Cyclar catalyst

Ben Taarit and Bandiera (138), have proposed that in monofunctional zeolite catalysts both cracking and dehydrogenation occur on the same type of sites being the attack of the proton the controlling step. The selectivity to these two reactions could be changed by changing the acidity of the sites, opening a possibility to improve the selectivity of a cyclar catalyst. 

Other reactions that occur over the Cyclar catalyst are isomerization, dealkylation, and transalkylation of the aromatics species formed in the main reaction mechanism. The transalkylation reactions result in a distribution of benzene and alkylbenzenes that depends on the charge stock and process conditions. Slightly more benzene is produced from propane than from butane-rich feedstocks. ... 

C and 5 kg/cm pressure (see Molecularsieves). Selectivity for toluene and xylenes peaks at 550°C but continues with increasing temperature for hensene. The Cyclar process (Fig. 6) developed joindy by BP and UOP uses a spherical, proprietary seoHte catalyst with a nonnoble metallic promoter to convert C or C paraffins to aromatics. The drawback to the process economics is the production of fuel gas, alow value by-product. BP operated a... 

A completely new approach for BTX production has emerged in recent years. It converts to paraffins into aromatics using a modified ZSM-5 zeoHte catalyst which contains gallium (19). An example of this approach, the Cyclar process, has been in commercial operation by British Petroleum at Grangemouth, Scotiand since August 1990 (20). It uses C —feed and employs UOP s CCR technology to compensate for rapid catalyst coking. 

The aromatization of liquefied petroleum gases (LPG) has been investigated for more than a decade due to its economical and strategic importance for the exploitation of natural gas reserves and valorization of light hydrocarbons obtained from petroleum refining. Commercially, these reactions using gallium modified ZSM-5 zeolite catalysts are known as Cyclar process, developed jointly by UOP and BP [1]. 

Zeolite catalysts play a vital role in modern industrial catalysis. The varied acidity and microporosity properties of this class of inorganic oxides allow them to be applied to a wide variety of commercially important industrial processes. The acid sites of zeolites and other acidic molecular sieves are easier to manipulate than those of other solid acid catalysts by controlling material properties, such as the framework Si/Al ratio or level of cation exchange. The uniform pore size of the crystalline framework provides a consistent environment that improves the selectivity of the acid-catalyzed transformations that form C-C bonds. The zeoHte structure can also inhibit the formation of heavy coke molecules (such as medium-pore MFl in the Cyclar process or MTG process) or the desorption of undesired large by-products (such as small-pore SAPO-34 in MTO). While faujasite, morden-ite, beta and MFl remain the most widely used zeolite structures for industrial applications, the past decade has seen new structures, such as SAPO-34 and MWW, provide improved performance in specific applications. It is clear that the continued search for more active, selective and stable catalysts for industrially important chemical reactions will include the synthesis and application of new zeolite materials. 

One Interesting and industrially important process developed recently,"the cyclar process" is the catalytic aromatization of light (C3-C5) hydrocarbons over pentasil based catalysts. These new classes of solids have been widely studied (1-9). These Investigations led to the conclusion that the catalysts consisting of gallium, zinc, Pt, and modified H-ZSM-5 were more active and more selective towards aromatics than the parent H-ZSM-5 zeolite. The formation of aromatics from light alkanes comprised several main hydrocarbon reactions alkane... 

Dehydrocyclodimerization of liquefied petrol gas (propane and butane) can be performed to yield BTX-aromatics (Table2, entry 21). Modified ZSM-5 based catalysts are used, for example in the UOP cyclar process [33], and the process will become attractive for extraction of aromatics from natural gas fields containing further C3-C4 fractions. 

The Cyclar process converts C3 and G paraffins to aromatics via a bifunctional zeolitic catalyst (25). Typical aromatic yields in Table 3.11 are 70 wt-%, with 6 wt-% hydrogen yields. The light hydrocarbon products can be used as fuel for the plant. Cyclar can be considered for remote locations as an alternative to flaring LPG, or when refrigerating LPG for shipment is not economical. 

Gallium loaded ZSM-5 is the catalyst used in the Cyclar process (UOP/BP) whereby LPG (largely propane and butane) is converted to high-octane fuels and benzene/toluene/xylene (BTX) as petrochemicals. 

This catalyst regeneration operation is performed using published processes, examples of which include the use of a fixed bed switching reactor system in the case of the Z-Forming process(l), and the use of a continuous catalyst regeneration system in the case of the Cyclar process(2). However, catalyst activity gradually decreases due to the repeated reaction and regeneration. Catalyst life, therefore, is considered terminated at the point where its activity falls below the point at which it is able to maintain a pre-set aromatic yield. 

The catalyst of choice remains acidic Ga-HZSM-5. The BP/UOP Cyclar process [115] used this catalyst in the 1000 bpd plant at Grangemouth, Scotland, which operated for about two years and was shut down in December 1991. With butane as feed a typical product pectrum was 65% BTX, 5% hydrogen and 30% fuel gas. UOPs continuous catalyst... 

ZSM-5 zeolites have been widely used in selective conversion of hydrocarbons through various modification methods. It is well known that Zn- or Ga-containing ZSM-5 zeolites are excellent catalysts for C2-C4 paraffin aromatization called as Cyclar process. Moreover, light olefins of C2""-C4 can be produced from saturated hydrocarbons on modified ZSM-5 zeolite catalysts [1]. Lately a catalyst for CH4 aromatization, that can be regarded as an extension of the Cyclar process, has been derived from ZSM-5 zeolite modified with Mo(VI) species [2-3], In this presentation, the aromatization of CH4 and C2H6 over Mo(VI)/HZSM-5 and W( VI) /HZSM- 5 zeolite catalysts and their mechanistic features are investigated. 

Then cyclization and further II-transfer reactions follow. With propane as feed a typical product spectrum over Ga-H-ZSM5 is 64% aromatics (of which 89% BTX (benzene, toluene, xylenes, ethylbenzene)), 6% hydrogen and 30% fuel gas [44J. Reaction temperatures are in the range 450-500 °C. BP and UOP jointly developed the CYCLAR process based on Ga-H-ZSM5 as the catalyst. 

Aromatization of paraffins is one of the most important conversion process for the production of the aromatics which is of great interest in both petroleum (as gasoline blender) and petrochemical industries. The conversion of lower alkanes to higher value products like benzene, toluene and xylenes over zeolite catalysts is well studied reaction [1-4]. A process for the transformation of propane and butane to aromatics has been developed and commercialized jointly by UOP and BP [5]. The technical feasibility of C3-C4 stream aromatization has been demonstrated by 1000 bbl/day Cyclar process at Grangemouth, U.K. and 200 bbl/day Z-forming pilot plant at Kawasaki Refinery of Mitsubishi Oil, Japan. Both these processes employ high silica, medium pore ZSM-5 zeolite based catalysts for aromatization. 

Since the introduction of the Cyclar process by BP(1), much work has been carried out on the Influence of the procedure for incorporation of dehydrogenating components (Ga or Zn) into the ZSM-5 zeolite, as well as on the mechanism of the conversion of light alkanes to aromatics (2-7). The differences observed among the different catalyst preparations are related to the dispersion and the stoichiometry of the metal oxide. Indeed changes in selectivity to aromatics with time on stream (8) or with a pretreatment of the catalyst with have been associated with the formation of lower valences of Ga as the active dehydrogenating species (6). 

One process that occurs by these mechanisms, called the Cyclar process, uses a gallium-modified zeolite catalyst. The gallium increases the rate of the early cracking steps that generate alkenes. The Cyclar process can convert butane, propane, and ethane to mixtures of benzene, toluene, and the isomeric xylenes. The reactivity order is butane > propane > ethane. 

The successful incorporation of gaUium into ZSM-5 resulted in a cornerstone technology developed by UOP-BP, called the Cyclar process. This catalyst is used for aromatization of tight paraffins to aromatics. 

LPG can be directly converted to aromatics by means of the cyclar process which uses a catalyst composed by Gallium on a ZSM-5 zeolite (134). Conversions higher than 65% with selectivity to aromatics higher than 50% can be achieved. TTie catalyst becomes deactivated after a relatively short time on stream, and the process is carried out in a moving bed type reactor with continuous regeneration. 

Gallosilicate Catalysts. Aromatization of Propane and Butane. Cyclar Process. The Cyclar process, which was discovered by BP and jointly developed with UOP, uses a single catalyst system to convert propane and butanes into aromatic hydrocarbons at high selectivity. The catalyst consists of a zeolite with a non-noble metal promoter. The zeolite component provides a shape-selective acid function, and the non-noble metal additive acts as a dehydrogenation catalyst. ... 

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