JP4713716B2 - Selective xylene isomerization and ethylbenzene conversion process - Google Patents

Description

【００４９】
この供給原料を１．３ＭＰａの圧力、１０ｈｒ^-1の質量時間空間速度、そして水素／炭化水素モル比４の条件下で異性化した。反応器温度を１回通過させる度にエチルベンゼンの消失することで示される転化レベル範囲に調整した。エチルベンゼンは少量のキシレン・ロスを伴って、主にベンゼンとトルエンに転化され、少量の軽質ガスの発生も認められた。エチルベンゼン転化率６５％での、貴重なキシレン・ロスを比較したテスト結果を以下に要約して示す。

【００５０】
本発明で用いられる触媒Ａは先行技術で公知の触媒と比較して、どの異性化条件ででも、より低いキシレン・ロスを示した。本発明で用いられる触媒Ａ’は約６５％程度のエチルベンゼン転化を達成するのに必要な低温に示されるような例外的な程の活性と、先行技術の触媒と比較しての低いキシレン・ロスとを示した。転化率の関数としてのキシレン・ロス及び活性で示される触媒Ａ、Ｘ及びＹの相対的な性能を図１に示す。
【００５１】
実施例６
白金族金属の濃度の異性化プロセスにおける性能に対する影響を比較するために本発明による一連の触媒を調製した。約６７質量％のゼオライト含有量を有するか焼された球を実施例１で述べた手順に従って調製し、水蒸気処理した。その後、塩化テトラアミン白金溶液を用いてそれらの球に含浸させ、乾燥、酸化、還元した。これらの球の名称とその白金含有量を質量ｐｐｍとして下表に示す。

【００５２】
実施例７
種々の白金含有量を有する本発明による触媒の異性化性能をモル％で以下の組成を有する不均衡Ｃ₈芳香族化合物供給原料を処理するパイロット・プラントを用いて比較評価した。

【００５３】
この供給原料を圧力１．３ＭＰａ、質量時間空間速度１０ｈｒ^-1、及び水素／炭化水素モル比４の反応条件下で異性化した。パラ−キシレン／キシレンの比率は約２３．９％に達した。反応温度は１回の通過あたりのエチルベンゼン消失で示される一定の範囲の転化レベルを起こすように調製された。エチルベンゼン転化率６５％での、貴重なキシレン・ロスに関するこれらのテストの結果は下表に示す通りである。

【００５４】
キシレン・ロスは白金含有量が４００質量ｐｐｍ以下の場合に最も低かった。
触媒活性は約４００質量ｐｐｍ以上の触媒白金含有量の場合、より好ましい結果を示した。
【００５５】
実施例８
一連の触媒を調製しテストすることによって水蒸気処理温度の触媒特性及び性能に対する影響を調べた。ゼオライト含有量が約６７質量％のゼオライト含有量を有するか焼された球を調製し、実施例１に示した手順で水蒸気処理した。水蒸気処理は表示されている温度に徐々に上げて行うか（ｒａｍｐと表示）、あるいは触媒をはじめから表示されている温度におく（ｆｌａｔと表示）ことによって行われた。その後、これらの球を触媒の白金含有量が３５０〜４６０質量ｐｐｍとなるように含浸させ、乾燥、酸化、そして還元した。完成した触媒は上に述べたマックベイン水容量テストで測定して、質量％で表示して下表に示すような４．６ｔｏｒｒ水容量を有していた。

【００５６】
実施例９
実施例７の触媒の異性化性能を実施例５で述べた不均衡Ｃ₈芳香族化合物供給原料を処理するパイロット・プラントを用いて比較評価した。この供給原料を圧力１．３ＭＰａ、質量時間空間速度１０ｈｒ^-1、水素／炭化水素モル比４、そして下表に示す温度で異性化した。６５％エチルベンゼン転化率でのテスト結果を下表に示す。

水容量の低下は触媒活性の低下と共に起こり、キシレン・ロスは温度勾配を用いずに一挙に高温で水蒸気処理した場合に低かった。これらの結果を図２にグラフ的に示す。
【００５７】
実施例１０
本発明によるさらに高い水蒸気処理温度を用いてさらに一連の触媒を作成し、上に述べたようなテスト手順でその性能を調べた。約６７質量％のゼオライト含有量を有するか焼された球を調製して、実施例１に示した手順で水蒸気処理した。水蒸気処理は連続したゾーンでそれぞれ約７２５℃及び８５０℃の温度で行われた。触媒Ｏ及びＱはアンモニウム交換をしたものであった。これらの球を触媒の白金含有量が３５０〜４６０質量ｐｐｍの範囲となるように含浸させ、乾燥、酸化、還元した。完成した触媒は上に述べたマックベイン水容量テストで測定して、質量％で示された下表に示すような４．６ｔｏｒｒ水容量を有していた。触媒の異性化性能を実施例４で述べた不均衡Ｃ₈芳香族化合物供給原料を処理するパイロット・プラントを用いて比較評価した。この供給原料を圧力１．３ＭＰａ、質量時間空間速度１０ｈｒ^-1、水素／炭化水素モル比４、そして下表に示す温度で異性化した。テスト結果を下表に示す。

【００５８】
実施例１１
本発明による白金含有触媒を、水蒸気処理された球に塩化テトラアミン白金を用いて含浸させた点を除けば実施例１に述べたのと同じ方法で調製した。完成した触媒は元素ベースで、質量ｐｐｍで表現した場合、以下に示すような白金含有量を有していた。
触媒Ｌ ５４０
触媒Ｍ １１３０
【００５９】
実施例１２
本発明による白金含有触媒の異性化性能を、モル％で以下に示す組成を有する不均衡Ｃ₈芳香族化合物供給原料を処理するパイロット・プラントを用いて比較評価した。

【００６０】
この供給原料を圧力１．３ＭＰａ、質量時間空間速度１０ｈｒ^-1、水素／炭化水素モル比４の条件下で異性化した。反応器温度は１回の通過毎のエチルベンゼンの消失で示した場合一定の範囲の転化レベルを達成するように調節した。エチルベンゼンは種としてベンゼン及びトルエン、そして少量の軽質ガスに転化されたが、少量のキシレン・ロスを伴った。６５％エチルベンゼン転化率でのテスト結果は以下の通りであった。

【００６１】
【発明の効果】
本発明では、従来の方法と比較して好ましい条件でより高いパラ−キシレン収率を示す。
【図面の簡単な説明】
【図１】本発明による触媒と公知の触媒のキシレン・ロスに対する相対的活性及び選択性を示すグラフである。
【図２】触媒水容量に対するキシレン・ロスを示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalytic hydrocarbon conversion process, and more specifically to a process for aromatic compound isomerization.
[0002]
[Prior art]
Para-xylene, meta-xylene, and ortho-xylene xylenes are important intermediates in chemical synthesis with a wide and diverse field of application. When para-xylene is oxidized, it produces terephthalic acid which is used in the production of synthetic textile fibers and resins. Meta-xylene is used in the production of plasticizers, azo dyes, wood preservatives and the like. Ortho-xylene is a raw material for phthalic anhydride products.
[0003]
Xylene isomers from catalytic reforming and other sources generally do not keep up with the proportion of demand as chemical intermediates, and also contain ethylbenzene which is difficult to separate and convert. In particular, para-xylene is a major chemical intermediate whose demand is growing rapidly. ₈ Only about 20-25% of the aromatic stream is included. Adjusting the isomer ratio to meet demand can be accomplished by combining xylene isomer recovery, such as adsorption for para-xylene recovery, with isomerization to produce additional amounts of the desired isomer. Isomerization converts an unbalanced mixture of xylene isomers that are poor in the desired xylene isomer to a near-equilibrium mixture.
[0004]
Various catalysts and processes have been developed to perform xylene isomerization. In selecting an appropriate technique, it is desirable to make the isomerization process as close to equilibrium as possible in order to maximize the yield of para-xylene, but due to side reactions, cyclic C ₈ Compound loss increases. The method used to approximate equilibrium is cyclic C at high conversion (ie, very close to equilibrium). ₈ Compound loss and unconverted C ₈ The aim is to balance the high utility costs generated by the high circulation rate of aromatic compounds.
[0005]
C ₈ Catalysts used to isomerize aromatic compounds are classified by the method of treating ethylbenzene combined with xylene isomers. Ethylbenzene is not easily isomerized to xylene, but is usually converted in the isomerization zone because separation from xylene by superfractionation or desorption is very expensive. One approach is to form xylene by reacting ethylbenzene by conversion from naphthene or by reconversion from it using a hydrogenation-dehydrogenation function in the presence of a solid acid catalyst. Another widely used method is by dealkylating ethylbenzene to form predominantly benzene while simultaneously isomerizing xylene to a near equilibrium mixture. The former method increases xylene yield by forming xylene from ethylbenzene, and the latter method generally increases the ethylbenzene conversion rate, thus reducing the amount of recycle to the para-xylene recovery unit and the associated processing costs. Reduce.
[0006]
In the last 20 years or so, crystalline aluminosilicate zeolite-containing catalysts have become widely used for xylene isomerization. For example, US Pat. No. 3,856,872 teaches xylene isomerization and ethylbenzene conversion using a catalyst containing ZSM-5, -12 or -21 zeolite. U.S. Patent Application No. 4,626,609 discloses the conversion of xylene isomers using a catalyst containing a composite that has been steamed in the range of 200-500 ° C. US Patent Application No. 4,899,012 teaches the use of a catalyst containing lead, a Group VII metal, a pentasil zeolite, and an inorganic oxide binder to isomerize xylene and dealkylate ethylbenzene. ing. Development efforts continue to achieve economically attractive isomerization with a better combination of activity, selectivity, and stability.
[0007]
[Problems to be solved by the invention]
The main object of the present invention is to provide a new isomerization process for alkylaromatic hydrocarbons. More specifically, the present invention provides C for increasing the concentration of desirable xylene isomers. ₈ It relates to the treatment of aromatic compounds.
[0008]
[Means for Solving the Problems]
The present invention is C ₈ Improved aromatic conversion and selectivity to xylene isomerization should be achieved using a zeolite catalyst component having a constant low water capacity in the finished catalyst composition and containing inert silica or aluminum phosphate binder. Is based on the discovery that
[0009]
Thus, one broad embodiment of the present invention is that in the form of an oil-dropped spherical catalyst, a zeolite aluminosilicate having a pore size in the range of 5-8 angstroms, a platinum group metal component, and an inert silica bond. 1 illustrates an alkyl aromatic hydrocarbon isomerization process using a catalyst having an agent or an aluminum phosphate binder. The process includes the step of isomerizing a feedstock composed of an unbalanced mixture of xylene and ethylbenzene under isomerization conditions to obtain a product having an increased para-xylene content relative to the feedstock. It is out. Suitable isomerization conditions are temperatures in the range of about 300-600 ° C., pressures in the range of 100 kPa-5 MPa, and 0.5-100 hr. ^-1 The mass time space velocity is included. Mass hourly space velocity is about 10-50 hr ^-1 A temperature in the range of 350 to 500 ° C. is particularly preferable. MFI type zeolite is the preferred zeolite aluminosilicate. The catalyst has a low 4.6 torr water capacity of less than about 7% by weight, preferably between about 3-5% by weight. The platinum group metal is preferably composed of a low concentration of platinum in the range of 100 to 2000 ppm by weight with respect to the catalyst, with a range of about 200 to 800 ppm by weight being particularly preferred.
[0010]
These and other objects and aspects will become apparent upon reference to the following detailed description of the invention.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The feedstock for aromatic isomerization is where n is an integer and R is CH _Three , C ₂ H _Five , C _Three H ₇ Or C _Four H ₉ As one of the general formulas C ₆ H _(6-n) R _n It contains an isomerizable alkyl aromatic hydrocarbon represented by Suitable alkyl aromatic hydrocarbons include, for example, ortho-xylene, meta-xylene, para-xylene, ethylbenzene, ethyltoluene, trimethylbenzene, propylbenzene, ethylmethyl-benzene, diethylbenzene, methylpropylbenzene, ethylpropylbenzene, trimethyl. Examples include ethylbenzene, di-isopropylbenzene, and mixtures thereof, but the present invention is not limited thereto.
[0012]
C containing ethylbenzene and xylene ₈ Isomerization of aromatic compound mixtures is one of the particularly preferred methods of application of the present invention. Generally such mixtures have an ethylbenzene content of about 5-50% by weight, a meta-xylene content of about 20-95% by weight, and a para-xylene content of about 0-15% by weight. C, the feedstock ₈ Aromatic compounds are composed of an unbalanced mixture, ie at least C ₉ It is desirable for the aromatic isomers to be present at a concentration that is significantly different from the equilibrium concentration under isomerization conditions. Typically, the unbalanced mixture is fresh C obtained from processes for the production and recovery of aromatics from other hydrocarbons such as catalytic reforming and / or extraction. ₈ It is prepared by removing para-xylene or ortho-xylene from an aromatic compound.
[0013]
For example, individual fractions obtained by selective fractionation and distillation of catalytically cracked or reformed hydrocarbons, or as found in appropriate fractions from various refined petroleum streams as constant boiling range fractions. Alkyl aromatic hydrocarbons can be used in the present invention. In the process according to the present invention, an alkyl aromatic hydrocarbon-containing stream, such as a catalytic reforming oil, regardless of whether there is continuous aromatic extraction to produce sufficient xylene isomers, particularly para-xylene. Isomerization can be performed. In this process, C ₈ The aromatic compound feedstock may contain non-aromatic hydrocarbons, that is, naphthene or paraffin within a range of 30% by mass or less. Preferably, however, the isomerizable hydrocarbon is constituted essentially by aromatic compounds so that a pure product is obtained from the downstream recovery process.
[0014]
In the process according to the invention, the alkyl aromatic hydrocarbon feed mixture, preferably in a mixed state with hydrogen, is contacted with a catalyst of the type as described above in the alkyl aromatic hydrocarbon isomerization zone. This contact can be performed using the catalyst in a fixed bed system, moving bed system, fluidized bed system, or batch operation. Considering the loss of valuable catalyst consumption and the risk of simple operation, it is preferable to use a fixed bed system. In this system, the hydrogen rich gas and feed mixture are preheated by suitable heating means to the desired reaction temperature and then fed into an isomerization zone containing a fixed bed of catalyst. The conversion zone may consist of one or more individual reactors with suitable means placed between them to ensure that the desired isomerization temperature is maintained at the entrance of each zone. These reactants can be contacted with the catalyst bed in either up-flow, down-flow, or radiant flow, and when the reactants are contacted with the catalyst, they can be in the liquid phase, liquid / vapor mixed phase, or vapor. Any of the phases may be used.
[0015]
Alkyl aromatic hydrocarbon feedstock mixture, preferably C ₈ The unbalanced mixture of aromatic compounds is contacted with the isomerization catalyst under suitable alkylaromatic hydrocarbon isomerization conditions. Such conditions include temperatures in the range of 100 to 500 ° C or higher, preferably about 350 to 500 ° C. The pressure is generally in the range of about 100 kPa to 10 MPa, and more generally in the range not exceeding about 5 MPa. About 0.5-100 hr for hydrocarbon feedstock mixture ^-1 A sufficient amount of catalyst to enter the isomerization zone to achieve a mass hour space velocity in the range of about 10 hr. ^-1 Good results have been obtained in these cases. The hydrocarbon feed mixture is reacted in a mixture with hydrogen at a hydrogen to hydrocarbon molar ratio of about 0.5: 1 to about 10: 1 and with other inert diluents such as nitrogen, argon, etc. Light hydrocarbons may be present.
[0016]
The specific scheme used to recover the isomerized product from the effluent from the reactor of the isomerization zone should not be considered an integral part of the present invention, and any effective known in the prior art Any recovery method may be used.
[0017]
In the combined separation / isomerization process associated with ethylbenzene / xylene mixture processing, fresh C ₈ Aromatic feedstock is C from the isomerization reaction zone. ₈ Combined with an isomerization product comprising aromatics and naphthalene, it is sent to a para-xylene separation zone from which pure para-xylene is recovered. Para-xylene from the separation zone is depleted and C containing xylene and ethylbenzene ₈ A stream composed of an unbalanced mixture of aromatics is sent to the isomerization reaction zone where C ₈ Aromatic isomers are isomerized to near equilibrium levels to obtain isomerized products. In this process scheme, unrecovered C ₈ The aromatic isomers are preferably recycled until they are converted to para-xylene or are lost by side reactions, i.e. completely eliminated. The separation of ortho-xylene, preferably by fractional distillation, is also fresh C ₈ This can be done with aromatic feedstocks or isomerization products, or a combination of both, but this is preferably done prior to the para-xylene separation.
[0018]
The isomerization catalyst according to the present invention is composed of molecular sieve and refractory inorganic oxide. Preferred molecular sieve is Si: Al ₂ Zeolite aluminosilicate selected from those having a ratio of about 10 or more, preferably 20 or more and a pore size of about 5 to 8 Angstroms. Specific examples of suitable zeolites are MFI, MEL, EUO, FER, MFS, MTT, MTW, TON, MOR and FAU type zeolites. Pentasil zeolite MFI, MEL, MTW, and TON are preferred, with MFI type zeolite often referred to as ZSM-5 being particularly preferred.
[0019]
The relative proportion of zeolite in the catalyst may be about 10 to 99% by mass, preferably in the range of about 20 to 90% by mass. There is a trade-off between the zeolite content of the catalyst composite to keep the xylene loss low in the isomerization operation and the pressure, temperature, and time space velocity.
[0020]
The refractory binder or matrix is used to facilitate the production of the isomerization catalyst. The binder must be uniform in composition and relatively high in fire resistance at the conditions used in the process. Suitable binders include alumina, magnesia, zirconia, chromia, titania, boria, and silica.
[0021]
The first preferred binder is amorphous silica. A preferred amorphous silica is a synthetic, white amorphous silica (silicon dioxide) powder, which is classified as a hydrated silica in the wet process. This type of silica is produced by a chemical reaction in an aqueous solution, from which it is precipitated as very fine spherical particles. Silica has a BET surface area of about 50 to 800 m ² / G, especially 120-160m ² / G is preferable. The content of the sulfate is desirably low, and is preferably 0.3% by mass or less. It is particularly preferred that the amorphous silica binder is non-acidic, for example, the pH of a 5% aqueous suspension is neutral or basic (pH is about 7 or higher).
[0022]
A second preferred binder is amorphous aluminum phosphate. Zeolite and aluminum phosphate binder can be formed into particles by methods well known in the prior art. A preferred method for preparing a zeolite / aluminum phosphate support includes the steps of adding the zeolite to an alumina sol or phosphate compound and an oil drop method as described below for the mixture of alumina sol / zeolite / phosphate compound. And including forming the particles by calcining the spherical particles.
[0023]
A preferred oil drop process for preparing an aluminum phosphate binding catalyst is described in US Pat. No. 4,629,717, incorporated herein by reference. The technique described in the above patent includes the step of gelling an alumina hydrosol containing a phosphate compound using a known oil drop process. Typically, this technique involves preparing a hydrosol by digesting aluminum in an aqueous hydrochloric acid solution at a reflux temperature of about 80-105 ° C. The ratio of aluminum to chloride in the sol ranges from about 0.7: 1 to 1.5: 1 mass ratio. Next, a phosphorus compound is added to the sol. Preferred phosphorus compounds are phosphoric acid, phosphorous acid, and aluminum phosphate. The amounts of phosphorus and aluminum expressed in molar ratios range from about 10: 1 to 1: 100, respectively, on an element basis. Zeolite is then added to the aluminum phosphate hydrosol to gel the mixture. One way to gel this mixture is to combine the gelling agent with the mixture and then heat the resulting combined mixture to a high temperature so that gelling occurs to form oblate spherical particles. Dispersing in an oil tank or tower. Gelling agents that can be used in this process are hexamethylene, urea, or mixtures thereof. The gelling agent releases ammonia at an elevated temperature that solidifies or converts the hydrosol spheres into hydrogel spheres. These spheres are then withdrawn continuously from the oil bath and are usually cured and dried in oil and ammonia solutions to further improve their physical properties. The cured and gelled particles thus produced are washed and dried at a relatively low temperature of about 100 to 150 ° C., and further calcined at a temperature of about 450 to 700 ° C. for about 1 to 20 hours. . The amount of phosphorus-containing alumina component present (as oxide) in the catalyst is about 10 to 70% by weight, preferably about 20 to 50% by weight.
[0024]
This combined mixture is preferably dispersed in the oil tank in the form of droplets from a nozzle, orifice, or rotating disk. These particles can also be formed by spray drying the mixture at a temperature in the range of about 425-760 ° C. In any case, conditions and equipment should be selected to obtain small spherical particles, which are preferably no greater than 1.0 mm, more preferably 0.2-0.8 mm, and most preferably about 0.3. It has an average diameter of ˜0.8 mm.
[0025]
The crystallinity of the aluminum phosphate binder can be adjusted by changing the proportion of the phosphate component. Substances that are not in the amorphous phase usually exist as gamma-alumina, and as the phosphorus content increases, the crystallinity increases accordingly. The apparent bulk density also changes depending on the phosphorus content, and the average bulk density decreases as the phosphorus ratio increases. The surface area is also controlled by the phosphorus content, and gamma-alumina oil drop spherical particles usually have a maximum of about 250 m. ² / G, while the surface area of the flat spherical particles of aluminum phosphate is 450 m at the maximum. ² / G. The Al / P ratio of the binder / matrix is generally in the range of about 1/10 to 100/1, more typically in the range of about 1/5 to 20/1.
[0026]
Another shape of the catalyst composite is an extrudate. The extrusion preferably includes a silica binder. A known extrusion method produces an extrudate that has acceptable integrity either by mixing the molecular sieve with a binder and a suitable peptizing agent either before or after mixing the metal components and by direct calcination. Forming a homogeneous dough or thick paste with the correct moisture as it is formed. Extrusion moldability is determined by analyzing the moisture content of the dough, and a moisture content of 30 to 50% by mass is preferred. A variety of different extruded shapes are possible, such as cylindrical, trefoil, dumbbell, left-right symmetric, or left-right asymmetric multi-leaf.
[0027]
The catalyst according to the invention can contain a halogen component. The halogen component can be any of fluorine, chlorine, bromine, iodine, or mixtures thereof, with chlorine being preferred. The halogen component is generally present in a bound state with the inorganic oxide support. The optional halogen component is preferably well dispersed throughout the catalyst and may be included on an elemental basis in an amount from 0.2% to about 15% by weight of the final catalyst. However, it is preferred that the catalyst does not contain halogens other than those combined with other catalyst components.
[0028]
The formed catalyst composite is dried at a temperature of about 100-320 ° C. for about 2-24 hours or more, usually converting the metal components present sufficiently to the oxide form. Until about 0.1 to 10 hours at a temperature in the range of about 400 to 650 ° C.
[0029]
This catalyst composite is subjected to steam treatment in order to adjust its acidic activity. This steam treatment is performed on the zeolite and binder composite prior to incorporating the platinum group metal. Steam treatment conditions include a water concentration of about 5 to 100% by volume, a pressure in the range of about 100 kPa to 2 MPa, and a temperature of about 600 to 1200 ° C., and the steam treatment temperature is at least about 650 ° C., more preferably at least About 750 ° C., and most preferably 775 ° C. or higher. In some examples, temperatures of about 800-850 ° C. or higher are employed. This steam treatment should be carried out over at least 1 hour, preferably over 6 to 48 hours.
[0030]
Apart from or in addition to steaming, the composite can be washed one or more times with ammonium nitrate solution, mineral acid, and / or water. In the first mode, the catalyst is washed with about 5-30% by weight ammonium nitrate. If acid cleaning is used, HCl or HNO _Three Mineral acids such as are preferred, and a sufficient amount of acid is added to maintain the pH in the range of 1 to about 6, preferably 1.5-4. The catalyst is maintained on a bed in which solution and / or water is circulated for a period of about 0.5 to 48 hours, preferably 1 to 24 hours. This washing can be performed at any stage of preparation, and a method of washing in two stages may be selected.
[0031]
Prior to adding the platinum group metal component, the composite is preferably NH. _Four Alternatively, it is ion exchanged with a base solution containing at least one hydrogen-forming cation such as tetravalent ammonium. This hydrogen-forming cation is primarily substituted for the alkali metal cation to provide a hydrogen form zeolite component after calcination.
[0032]
A platinum group metal containing one or more of platinum, palladium, rhodium, ruthenium, osmium, and iridium is an essential component of the catalyst according to the present invention. Preferred platinum group metals are platinum and palladium, with platinum being particularly preferred. The platinum group metal is present in the final catalyst as an oxide, halogen compound, sulfide, oxysulfide, or other elemental metal or in combination with one or more other components of the catalyst composite. It may be. It is believed that best results are obtained when almost all of the platinum group metal component is present in the reduced state. The platinum group metal component is usually included on an elemental basis in a proportion of about 100 to 5000 ppm by weight (parts per million) of the final catalyst composite, and a level of about 100 to 2000 ppm by weight is particularly suitable. When using a platinum component, it is preferred that a very low proportion of platinum, in the proportion of about 200 to 800 ppm by mass, is present in the catalyst on an element basis, a level of about 600 ppm by mass or less is particularly preferred, and about 300 to A level of 500 ppm by mass gives very good results. When a palladium component is used, it is preferred that palladium is present in the catalyst in a proportion of about 400-2000 ppm by mass, with a level of about 500-1200 ppm by mass being particularly preferred.
[0033]
The platinum group metal component can be incorporated into the catalyst composite by any suitable method. One method of preparing this catalyst is to impregnate a calcined sieve / binder composite with a water-soluble, degradable metal of a platinum group metal. Further, a platinum group metal may be added at the time of combining the sieving component and the binder. Yet another way to achieve proper metal distribution is by combining the metal component with the binder before extruding the sieve and binder together. Platinum group metal complexes mentioned above or that can be used by other known methods include chloroplatinic acid, chloropalladium acid, platinum ammonium chloride, bromoplatinic acid, platinum trichloride, platinum tetrachloride hydrate, Examples thereof include platinum dichlorocarbonyl dichloride, tetraamine platinum chloride, dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladium chloride, palladium nitrate, diamine palladium hydroxide (II), and tetraamine palladium (II) chloride. It is within the scope of this invention that the catalyst contains other metal components known to modify platinum group metal components.
[0034]
After adding the metal component, the resulting catalyst composite is typically dried at a temperature of about 100-320 ° C. for a period of about 1-24 hours or longer. The dried composite is then calcined in air at a temperature of about 400-600 ° C. for about 0.1-10 hours to convert the metal component to essentially the oxide form.
[0035]
The calcined composite is optionally subjected to a substantially moisture-free reduction step to ensure that any metal components are evenly divided and dispersed. The reduction can optionally be carried out with a catalyst which has been put into the isomerization process according to the invention prior to the start of the isomerization process. Substantially pure and dry (ie, 20 ppm by volume or less H ₂ O) Hydrogen is used as the reducing agent in this step. The reducing agent contacts the catalyst under conditions effective to reduce almost all of the Group VIII metal to a metallic state, including a temperature of about 200-650 ° C. and a period of about 0.5-10 hours. In some instances, the resulting reduced catalyst composite is known in the prior art to incorporate about 0.01 to 0.05 weight percent sulfur on an element basis in the catalyst composite. It is also preferred to presulfide using the method.
[0036]
The finished catalyst has a McBain water capacity in the range of about 2-7 wt%, preferably about 3.0-5.0 wt%, and most preferably about 3.5-4.5 wt% at 4.6 torr. Have. The water capacity can be measured by the following procedure.
[0037]
Activation step:
The empty pail reading (W1) is read, after which the catalyst is activated overnight under vacuum at a temperature of 375 ° C. to 400 ° C. for about 16 hours. The degree of vacuum of this system is 1 millitorr or less. The catalyst is cooled to room temperature and the McBain tube containing the activated catalyst is closed, after which the reading of the activated catalyst at room temperature (W2) is read. The ice bath is then collected around a water reservoir to maintain the water at 0 ° C. during the adsorption step.
[0038]
Adsorption step:
Open the water reservoir to drain water from the manifold and allow the mercury U-type nanometer to read a pressure of 4.6 torr. Open the tube and record the adsorption start time. The catalyst is allowed to equilibrate for at least 1.5 hours and the final time is recorded before reading the water vapor balanced catalyst reading (W3). The water capacity is calculated as follows:
Capacity, mass% = [(W2-W3)] / (W1-W2)] × 100
[0039]
Slow deposition of coke and other non-activated deposits on the catalyst during the operation of the isomerization process will ultimately reduce the activity and selectivity of the process to the desired level for regeneration. If the performance of the catalyst has deteriorated to the extent that regeneration is desired, the introduction of hydrogen feed into the conversion zone containing the catalyst is stopped and the conversion zone is purged with a suitable gas stream. Regeneration to restore the activity and selectivity of the catalyst may be performed on site, or the catalyst may be removed to an off-line facility and regenerated there.
[0040]
【Example】
Example 1
An aluminum phosphate linked MFI was prepared to illustrate the transalkylation process according to the present invention. A first solution was prepared by adding a sufficient amount of phosphoric acid such that the phosphorus content of the finished catalyst was equal to about 11% by weight to a sufficient amount of hexamethylenetetraamine (HMT) solution. Sufficient amount of alumina prepared by digesting metallic aluminum in hydrochloric acid with ammonia-exchanged MFI type zeolite having a Si / Al ratio of about 39 so that the zeolite component in the finished catalyst is about 67% by mass A second solution was prepared in addition to the sol. These two solutions were combined to create a homogeneous mixture of HMT, phosphorus, alumina, and zeolite. This mixture was dispersed as droplets in an oil bath maintained at a temperature of about 93 ° C. The droplets remained in the oil bath until they solidified to form hydrosol spheres with a diameter of about 1.6 mm. The balls were removed from the oil bath, washed with water, air dried and then calcined at a temperature of about 550 ° C. The calcined spheres were steamed for 12 hours at a temperature of about 660 ° C. in air containing 40% steam at 1 atmosphere.
[0041]
The steam-treated spheres were then metal impregnated using a tetraamine platinum chloride solution. When impregnation was completed, the catalyst was dried, oxidized, and further reduced to prepare a catalyst having a platinum concentration of about 460 ppm by mass. The isomerization catalyst used to describe the process according to the invention was named Catalyst A.
[0042]
Example 2
A silica-bound MFI catalyst was prepared to illustrate the transalkylation process according to the present invention. Si / Al ₂ Ammonia exchanged MFI type zeolite with a ratio of about 38 was mixed with Methocel in a grinder. A hydrated amorphous silica powder, Ludox AS-40, was added to the MFI catalyst at a ratio of about 67% by weight. This mixture was thoroughly blended in a grinder with sufficient amount of pure water to produce an extrudable dough having a water content of about 40% by weight. This dough was then extruded through a cylindrical mold to form a cylindrical extrudate with a diameter of about 1.6 mm. Next, the extruded product was washed with water, air-dried, fired at a temperature of about 550 ° C., and steam-treated at a temperature of about 660 ° C. for 12 hours in air containing 40% water vapor.
[0043]
The steam-treated extrudate was column washed with ammonium nitrate at a temperature of 88 ° C. for 5 hours, then cleaned with deionized water and dried at a temperature of 510 ° C. for about 9 hours. The dried extrudate was impregnated with metal by rotating in a chloroplatinic acid solution at a temperature of 60 to 100 ° C. for 6 to 7 hours. When impregnation was completed, the composite was dried, oxidized and reduced to produce a catalyst containing about 460 mass ppm platinum. This isomerization catalyst used for explaining the method of the present invention was designated as catalyst A ′.
[0044]
Example 3
To compare the isomerization results with Catalyst A, an alumina-bound catalyst was prepared. Prepare a first solution of aluminum nitrate and add it to NH _Four A second solution of OH was added. The second solution was slowly added to maintain pH 8 until aluminum gelation occurred. The alumina hydrosol was slurried with water and filtered to produce a filter cake having a moisture content of about 90% by weight. A portion of this filter cake was dried at a temperature of 150 ° C. to a moisture content of about 60% by weight. The dried material was pulverized to produce powdered alumina.
[0045]
About 67% by weight MFI zeolite was combined with hydrosol alumina and powdered alumina and mixed to produce an extrudable dough. Thereafter, the dough was extruded to form a cylindrical extruded product. These extrudates were directly calcined at a temperature of about 600 ° C. in flowing air.
[0046]
The calcined extrudate was subjected to an impregnation procedure using a solution of tetraamine platinum chloride. Thereafter, the catalyst was dried, oxidized and reduced to prepare a catalyst containing platinum at a concentration of about 400 ppm by mass. This reference catalyst was designated as Catalyst X.
[0047]
Example 4
A second control catalyst was made for comparison with the catalyst according to the present invention. This catalyst was basically composed of approximately 11% by weight of hydrogen form ZSM-5 zeolite and 0.29% by weight of platinum with the remainder being alumina binder. MFI zeolite was added to an alumina sol solution that had been calcined by digesting metallic aluminum in hydrochloric acid in an amount sufficient to produce an alumina content of about 11% by weight in the final catalyst. A second solution of hexamethylenetetramine (HMT) was prepared and added to the zeolite / alumina sol to obtain a homogeneous mixture. This mixture was then added as droplets to an oil bath maintained at a temperature of about 93 ° C. These oil droplets solidified and maintained in the oil bath until formed hydrosol spheres were formed. These spheres were removed from the oil bath, washed with 0.5% ammonia / water solution, air dried and calcined at a temperature of about 650 ° C. These calcined spheres are chlorplatinic acid solution, Pb (NO _Three ) ₂ Was co-impregnated with lead and hydrochloric acid to form a finished catalyst containing about 0.2 wt% platinum and 0.8 wt% lead. The impregnated spheres are oxidized and H at a temperature of 565 ° C. ₂ Put under reducing atmosphere, H ₂ Sulfurized with S. This catalyst known from the prior art was designated catalyst Y.
[0048]
Example 5
The isomerization performance of the catalyst according to the present invention and the isomerization performance of the control catalyst in mol% with the following composition: ₈ A comparative evaluation was conducted using a pilot plant for treating aromatic raw materials.

[0049]
This feedstock was pressured at 1.3 MPa, 10 hr ^-1 Was isomerized under the following conditions: mass hour space velocity, and hydrogen / hydrocarbon molar ratio of 4. Each pass through the reactor temperature was adjusted to the conversion level range indicated by the disappearance of ethylbenzene. Ethylbenzene was converted mainly to benzene and toluene with a small amount of xylene loss, and a small amount of light gas was also observed. The test results comparing valuable xylene loss at an ethylbenzene conversion of 65% are summarized below.

[0050]
Catalyst A used in the present invention showed lower xylene loss under any isomerization conditions compared to catalysts known in the prior art. The catalyst A 'used in the present invention has exceptional activity as indicated by the low temperatures required to achieve about 65% ethylbenzene conversion and low xylene loss compared to prior art catalysts. And showed. The relative performance of catalysts A, X and Y, expressed in xylene loss and activity as a function of conversion, is shown in FIG.
[0051]
Example 6
To compare the effect of platinum group metal concentration on performance in the isomerization process, a series of catalysts according to the present invention were prepared. A calcined sphere having a zeolite content of about 67% by weight was prepared according to the procedure described in Example 1 and steamed. Thereafter, these spheres were impregnated with a tetraamine platinum chloride solution, dried, oxidized and reduced. The names of these spheres and their platinum content are shown in the table below as mass ppm.

[0052]
Example 7
The isomerization performance of the catalysts according to the invention with different platinum contents in terms of mol%, with the following composition: ₈ A comparative evaluation was conducted using a pilot plant for processing aromatics feedstocks.

[0053]
This feedstock is pressure 1.3 MPa, mass hour space velocity 10 hr ^-1 And isomerization under reaction conditions with a hydrogen / hydrocarbon molar ratio of 4. The para-xylene / xylene ratio reached about 23.9%. The reaction temperature was adjusted to produce a range of conversion levels indicated by the disappearance of ethylbenzene per pass. The results of these tests for valuable xylene loss at 65% ethylbenzene conversion are shown in the table below.

[0054]
The xylene loss was lowest when the platinum content was 400 ppm by mass or less.
The catalytic activity showed more preferable results when the platinum content was about 400 ppm by mass or more.
[0055]
Example 8
The effect of steaming temperature on catalyst properties and performance was investigated by preparing and testing a series of catalysts. A calcined sphere having a zeolite content of about 67% by weight was prepared and steamed according to the procedure shown in Example 1. The steam treatment was carried out by gradually raising the temperature to the indicated temperature (indicated as ramp) or by placing the catalyst at the indicated temperature from the beginning (indicated as flat). Thereafter, these spheres were impregnated so that the platinum content of the catalyst was 350 to 460 ppm by mass, dried, oxidized, and reduced. The finished catalyst had a 4.6 torr water capacity as measured by the MacBain water capacity test described above and expressed in mass% as shown in the table below.

[0056]
Example 9
The isomerization performance of the catalyst of Example 7 is shown in the imbalance C described in Example 5. ₈ A comparative evaluation was conducted using a pilot plant for processing aromatics feedstocks. This feedstock is pressure 1.3 MPa, mass hour space velocity 10 hr ^-1 Isomerization at a hydrogen / hydrocarbon molar ratio of 4 and the temperatures shown in the table below. The test results at 65% ethylbenzene conversion are shown in the table below.

The decrease in water capacity occurred with a decrease in catalyst activity, and the xylene loss was low when steaming at a high temperature all at once without using a temperature gradient. These results are shown graphically in FIG.
[0057]
Example 10
A further series of catalysts was made using the higher steam treatment temperature according to the present invention and its performance was examined in the test procedure as described above. A calcined sphere having a zeolite content of about 67% by weight was prepared and steamed according to the procedure shown in Example 1. The steam treatment was performed in continuous zones at temperatures of about 725 ° C. and 850 ° C., respectively. Catalysts O and Q were ammonium exchanged. These spheres were impregnated so that the platinum content of the catalyst was in the range of 350 to 460 mass ppm, dried, oxidized and reduced. The finished catalyst had a 4.6 torr water capacity as shown in the table below, expressed in mass%, as measured by the McBain water capacity test described above. The isomerization performance of the catalyst is shown in Example 4 ₈ A comparative evaluation was conducted using a pilot plant for processing aromatics feedstocks. This feedstock is pressure 1.3 MPa, mass hour space velocity 10 hr ^-1 Isomerization at a hydrogen / hydrocarbon molar ratio of 4 and the temperatures shown in the table below. The test results are shown in the table below.

[0058]
Example 11
A platinum-containing catalyst according to the present invention was prepared in the same manner as described in Example 1 except that steam-treated spheres were impregnated with tetraamineplatinum chloride. The completed catalyst was element-based and had a platinum content as shown below when expressed in ppm by mass.
Catalyst L 540
Catalyst M 1130
[0059]
Example 12
The isomerization performance of the platinum-containing catalyst according to the invention is shown in imbalance C having the following composition in mol%: ₈ A comparative evaluation was conducted using a pilot plant for processing aromatics feedstocks.

[0060]
This feedstock is pressure 1.3 MPa, mass hour space velocity 10 hr ^-1 The isomerization was carried out under a hydrogen / hydrocarbon molar ratio of 4. The reactor temperature was adjusted to achieve a range of conversion levels as indicated by the disappearance of ethylbenzene per pass. Ethylbenzene was converted to benzene and toluene as seeds and a small amount of light gas, but with a small amount of xylene loss. The test results at 65% ethylbenzene conversion were as follows.

[0061]
【The invention's effect】
In the present invention, a higher para-xylene yield is exhibited under favorable conditions as compared with the conventional method.
[Brief description of the drawings]
FIG. 1 is a graph showing the relative activity and selectivity of a catalyst according to the present invention and a known catalyst against xylene loss.
FIG. 2 is a graph showing xylene loss versus catalyst water capacity.

Claims (6)

In a process for isomerizing an unbalanced feedstock mixture of xylene and ethylbenzene, the feedstock mixture comprises a zeolite aluminosilicate having a pore size ranging from 5 to 8 angstroms, a platinum group metal component, and amorphous aluminum phosphate. In an isomerization zone in which hydrogen is present in a catalyst having an oil-dropped spherical shape containing a binder, the catalyst having a water capacity of 4.6 torr of 3 to 5% by mass, and 300 to 600 ° C. Isomerization in which at least one xylene isomer is contained in a higher proportion in the feed mixture under isomerization conditions including a temperature of 100 kPa to 5 MPa, a pressure in the range of 100 kPa to 5 MPa, and a mass hour space velocity of 0.5 to 100 hr ^−1. Comprising contacting to obtain a fluorinated product.   The process of claim 1 wherein the xylene isomer is para-xylene. The process according to claim 1, wherein the isomerization conditions comprise a range of 350 to 500 ° C, an absolute pressure in the range of 100 kPa to 5 MPa, and a mass hour space velocity of 2 to 50 hr- ¹ .   The method of claim 1, wherein the zeolite aluminosilicate comprises a pentasil zeolite selected from the group consisting of MFI, MEL, MTW, and TON.   The method of claim 1, wherein the platinum group metal component comprises 200 to 800 ppm by weight of platinum on an element basis. Isomerized product and fresh C ₈ ortho from one or both of the aromatic feedstock - The method of claim 1, further comprising the step of recovering the xylenes.

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