Active Catalyst System Research Articles

Reactions of active methylene compounds with 1,3-dienes catalysed by nickel complexes

Reactions of buta-1,3-diene with benzyl methyl ketone, benzyl cyanide, diethyl malonate, and ethyl acetoacetate have been studied in the presence of nickel salts, di-isopropoxyphenylphosphine, and a cocatalyst such as sodium phenoxide. Mixtures of 2 : 1 and 1 : 1 adducts were obtained with the former in predominant quantities. Nickel halides provided the most active catalyst system and the product ratio could be affected by the concentration of reagents and phosphine. Mainly 1 : 1 adduct was obtained on reaction of isoprene with benzyl methyl ketone and exclusive formation of this adduct was found with 2,3-dimethylbutadiene and piperylene. The reaction has been suggested to occur by competing processes involving π-allylnickel and bis-π-allylnickel complexes leading to 1 : 1 and 2 : 1 adducts, respectively. Reactions with diethyl malonate and ethyl acetoacetate require higher amounts of the nickel system which has been demonstrated to be due to complex formation between the catalyst and reagents. The importance of cocatalysts such as sodium phenoxide has been stressed.

Isopropyl Alcohol by Direct Hydration of Propylene

Tokuyama Soda has developed a new process for direct hydration of propylene to isopropanol in liquid phase. This process employs a highly active and selective catalyst system which essentially comprises an aqueous solution of polytungsten compounds within a selective pH range.The first commercial plant, having a capacity of 30, 000 metric tons of isopropanol per annum, has been successfully in operation since the beginning of June 1972 at Tokuyama Soda Co., Ltd.The features of the process are simpleness, low value for propylene consumption and freedom from environmental pollution problems. These advantages make Tokuyama Process by far more economical than the conventional process for the manufacture of isopropanol.

Double‐bond isomerization and hydrogenation in polyethylene with soluble nickel catalysts

AbstractPolyethylene exhibits an increase in melt viscosity (melt index drop‐off) when subjected to extreme thermal treatment. Although stabilizers and antioxidants do not prevent this change it has been possible to stabilize high‐density polyethylene by isomerization or hydrogenation of the polymer unsaturation. A soluble nickel octoate–triethylauminum complex was an active catalyst system for these reactions. A triethyl‐aluminum/nickel ratio of three appeared optimum for maximum activity. Of particular interest regarding this catalyst system was the fact that the terminal vinyl unsaturation of the polymer had to be isomerized to some internal position before hydrogenation commenced. However, when this catalyst system was impregnated on a predried silica or when butyllithium was substituted for triethylaluminum, both isomerization and hydrogenation occurred simultaneously. The addition of a light olefin such as ethylene to the reaction mixture slowed the overall reaction until most of the ethylene had been hydrogenated. At this point the isomerization–hydrogenation reaction path previously mentioned commenced.

Polymerization of epoxides with dialkylaluminum acetylacetonate catalyst systems

AbstractCatalyst systems for the polymerization of epichlorohydrin, propylene oxide, and allyl glycidyl ether have been prepared from pure, separately synthesized dialkylaluminum acetylacetonates (R2Alacac). Adding small amounts of water to R2Alacac gives a catalyst system with enhanced activity. An even more active catalyst system for yielding high molecular weight, epichlorohydrin‐containing polymers is obtained when another organometallic compound is added to the R2Alacac‐0.5 water components. The R2Alacac‐0.5 water‐R2Zn system has been studied in detail. Variation in the molar proportion of water and structural changes in the chelate structure of the R2Alacac component have been examined. Results indicate that the bis‐chelate structure, acac(R)‐Al‐O‐Al(R)acac, plays a major role in catalyst formation. A bimetallic catalyst species containing aluminum and zinc atoms is proposed, with zinc functioning primarily in monomer coordianation and with aluminum involved primarily in polymer chain growth.

Mixed Catalyst Systems for Reactions of Cotton with Dimethylolethyleneurea or Dimethyloldihydroxyethyleneurea

Substituted acetic acids or dibasic acids in combination with MgCl2 are active catalyst systems for the reaction between cotton and dimethylolethyleneurea (DMEU) or dimethyloldihydroxyethyteneurea (DMDHEU) at cure temperatures from 105-125°C. The reaction is primarily influenced by hydrogen ion concentration of the pad bath. Based on condi tioned wrinkle recovery of treated facrics, the order of increasing activity among the substituted acetic acid-Mgcl2 catalyst systems at 115°C in promoting the reaction of cotton with DMDHEU is as follows: acetic ≤ diethylaminoacetic < methylaminoacetic ≤ aminoacetic ≤ thiohydroxyacetic ≤ cyanoacetic ≤ hydroxyacetic acid. The order for the cotton-DMEU reaction is as follows: diethylaminoacetic ≤ acetic ≤ methylaminoacetic ≤ thiohydroxyacetic < hy droxyacetic ≤ aminoacetic ≤ cyanoacetic. Dibasic acids used with MgCl2 in the cellulose-DMEU reaction were more effective than either alone in increasing the amounts of bound nitrogen and formaldehyde and the wet recovery angles of the finished cottons. With DMDHEU, only the succinic acid-MgCl2 combination resulted in an increase in bound nitrogen over that observed with either catalyst used individually. With acids used singly or in combination with MgCl2, the pH of the pad bath was a primary factor in im proving wrinkle recovery with both DMEU and DMDHEU.

Asymmetric‐induction polymerization of β‐vinylacrylates

AbstractOptically active polymers of methyl, ethyl, n‐butyl, and tert‐butyl β‐vinylacrylates were synthesized by using optically active catalyst systems such as n‐BuLi/sodium l‐menthoxide and n‐BuLi/sodium d‐bornoxide. The optically active alkoxides were found to be even more efficient cocatalysts for the asymmetric‐induced polymerization than were the corresponding ethers.The polymers obtained were characterized from their optical rotatory dispersion curves and infrared absorption spectra.

Some aspects of the mechanism of the stereospecific polymerization of α-olefins

Abstract

Polyethers. XI. Polymerization ofDL‐propylene oxide with optically active catalyst systems

AbstractThe polymerizations ofL‐propylene oxide by aluminum isopropoxide–zinc chloride, ferric chloride–propylene oxide, and diethylzinc–water catalysts have been studied further and analyzed in terms of the source of stereocontrol in producing isotactic crystalline polymer. The polymerization ofDL‐propylene oxide by optically active complexes of the above catalysts with poly(L‐propylene oxide) and with a catalyst formed from triisobutylaluminum andL‐propylene glycol failed to produce any evidence for stereopreference by the catalysts for theL‐ orD‐molecules.

Separated aluminum alkyl–titanium tetrachloride catalysts for isoprene polymerization

AbstractThe liquid portions of triisobutyl–aluminum TiCl4 catalysts were partially or completely removed from catalysts formed at Al/Ti ratios of 0.5, 0.6, 1.0, 1.2, 2.0, 3.0, and higher. The partially separated catalysts (0.5–1.2 Al/Ti) are still highly active for the polymerization of isoprene to a high cis polymer. The completely separated solid is inactive, but regains polymerization activity if triisobutyl aluminum or diisobutyl‐aluminum chloride is added back. Polymer yield quickly reaches a maximum and then falls off sharply on addback of more trialkyl; the drop in yield is much slower on addback of excess dialkyl halide. The results indicate that trialkyl or dialkyl halide plus β‐TiCl3 make active catalyst systems for cis‐polyisoprene; the alkyl dihalide is not satisfactory. Excess trialkyl changes the solid surface or mechanism and results in lowered solid polymer yield and increased oily oligomer formation. Completely separated high ratio (2.0 and 3.0 Al/Ti) catalysts are more active than those only partially separated but still much less active than catalysts formed at lower ratios. Addbacks of either aluminum trialkyl or dialkyl halide depress the solid cis polymer yield. Without any separation no solid polymer at all forms. The results suggest that the catalyst at these high ratios is a solid complex of β‐TiCl3 with an organometallic. A simple coordination mechanism is sufficient to correlate all the experimental results.

The polymerization of propylene using an optically active catalyst system

The incorporation of the first monomer unit in a growing chain of isotactic polypropylene affords an asymmetric carbon atom, and the orientation of subsequent monomer units has been explained on the basis of asymmetric induction. This hypothesis has now been tested by carrying out the polymerization of propylene in the presence of an optically active trialkylaluminium and α-titanium trichloride. The absence of optical activity in the resulting polymer, and in the products of its pyrolysis, would appear to disprove the above hypothesis. Polymerizations carried out in an optically active medium also failed to produce an optically active polypropylene.