Catalysis in Industry最新文献

Industrial wastewaters from enterprises using dyes are one of the main contaminants of the environment and surface waters. In recent years, much attention has been paid to innovative ways of removing this problem. This work reviews research over the recent decade on different ways of removing biological, chemical, and physical dyes and evaluates their efficiency. The possibility of using cellulose and cellulose based materials in the removing dye from aqueous solutions is shown. Special emphasis is placed on the composites based on cellulose and metal-organic frameworks (Cell-MOFs). Main approaches to creating Cell-MOF materials and the possibilities of controlling their properties are considered. Examples of using Cell-MOF materials to remove dye from aqueous solutions via adsorption and catalytic methods are given. Problems and prospects of applying them in practice are discussed.

The focus on green energy requires the search for environmentally friendly energy storage systems. The choice of ammonia as a potential container for hydrogen is attributed to the high energy content in it and the absence of carbon and nitrogen oxide emissions during decomposition. In this study, Co–Al₂O₃/SiO₂ ammonia decomposition catalysts activated by the different methods, namely, cyclic reduction–carburization–reduction (RCR) and reduction–oxidation–reduction (ROR) procedures, have been tested and compared with a catalyst subjected to the conventional reduction of cobalt with hydrogen (R). The samples have been characterized by H₂-TPR, TEM, and XRD using synchrotron radiation; the studies have shown the invariance of the structural properties of the catalysts during reaction. Since the activity and effective activation energy values of the studied catalysts are similar, catalyst R characterized by the simplest synthesis procedure has been chosen for a long-term test, where it has exhibited high on-stream stability.

A set of Ni–Mo bimetallic catalysts based on Ni/ZSM-23 with an initial Ni content of 5 wt % has been synthesized. The catalysts have been tested in the hydrotreating of a mixture of fatty acids (C₁₆–C₁₈) in a flow reactor at a temperature of 300°C, a pressure of 2.5 MPa, and WHSV = 8.4 h⁻¹. The effect of the metal ratio on the activity, isoalkane selectivity, and stability of the catalysts in the hydrotreating of a fatty acid mixture has been shown. The highest deoxygenating capacity and the highest isoalkane yield have been found in the presence of a catalyst with a Mo/(Ni + Mo) ratio of 0.25, in which, according to XPS, the Mo/(Ni + Mo) ratio on the surface is 0.4.

Ethanol is one of the promising sources of hydrogen (synthesis gas), in particular, in various power engineering applications. Synthesis gas can be produced from ethanol by various methods, such as steam and autothermal reforming, which are endothermic and thermoneutral reactions, respectively. Control and management of heat and mass transfer during the occurrence of these reactions is an important task, which can be solved by using catalysts supported on heat-conducting metal substrates. This paper describes results of studying the physicochemical properties of FeCrAl gauze-supported Pt-, Rh-, Pd-, Ru-, Ni-, and Co-containing structured catalysts tested in the steam and autothermal reforming of ethanol. Among the tested samples, the highest efficiency in the steam and autothermal reforming of ethanol is exhibited by the ruthenium catalyst, which provides an equilibrium composition of the products without visible signs of carbonization.

Steam and autothermal ethanol reforming provides the production of synthesis gas suitable for use both in fuel cells and as a feedstock as a feedstock the chemical industry. The effective occurrence of these reactions requires heat transfer control. In the case of the endothermic steam reforming of ethanol, the problem of heat transfer from the reactor walls to the catalyst bed arises. For the thermoneutral autothermal reforming (steam–air conversion) of ethanol, the heat evolved in the frontal part of the catalyst bed due to ethanol oxidation by oxygen should be redistributed along the catalyst bed to compensate for the endothermic effect of ethanol steam reforming. Structured catalysts based on heat-conducting substrates—metal gauzes, metal foam, and other supports—are well suited to solving these problems. These catalysts are represented by a complex composite material with a multilevel “structured metal substrate–structural oxide component–active oxide–metal/alloy nanoparticle” structure, which combines the functions of a heat exchanger, a flow distributor, and a catalyst. This paper describes results of synthesizing structured Pt-, Rh-, Pd-, Ru-, Ni-, and Co-containing catalysts supported on a FeCrAl gauze and studying their catalytic properties.

The catalytic properties of palladium catalysts based on Al₂O₃, SiO₂, their mechanical mixtures with SO₄–ZrO₂, and a Pd/SO₄–ZrO₂–Al₂O₃ catalyst in the hexane isomerization reaction have been studied. The catalysts have been characterized by low-temperature nitrogen adsorption, X-ray diffraction analysis, transmission electron microscopy, temperature-programmed reduction, IR spectroscopy of adsorbed CO, and X-ray photoelectron spectroscopy. It has been shown that the nature of the support and the palladium precursor affect the size and charge state of palladium species in the catalysts. It has been found that the highest activity in the hexane isomerization reaction is exhibited by catalyst systems that contain positively charged palladium species.

The effect of the conditions of ethylene conversion to propylene on the product yield and the activity and stability of a NiO–MoO₃/Al₂O₃ catalyst has been studied. Tests in a flow reactor with a fixed catalyst bed at temperatures of 100–250°C, near-atmospheric pressure, and an ethylene weight hourly space velocity of 0.25–2 h⁻¹ have been conducted. It has been found that the maximum propylene yield of 57 wt % is achieved at 150°C and 0.25 h⁻¹. The ethylene conversion reaches 89%. A kinetic model of the process to describe the formation of the main reaction products has been proposed. It has been shown that, during ethylene conversion, carbon deposits are formed on the surface of the catalysts; when the temperature and contact time are increased, the amount of deposits grows, and the oxidation state of molybdenum atoms changes from +6 to +4/+5.

The effect of catalytically active vanadium(V) atoms on the physicochemical properties of a silicotungstic heteropoly acid has been studied. It has been shown that introducing vanadium(V) atoms into a framework of monovacant W-containing heteropoly anions in the form of a H₆V₁₀O₂₈ solution prepared using the environmentally friendly peroxide approach ensures the formation of mixed Si–W–V anions with the retention of structural integrity. It has been demonstrated that the partial substituting of such large cations as Cs⁺ and nBu₄N⁺ for protons results in the precipitation of insoluble acidic А_4.5H_0.5SiW₁₁VO₄₀ salts, the properties of which change substantially depending on the type of the introduced counterion (А⁺). The textural characteristics of the synthesized salts have been compared, their TG/DTG/DSC profiles have been obtained, and their phase compositions have been analyzed. IR-ATR, XRD, and ICP-AES characterizations of samples after hydrothermal treatment have proved that the synthesized salts are highly stable. Samples display activity as reversible oxidizers in the reaction of 5-hydroxymethylfurfural conversion in an aqueous medium with a yield of 2,5-diformylfuran up to 89% while retaining their efficiency upon repeated use.

The kinetics of coke combustion at temperatures of 525–650°C on a K–CrO_x/γ-Al₂O₃ catalyst for the direct dehydrogenation of n-butane to butadiene-1,3, which is an analogue of a commercial catalyst, has been studied. It has been shown that under the studied conditions, the coke combustion reaction is described by a first-order kinetic equation with respect oxygen and coke at an apparent activation energy of ~93 kJ/mol. The adequacy of the kinetic model has been confirmed by agreement between the calculated results and the test data.

An analysis of general approaches to organizing and developing the production of low-tonnage chemical products of organic nature is performed. A condition for manufacturers to successfully compete in the market of low-tonnage chemical products (LTCs) is the need to move from individual installations for obtaining them to flexible multi-product chemical–technological systems (CTSes). The possibility of using flow microreactor systems to synthesize small quantities of high-purity organic compounds are considered. Examples of developing a number of technologies for obtaining such organic compounds as captax, altax, furfural, benzguanamine, and di-chloro-di-para-xylylene are substantiated, along with a variety of integrated approaches to rationally organizing the production of low- and medium-tonnage products.