BR0105270B1 - aromatic alkylation process using a silica supported alkylation catalyst as well as a process in the production of ethylbenzene. - Google Patents

Description

Report of the Invention Patent for "Aromatic Alkylation Process Using a Silica-Supported Alkylation Catalyst as a Process for the Production of Ethylbenzene".

FIELD OF INVENTION

This invention relates to an aromatic alkylation process comprising alkylating an aromatic substrate such as benzene over a beta zeolite aromatic alkylation catalyst formulated with a silica binder.

BACKGROUND OF THE INVENTION

Zeolite beta is a well known molecular sieve catalyst that is employed in hydrocarbon conversion processes such as wax removal and catalytic fractionation of relatively heavy high molecular weight hydrocarbon oils. Beta zeolite, as employed in such conversion practices, was first described in U.S. Patent No. 3,308,069 issued to Wadlinger et al. And later in a so-called improved form in U.S. Patent No. 4,642,226 issued to Calvert et al. As disclosed in the Calvert patent, conversion processes in which beta zeolite is particularly useful are wax removal, hydroisomerization, fractionation, hydrofractionation and aromatization by converting light aliphatic hydrocarbons to aromatic hydrocarbons. As presented in Calvert, beta zeolite employed in such conversion processes can be prepared by synthetic procedures involving hydrothermal digestion of reaction mixtures, including silica, alumina, various other oxides or hydroxides of optional metals. , and a standard organic agent that is employed to produce the desired crystalline structure. The amount of silica and alumina in the reaction mixture may vary with a standard silica to alumina ratio in the range of 20-250, ultimately resulting in silica / alumina molar ratios of the crystalline product ranging from less than 20 to about 60 even as high as, in an example given in Calvert, 171.

Molecular sieve catalyst such as beta zeolite, as well as numerous other molecular sieves, are commonly employed in combination with a matrix material that acts as a binder for the molecular sieve. For example, the aforementioned patent granted to Wadlinger discloses that beta zeolite may be employed alone or as a dispersed mixture in combination with a low activity and / or catalytically active material that functions as a binder for the zeolite catalyst. constituent. The above-mentioned patent issued to Calvers describes the use of inorganic materials such as clay, silica or alumina or various composite materials such as silica / alumina, silica / magnesia and various other binary and ternary compositions.

In addition to the use of beta zeolite in hydrocarbon conversion processes, including, for example, wax removal, hydrofraction or aliphatic aroma conversion as described above, beta zeolite, as well as numerous other molecular sieves, has been employed. catalysts in the alkylation of an aromatic substrate. Such alkylation conversion reactions include alkylation of aromatic substrates such as benzene to produce aromatic alkyls such as ethylbenzene, ethyltholuene, cumene or higher aromatics and transalkylation of polyalkylbenzenes to monoalkylbenzenes. Typically, an alkylation reactor producing a mixture of mono and polyalkyl benzene may be coupled through various stages of separation to a downstream transalkylation reactor. Such alkylation and transalkylation reactions may be carried out in the liquid phase, the vapor phase or under conditions where both liquid and vapor phases are present.

U.S. Patent No. 4,185,040 issued to Ward et al. Discloses an alkylation process employing a low sodium molecular sieve catalyst of less than 0.5 wt% Na 2 O, which process is said to be. be especially useful in the production of ethylbenzene from benzene and ethylene, and cumene from benzene and propylene. Examples of suitable zeolites include X, Y, L, B, ZSM-5 and omega crystal molecular sieves, with steam stabilized hydrogen Y zeolite being preferred. Specifically, a vapor stabilized ammonium Y zeolite of about 0.2% Na 2 O is shown. Various forms of catalyst are disclosed in Ward et al. Although cylindrical extrudates may be employed, a particularly preferred form of catalyst is a form called a "trilobate" which is similar in nature to a three-leaf clover. The surface area / volume ratio of the extrudate should be in the range of 215.9 - 406.40 cm "1 (85-160 inch" 1). The alkylation process may be carried out with up or down flow, the latter being preferred, and preferably under temperature and pressure conditions such that at least some liquid phase is present, at least until substantially all of the olefin alkylating agent. be consumed. The Ward and others patent states that rapid catalyst deactivation occurs under even more alkylation conditions when no liquid phase is present. In the Ward process, as well as the various conversion processes described above, the zeolite may be incorporated with a porous mineral oxide binder to obtain in the particulate catalyst configuration such as the trilobed configuration. Accordingly, Ward describes the use of alumina gel, silica gel, silica / alumina co-gels, various clays, titania and other alumina mineral oxides being preferred for use in combination with preferred Y zeolite.

As is the case with zeolite employed in conversion or alkylation processes. Procedures involving beta zeolite for alkylation or transalkylation processes are usually performed employing alumina as a binder providing a matrix for the zeolite catalyst. Accordingly, U.S. Patent No. 4,891,458 issued to Ennes et al. Discloses a process for the liquid alkylation or transalkylation phase of an aromatic hydrocarbon employing a beta zeolite catalyst. Beta zeolite is presented in Ennes and others as having a silicon to aluminum atomic ratio of greater than 5: 1 and less than 100: 1, and preferably greater than 5: 1 and less than 50: 1. Ennes describes alkylation under conditions where the molar ratio of aromatics to olefins is at least 4 to 1 to prevent rapid catalyst clogging. The reaction temperature ranges from about 37.8 ° C to 315.6 ° C (100 ° to 600 ° F) and the reaction pressure is typically about 0.35 - 0.69 MPa (50-100 psig). ) and sufficient to maintain at least one partial liquid phase. Preferably, the beta zeolite used in the Ennes procedure is predominantly hydrogen, obtained by ammonium exchange of the synthesized product followed by calcination. Ennes describes that pure zeolite may be employed with an inorganic oxide binder such as alumina, silica, silica / alumina or naturally occurring clays. Ennes insists that the preferred inorganic binder is alumina.

Another alkylation procedure is disclosed in US Patent No. 4,798,816 issued to Ratcliffe et al. And involves the use of molecular sieve alkylation catalysts which are treated to enhance monoalkylation selectivity, specifically in the propylene benzene for produce cumene. Selectivity is increased by at least one percentage point by first depositing a carbonaceous material in the catalyst and then subjecting the resulting carbon containing catalyst particles to combustion. Specific crystalline zeolitic molecular sieves include those selected from the group of Y zeolites, fluorinated Y zeolites, X zeolites, beta zeolite, L zeolite and omega zeolite. Preferred Y-type zeolites may be de-illuminated to produce an overall silica to alumina ratio of above 6. As is the case in the preceding references, the preferred inorganic refractory oxide material used as a binder is alumina, specifically catapal, although other binders such as alumina, gaul, thalia, titania, zirconia, beryllium, silica, silica-alumina and various other materials are presented.

Butler publication EPA 467,007 describes other processes which have separate alkylation and transalkylation zones employing various molecular sieve catalysts and with the transalkylation reactor outlet being recycled to an intermediate separation zone. Here, a benzene separation zone, from which an ethylbenzene / polyethylbenzene fraction is recovered from the bottom with recycling of the benzene air fraction to the alkylation reactor, is preceded by a pre-fractionation zone. The pre-fractionation zone produces a benzene air fraction which is recycled along with the benzene column air fractions and a bottom fraction comprising benzene, ethylbenzene and polyethylbenzene. The subsequent two separation zones are interposed by the benzene separation zone and the transalkylation reactor to provide ethylbenzene recovery as a process product and a heavier residue fraction. The polyethylbenzene fraction of the last separation zone is applied to the transalkylation reactor and the output is applied either directly to the second benzene separation column or indirectly through a separator and then to the second benzene separation column. Butler describes that the alkylation reactor may be operated in the liquid phase with a catalyst such as zeolite-beta, zeolite Y or omega zeolite or in the vapor phase employing a catalyst such as silicalite or ZSM-5.

Another procedure involving liquid phase alkylation of an aromatic substrate is disclosed in EPA Publication No. 507,761 to Shamshoum et al. This procedure involves the use of a molecular sieve catalyst that is based on beta zeolite but has been modified by incorporating lanthanum. The lanthanum modified beta zeolite catalyst is presented in Shamshoum et al. To provide little or no xylene production under moderate liquid phase conditions as contrasted with the use of hydrogen zeolite beta. In the Shamshoum et al procedure, the initial beta zeolite preferably has a silica / alumina ratio of between 20 and 50, which is initially subjected to an ion exchange step followed by calcination at a temperature of about 570 ° C for 2 hours or more. Following subsequent ion exchange and calcination procedures, the molecular sieve is dried followed by incorporation of lanthanum into the zeolite system by ion exchange with a lanthanum saline solution. Shamshoum et al. Describe that lanthanum modified beta zeolite is mixed with binder such as sol alumina, gamma alumina or other refractory oxides to produce a zeolite binder mixture which is then pelletized. Other procedures involving liquid phase benzene alkylation are disclosed in U.S. Patent No. 5,030,786 issued to Shamshoum et al. And 5,073,653 issued to Butler. Shamshoum '786 describes the use of molecular sieves having a pore size greater than 6.5 angstroms, specifically Y and beta zeolites having pore sizes in the range of 7-7.5 angstroms. Butler's patent discloses benzene alkylation in the liquid phase employing catalysts including zeolites such as omega zeolite, beta zeolite and Y zeolite. Butler discloses that the operation of alkylation reactors under relatively moderate liquid phase conditions allows the use of relatively low benzene-ethylene molar ratios in the reactor of about 5: 1 or less and preferably 4: 1 or below about 2: 1. Larger ratios up to 15: 1 are also presented. Butler specifically describes a catalyst containing 80% crystalline omega zeolite and 20% by weight alumina binder.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided an aromatic alkylation process for alkylation of benzene containing feed material on the beta zeolite alkylation catalyst. The beta zeolite alkylation catalyst is formulated with a silica binder and has an average regeneration coefficient of at least 95% for at least three regenerations. The alkylation reaction is carried out in liquid phase or supercritical region with a C2 -C4 alkylating agent. In a preferred embodiment of the invention, the alkylating agent is an ethylating agent, but specifically ethylene. The catalyst exhibits a regeneration coefficient of at least 95% after ethylene of benzene with ethylene under a benzene / ethylene molar ratio of less than 10.

In a further aspect of the invention a benzene-containing feedstock is fed to a reaction zone containing a molecular sieve catalyst comprising a beta zeolite alkylation catalyst formulated with a silica binder. Ethylene is fed to the reaction zone which is operated under temperature and pressure conditions in which benzene is in liquid phase or in supercritical phase. Benzene ethylation occurs in an initial designated primary activity. Operation of the reaction zone is continued until the catalyst activity for benzene ethylation decreases around a value of at least 0.1% of the initial designated initial activity. This decrease in value shall not exceed 1% of the initial designated primary activity. The reaction operation for alkylation is terminated and a regeneration procedure is instituted. In the regeneration procedure the catalyst is regenerated in an oxidizing medium at an average temperature of not more than 500 ° C. At the conclusion of the regeneration procedure, the operation of the alkylation zone is reinstated with the reaction zone re-operated under effective temperature and pressure conditions to produce benzene ethylation in the liquid or supercritical phase. The initial catalyst activity in the second pass is such as to provide a secondary activity of at least 95% of the initial primary activity. Operation of the alkylation reaction zone continues until catalyst activity declines by at least 0.1% of the secondary initial activity and operation of the alkylation reaction zone is terminated again and the catalyst is subjected to a regeneration procedure as described above. At the conclusion of the regeneration procedure, benzene and ethylene are again fed into the alkylation reaction zone. The alkylation zone is operated at the temperature and pressure at which benzene is in the liquid or supercritical phase to provide an additional tertiary activity for benzene ethylation of at least 95% of the secondary activity.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a graph illustrating the volume percentage of a catalyst support at maximum temperature under liquid phase alkylation conditions employing a beta zeolite catalyst formulated with an alumina binder.

Fig. 2 is a graph illustrating the volume percent of a catalyst support at maximum alkylation temperature employing a regenerated beta zeolite catalyst formulated with a silica binder progressively under liquid phase conditions under progressively decreasing benzene / ethylene molar ratios.

Fig. 3 is a schematic illustration of a stage reactor system that may be used in carrying out the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves alkylation of an aromatic substrate comprising benzene in a reaction zone containing a beta zeolite alkylation catalyst which is preferably carried out under relatively moderate liquid phase alkylation conditions. The invention is especially applicable to ethylene benzene under moderate liquid phase conditions producing little or no xylene and the invention will be specifically described with reference to ethylbenzene production. However, other alkylation reactions may be used in carrying out the invention. For example, the invention may be applied to the reaction of propylene with benzene to produce cumene. Also, although olefinic alkylating agents will normally be employed, other alkylating agents such as alkynes, alkyl halides, alcohols, ethers and esters as set forth, for example, in Pat. No. 3,551,510 to Pollitzer et al. May be used.

As indicated above, the alkylation reactor is preferably operated under relatively moderate pressure and temperature conditions where benzene is in the liquid phase, that is, at a temperature well below the critical benzene temperature, and under enough pressure to keep the benzene in the liquid phase. However, the alkylation reaction may be carried out under conditions where benzene is in the supercritical phase, that is, under temperature and pressure conditions above the critical temperature and pressure, unless otherwise indicated in context. The terms "liquid phase" or "liquid phase reaction" as used in this invention shall be understood to mean operation in the supercritical region as well as in the liquid region.

The beta zeolite employed in the present invention may be conventional beta zeolite, or it may be a modified beta zeolite of any of several types described in greater detail below. Regardless of the nature of beta zeolite, the present invention proceeds in a manner contrary to the conventional procedure in which beta zeolite is normally heated with an alumina binder such as gamma alumina or catapal alumina. Thus, as described in more detail below, the beta zeolite employed in the present invention is formulated with a silica binder which results in a beta zeolite catalyst for use in liquid phase alkylation, which exhibits substantially better deactivation characteristics. and regenerating than beta zeolite formulated with a conventional alumina binder. Beta zeolite formulated with a silica binder exhibits a regeneration characteristic as described below after at least three regenerations which is at least 105% of the regeneration coefficient of beta zeolite catalyst formulated with an alumina binder being in the same amount as the silica binder employed in the catalyst.

The beta zeolite employed in the present invention may be a high ratio silica / alumina beta zeolite, a lanthanum modified beta zeolite or a ZSM-12 modified beta zeolite as described in detail below. This may of course also be a more or less conventional beta zeolite as set forth, for example, in the above mentioned Patents Nos. 3,308,609 issued to Wadlinger et al. And 4,642,226 issued to Calvert et al. Regardless of the nature of beta zeolite, it is formulated with a silica binder to provide a catalyst that is substantially more stable than beta zeolite formulated with an alumina binder in a traditional manner. In addition, the silica-bound beta zeolite catalyst of the present invention is stable at substantially lower benzene / ethylene ratios than is the case with a corresponding beta zeolite catalyst formulated with an alumina binder.

Beta zeolite is, as noted earlier, a well known molecular sieve catalyst and basic procedures for its preparation are well known to those skilled in the art. Procedures for the preparation of crystalline beta zeolite are set forth in US Pat. No. 3,308,069 issued to Wadlinger and others and 4,642,226 issued to Calvert et al. And European Patent Publication No. 159,846 issued to Reuben. , the descriptions of which are incorporated in their entirety by reference in this invention. Beta zeolite may be prepared to have a low sodium content, i.e. less than 0.2 wt% expressed as Na 2 O and the sodium content may be further reduced to about 0.02 wt% through of an ion exchange treatment.

As disclosed in the above referenced US patents issued to Wadlinger et al. And Calvert et al., Beta zeolite may be produced by hydrothermal digestion of a reaction mixture comprising silica, alumina, sodium or other alkyl metal oxides and an agent. Organic pattern. Typical digestion conditions include temperatures that vary slightly below the boiling point of water under atmospheric pressure to about 170 ° C at pressures equal to or greater than the water vapor pressure under the temperature involved. The reaction mixture is subjected to moderate agitation for periods ranging from about one day to several months to achieve the desired degree of crystallization to form the beta zeolite. The resulting beta zeolite is typically characterized by a silica to alumina molar ratio (expressed as S1O2 / Al2O3) between about 20 and 50.

The beta zeolite is then subjected to ion exchange with ammonium ions at uncontrolled pH. It is preferred that an aqueous solution of inorganic ammonium salt, for example ammonium nitrate, be employed as the ion exchange medium. Following the ammonium ion exchange treatment, the beta zeolite is filtered, washed and dried, and then calcined at a temperature between about 530 ° C and 580 ° C for a period of two or more hours.

Beta zeolite can be characterized by its crystal structure symmetry and X-ray diffraction patterns. Beta zeolite is a molecular pore size medium of about 5-6 angstroms and contains 12-channel channels. rings. Beta zeolite is tetragonal symmetry P422, a = 12.7, c = 26.4 Å (W.M. Meier and D.H. Olson Butterworth, Atlas of Zeolite Structure Types, Heinemann 1992, ρ.58); ZSM-12 is generally characterized by monoclinic symmetry. The beta zeolite pores are generally circular along plane 001 with a diameter of about 5.5 angstroms and are elliptical along plane 100 with diameters of about 6.5 and 7.6 angstroms. Zeolite beta is further described in Higgins and others, "The framework topology of zeolite beta", Zeolites, 1988, Vol. 8, November, pp. 446-452, the disclosure of which is incorporated in its entirety by reference in this invention.

The beta zeolite formulation employed in carrying out the present invention may be based on conventional beta zeolite as disclosed in the above-mentioned patent issued to Calvert or a lanthanum modified beta zeolite as disclosed in the above-mentioned EPA publication Shamshoum et al., or it may be a modified beta zeolite with a ZSM-12 crystal intergrowth, as disclosed in US Patent No. 5,907,073 issued to Ghosh. However, unlike the use of alumina binder as disclosed in Ghosh, a silica binder is employed as described in this invention. For a further description of procedures for producing beta zeolite useful in accordance with the present invention, reference is made to the above mentioned Patents Nos. 3,308,069 issued to Wadlinger, 4,642,226 issued to Calvert and 5,907,073 issued to Ghosh and EPA Publication No. 507,761 issued to Shamshoum, the disclosures of which are incorporated in their entirety by reference in this invention.

The present invention may also be carried out with a silica bonded beta zeolite based on a beta zeolite having a higher silica / alumina ratio than normally encountered. For example, as disclosed in EPA Publication No. 186,447 issued to Kennedy, a calcined beta zeolite may be de-illuminated by a steaming procedure to increase the silica / alumina ratio of the zeolite. Thus, as presented in Kennedy, a calcined beta zeolite having a silica / alumina ratio of 30: 1 was subjected to steam treatment at 650 ° C and 100% steam for 24 hours under atmospheric pressure. The result was a catalyst having a silica / alumina ratio of about 228: 1 which was then subjected to an acid wash process to produce a 250: 1 beta zeolite. Various beta zeolites, as described above, may be subjected to extraction procedures in order to extract aluminum from the beta zeolite structure by extraction with citric acid. Washing of zeolite beta with acid is performed initially to arrive at high ratio silica / alumina beta zeolite. This is followed by ion exchange lanthanum in the zeolite structure. Subsequent acid scrubbing should not be performed to prevent lanthanum removal from the zeolite.

In aromatic alkylation procedures it is highly desirable to regenerate the catalyst after decreasing its activity over time during alkylation procedure. In experimental work carried out in connection with the invention, silica binder-formulated beta zeolite was found to be substantially better regenerable than alumina binder-formulated beta zeolite according to conventional prior art procedures. Typically, during an alkylation procedure, new catalysts will exhibit relatively high initial activity that can be measured in terms of the percentage of ethylbenzene produced under a molar ratio designated benzene / ethylene and benzene space velocity. Desirably, activity will remain constant for an initial period, but at some point, due to catalyst co-qualification in the alkylation procedure, catalyst activity progressively declines. After catalyst activity declines to a level where additional operations are not possible or at least not economically practical, the reactor can be removed and the catalyst undergoing a regeneration procedure. A typical regeneration procedure involves the initial injection of nitrogen followed by the progressive increase of an amount of air added to the nitrogen until a desired oxygen content is reached. For example, an initial oxygen content may be about 0.5 vol% with the regeneration gas injected at a temperature of about 500 ° C. As the oxygen content is progressively increased, the coke is burned from the catalyst until the catalyst reaches a regenerated state where its activity is close to or sometimes even equal to the initial catalyst activity. In beta zeolite regeneration, it is initially desired to provide a nitrogen atmosphere at a temperature of about 500 ° C in order to substantially carry all hydrogen out of the catalyst prior to the introduction of oxygen to prevent generation. of water.

Catalyst regenerability can be characterized in terms of a regeneration coefficient indicating the level at which the catalyst can be regenerated (compared in terms of its initial activity) from one alkylation passage to another. Thus, considering multiple alkylation and regeneration passages, if the catalyst exhibits activity under a standard set of 10% ethylbenzene during a first pass, if the catalyst activity at the completion of a first regeneration step is 9%. of ethylbenzene under the same conditions at the beginning of the second alkylation pass, the regeneration coefficient will be characterized as 90%. If this same regeneration coefficient is observed from the second pass with a second interleaved regeneration to a third alkylation pass, the initial activity at the beginning of the third pass would be 8.1% ethylbenzene.

In describing the present invention, the term "regeneration coefficient" will be characterized in terms of the following standard conditions.

The catalyst is employed in a liquid alkylation phase procedure performed at a temperature and pressure of 300 ° C and 4.48 MPa gauge (650 psig) at a benzene / ethylene molar ratio of 10. The Ethylation Reaction It is performed until the catalyst activity, as measured by the percentage conversion of ethylene, declines around 0.5 percent. The catalyst is then regenerated by initially injecting nitrogen for a period of 24 hours at a temperature of 500 ° C after slowly increasing the oxygen content of nitrogen to 10% oxygen over a period of 24 hours. The initial catalyst activity at a second lease pass is then measured to achieve the secondary alkylation activity used to measure the regeneration coefficient. In experimental work with respect to the invention, the alkylation was performed employing a lanthanum beta zeolite formulated with alumina binder (Catalyst A) and formulated with silica binder (Catalyst Β). Lanthanum beta zeolite was prepared according to the procedure of EPO 507761 and had a silica / alumina ratio of about 100 and a lanthanum content of about 1% by weight. Experimental work was performed on a single-pass reactor under a temperature of 300 ° C and a pressure of 4.48 MPa (650 psig). The benzene feed had a purity of about 99% and was introduced at a spatial velocity (LHSV) of 70 h -1. Two sets of tests were performed, one employing 5 ml of catalysts on the catalyst bed and the other employing 10 ml of catalysts on the catalyst bed.

In an initial test set performed using Catalyst A (the alumina binder beta lanthanum), the catalyst bed temperature was measured as a function of time over two successive passes with an interleaved regeneration procedure. One set of tests was performed for the 5 ml catalyst bed activity and another for the 10 ml.

Alkylation operations were performed for five days for the 5 ml catalyst bed and four days for the 10 ml catalyst bed at the temperature detected by thermocouples spaced along the bed. The results of a first separation test performed with Catalyst A are shown in Fig. 1 in which the percentage of bed volume at maximum temperature (490 ° C), V, is plotted in ordinate versus time of operation. in days (D) traced on the abscissa. In Fig. 1, curve 2 shows the results for the first pass relative to the 5 ml bed and curve 3 shows the results of the second pass relative to the 5 ml bed. Curves 5 and 6 show the results for the first and second passes, respectively, across the 10 ml bed. The temperature was controlled at a maximum of 490 ° C during regeneration. For both 5 ml and 10 ml operations, beta lanthanum showed a higher rate of deactivation after regeneration than initially observed. Additionally, after a second regeneration, no activity was recovered, indicating that the beta lanthanum zeolite formulated with alumina binder was not stable enough to withstand multiple regenerations.

A second set of experiments was performed under critical phase conditions employing 20% silica binder beta lanthanum around the same amount of binder employed in the lanthanum modified beta alumina catalyst composition. Here, the alkylation operation was performed above the critical temperature (289 ° C) of benzene. The reactor temperature was 300 ° C, the pressure was 4.48 MPa (650 psig) and the benzene space velocity (LHSV) 70 h "1. The catalyst was stable at a benign / molar ratio. 10: 1 ethylene At the conclusion of an initial operation performed for 4 days, the catalyst was regenerated using the following regeneration procedure.

1. Allow cooling to ambient under minimum benzene flow;

2. Start purging with 240 sccm of nitrogen; keep the reactor in downflow mode;

3. Lower the temperature below 100 ° C / h to 400 ° C and maintain for 3 hours;

4. Cool it to 250 ° C;

5. Slowly add air at minimum rate Mass Flow Controller; do not allow the exotherm to exceed 490 ° C.

6. Once the initial rapid burn has been completed, the air is slowly increased over a period of 2 hours to 240 sccm while nitrogen is reduced to 0 sccm.

7. Raise the temperature to 485 ° C and keep it for 3 hours; and

8. Cool to room temperature with circulating air.

A second pass-through operation was then performed employing the regenerated catalyst with the benzene rate maintained at a space velocity of 70 h-1, and the ethylene rate progressively increased over time to produce benzene / ethylene ratios of 20: 1, 10: 1 and 7.9: 1. The results of this experimental work are shown in Fig. 2 where the percentage of bed volume, V, at the maximum temperature (490 ° C) is plotted in the ordinate versus the days, D, in the stream to the catalyst bed in the abscissa In Figure 2, curve 8 represents the data for the benzene / ethylene molar ratio of 20: 1, curve 9 for the benzene / ethylene molar ratio of 9 : 1, and curve 10, the curve for the benzene / ethylene molar ratio of 7.9: 1. As can be seen from an examination of the data shown in Fig. 2, the catalyst appears completely stable at the benzene molar ratios. / ethylene of 10: 1 and 7.9: 1, and even at ratios greater than 20: 1, stability has been shown to be substantially better. the alumina binder catalyst under a benzene / ethylene ratio of 10: 1. On the tenth day, the benzene space velocity was reduced and the additional ethylene flow reduced to provide a benzene / ethylene ratio of about 3: 5, at which point the catalyst immediately began to deactivate as indicated by curve 11.

Additional experimental work was performed with a silica binder beta lanthanum zeolite (Catalyst B) at benzene / ethylene molar ratios of 20: 1 and 10: 1 for four successive passages with intermediate regenerations. This experimental work was performed with beta lanthanum presenting a silica / alumina ratio of 50: 1. Temperature was controlled to a maximum of 490 ° C with a pressure of 650 psig (4.48 MPa) to operate in the supercritical region, thereby providing more severe reaction conditions than more moderate temperature and pressure conditions. involved in regular liquid phase alkylation. Each pass was performed under a 70 h'1 benzene feed LHSV. Between each pass the catalyst was regenerated by the same regeneration procedure as described above.

The results of this experimental work are presented in Table 1. As indicated, Table 1 shows for each pass the EB content, the percentage of diethylbenzene as measured against ethylbenzene in the production stream, the amount of butylbenzene in parts per million based on the ethylbenzene content, and the amount of propylbenzene in parts per million based on ethylbenzene in the product. As can be seen from an examination of Table 1, the catalyst maintained good activity after each regeneration, with fourth pass activity roughly equivalent to the initial activity. In the second regeneration performed between the second and third passages, an unexpectedly high coke burn caused the catalyst bed temperature to exceed the desired maximum temperature of 490 ° C for 40 minutes, reaching a high of 550 ° C. This led to propylbenzene yields increasing by an order of magnitude as shown in Table 1. However, as is evident from the experimental work described in this invention, the silica binder beta zeolite was much more stable and exhibited a coefficient of substantially better than the corresponding beta zeolite with alumina binder.

Table 1

<table> table see original document page 18 </column> </row> <table> Continued ...

<table> table see original document page 19 </column> </row> <table>

As noted above, silica binder beta zeolite catalysts are intended for use in liquid phase alkylation in accordance with the present invention. In carrying out the invention, the alkylation reaction is carried out under pressures well above the vapor pressure of the aromatic substrate at the reaction temperature involved in order to ensure that a liquid phase is retained throughout the reactor. In order to provide a complete liquid phase reaction, a flooded bed format is used in which the catalyst is completely immersed in liquid. This can readily be accomplished using an upflow technique as used in the prior experimental work, and this will usually be preferred in carrying out the invention. However, a downstream flooded bed operation can be performed by controlling the flow rate output to ensure that the catalyst beds are covered by liquid benzene or other aromatic substrate.

Preferably, a staged reaction format is employed to ensure good solubility of ethylene (or alkylating agent) in benzene (or other aromatic substrate) and provides for the entire reaction to take place in liquid phase. The staged reaction format may be provided by a plurality of catalyst beds on a single reactor by a series of sequentially connected reactors as set forth in the above-mentioned US Patent No. 5,073,653 issued to Butler . The multistage condition provides an opportunity for interstage cooling where adiabatic reactors are used or allows the use of various isothermal reaction stages. Turning now to Fig. 3, a schematic illustration of a staged reactor system used for ethylbenzene production by the ethylene-benzene reaction that includes a plurality of interstage cooling and ethylene injection reactors is shown. More particularly and as illustrated in the figure, ethylene and benzene are fed via lines 12 and 14 to the input line 15 of a dehydration unit 16. The dehydration unit functions to dehydrate the input to alkylation reactors so that it is essentially dry, desirably containing less than 100 ppm in water and more preferably less than 50 ppm in water. By way of example, dehydrator 16 may take the form of a column filled with a desiccator such as silica gel or other suitable hydroscopic medium or a known azeotropic column.

The effluent dehydrator is fed into a reactor 18, the first of a plurality of serially connected alkylation reactors operated in an upstream mode. Reactor 18 is operated at an average temperature of 350 ° C or less and preferably at an average temperature in the range 150 ° -250 ° C. For liquid phase operation, the pressure in reactor 18 is sufficient to maintain benzene in the liquid phase and preferably is at least 0.35 MPa (50 psi) above the vapor pressure of benzene at reactor temperature. Typically, the reactor pressure is in the range of about 3.45 - 5.86 MPa absolute (500 - 850 psia). Remaining downstream reactors typically operate under approximately the same conditions as the initial reactor. The effluent from the initial reactor 18 is drawn via line 19 and applied via a heat exchanger 22 where it is cooled before being fed to the second reactor stage 24. Ethylene is fed via line 21 where it is mixed with the first reactor effluent 18. Preferably, ethylene is fed to the effluent reactor prior to cooling as shown in the figure to facilitate ethylene distribution throughout the liquid benzene. Desirably, the cooling step is performed to reduce the temperature of the feed mixture fed to the second reactor 24 to a value around the same inlet temperature in the first reactor 18. The average temperature in the second reactor will usually be nearly same as that of the first reactor. The required pressure will be slightly lower to provide sufficient gradient pressure to accommodate flow through the system. The effluent from the second reactor 24 is fed together with ethylene provided via line 27 to a second interstage cooling unit 29 where the charge mixture to the third reactor 30 is again cooled to a temperature almost equal to the inlet temperature for the first two. reactors.

Reactor output 30 is fed via line 32 to a downstream separation and processing unit 34. At unit 34, ethylbenzene is separated and removed as a product of the alkylation plant. Typically, ethylbenzene will be used as the filler for a dehydrogenation system where it undergoes cataitic dehydrogenation in styrene production. Normally benzene and ethylene will be separated into unit 34 and recycled for use in the alkylation process. Heavier polyethylbenzenes may be transalkylated with benzene to produce additional ethylbenzene. A suitable multistage separation system together with a transalkylation system may take the form of one of the integrated systems set forth in EPA 467.007 mentioned above, the entire disclosure of which is incorporated by reference in this invention. Benzene to ethylene excess stoichiometry will be fed into the filler material to alkylation reactors in order to increase selectivity for monoalkylation. Reactor operation provides liquid phase alkylation under relatively moderate conditions not only minimizes the xylene produced in the alkylation reaction but also allows the use of a slightly lower benzene / ethylene molar ratio than is usually the case. Benzene / ethylene molar ratios as low as about 2: 1 may be employed, although ratios of about 4: 1 will usually be used. However, there is usually little incentive to use extremely high ratios, and as a practical matter the benzene / ethylene molar ratio will rarely exceed 15: 1. Preferred benzene / ethylene molar ratios are about 4/1. The above benzene / ethylene molar ratios are relative to the overall system, and for a multistage reaction system as depicted in the drawing, the benzene / ethylene feed ratio at each stage will be less than the overall ratio. The amount of ethylene solubilized benzene charge at each reactor stage will depend on the part in the number of reactor stages employed. Usually at least three reactor stages as illustrated will be used. Additional reactor stages will be provided although the total number of stages will normally not exceed 8. Preferably, the pressure at each stage of the region and the amount of ethylene fed is such as to provide at least 1 mol percent. solubilized ethylene in benzene. Usually, at least 2 mol percent of ethylene will be solubilized in the charge at each reactor. Unless many large reactor stages are employed, usually the amount of solubilized ethylene in the benzene liquid phase of each reactor will be at least 4 mol percent.

Multistage benzene ethylation may also be performed according to the present invention employing isothermal reaction zones. Isothermal reactors may take the form of shell and tube-type heat exchangers with the alkylation catalyst deposited on the tubes and with a heat transfer medium circulating through the shell surrounding the catalyst-filled tubes. The heat exchange medium will naturally be fed into the reactors at rates to maintain a relatively constant temperature throughout each reaction stage. In this case interstage cooling will be unnecessary although it is preferred to inject ethylene in front of each reaction stage.

As noted above, it is preferred to use the beta-silica catalyst in liquid phase alkylation reaction under relatively moderate conditions. However, the present invention will be carried out with an almost liquid phase-operated alkylation reactor with the benzene substrate under more severe conditions where both temperature and pressure are above the critical temperature and pressure for benzene operating in the supercritical region. As noted earlier, in this case the alkylation reactor would be operated at a temperature of about 290 ° or higher and an excess pressure of 4.82 absolute MPa (700 psia). Both higher temperatures and pressures will normally be employed. Here, operation of the benzene alkylation reactor in the supercritical region will be in the range of 300 - 600 ° C and about 4.48 - 5.86 absolute MPa (650 - 850 psia).

Having described specific embodiments of the present invention, it will be understood that modifications thereof may be suggested to those skilled in the art, and it is intended to cover all such modifications to the extent that they fall within the scope of the appended claims.

Claims (14)

Aromatic alkylation process, comprising: (a) feeding a benzene-containing feedstock into a reaction zone, and in contact with a molecular sieve catalyst comprising a beta-zeolite alkylation catalyst comprising - giving a lanthanum modified beta zeolite in which lanthanum ions are incorporated by ion exchange into the beta zeolite formulated with a silica binder and having a mean regeneration coefficient of at least 95% for at least three regenerations performed at a temperature not more than 500 ° C; (b) feeding a C 2 -C 4 alkylating agent to the reaction zone; (c) operating the reaction zone under effective temperature and pressure conditions to produce alkylation of benzene in the liquid phase or supercritical region by the alkylating agent; and (d) recovering alkylated benzene from the reaction zone. Process according to Claim 1, characterized in that the alkylating agent is an ethylating agent. Process according to Claim 2, characterized in that the ethylating agent is ethylene. Process according to claim 1, characterized in that the reaction zone is operated under temperature and pressure conditions in which benzene is in liquid phase. Process according to Claim 4, characterized in that the benzene and alkylating agent are fed to the reaction zone at flow rates to provide a molar ratio of benzene to alkylating agent of less than 15 µM. Process according to Claim 5, characterized in that the molar ratio of benzene to alkylating agent is less than 10. Process according to Claim 5, characterized in that the molar ratio of benzene to alkylating agent is in the range of 4-10. Process for the production of ethylbenzene, comprising: (a) feeding a benzene-containing feedstock into a reaction zone and in contact with a molecular sieve catalyst comprising a beta zeolite alkylation catalyst comprising a lanthanum modified beta zeolite wherein lanthanum ions are incorporated by ion exchange into the beta zeolite formulated with a silica binder; (b) feed ethylene the reaction zone; (c) operating the reaction zone under temperature and pressure conditions where benzene is in liquid phase or in supercritical phase to produce benzene ethylation in the presence of the alkylation catalyst at a primary activity. (d) recovering an alkylbenzene-containing alkylation product from the reaction zone; (e) continue operation of the reaction zone until benzene ethylation catalyst activity decreases by about 0.1% of the primary benzene ethylation catalyst activity; (f) terminating the operation of the reaction zone for benzene alkylation and instituting a regeneration procedure wherein the catalyst is regenerated in an oxidizing medium at an average temperature during the regeneration procedure of not more than 500 ° C; (g) subsequent to the regeneration procedure, reinstating the operation of the alkylation reaction zone by feeding benzene to the alkylation reaction zone; (h) operate the reaction zone under effective temperature and pressure conditions to produce benzene ethylation in liquid phase or supercritical phase to produce benzene ethylation in the presence of the regenerated catalyst to produce ethylbenzene under secondary activity of benzene. at least 95% of primary activity; (i) continue operation of the alkylation reaction zone until the catalyst activity for benzene ethylation declines around an amount of at least 0.1% of the secondary activity; (j) terminating the operation of the alkylation reaction zone and regenerating the catalyst in an oxidizing medium and at an average temperature of no more than 500 ° C to effect catalyst regeneration; (k) feeding benzene and ethylene to the alkylation reaction zone; and (l) operating the reaction zone under effective temperature and pressure conditions to produce liquid or supercritical phase benzene ethylation, to produce benzene ethylation in the presence of the regenerated catalyst to provide an initial activity for benzene ethylation of at least 95% of secondary activity. Process according to Claim 8, characterized in that the beta zeolite has a silica / alumina ratio of at least 40. Process according to claim 8, characterized in that the beta zeolite exhibits a regeneration coefficient after at least three regenerations which is at least 105% of the regeneration coefficient value of the beta zeolite catalyst formulated with an alumina binder in the same amount as the silica binder employed with beta zeolite. Process according to Claim 8, characterized in that the reaction zone is operated under temperature and pressure conditions in which benzene is in liquid phase. Process according to claim 11, characterized in that the benzene and alkylating agent are fed to the reaction zone at flow rates to provide a benzene to alkylating molar ratio of less than 15. Process according to Claim 12, characterized in that the molar ratio of benzene to alkylating agent is less than 10. Process according to Claim 13, characterized in that the molar ratio of benzene to alkylating agent is in the range 4-10.