Oligomerization Process
20220234967 · 2022-07-28
Inventors
- Andrew Wiersum (Kessel-Lo, BE)
- Paul Hamilton (Chandlers Ford, Eastleigh, GB)
- Luc Martens (Meise, BE)
- Sara Garcla Frutos (Brussels, BE)
- Marcel Janssen (Kessel-Lo, BE)
Cpc classification
B01J31/0257
PERFORMING OPERATIONS; TRANSPORTING
C07C2527/173
CHEMISTRY; METALLURGY
C07C2/18
CHEMISTRY; METALLURGY
C07C2/18
CHEMISTRY; METALLURGY
International classification
Abstract
The present invention concerns a process for oligomerizing an olefin feedstock to form an oligomerization product, and a method of controlling such an oligomerization process. The process comprises oligomerizing propylene to form a C.sub.n olefin, including contacting a feed stream comprising propylene and a recycle fraction with a solid phosphoric acid oligomerization catalyst under effective oligomerization conditions in an oligomerization reactor to produce an oligomerization effluent; and fractionating the oligomerization effluent to obtain a product fraction and the recycle fraction, the product fraction comprising the C.sub.n olefin and the recycle fraction comprising a C.sub.n-3 olefin; wherein the recycle fraction comprises at least 80 wt % of the C.sub.n-3 olefin, based on the weight of the recycle fraction; and wherein n is 9, or 12.
Claims
1. A process for oligomerizing propylene to form a C.sub.n olefin, wherein the process comprises: contacting a feed stream comprising propylene and a recycle fraction with a solid phosphoric acid oligomerization catalyst under effective oligomerization conditions in an oligomerization reactor to produce an oligomerization effluent; and fractionating the oligomerization effluent to obtain a product fraction and the recycle fraction, the product fraction comprising the C.sub.n olefin and the recycle fraction comprising a C.sub.n-3 olefin; wherein the recycle fraction comprises at least 80 wt % of the C.sub.n-3 olefin, based on the weight of the recycle fraction; and wherein n is 9, or 12.
2. The process according to claim 1, wherein the recycle fraction comprises at least 90 wt % of a C.sub.n-3 olefin, based on the weight of the recycle fraction.
3. The process according to claim 1, comprising, in any order, at least one period T1 wherein n is 9 and at least one period T2 wherein n is 12.
4. The process according to claim 3, wherein T1 and T2 are each at least 24 hours, such as at least 1 week.
5. The process according to claim 1, wherein the effective oligomerization conditions include conditions effective for a propylene per pass conversion of at least 90 wt %, based on the weight of propylene fed to the oligomerization reactor.
6. A process according to claim 1, wherein the effective oligomerization conditions include a temperature of at least 175° C. and a pressure of at least 60 barg.
7. A process according to claim 1, wherein propylene and the recycle fraction are present in the feed stream at a propylene:recycle fraction ratio of from 10:1 to 1:2, by weight.
8. A process according to claim 1, wherein the feed stream comprises propylene in an amount of from 25 to 60 wt %, based on the weight of the feed stream.
9. A process according to claim 1, wherein the feed stream comprises the recycle fraction in an amount of from 5 to 50 wt %, based on the weight of the feed stream.
10. A process according to claim 1, wherein feed stream comprises an alkane diluent.
11. A process according to claim 10, wherein the alkane diluent is propane.
12. A process according to claim 10, wherein the feed stream comprises the alkane diluent in an amount of from 20 to 70 wt %, based on the weight of the feed stream.
13. A process according to claim 10, wherein the feed stream comprises X wt % propylene, Y wt % recycle fraction, and Z wt % alkane diluent, wherein X+Y+Z=100, wherein X is from 25 to 60, Y is from 5 to 50 and Z is from 20 to 70; wherein the process comprises at least one period Ta during which X, Y and Z remain constant, and at least one period Tb during which X, Y and Z remain constant, and wherein at least two of X, Y and Z during period Tb differ by at least 5, optionally 10, from X, Y and Z during period Ta.
14. A process according to claim 13, wherein Ta and Tb are each at least 24 hours, such as at least 1 week.
15. A process according to claim 13, wherein all of X, Y and Z during period Tb differ by at least 5, optionally 10, from X, Y and Z during period Ta.
Description
DESCRIPTION OF THE FIGURES
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[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[0026] It will be understood that any suitable solid phosphoric acid catalyst may be used in the process of the present invention. Solid phosphoric acid oligomerization catalysts, such as catalysts for propylene oligomerization are widely available, for example Polymax catalysts available from Clariant.
[0027] As used herein, fresh propylene is propylene not previously contacted with the oligomerization catalyst in the oligomerization reactor. Diluent is an inert fluid, typically fed to the oligomerization reactor together with fresh propylene and the recycle fraction. It will be understood than any suitable diluent may be used, typically an alkane, for example a light alkane, such as one or more C.sub.2-C.sub.5 alkanes. Preferably the diluent comprises propane, for example the diluent comprises at least 50 wt %, such as at least 75 wt %, optionally at least 90 wt %, propane. Optionally, the diluent is propane. As used herein, a recycle stream conveys material from a downstream location in the process to an upstream location, for example from a position downstream of the oligomerization reactor to a position upstream of the oligomerization reactor. The recycle fraction of the process of the first aspect of the invention is a portion of material produced in the oligomerization reactor. As used herein, the product fraction is a portion of material produced in the oligomerization reactor. It will be understood that fractionation of the oligomerization reactor effluent downstream of the oligomerization reactor typically separates the effluent into a plurality of product fractions. The recycle stream may correspond to a portion of at least one of the fractions so produced. Optionally, during continuous operation of the oligomerization reactor, the composition of the recycle stream may be adjusted, for example wherein the recycle fraction initially corresponds to a portion of a first product fraction and subsequently corresponds to a portion of a second product fraction different to the first product fraction. It will be understood that unreacted propylene (and diluent, if present) may also be conveyed from a position downstream of the polymerization reactor to a position upstream of the polymerization reactor, referred to herein as the propylene return fraction. For example, fractionation of the oligomerization reactor effluent may separate unreacted propylene (and diluent, if present) from oligomer products. Unless otherwise stated, propylene fed to the oligomerization zone includes fresh propylene and any return propylene. Similarly, unless otherwise stated, diluent fed to the oligomerization zone includes fresh diluent and any return diluent. Unless otherwise indicated, the recycle fraction referred to herein is separate to the propylene return fraction. For example, the recycle fraction is preferably substantially, such as entirely, free from propylene. It will be understood, however, that any of the fresh propylene feed, propylene return fraction, diluent and recycle fraction may be combined in any order, and/or supplied separately to the oligomerization reactor. Thus, the feed stream supplied to the reactor and contacted with the solid phosphoric acid catalyst in the oligomerization reactor may include feed components fed separately into the oligomerization reactor.
[0028] Optionally, the recycle fraction comprises at least 85 wt %, such as at least 90 wt %, of the C.sub.n-3 olefin, based on the weight of the recycle fraction. Optionally, the recycle fraction has an average carbon number of from n−0.1 to n+0.1, such as from n to n+0.1, as measured by hydrogenation gas chromatography. Optionally, when n is 9, the average branching of C.sub.9 molecules in the recycle fraction is from 1.8 to 2.2, as measured by hydrogenation gas chromatography. Optionally, when n is 6, the average branching of C.sub.6 molecules in the recycle fraction is from 0.8 to 1.2, as measured by hydrogenation gas chromatography.
[0029] When n is 9, the process is configured for formation of nonene. When n is 12, the process is configured for formation of dodecene. It will be understood that during continuous operation of the process, n may be varied. Thus, the process may operate for one period during which the process is configured for formation of nonene, and for another period during which the process is configured for formation of dodecene. It will be understood that the process of the present invention thus provides the operator with flexibility, allowing the oligomerization reactor output to be adjusted according to fluctuations in market demand for nonene and dodecene. Optionally, the process comprises, in any order, at least one period T1 wherein n is 9 and at least one period T2 wherein n is 12. Optionally, T1 and T2 are each independently at least 12 hours, such as at least 24 hours, for example at least 72 hours, optionally at least 1 week, such as at least 2 weeks, for example at least 1 month. Optionally, the oligomerization reaction conditions are substantially the same, such as the same, during T1 and T2, apart from the composition of the recycle fraction.
[0030] It will be understood that any suitable oligomerization conditions may be used in the process of the present invention. For example, suitable conditions may be chosen by the process operator in dependence on the particular equipment and catalyst utilised and the desired per pass conversion of propylene. Preferably, the effective oligomerization conditions include conditions effective for a propylene per pass conversion of at least 70 wt %, such as at least 80 wt %, for example at least 90 wt %, based on the weight of propylene fed to the oligomerization reactor. As used herein, per pass conversion of propylene is the proportion of propylene oligomerized to a higher olefin on each pass through the reactor. Per pass conversion is a convenient measure of oligomerization efficiency in a continuous oligomerization process where fresh olefin is continuously supplied to the oligomerization reactor. As used herein, high severity oligomerization conditions are conditions effective to achieve propylene per pass conversion of at least 95 wt % (e.g. 95-98 wt %), based on the weight of propylene fed to the oligomerization reactor. As used herein, lower severity oligomerization conditions are conditions effective to achieve propylene per pass conversion of up to 94 wt % (e.g. 85-93 wt %, 90-93 wt %), based on the weight of propylene fed to the oligomerization reactor. It will be understood that high severity oligomerization conditions typically include higher temperatures than employed in lower severity oligomerization conditions, such as temperatures at least 15° C. higher, such as at least 25° C. higher.
[0031] Optionally, the effective oligomerization conditions include one or more of a temperature of at least 160° C., such as at least 170° C., for example at least 180° C.; and a pressure of at least 40 barg, such as at least 45 barg. Optionally, the effective oligomerization conditions include one or more of a temperature of from 150° C. to 250° C., such as 170° C. to 240° C., for example 180° C. to 230° C.; and a pressure of from 40 to 80 barg, such as 45 to 65 barg. Unless otherwise stated, pressure is gauge pressure, recognised as the amount by which the measured pressure exceeds the pressure of the atmosphere. Typically, the oligomerization temperature increases during operation of the oligomerization, rising from a starting temperature to an end temperature. The end temperature may be around 10° C. higher than the starting temperature. As used herein, the temperature of the effective oligomerization conditions is the temperature at steady state operation, which is typically equal to or greater than the starting temperature and equal to or less than the end temperature. Optionally, the effective oligomerization conditions include a liquid hourly space velocity (LHSV) of from 2 to 4 ml/ml/h, such as from 2.5 to 3.5 ml/ml/h. Additionally or alternatively, the effective oligomerization conditions include a weight hourly space velocity (WHSV) of from 0.5 to 3 g/g/h, such as from 1 to 2 g/g/h. Optionally, the effective oligomerization conditions include a water content of from 200 to 1000 wtppm, such as from 400 to 600 ppm, based on the weight of feed to the reactor. Unless otherwise indicated, the feed stream for the oligomerization reactor, i.e. the feed stream, includes all materials fed to the reaction, including for example fresh feed, recycled feed and return feed, when present.
[0032] It will be understood that LHSV is the volume feed rate per volume of catalyst (e.g. feed volume/catalyst volume/time), while WHSV is the weight feed rate per weight of catalyst (e.g. feed weight/catalyst weight/time). Feed density and catalyst density can be used to convert between LHSV and WHSV.
[0033] In a process operating without any recycle of oligomers to the oligomerization reactor, the feed stream may consist essentially of propylene and diluent, such as a light alkane diluent comprising propane. In terms of the ratio of feeds to the reactor, it will be understood that, as compared to such a conventional process without recycle, the recycle fraction can be used (i) in place of a portion of the propylene feed, (ii) in place of a portion of the diluent feed, or (iii) partially in place of the propylene feed and partially in place of the diluent feed. It will be understood that the olefin:diluent ratio is important for temperature control because of the exothermic nature of the oligomerization reactor. It will also be understood that different olefins have differing reactivity. In the case of option (i), while substitution of a portion of the propylene feed for the recycle fraction may maintain a comparable olefin:diluent ratio, reactor temperature may nevertheless decrease if the olefin in the recycle fraction is less reactive than the propylene it is substituting. That decrease in temperature may help to increase selectivity for higher olefins and/or improve catalyst life. Furthermore, in the case of option (i), while propylene per pass conversion may remain at a similar level, overall productivity will likely reduce because less propylene is fed to the process. In the case of option (ii), the amount of olefin relative to the amount of diluent increases, which may result in an unwanted increase in reactor temperature. Furthermore, while both propylene per pass conversion and overall productivity may increase, selectivity for higher olefins may be reduced and/or catalyst life shortened, for example as a result of the increase in reactor temperature. It will be appreciated that option (iii) presents a compromise between options (i) and (ii). In a conventional process (i.e. without recycle), once process parameters have been optimised to achieve stead state, isothermal operation, the operator has little ability to make further adjustments in order to vary selectivity for different oligomer products. The present inventors have found that introducing a recycle fraction increases process flexibility by providing a greater number of adjustable variables, including for example recycle composition and recycle:propylene:diluent ratios.
[0034] Optionally, the feed stream comprises propylene and the recycle fraction in a propylene fed to the reactor:recycle fraction ratio of from 10:1 to 1:2, such as from 8:1 to 2:3, for example from 5:1 to 1:1. Additionally or alternatively, the feed stream comprises propylene and C.sub.n olefin of the recycle fraction in a propylene fed to the reactor:C.sub.n olefin fraction ratio of from 10:1 to 1:2, such as from 8:1 to 2:3, for example from 5:1 to 1:1. Optionally, the feed stream comprises propylene in an amount of from 20 to 65 wt %, such as 25 to 60 wt %, for example 30 to 50 wt %, based on the weight of the feed stream. Optionally, the feed stream comprises the recycle fraction in an amount of from 5 to 60 wt %, such as from 8 wt % to 55 wt %, for example 10 wt % to 50 wt %, based on the weight of the feed stream. Optionally, the feed stream comprises diluent (e.g. alkane diluent) in an amount of from 10 to 75 wt %, such as 20 to 70 wt %, for example 30 to 50 wt %, based on the weight of the feed stream.
[0035] Optionally, the feed stream comprises X wt % propylene, Y wt % recycle fraction, and Z wt % alkane diluent, wherein X+Y+Z=100, wherein X is from 25 to 60, Y is from 5 to 50 and Z is from 20 to 70. Optionally, the process comprises at least one period Ta during which
[0036] X, Y and Z remain constant, and at least one period Tb during which X, Y and Z remain constant. Optionally, X during Ta differs from X during Tb by at least 5, such as at least 10, for example at least 15. Optionally, Y during Ta differs from Y during Tb by at least 5, such as at least 10, for example at least 15. Optionally, Z during Ta differs from Z during Tb by at least 5, such as at least 10, for example at least 15. Optionally, at least two of X, Y and Z during period Tb differ by at least 5, optionally 10, for example at least 15, from X, Y and Z during period Ta. Optionally, all of X, Y and Z during period Tb differ by at least 5, optionally 10, for example at least 15, from X, Y and Z during period Ta. Optionally, Ta and Tb are each independently at least 12 hours, such as at least 24 hours, for example at least 72 hours, optionally at least 1 week, such as at least 2 weeks, for example at least 1 month. Optionally, the oligomerization reaction conditions are substantially the same, such as the same, during Ta and Tb, apart from the composition of the recycle fraction. It will be appreciated that period Ta and/or period Tb may each comprise any number of periods T1 and/or T2, and vice versa. It will be appreciated that such variations in the relative amounts of propylene, recycle fraction and diluent in the feed stream may be employed in the method of controlling C.sub.9 and C.sub.12 olefin selectivity according to the second aspect of the invention. For example, the method of the second aspect of the invention may comprise in any order operating the process of the first aspect of the invention for at least one period Ta, and for at least one period Tb.
[0037] Olefin oligomers produced by the process of the present invention are useful in the production of oxygenated organic compounds. For example, the olefin oligomer products may be subjected to hydroformylation by reaction with synthesis gas (carbon monoxide and hydrogen) over a hydroformylation catalyst, such as cobalt or rhodium. The hydroformylation reaction generates an aldehyde having one more carbon atom than the starting olefin oligomer. By way of example, higher alcohols useful as intermediates in the manufacture of plasticizers, detergents, solvents, synthetic lubricants, and the like, are produced commercially in the so-called Oxo Process (i.e., transition metal catalyzed hydroformylation) by conversion of higher olefin fractions (typically C.sub.5-C.sub.12) to an aldehyde-containing oxonation product having one additional carbon atom (e.g., C.sub.6-C.sub.13). Hydrogenation and distillation yields the respective alcohols, or the aldehydes may instead be further oxidized to the respective acids. Synthesis gas may be obtained, for example, by gasification of a carbonaceous feedstock, e.g. tar. Often, synthesis gas so produced includes impurities such as sulfur-, nitrogen-, and/or halogen-containing compounds. Such impurities in the synthesis gas feed can reduce catalyst life and/or lead to accumulation of unwanted impurities in recycle loops. For example, some hydroformylation processes utilise water recycle loops in order to minimise wastewater generation, which water recycle loops can accumulate acids derived from impurities in the synthesis gas. Sulfur present in synthesis gas may react with a cobalt hydroformylation catalyst, forming a Co—S complex. It may be necessary to periodically purge the Co—S complex and water in the water recycle loop in order to prevent plugging of heat exchangers and other vessels employed in the hydroformylation process.
[0038] One approach to removal of acid gases such as H.sub.2S and CO.sub.2 from synthesis gas is to contact the gas with an amine based adsorbent, such as Flexsorb PS. Such an adsorbent has been found to reduce H.sub.2S and COS levels in synthesis gas to around 0.5 ppmv (the synthesis gas being produced by gasification of tar feeds containing 1-3% w/w total sulfur). It has now been found that the Rectisol acid gas removal process can be utilised for removing impurities from synthesis gas. The Rectisol process utilises methanol as a solvent at about to separate acid gases such as H.sub.2S and CO.sub.2 from gas streams. The methanol is used at a temperature of about −40° C., at which temperature Henry's Law coefficients for methanol favour the removal of acid gases and other impurities from the synthesis gas. Rectisol treatment is capable of reducing impurities to a level of <100 ppbv, or even 10 ppbv for some impurities. Reducing impurity levels to such low levels reduces hydroformylation catalyst consumption and wastewater purging, thereby reducing operating costs. The Rectisol process utilises an adsorption tower as well as downstream methanol regeneration towers. The adsorption tower includes a water wash section, which has been found to be capable of reducing the content of halogen impurities, such as chloride, in synthesis gas down to <3 ppbv. Removal of chloride impurities helps to reduce corrosion of hydroformylation reaction equipment. It has been found that impurity removal can be enhanced by passing the Rectisol purified synthesis gas through a temperature swing adsorption system. More particularly, the temperature swing adsorption system acts to remove impurities that break through the Rectisol adsorption tower. Preferably, the temperature swing adsorption system comprises a silica adsorbent for trapping methanol, and an alumina-silicate molecular sieve for capturing residual halogen- and sulfur-containing compounds.
Examples of the Invention
[0039] The following examples illustrate the present invention. Numerous modifications and variations are possible and it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
[0040] For all examples, a mixture of propylene, propane and optionally a co-feed provided to model a recycle stream was contacted with a solid phosphoric acid catalyst in a tubular reactor and the product analysed to determine selectivity for specific olefin products. Tests were carried on a pilot unit having two identical tubular reactors, each of which were filled with approximately 100 grams of solid a commercially available phosphoric acid catalyst crushed and sieved into particles having an average diameter of 2.8-3.4 mm. Hydration of the catalyst was controlled by the injection of isopropyl alcohol into the feed of each reactor. Olefin contents, average carbon number and average branching of C.sub.9 molecules were determined by hydrogenation gas chromatography (HGC). In HGC, olefins in the sample to be analyzed are first hydrogenated to the corresponding paraffins before the sample is passed through an Agilent CP-Sil PONA CB gas chromatography (GC) column. This approach simplifies the GC spectrum because it significantly reduces the number of possible isomers. The peaks in a HGC spectrum can be more easily assigned to a particular carbon number as compared to the peaks of a GC spectrum of the original olefin mixture, and the carbon number distribution (CND) of a complex stream such as an oligomerization reactor effluent is easier to obtain and becomes more accurate. The hydrogenation step was performed by a 0.5 wt % Pt on alumina hydrogenation catalyst in the GC analyzer downstream of the splitter, using H.sub.2 as the carrier gas. Saturates content was determined by gas chromatography on a Agilent Olefin Trap 0.5 m×1.8 in×2.0 mm with POLT material.
[0041] Online gas chromatography (GC) analyses of the propylene/propane (C.sub.3) feed stream and the C.sub.3 gas stream exiting the reactor were used to monitor the propylene Per Pass Conversion (PPC). Temperature was used to adjust the propylene PPC to within the target range. The two reactor columns shared a heating jacket and were therefore always at the same temperature. Unless otherwise indicated, all other process conditions were identical for both reactors.
[0042] During each test, the liquid reactor effluent was analyzed on a daily basis for CND according to the following methodology. The liquid reactor effluent was recovered and allowed to settle for 24 hours at atmospheric pressure to allow the evaporation of unreacted light olefins and paraffins. The CND in the C.sub.5-C.sub.13+ range was subsequently analyzed in these offline samples by HGC. Net selectivities towards each carbon number were calculated by dividing the net increase in weight fraction of a given carbon number across the reactor by the total net increase in the weight fraction of C.sub.5-C.sub.13+ across the reactor.
Example 1
[0043] Example 1 was conducted to study the effect of recycling a high concentration nonene recycle stream (“Nonene”) as compared to recycling a stream representative of a typical ‘Light Polymer Recycle’ (“LPR”) stream which comprises less than 80 wt % C.sub.9. Reference data were obtained for oligomerization without any recycle stream by feeding a mixture of propane and propylene to the reactor. The impact of recycling Nonene as compared to LPR was simulated by feeding a mixture of propane, propylene and either commercial grade nonene or LPR from a commercial propylene oligomerization unit to one or both reactors. The composition of the two co-feeds used is given in Table 1.
TABLE-US-00001 TABLE 1 Composition of nonene and LPR used as co-feed (Example 1) Property Nonene LPR C.sub.7− content (wt %) <0.1 6.3 C.sub.8 content (wt %) 0.6 6.5 C.sub.9 content (wt %) 92.2 63.8 C.sub.10 content (wt %) 7.1 10.7 C.sub.11+ content (wt %) <0.1 12.7 Average carbon number 9.07 9.15 Average branching of C.sub.9 molecules 2.00 1.97 Saturates content (wt %) 0.8 3.9
[0044] The Nonene and LPR tests were carried out under substantially identical conditions. The target propylene PPC was 60-70%. The reactors were fed with different ratios of propylene-propane-co-feed on a weight basis, simulating different recycle rates. The total flow on a mass basis was kept equal in all cases. The process conditions are listed in Table 2.
TABLE-US-00002 TABLE 2 Process conditions (Example 1) Parameter Value Start T (° C.) 165 End T (° C.) 175 P (barg) 45 WHSV (g/g/h) 1.2 H.sub.2O (wtppm) 350 Target PPC (wt %) 60-70
[0045] Three different ratios of liquid co-feed-to-propylene were tested for each co-feed. A reference test with no co-feed was also run for comparison. The test ratios are listed in Table 3.
TABLE-US-00003 TABLE 3 Ratios of liquid co-feed to propylene fed to the reactors (Example 1) Reference test Co-feed tests Feed to Reactor R1 Test 1.1 Test 1.2 Test 1.3 Propylene (wt %) 30 30 30 30 Propane (wt %) 70 55 40 25 Co-feed (wt %) 0 15 30 45 Co-feed:Propylene ratio 0% 50% 100% 150%
[0046] Each test was run for 6 days.
TABLE-US-00004 TABLE 4 Changes in net selectivities to different carbon number groups with replacement of LPR co-feed by Nonene co-feed (Example 1) Change in Selectivity (wt %) Co-feed:Propylene ratio 50% 100% 150% C.sub.5-C.sub.8 4.3 6.2 5.6 C.sub.9 −3.8 −7.7 −9.3 C.sub.10-C.sub.11 −4.1 −4.3 −4.5 C.sub.12 6.9 7.2 9.5 C.sub.13+ −3.3 −1.4 −1.2
[0047] The results in
Example 2
[0048] Example 2 was conducted to study the effect of recycle of a high concentration nonene stream (“Nonene”) at high severity. Reference data were obtained by feeding a mixture of propane and propylene. The impact of Nonene recycle was simulated by feeding a mixture of propane, propylene and commercial grade Nonene to one or both reactors. The composition of the Nonene used as co-feed is given in Table 5.
TABLE-US-00005 TABLE 5 Composition of Nonene used as co-feed (Example 2) Property Value C.sub.7− content (wt %) <0.2 C.sub.8 content (wt %) 1.1 C.sub.9 content (wt %) 91.8 C.sub.10 content (wt %) 6.5 C.sub.11+ content (wt %) <0.5 Average carbon number 9.06 Average branching of C.sub.9 molecules 1.96 Saturates content (wt %) 0.4
[0049] The target propylene PPC was 95-98 wt %. The reactors were fed with different ratios of propylene-propane-Nonene on a weight basis, simulating different recycle rates. The total flow on a volumetric basis was kept equal in all cases. The detailed process conditions are listed in
[0050] Table 6.
TABLE-US-00006 TABLE 6 Process conditions (Example 2) Reactor Conditions Starting T (° C.) 211 End T (° C.) 220 P (barg) 65 LHSV (ml/ml/h) 2.8 H.sub.2O (wtppm) 510 Target PPC (wt %) 95-98
[0051] Four different ratios of liquid co-feed to propylene were tested. A reference test without Nonene co-feed was also run for comparison. The detailed test experiments are listed in Table 7.
TABLE-US-00007 TABLE 7 Ratios of liquid co-feed to propylene fed to the reactors (Example 2) Reference Co-feed tests Feed to Reactor test R2 Test 2.1 Test 2.2 Test 2.3 Test 2.4 Propylene (wt %) 55 50 50 50 30 Propane (wt %) 45 40 30 25 40 Nonene (wt %) 0 10 20 25 30 Nonene:Propylene ratio 0% 20% 40% 50% 100%
[0052] Each test was run for at least one week.
TABLE-US-00008 TABLE 8 Changes in net selectivities to different carbon number groups with varying Nonene:Propylene ratios (Example 2) Change in Selectivities (wt %) Reference 100% Selectivities 50% Nonene: Nonene: (no recycle) (wt %) Propylene Propylene C.sub.5-C.sub.8 19.2 1.0 7.4 C.sub.9 56.9 −8.8 −25.1 C.sub.10-C.sub.11 10.6 1.1 2.5 C.sub.12 11.2 6.5 14.9 C.sub.13+ 2.0 0.2 0.3
[0053] The results in
Example 3
[0054] Example 2 was repeated under lower severity conditions, and the total flow on a weight basis was the same to both reactors. The detailed process conditions are listed in Table 9.
TABLE-US-00009 TABLE 9 Process conditions (Example 3) Reactor Conditions Starting T (° C.) 185 End T (° C.) 195 P (barg) 65 WHSV (g/g/h) 1.5 H.sub.2O (wtppm) 510 Target PPC (wt %) 90-93
[0055] Two different ratios of liquid co-feed to propylene were tested. The target propylene PPC was 90-93 wt %. A reference test with no Nonene co-feed was also run for comparison. The detailed test experiments are listed in Table 10.
TABLE-US-00010 TABLE 10 Ratios of liquid co-feed to propylene fed to the reactor (Example 3) Reference Co-feed tests Feed to Reactor test R3 Test 3.1 Test 3.2 Propylene (wt %) 50 46 36 Propane (wt %) 50 36 28 Nonene (wt %) 0 18 36 Nonene:Propylene ratio 0% ~40% 100%
[0056] Each test was run for at least one week.
TABLE-US-00011 TABLE 11 Changes in net selectivities to different carbon number groups with varying Nonene:Propylene ratios (Example 3) Change in Selectivities wt % Reference 40% 100% Selectivities Nonene: Nonene: (no recycle) (wt %) Propylene Propylene C.sub.5-C.sub.8 6.9 1.2 1.9 C.sub.9 65.7 −5.6 −9.1 C.sub.10-C.sub.11 9.1 −0.2 −2.0 C.sub.12 16.7 5.1 9.1 C.sub.13+ 1.6 −0.4 0.0
[0057] The results in
[0058] A comparison between Examples 2 and 3 show that similar effects are observed at high severity and at lower severity.
Example 4
[0059] Example 4 was conducted to study the effect of recycle of a high concentration hexene stream (“Hexene”) at high severity. Reference data were obtained by feeding a mixture of propane and propylene. The impact of Hexene recycle was simulated by feeding a mixture of propane, propylene and commercial grade Hexene to one or both reactors. The composition of the Hexene used as co-feed is given in Table 12.
TABLE-US-00012 TABLE 12 Composition of Hexene used as co-feed (Example 4) Property Value C.sub.4− content (wt %) <0.2 C.sub.5 content (wt %) 5.8 C.sub.6 content (wt %) 90.1 C.sub.7 content (wt %) 3.9 C.sub.8+ content (wt %) <0.1 Average carbon number 5.98 Average branching of C.sub.6 molecules 0.99 Saturates content (wt %) 19.9
[0060] The target propylene PPC was 95-98 wt %. The reactors were fed with different ratios of propylene-propane-hexene on a weight basis, simulating different recycle rates. The total flow on a volumetric basis was kept equal in all cases. The detailed process conditions are listed in Table 13.
TABLE-US-00013 TABLE 13 Process conditions (Example 4) Reactor Conditions Starting T (° C.) 211 End T (° C.) 220 P (barg) 65 LHSV (ml/ml/h) 2.8 H.sub.2O (wtppm) 510 Target PPC (wt %) 95-98
[0061] Three different ratios of liquid co-feed to propylene were tested. A reference test with no Hexene co-feed was also run for comparison. The detailed test experiments are listed in Table 14.
TABLE-US-00014 TABLE 14 Ratios of liquid co-feed to propylene fed to the reactors (Example 4) Reference Co-feed tests Feed to Reactor test R4 Test 4.1 Test 4.2 Test 4.3 Propylene (wt %) 55 50 50 30 Propane (wt %) 45 40 30 40 Hexene (wt %) 0 10 20 30 Hexene:Propylene ratio 0% 20% 40% 100%
[0062] Each test was run for at least one week.
TABLE-US-00015 TABLE 15 Change in net selectivities to different carbon number groups with varying Hexene:Propylene ratios (Example 4) Change in Selectivities (wt %) Reference 100% Selectivities 40% Hexene: Hexene: (no recycle) (wt %) Propylene Propylene C.sub.5 0.6 −0.6 −0.6 C.sub.6 4.1 −4.1 −4.1 C.sub.7-C.sub.8 7.2 −1.3 −1.2 C.sub.9 56.9 7.2 10.8 C.sub.10-C.sub.11 10.6 −0.2 −1.7 C.sub.12 11.2 −1.0 −3.1 C.sub.13+ 2.0 0.1 0.0
[0063] The results in
Example 5
[0064] Example 5 was conducted to determine the effect of recycling higher olefin products on catalyst life. One reactor was fed with a mixture of propane and propylene while the other reactor was fed with propane, propylene and commercial grade nonene (“Nonene”) to simulate the recycle. The composition of the nonene used as co-feed is given in Table 16.
TABLE-US-00016 TABLE 16 Composition of Nonene used as co-feed (Example 5) Property Value C.sub.7− content (wt %) <0.2 C.sub.8 content (wt %) 1.1 C.sub.9 content (wt %) 91.8 C.sub.10 content (wt %) 6.5 C.sub.11+ content (wt %) <0.5 Average carbon number 9.06 Average branching of C.sub.9 molecules 1.96 Saturates content (wt %) 0.4%
[0065] The propylene PPC target range was 95-98 wt %. Online differential pressure indicators were installed to measure the pressure drop across the reactors throughout the run. Each test was allowed to run for 4 weeks, which is approximately the lifetime of a commercial tubular reactor running at high severity conditions. The catalyst life is defined as the grams of liquid product obtained per gram of catalyst, after subtracting the grams of liquid co-feed fed to the reactor.
[0066] The reference reactor was fed with a 50-50 mixture of propylene and propane while the co-feed reactor was fed with a mixture of 30-40-30 propylene-propane-Nonene on a weight basis, corresponding to the recycle-to-propylene ratio of 100%. The total flow on a volumetric basis was the same to both reactors. The detailed process conditions are listed in Table 17.
TABLE-US-00017 TABLE 17 Process conditions and feed compositions (Example 5) Reference Reactor Co-feed reactor Starting T (° C.) 211 P (barg) 65 LHSV (ml/ml/h) 2.8 H.sub.2O (wtppm) 510 Target PPC (wt %) 95-98 Propylene in reactor feed (wt %) 50 30 Propane in reactor feed (wt %) 50 40 Nonenes in reactor feed (wt %) 0 30
[0067] The temperature of the two reactors was increased from the starting temperature (211° C.) on two occasions to ensure that the per pass conversion of the reference reactor remained within the target range. Although the temperature was raised for both reactors as the same time on stream, due to the higher concentration of propylene in the feed to the reference reactor the catalyst life is greater for the reference reactor than for the co-feed reactor at the point where the temperature is increased.
[0068] Propylene PPC for the reference and co-feed reactors are shown as a function of catalyst life in
Example 6
[0069] Example 5 was repeated under lower severity conditions. The propylene PPC target was 90-93 wt %. The reference reactor was again fed with a 50-50 mixture of propylene and propane while the co-feed reactor was fed with a mixture of 46-36-18 propylene-propane-Nonene on a weight basis, corresponding to the recycle-to-propylene ratio of 40%. It is believed that the Nonene stream will act to dilute propylene and to assist in heat management. The total flow on a weight basis was initially the same to both reactors, but because of a large difference in per pass conversion, the WHSV of the reference reactor was subsequently reduced to bring the conversion within the target range. The detailed process conditions are listed in Table 18.
TABLE-US-00018 TABLE 18 Process conditions (Example 6) Reference reactor Co-feed reactor Starting T (° C.) 185 P (barg) 65 WHSV (g/g/h) 1.5 H.sub.2O (wtppm) 510 Target PPC (wt %) 90-93 Propylene in reactor feed (wt %) 50 46 Propane in reactor feed (wt %) 50 36 Nonenes in reactor feed (wt %) 0 18
[0070] Propylene PPC for the reference and co-feed reactors are shown as a function of catalyst life in
[0071] The results in