Supported Propylene Polymerization Catalyst

Abstract

Since the development of supported propylene polymerization catalysts, a great deal of information has appeared in the patent literature. A detailed summary of the patents granted up to 1981 was reported by Ray and his associates [28], and a general review of historical development of both supported and unsupported catalysts for propylene polymerization was given by Pino and Mulhaupt [22]. Unfortunately, the same cannot be said about the scientific literature. Investigations into the fundamentals of this type of polymerization are still at the pioneer stage. However, from the limited number of scientific publications available, some consensus has emerged regarding certain basic features of this polymerization system. In this paper the characteristics of the supported catalysts of propylene polymerization and its kinetics are reviewed.     

POLYMERIZATION OF ETHYLENE AND PROPYLENE WITH VCL4-BUTYLLITHIUM CATALYSTS

Polymerization of ethylene and propylene with VCl₄-BuLi (Bu = n-Bu, sec-Bu, tert-Bu) catalysts was investigated. The VCl₄-BuLi catalysts were found to initiate the polymerization of ethylene and propylene. The VCl₄-BuLi catalysts gave an ultra high molecular polyethylene. The effect of the Li /V mole ratio on the polymerization of ethylene with the VCl₄-BuLi catalysts was observed, an the catalyst gave an optimum rate at the Li/V ratio of about 3.0. The polyethylene obtained with the VCl₄-BuLi catalyst was found to be a linear structure. In the polymerization of propylene with the VCl₄-BuLi catalyst, the polymers contain mm contents of 56–66% were produced.     

Direct Oxidation of Propylene with Molecular Oxygen Over Ti-Modified Sulfated Zirconia Catalyst, 2. In Situ Diffuse Reflectance FT-IR Study

During the reaction of propylene with O₂, in situ Diffuse Reflectance FT-IR measurements were performed over Ti-modified SZ and SZ catalysts. Without O₂, the main bands characteristic of (branched) hydrocarbons, formed by oligomerization leading to, finally, carbonaceous residue, appeared within the range of 3900-2750 cm^-1, which was affected by the bands of surface OH groups. Investigation of these IR bands showed the role of molecular oxygen not only to limit the formation of carbonaceous species on the catalyst surface, but also to form oxygenates and these findings were in good agreement with the results of catalytic reaction.     

Reactivity of RuO species in RuO2/CeO2 catalysts prepared by a wet reduction method

The paper deals with the reactivity of RuO₂/CeO₂ prepared by a wet reduction method: ruthenium was supported on Ce(OH)₃, which was precipitated by alkali-hydrolysis of Ce(NO₃)₃, under a reduction condition with formaldehyde at pH 11 and transformed into RuO₂/CeO₂ catalysts by calcination in air at 773 K. The catalysts were investigated with an ESR technique and were tested for oxidation of propylene. They had no ESR signals by themselves at room temperature, but gave two sets of anisotropic signals upon contact with propylene. These signals were derived from the reaction products between RuO and propylene. The intensities of the signals were kept unchanged at room temperature for more than 1 h in the absence of excess propylene. The signals decayed in the presence of excess propylene and the upfield signal decayed more rapidly. A prior heating of the catalyst in air at 473 K or above caused the increase in the intensity of the upfield signal. The time course of the signal changes discriminated between ethylene and olefins with allylic hydrogen toward RuO species.     

Catalytic conversion of lactic acid into propylene glycol over various metals supported on silica

Catalytic hydrogenation of lactic acid to propylene glycol was performed over various metals (Ag, Co, Cu, Ni, Pt, and Ru) supported on silica prepared by an incipient wetness impregnation method. The loading amount of each metal was 5 wt%. Crystallinity of the synthesized catalysts was investigated by X-ray diffraction (XRD), and the BET method was utilized to examine the surface area. Pore volume and pore size of catalysts were determined using BJH analysis of the N₂ adsorption isotherm. Particle sizes of various metals were determined from transmission electron microscopy (TEM) images. The catalytic activity was found to be strongly dependent on the supported metal. Among catalysts tested, Ru/SiO₂ showed the highest propylene glycol yield. The yield of propylene glycol increased with pressure, and the highest yield was achieved at 130 °C.     

Preparation of elastomeric polypropylene using metallocene catalysts: Catalyst design criteria and mechanisms for propagation

A series of unsymmetrical metallocene catalysts were prepared and used to polymerize propylene under a variety of conditions using methylaluminoxane as a cocatalyst. Zirconium and hafnium-based catalysts were more active and more importantly, much more stable at conventional polymerization temperatures than titanium catalysts. By adjusting experimental conditions, it is possible to vary both the molecular weight of the polymer and also the degree of crystallinity. These properties significantly impact on the tensile properties of elastomeric poly(propylene) (ELPP) in a predictable manner. The microstructure of ELPP was characterized by ¹³C NMR spectroscopy and the pentad distributions were analyzed using several statistical models for propagation. This work has demonstrated that the microstructure of ELPP is probably not that of an isotactic-atactic block copolymer.     

Effects of Various Amounts of New Hepta-Ether as the Internal Donor on the Polymerization of Propylene with and without the External Donor

The new hepta-ether compound as the internal donor was synthesized using the Williamson reaction of dipentaerythritol with sodium hydride as the strong base and iodomethane as the alkyl halide. The hepta-ether compound was characterized by NMR, FTIR, and GC techniques. The MgCl₂-supported catalysts incorporated with different amounts of hepta-ether compound as the internal donor and without the internal donor were synthesized and characterized. The propylene polymerization was carried out using these catalysts in the presence of triethylaluminum as a co-catalyst and hydrogen as a chain transfer agent, with and without the external donor. The effect of a new internal donor on propylene polymerization using prepared MgCl₂-supported Ziegler-Natta catalysts was investigated.     

Reduction of NO2 in Flue Gas by CO and Propylene over CuO‐CeO2/SiO2 in the Presence of O2

Catalytic reduction of NO₂ with CO and/or propylene in the presence of NO and excess oxygen, a model mixture for flue gas, was studied over a series of CuO‐CeO₂/SiO₂ catalysts between 120–260 °C. The effect of HCl, an impurity in flue gas, on the activity of the catalysts was evaluated. It was found that a binary oxide catalyst, 2% CuO‐8% CeO₂/SiO₂, was active for the reduction of NO₂ by CO and/or propylene. CO was effective for selective reduction of NO₂ in the presence of NO and O₂ in a temperature window between 160–200 °C while propylene was effective at temperature higher than 200 °C. In the presence of HCl, the activity of the catalyst for reduction of NO₂ with CO was irreversibly deactivated. However, the activity for reduction of NO₂ with propylene was not influenced by HCl.     

Isomerization of 3,3-dimethyl-1-butene over aluminum and chromium orthophosphates

The skeletal isomerization of 3,3-dimethyl-1-butene over AlPO₄ (Al/P=1), CrPO₄ (Cr/P=1), and CrPO₄−AlPO₄ (CrAlP, 5–10 wt.% AlPO₄) catalysts is a first order reaction. Catalytic performance is affected by the precipitation agent. CrPO₄ catalysts obtained in propylene oxide-aqueous ammonia showed the highest activity. Moreover, the incorporation of AlPO₄ to CrPO₄ developed CrAlP catalysts that exhibited increased activity, irrespective of the precipitation method, as compared with both AlPO₄ and CrPO₄ catalysts. Besides, CrAlP catalysts prepared in propylene oxide-aqueous ammonia were the more active ones.     

Copolymerization of ethylene and propylene catalyzed by magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts

Magnesium chloride supported vanadium/titanium bimetallic Ziegler-Natta catalysts with di-i-butyl phthalate as internal donor for copolymerization of ethylene and propylene were prepared.The effects of reaction temperature, ethylene/propylene molar ratio,aluminium/vanadium（Al/V）molar ratio and titanium/vanadium molar ratio on the catalytic activity were investigated.The molecular weight,molecular weight distribution,sequence composition and crystallinity of the products were measured by gel permeation chromatography,¹³C-NMR and differential scanning calorimetry analysis, respectively.In comparison to the vanadium and titanium catalysts,the bimetallic catalyst showed higher catalytic activity and better copolymerization performance.The obtained ethylene/propylene copolymers have high molecular weight （10⁵）,broad molecular weight distribution,high propylene content with random or short blocked sequence structures （r_Er_P=1.919）,low melting temperatures and low crystallinities（X_c<20%）.     

Propylene polymerization with catalysts containing divalent titanium

The behavior in propylene polymerization of divalent titanium compounds of type [η⁶-areneTiAl₂Cl₈], both as such and supported on activated MgCl₂, has been studied and compared to that of the simple catalyst MgCl₂/TiCl₄. Triethylaluminium was used as cocatalyst. The Ti–arene complexes were active both in the presence and in the absence of hydrogen, in contrast to earlier reports that divalent titanium species are active for ethylene but not for propylene polymerization. ¹³C-NMR analysis of low molecular weight polymer fractions indicated that the hydrogen activation effect observed for the MgCl₂-supported catalysts should be ascribed to reactivation of 2,1-inserted (“dormant”) sites via chain transfer, rather than to (re)generation of active trivalent Ti via oxidative addition of hydrogen to divalent species. Decay in activity during polymerization was observed with both catalysts, indicating that for MgCl₂/TiCl₄ catalysts decay is not necessarily due to overreduction of Ti to the divalent state during polymerization. In ethylene polymerization both catalysts exhibited an acceleration rather than a decay profile. It is suggested that the observed decay in activity during propylene polymerization may be due to the formation of clustered species that are too hindered for propylene but that allow ethylene polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2645–2652, 1997     

原子层沉积构筑Pd/TiO2限域催化剂及其在1,4-丁炔二醇加氢的应用

利用ALD制备了TiO₂限域的Pd催化剂, 研究了限域空间内Pd纳米颗粒与TiO₂的界面作用对1,4-丁炔二醇(BYD)加氢性能的影响. 相比于管外负载型催化剂, 限域催化剂在催化1,4-丁炔二醇选择性加氢反应中体现出非常高的催化活性和1,4-丁烯二醇的选择性. HR-TEM、 EDX-Mapping、 XRD、 XPS和H₂-TPR表征说明, 限域体系中Pd-TiO₂的界面相互作用强于传统TiO₂表面负载型Pd催化剂, 这种强界面作用不仅能够提高BYD的加氢活性, 也可抑制半加氢产物1,4-丁烯二醇的异构化和深度加氢, 提高1,4-丁烯二醇的选择性, 而且限域结构也可阻止管内壁Pd纳米颗粒的脱落, 提高催化剂的稳定性.     

Preparation of phosphorus-modified PITQ-13 catalysts and their performance in 1-butene catalytic cracking

A series of phosphorus-modified PITQ-13 catalysts was prepared by wet impregnation of NH₄H₂PO₄ solution into an HITQ-13 parent. The catalysts were characterized using XRD, N₂ adsorption, MAS NMR and NH₃-TPD. Their catalytic performance in 1-butene catalytic cracking was evaluated in a fixed fluidized bed reactor. The results showed that the crystallinity, surface area and pore volume of P-modified PITQ-13 catalysts decreased with the increasing amounts of P. The number of weak acid sites increased, whereas that of strong acidity decreased. The selectivity to propylene in 1-butene cracking reactions increased because of the decrease in strong acidity. The yield of propylene achieved 41.6% over PITQ-13-2 catalyst with a P content of 1.0 wt%, which was 5.1% greater than that achieved over HITQ-13 catalyst.     

Chloride‐Induced Highly Active Au Catalyst for Methyl Esterification of Alcohols

Chloride is generally regarded as a harmful species for the heterogeneous catalysts, especially Au catalysts. In this work, a series of active Au/NiO_x catalysts were successfully prepared with co‐precipitation method by tracking the concentrations of chloride in the re‐dispersed aqueous solutions. For methyl esterification of alcohols, the highest active Au/NiO_x catalysts could be prepared from aqueous solutions containing 8‐13 ppm chloride, the yield of methyl benzoate of catalyst Au/NiO_x‐9 was 99%. The catalyst structures and the role of chloride in catalysts were explored by ICP, BET, XPS, TEM and EXAFS characterizations. It was found that the appropriate amount of residual chloride in Au catalysts was beneficial to their catalytic activities. Especially for Au/NiO_x‐9, the appropriate amount of residual chloride had positive effects on the physicochemical properties of Au/NiO_x catalyst, the position of Au nanoparticles (NPs) located on NiO_x crystallites and the ratio of Au^δ+/Au⁰ in catalyst, which together resulted in its high reactivity.     

Kinetics of propylene and ethylene polymerization reactions with heterogeneous ziegler-natta catalysts: Recent results

The article discusses recent results of kinetic analysis of propylene and ethylene polymerization reactions with several types of Ti-based catalysts. All these catalysts, after activation with organoaluminum cocatalysts, contain from two to four types of highly isospecific centers (which produce the bulk of the crystalline fraction of polypropylene) as well as several centers of reduced isospecificity. The following subjects are discussed: the distribution of active centers with respect to isospecificity, the effect of hydrogen on polymerization rates of propylene and ethylene, and similarities and differences between active centers in propylene and ethylene polymerization reactions over the same catalysts. Ti-based catalysts contain two families of active centers. The centers of the first family are capable of polymerizing and copolymerizing all α-olefins and ethylene. The centers of the second family efficiently polymerize only ethylene. Differences in the kinetic effects of hydrogen and α-olefins on polymerization reactions of ethylene and propylene can be rationalized using a single assumption that active centers with alkyl groups containing methyl groups in the β-position with respect to the Ti atom, Ti-CH(CH₃)R, are unusually unreactive in olefin insertion reactions. In the case of ethylene polymerization reactions, such an alkyl group is the ethyl group (in the Ti-C₂H₅ moiety) and, in the case of propylene polymerization reactions, it is predominantly the isopropyl group in the Ti-CH(CH₃)₂ moiety. Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 11, pp. 1911–1934. The text was submitted by the authors in English.     

Crystal‐Plane‐Controlled Selectivity of Cu2O Catalysts in Propylene Oxidation with Molecular Oxygen

The selective oxidation of propylene with O₂ to propylene oxide and acrolein is of great interest and importance. We report the crystal‐plane‐controlled selectivity of uniform capping‐ligand‐free Cu₂O octahedra, cubes, and rhombic dodecahedra in catalyzing propylene oxidation with O₂: Cu₂O octahedra exposing {111} crystal planes are most selective for acrolein; Cu₂O cubes exposing {100} crystal planes are most selective for CO₂; Cu₂O rhombic dodecahedra exposing {110} crystal planes are most selective for propylene oxide. One‐coordinated Cu on Cu₂O(111), three‐coordinated O on Cu₂O(110), and two‐coordinated O on Cu₂O(100) were identified as the catalytically active sites for the production of acrolein, propylene oxide, and CO₂, respectively. These results reveal that crystal‐plane engineering of oxide catalysts could be a useful strategy for developing selective catalysts and for gaining fundamental understanding of complex heterogeneous catalytic reactions at the molecular level.     

Catalytic cracking of C<Subscript>5</Subscript> raffinate to light olefins over NaOH-treated ZSM-5

A series of ZSM-5 catalysts (ZSM-5 (X)) treated with different NaOH concentration (X = 0, 0.05, 0.1, and 0.2 M) were prepared for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C₅ raffinate. The effect of NaOH concentration on their physicochemical properties and catalytic activity was investigated. It was found that textural and physicochemical properties of ZSM-5 (X) catalysts were strongly influenced by the NaOH concentration. Mesopore volume of ZSM-5 (X) catalysts increased with increasing NaOH concentration, while acidity of the catalysts decreased with increasing NaOH concentration. Conversion of C₅ raffinate and yield for light olefins (ethylene and propylene) showed the volcano-shaped curves with respect to NaOH concentration (X). This implies that NaOH treatment of ZSM-5 was an efficient method to produce light olefins through catalytic cracking C₅ raffinate, and that optimal NaOH concentration was required for maximum production of light olefins. Among the catalysts tested, ZSM-5 (0.05) catalyst showed the best catalytic performance due to its favorable porosity and acidity.     

Homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide with metal salts of acetic acid

The homopolymerization of propylene oxide was first conducted at 80°C in the absence of any solvent by using various metal salts of acetic acid and it was found that Mg(OAc)₂, Cr(OAc)₃, Mn(OAc)₂, Co(OAc)₂, Ni(OAc)₂, Zn(OAc)₂, and Sn(OAc)₂ were effective for the polymerization. The copolymerization of propylene oxide and carbon dioxide was next examined by using these effective metal salts of acetic acid as catalysts. Most of these were effective also for the copolymerization. The nature of the polymer obtained was strongly dependent on the catalyst used. Co(OAc)₂ and Zn(OAc)₂ gave an alternate copolymer of propylene oxide and carbon dioxide, Mg(OAc)₂, Cr(OAc)₃, and Ni(OAc)₂ gave a random copolymer, while Sn(OAc)₂ gave a homopolymer of propylene oxide. Then the copolymerization of propylene oxide and carbon dioxide was kinetically investigated in some detail by using Co(OAc)₂ as a catalyst. On the basis of the results obtained, a plausible mechanism was proposed for both the homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide.     

Influence of support recrystallization techniques on catalyst performance in olefin polymerization

This paper is a comparative study of the performance of TiCl₄ catalysts supported on recrystallized MgCl₂ through different techniques for the polymerization of ethylene, propylene and ethylene-propylene copolymers. MgCl₂ was dissolved in 1-hexanol and recrystallized through solvent evaporation, quick cooling and precipitation with SiCl₄. The effect of the recrystallization conditions during the catalyst preparation on the chemical composition of catalysts was discussed with the help of IR spectroscopy. The variations of dealcoholation levels due to the different recrystallization techniques highly influenced the catalytic activity. The catalyst obtained through SiCl₄ recrystallization was not only the most active, but it also showed the highest isotacticity indexes for propylene polymerization.     

Some aspects of the bimetallic μ-oxo-alkoxides for polymerizing epoxides to polyether elastomers

The bimetallic catalysts of Osgan and Teyssie, (RO)₂Al-O-Zn-O-Al(OR)₂, are effective, unusual catalysts for polymerizing epoxides. The polymer obtained from propylene oxide when R = n-Bu is preponderantly isotactic and highly crystalline and thus, largely head-to-tail. Crystallizable, sulfur vulcanizable propylene oxide rubber was made by copolymerizing propylene oxide (PO) with allyl glycidyl ether (AGE) with this catalyst. This product after S vulcanization exhibited gum tensile and other properties which were superior to the commercially available, amorphous PO–AGE copolymer of similar composition. However, the Osgan–Teyssie catalyst is very sensitive to reactive, polar impurities. Hindered alkyl aluminums and especially alkoxides such as Et₂AlOtert–Bu can be added to help alleviate this problem. The reported favorable (but slow) copolymerization of epichlorohydrin with propylene oxide in nonpolar media with the Osgan–Teyssie catalyst has been confirmed and an alternate explanation for this unusual result suggested.