Ya. I. Isakov

Aromatization of ethane on metal-zeolite catalysis

Conclusions1.Catalytic systems based on TsVM high-silica zeolites are active catalysts of ethylene and ethane aromatization. The yields of aromatic hydrocarbons from ethylene on the H form of the TsVM are as high as 75%. The catalyst activity increases in the series Na-TsVM (I) ≪ HNa-TsVM (II) < H-TsVM (III), apparently governed by their acidic function; the catalysts II and III are active in the aromatization of ethane.2.The introduction of a dehydrogenating component into the H form of the TsVM, in particular platinum, increases the yield of aromatic hydrocarbons from ethane to 20%.3.The aromatization of ethane in the presence of the bifunctional system M/H-TsVM (M=Pt, Pd, Rh) is influenced substantially by preliminary high-temperature treatment of the catalyst (air alone, air and hydrogen, or hydrogen alone).4.In the course of ethane and ethylene conversions, the catalytic system M/H-TsVM “evolves, ” with an increase in the yield of aromatic hydrocarbons.

Forms of nickel-Components of nickel aluminosilicate catalysts of the dimerization of ethylene

1. Crystalline and amorphous nickelaluminosilicate catalysts, containing all the nickel in the form of the metal, are inactive in dimerization and other conversions of ethylene at 150–250°. 2. Nickel zeolite catalysts, containing NiO on the surface of the zeolite or Ni2+ ions in the cavities, are active in these reactions.

Transformations of butyraldehyde in the presence of catalysts based on large-pore molecular sieves VPI-5 and AlPO4-8

It is found that zeolite-like crystalline aluminophosphates VPI-5, Si-VPI-5, and Mn-VPI-5 as well as those dirived from them, AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8, are capable of catalyzing aldol condensation and crotonization of butyraldehyde (BA). Pd/AlPO{in4}-8 is catalytically active in hydrocondensation of BA with H{in2} at atmospheric pressure. The activities in BA conversion to 2-ethylhexane-3-ol-1-al increase in the following order: Mn-VPI-5 < Si-VPI-5 < VPI-5. The same order of activities is also found for AlPO{in4}-8, SAPO{in4}-8, and MnAPO{in4}-8. These catalysts are characterized by a lower initial activity in crotonization of BA than M{su+}NaX (CsNaX), but they are much more stable. Pd/AlPO{in4}-8 catalyzes BA conversion to 2-ethylhexanal even in the absence of H{in2} feed to the reaction zone. The influence of catalyst pretreatments and experimental conditions on the catalyst structures and catalytic activities is discussed.

Cyclodimerization of bicyclo[2.2.1]hepta-2,5-diene in the presence of rhodium-containing zeolite catalysts

It has been shown that norbornadiene is dimerized in the presence of rhodium-containing zeolite catalysts, forming hexacyclic [4+2]dimers preferentially. The effect of the structure and the method of preparation and pretreatment of the catalysts on their activity and selectivity in norbornadiene cycloaddition was studied. The influence of the above parameters on the change in the electronic state of rhodium in the course of the reaction was also investigated.

Catalytic Properties of a Zeolite System in Bicyclo [2. 2. 1] Hepta-2, 5-Diene Reactions

It is shown that acidic forms of zeolites of different types catalyze bicyclo [2. 2. 1] hepta-2, 5-diene hydration. In the presence of wide-pore REE-Y zeolites norbornadiene and aromatic compounds form alkylated products such as endo-5-phenyl norborn-2-ene.

A study of polyfunctional zeolite catalysts. Communication 7. Catalytic properties of metal-M1+NaX zeolite systems in the hydrocondensation of butyraldehyde

Conclusions1.Butyraldehyde and hydrogen are converted to 2-ethylhexanal and 2-ethyl-1-hexanol on systems containing and metal (Pt, Pd, Rh, Ni, and Co) and zeolite M1+NaX (M1+=Na+, K+, and Rb+) at atmospheric pressure and 100–200°C. This finding confirms the bifunctional catalytic effect of these systems.2.The Pd/M1+NaX systems displays the greatest selectivity of the catalysts studied in the one-step synthesis of 2-ethylhexanal from butyraldehyde and H2.

The effect of acidity on the catalytic action of PdCu zeolites in the oxidation of ethylene to acetaldehyde

Conclusions1.The acidity determines the activity of PdCu ion-exchange catalyst based on type A, X, and Y zeolites and mordenite in the oxidation of ethylene to acetaldehyde. Increasing the concentration of acidic OH groups in the PdCuNaY catalyst through decationization reduces the activity, selectivity, and stability of the catalyst.2.IR studies have shown that NH3, introduced into the PdCu zeolite either through adsorption or as part of Pd(NH3)42+ complexes, can interact with either the acidic H+ centers of the aluminosilicate crystals or with the transition-metal cations. There is the possibility of a redistribution of NH3 between the NH4+ ions and the M(NH3)X2+ faujasite complexes.3.The reversible poisoning of PdCu zeolites by ammonia is due, in the first instance, to the formation of ammoniacal complexes with the palladium cations. Increasing the acidity of the PdCu zeolite reduces the deactivating action of ammonia.

IR-spectroscopic investigation of the effect of water on the catalytic properties of PdCuNaY zeolite in the oxidation of ethylene to acetaldehyde

Conclusions1.It was determined by IR spectroscopy that the catalytic properties of PdCuNaY zeolite in the oxidation of ethylene to acetaldehyde are determined by the amount of water in the zeolite: With a water content of up to 15%, only traces of acetaldehyde are formed, and an increase in the water content (up to 40–44%) causes an increase in the activity of the catalyst.2.The role of water in the catalysis of ethylene oxidation on PdCuNaY was discussed on the basis of an assumption of the similarity of mechanisms of homogeneous and heterogeneous oxidation of olefins to carbonyl compounds and of the properties of hydrated Y-type zeolites containing palladium and copper cations.

Transformation of n-butyraldehyde on zeolite catalysts

1. On the zeolites NaY, KNaY, HNaY and NdNaY, at 150–250°, butyraldehyde undergoes mainly the crotonic condensation with the formation of 2-ethylhexenal. The most active catalyst is KNaY, the most stable is NaY, and the least selective are HNaY and NdNaY. 2. Butanol, 2-ethyl-1-hexanol, 2-ethylhexanal, and 2-ethylhexenal are obtained in the presence of 4% Ni/NaY in a hydrogen atmosphere, the ratio in the yields of which changes during the course of catalyst operation.

Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y′, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C3-C5 alcohols and for alkylation ofm-xylene bytert-butyl alcohol.