Nikolay V. Tarabanko

Using vanadium catalysts for the oxidation of hydrogen chloride with molecular oxygen

Regeneration of chlorine by oxidation of hydrogen chloride is an important problem in the production of chloroorganic products. The known catalysts for this reaction are insufficiently active and typically not stable enough, while data on the use of V catalysts for this process are absent. Here we report on our study of the stability and catalytic activity of the industrial sulfuric acid production sulfate-promoted vanadium catalyst IK-1-6 in the process of oxidation of hydrogen chloride with molecular oxygen. Under conditions of low conversion (less than 15%) with the reaction in the external diffusion region, the catalyst activity attained 660 g/(kg cat h) at 400°C, and the mass loss rate of the catalyst was (due to the formation of volatile vanadyl chloride) 4.6 % per hour, based on vanadium. Under high conversion conditions (over 60%), the vanadyl chloride formed in the top layer of the catalyst was hydrolyzed and precipitated on subsequent layers as the conversion of the reaction mixture increased, leading to a redistribution of vanadium over the catalyst bed height and hindering its removal form the reactor. The stable operation of the catalyst can be ensured by intermittently changing the flow direction of the reactant gas in the catalytic reactor or using an array of several reactors connected in series, intermittently changing their places in the inlet-outlet chain. Our results show that the industrial sulfate-promoted vanadium catalysts for the oxidation of sulfur dioxide are more active and stable than all known catalysts of the Deacon process (except for ruthenium catalysts) and could be used for catalytic oxidation of hydrogen chloride.

Processing Pine Wood into Vanillin and Glucose by Sequential Catalytic Oxidation and Enzymatic Hydrolysis

Extractive-free pine wood was processed into vanillin (up to 18 wt.% of the initial lignin) and cellulose (typically 84–93% of the initial amount in the wood) by one-step catalytic oxidation followed by enzymatic hydrolysis of the resulting cellulose into glucose (reducing sugar yield up to 70% based on the post-oxidation cellulose). Correlation between the cellulose conversion in hydrolysis and the lignin content in the post-oxidation lignocellulosic material was established, which follows the general trend for the products of various delignification methods. The obtained results demonstrate the practical possibility of efficient two-step processing of wood into vanillin and glucose.

Catalytic Oxidation of Lignins into the Aromatic Aldehydes: General Process Trends and Development Prospects

This review discusses principal patterns that govern the processes of lignins’ catalytic oxidation into vanillin (3-methoxy-4-hydroxybenzaldehyde) and syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde). It examines the influence of lignin and oxidant nature, temperature, mass transfer, and of other factors on the yield of the aldehydes and the process selectivity. The review reveals that properly organized processes of catalytic oxidation of various lignins are only insignificantly (10–15%) inferior to oxidation by nitrobenzene in terms of yield and selectivity in vanillin and syringaldehyde. Very high consumption of oxygen (and consequentially, of alkali) in the process—over 10 mol per mol of obtained vanillin—is highlighted as an unresolved and unexplored problem: scientific literature reveals almost no studies devoted to the possibilities of decreasing the consumption of oxygen and alkali. Different hypotheses about the mechanism of lignin oxidation into the aromatic aldehydes are discussed, and the mechanism comprising the steps of single-electron oxidation of phenolate anions, and ending with retroaldol reaction of a substituted coniferyl aldehyde was pointed out as the most convincing one. The possibility and development prospects of single-stage oxidative processing of wood into the aromatic aldehydes and cellulose are analyzed.

Thermodynamics of α-angelicalactone polymerization

Abstract Thermodynamics of sodium butoxide-catalyzed polymerization of α-angelicalactone (a five-member unsaturated lactone) is studied by calorimetric methods. A polymer with Mw = 2,500 g/mol and the ratio of C–O to C–C inter-monomeric bonds 87–13% is obtained; this polymerization is characterized by the values of = −33.41 kJ/mol, = −42.69 J/(mol∙K) and = −20.68 kJ/mol. This and similar polymers and copolymers are biodegradable and can be produced from commercially available green bio-platform feedstock: renewable carbohydrates and levulinic acid.

Synthesis of a Polyconjugated Polymer by Aldol Condensation of 2,5-Diformylfuran and Acetone

Pioneer synthesis of the product of aldol polycondensation between 2,5-diformylfuran and acetone is presented. The synthesis was accomplished by a direct reaction of diformylfuran and acetone in dimethyl sulfoxide with addition of aqueous sodium hydroxide as a catalyst. The fact of the aldol condensation occurrence and formation of the polyconjugated oligomers in this system is confirmed by 1H nuclear magnetic resonance and molecular absorption spectroscopy. Cannizzaro reaction plays a significant side process role in the studied system, leading to the loss of diformylfuran’s aldehyde groups and their inability to participate in polymer chain growth. A solid polymeric product of brown color was isolated with the yield of 28 % based on the initial diformylfuran. The solid product is insoluble (judging by the lack of coloration in liquid) in various tested solvents: water, 1,4-dioxane, dimethyl sulfoxide, acetone, chloroform, or 1,2-dichloroethane with trifluoroacetic acid mixed in different proportions. The presence of polyconjugated chains in the solid product is confirmed by electron spin resonance spectroscopy.

Synthesis of Copolymers of Furandicarboxylic Acid, Ethylene Glycol, and Poly(Angelica Lactone)

This work demonstrates the possibility of creating biodegradable derivatives of poly(ethylene furandicarboxylate) by modification with poly(angelica lactone) chains. Block copolymers with the content of angelica lactone 33-50 mol. % (based on monomeric links) were obtained. Polymer yields were 60-70 %, and weight average molecular weights attained 36-45 kDa. The results of the polymers biodegradation are presented.