Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1988-06-21
1989-08-15
Shine, W. J.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
502302, 502303, 585444, B01J 2310, B01J 2378, B01J 2382
Patent
active
048574988
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a dehydrogenation catalyst suitable for use in the dehydrogenation of hydrocarbons, especially in the dehydrogenation of ethylbenzene to styrene.
BACKGROUND OF THE INVENTION
It is generally known that iron oxide containing catalysts are used in dehydrogenation reactions e.g., the conversion of ethylbenzene into styrene.
A number of catalysts have been described which are based on iron oxide, potassium oxide, together with other promoters such as cerium, chromium, molybdenum and calcium.
In U.S. Pat. No. 4,460,706 issued July 17, 1984, is disclosed a dehydrogenation catalyst mainly based on iron and an alkali metal, a rare earth metal and calcium as promoters, and a process for dehydrogenation making use of the catalyst, e.g., a process for the preparation of styrene. Further prior art has also been discussed in the said U.S. patent application.
SUMMARY OF THE INVENTION
It has now been found that a dehydrogenation catalyst based on iron, alkali metal, rare earth metal and calcium can be further improved by containing an amount of germanium, tin or lead.
The invention accordingly relates to a dehydrogenation catalyst comprising: metal oxide, oxide, as the dioxide, and
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The selectivity to a certain compound, expressed in a percentage, is defined herein as certain compound and "b" is the total amount of alkylbenzene that has been converted.
The alkali metal compounds which may be used in the process according to the present invention are those of lithium, sodium, potassium, rubidium and cesium. Very good results have been obtained with potassium compounds. The alkali metal compounds are present in the catalyst in an amount of from 1 to 25% by weight, preferably from 5 to 20% by weight, more preferably of from 6 to 15% by weight, calculated as alkali metal oxide. Suitable alkali metal compounds are the oxides, hydroxides and carbonates. Catalysts containing more than 25% by weight of an alkali metal compound have as a disadvantage that their bulk crushing strength is not very high.
The rare earth metals which may be used are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Mixtures of rare earth metals may be used. Very good results have been obtained with cerium compounds.
The rare earth metal compounds are preferably present in the catalyst in an amount of 1 to 10% by weight, calculated as oxide in the highest valence state on the total catalyst.
It has been found that the presence of a calcium compound provides the extreme high stability of the catalyst being used in the dehydrogenation of hydrocarbons.
The calcium compound is present in an amount of 0.5 to 10% by weight, preferably 0.5 to 5% by weight, calculated as CaO.
The germanium-, tin- or lead compound is present in an amount of from 0.5 to 10% by weight, preferably in an amount of from 0.5 to 5% by weight, more preferably in an amount of from 0.8 to 4% by weight of the total catalyst and calculated on the dioxide.
An attractive feature is that the present catalyst does not need to contain molybdenum, but, if desired, molybdenum may be present.
The dehydrogenation process is suitably carried out using a molar ratio stream to alkylbenzene in the range of from 2 to 20 and preferably of from 5 to 13. Another attractive feature is that relatively low molar ratios steam to alkylbenzene can be used.
The dehydrogenation processes are suitably carried out at a temperature in the range of from 500.degree. C. to 700.degree. C. An attractive feature of the process is that relatively low temperatures can be used, particularly in the range of from 550.degree. C. to 625.degree. C.
The dehydrogenation processes may be carried out at atmospheric or super- or subatmospheric pressure. Atmospheric pressure and pressures between 1 bar and 0.5 bar absolute are usually very suitable.
The dehydrogenation processes are suitably carried out using a liquid hourly space vel
REFERENCES:
patent: 3364277 (1968-01-01), Siem
patent: 4460709 (1984-07-01), Imanari et al.
Darnanville Jean-Paul
Dejaifve Pierre E.
Dufour Jacques J. J.
Garin Roland A. C.
Shell Oil Company
Shine W. J.
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