Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,... – Hydrocarbon is contaminant in desired hydrocarbon
Patent
1998-09-03
2000-09-12
Yildirim, Bekir L.
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
Hydrocarbon is contaminant in desired hydrocarbon
585259, 585261, 585263, 585264, 585274, 585276, C07C 503
Patent
active
061180343
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the selective hydrogenation of dienes, in particular of dienes in reformate streams (feed streams) over a nickel-containing precipitated catalyst. In addition, the present invention relates to a process for preparing high-purity aromatics or aromatic mixtures.
The reformate produced by catalytic reforming of naphtha represents a very important source of aromatics for isolating pure aromatics. Important constituents of the reformate stream are aromatic compounds such as benzine, toluene, xylene and ethylbenzene. The boiling range of the hydrocarbon mixture is between 60 and 180.degree. C. Apart from the saturated hydrocarbons and aromatic compounds, the untreated reformate streams contain other constituents such as olefins and diolefms. To further process them to give pure aromatics, up to now a series of distillation, extraction and extractive distillation steps were used.
If high purities are required, the diene compounds which are difficult to separate off by means of the abovementioned physical processes have to be removed from the pure aromatic fraction. According to Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. A3, Page 490, Verlag Chemie, this is carried out by further treating the pure aromatics over an active alumina: on passing through the fixed bed, the diene compounds are selectively adsorbed. Disadvantages of this process are the high solids consumption and the necessity of disposing of the alumina contaminated with hydrocarbon compounds, disadvantages which are becoming increasingly important in line with ever stricter environmental controls.
An alternative process comprises the selective hydrogenation of traces of unsaturated compounds. FR-A 2 720 754 discloses, in the case of pyrolysis gasoline, selectively hydrogenating dienes over an impregnated palladium catalyst at about 150.degree. C. and about 15 bar.
It is an object of the present invention to provide a process for the selective hydrogenation of dienes in which refineries.
We have found that this object is achieved by a process for the selective hydrogenation of dienes in diene-containing feed streams, which comprises hydrogenating such a diene-containing feed stream over a nickel-containing precipitated catalyst at from 40 to 100.degree. C., a pressure of from 3 to 20 bar and a WHSV of from 1 to 10 kg/(l.times.h) in the presence of free hydrogen.
According to the present invention it has been found that nickel-containing precipitated catalysts which are known per se from EP-A 0 672 452 allow very effective selective hydrogenation of dienes, with the hydrogenation using this catalyst being carried out with high reformate space velocities over the catalyst and under low-pressure and low-temperature conditions. Using the process of the present invention, it is possible, during operation under low pressure and temperature conditions and a high reformate throughput, to feed the hydrogen into the hydrogenation reactor in such a way that the amount fed in is regulated as a function of the dienes being hydrogenated.
PRECIPITATED NICKEL CATALYST
The precipitated nickel catalysts used according to the present invention are described in EP-A 0 672 452. These catalysts consist essentially of from 65 to 80% of nickel calculated as nickel oxide, from 10 to 25% of silicon, calculated as silicon dioxide, from 2 to 10% of zirconium, calculated as zirconium oxide and from 0 to 10% of aluminum, calculated as aluminum oxide, with the proviso that the sum of the contents of silicon dioxide and aluminum oxide is at least 15% (percentages in percent by weight, based on the total mass of the catalyst). They are prepared by addition of an acid aqueous solution of nickel, zirconium, and, if desired, aluminum salts to a basic aqueous solution of silicon and, if desired, aluminum compounds, with the pH being lowered to at least 6.5 and subsequently being adjusted to from 7 to 8 by an addition of further basic solution, isolating the solid thus precipitated, drying, shaping and calcining.
The
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Ullmann's Enc. of Ind. Chem., vol. A3, 5th Edition, p. 490, 1985.
Dilling Stephan
Kons Germain
Muller Hans-Joachim
Polanek Peter
Schwab Ekkehard
BASF - Aktiengesellschaft
Yildirim Bekir L.
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