A process for preparing butadiene from n-butenes, comprising the steps of: absorbing C4 hydrocarbons comprising butadiene and n-butenes, obtained from oxidative dehydrogenation of n-butenes, in an aromatic hydrocarbon solvent as an absorbent and removing uncondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, any carbon oxides, aromatic hydrocarbon solvent and any inert gases as gas stream d2, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1; and at least partly recycling the gas stream d2 as cycle gas stream a2 into the oxidative dehydrogenation zone, wherein the content of aromatic hydrocarbon solvent in the cycle gas stream a2 is limited to less than 1% by volume.

A process for preparing butadiene from n-butenes, comprising the steps of: absorbing C4 hydrocarbons comprising butadiene and n-butenes, obtained from oxidative dehydrogenation of n-butenes, in an aromatic hydrocarbon solvent as an absorbent and removing uncondensable and low-boiling gas constituents comprising oxygen, low-boiling hydrocarbons, any carbon oxides, aromatic hydrocarbon solvent and any inert gases as gas stream d2, giving an absorbent stream laden with C4 hydrocarbons and the gas stream d2, and then desorbing the C4 hydrocarbons from the laden absorbent stream, giving a C4 product gas stream d1; and at least partly recycling the gas stream d2 as cycle gas stream a2 into the oxidative dehydrogenation zone, wherein the content of aromatic hydrocarbon solvent in the cycle gas stream a2 is limited to less than 1% by volume.

The present invention provides a method for producing an oxide catalyst comprising Mo, V, Sb, and Nb for use in a gas-phase catalytic oxidation reaction or a gas-phase catalytic ammoxidation reaction of propane or isobutane, the method comprising: a preparation step of preparing a first aqueous mixed solution containing Mo, V, and Sb; a mixing step of mixing the first aqueous mixed solution with a support raw material comprising silica sol, and a Nb raw material to obtain a second aqueous mixed solution; a drying step of drying the second aqueous mixed solution to obtain a dry powder; and a calcination step of calcining the dry powder to obtain the oxide catalyst, wherein the support raw material comprises 25% by mass or more, based on SiO.sub.2, of the silica sol having an average primary particle size of 3.0 nm or larger and smaller than 11 nm based on a total amount of the support raw material, and the silica sol comprises 55% or more of silica sol particles having a primary particle size of smaller than 11 nm.

The present invention provides a method for producing an oxide catalyst comprising Mo, V, Sb, and Nb for use in a gas-phase catalytic oxidation reaction or a gas-phase catalytic ammoxidation reaction of propane or isobutane, the method comprising: a preparation step of preparing a first aqueous mixed solution containing Mo, V, and Sb; a mixing step of mixing the first aqueous mixed solution with a support raw material comprising silica sol, and a Nb raw material to obtain a second aqueous mixed solution; a drying step of drying the second aqueous mixed solution to obtain a dry powder; and a calcination step of calcining the dry powder to obtain the oxide catalyst, wherein the support raw material comprises 25% by mass or more, based on SiO.sub.2, of the silica sol having an average primary particle size of 3.0 nm or larger and smaller than 11 nm based on a total amount of the support raw material, and the silica sol comprises 55% or more of silica sol particles having a primary particle size of smaller than 11 nm.

The preparation of an oxidative dehydrogenation catalyst comprising Mo, V, Nb and Te using a hydrothermal step. In some embodiments, the activity and reproducibility of the catalyst is improved by conducting the hydrothermal step while permitting gaseous products to leave the reactor. In some instances a condenser may be upstream of the outlet of the reactor.

The preparation of an oxidative dehydrogenation catalyst comprising Mo, V, Nb and Te using a hydrothermal step. In some embodiments, the activity and reproducibility of the catalyst is improved by conducting the hydrothermal step while permitting gaseous products to leave the reactor. In some instances a condenser may be upstream of the outlet of the reactor.

A catalytic composition and process useful for the conversion of an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile, hydrogen cyanide and acetonitrile and mixtures thereof, wherein the catalyst exhibiting increased selectivity to hydrogen cyanide compared to prior art catalysts.

A catalytic composition and process useful for the conversion of an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile, hydrogen cyanide and acetonitrile and mixtures thereof, wherein the catalyst exhibiting increased selectivity to hydrogen cyanide compared to prior art catalysts.

Oxidative dehydrogenation of light paraffins, such as ethane at moderate temperatures (<500 C.) to produce ethylene without the formation of side products such as acetic acid and/or other oxygenated hydrocarbons is achieved using tellurium-free, multimetallic catalysts possessing orthorhombic M1 phase and other crystalline structures that have an important role for obtaining high performance catalysts for the oxidative dehydrogenation of ethane to ethylene. Such catalysts are prepared using thermal and hydrothermal methods.

Oxidative dehydrogenation of light paraffins, such as ethane at moderate temperatures (<500 C.) to produce ethylene without the formation of side products such as acetic acid and/or other oxygenated hydrocarbons is achieved using tellurium-free, multimetallic catalysts possessing orthorhombic M1 phase and other crystalline structures that have an important role for obtaining high performance catalysts for the oxidative dehydrogenation of ethane to ethylene. Such catalysts are prepared using thermal and hydrothermal methods.