V. P. Kalinin

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.

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.

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.

The promoting effect of CO2 on zeolite catalysts

1. Through study of the alkylation of benzene by ethytene on a 0.67 CaNaY zeolite catalyst it has been shown that the increase in zeolite activity in carbonium type reactions under the action of CO2 is due to proton enrichment and an increase in the number of acid centers capable of participating in the catalytic process. 2. Dry CO2 adsorbs on the completely dehydrated CaNaY zeolite to form monodentate carbonate structures, without altering the system acidity. In the presence of water, formation of these carbonate structures is accompanied by an increase in the concentration and strength of the Bronsted acid centers.

Investigation of polyfunctional zeolite catalysts. Communication 6. Influence of pretreatment and conditions of use on catalytic properties of nickel-zeolite systems in alkylation of benzene with ethylene

Conclusions1.The ratio between the acid (alkylating) function and oligomerizing function, as well as the activity and selectivity of the bifunctional catalysts NiNaY, NiCaNaY, and NiO/CaNaY, depend to a great degree on the catalyst pretreatment and on the conditions of catalyst use in the reaction of benzene with ethylene.2.When the NiCaNaY and NiO/CaNaY are used in a stream of CO2, the C2H4 conversion to ethylbenzene is considerably higher, and the conversion to sec-butylbenzene is considerably lower, than in experiments without carrier gas or with N2 or CO.3.The IR spectra of the catalysts and C2H4 and CO2 adsorbed on these catalysts have been investigated in order to clarify the reasons for the phenomena that have been observed.

Polyfunctional zeolite catalysts 5. Catalytic properties of NiMn+NaY zeolites in the alkylation of benzene by ethylene

1. The activity and selectivity of the bifunctional NiMNaY zeolite catalysts in the alkylation of C6H6 by ethylene can be modified by varying the nature of the Mn+ cation, the Ni2+: Mn+ ratio, the total extent of exchange of Na+, and the mode of incorporation of Ni2+ and Mn+ into the faujasites. Of zeolites of the same composition (NiCaNaY) the most effective is that prepared by consecutive substitution of Na+ in NaY by Mn+ (Ca2+) and Ni2+). 2. An IR spectroscopic study of the adsorption of Py, C2H4, and CO has revealed that the proton acidity, which is responsible for the activity of NiMNaY in the alkylation of benzene by olefins, is controlled mainly by the composition of the zeolite; the activity in the dimerization of ethylene is due to the nickel cations, whose state and properties depend on the composition and mode of preparation of the catalyst.

The investigation of polyfunctional zeolite catalysts

1. Mixtures of NiNaA and CaNaY or NiNaX and CaNaY zeolites, one of which is active in ethylene dimerization and the other of which is active in alkylation of benzene with olefins, are bifunctional catalytic systems and are effective in the synthesis of secondary butylbenzene (SBB) from C6H6 and C2H4. 2. The properties of these systems can be regulated by changing the ratio of components responsible for the activity of the catalysts in various reactions, the method of their mixing, and also the conditions of use. 3. In NiNaX-CaNaY catalysts, obtained by pressing mixtures of powdery zeolites, Ni2+ and Ca2+ cations evidently migrate from one zeolite to another, as a result of which catalysts are formed, possessing high activity in dimerization of C2H4 and the synthesis of SBB, which would be expected with simple additivity of the properties of NiNaX and CaNaY.

Study of polyfunctional zeolite catalysts

1. The catalytic properties of the Ni forms of various types of synthetic zeolites in the reaction of benzene with ethylene are determined by their structure, composition, and conditions under which they are used. 2. The NiNaA zeolites accelerate only the dimerization of C2H4, and are inactive in the alkylation of C6H6 with olefins. From benzene and ethylene it is possible to obtain on NiX and NiY either predominantly sec-butylbenzene (SBB) (selectivity 80–86%) or SBB and butenes in approximately equal amounts.

Polyfunctional zeolite catalysts Communication 1. Catalytic properties of NiO-CaX and NiO-CaY systems in reaction of benzene with ethylene

1. The bifunctional catalysts NiO-CaX and NiO-CaY are active in the synthesis of sec-butylbenzene (SBB) from benzene and ethylene. 2. The activity, selectivity, and stability of the catalysts are regulated by varying the amount of nickel in them, the degree of Na+ exchange by Ca2+, and the SiO2/Al2O3 ratio in the zeolite, and also the conditions of their use. 3. On NiO-CaX catalysts the reaction of C6H6 with C2H4 goes with the formation of SBB and butenes. In the presence of NiO-CaY catalysts with a low amount (<1%) of NiO it is possible to obtain the butyl and ethylbenzenes, and predominantly SBB on NiO-CaY catalysts with more than 1% of NiO.