G.Ya. Popova

In situ FTIR Study of the Adsorption of Formaldehyde, Formic Acid, and Methyl Formiate at the Surface of TiO2 (Anatase)

The catalytic properties of TiO2 (anatase) in the reactions of formaldehyde oxidation and formic acid decomposition are examined. At 100–150°C, formaldehyde is converted into methyl formate with high selectivity regardless of the presence of oxygen in the reaction mixture. Formic acid is decomposed to CO and water. Surface compounds formed in the reactions of formaldehyde, formic acid, and methyl formate with TiO2 (anatase) are identified by in situ FTIR spectroscopy. In a flow of a formaldehyde-containing mixture at 100°C, H-bonded HCHO, dioxymethylene species, bidentate formate, and coordinatively bonded HCHO are observed on the TiO2 surface. In the adsorption of formic acid, H-bonded HCOOH and two types of formates (bidentate and unsymmetrical formates) are formed. In the adsorption of methyl formate, H-bonded HCOOCH3, HCOOCH3 coordinatively bonded via the carbonyl oxygen, and bidentate formate are identified.

Determination of surface intermediates during the selective oxidation of formaldehyde over V–Ti–O catalyst by in situ FTIR spectroscopy

Abstract Formaldehyde oxidation to formic acid on V–Ti–O catalyst was studied in a flow-circuit setup with a differential reactor and in the IR cell. Surface intermediates leading to formic acid formation were identified. Catalyst calcination temperature was varied to study its effect on catalyst performance and surface species structure.

Formation of active component of MoVTeNb oxide catalyst for selective oxidation and ammoxidation of propane and ethane

Abstract The effect of slurry pH on the formation of active component of MoVTeNbO catalyst for selective (amm)oxidation of ethane and propane has been studied. pH affects the nature and composition of the crude and dry precursors as well as chemical and phase composition of the final catalyst. The most effective catalyst is prepared at pH = 3.0, which is characterized by a maximum content of M1 phase.

Preparation, active component and catalytic properties of supported vanadium catalysts in the reaction of formaldehyde oxidation to formic acid

Abstract The influence of the support nature was investigated with supported vanadium catalysts prepared by a wet impregnation method. SiO 2 , γ-Al 2 O 3 , ZrO 2 and TiO 2 (anatase) were used as supports. Two series of catalysts were prepared, the first one consisting of catalysts of composition ca. 20% wt. V 2 O 5 /80% wt. support (series 1) and the second one prepared by washing the series 1 samples with nitric acid (series 2). In the catalysts of series 1 (except 20% V 2 O 5 /80% SiO 2 ), vanadium is represented by both monolayer species (monomeric and polymeric VO x ) and crystalline V 2 O 5 phase. When vanadium is supported on SiO 2 , only the crystalline V 2 O 5 is formed. Washing the samples of series 1 with nitric acid removes crystalline V 2 O 5 phase. Monomeric and polymeric vanadia species are more active in the reaction of formaldehyde oxidation to formic acid as compared to V 2 O 5 .

Kinetics of formaldehyde oxidation on a vanadia-titania catalyst

The heterogeneous catalytic oxidation of formaldehyde in the gas phase may be considered as an alternative to the multistep liquid-phase synthesis of formic acid. Monolayer vanadia-titania catalysts are active and selective in the oxidation of formaldehyde to formic acid. Detailed investigation of kinetics of formaldehyde oxidation over a monolayer vanadia-titania catalyst was carried out. It was established that byproduct form via a consecutive-parallel reaction network. CO2 results from formaldehyde oxidation via parallel pathway and from formic acid overoxidation via consecutive pathway; CO forms from formic acid via consecutive pathway. It was shown that oxygen and water accelerate formic acid formation and that water retards CO formation. Based on experimental data, a kinetic model of formaldehyde oxidation was developed. The kinetic model was used in the mathematical simulation of the formaldehyde oxidation process and in the determination of dynamic and design parameters of the reactor. Formic acid production by the gasphase oxidation of formaldehyde is unique and does not have any analogue. As opposed to conventional technologies, it is energy-saving, environmentally friendly, and technologically simple. An enlarged-scale pilot plant using this technology is under construction.

Heterogeneous selective oxidation of formaldehyde on oxide catalysts : In situ FTIR study of formaldehyde surface species on a V-Ti-O catalyst and oxygen effect

The interaction of formaldehyde with a highly selective V-Ti-O catalyst for the oxidation of formaldehyde to formic acid is studied by Fourier-transform infrared (FTIR) spectroscopy at 70–200‡C. In a flow of formaldehyde/oxygen mixture and in a mixture without oxygen at optimal temperatures for formic acid formation (100–140‡C), methoxy groups and other oxygenates are formed in small amounts. These are two bidentate formates and covalently bound monodentate formate. The fact that similar oxygenates are observed independently of the presence of oxygen in the reaction mixture suggests the participation of the catalyst oxygen in their formation. Oxygen accelerates the desorption of bidentate formates. Bidentate formates of one type decompose in a flow of air at 100–150‡C, and bidentate formates of the other type decompose at 170–200‡C.

Effect of preparation conditions on the phase composition of the MoVTe(Nb) oxide catalyst for the oxidative conversions of propane

The replacement of expensive propylene by propane, which requires the development of catalysts for the direct oxidation of propane into acrylonitrile, is an important and insufficiently studied problem. Multicomponent MomVnTekNbx oxide systems are promising in one-stage ammoxidation of propane to acrylonitrile. Despite considerable attention of various authors to the preparation methods for these catalysts, the reproducibility of their physicochemical and catalytic properties is low. To optimize the technology of catalyst synthesis, we studied the effect of drying method (evaporation or spray drying) for the aqueous suspension of the initial compounds on the formation of the Mo1V0.3Te0.23(Nb0.12) oxide catalyst. It is shown that the method of drying determines the chemical and phase composition of solid catalyst precursors and the phase composition of the final catalyst in high-temperature treatment. The use of spray drying provides the required physicochemical characteristics of the catalyst (the specific surface area and the phase composition) that determine the high activity and selectivity in the selective conversion of propane. These catalysts contain two crystalline phases: orthorhombic M1 and hexagonal M2 in an optimal ratio of 3: 1.

IN SITU IR SPECTROSCOPIC STUDIES OF HCOOH DECOMPOSITION OVER V-TI-O CATALYST

Decomposition of formic acid over V-Ti-O catalysts was studied by in situ IR spectroscopy. Four surface compounds, among which are H-bonded acid, one mono- and two bidentate formates (BF1 and BF2), were identified in the temperature range of 100-190°C. The activation energy and rate of the BF2 decomposition were found equal to those for the CO formation. This equality points to the involvement of BF2 in the HCOOH decomposition into carbon monoxide.

Active component of supported vanadium catalysts in the selective oxidation of methanol

The structure of catalysts based on vanadium oxide supported on different oxides (SiO2, γ-Al2O3, ZrO2, and TiO2) was investigated. Their catalytic properties in the selective oxidation of methanol in a temperature range of 100–250°C were studied. It was shown that the nature of the support determines the structure of the oxide forms of vanadium. The supporting of vanadium on SiO2 and γ-Al2O3 leads to the preferred formation of crystalline V2O5; the surface monomeric and polymeric forms of VOx are additionally formed on ZrO2 and TiO2. It was established that the crystalline V2O5 oxide is least active in the selective oxidation of methanol; the polymeric forms are more active than monomeric ones. The mechanism of the selective oxidation of methanol to dimethoxymethane and methyl formate on the vanadium oxide catalysts is considered.

A new gas-phase method for formic acid production: Tests on a pilot plant

Formic acid is industrially produced from methyl formate by multi-stage liquid-phase methods characterized by high capital intensity and high energy costs. The gas-phase synthesis of formic acid by catalytic oxidation of formaldehyde with atmospheric oxygen is developed at the Boreskov Institute of Catalysis. A pilot plant with productivity of up to 3 kg of formic acid per hour is constructed; its flow sheet and the apparatus constructions fully reproduce the future industrial process. It includes two catalytic stages: the oxidation of methanol to formaldehyde and the oxidation of formaldehyde to formic acid. Methanol is oxidized over a commercial iron-molybdenum catalyst oxide under conventional conditions. The oxidation of formaldehyde to acid is performed over titania-vanadia catalyst at temperatures of 120–140°C. Because of the narrow temperature range, a two-reactor flow sheet and the partial dilution of a bed with inert filling in the first of two reactors are used at the second stage. The tests are performed at a methanol concentration in the initial mixture of 6–7 vol % and the temperature is varied in the formaldehyde oxidation reactors. Under optimum conditions, the acid yield is 87–88% relative to the converted formaldehyde and 79–81% based on the converted methanol. This is achieved at the complete conversion of methanol and 96.5–98.5% conversion of formaldehyde. The technology meets the requirements of “green” chemistry.