A catalyst having coke wherein the coke, upon analysis by infrared spectroscopy in diffuse reflection, has at least two peaks at a wavelength between 1450 cm.sup.−1 and 1700 cm.sup.−1.

The aforesaid catalyst having coke can be advantageously used in a process for the production of a diene, preferably a conjugated diene, more preferably 1,3-butadiene, said process having the dehydration of at least one alkenol having a number of carbon atoms greater than or equal to 4.

Preferably, the alkenol having a number of carbon atoms greater than or equal to 4 can be obtained directly from biosynthetic processes, or through catalytic dehydration processes of at least one diol.

When the alkenol is a butenol, the diol is preferably a butanediol, more preferably 1,3-butanediol, even more preferably bio-1,3-butanediol, i.e. 1,3-butanediol deriving from biosynthetic processes.

When the diol is 1,3-butanediol, or bio-1,3-butanediol, the diene obtained with the process is, respectively, 1,3-butadiene, or bio-1,3-butadiene.

A catalyst having coke wherein the coke, upon analysis by infrared spectroscopy in diffuse reflection, has at least two peaks at a wavelength between 1450 cm.sup.−1 and 1700 cm.sup.−1.

The aforesaid catalyst having coke can be advantageously used in a process for the production of a diene, preferably a conjugated diene, more preferably 1,3-butadiene, said process having the dehydration of at least one alkenol having a number of carbon atoms greater than or equal to 4.

Preferably, the alkenol having a number of carbon atoms greater than or equal to 4 can be obtained directly from biosynthetic processes, or through catalytic dehydration processes of at least one diol.

When the alkenol is a butenol, the diol is preferably a butanediol, more preferably 1,3-butanediol, even more preferably bio-1,3-butanediol, i.e. 1,3-butanediol deriving from biosynthetic processes.

When the diol is 1,3-butanediol, or bio-1,3-butanediol, the diene obtained with the process is, respectively, 1,3-butadiene, or bio-1,3-butadiene.

The present invention provides a method for producing 1,3-butadiene that is capable of suppressing generation of reaction by-products. The method includes: a step (A) of to obtain a produced gas containing 1,3-butadiene; a step (B) of cooling the produced gas; and a step (C) of separating the produced gas cooled in the step (B) into molecular oxygen and inert gases, and other gases containing 1,3-butadiene, by selective absorption into an absorption solvent. In the method, in the step (A), the raw material gas and a molecular oxygen-containing gas are supplied to a fixed-bed reactor with a composite oxide catalyst containing molybdenum and bismuth; the molar ratio of molecular oxygen to n-butene in the gases is 1.0 to 2.0; and the molar ratio of water vapor to n-butene in the gases supplied to the fixed-bed reactor is not more than 1.2.

The present invention provides a method for producing 1,3-butadiene that is capable of suppressing generation of reaction by-products. The method includes: a step (A) of to obtain a produced gas containing 1,3-butadiene; a step (B) of cooling the produced gas; and a step (C) of separating the produced gas cooled in the step (B) into molecular oxygen and inert gases, and other gases containing 1,3-butadiene, by selective absorption into an absorption solvent. In the method, in the step (A), the raw material gas and a molecular oxygen-containing gas are supplied to a fixed-bed reactor with a composite oxide catalyst containing molybdenum and bismuth; the molar ratio of molecular oxygen to n-butene in the gases is 1.0 to 2.0; and the molar ratio of water vapor to n-butene in the gases supplied to the fixed-bed reactor is not more than 1.2.

The present invention provides a method for producing 1,3-butadiene that is capable of suppressing generation of reaction by-products. The method includes: a step (A) of to obtain a produced gas containing 1,3-butadiene; a step (B) of cooling the produced gas; and a step (C) of separating the produced gas cooled in the step (B) into molecular oxygen and inert gases, and other gases containing 1,3-butadiene, by selective absorption into an absorption solvent. In the method, in the step (A), the raw material gas and a molecular oxygen-containing gas are supplied to a fixed-bed reactor with a composite oxide catalyst containing molybdenum and bismuth; the molar ratio of molecular oxygen to n-butene in the gases is 1.0 to 2.0; and the molar ratio of water vapor to n-butene in the gases supplied to the fixed-bed reactor is not more than 1.2.

In the present disclosure, a composite oxide catalyst capable of effectively suppressing side reactions at the time of dehydrogenation of C4 hydrocarbons having single bonds or one double bond and a process for preparing butadiene, in particular 1,3-butadiene, with a high selectivity and a high yield using the same are described.

In the present disclosure, a composite oxide catalyst capable of effectively suppressing side reactions at the time of dehydrogenation of C4 hydrocarbons having single bonds or one double bond and a process for preparing butadiene, in particular 1,3-butadiene, with a high selectivity and a high yield using the same are described.

A first stream containing 1,3-butadiene, C.sub.4 acetylenes, and optionally C.sub.3 hydrocarbons, is mixed with a portion of the liquid recycle stream from a C.sub.4 acetylene hydrogenation reactor containing hydrogenated C.sub.4 acetylenes and a molecular hydrogen-containing stream, the resulting mixed stream is then fed to a C.sub.4 acetylene hydrogenation reactor to selectively hydrogenate the C.sub.4 acetylenes in the crude butadiene stream without appreciable 1,3-butadiene conversion.

A first stream containing 1,3-butadiene, C.sub.4 acetylenes, and optionally C.sub.3 hydrocarbons, is mixed with a portion of the liquid recycle stream from a C.sub.4 acetylene hydrogenation reactor containing hydrogenated C.sub.4 acetylenes and a molecular hydrogen-containing stream, the resulting mixed stream is then fed to a C.sub.4 acetylene hydrogenation reactor to selectively hydrogenate the C.sub.4 acetylenes in the crude butadiene stream without appreciable 1,3-butadiene conversion.

A first stream containing 1,3-butadiene, C.sub.4 acetylenes, and optionally C.sub.3 hydrocarbons, is mixed with a portion of the liquid recycle stream from a C.sub.4 acetylene hydrogenation reactor containing hydrogenated C.sub.4 acetylenes and a molecular hydrogen-containing stream, the resulting mixed stream is then fed to a C.sub.4 acetylene hydrogenation reactor to selectively hydrogenate the C.sub.4 acetylenes in the crude butadiene stream without appreciable 1,3-butadiene conversion.