Chemistry: fischer-tropsch processes; or purification or recover – Liquid phase fischer-tropsch reaction
Reexamination Certificate
1999-10-01
2001-10-09
Vollano, Jean F. (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
Liquid phase fischer-tropsch reaction
C518S702000, C518S704000, C518S712000, C422S198000
Reexamination Certificate
active
06300380
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a production process for methanol, more specifically to a production process for methanol in which a reactor having a structure capable of efficiently removing generated heat is used in a methanol synthesis step in producing methanol to inhibit by-products from being formed, whereby a compact distillation step (distillation system) is achieved.
DESCRIPTION OF RELATED ART
As shown, for example, in Japanese Patent Application Laid-Open No. 1-180841, a conventional process for producing methanol (CH
3
OH) from hydrocarbon comprises usually the following steps (1) to (3). That is, they are:
(1) a synthetic gas production step in which gaseous hydrocarbon or vaporized liquid hydrocarbon reacts with steam in a reforming furnace at 800 to 1000° C. in the presence of a nickel base catalyst to produce synthetic gas comprising main components of hydrogen (H
2
), carbon monoxide (CO) and carbon dioxide (CO
2
);
(2) a synthesis step in which the synthetic gas described above reacts on a copper base methanol synthesis catalyst at a pressure of 50 to 150 atm and a temperature of 200 to 300° C. and resulting crude methanol is recovered from the reaction gas in the form of liquid; and
(3) a distillation step in which liquid crude methanol is distilled in a distillation column comprising a single column or two or more columns to separate refined methanol from waste water containing organic compounds having lower boiling points than that of methanol (hereinafter referred to as low boiling organic compounds), organic acids and organic compounds having higher boiling points than that of methanol (hereinafter referred to as high boiling organic compounds).
In the synthesis step (2) described above, methanol (CH
3
OH) is produced from carbon monoxide (CO) contained in the synthetic gas, and methanol (CH
3
OH) and water (H
2
O) are produced from carbon dioxide (CO
2
). Impurities such as dimethyl ether, ethanol and the like are formed by side reaction in this synthesis step.
These impurities and water are contained in liquid crude methanol together with intended methanol but separated from methanol in the subsequent distillation step (3). In this case, there used to be involved the problem that if a lot of the impurities are contained, facilities for separation and refining in the distillation step are complicated and expanded in a size.
Various reactors having means and structures for controlling an increase in a gas temperature caused by an exothermic reaction during operation when carrying out synthesis by an exothermic reaction in the presence of a solid catalyst are devised for the reactor used in the synthetic step (2) described above. In this case, there has been the problem that as apparent from an effect of a temperature against a methanol equilibrium concentration, an increase in the temperature is accompanied with a reduction in the methanol equilibrium concentration in a methanol synthesis reaction to damage the profitability of the industrial plant.
On the other hand, even if a catalyst is used, the reaction rate is limited and reduced as the temperature is lowered, and therefore operation is desirably carried out in a proper temperature range from an industrial point of view considering the catalyst performance. For example, when methanol is synthesized from mixed gas comprising significant substances of hydrogen, carbon monoxide and carbon dioxide using a copper base catalyst, a temperature of 220 to 280° C. is considered to be appropriate. Further, a pressure of 50 to 300 kg/cm
2
.G is considered to be an economically proper pressure range for the pressure (total pressure) of gas. However, they are variable depending on an improvement in the catalyst.
OBJECT AND SUMMARY OF THE INVENTION
In light of the problems described above, the present inventors have made intensive investigations in order to develop a production process for methanol which can efficiently remove heat generated in a methanol synthesis reaction and which makes it possible to reduce the size of the distillation step (distillation system) by inhibiting by-products from being formed.
As a result thereof, the present inventors have found that such problems can be solved by using a reactor having a specific structure in a methanol synthesis step in producing methanol, in which an inner tube and a central tube are disposed in a reaction tube in the reactor and a granular catalyst is charged into a circular space surrounded by the reaction tube and the inner tube and in which the above central tube is disposed almost in the center of a shielding plate provided at the upper end of the reaction tube. The present invention has been completed from such point of view.
That is, the present invention provides a production process for methanol comprising a synthetic gas production step in which hydrocarbon reacts with steam to generate synthetic gas comprising main components of hydrogen, carbon monoxide and carbon dioxide, a methanol synthesis step in which the synthetic gas described above reacts on a methanol synthesis catalyst and resulting crude methanol is recovered in the form of liquid, and a distillation step in which recovered crude methanol described above is distilled to be separated into waste water containing low boiling organic compounds and high boiling organic compounds and refined methanol, wherein used in the methanol synthesis step described above is a reactor which comprises a reaction tube, an inner tube closed at a lower end thereof disposed almost in the center of the reaction tube, a central tube in which unreacted feed gas flows disposed almost in the center of the above inner tube, and a circular catalyst layer charged with a granular catalyst disposed in a circular space surrounded by the reaction tube and the inner tube and in which the central tube described above is disposed almost in the center of a wholly or partially detachable shielding plate disposed at the upper end of the reaction tube. Usually disposed are an unreacted gas-feeding room at the upper part of the reaction tube in the reactor described above and a lower collecting room for reaction gas at the lower part of the reaction tube.
Further, the present invention provides a reactor for methanol synthesis, wherein plural reaction tubes are disposed in the inside thereof; an inner tube closed at a lower end thereof is disposed almost in the center of the reaction tube; a central tube is disposed almost in the center of the inner tube; a circular space surrounded by the reaction tube and the inner tube is constituted as a granular catalyst-charged part; a shielding plate in which at lest one of the whole and a part thereof is detachable is disposed at the upper end of said reaction tube; said central tube is connected almost to the center of the shielding plate; fed unreacted gas flows downwards from the upper part of the central tube to flow into the inner tube from the lower outlet of the central tube; and further, said unreacted gas flows upwards through a circular duct surrounded by the inner tube and the reaction tube and flows downwards from the upper part of the granular catalyst-charged part.
The production process of the present invention comprises a synthetic gas production step, a methanol synthesis step and a distillation step, and refined methanol is produced by passing in order through these steps.
The reactor used in the methanol synthesis step is provided with the inner tube closed at a lower end thereof disposed almost in the center of the reaction tube, and the central tube is disposed almost in the center of the inner tube to form a granular catalyst-charged layer in a circular space surrounded by the reaction tube and the inner tube. This allows unreacted gas which is synthetic gas to flow downwards through the upper part of the central tube from the unreacted gas-feeding room and flow into the inner tube from the lower exit of the central tube. Then, the unreacted gas flows upwards through a circular duct surrounded by the inner tube and the central tube, and subs
Kobayashi Kazuto
Nagai Hideaki
Ohira Hiroshi
Osara Hiroyuki
Anderson Kill & Olick P.C.
Mitsubishi Heavy Industries Ltd.
Parsa J.
Vollano Jean F.
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