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The capabilities of crystallization and extraction methods for separation of vanillin and syringaldehyde are described. Crystallization methods are based on differences in solubility of aldehydes ammonia derivatives in water, and solubility of their potassium salts in concentrated aqueous solutions of potassium carbonate. Temperature dependencies of solubility of potassium vanillate and potassium syringate in aqueous solutions containing 300–500 g/l of potassium carbonate are presented. The crystallization methods give separation factors of ca. 50 and allow to isolate syringaldehyde from its mixture with vanillin by one-stage crystallization with yield over 95% and purity over 98%. Extraction methods have lower separation factors of 2−2.5.

The main problem with cast austenitic—ferritic duplex stainless steels is the formation of cracks after the solidification. The crack sensitivity is caused by volume differences between the microstructural components and coupled to an extreme embrittlement. Therefore the σ phase precipitation becomes important. It binds Fe, Cr and Mo and degrades the corrosion resistance. In addition, it decreases the toughness of the steel because of its embrittling character and by precipitating at grain boundaries. Both the absolute amount of σ phase and its distribution have an influence. During casting of components, the σ phase precipitation should be kept as low as possible. This is achieved by rapid cooling through the critical temperature range from 1000 to 600°C. Since the main cause of crack formation lies in microstructural stresses and incompatibilities, this process must be better understood. Neutron time-of-flight diffractometry can detect strains in different phases simultaneously from the same vo...

The influence of catalyst (CuSO4 solution), pH and temperature on the vanillin formation and oxygen consumption in oxidation of lignin in alkaline media have been studied. It was shown that the main role of catalyst in the lignin oxidation is to change the selectivity of hydroperoxide fragmentation rather than to accelerate oxidation.

The oxidation of a number of lignin species by molecular oxygen was studied. The selectivity of the process was found to be close to that of the oxidation with nitrobenzene. The influence of lignin origin on the yields of vanillin and syringaldehyde as well as the correlation between the rates of wood delignification and the aldehydes formation are discussed.

The Ni(PPh3)n-Et3Al2Al3 catalytic system was found to be most effective for the dimerization of ethylene and propylene when the ligands Bu3PO and (BuO)2-PNEt2 were used in the Ni complex. For propylene dimerization in the liquid phase, the yield was 54 kmole/mole Ni-h at 40–55‡C. Using mathematical planning methods for the experiments the optimum conditions range for the formation of hexanes was found, in which selectivity for dimerization reached 85–96% at 80–90% conversion.

Ni(0), Ni(I), and Ni(II) complexes, differing in the ligand environment of the central atom, bring about di-, tri-, and oligomerization of spiro[2,3]-hex-1-ene (SH). The most efficient catalyst for the [2+2]-cyclodimerization of SH is NiBr(PPh3)3, which gives virtually a single product, the SH cyclo dimer. It has been found that high conversion and selectivity in the [2+2]-cyclodimerization of SH is achieved by using organoaluminum compounds as catalysts.

1. It has been shown that in the presence of (η2-methylenecyclopropane)bis(triphenyl-phosphine) nickel (Kt-1) and of a series of triphenylphosphine Ni(O) complexes the catalytic conversion of methylenecyclopropane (MCP) proceeds with the formation of identical di- and trimerization products. It is postulated that the mechanism of di- and trimerization of MCP on all Ni(O) phosphine complexes is similar, with the formation of Kt-1 as a general intermediate. 2. Complexes of Ni(I) and Ni(II) which have been studied were found to be inactive in MCP conversion.

The oxidative addition of 3,3-dimethylcyclopropene (DMCP) to the nickel complexes (Ph3P)3Ni and (π-C2H4)Ni(PPh3)2 resulting in the formation of bis(triphenylphosphine)-5-nickela-3,3,7,7-tetramethyl-trans-tricyclo[4.1.0.02,4]heptane has been carried out. The NMR (1H and 31P-{1H}) spectra, the reactivity and some of the catalytic properties of this complex in the cyclodimerization of DMCP have been studied.

Two methods for preparing π-methylenecyclopropanebis(triphenylphosphine)-nickel are described: (1) the substitution of the ethylene ligand in π-ethylenebis(triphenylphosphine)nickel by methylenecyclopropane; (2) the interaction of Ni(acac)2 with diethylaluminium ethoxide in the presence of methylenecyclopropane and triphenylphosphine. The reactivity, some catalytic properties and the NMR (1H and 31P-{1}) spectra of the nickel-olefin complex obtained have been studied.

1. In the presence of (η2-methylenecyclopropane)bis(triphenylphosphine)nickel (Kt-1), methylcyclopropane (MCP) undergoes dimerization, trirmerization, and oligomerization, the formation, of trimers being predominant. In catalytic conversions of MCP under the influence of Kt-1, we have found for the first time in the composition of the dimers 2-methyl-4-methylene-1,5-hexadiene. It has been established that this dimer is also formed in the case of the catalytic system Ni(COD)2-PPh3. 2. Dimers and trimers of MCP that are formed, containing diene fragments, are the principal predecessors of higher oligomers. Conditions have been found for reducing the yield of oligomers from 45–56% to 4–6%, thus increasing the selectivity of the process in the direction of monoolefins and triolefins with cyclopropyl substituents

1. The formation of (η2-methylenecyclopropane)bis(triphenylphosphine)nickel was established in the reaction of methylenecyclopropane (MCP) with Ni(PPh3)3, Ni(PPh3)4, and the catalyst (Cat) obtained by the reduction of NiCl2·6H2O by sodium borohydride in the presence of PPh3. 2. 31P-{1H} NMR spectroscopy was used to determine that the catalyst was composed of Ni(PPh3)3, Ni(PPh3)4, and, probably, Ni(PPh3)2. 3. Interconversions of the catalyst and (η2-methylenecyclopropane)bis(triphenylphosphine)nickel were determined during the transformations of MCP, which supports the scheme for the catalytic cycle of MCP reactions by the action of Ni(O) triphenylphosphine complexes.

1. The methods of IR spectroscopy have been used to show that at least three complexes; Ni(CO)2PPh3L (with L=PPh3, Al2O3) and Ni(CO)3PPh3, result from formation of a complex catalyst through stepwise ligand interchange between nickel triphenylphosphine and nickel tetracarbonyl on a carrier surface. 2. Codimerization of ethylene and propylene in liquified propylene containing the heterogenized trichlorotriethyldialuminum-activated catalyst gives high product yields with a 40% selectivity for amylene formation.