RU2698302C1 - Plant for processing aliphatic hydrocarbons c2-c12 using zeolite-containing catalysts - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to an apparatus for processing aliphatic hydrocarbons C₂-C₁₂ using zeolite-containing catalysts. Plant is characterized by that it ensures continuous operation mode of parallel functioning three and more single-layer reactors, each of which is equipped with an individual heating furnace, a recuperative heat exchanger and a cooler.

EFFECT: use of the proposed apparatus increases the quality of the obtained product, as well as increases efficiency of using the equipment.

1 cl, 1 dwg

Description

The invention relates to plants for the processing of aliphatic hydrocarbons (lower paraffins and C ₂ -C ₁₂ olefins) using zeolite-containing catalysts and can be used in oil refining and petrochemicals.

Processing of C ₃ -C ₁₂ lower paraffins (mainly C ₃ -C ₈ ) to produce aromatic hydrocarbons (primarily benzene - toluene - xylene fraction (BTK - fraction) or high-octane gasolines in the processing of low-octane gasoline fractions or joint processing of low-octane gasoline fractions and oxygenates, in particular methanol, as well as C ₂ -C ₁₂ olefins (mainly C ₂ -C ₆ ) in order to obtain the components of high-octane gasolines AI - 92, AI - 95, AI - 98 and diesel fractions (oligomerization of olefins) or BTK - fraction (Aromatization of olefins) is carried out on an industrial scale is currently using zeolite catalysts (primarily using the zeolite group pentasil (ZSM - 5, ZSM - 11, etc.) or elementosilikatov zeolite structure).

The Cyclar process of the British Petroleum and UOP firms for the aromatization of C ₃ -C ₄ paraffins (Oil and Gas Technologies, No. 8, 2005, p. 81) is carried out using the modified silica zeolite of the pentasil group modified metal promoters - zinc and gallium. The Z-forming process of Mitsubishi Oil and Chioda Corporation (Japan) of the aromatization of the pentane-hexane fraction (Z-forming process: conversion of LPG and light naphtha to aromatics, 1992, NPRA ANNUAL MEETING, march 22- 24, 1992, Marriot / Sheraton, New Orleans, Louisiana, Chiyoda Corporation) proceeds using a metallosilicate catalyst (US Pat. No. 4,709,494, 1987). A similar process was developed by Japanese firms Shova Shell and Tomoyuki Inui (A.Z. Dorogochinsky, A.L. Proskurnin, S.N. Ovcharov, N.N. Krupina "Aromatization of low molecular weight paraffin hydrocarbons on zeolite catalysts", M. , TsNIITENeftekhim, 1989, p. 73). The process of joint processing of low-octane gasoline fractions and methanol or other alcohols or ethers (US Pat. RF No. 138334, 2013) is also carried out on a catalyst based on a zeolite of the pentasil group.

The processes of oligomerization of C ₃ -C ₄ olefins into components of high-octane gasolines AI - 95 - AI - 98 (the MOGD process of Mobil Oil Corp. (Oil, Gas, and Petrochemicals Abroad, No. 9, 1985, p. 67-70), as well as the domestic process according to (Pat. RF No. 2135547, 1998) is carried out using zeolites of the ZSM-5 or ZSM -11 type modified with zinc oxide.

A distinctive feature of all of the above processes is the relatively short service life of the used zeolite-containing catalysts until they are completely coked (coke, i.e. carbon deposits, in the cavities and channels of the zeolite). Depending on the raw materials used and the desired end products, it amounts to 300 to 700 hours for aromatization of paraffins and olefins and oligomerization of olefins in one continuous operation cycle. Then follows the process of oxidative regeneration of the catalyst, which in industrial conditions lasts 120-150 hours.

To organize the continuous operation of the processes of aromatization of paraffins and olefins or the oligomerization of olefins, two technological threads are provided for in the technological schemes of these processes, one of which is operated in the synthesis mode, and the other at the same time in the oxidative regeneration mode. After complete coking of the catalyst operating in the synthesis mode, the operation of this catalyst switches to the regeneration mode, and the regenerated catalyst is included in the synthesis mode.

In order to achieve complete conversion of raw materials, a multi-shelf adiabatic reactor (Pat. RF No. 2277524, 2004) is provided in each process line of the paraffin aromatization unit with separation of the obtained aromatic hydrocarbons from the feed stream between the shelves or several (usually four) located one after another reactors (in processes "Cyclar" and "Z - forming") with an intermediate supply of heat between the shelves or reactors (the aromatization reaction of paraffins is highly endothermic). Heat can be supplied by passing the raw material - product flow through the coils of the intermediate fuel furnaces (in the Cyclar and Z-forming processes), through the annular space of tubular heat exchangers with molten salts in the pipe space and its fuel furnace, by electrically heating the reaction zone, circulating dry food containing hydrogen and fatty gases (US Pat. RF No. 2185359, 2000, No. 2277524, 2004).

For the complete conversion of raw materials, each process line of the olefin oligomerization unit is provided with a multiband adiabatic reactor according to (Pat. RF No. 2206384, 2002) with one catalyst on each shelf, or one tubular or in series two tubular reactors with different catalysts, or at least three adiabatic oligomerization reactors with one or two different catalysts (US Pat. RF No. 2191204, 2001). Since the oligomerization reaction of olefins is highly exothermic, direct heat exchange with cold gas is usually used to cool the reaction stream between the shelves in the adiabatic reactor or between the reactors, which allows one to quickly reduce the temperature of the reaction stream (US Pat. RF No. 2206384, 2002).

Existing process flow diagrams for the aromatization of paraffins with two two-four-layer endothermic reactors (US Pat. RF No. 2139844, 1998, No. 2175959, 2000, No. 2277524, 2004) or the oligomerization of lower olefins with two four-layer exothermic reactors (US Pat. RF №2135547, 1998 - the technological scheme for the oligomerization of olefins, No. 2206384, 2002 - the oligomerization reactor), which provide for alternating operation of the reactors in the synthesis and regeneration mode, have several disadvantages:

1. The process of hydrocarbon synthesis takes more than 300 hours, and the regeneration of the catalyst -120-150 hours. Therefore, the technological equipment: the reactor, compressor, separators and furnace that were involved in the regeneration stage, stand idle for at least 150 hours (in the case of operation on a fresh catalyst).

2. The synthesis reactions (oligomerization and aromatization of olefins) and oxidative regeneration are exothermic reactions. Therefore, to remove excess heat before the second, third and fourth layers of the catalyst in the synthesis and regeneration, it is necessary to apply quenching or steam, respectively. The increase in ballast flows leads to a deterioration in the economic performance of the installation, as these flows should subsequently be cooled, separated and removed from the installation.

3. The aromatization reaction of paraffins is endothermic. Additional heating of gas flows between the shelves of the adiabatic reactor, i.e. additional energy consumption.

4. The design of a four-layer reactor with mother liquors - distributors of cooling or heating flows is quite complicated and metal-intensive.

5. The cost of the technological scheme with reactors containing four-layer catalyst layers increases due to the fact that:

- the costs of ballast flows must be controlled and regulated;

- shutoff blocks for switching synthesis and regeneration flows should be installed on hot flows with a temperature of more than 520 ° С.

6. The quality of the liquid products of aromatization and oligomerization reactions (their chemical and fractional compositions) differs significantly at the beginning and at the end of the synthesis cycle.

7. The synthesis of finished products ceases during the time required to switch the reactors.

Close to the claimed installation is a comprehensive installation for processing a mixture of gasoline fractions and methanol in order to obtain high-octane gasoline (US Pat. RF No. 138334, 2013). The installation according to this method includes two adiabatic reactors technologically connected with equipment for heating raw materials, cooling, partial condensation, separation and rectification of reaction products, and characterized in that each reactor includes at least two stationary catalyst beds, with the possibility of feeding into the raw material mixture, as well as in the second and each subsequent layer of the part of the gas that was heated in the fire heater that was released in the three-phase separator from the stream of reaction products after their partial condensation. This installation also includes a regeneration circuit consisting of a furnace, a circulation compressor and a separator.

Closest to the claimed installation is a device for oligomerization of lower olefins in order to obtain high-octane gasoline, described in US Pat. RF №2135547, 1998. In a multilayer reactor, the raw materials are contacted with an oligomerization catalyst containing a zeolite of the pentasil group under oligomerization conditions to form a stream enriched in C ₅₊ hydrocarbons, which, in order to isolate a stream containing C ₃₊ hydrocarbons, and a lung stream hydrocarbons are cooled, passed through a separator and the liquid phase is fractionated from the separator, and the stream containing C ₃₊ hydrocarbons is fractionated to produce C ₅₊ gasoline, C ₃ hydrocarbon fraction and C ₄ hydrocarbon fraction, characterized in that the light hydrocarbon stream contains C ₁ -C ₄ components and part of this stream and part of the C ₄ hydrocarbon fraction are sent to be mixed with the olefin-containing feed. The installation also includes a regeneration circuit consisting of a furnace, a circulation compressor and a separator.

An improved installation is proposed for carrying out the conversion processes of C ₂ -C ₁₂ aliphatic hydrocarbons (conversion of low-octane gasolines, aromatization of paraffins and olefins, oligomerization of olefins) on zeolite-containing catalysts. The essence of the proposed installation is that instead of a two-reactor scheme with two or more layer loading of the catalyst, three or more single-layer reactors are provided, each with its own individual heating furnace (the installation scheme is shown in Fig. 1). At the same time, one of these reactors simultaneously operates in the regeneration mode, and the rest in the synthesis mode.

A plant for processing aliphatic hydrocarbons C ₂ -C ₁₂ (conversion of low octane gasolines, aromatization of paraffins and olefins, oligomerization of olefins) using zeolite-containing catalysts with activity changing during operation in the synthesis mode is claimed, characterized in that it is used to increase the plant’s performance and improve the quality obtained liquid products, increasing the efficiency of using technological equipment and improving the economic performance of the installation on ensure continuous operation of three or more single-layer reactors operating in parallel, each of which is equipped with an individual heating furnace.

The installation described above is also characterized in that at the same time one of these reactors is operating in the regeneration mode, and the rest in the synthesis mode.

Given that the synthesis of a hydrocarbon product prior to the regeneration of zeolite-containing catalysts of all the above processes lasts for at least 360 hours on an equilibrium catalyst, this process, depending on the activity of the catalyst, can conditionally be divided into three stages of run: the first from 0 to 120 hours - highly active catalyst;

2nd from 120 to 240 hours — medium activity catalyst;

3rd from 240 to 360 hours - low activity catalyst.

Three reactors in synthesis mode at different stages of catalyst run and one reactor in regeneration mode are equivalent in power to two four-layer adiabatic reactors, but they do not have the above disadvantages.

The technological scheme of the proposed process provides:

1. Constant quality of the obtained product, since the liquid products of the aromatization or oligomerization processes from the three reactors are mixed in the product tank and averaged over the composition.

2. The temperature control of raw materials supplied to each reactor depending on the activity of its catalyst is ensured by adjusting the temperature of the raw materials at the outlet of the preheater furnaces, which provides optimal conditions for reactions in the catalyst bed and does not require additional supply of quenching or steam to the reactor for removing excess heat.

3. The raw material flows supplied to the reactors are stabilized by correcting the tasks for the pressures of the raw materials entering the heat exchangers. Since the consumption of raw materials in this case does not depend on the degree of coking of the catalyst layers, the same load is ensured in all reactors operating in the synthesis mode.

4. Blocks of shutoffs for switching the flows of raw materials for synthesis and regeneration, as well as control valves do not require a special high-temperature design, since they are installed on cold streams (30-200 ° C).

The operation of the inventive installation, shown in the diagram (Fig. 1) on the example of four reactors, can be illustrated as follows.

A mixture of raw materials from tank 1 (stream 51) and recycle from tank 2 (stream 52) is supplied by pumps 9/1 and 9/2 in a predetermined ratio (stream 56) to a mixing unit with a hydrogen-containing gas (HSG). The resulting stream (stream 57) is supplied for heating to three of the four existing heat exchangers (11, 21, 31, 41), in which the product stream is the heat carrier. After heating the raw material, it is heated in three of four existing furnaces (12, 22, 32, 42) to a predetermined temperature and fed into three of four existing reactors (13, 23, 33, 43), which operate in the synthesis mode. In these reactors, the raw material contacts the oligomerization catalyst, resulting in product streams enriched in C ₅₊ hydrocarbons. The product leaving the reactors is cooled in three of the four existing heat exchangers (11, 21, 31, 41) and in three of the four existing air coolers (14, 24, 34, 44). A refrigerated and partially condensed stream (stream 60) from the three reactors is sent to a separator 5. The balance amount of hydrogen-containing gas (stream 63) and the liquid phase (stream 64) is pumped to the stabilization column by pump 10. The circulating VSG (stream 62) enters the separator 3, mixes with fresh hydrogen (stream 53), and then the gas mixture is fed to the compressor inlet 4.

The synthesis process with a decrease in the activity of the catalyst in the reactors is carried out with a rise in the temperature of the feed at the inlet of the reactor. The decrease in catalyst activity is due to the formation of coke, which is formed during the conversion of hydrocarbons in reactors. The rate of coke formation depends on the composition of the feed and the process conditions. Coke is periodically burned in an oxygen-containing gas to form carbon oxides and water. A mixture of nitrogen and air is used as a regenerating gas. To control the rate of burning of coke from the catalyst, accompanied by significant heat, a predetermined amount of oxygen is maintained in nitrogen. This prevents the structural changes of the catalyst and its irreversible deactivation.

After the completion of the synthesis mode, one of the three reactors with the most coked, i.e. the most inactive catalyst, which has been in the synthesis mode longer than the other two, is connected to the regeneration circuit. A mixture of nitrogen (stream 54), air (stream 55) and recycle gas (stream 66) from the separator 6 enters the compressor 8, and then is fed to the heat exchanger for heating. In a heat exchanger, the nitrogen-air mixture (ABC) is heated by a stream of regeneration gases from the reactor, and then heated to a predetermined temperature in the furnace. After heating, ABC is fed to the reactor in which contact with the catalyst occurs. The product stream leaving the reactor is cooled in a heat exchanger and in an air cooler. Partially condensed (stream 61) is sent to a separator 6, from which the balance amount of gas is withdrawn (stream 65), and the rest of the gas (stream 66) is directed to a separator 7. At the same time, water (stream 67) separated in the process of gas stream separation in the separators 3, 5, 6 and 7, dumped into the drainage.

Oxidative regeneration is carried out with a stepwise increase in temperature by increasing the fuel supply (stream 68), while increasing the oxygen concentration in the regenerating gas from 0.5 to 21% vol. Burning coke leads to an almost complete restoration of the activity of the catalyst. This process is carried out periodically. During the regeneration process, contact of the feed with the catalyst is not allowed.

The decrease in the activity of the zeolite-containing catalyst also occurs as a result of the formation of unsaturated polymer hydrocarbon molecules that are not coke, but adsorbed in the pores of the zeolite and block its active surface. Between oxidative regenerations, in order to increase the activity of the catalyst, it is possible to carry out its treatment with a stream of inert or hydrogen-containing gas at an elevated temperature. Periodic reactivation of the zeolite-containing catalyst for oligomerization of olefin-containing raw materials upon their contact with an inert or hydrogen-containing gas at a temperature of 20-50 ° C higher than the contact temperature of the raw materials with the catalyst allows to increase the duration of the catalyst between oxidative regenerations. The duration of contact of the catalyst with a hydrogen-containing gas is determined by the properties of the catalyst and the contact conditions and ranges from 2 to 10 hours.

Claims (2)

1. Installation for the processing of aliphatic hydrocarbons C ₂ -C ₁₂ using zeolite-containing catalysts, characterized in that it provides continuous operation in parallel with three or more single-layer reactors, each of which is equipped with an individual heating furnace, a regenerative heat exchanger and a refrigerator. 2. Installation according to claim 1, characterized in that at the same time one of these reactors works in the regeneration mode, and the rest in the synthesis mode.

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