Ethylbenzene zeolite catalyst processes

Alkylation. Ethylbenzene [100-41-4], the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either in the liquid phase in the presence of a Friedel-Crafts catalyst (A1C13, BF3, FeCl3) or in the vapor phase with a suitable catalyst. The Monsanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeolite catalyst process for liquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process using zeolite catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-3], which is obtained by dehydrogenation in the presence of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

EBMax A continuous, liquid-phase process for making ethylbenzene from ethylene and benzene, using a zeolite catalyst. Developed by Raytheon Engineers and Constructors and Mobil Oil Corporation and first installed at Chiba Styrene Monomer in Japan in 1995. Generally similar to the Mobil/Badger process, but the improved catalyst permits the reactor size to be reduced by two thirds. 

Since zeolite catalysts are successfully introduced in the refining and petrochemical industries, it is not surprising that most of the recent advances concern incremental improvements of existing processes with the development of new generations of catalysts (e.g., dewaxing, ethylbenzene and cumene synthesis). The number of newer applications is much more limited, for example, direct synthesis of phenol from benzene and aromatization of short-chain alkanes, etc. However, both the improvement and development of processes contribute significantly to environmental advances. 

In recent years alkylations have been accomplished with acidic zeolite catalysts, most nobably ZSM-5. A ZSM-5 ethylbenzene process was commercialized jointly by Mobil Co. and Badger America in 1976 (24). The vapor-phase reaction occurs at temperatures above 370°C over a fixed bed of catalyst at 1.4—2.8 MPa (200—400 psi) with high ethylene space velocities. A typical molar ethylene to benzene ratio is about 1—1.2. The conversion to ethylbenzene is quantitative. The principal advantages of zeolite-based routes are easy recovery of products, elimination of corrosive or environmentally unacceptable by-products, high product yields and selectivities, and high process heat recovery (25,26). 

ABB Lummus Crest Inc. and Unocal Corp. have licensed a benzene alkylation process using a proprietary zeolite catalyst. Unlike the Mobil-Badger process, the Unocal-Lummus process is suitable for either ethylbenzene or cumene manufacture (27,28). 

Zeolite-Based Alkylation. Zeolites have the advantage of being noncot-rosive and environmentally benign. The Mobil-Badger vapor-phase ethylbenzene process was ihe lirsl zeolite-based process to achieve commercial success. It is based on a synthetic zeolite catalyst. ZSM-5. and has the desirable characteristics of high activity, low oligomerization, and low coke formation. See also Molecular Sieves. 

The enhanced diffusivity of polynuclear compounds in sc C02 has been utilized to enhance catalyst lifetimes in both 1-butene/isoparaffin alkylations (Clark and Subramaniam, 1998 Gao et al., 1996). The former may be catalyzed using a number of solid acid catalysts (zeolites, sulfated zeolites, etc.), and the use of sc C02 as a solvent/diluent permits the alkylations to be carried out at relatively mild temperatures, leading to the increased production of valuable trimethylpentanes (which are used as high-octane gasoline blending components). The enhancement of product selectivity in the latter process is believed to result from rapid diffusion of ethylbenzene product away from the Y-type zeolite catalysts, thus preventing product isomerization to xylenes. 

Over 90 percent of all ethylbenzene is produced by alkylation of benzene with ethylene in the presence of an acidic catalyst such as aluminum chloride or an acidic zeolite. Figure 10.13 shows a liquid phase alkylation process with zeolite catalyst. 

Styrene. Styrene is the largest benzene derivative with annual consumption about 11.5 billion lb in the United States. It is produced mainly by catalytic dehydrogenation of high-purity ethylbenzene (EB) in the vapor phase. The manufacture process for EB is based on ethylene alkylation with excess benzene. This can be done in a homogeneous system with aluminum chloride catalyst or a heterogeneous solid acid catalyst in either gas or liquid-phase reaction. In the past decade, the liquid-phase alkylation with zeolite catalyst has won acceptance. Those processes have advantages of easier product separation, reducing waste stream, and less corrosion. In addition, it produces less xylene due to lower... 

Friedel-Crafts alkylation of benzene was first commercialized for ethylbenzene and cumene in the 1940s. Aluminum chloride is the Friedel-Crafts catalyst, and the process is operated in the liquid phase. Several alternatives to aluminum chloride technology were developed later, but zeolitic catalysts are a rather recent introduction. UOP began using zeolitic catalysts in the 1990s. 

The feed to an aromatics complex is normally a C6+ aromatic naphtha from a catalytic reformer. The feed is split into Cg+ for xylene recovery and C7 for solvent extraction. The extraction unit recovers pure benzene as a product and C7+ aromatics for recycling. A by-product of extraction is a non-aromatic C6+ raffinate stream. The complex contains a catalytic process for disproportionation and transalkylation of toluene and C9+ aromatics, and a catalytic process for isomerization of C8 aromatics. Zeolitic catalysts are used in these processes, and catalyst selectivity is a major performance factor for minimizing ring loss and formation of light and heavy ends. The choice of isomerization catalyst is dependent on whether it is desired to isomerize ethylbenzene plus xylenes to equilibrium or to dealkylate ethylbenzene to benzene while isomerizing the xylenes. Para-selectivity may also be a desired... 

EBMax is a liquid phase ethylbenzene process that uses Mobil s proprietary MCM-22 zeolite as the catalyst. This process was first commercialized at the Chiba Styrene Monomer Co. in Chiba, Japan in 1995 (16-18). The MCM-22-based catalyst is very stable. Cycle lengths in excess of three years have been achieved commercially. The MCM-22 zeolite catalyst is more monoalkylate selective than large pore zeolites including zeolites beta and Y. This allows the process to use low feed ratios of benzene to ethylene. Typical benzene to ethylene ratios are in the range of 3 to 5. The lower benzene to ethylene ratios reduce the benzene circulation rate which, in turn, improves the efficiency and reduces the throughput of the benzene recovery column. Because the process operates with a reduced benzene circulation rate, plant capacity can be improved without adding distillation capacity. This is an important consideration, since distillation column capacity is a bottleneck in most ethylbenzene process units. The EBMax process operates at low temperatures, and therefore the level of xylenes in the ethylbenzene product is very low, typically less than 10 ppm. 

The approximately 40% of the world s ethylbenzene capacity that still uses A1C13 is testimony to the efficiency and economy of this process. To capture this segment of the industry, zeolite catalysts that operate at close to the same very low benzene to ethylene ratios that make the A1C13 process economically attractive will have to be developed. Heat management in fixed bed reactors becomes a design concern at the low benzene to ethylene ratios that characterize the A1C13 process. Hence, process and catalyst innovations will have to evolve concurrently to achieve the goal of low benzene to ethylene ratios. 

Current zeolite catalysts already operate at process temperatures that require minimal external heat addition. Heat integration and heat management will be of increasing concern at the lower benzene to propylene ratios because the cumene synthesis reaction is highly exothermic (AHf= -98 kJ/mole). Recycle, particularly in the alkylation reactor, is likely to become increasingly important as a heat management strategy. The key will be how to limit the build-up of byproducts and feed impurities in these recycle loops, particularly as manufacturers seek cheaper and consequently lower quality feedstocks. As in the case of ethylbenzene, process and catalyst innovations will have to develop concurrently. 

Application State-of-the-art technology to produce high-purity ethylbenzene (EB) by liquid-phase alkylation of benzene with ethylene. The Lum-mus/UOP EBOne process uses specially formulated, proprietary zeolite catalyst from UOP. The process can handle a wide range of ethylene feed compositions ranging from chemical (70%) to polymer grade (100%). 

Mobil/Badger Ethylbenzene Benzene, polymer-grade ethylene EBMax process uses proprietary Mobil MCM-22 zeolite catalyst low capital cost 10 2000... 

Besides the production of cumene and ethylbenzene, there are a number of recent reports on the production of linear alkylbenzene, precursors to detergents, via the alkylation of benzene with C6-C18 olefins. One process uses suspension CD and essentially 100% conversion of olefin at low temperatures of 90-100°C was obtained. An HF-treated mordenite used in the alkylation of benzene and C10-C14 olefins was foimd to give a 74-84% selectivity to linear alkylbenzene containing 80% 2-phenyl isomer. A new patent on the alkylation of aromatic hydrocarbons such as benzene and cumene with straight-chain C6-C20 olefins on acidic catalyst such as zeolites or fluorine-treated zeolite catalyst packed in a Katamax-type packing was granted. A patent application on the manufacture of xylenes from reformate by RD also appeared and higher than equilibrium amounts of para-xylene were claimed. 

Styrene (SM) can be synthesized in a single step via alkylation of toluene with methanol which offers significant advantages in raw material costs and energy consumption as compared to the benzene to styrene via ethylbenzene process. This single-step process is carried out at a temperature of 400°C and uses a cesium-boron type X zeolite catalyst. The reaction is [31] ... 

Borosilicate catalysts provide high approach to thermodynamic equilibrium of the xylenes, and offer high selectivity in the conversion of ethylbenzene (8.12.22.50 ). In addition, they have been shown to be less prone to the effects of thermal and steam treatments than corresponding aluminosilicate zeolite catalysts (51). The catalytic activity of borosilicate catalysts was demonstrated to be a function of the structural boron content of the molecular sieve (22.36,50). In addition, the by-product distribution obtained from a borosilicate catalyst in a xylene isomerization/ethylbenzene conversion process was found to be distinctive (50), with high transethylation reactivity relative to transmethylation. 

Badger Licensing LLC Ethylbenzene Benzene, ethylene (chemical-grade or polymer- grade) EBMax process uses proprietary ExxonMobil zeolite catalysts high yields and product purity, low capital cost 32 2010... 

Two catalysts have emerged as commercially viable. The Mobil—Badger ethylbenzene process, which has been in commercial use since 1980, employs a zeolite catalyst and operates in the gas phase. A liquid-phase ethylbenzene process joindy licensed by Lummus and UOP uses a Y-type Zeolite catalyst developed by Unocal. This liquid-phase process was commercialized in 1990. The same Y-type ZeoUte catalyst used for the production of ethylbenzene is being offered for the production of cumene but has not yet been commercialized. 

Examples of commercial processes that use zeolitic catalysts for the alkylation of aromatics include the Mobil-Badger ethylbenzene process and the... 

Cg products coming from the reformer can be directly processed in a xylene isomerization unit, using a Pt ZSM-5 zeolite catalyst, and operating at high temperature. Under these conditions, the aliphatics are cracked to lighter products, and the ethylbenzene is hydrodealkylated to benzene and ethane (170,199). 

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