Catalysis in Industry最新文献

Aluminum oxides are the most common component used in the design of heterogeneous catalysts of oil refining and petrochemistry. The optimum characteristics of aluminum oxide supports and catalysts (e.g., specific surface area, pore size, and phase and impurity compositions) correspond to the type of hydrocarbon feedstocks and technological process. In light of the trend toward import substitution, it is becoming ever more relevant to study the market for domestic producers of aluminum hydroxide feedstocks used in the synthesis of aluminum oxides. In this work, domestic commercial samples of aluminum hydroxides are investigated via X-ray diffraction, simultaneous thermogravimetry/differential scanning calorimetry, low-temperature nitrogen adsorption, and elemental analysis. It is established that the objects of study are most often inhomogeneous in phase and contain iron, silicon, and calcium impurities. The effect of degree of crystallinity and the sizes of coherent scattering regions in aluminum hydroxides with a predominantly boehmite structure (and in some cases, aluminum hydroxides containing bayerite) on the textural characteristics of synthesized aluminum oxides is demonstrated.

The kinetics of n-butane dehydrogenation to butadiene is studied with temperature (T) variation of 550–625°C, duration of dehydrogenation stage (t) of 5–30 min, and space velocity (V) of 4400–35 200 h⁻¹ on industrial catalyst K-CrO_x/γ-Al₂O₃ at a fraction of 56–94 μm. The catalyst is stabilized before studies. The granulated catalyst in a reduction–dehydrogenation–regeneration cycle at 593°C, and then as a fraction of 56–94 μm in dehydrogenation–regeneration cycle at 650°C. The maximum selectivity toward butadiene of ~25 mol % is achieved with n-butane conversion of 26–30% (V = 35 200 h⁻¹), T = 600 °C, and t = 5 min, while the maximum yield of butadiene ~10 mol % is obtained with an increase in conversion up to ~50% (V = 8800 h^–1) under the same conditions. Raising T to 625°C and t to 30 min and lowering V to ~4400 h^–1 increases the selectivity toward by-products to ~50 mol %. It is found that the energy of activation for the rates of product formation falls in the order by-products > butylene > butadiene. A kinetic model is proposed that describes the formation of butadiene via butylene, the formation of ethane/ethylene and methane/propylene by-products during butylene hydrocracking, and secondary conversions of by-products, plus the formation of coke and its effect on catalyst activity. In the model, the inhibition of dehydrogenation reactions by components of reaction mixture is described by a mechanism in which the limiting stage is a surface reaction on two active centers. The adequacy of the kinetic model is confirmed by good agreement between the calculated and experimental results.

Mathematical modeling for the autothermal reforming of hexadecane, propane, and methane in the presence of catalyst modules of different geometric shapes has been conducted. It has been shown that a module shape that is convex toward the oncoming reaction stream can increase the maximum temperature in the frontal zone, whereas a concave shape contributes to a more uniform temperature distribution throughout the entire length of the catalyst bed. In addition, the effect of the reaction flow rate on the change in the temperature gradient has been studied; the results can subsequently be used to prevent local overheating and catalyst deactivation. The results obtained can be used as a basis for future research in the field of autothermal reforming and optimization of geometric parameters of catalysts for the conversion of hydrocarbon fuels to synthesis gas.

The authors formulate a mathematical model of the non-stationary single-stage dehydrogenation of n-butane to butadiene in an adiabatic fixed-bed reactor for the first time, based on a kinetic model that describes the formation of coke and primary and secondary by-products on a K-CrO_x/γ-Al₂O₃ catalyst. The model allows prediction of the yield of butadiene and other products depending on the activity of the catalyst, the composition of initial mixture, the period of the dehydrogenation cycle, and the degree of catalyst dilution with an inert material (including the non-uniform dilution of a catalyst with an inert material along the bed length). It also allows assessment of the temperature regime of the catalyst’s operation and the degree of its coking along the bed. It is shown that the model is adequate for describing the conversion of n-butane, the formation of butadiene and butylene, the accumulation of coke, and the loss of catalyst activity using test calculations of main technological parameters as an example.

The applicability of some commercial catalysts in the conversion of carbon dioxide into syngas is estimated. Catalysts based on Cu and transitional metals (Fe, Ni, Co) and used in large-capacity hydrogenation and syngas technology are selected for study. They include NIAP-03-01 (steam conversion of hydrocarbon gases), NIAP-06-06 (low-temperature CO conversion), AmoMax 10 (synthesis of ammonia), and Со-Al₂O₃/SiO₂ (synthesis of hydrocarbons). The catalysts are tested in the reduction of СО₂ using the reverse water gas shift (RWGS) reaction. Cu-containing catalyst NIAP-06-06 is shown to have the highest activity and selectivity in the reduction of СО₂, with 97% equilibrium in the RWGS reaction being reached at GHSV = 32 000 h⁻¹, Н₂/СО₂ = 2, and temperatures of 500–800°C. The possibility is shown of obtaining syngas with the composition required for the synthesis of hydrocarbons and methanol by changing the parameters of СО₂ reduction (temperature, Н₂/СО₂ ratio).

Polyfunctional nickel-containing catalysts based on B₂O₃–Al₂O₃ and MoO₃–Al₂O₃ oxide supports have been synthesized by sequential impregnation and studied in the conversion of ethylene into C₅₊ alkenes or propylene. The physicochemical properties of the prepared catalysts has been studied using X-ray diffraction analysis, IR spectroscopy, IR spectroscopy of adsorbed CO, UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS), temperature-programmed reduction of hydrogen (H₂-TPR), and temperature-programmed desorption of ammonia (TPD-NH₃). The most active catalysts of ethylene oligomerization are NiO/B₂O₃–Al₂O₃, where Ni²⁺ cations chemically bounded to the acidic support are formed. NiO/MoO₃–Al₂O₃ activity in conversion of ethylene to propylene is provided by the presence on the surface of ethylene dimerization active sites, i.e., Ni²⁺ cations bounded with the support acidic sites, and active sites of metathesis based on monomolybdate species.

Nanoscale Co₃O₄ has successfully been supported onto the mesoporous SBA-15 following two methods viz. direct deposition (DD) and isonicotinate ligand assisted (INL) route. The later method (INL) involves the formation of cobalt isonicotinate tetrahydrate complex inside mesopore volumes of SBA-15 and subsequent calcination of the cobalt complex loaded SBA-15 composite. The present method is found to be advantageous in reducing the formation of oxide particles outside mesopores. The synthesized materials are investigated by various physical tools such as XRD, SEM, TEM and H₂-TPR in combination with N₂ adsorption-desorption study. As a promoter, little amount of gold is also deposited in SBA-15 supported Co₃O₄ samples and all these materials are explored as catalysts in the hydrogenation of cinnamaldehyde. The composite material that is synthesized via DD method has shown promising results in the hydrogenation reaction giving 50% cinnamaldehyde (CAL) conversion with 66% selectivity for hydrocinnamaldehyde (HCAL) at 170°C under the hydrogen pressure of 2 MPa.

The review discusses the production of jet fuel from microalgae biomass. The modern standards that should be met by biojet fuel produced from microalgae biomass are described. The main methods for synthesizing jet fuel from microalgae, namely, the oil-to-jet, gas-to-jet, and sugar-to-jet processes, and the production of this fuel along with other valuable products by the integrated conversion of biomass are discussed. Data on the potential use of biofuel synthesized from microalgae biomass in blends with conventional petroleum fuel are described. Data on the prospects for using this alternative fuel in modern aviation are given.

The kinetic laws of the liquid-phase aerobic oxidation of sec-butylbenzene to the respective tertiary hydroperoxide in the presence of N-hydroxyphthalimide as a catalyst have been studied. The effect of temperature, reaction duration, and catalyst content on the sec-butylbenzene oxidation rate has been studied. Based on the experimental data obtained, a kinetic (mathematical) model of the studied process, which adequately describes the change in the concentration of the main components during reaction, has been compiled. Numerical values of rate constants of the main stages of the process have been calculated. It has been found that the use of N-hydroxyphthalimide in the sec-butylbenzene oxidation process provides an increase in the oxidation rate and hydrocarbon conversion, while maintaining the high sec-butylbenzene hydroperoxide selectivity.

This paper is a part from the series of reviews focused on the use of microalgae biomass to synthesize products for a wide range of applications. In this review, microalgae are discussed as potential renewable feedstocks for producing functional materials that have found application in the polymer industry. Strong, stable, and biodegradable microalgae bioplastics are an alternative to conventional petroleum-based plastics. Approaches to producing bioplastics from microalgae both directly from biomass (polyhydroxyalkanoates, starch, cellulose, organic acids) and by blending biomass with other polymers are discussed. Data on the prospects of using bioplastics synthesized from microalgae, in particular, by integrated biomass biorefinery, are described.