AU9710498A - Composition useful in converting non-aromatic hydrocarbons to aromatics and olefins - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE

SPECIFICATION

(ORIGINAL)

Class Int. Class Cf., I Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Phillips Petroleum Company Actual Inventor(s): Charles Alfred Drake An-ilsiang Wu Address for Service: PHILIP oRmoNDE

FITZPATRICK

Patent and Trade Mark Attorneys 367 colins Street Melbourne 3004) AUSTRALIA Invention Title: COMPOSITION USEFUL IN CONVERTING NON-AROMATIC

HYDROCARBONS

TO AROMATICS AND OLEFINS Our Ref:- 563924 POF Code: 1422150647 method of performing it kno0wn to applicant(s): 2--veffogn, iud hf! he IP AUSTRAIJA

RECEIVED

14 DEC 1998

MELBOURNE

E--

BACKGROUND OF THE IVENTION The invention relate8 to a proess for converting non-aromatic hydrocarbons in the presence of an improved zeolite material to aromatic and lower olefin hydrocarbions. Also, ttie invcatior Mcato~ to thu reduction ia tire rabe of coke f~uioa dun the conveision of hydrocasbons in the presence of such impro-ved zeolite material It is known to catalytically crack non-aromatic gasoline boiling iange hydro carbons to lower olefins (such as ethylene and piopylene) and aromatic hydrocarbons (such as benzene, toluene, and xylenes) in the presence of catalysts which 10 contain a zeolite (such as ZSM-5), as is described in an article by N.Y. Chen et al in industrial Engineering Chemistry Process Design and Development, Volume 25, 1986, pages 151-15S. The reaction product of this catalytic crackin.!, proces3 contains a multitude of hydrocarbonas such as unconverted'Cs alkancs, lower alkanes (methane, ethane, propane), lower alkenes (ethylene and propylene), C 4 -Ce aromatic hydrocarbons (bentzeme, toluene, xylene, and etlrylbenzene), and C; aromatic hydrocarbons. Depending upon the relative market prices of the individual *reaction products, it can be desirable to inctease ihe yield of certain of the more valuable products relative to the others.

One concern with the use of zeolite catalysts in the conversion of hydrocarbons to aromatic hydrocarbons and low~er olefins is the excessive production of roke during the conversion reaction. Coke formed during the zeolite catalyzed aromatization of hydrocarbons tends to cause catalyst deactivation. It is desirable to improve the process for the aromatization of hydrocarbons by minimizing the amount of coke formed during such aromatization reaction processes.

SUMMAkRY OF THE INVENTION It is au object of this invention to at least partially convert hydrocarbons lo ethylene, propylene and BTX (benzene, toluene, xylene and ethylbenizene) aromatics.

A fuirther object of this invention is to provide anx improved procms for the conversion of hydrocabons in which the rate of coke formation during such conversion of hydrocarbons is ninimuized.

I7-

V.

One of the inventive processes provides for the conversion Of nonaromalic hydrocarbons to aromatic hydrocarbons and lower olefins by contacting a feed comprising at least one non-aromatic hydrocadbon conta~ining 5 to 16 carbon atoms per mnolecule selected from a group consisting Of alkanes, alkenes, cycloparaffiuas, and cycloalkenies with a silvIaled, acid-leached zeolite composition under effective contacting conditions such that the reaction product contains lower alkones contining 2-5 carbon atoms per molecules and aromatic hydrocarbons.

Another of the inventive processes provides for the, conversion of non-aroniatic hydrocarbons to aroinatic hydrocarbons and lower olefins by contacting a feed comprising~ at least a non-aromatic hydrocarbon containing 2 to 16 carbon atoms per molecule selected from a group consisting of alkartes, alkenes, cycloparaffins, and cycloalkenes with a silylated zeolite composition. that his preferably been steam-treated, under effective contacting conditionls such that the reaction product contains lower akenes containing 2-5 carbon atoms per molecule and aromatir. hydrocarbons.

Another embodiment of the invention is a composition used in the conversion of hydrocarbons comprising an acidI-leached zeolite material treated with a silylating agent and/or steam. This novel zeolite composition is made by leaching a zeolite material w ith acid to form an acid leached zeolite material and silylating the acid leached zeolite material with a silylating agent. The silylated, acid leached zeolite is effective in increasing the ratio of olefin to aromatics and reducing the rate of coke formutio durin use in converting hydrocarbons to aromatics and Another inventivye composition used in the conversion of hydrocarbons comprises a 7eolite material treated with a silylatiug agent with the silylated zeolite material preferably being treated with steam. Tis novel zeolite composition is made by silylaling a zeolite material with a silylating agent to form a silylated zeolite material. The silylated zeolite material can be treated with steam to thereby form a steam treated, silylatcd. zeolite material. The steam treated, silylated zeolite material provides for a high yield of olefins and aromatics wit a low rate of coke formation when used in converting gasoline to aromatics and olefins.

Another of the inventive compositions includes a zeolite material treated once with a silylating agent to give a oneme-.silylated zealite material.

Prefe~rably, the once-silylated zeolite material is further treated with steam to give a steam treated, once-silylated zeolite. The once-silylated zeolite material and the steam treated, once-silylated zeolite material are. particularly useful in the aromatization of hydiocarbons to provide a high yield of BTX aromnatics with a low rate of coke production.

In accordance wNith the present invention there is provided a method of making a composition for use as a zeolite catalyst effective in increasing the ratio of olefins, to aronmatics and in reducing the rate of coke formation during uise of said zeolite catalyst in converting gasoline to said aromatics and said olefins, said method consisting essentially of. impregnating a zcolite starting matcrial with a silylating agent; and drying the impregnated silylated zeolite material to produce a composition in which the silylating agent is present in the zeolite starting mate-rial in an amoutnt upwardly to 50 weight percent of the zeolite starting material- Other objects and advantages of the invention will become apparent from the detailed description and the appended claims.

DETAILED DESCRIPTIIN OF THE TNVEbNIO It has been unexpectedly found that the inventive composition comprising an acid leached zeolite- treated with a silyloting agent, whcn used in the 20 conversioni of hydrocarbons particularly in the aromatization of a gasoline product fron a catalytic oil cracking unit. provides for a significant improvement in the weight ratio of olefins to RTX aromatics with a very lo'%v Tate of coke forrnation.

The inventive silylated, acid leached zeolite composition utilizes a zeolitc starting material which is treated, or prefer-ably leached with an acid compound. This acid treated. or leached. zeolite material is then treated with a silylating agent to thereby incorporate silicon into the acid treated zeolite and provide a silylated, acid treated zzolite composition that is effective in providing an improvement in the weight ratio of olefins to aromatics wvith a low rate of coke formation during its use in converting gasoline to olefins and aromatics.

1Anyv suitble meains can be used to treat the zeolite starting material with acid. It is preferred for the zeolite to be soaked with an acid solution by any suitable means knon in the art for contacting the zeolite with such acid solution.

I A-i -4- The acid solution used to treat the zeolite mat be a solution of any acid that suitably provides for the leaching of aluminumn atomns from the zeolite erystalline structure.

Examp~les of such suitable acids include sulfuric, Phosphoric, nitric and hydrochloric. The preferred acid solution is aqueous hydrochloric acid. The zeolite is soaked in the acid solution for a period of from about 0.25 hours to about 10 hours.

After soaking, the resultant acid treated zeolite is washed fiee of the avid and then can be dried or calcined, or both.

The acid treated zeolita is then silylated by treatment with a silylating agent. The silylating agent can be any suitable silicon contaning compound that 10 effectively treats tile acid leached zeolite so as to provide a silylated, acid leached zeolite that is effective in giving an improved weight ratio of olefins to aromatics wiha low rate of coke formation when used in converting gasoline to aromatics and olefins. Mfore particularly, the silylating agent is an organosilicon compound Selected from compounds hating the following- molecular formulas: SilR., and (R.Si) 2 wherein: 6* w i to 3; *R alkyl, aryl, H. alkoxy, arylalkyl, and where R has from I to i 20 10 carbon atoms.- X halide; and.

z= oxygen or imino or alkylimino or alkanoylimino.

The preferrd silylating agent is selected from the group of tetra alkyl orthosilicates, Si(OR) 4 and poly(alkyl)siloxane.. The most preferred silylating 2$ agents are tetra ethyl orthosilicate and poly(phenyl methyl)siloxane- The pieferred method of silylaling the acid treated zeolite is to impregnate it with a solution of the silylatingoz agent by any standard incipient wetness technique known in the art. The solution may be an aqueous solution or a hydrocarbon solution of the silylating agent. it is preferrd, however, for the silylating agent to be insoluble in w~ater but soluble in hydrocarbon. Any suitble hydrocarbon solvent can be used including, for example, aromatics and other hydromabons having firom 4 to 10 carbon atoms per molecule including alkanes, cyclo,alkanes and olefins. The mast preferred hydrocarbon solvent is cyclohexane, The concentration of silylating agent in the solution can range upwardly to the solubility ~~iTof the silylating agent in the solvent. P~referably, the concentration of the silylating agent in the solution can be in the range front about 1 weight percent to about 99 weight percent. Most preferr4d the concentration of silylating agent in the solvent is from 5 to -25 wveight percent.

The amount of silylating agent incorporated into the acid treated zeolite should be such as to provide a silylated, acid leached zeolite that effectively -provides a suitably high weight ratio of olefin to aromnatics with a low rate of coke- 10 formation during its use in, The conversion of gasoline to aromatics and olefins.

Generally, the silylatingq agent can be present in the ac-id leached zeolite in an amnount upwardly to about 50 weight percent of the acid leached zeolite- Preferably, the amount of silylating agent incorporated into the acid leached zeolite can be in the range of from. about 0.5 weight percent to about 40 weight percent and, most preferably, from 5 weight percent to 25 weight percent.

After the incorporaion of silylating agent into the acid leached zeolite, the thus impregnated acid leached zeolite can be dried at suitable drying -ondito, geealy in the presence of aix, and then calcined. The drying V. temperature generally ranges from about 20"C to about 125'C and is generally 20 preformed over a time period of from 0.1 hours to 4 hours. Thle calcination temperature is generally in the range of from about HOTC to about 700TC. The calcination can be performned in an air atmaosphere for a time period of from 0.1 hours to 10 hours.

Another of the inventive compositions includes a zeolite material treated with a silylating agent to give a silylated zeolito material. Preferably, the silylated zeolite material is further treated -w~qith steam to give a steam treated, silylated. zolite. Thze sitylated zeolite material and steam treated, silylated zeolite material are particularly useMii in the aromatization of hydrocarbons to provide a high yield of BTX aromatics with a low rate of coke production.

To prepare the silYlated zeolite material, a zeolite starting material is silylated by treatment 'with a silylating agent The silylating agent can be any suitable silicon containing compound that is effective in providing a high BTX yield, preferably an improved BTX yield over other zeolite catalysts, and a low rate of coke formation when used in converting gasoline to aromatics and olefins. The more desirable silylating agents incluides organosilion compounds as described earlier herein among which tetra alkyl orthosilicates and poly(aikyl) siLoxane are preferred. The most preferred silylating agents are tenr ethyl orthosilicate and poly(phenyl methyl) sitoxne- The preferred method of silylating the zcolite starting material is with a solution of the silyvlating agent by any standard incipient wetness technique knownn in the art. Suitable sitylating solutions are as described earlier herein- It is preferred to impregnate the zeolite starting material with a sufficient amnount of silylating agent that effectively provides for an improved BTX yield when the silylated zeolite is utilized in the conversion of gasoline to aromatics and olefin.

To achieve- this benefit, generally, the silylating agent van be present in the zeolite starting material in an amount -upwardly to about 50 weight percent of the zeolite staiting material. Preferably, the amnount of silylating agent incorporat", in the zeolite starting material can be in the range of from about 0.5 weight percent to about 40 weight percent and, must preferably, from 5 we ight percent to 25 weight percent.

After the incorporation of silylating agent into the zeolite starting material. the silylated zeolite can be dried at suitable drying conditions, generally in the presence of air, and then calcined. The drying temperatures generally range from about 20 9 C to about 125'C and is generally performed over a time period of from 0.1 hours to 4 hours. The calcination temperaiture is generally in the range of from about 3WOC to about 70CC. The calcination can be performued in an air atmosphere for a time period of from 0.1 hours to 10 hours- The silyiated zeolite material can preferbly be steamn treated to gv a steam treated, silylated zeolite composition. The silylated zeolite material c= be steam treated by anky suitable method known in the adt. Generally, the siylated zeolite material is exposed to an atmosphere of steam for a period of time sufficient to provide a steam treated, silylated zeolite composition that is usefu in the- aromatization of hydrocarbons and provides for an improved yield of BTX aromatics with a low rate of coke production. The steam temperature can generally be in the range of from about lO00C to about 9000C under a pressure in the range of from Subatmospheric to about 3000 psia. Preferably, the steam is not a saturated steam but is superheated steam in the temperature range of from about 1251C to about 750*C and, most preferably, frm 15VC to 70(tOC The silylated zeolite is exposed to the S steam atmosphere for a period sufficient to provide the desired properties but, geealupwardly to about 20 hours-. Preferably, the silylated zeolite is tMated with steam for a period of from about 0.5 hours to about 15 hio=r and, most preferably &rm 1 hour to 10 hours.

The zeolite starting material used in the composition of the invention can be any zeolite which is effective in the conversion of non-aromaiftics to aromnatics when contacted under suitable reaction conditions with non-aromatic hydrocarbons. Preferably, the zeoite has a constraint index (as defned in U.S.

Patent 4,097.367, which is incorporated herein by reference) in the range of about 0.4 to about 12, preferably about 2-9. Generally, the molar ratio of SiC) 2 to A1 2 03 in the crystalline framnework of the zeolite is at least about 5:1 and can range up to infinity. Preferably the molar ratio of SiOj to A120 3 in the zeolite ftiuework is a about 8-1 io about 200:1, raore preferably about 12:1 to about 60:1. Preferred zeolites include ZSMS. Z.SM-8, ZSM-11, ZSM-l.2, ZSM-35, ZS-M-39, and mixtures 20 thereof. Some of these zeolites are also knowni as "IT'or PentasTl"zeolites.

The presently mo-re preferred zeolite is V* t The inventive compositions described herein can also contain an inorganic binder (also called mafrix material) preferably selected from the group consisting of alumina silica, alumina-silica, aluminum phosphate, clays (such as bentonite), and mixtures thereof. Optionally, other metal oxides, such as magnesia, ceria, thoria, titania, zirconia, hafii, zinc oxide and mixtures thereof, which enhance the thermal stability of th catalyst composition, may also be present in the catalst composition.

The content of the zeolite component o f the zeolite compositions is about 1-99 (prfably about 5-80) weight-%/, and the content of the above-listed inorganic binder and metal oxi de materials in the zeolite is about 1-50 weight-%4.

Glenerally, the zeolite component of the zeolite compositions has been compounded iwith binderLs and subsequently shaped (such as by pelletizing. extrurlng or I tableting). Generally, the- surface area of the compounded zeolitt composition is about 50-700 m'Ig and its particle, size is about 1-10 mm.

Any suitablte hydrocarbon feedstock -which comprises paraffins (alkanies) andlor olefins (alkenesj) andior naphthenies (cycloalkafles), w.herein each of thest hydrocarbons contains 2-16 carbon atoms per molecule can be used as the fwed to be contacted wvith the inventive zeolite wompositiofs unmder suitable process conditions for obtaining a reaction product comprising lower alkenies containing c=bon atoms per molecule and aromatic hydrocarbons. Frequently, these feedstocks also contain aromatiz hydrocarbons. Non-limiting examnples of suitable, available 10 feedtooks include gasolines from catalytic oil cracking FCC and hydrcracking) processes, pyrolysis gasolines from thermial hydrocarbon ethane V.propane, and naphitha) cracking processes, naphthias, ga3 oils, reformates straightrun gasoline and te like. The preferred feed is a gasoline-boiling range hydrocarbon feedstock suitable for use as at least a gasoline blend stock generally- having a boiing range of about 30-210TC. Generally, the content of pmAffins exceeds the combined content of' olafins naphthenes and aromatics (if present).

*The hydrocarbon feed stream can be contacted by any suitable manner .i0h the iniventive 7eolite compositions describ.Ad herein eontained within a reaction zone. T he contacting step can be operated as a batch process step or, preferably, as a continuous process step. In the latteroprtoasldcalsbe or a movin catalyst bed or a flUdized catalyst bed can be employed. Any of these operational modes have advantages and disadvantages, and those skilled in the art can select the one most suitable for a particular feed and atalyst. No significant amount of hydrogen gas is required to be introduced -Aith the feed into the -reaction zone of the contacting step, iLe.. no Hz gas at all or only insigoificant trace amounts -of H, less tha about I ppm H 2 Nhich do not significantly affec-t the processes are to be introduced into these reactors frm an external source.

The contacting step is preferably carried out within an aromatization reaction zon'e, wherein is contaned the novel zeolite composition, and under reaction conditions that suitably Promote the aromatizalioft. of at kast a portion of the hydrocarbons of the hydrocarbon fed The reaction temeratmr of the contacin step is more particularly in the range of from about W00C to about m I 11 -9- 900 0 C, preferably, fron about 450'C to aboout 75O04C and, most prefkrably, from 500CC to 700 0 C- The contacting pressure can rang. from subatmospheric pressure upwardly to about 500 psia, preferably, from about atmospheric to about and, most preferably, from 20 psia to 400 psia.

S The flow rate at which the hydrocarbon feed is chargd to the aromatzation reaction zone is such as to provide a -weight hourly space velocity C'WHSV") in the range of from exceeding 0 hour' upwrdly to about 1000 hole'.

The term "weight hourly spac velocity," as used herein, shall mean the numerical ratio of the rate at which a hydrocabon feed is chard to a reaction zone in 10 pounds per hour divided by the pounds of catalyst contaned in the reaction zone to whichi the hydrocarbon is charged- The preferred "WHSV" of the feed to the Contacting zone can be in the range of front about 0.25 hour" to about 250 houf? and, most preferably, from 0.5 hout" to LOO hour' 1 The following examples arc presented to further illustrate this invuntion and are aot to be construed as unduly limiting its scope- EXANIRLE I .*This exuumple illustrates the preparation of several catalysts which were subsequently tested as catalysts in the conversion of a gasoline sample, which had been produced in a commercial fluidized catalytic cracking unit (FCC), to 20 aromatics- Catalys Aw a commercial HZM-5-containing catalyst, extrudate which was supplicd by Chemi Uetikoa AG, Ietikon, Smwitzerland, under the product designation "Zeooae' PZ-2150 PF. This catalyst contained 97.0 weight-Ve SiO,2.9 weight-%/ AlrO03 and Q-1 weight-% Na 2 all determined on an anhydirous bisis; having a SiO 2 A1 2

O

3 mole ratio of about 50:1, a BET surface area of about 400 mn~Ig. The extudate had an approximate diameter of 1/16 inch and length of 3/16 bIch Catalyst Awas calcind inair at5381C for 2to 4 houbefore itwasused in the aromatization tests described in Example HI.

Catalyst B was prepared by impregnating (by incipjit wetness) 15.0 gram of Catalyst A with 7.9 grams of a 20 weigh-% solution of tetraethyl orthosilicate (also knovmi as tetraethoxysilane; TEOS) in cyelohexae; drying the TEOSimpresnaed Catalyst A magtedral at toom temperatue for about 3 hours; heatig the -9 800 0 C, preferably, fromn about 4500C to about 750'C and, most preferably, from 500'C to 700 0 C. The cortacting pressure c~an range from subatmospheric pressure upwaidly to about 500 psia, preferably, from about atmospheric to about 450 psia and, most preferably, from 20 psia to 400 psia.

The flow rate at which the hydrocarbon feed is charged to the aromatization reaction zone is such as to provide a weight hourly space velocity ("WHSV") in the range of from exceeding 0 hour'1 upwardly to abou.t 1000 houf' Th Nem"eight hourly space velocity," as used herein, shall mean the numerical ratio of the rate at which a hydrocarbon feed is charged to a reaction zone in 10 pounds per hour divided by the pounds of catalyst contained in the reaction zone to 'which the hydrocarbon is charged. The preferred "WI-ISV" of the feed to the contacting zone caun be in the range of fromn about 0.25 hour" to about 250 hour" and, most preferably, from 0.5 howr' to 100 hout".

The following examples are presented to further illustrate this invention and are not to be construed as unduly limiting its scope.

EXAMPE-UhI This ex~anple illustrates the preparation of several catalysts which were subsequently tested as catalysts in the conversion of a gasoline sample, which had been produced in a commercial fluidized catalytic cracking unit (FCC), to 20 aromatics.

Catalyst Awas a commercial HZSM-5-contaning catayst extrudate which was supplied by Chemi Uetikon AG, Ueftkon, Switzerland, under the product designation 4"Zeocate PZ-2130 This catalyst contained 97.0 weight-%/ SiO 2 2.9 weight-% A1,03 tund 0- 1 weight-%o Na 2 O, all determined on an anhydrous biesis; having a SiO2:AlO, mole ratio of about 50:1, a BET surface area of about 400 tn The extrudate had an approximate diameter of 1/16 inch and length of 3/16 inh aayst A was calcined in air at 53811C for 2 to 4 houis before it was used in the aromatization tests described in Example II.

Catalyst B was prepared by impregnating (by incipient wemness) 15.0 grams of Catalyst A with 7.9 grams of a 20 weight-% solution of tetraethyl ortho.

silicate (also known ats letraethwxysilanic; TEOS) in cyclohexan; drying the TEOSirupzegnaWe Catalyst A material at room tempera=ur for about 3 hours; healing the dried material in air so as to increase its temperature from room temperature to a fi temperature of 538TC at a. rate Of IOclinnute; alingteaerlfr6 hours in air at 5386C; cooling the calcined materiel to room temIperatur; imp1egnating the cooled, calciined material with 8.0 grams of a 25 weight- 0 /6 solution of TEoS in cyclohexane; drying/calcininlg ihe twice-impregnated (iLe., twice-silylated) material, as described above; cooling, impreg ating the calcined, twice-silylated material with 8.0 grams of a 25 weight-% solution of TEOS in cyclohexane; and finally drying/heating the trice-impregnated (iLe., tiarice-silylated) material, as a described above to provide a thrice-silylated zeolite. Catalyst B weighed 16.34 grams~, and thus had gained 1.34 grams in weight (as SiO,).

~gatalgsC was prepared by treating 10.89 grams of Catalyst B with 100% steam for 3 hours at 325 0 C, followed by cooling the steamed treated, thricesilylated zeolite in a helium gas streamn (flow rate: 100 c/minute) to provide a steam treated, thrice-silylatel zeolite.

Catalyst D was prepared by impregnating (by incipient wetness) 15.0 gras of Catalyst A once with 8.0 grams of 70 weight-%/ solution of tetraethyl.

orthosilicate (also known as tetraethoxysilane; TEOS) in cyclohexane; drying the TEOS-impregnated Catalyst A material once-silylated Catalyst A material) at room temaperature for about 3 hours; and then calcining the material for 6 hours in air at 53ST to provide a once-silylated zeolite. Catalyst D weighed 16.42 grans, and thus had gained 1.42 gramis in weight (as SiQ 2 !Catyst B was prepared by treating Catalyst D with 100% steam for 3 hours at 325 0 C, followed by cooling the steam treated, once-silylated zeaolita in a helium gas stream (flow rate: 100 eclrinute) to provide a steam treated, once silylated zeolite. EXAMPLE 11 This example illustrates the use of the zeolite. materials described in Example I as catalysts in the conversion of a gasoline feed to beraene, toluene and xylenes (BMX and lower olefas (ethylene, propyleneb).

A sample of 5.0 g of each of the catalyst matefials described in, Example I was, placed into a stainless steel tube reactor (length: about 18- inches; inner diameter; about 0.5 inch). Gasoline (density: 0,73 glcc; containing about 4.2 11 weight-%/ C4-C,3 norma] paraffins, about 25.4 weight-%/ C,-Ci) isoparaftins, about 25.4 weight-%

C

4 -'Cg Oletimls, about 9.5 wveight-% Cs-Cj? naplitbenes and about 32.7 wcight-%C 6 -CI2 aromatics) from a catalytic cracking unit of a refinery was passed through the reactor at a flow rate of about 10.0 g9'hour, at .a temperature of about 600 0 C mid at atmospheric Pressure (about 0 Psig). Thus, the weight hourly space velocity (WIASV) of the- liquid feed was about 2.0O g feedig catalyst/hour. The formed reaction product exited the reactor tube and passed through several icecooled taps. The liquid portion remained in ihese traps and was -weighed, whereas the volume of the gaseous portion Maich exited the traps Nwas measured in a "wect test meter". Liquid an~d gaseous product samples (collected at hourly intervals) Nvere analyzed by means of a gas cbrornatograph. Results of five test runs for Catalyst A, V. B, C, D, and E are summarized in Tuble 1. All test data wer obtained after 8 bours on streamn.

C S

S

*4 S

S.

6 S S Sn S S .5 .5 1 S

*S

S

S

S. S

S

TABLE I C-tla.ProdJuct coke 1i C.

4

C

3 Y11 6 Others' BTXZ Heavies? Other' hour) ~Leam treaed, lia illtd elt B25.5 20.2 24.9 30.4 61.4 2879 10.7 0.3 E30.2 9.5 20.5 29.8 64.8 26.3 8.9 0.6 'Mainly methane, ethane, propane and hydrocarbols; minor amounts of n-butane. isobutane and bifleles.

2 B3enzene. toluene, and xylenes; mninor amounts of ethylbenzene.

lpriznarily aromatic hydrocarbons containing miore than 8 C atoms per molecule.

'Primarily C.-CS parafims sCumuAntive increas in weight of catalyst divided by duration of test (8 houIn).

1~ 1.

4* IS *11141

S

S.)

S. I S

S

a 13 Test data in Table I clearly shoIw the Catalysts B and C, Avich have been treated more than once with tetraothyl orthosihicate flui-cesiylated), ehibited considerably less coking Than 0011troI Catalyst A which had not been ,jete 'Futtath l~ to il~ t. T rthero re, higher yields of BTX arom tics wvere obtained when thtice-silylated Catalysts B and C were used. An additional increase in BTX yield was achieved by steam treatment after the MultiPlesteP treatment with tetraethyl orthosilicate (compare run using steam, Ohic-silylated Catalyst C versus rn using tbrce-silylatod Catalyst

B).

Test data in Table I also clearly show that CaitalySts 1) nd. E, which have been treated once with tetraothyl orthosilicate ouce-silylated), exhibited considerably less coking than control Catalyst A which. had not been treated.

Furthemrme, higher yields of BIX aromatics were obtained when once-silylated Catalyst D and F, were used. An idditional increase in BTX yield was achlieved by steam treatment after the single-step treatmnt with tetraethyl orthosilicate (comepare run using steam treated, once:-silylated Catalyst B versus tun using once-sllylateki Catalyst

D).

Further, test data in Table I also clearly show that Catalysts D and E, which have been treated once with tetraethyl orthosilicale Ooe-silYlated), exhibited coking amo-ants and yields of olefins and BTX aromeatics sim~ilar to those 20 ekhibited by Catalysts B and C, which have been treated mnore than once with tetraethyl orthosilate tbrice-silylated). Thus, a benefit of the invention is the ability to treat the zeolite once with tetraethyl orthosilicate and obtain a comfpositionl tat works as well, if not better than, a zeolite treated more than once wAith lttl ortliosilicate ,Wich results in less preparation time and cost.

This example describes the two preparations of zeolite used in the aromatization rection runs of Example;

W.

A commercially available ZSM-5 catalyst (provided by United Catalysts Inc., Louisville, KY, under product designation was treated by acid leaching. To acid leach the catayst, it was soaked in an aqueous HCI solution, baving a concentration of 19 weight percent HCI, for two hours at a constant temperature Of about'90-C. Aftr soaking, the cataySt was separated from the acid -14solution and thioroughly washed with water and dried. The acid so"ke, washed and dried catalyst was calciiied at a temperature of about 500'C for four hours. This acid leached ZSM-S catalyst wais used in the aromatization reaction runs as described hereafter to determine the coking r-ate related to its use.

The acid leached ZSM-5 zeolite described above Aw treated with a silylating agent by using an incipient wetness technique to impregnate it 'with a weight percet solution of poly(methyl phenyl) siloxane with cyolohcxane as the solvent. The impregnated, acid leached ZSM=5 was dried for two hours folowed by calcination at 5309C for six hours. This silylated and calcined acid leached 10 ZSM-5 catalyst was used in an aromatization reaction run as described hereafter to determine the product yield and coking rate related to its use.

V. EXAMPLE

IV

This example illustrates the benefit of reduced coke formation rate and improved glei-to-BT product ratio that result form the inventive use of the iventive silylated, acid leached zoolite in the conversion of hydrocaxbons to olefins.

The standard T-44S0 zeolite and the two zeolite preparations described in Example Mli were used in three Teaction. runs the results of which are summnarized in Table 11.

Table 11 provides comparisons of the results from the use of the standard zeohite and acid leached zeolite with the results firm the use of the inventive silylated, acid 20 leached zeolite.

For each of the reaction test runs, a sample, of 5 g of the particular zeolite catalyst preparation mixKed with about S cc 10-20 mesh alumina Nw placed into a stainless steel tube reactor (length:. about 18 inches; inner diamete about inch). Gasoline from a catalytic cracking unit of a refinery was passed through the teactor at a flow rate of about 14 rnllhour, at a temperature of about 600*C and at atmospher pressure (about 0 psig. The formed reaction product exited the remcor tube and passed through several ice-cooled traps. The liquid potion remained in these traps and was weighed. whereas the volume of the gaeous portion which exited the traps was measured in a 'wet test meter." Liquid and gaseous product samnples were periodically collected and analynzed by means of a gas chramtograph.

After the reaction runs were completed (approximately 8 hours on stream) the colting rate was determined by measuring the amount of coke deposited on the

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sudface of the catalyst. The coking rate: and product olefin-to-TX ratio results of the three test runs for the catalysts described in Example III ar suwawaized in Table UI.

T-4480 Zoolite045.3 4 0 Acid Leached Zeolite 0.31 1.74 Silylated, Acid Leached 0.88 0.46 Zeolite to As can be seen from the coking Tate data presented in Table II, the use of a silylated, acid leached zeolite in the conversion of hydrocarbons resulted in a significantly lower coking rate than that of the zeolite or acid leached zeolite, Also, a significant improvement in the olefi-to-BTX ratio in the reaction product is achieved by 'using the silylated, acid leached zeolite.

As used in the claim,% "consisting essentilly of" is intended to mean that the method does noi contain any further steps which would materially affect the desired object of the invention.

Claims (9)

1. A method of making a composition for use as a. zeolite catalyst effective in increasing the ratio of olefium to aromatics and in reducing the rate of cokec formation during use of said zeoiite catalyst in converting gasoline to said aromatics and said olefins, said method consisting essentially of- impregnating a zeolite starting material with a silylating agent; and dryingL the. impregnated silylated zeolite material to produce a composition in which the silyinting agent is present in the~zcollte starting material in an amount upwarly to 50 weight percet of the zeolite starting material.

2, A method according to claim 1, wherein the amount of the silylating agent incorporated in the zeolite starting material is in the range of from. 0.5 to Weight percent of the zeolite starting material.

3- A method according to claim 2, wherein the amount of the silylating agent incorporated in the zeolite starting material is in the iange of from 5 to weighlt percent of the zeolite starting material.

4. A method according to anyone of claim 1-3, wherein said silylating agent is an organosilicon compound.

S. A method according to claim 4, wherein sai d organosilicon compound is tetra alkyl orthosilicate, or poly(phanyl mnethyl) siloxane-

6. A method according to anyone of the preceding claims, wherein the dried silylated zoolite material is contacted with steam at a temperature in the range of frm l000C to 900 0 C for a period of from 0.5 to 15 hours,

7. A method according to any one of the precding claims, wherein the dried silylated zeolite material is calcined at a temperature in the range of O~T to 1000C for a period of from 0.1 to 20 hours.

8. A method of converting non-aromatic hydrocabons to aromatic hydrcaronsand lower Olefins wich comprises wmonting a feed comprising at least one non-aromatic hydrocarbon contaig 2-16 carbon atom pI= mOlecule which is alkane, aikene or cycloparaffin 'with a composition produced according to any one of the precding claims under contact& conditions effective in obtaining a rcaWCiOn product comprising lower alkenes containing 2-5 carbon atoms per molecule and aromatic hydrocabons. f -17-

9. A method of making a composition for use as a zeolite catalyst substantially as herein described. A composition when made by a method according to any one of the preceding claim substantially as herein describcd. ii. A method of converting non-aromatic hydrocabons to aromatic hydrocarbons and lower olefins substantially ws herein described. DATED: 11 December, 1998 PHILLIPS OR1MOIUE FITZPATRICK Attorneys for: PHILLIPS PETROLEUM COMPANY C. 9