Chemistry of hydrocarbon compounds – Plural serial diverse syntheses – To produce aromatic
Reexamination Certificate
1998-11-04
2001-03-20
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Plural serial diverse syntheses
To produce aromatic
C525S319000, C525S320000, C525S323000, C525S485000, C525S486000, C525S488000
Reexamination Certificate
active
06204422
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
TECHNICAL FIELD OF INVENTION
BACKGROUND OF INVENTION
This invention relates to a process for producing dialkylnaphthalenes. More particularly, this invention relates to a process for producing high-purity diallylnaphthalenes from stock oils containing a substantial amount of naphthalene and/or alkylnaphthalenes, preferably for producing high-purity 2,6-dialkylnaphthalenes, in high yields from light cycle oils produced by catalytic cracking of petroleum.
PRIOR ART
In recent years, attention has been drawn to dialkylnaphthalenes as precursors of monomers for high performance polymers. In particular, 2,6-dialkylnaphthalenes are very important compounds as precursors of monomers for synthesis of polyethylene naphthalate (PEN), which have received attention as engineering plastics required to have a high level of mechanical properties, heat-resistance, stability against chemicals, and electrical and optical properties. They are also important as precursors of monomers for synthesis of fully aromatic liquid crystal polymers which have recently attracted special attention. Under these circumstances, supply of high-purity dialkylnaphthalenes, especially 2,6-diallylnaphthalenes, at low cost has been required in various industries.
Dialkylnaphthalenes are contained in coal tar and petroleum stock oils. These stock oils, however, contain, besides dialkylnaphthalenes, a large quantity of other components and impurities. Therefore, separation of dialkylnaphthalenes directly therefrom would result in low yields and high cost, and, in addition, would not provide high-purity dialkylnaphthalenes suitable for use in subsequent chemical synthesis without difficulty.
Further, in stock oils, a variety of hydrocarbon compounds having boiling points close to dialkylnaphthalenes are present. Therefore, selectively separating and extracting dialkylnaphthalenes alone has been technically and economically difficult.
The coal tar as the starting material is typically a by-product of blast furnace coke production in steelmaking industry. Adoption of advanced technology in steelmaking would lead to markedly reduced production of coal tar in the future. For this reason, supply of stock oils, alternative to the coal tar, would be increasingly required which are easily available and can be supplied at low cost.
On the other hand, dialkylnaphthalenes may be produced also by alkylation of naphthalene or monoalkylnaphthalenes. Naphthalene or monoalkylnaphthalenes as a starting material, particularly naphthalene or methylnaphthalene commonly used in industry, above all, &bgr;-methylnaphthalene, is mainly separated from coal tar. These naphthalene and monoalkylnaphthalenes separated from the coal tar contain a large quantity of impurities such as sulfur compounds and nitrogen compounds. Therefore, pretreatments, such as hydrodesulfurization and hydrodenitrogenation, should generally have been carried out to reduce the deactivation of catalysts caused by the impurities and to prevent the formation of alkylated compounds of the impurities. Disadvantageously, however, these pretreatments merely make the, stock oil alkylation process complicate, increase the cost, and, furthermore, cause yield loss due to hydrogenation of naphthalene ring.
Therefore, development of methods for efficiently synthesizing dialkylnaphthalenes, especially 2,6-dialkylnaphthalenes, above all, 2,6-dimethylnaphthalene, 2,6-isopropylmethylnaphthalene, and 2,6-diisopropylnaphthalene by alkylation of naphthalene or methylnaphthalene, especially &bgr;-methylnaphthalene, have been desired in industry. The technology, however, has not been satisfactorily established yet.
PROBLEMS TO BE SOLVED BY THE INVENTION
It is a general object of this invention to solve the above problems and to provide a rational technical process for producing dialkylnaphthalenes, especially 2,6-dialkylnaphthalenes, from petroleum stock oils which exist in abundance. It is a more specific object of this invention to establish a production process which has been enhanced in rationality of process and heat balance economics in the whole production process through effective utilization of naphthalene and/or alkylnaphthalenes contained in a large quantity in petroleum stock oils and, in a preferred embodiment, through the removal of catalytic poisons in the alkylation step, and consequently to provide a process for easily producing high-purity dialkylnaphthalenes in high yields at low cost.
MEANS FOR SOLVING THE PROBLEMS OF THE INVENTION
SUMMARY OF THE INVENTION
SUBJECT MATTER
The above objects can be attained by the following present invention.
Namely, the process for producing dialkylnaphthalenes according to this invention comprises the following steps:
(1) 1st step
the step of catalytically hydrodealkylating a stock oil containing a substantial amount of naphthalene and/or alkylnaphthalenes, separating a product oil from a product gas, and separating and recovering a fraction composed mainly of naphthalene and/or methylnaphthalene from the product oil;
(2) 2nd step
the step of catalytically alkylating or catalytically transalkylating the fraction, recovered in the 1st step, composed mainly of naphthalene and/or methylnaphthalene directly without pretreatment for purification, with an alkylating agent or a transalkylating agent to prepare alkylnaphthalenes;
(3) 3rd step
the step of separating and recovering dialkylnaphthalenes from the alkylnaphthalenes obtained in the 2nd step; and
(4) 4th step
the step of returning at least a part of the residual fraction, after the separation and recover of dialkylnaphthalenes in the 3rd step, as at least a part of the stock oil in the 1st step and/or at least a part of the alkylating agent or transalkylating agent in the 2nd step to the corresponding step.
EFFECT
The process for producing dialkylnaphthalenes according to this invention, comprising the 1st step of hydrodealkylating a stock oil, the 2nd step of directly alkylating (the term “alkylating” used herein including “transalkylating”) naphthalene and/or methylnaphthalene produced in the 1st step, the 3rd step of separating and recovering dialkylnaphthalenes from alkylnaphthalenes produced by the alkylation in the 2nd step, and the 4th step of returning the residual fraction, after the separation and recovery of the dialkylnaphthalenes, to the 1st step and/or the 2nd step, can realize the production of dialkylnaphthalenes in an economical and rational manner and can solve various problems involved in the prior art.
Namely, the process for producing dialkylnaphthalenes according to this invention has the following advantages over the process where hydrodealkylation and alkylation are separately conducted. According to the process of this invention, the utilization of alkylnaphthalenes contained in the stock oil can be increased because alkylnaphthalenes other than dialkylnaphthalenes as the target products, that is, by-products, can be reutilized as starting materials. Further, since the high temperature stream as such can be transferred to the next step, the number of process equipments, such as distillation column and heat-exchanger necessary in each step, can be reduced, so that the utilities consumption for heating up the feed stream and cooling down the product can be markedly reduced.
Furthermore, according to the hydrodealkylation step) in the process according to this invention, a hydrodealkylation catalyst having both hydrodesulfurization activity and hydrodenitrogenation activity is preferably used. This permits the hydrodesulfurization reaction and the hydrodenitrogenation reaction to satisfactorily proceed to produce hydrogen sulfide and ammonia which are then separated from the product oil by gas-liquid separation. Therefore, the poisoning of catalyst in the alkylation step can be prevented without provision of an additional desulfurization or denitrogenation step before the alkylation step.
Thus, according to the process of this invention, the alkylation can be advantageously carried out with high selectivity in high yields.
REFERE
Fujii Masaki
Kubota Osamu
Okada Shin-ichi
Sasaki Takumi
Satou Yoshitaka
Fuji Oil Company Ltd.
Griffin Walter D.
Wenderoth , Lind & Ponack, L.L.P.
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