A process, unit and reaction system for dehydrogenation of low carbon alkane

Abstract

The invention relates to a process, unit and reaction system of low-carbon alkane dehydrogenation, which comprises the following steps: C3-C5 low-carbon alkane feed gas, together with CO and/or CO.sub.2 process gas, get into reactor after being preheated to 200-500° C., contact with a Cr—Ce—Cl/Al.sub.2O.sub.3 dehydrogenation catalyst, a Cu—Ce—Ca—Cl/Al.sub.2O.sub.3 thermal generating agent and thermal storage/support inert alumina balls, and convert to dehydrogenation products for 5-30 minutes under the conditions: temperature, 500-700° C., pressure, 10-100 kPa and weight hourly space velocity (WHSV), 0.1-5 hours.sup.−1. The products formed enter the downstream separation unit for separating out the low-carbon alkenes. The periodic regeneration process of the catalyst bed includes steam purging, hot air regenerating, bed heating, evacuating and reducing at 560 to 730° C. and 0.01 to 1 MPa. Each cycle needs about 10-70 minutes. With such dehydrogenation process, the reaction heat balance is moderated, and temperature gradient and reaction severity in the catalyst bed are reduced. As a consequence, the catalytic conversion, product selectivity, operation cycle and service life are improved. The system energy consumption is reduced.

Claims

1. A process for dehydrogenating low-carbon alkanes, the process comprising: (1) pre-heating C3-C5 low-carbon alkane feed gas, CO and/or CO.sub.2 process gas to 200-500° C.; (2) introducing the preheated mixture gas into a reactor and getting contact for 5-30 minutes with a Cr—Ce—Cl/Al.sub.2O.sub.3 dehydrogenation catalyst, a Cu—Ce—Ca—Cl/Al.sub.2O.sub.3 thermal generating agent, and heat storage/support inert alumina balls, and converting to products under the reaction conditions: temperature 500-700° C., pressure 10-100 kPa and WHSV 0.1-5 hour.sup.−1; (3) separating out the low-carbon alkenes and by-products in a separation unit and obtaining the low-carbon alkenes, hydrogen-rich gas and burning gas (used for heating), and recycling the unreacted low-carbon alkane back to the reactor. (4) periodically regenerating the catalyst bed via purging with steam, heating the catalyst bed with 560-730° C. and 0.01-1 MPa hot air, evacuating, and reducing with H.sub.2-rich gas stream. The cycle takes about 10-70 minutes.

2. The process of claim 1, wherein the dehydrogenation reaction and catalyst bed regeneration conditions are: pre-heating temperature, 300-450° C., dehydrogenation reaction temperature, 540-650° C., and pressure, 20-70 kPa, reaction time, 10-20 minutes, and WHSV 0.3-2 hour.sup.−1, and regenerating 600-700° C. hot air and pressure 0.05-0.5 MPa, with the whole cycle taking 20 to 35 minutes.

3. The process of claim 1, wherein the consumed time ratio in a single reaction-regeneration cycle, dehydrogenation:steam purge:hot air heating:vacuum/reduction is 1:(0.2-0.4):(0.8-1.1):(0.2-0.4).

4. The process of claim 1, wherein the low-carbon alkane is propane, isobutane or n-butane, or their mixture.

5. The process of claim 1, wherein the Cr—Ce—Cl/Al.sub.2O.sub.3 dehydrogenation catalyst contains 18-30 mol % Cr.sub.2O.sub.3, 0.1-3 mol % CeO.sub.2, 0.1-1 mol % Cl, and 67-80 mol % Al.sub.2O.sub.3.

6. The process of claim 1, wherein the Cu—Ce—Ca—Cl/Al.sub.2O.sub.3 heat generating agent contains 5 to 30 mol % CuO, 0.1 to 3 mol % CeO.sub.2, 10 to 35 mol % CaO, 0.1 to 1 mol % Cl and 50 to 80 mol % Al.sub.2O.sub.3.

7. The process of claim 1, wherein the proportion of the process gas CO and/or CO.sub.2 in the low-carbon alkane feed is 1-20 mol %.

8. The process of claim 1, wherein the filling volume ratio of the dehydrogenation catalyst, the heat generating agent, the heat storage inert alumina balls and the supporting balls is 1:(0.1-0.2):(0.4-0.7):(0.4-0.6).

9. A unit for dehydrogenating low-carbon alkanes, the unit consisting: a raw material preheating furnace and an air preheating/heating furnace connected to the reactors by process pipes; 3-8 parallel fixed bed reactors controlled by program-controlled valves to make the reactors rotate at a state of reaction, regeneration and purging; the series separation equipment connected to the outlet of the reactors used for separation of reaction products; the compression and gasification equipment connected to the process pipeline used for hydrocarbon respectively; the heat exchanger, condenser and HRSG in the process pipeline respectively used for heat exchange, condensation and heat recovery of raw materials, process gas, products and exhaust gas of the reactors.

10. A dehydrogenation reaction system, the system consisting: heating equipment, reactor, separation equipment, reaction feedstock, process gas, catalyst, heat generating agent, heat storage inert alumina ball and inert alumina ceramic ball, where in the dehydrogenation reaction stage, low-carbon alkane and process gas enter the reactor from the top of the reactor after preheating and contact with dehydrogenation catalyst, heat generating agent, heat storage inert alumina ball and inert ceramic alumina ball, and convert to products under the dehydrogenation reaction condition which are discharged from the bottom of the reactors to the connected rear section separation unit to separate out the low-carbon olefin, hydrogen rich gas and burning gas; the unconverted low-carbon alkane is recycled back to the reactor; where in the regeneration stage, feeding is stopped first, the catalyst bed is purged with steam, and then heated hot air enters from the top of the reactor and regenerates the catalyst and raises the bed temperature.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0042]

[0043] FIG. 1. The process flow diagram of low-carbon alkane dehydrogenation.

[0044] where 1—feed heating furnace; 2—reactor under reaction; 3—regenerator under reaction; 4—reactor under purging; 5—flash separation tank; 6—de-ethane tower; 7—product separation tower; 8—air heating furnace; 9—product compressor; 10—gasifier; 11—raw low-carbon alkane; 12—process gas; 13, 20, 21—burning gas; 14—hydrogen-rich gas; 15—product low-carbon olefins; 16—recycle low-carbon alkanes; 17—air; 18—waste heat boilers; 19—exhaust gas; 22, 23, 27, 28, 29—heat exchangers; 24—coolers; 25, 26—condenser; 30—process pipe.)

[0045] FIG. 2. The structure diagram of fixed bed reactor for low-carbon alkane dehydrogenation

[0046] where 31—catalyst bed; 32—catalyst bed refractory brick floor; 33—catalyst bed bottom refractory brick arch support; 34—fixed-bed reactor refractory lining; 35—reactor carbon steel shell; 36—low-carbon alkane feedstock inlet; 37—hot air inlet; 38—steam, process gas and reducing gas inlet; 39—hydrocarbon product outlet; 40—waste hot air outlet; 41—evacuation port; 42—air drying device; 43 —feed inlet deflectors; 44, 45—three-point thermocouples in the catalyst bed; 46, 47, 48, 49, 50, 51—programmed valves.

DETAILED IMPLEMENTATION

[0047] With the help of the schematic diagrams it is clear that the invention provides an alkane dehydrogenation reaction process, an alkane dehydrogenation unit and a specific implementation of dehydrogenation reaction system which includes reaction unit, reaction feed, catalyst and thermal coupling additive.

[0048] FIG. 1 is a flow chart of a low-carbon alkane dehydrogenation reaction process provided by the invention, and also a schematic diagram of a low-carbon alkane dehydrogenation reaction unit and reaction system.

[0049] FIG. 2 is the structure diagram of fixed bed reactor for low-carbon alkane dehydrogenation.

[0050] As shown in FIG. 1, the alkane dehydrogenation process unit of the invention includes: feed preheating furnace, air preheating furnace, and heating furnace which are connected to the reactor via process pipelines; 3-8 side-by-side fixed-bed reactors are controlled by program-controlled valves, which are used to keep the reactor rotation at different states such as reaction, regeneration and purging; an in-series separation unit connected to the reactor outlet is used for product separation; Compression and gasification equipment are used for the compression, circulation and gasification of air, product, process gas and burning gas respectively; Additionally, it also includes heat exchanger, condensation equipment and waste heat boiler connected via pipelines in the process for heat exchange, condensation and heat recovery of feed, products and recycle materials.

[0051] In the alkane dehydrogenation process of the invention, the reaction conversion process includes: low-carbon alkane feed gas 11, process gas 12 accounting for 1-20 mol % of low-carbon alkane feed gas, through process pipeline 30, preheating by heat exchanger 22, 27 and heating furnace 1 to 200-500° C., entering reactor 2 in reaction state from the top of the reactor; unconverted low-carbon alkane 16 and fresh feed gas 11 enter the reactor together; contact with chromium alumina dehydrogenation catalyst in fixed bed reactor 2, thermal coupling additive, inert heat storage alumina balls and supporting inert alumina ceramic balls.

[0052] Under the conditions of reaction temperature 500-700° C., reaction pressure 10-100 kpa, and mass space velocity (WHSV) 0.1-5 h.sup.−1, the reaction takes place and the reaction time is 5-30 min.

[0053] In the aforementioned single cycle, the time ratio of the dehydrogenation reaction, steam purging, catalyst bed heating and vacuum pumping/reduction is 1: (0.2-0.4): (0.8-1.1): (0.2-0.4).

[0054] The low-carbon olefins and by-products generated by the reaction are discharged from the lower part of the fixed bed reactor, heat-exchanged through heat exchanger 29 to generate steam, and further heat-exchanged with the heat exchanger 22 and the feed 11 and 16, then cooled with the condenser 25, and compressed with the product compressor 9 and further cooled and condensed with the condenser 26, and then entering into the subsequent separation unit 5, 6, 7 and 24 to separate out the low-carbon olefins 15, hydrogen rich gas 14 and side-products as burning gas gas 20 and 21. A part of the by-product burning gas 13, the unconverted low-carbon alkane 16, together with the fresh feed 11, passes through the full heat exchange (heat exchanger 22) and (heating furnace 1) heats up, and then circulates back to the reactor 2 at the reaction state for further conversion.

[0055] The conversion process includes the periodic regeneration process of the catalyst bed (31 in FIG. 2), which, through a set of program-controlled valves (46, 47, 48, 49, 50, 51 in FIG. 2), 3-8 fixed bed reactors are controlled to be at different states (reaction 2, purging 4 and regeneration 3); after the reaction conversion, the catalyst bed 31 stops feeding, and after the steam purging (reactor 4 at the purging state), 560-730° C. and 0.01-1 MPa hot air enters the catalyst bed 31 for regeneration (reactor 3 at the regeneration state). The high temperature hot air is formed in the furnace 8 by air 17 and burning gas 21 after being gasified in the gasifier 10 and heat exchanged in the heat exchanger 23 before entering into the reactor 3 (reactor at the regeneration state). The high-temperature hot stream flows through the catalyst bed 31 in the reactor 3 at the regeneration state, then passes through the heat exchanger 28 to exchange the heat to generate steam, and after heat exchange in the heat exchanger 23 with cold air, the remaining heat is recovered via the waste heat boiler 18 and then vented 19.

[0056] After completing the regeneration process of the catalyst bed 31, the reactor goes to evacuation and reduction states, and then the dehydrogenation process is repeated; Each cycling time takes 10-70 minutes. The aforementioned reduction process includes a flash separation in the flash separation tower 5, and the hydrogen-rich gas 14 obtained in the cold box 24 (further separation if a PSA separation is employed) is used to reduce the catalyst bed 31 in the reactor 3 at the regeneration state. The catalyst bed 31 is packed with the dehydrogenation catalyst, the thermal coupling additive, the heat storage inert alumina balls and the supporting inert alumina ceramic balls having a volume ratio of 1: (0.1-0.2): (0.4-0.7): (0.4-0.6).

[0057] In the dehydrogenation process and reaction system of low-carbon alkanes provided by the invention, the Cr—Ce—Cl/Al.sub.2O.sub.3 dehydrogenation catalyst in the catalyst bed 31 may be prepared following the steps and procedures given in the inventor's granted patent ZL200910210905.0, but the Cr—Ce—Cl/Al.sub.2O.sub.3 dehydrogenation catalyst of the invention has the composition of 18˜30 mol % Cr.sub.2O.sub.3, 0.1˜3 mol % CeO.sub.2, 0.1˜1 mol % Cl and 67˜80 mol % Al.sub.2O.sub.3.

[0058] In the dehydrogenation process and reaction system of low-carbon alkanes provided by the invention, the Cu—Ce—Ca—Cl/Al.sub.2O.sub.3 thermal coupling additive in the catalyst bed 31 can be prepared following the steps and procedures in the inventor's pending patents, application numbers 201711457256.5 and 201810119334.9; but the Cu—Ce—Ca—Cl/Al.sub.2O.sub.3 thermal coupling additive of the invention contains 5-30 mol % of CuO, 0.1-3 mol % of CeO.sub.2, 10-35 mol % of CaO and 50-80 mol % of Al.sub.2O.sub.3.

[0059] In the dehydrogenation process, unit and reaction system of low-carbon alkane provided by the invention, the heat storage inert alumina balls and the supporting inert alumina ceramic balls in the catalyst bed 31 have a composition of Al.sub.2O.sub.3≥99.5 mol %, a heat capacity of 0.2 to 0.35 cal/g° C., and a maximum use temperature of more than 1400° C., as an effective heat accumulator with guaranteed stability under harsh environments.

[0060] In the dehydrogenation process, unit and reaction system of low-carbon alkane provided by the invention, the reaction feed 11, 16 and the process gas 12 enter the reactor with carbon steel shell 35 and refractory lining 34 via the upper hydrocarbon inlet 36 and steam/gas inlet 38 of the reactor shown in FIG. 2, being guided by the feed inlet guide plate 43 and pass through from top to bottom the catalyst bed 31 supported by the arch support of refractory brick 33 and located on the refractory brick floor 32; The temperature change of catalyst bed is detected by the three-point thermocouple 44 and 45 in the bed; The reaction products are discharged from the lower part of the reactor via the hydrocarbon outlet 39, pass through the heat exchanger 29 and 22, cooler 25, compressor 9 and condenser 26, and then enter the subsequent separation equipment 5, 6, 7 and 24 for separation.

[0061] In the regeneration stage, after stopped the feed 11, 16 and 12, the steam enters the reactor (reactor 4) which is at the purging state from the inlet 38, purges from the top to the bottom the residual hydrocarbon in the catalyst bed 31 and discharges out from the outlet 39 at the bottom of the reactor; After that, the high-temperature hot air being dried by the air drying device 42 enters the reactor at the reducing state from the inlet 37 (Reactor 3) and passes through the catalyst bed 31 from top to bottom, which regenerates the catalyst and auxiliary agent and accumulates the heat in the catalyst, auxiliary agent, heat storage alumina and supporting alumina ceramic balls in the catalyst bed 31, also raises the bed temperature. The waste heat air is discharged from waste heat air outlet 40 at the lower part of the reactor. After exhausting the reactor through the evacuation port 41 at the lower part of the reactor, hydrogen rich gas 14 is introduced from the upper inlet 38 and goes through from top to bottom the catalyst bed 31 to reduce the catalyst and auxiliary agent. The exhaust gas is discharged through the exhaust port 41, and then the reactor enters the reaction state again. The state change and control of the reactor are achieved by a group of program-controlled valves, 46, 47, 48, 49, 50, 51.

[0062] The following embodiments are used to further describe the low-carbon alkane dehydrogenation process, unit, reaction system of the invention and its usefulness. As an illustrative explanation, the embodiments of the invention shall not be understood as restrictions to other generalized explanations of the invention given in the claims.

[0063] In the embodiment, the temperature change of the catalyst bed is monitored by three-point thermocouples in the bed; the analysis of the composition of the feed and reaction products is performed using an Agilent 6890N gas chromatography.

[0064] Other analytical methods can be found in relevant analytical methods (National Standard for Test Methods of Petroleum and Petroleum Products, China Standards Press, 1989) and (Analytical Methods of Petrochemical Industry (RIPP test methods), Science Press, 1990).

Embodiment 1

[0065] Embodiment 1 illustrates the application usefulness of the low-carbon alkane dehydrogenation process, unit and reaction system in the propane dehydrogenation process.

[0066] Following the preparation procedures in the inventor's granted patent ZL200910210905.0, a 3 mm extrudate dehydrogenation catalyst with a composition of 23 mol % Cr.sub.2O.sub.3, 1 mol % CeO.sub.2, 1 mol % Cl, and 75 mol % Al.sub.2O.sub.3 was prepared, and its surface area was 95 m.sup.2/g, bulk density was 1.05 g/ml, and crushing strength was 65 N/mm.

[0067] Following the steps in the pending patents of the inventors' 201711457256.5 and 201810119334.9, a 3 mm extrudate thermal coupling agent with a composition of 15 mol % CuO, 3 mol % CeO.sub.2, 17 mol % CaO, and 65 mol % Al.sub.2O.sub.3 was prepared, and its surface area was 35 m.sup.2/g , bulk density was 1.1 g/ml, the crushing strength was 40 N/mm.

[0068] The test flow of the low-carbon alkane dehydrogenation reaction is shown in FIG. 1. The prepared 3 mm extrudate dehydrogenation catalyst, the prepared 3 mm extrudate thermal coupling agent, the 5 mm heat storage Al.sub.2O.sub.3≥99.5 mol % with heat capacity of 0.3 cal/g° C. and melting temperature ≥1700° C.; the 8 mm supporting inert alumina ceramic balls of Al.sub.2O.sub.3≥99.5m % with heat capacity 0.3 cal/g° C. and usage temperature ≥1400° C. are packed in the catalyst bed of eight industrial fixed bed reactors in a volume ratio of 1:0.15:0.5:0.5, as shown in FIG. 2.

[0069] According to the process described in the invention, 8 fixed bed reactors are put into operation successively at 3 minute intervals. At any time, 3 reactors are in the dehydrogenation reaction process, 3 reactors are in the regeneration and reheating process, and 2 reactors are in the steam purging or evacuating/reduction process. The single cycle is about 25-30 minutes, including 10-15 minutes for dehydrogenation, 3 minutes for steam purging, 9 minutes for regeneration and reheating of catalyst bed, and 3 minutes for evacuating and reduction.

[0070] Table 1 shows the properties of industrial grade propane feedstock for propane dehydrogenation

TABLE-US-00001 TABLE 1 Feedstock properties of propane dehydrogenation Item Composition/m % Ethane 1.2 Propane 95.4 Propene 2.5 Diene & acetylene 0.5 C.sub.4.sup.+ 0.4

[0071] As the CO and CO.sub.2 of the process gas, the industrial CO and CO.sub.2 are those separated from the waste gas in the process unit of the invention.

[0072] Table 2 shows the operation conditions of dehydrogenation and regeneration when the low-carbon alkane dehydrogenation process method of the invention is applied to propane dehydrogenation

TABLE-US-00002 TABLE 2 Operating conditions of propane dehydrogenation and regeneration Item Parameters Feed temperature/° C. 590 Pressure/kPa (absolutely) 50 Propane feed WHSV/hour.sup.−1 0.5 Process gas WHSV/hour.sup.−1 0.01 Single pass reaction time/min 10~15 Temperature of regeneration air/° C. 670 Pressure of regeneration air/kPa 80 (absolutely)

COMPARATIVE EXAMPLE 1

[0073] Referring to U.S. Pat. No. 2,419,997, a commercially available Cr/Al.sub.2O.sub.3 industrial dehydrogenation catalyst and the similar industrial grade propane feed as in embodiment 1 were used, operating under the typical Houdry fixed bed dehydrogenation condition.

COMPARATIVE EXAMPLE 2

[0074] Referring to U.S. Pat. No. 2,419,997, a commercially available Cr/Al.sub.2O.sub.3 industrial dehydrogenation catalyst, a similar industrial-grade propane feed as in Embodiment 1 and a commercially available Cu/Al.sub.2O.sub.3 heating generating material were used, operating under a typical HOUDRY circulating fixed bed dehydrogenation process condition.

Embodiment 2

[0075] Embodiment 2 illustrates the comparison of the implementation results of the invention with Comparative Examples 1 and 2. Table 3 shows the comparison of the results of low-carbon alkane dehydrogenation process of the present invention, when applied to propane dehydrogenation reaction, with a typical HOUDRY circulating fixed bed dehydrogenation (Comparative Example 1), and those with a HOUDRY circulating fixed bed dehydrogenation with commercial heat generating material (Comparative Example 2). The catalyst life period not <3 years is taken as the initial (SOR) and final (EOR) stages of operation.

TABLE-US-00003 TABLE 3 Comparison of propane dehydrogenation of SOR - EOR catalyst life Embodiment Comparative Comparative Item 1 Example 1 Example 2 Single 50% 44 45 pass propane conversion (SOR)/% Single 44% 40 41 pass propane conversion (EOR)/% Propene 86% 84 84 selectivity (SOR)/% Propene 86% 81 82 selectivity (EOR)/%

[0076] Compared with the operation of a typical HOUDRY circulating fixed bed dehydrogenation and the operation of a typical HOUDRY circulating fixed bed dehydrogenation with heat generating material, the invention has better propane single-pass conversion rate and propylene selectivity and achieves better propane dehydrogenation reaction efficiency.

Embodiment 3

[0077] Embodiment 3 illustrates the process, unit and reaction system of low-carbon alkane dehydrogenation of the invention, and the implementation efficiency in the dehydrogenation process when it is applied to propane and isobutane mixed feed.

[0078] The dehydrogenation catalyst, thermal coupling agent, heat storage inert alumina balls and supporting inert alumina ceramic balls as prepared in Embodiment 1 are packed in the catalyst beds of the 8 industrial fixed bed reactors as shown in FIG. 2. The dehydrogenation of propane and isobutane mixed feed is carried out by following the process of the invention in Embodiment 1 and the process flow chart as shown in FIG. 1.

[0079] The data listed in Table 4 are the property data of propane and isobutane industrial mixed feed; The CO and CO.sub.2 process gases were obtained in the same way as in Embodiment 1.

TABLE-US-00004 TABLE 4 Property of propane and isobutane mixed feed Item Composition/m % Ethane 0.3 Methyl acetylene 0.02 Propadiene 0.02 Propylene 1.4 Propane 56.7 Iso-butane 37.2 Iso-butene 0.7 n-Butane 1.1 n-Butene 0.8 1,3-Butadiene 0.2 cis-Butene 0.5 trans-Butene 1.1

[0080] Table 5 shows the operation conditions of dehydrogenation and regeneration when the low-carbon alkane dehydrogenation process method of the invention is applied to the dehydrogenation of propane and isobutane mixed feed.

TABLE-US-00005 TABLE 5 Operating condition of dehydrogenation and regeneration of propane and isobutane mixed feed Item Parameters Feed temperature/° C. 592 Reactor pressure/kPa (absolutely) 50 Mixed feed WHSV/hour.sup.−1 0.5 Process gas WHSV/hour.sup.−1 0.01 Single pass reaction time/min 10~15 Regeneration air temperature/° C. 671 Regeneration air pressure/kPa (absolutely) 80

COMPARATIVE EXAMPLE 3

[0081] Referring to U.S. Pat. No. 2419997, dehydrogenation is carried out with a similar industrial grade propane and isobutane mixed feed as in Embodiment 3 and a commercially available Cr/Al.sub.2O.sub.3 industrial dehydrogenation catalyst under a typical HOUDRY fixed bed dehydrogenation process.

COMPARATIVE EXAMPLE 4

[0082] Referring to U.S. Pat. No. 2,419,997, dehydrogenation is carried out with similar industrial grade propane and isobutane mixed feed as in Embodiment 1, a commercially available Cr/Al.sub.2O.sub.3 industrial dehydrogenation catalyst and a commercially available Cu/Al.sub.2O.sub.3 industrial heat generating material under a typical HOUDRY fixed bed dehydrogenation process.

Embodiment 4

[0083] Example 4 illustrates the comparison of the implementation efficiency of the invention when it is applied to a mixed low-carbon alkane feedstock.

[0084] Table 6 shows the comparison of results of the HOUDRY circulating fixed bed dehydrogenation process (Comparative Example 3) with that having heat generating material (Comparative Example 4) when propane and isobutane mixed feed is used in the invention. The catalyst's lifetime is not less than 3 years as the initial and final operation period.

TABLE-US-00006 TABLE 6 Comparison of dehydrogenation of propane and isobutane mixed feed at the beginning and end of catalyst life Example Comparative Comparative Item 3 Example 3 Example 4 Single pass 55% 49 50 propane + isobutane mixed feed conversion (SOR)/% Single pass 45% 41 42 propane + isobutane mixed conversion (EOR)/% Propylene + 86% 82 82 isobutene selectivity (SOR)/% Propene + 85% 81 80 isobutane selectivity (EOR)/%

[0085] In comparison with the results of the typical HOUDRY circulating fixed bed dehydrogenation process and with those with heat generating material in dehydrogenation of a mixed propane and isobutane feed, the invention has better conversion and selectivity and obtains better implementation efficiency. The invention provides a low-carbon alkane dehydrogenation process, unit and reaction system, which also has good implementation efficiency for the composition of more complex mixed low-carbon alkane feed and relatively more complex conversion process, and embodies good feed and process adaptability.

Embodiment 5

[0086] Embodiment 5 illustrates the implementation efficiency of a low-carbon alkane dehydrogenation process, unit, and reaction system of the invention when applied on reducing process severity, temperature difference, energy consumption, and material consumption.

[0087] In addition to the above implementation results obtained using industrial propane feed and mixed propane and isobutane feed, the comparison of operating condition data of dehydrogenation process in each embodiment also shows a good implementation efficiency.

[0088] The data listed in Table 7 is the comparison of the catalyst bed temperature and other operating conditions in the unit and the reaction system between the embodiment of the invention and the comparative example of the prior art, as well as the comparison of the process consumption data.

TABLE-US-00007 TABLE 7 Comparison of operation conditions and process consumption between the embodiments of the invention and the prior art. Comparative Comparative Example Item example 1, 3 example 2, 4 1, 3 Temperature difference in catalyst bed Temperature +8 −4.2 −5 difference between top and bottom of the bed/% Temperature +4 +3.2 +3.5 difference between middle and bottom of the bed/% Comparison of severity Catalyst base −2.5 −3.4 bed average maximum temperature/% Reactor base −1.4 −3.2 inlet temperature/% Hot air base −1.7 −4.8 inlet temperature/% Comparison of process consumption Energy base −3 −8 consumption/% Mass base −2 −4 consumption/%

[0089] Compared with the prior art, the invention effectively reduces the temperature difference and the severity in the catalyst bed, and makes the temperature distribution more uniform; the invention also reduces the process energy consumption and material consumption to a certain extent, reflecting a better implementation efficiency.

[0090] These implementation results obtained under different operating conditions and severity are undoubtedly very beneficial to reduce the requirements on process unit and equipment, and on reaction system in terms of materials, design and operation.

[0091] Finally, it needs to be noted that the above embodiments are only used to explain the technical scheme of the invention, not to limit the invention. Although the invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical scheme of the invention can be modified or replaced equivalently without departing from the spirit and scope of the technical scheme of the invention.