃料具有重要意义。文中通过文献调研,阐述了噻吩类硫化物在FCC催化剂上的裂化依赖于B酸和L酸的协同作用原理,指出以L酸碱对化合物修饰FCC催化剂可改善其表面的弱L酸分布,增强催化剂对噻吩类硫化物的选择性吸附能力,提高FCC催化剂脱除噻吩类硫化物性能。氧化钒作为典型的L酸碱对化合物,利用其修饰FCC催化剂可改善裂化催化剂的脱硫活性。鉴于氧化钒对FCC催化剂的活性组分分子筛存在一定的破坏作用,FCC催化剂的载体是较适宜的修饰位置。低价态钒较高价态钒对噻吩有着更强的化学吸附能力,因而采用还原预处理后的催化剂可得到较好的脱硫效果。     

乙烯丙烯酸共聚物型不可逆示温材料的研究

以乙烯丙烯酸共聚物为原料,以低毒性溶剂正庚烷为溶剂,在低温下通过加热和搅拌,制备了环保型低温不可逆示温材料。通过X射线衍射仪测试和分析不可逆示温材料的粒径及结晶规整度。采用差示扫描量热法测定不可逆示温材料的结晶性能和熔点熔限。通过单因素法讨论制备工艺对不可逆示温材料性能的影响。最终确定实验的最佳组成。结果表明,EAA580起始变色温度为82 ℃,变色温度区间为3 ℃,而EAA540起始变色温度为86 ℃,变色温度区间为10 ℃;由EAA580制备的示温贴片具有起始变色温度低、变色温度窄、灵敏度高的特点。     

影响硫酸生产催化剂低温活性的几个因素

研究了用碳化母液制备的低温硫酸催化剂中铯、铷、锂等碱金属元素的助催化作用和熔盐用量对催化剂低温活性的影响。结果表明,铯的低温助催化效果最佳,其用量宜控制在Cs／V＝0.3～0.6。当Cs／V＝0.6时,410℃的ＳＯ_２转化率达42.5%,比无铯催化剂的转化率高9.5%。铷的低温助催化作用比铯低,宜采取措施,适当提高母液的Cs／Rb。在多种碱金属元素混合使用的情况下,锂元素有较好的助催化作用,其最佳用量为Li／Ｖ＝0.4,此时410℃的ＳＯ_２转化率达46%。锂盐的添加顺序对催化剂低温活性亦有一定影响。发现活性组份含量对催化剂低温活性和高温活性影响较大,M／V宜小于4.5。     

Synthesis of poly(vinyl alcohol) derivatives containing amidoxime groups

The modification reaction of poly(vinyl alcohol) (PVAL) with acrylonitrile in alkaline medium was studied. The structure of the resulting polymers was determined by means of IR, ¹H and ¹³C NMR spectroscopy. The influence of solvent composition, catalyst and temperature was evaluated. ¹³C NMR spectroscopy was used for the determination of the sequence distribution of cyanoethylated PVAL (considered as a vinyl alcohol (VAL)-(2-cyanoethyl) vinyl ether (VCE) copolymer). The ¹³C NMR spectra of the methylene carbons in the main chain show three split peaks, the intensities of which change with copolymer composition. These peaks can be assigned to the three dyad sequences. The obtained results show that VCE units have an alternating tendency in the copolymer. Nitrile groups in cyanoethylated PVAL were converted to amidoxime groups by reaction with hydroxylamine. The reaction showed second order kinetics. The activation energy was found to be 51.6 kJ/mol. Soluble polymeric chelates between amidoximated PVAL and cupric ions have been prepared. It is noteworthy that not all the amidoxime groups participate in binding cupric ions.     

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

Ethylene/1-olefin copolymerization using vanadium and titanium complexes bearing tetradentate [O,N,N,O]-type ligand and EtAlCl₂ or MAO as a cocatalyst is carried out. In the presence of the vanadium complex activated with EtAlCl₂ is observed (a) negative “comonomer effect”, (b) high comonomer incorporation and narrow chemical composition distribution (CCD), (c) unexpected copolymer microstructure, and (d) increased molecular weight of copolymers when compared with the homopolymer. In contrast, titanium catalyst gives copolymers with lower 1-olefin content and broad CCD. Supported complexes show higher activity, lower 1-olefins incorporation and give copolymers with ultra high molecular weights.     

用于乙丙橡胶生产的钒醇配体催化剂的制备研究

从乙丙橡胶催化剂需要出发，以含钒浓度高的盐酸溶液为初始水相，高浓度脂肪醇溶液为初始有机相，控制适当游离酸度，采用萃取的方法制备出钒醇配合物的己烷溶液用于乙丙共聚的催化剂，经实验研究其存放稳定性及催化性能均优于工业VOC13催化剂，且制备条件温和、成本低。     

Copolymers of N-vinylcarbazole with monomers containing carboxylic acid groups or carboxylic anhydride groups. II. Photoconductivity and composition

Copolymers of N-vinylcarbazole containing olefinic monomers that possess carboxylic acid or anhydride functionality have been produced. The photoconductive properties of the copolymers were measured. Fluorimetry has been used to relate this photoconductivity to the copolymer composition. Photoconductivity was greatest in copolymers containing high percentages of vinylcarbazole. It is suggested that this is due to block copolymer formation, since the development of such blocks allows greater interchromophore overlap than would be possible with alternating copolymers, which exhibit low photoconductivity.     

Proton conductive reinforced poly(ethylene‐co‐styrene) membranes

Polymers with ionic conductivity are useful materials for ion exchange membranes, separators, and electrolytes in electrochemical cells. New ionomers are currently being sought to replace the ionomers, which contain fluorine and are harmful to environment and expensive. A new and promising ionomer is a sulfonated ethylene/styrene copolymer. A nearby alternating copolymer with styrene content of 47 mol % was polymerized with metallocene/MAO catalyst. Membranes were prepared by hot‐pressing copolymer films with a glassfiber tissue. Phenyl rings in the copolymers were sulfonated with chlorosulfonic acid as a sulfonating agent. As the alternating structure of the copolymer, sulfonic groups were evenly distributed along the membranes. The membranes were characterized by determining water uptake, ion exchange capacity, proton conductivity, and mechanical properties. The studies revealed that the sulfonated copolymers have promising properties for proton‐conducting applications. All membranes had good ion exchange capacity, ～ 3.5 meq/g, and proton conductivity, over 50 mS/cm. Due to the high water uptake of the sulfonated copolymer, mechanical properties of the membranes were improved by using the glassfiber tissue as reinforcement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Facile synthesis of ethylene–propylene fully alternating copolymer and comparison with random copolymer of similar composition

A precisely sequenced ethylene–propylene (EP) fully alternating copolymer was synthesized via trans‐1,4‐polymerization of isoprene catalyzed by Ziegler–Natta catalyst followed by hydrogenation. This EP copolymer was used as model polymer for studying structure–property relationship. An ethylene–propylene random copolymer (ethylene–propylene rubber [EPR]) with similar ethylene content was also prepared for comparison, and the effect of comonomer sequence distribution on properties was investigated. The copolymer chain structures were monitored by ¹H and ¹³C NMR and Fourier translation infrared. Differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, and tensile tests were employed to determine the thermal and mechanical properties. The fully alternating copolymer EP gives a more precise glass transition comparing than EPR. Further understanding on thermal properties and aggregation behavior of ethylene–propylene copolymers is made possible by this comparative study. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45816.     

Liquid crystalline aromatic polyesters containing para-linked dimethylbiphenylene moieties

A series of liquid crystalline aromatic polyesters containing 3,3′-dimethylbiphenyl-4,4′-dicarboxylic acid and 3,4′-dimethyl-biphenyl-4,3′-dicarboxylic acid was prepared by a melt polycondensation procedure and characterized by elemental analysis, DSC and TMA measurements, and optical polarizing microscopy. An optimal composition of the copolymer having a melting temperature around 300°C is proposed and the rheological behavior is discussed. Most of the mechanical properties of this copolymer were found to be close to those of Vectra A950® used as a reference sample. © 1996 John Wiley & Sons, Inc.     

Catalytic Partial Oxidation of Ethane to Acetic Acid over Mo1V0.25Nb0.12Pd0.0005Ox: I. Catalyst Performance and Reaction Mechanism

The oxidation of ethane to acetic acid was studied over the title catalyst at temperatures between 500 and 580 K and elevated pressures between 1.3 and 1.6 MPa. Since water is known to favour acetic acid formation water was considered as an important variable. For a comprehensive characterisation of the catalyst SEM/EDX, TEM/EDX, XRD, XPS, TPD, and TAP were applied. The catalytic experiments revealed a change in reaction mechanism with temperature. While a consecutive reaction scheme dominates at low temperatures with ethylene as intermediate leading to acetic acid, ethylene and acetic acid are mainly formed in parallel at high temperatures. The initial step for both pathways is the reaction of ethane with lattice oxygen; vanadium acts as redox centre. The ethylene formed undergoes a consecutive reaction to acetic acid which can be described as a heterogeneous Wacker-like reaction, where highly dispersed Pd(II) acts as a catalytically active centre. The role of water in this step seems to be similar to that in the homogeneous Wacker reaction of ethylene to acetic acid. The high dispersion of palladium in the present catalyst system maintained under reaction conditions results from the incorporation of small amounts of palladium into a Mo₅O₁₄ like phase serving as host structure also for vanadium and niobium.     

Spontaneous alternating copolymerization of six-membered cyclic phosphonites with lipoic acid

Summary Alternating copolymerizations of six-membered cyclic phosphonites as M_N with lipoic acid as M_E are described. The phosphonites employed were salicylyl phenyl phosphonite (SPO) and 2-phenyl-1,3,2-dioxaphosphorinane (trimethylene phenylphosphonite, TPO). The copolymerization took place without catalyst at 0°C or room temperature. The reaction of SPO with lipoic acid gave alternating copolymer 1, which was formed directly from a genetic zwitterion 4. On the other hand, the reaction of TPO with lipoic acid gave alternating copolymer 2, which was produced after a proton transfer as well as an O-S scrambling giving rise to units 2A and 2B, respectively. Both copolymers 1 and 2 have a lipoic acid component in the main chain.     

柱撑型钒基催化剂的制备及其丙烷氧化脱氢催化性能

以人工合成的3种不同层板组成的层状双羟基金属氢氧化物MgAl-CO₃-LDHs、CoAl-CO₃-LDHs和NiCr-CO₃-LDHs为载体，以偏钒酸钠NaVO₃为柱撑剂和钒前体，采用离子交换法制备了钒柱撑的催化剂样品（MgAlVO、CoAlVO和NiCrVO），通过XRD、FTIR、XPS和Raman等手段表征了样品的物相、钒物种的存在形态以及钒的价态，以丙烷氧化脱氢制丙烯为模型反应，表征了所制备的催化剂样品的催化性能，着重探讨了LDHs载体的层板组成以及钒的含量对催化剂样品中的钒氧物种存在形态及其丙烷氧化脱氢催化性能的影响。结果表明：以20%理论含量的钒柱撑MgAl-CO₃-LDHs所制备的催化剂样品20%MgAlVO对丙烷氧化脱氢反应的催化性能较好，当反应温度为560℃时，丙烯收率可以达到11.3%，Raman光谱显示该催化剂样品中的钒以Mg₃V₂O₈和α-Mg₂V₂O₇两种形式共存，且晶格氧O^2-和吸附氧O^-所占的比例较为均衡，有利于获得较好的丙烷氧化脱氢催化性能，而在同样条件下制备的催化剂样品20%CoAlVO和20%NiCrVO中的钒物种只观察到分别以Co₃V₂O₈和Ni₃V₂O₈存在的正钒酸盐，前者对丙烯的收率不到8%，后者甚至完全得不到丙烯。     

溶剂对rac-Et[Ind]_2ZrCl_2/MMAO催化体系催化乙烯-降冰片烯共聚合的影响

采用乙基桥连二茚基二茚基二氯化锆(rac-Et[Ind]2ZrCl2)/MMAO催化体系催化乙烯/降冰片烯共聚合,比较了甲苯、苯、正己烷、环己烷及其混合溶剂作为反应介质对共聚合活性及共聚物结构的影响。通过差示扫描量热分析(DSC)对共聚产物进行了热力学性质的表征。结果表明,聚合活性和产品的玻璃化转变温度(Tg)在不同溶剂体系中有着显著的差异,在相同聚合条件下,当甲苯/苯体积比为80/20时,聚活活性达到最高,但产品的Tg和降冰片烯的插入率较低。     

新型高性能Ziegler-Natta催化剂用于乙烯淤浆聚合

A novel high performance MgCl2/TiCl4 catalyst with tetrabutyloxsilicane as electron donor was prepared for ethylene slurry polymerization process. The properties of the catalyst such as particle size distribution, catalytic activity, hydrogen responsibility and copolymerization performance were investigated and compared with commercial catalyst (imported catalyst). Copolymerization of ethylene and 1-butylene using the catalyst was stud-ied in a pilot plant. The composition, structure and property of the copolymer were characterized by 13C nuclear magnetic resonance (13C NMR) and gel permeation chromatography-Infrared (GPC-IR), and compared with those of the copolymer obtained from a commercial catalyst. In comparison with the commercial catalyst, the novel cata-lyst had a higher activity (up to 34.6 kg•g－1) and a better particle size distribution (PSD), and produced polymers having higher bulk density (up to 0.37 g•cm－3) with less fine resin. Meanwhile, the novel catalyst showed a higher hydrogen responsibility and better copolymerization performance. The results indicated that the copolymer obtained from the novel catalyst has a higher branch in the high molecular weight fraction and lower branch in the low mo-lecular weight fraction.     

Building of a thermoresponsive cement

A thermoresponsive copolymer solution is used to control the mechanical properties of a cement paste suspension. We use a comb copolymer consisting of a polymethacrylic acid (PMAA) backbone grafted with a polypropylene oxide (PPO) and polyethylene oxide (PEO) copolymer that possesses a low critical solution temperature (LCST). When the temperature crosses the LCST value, microphase separation occurs and the adsorption of the copolymer onto the cement particles is modified. We show that a control of the grafting ratio and of the graft chain composition allows monitoring of the transition temperature as well as the viscosity of the paste in the low and high temperature phases.