Mineral oils: processes and products – Chemical conversion of hydrocarbons – Reforming
Patent
1991-08-09
1995-01-03
Sneed, Helen M. S.
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Reforming
208 64, 502308, 502317, 502320, 502344, 502349, 585631, 585663, 585418, C10G 3506, B01J 2300, C07C 5333, C07C 541
Patent
active
053783506
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process and a catalyst for dehydrogenation or dehydrocyclization of hydrocarbons on regenerable catalysts, consisting of chromium oxide and aluminum oxide with one or more promoters from the group of alkali metal and/or alkaline earth metal compounds and with at least one additional promoter.
It is generally known that hydrocarbons can be dehydrogenated in the presence of suitable catalysts at higher temperature. Depending on the type of hydrocarbons used, in the case of paraffins especially as a function of the chain length, either a dehydrogenation to monoolefins or diolefins or, possibly also simultaneously, a cyclization i.e. ring formation, mainly to aromatic compounds, with simultaneous cleavage of hydrogen, a so-called dehydrocyclization, takes place.
Below, by the term "dehydrogenation" are understood all reactions in which hydrogen is cleaved from hydrocarbons of any type, without regard to whether the dehydrogenation products form straight or branched chains whether they are cyclic or whether they are singly or repeatedly unsaturated.
As can be seen, for example, from U.S. Pat. No. 3,719,721, aluminum oxide-chromium oxide catalysts are used for such dehydrogenation processes.
But since catalysts with aluminum oxide as support material exhibit acid properties, which lead to undesirable isomerization or cracking reactions, these known catalysts in addition contain a small portion of an alkali metal oxide and/or alkaline earth metal oxide, which acts as a base and thus improves the selectivity of the catalyst.
As other promoters, the known catalysts contain niobium or tantalum oxide or also, as a comparison example, cerium oxide, which contributes to increasing the catalyst activity.
Despite the improved selectivity and activity of the chromium oxide catalysts, in the dehydrogenation according to the process of the above-mentioned U.S. Patent, carbon or coke results, which is precipitated on the catalyst and deactivates it continuously, which means a considerable drawback relative to economy and investment costs.
The known process further has the drawback that the selectivity or activity of the catalyst is not sufficient to keep the by-product formation values optimally low--especially to prevent multiple dehydrogenations--to obtain pure monoolefin dehydrogenation products in a suitable feedstock stream.
SUMMARY OF THE INVENTION
Therefore, it is the object of this invention to configure a process and a catalyst of the above-mentioned type so that a minimal coke formation is achieved with simultaneous optimization of the investment and operating costs.
This object is achieved according to the invention in that the dehydrogenation or dehydrocyclization is performed on a catalyst, which, in addition to at least one alkali and/or alkaline earth promoter, comprises at least one metal compound of the elements of the third and/or fourth subgroups of the periodic table (excluding the elements with atomic numbers 58 to 71) as an additional promoter.
The catalyst according to the invention is distinguished by the characteristic feature that, despite its increased activity, coke formation and side reactions--such as, for example, multiple dehydrogenations, which, for example in the case of propane dehydrogenation, result in an undesirable formation of propadiene--are reduced to a minimum.
DESCRIPTION OF THE INVENTION
As suitable promoters from the group of alkali or alkaline earth compounds for the process of the invention there can be mentioned sodium, potassium, calcium or barium compounds. However, the results that can be achieved with cesium compounds as promoters are outstanding. Catalysts which contain 0.1 to 10, preferably 1 to 5, % by weight of a cesium compound, calculated as Cs.sub.2 O, have proven to be especially effective.
But catalysts according to the invention which as additional promoter contain a scandium, yttrium or lanthanum compound or a titanium, zirconium or hafnium compound, individually or in combination, have proven to be e
REFERENCES:
patent: 2249337 (1941-07-01), Visser et al.
patent: 2311979 (1943-02-01), Corson et al.
patent: 2371087 (1945-03-01), Webb et al.
patent: 2374404 (1945-04-01), Ahlberg
patent: 2380035 (1945-07-01), Edson et al.
patent: 2437532 (1948-03-01), Huffman
patent: 2668142 (1954-02-01), Strecker et al.
patent: 3114697 (1963-12-01), Bourne et al.
patent: 4151071 (1979-04-01), Myers
patent: 4347123 (1982-08-01), Mauldin et al.
patent: 4788364 (1988-11-01), Harandi
Versluis Frederik
Zimmermann Heinz
Griffin Walter D.
Linde Aktiengesellschaft
Sneed Helen M. S.
LandOfFree
Process and catalyst for dehydrogenation or dehydrocyclization o does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and catalyst for dehydrogenation or dehydrocyclization o, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and catalyst for dehydrogenation or dehydrocyclization o will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2209118