Calcium catalyzed enantioselective intramolecular alkene hydroamination with chiral C2-symmetric bis-amide ligands

Enantioselective catalysis with calcium catalysts is challenging due to facile loss of the chiral spectator ligand. Herein a series of bis-amide calcium catalysts with chiral binaphtalene bridges is introduced.

Effect of catalyst on tail gas during reduction of vanadium-titanium magnetite carbon-containing pellet

Catalyst can enhance the reduction effect and promote the reduction of vanadium titanomagnetite. In this paper, the carbon-containing pellets of vanadium titanomagnetite were prepared by using highly volatile coal as the reducing agent under the background of a novel process of pre-reduction in the rotary kiln. The effects of CaO, CaCO3, B2O3 and borax (Na2B4O7·10H2O) on the tail gas characteristics of carbon-containing pellets in the prereduction process were studied by using a simulated rotary kiln and flue gas analyzer. The results showed that the enhanced reduction effect of boron catalysts was slightly stronger than that of calcium catalysts, among which CaO catalyzed the least and borax the best. With the increase of metallization rate, the CO utilization in the tail gas is generally reduced, while when using CaCO3 as the catalyst, the CO utilization is significantly increased. Due to different reduction mechanism, the boron catalysts have little effect on the tail gas, and the calcium catalysts have a great effect on the tail gas. Based on the experimental results and the characteristics of the tail gas from the reduction process, we put forward the idea of using CaCO3 as the best catalyst and using CaO to absorb CO2 in the tail gas to form CaCO3.

OPERATING SPECIFICATIONS OF CATALYTIC CLEANING OF GAS FROM BIOMASS GASIFICATION

The paper focuses on the theoretical description of the cleaning of syngas from biomass and waste gasification using catalytic methods, and on the verification of the theory through experiments. The main obstruction to using syngas from fluid gasification of organic matter is the presence of various high-boiling point hydrocarbons (i.e., tar) in the gas. The elimination of tar from the gas is a key factor in subsequent use of the gas in other technologies for cogeneration of electrical energy and heat. The application of a natural or artificial catalyst for catalytic destruction of tar is one of the methods of secondary elimination of tar from syngas. In our experiments, we used a natural catalyst (dolomite or calcium magnesium carbonate) from Horní Lánov with great mechanical and catalytic properties, suitable for our purposes. The advantages of natural catalysts in contrast to artificial catalysts include their availability, low purchase prices and higher resilience to the so-called catalyst poison. Natural calcium catalysts may also capture undesired compounds of sulphure and chlorine. Our paper presents a theoretical description and analysis of catalytic destruction of tar into combustible gas components, and of the impact of dolomite calcination on its efficiency. The efficiency of the technology is verified in laboratories. The facility used for verification was a 150 kW pilot gasification unit with a laboratory catalytic filter. The efficiency of tar elimination reached 99.5%, the tar concentration complied with limits for use of the gas in combustion engines, and the tar content reached approximately 35 mg/m_n³. The results of the measurements conducted in laboratories helped us design a pilot technology for catalytic gas cleaning.

Ring-opening polymerization of rac-lactide and ε-caprolactone using zinc and calcium salicylaldiminato complexes

Tridentate Schiff base complexes of zinc and calcium were prepared and tested in the ring-opening polymerization of ε-caprolactone and rac-lactide to generate biodegradable polymeric materials from biocompatible metals. Alteration of the pendant donor arm attached to the imine backbone provides some control over catalyst composition and polymerization activity. Complexes of the formula [ONN]ZnN(SiMe3)2, where [ONN] = 2-(N-donor arm-imine)[4,6-di(tert-butyl)phenoxide], were isolated with ethyldimethylamine, ethylpiperidine, and ethylmorpholine substituents, while disproportionation led to the isolation of [ONN]2Zn complexes with methylpyridine, quinoline, and ethyldiisopropylamine derivatives, two of which were crystallographically characterized. Calcium complexes were more stable and novel [ONN]CaN(SiMe3)2 complexes with ethylpiperidine and ethyldiisopropylamine substituents were reported. Zinc and calcium catalysts coordinated to a single tridentate ligand were effective at initiating the polymerization of ε-caprolactone, but did not control the polymerizations, whereas the bis(ligand) complexes produced no polymer. These catalysts were effective at controlling the polymerization of rac-lactide. Coordinatively saturated complexes inhibit the polymerization, while initiation from either the amido or ligand alkoxide functionalities produces poly(lactic acid) with low polydispersities.