Zeolite catalysts described, 164

Another patent apphcation (28) describes the use of zeolite/TUD-1 with optionally a metal function for a variety of reactions. In an example, as-synthesized MCM-22 / TUD-1 was tested for acylation of 2-methoxynaphthalene with acetic anhydride to 2-acetyl-6-methoxynaphthalene at 240°C. After reaction for six hours, conversion of 2-methoxynaphthalene reached 56% with 100% selectivity to 2-acetyl-6-methoxynaphthalene. Other zeolite catalysts were similarly tested, but none were nearly as effective. 

Although the mechanism proposed for the ZSM-5/methanol system adequately explains the production of the primary C2-C5 products, it is not clear how these are converted into the final gasoline product or indeed why this product should be so rich in aromatics. Production of olefins from methanol over zeolite catalysts has previously been described (110, 112) however, the ZSM-5 system appears to be unique with respect to both product selectivity and catalyst stability. Mobil now has some 140 patents relating to the preparation and use of ZSM-5 zeolites and has stated that "given a favorable economic and political climate a commercial unit could be in operation by the early 1980 s (101). 

The purpose of this chapter is to provide general guidance for the various characterization techniques that are most often employed in the development and commerciaHzation of new zeolites, catalysts and adsorbents. Each of these techniques can be a volume unto itself. Thus we only briefly describe the technique but emphasize the information that can be obtained by the particular method and the utiHty of that information for characterizing zeoHtes, zeolitic catalysts and zeoHtic adsorbents. The Hmitations of the various techniques are included to assist the novice. For a more in depth understanding of the various techniques, references are given throughout the chapter. 

The Beta-zeolite catalyst samples were purchased from PQ Corporation and from UOP. The HF-treated p-zeolite and montmorillonite clay samples were prepared as described previously (9,12). 

Silica is of particular importance because of its use as a stable catalyst support with low acidity and its relationship to zeolite catalysts, which will be discussed in chapter 4. Silicon is an abundant material in the earth s crust and occurs in various forms including silica. Silica is also polymorphous with the main forms being quartz, cristobalite and trydimite. The stable room temperature form is quartz (Si02). Recently, a new family of stable silica-based ceramics from chemically stabilized cristobalites has been described using electron microscopy (Gai et al 1993). We describe the synthesis and microstructures of these ceramic supports in chapters 3 and 5. 

Zeolite catalysts may also be regarded as mixed oxides, but the crystallographic structures differ from the solids discussed above in that active sites for catalysis occur within the open lattice framework. In consequence, rate data are not directly comparable with similar observations for other heterogeneous reactions since the preexponential factors are calculated and reported on a different basis. For completeness, however, it is appropriate to mention here that instances of compensation behavior on zeolite catalysts are known. Taylor and Walker (282) described such an effect for the decomposition reactions of formic acid and of methyl forma te on cation-exchanged 13X molecular sieves, and comparable trends may be found in data reported for reactions of propene on similar catalysts (283). 

This was a liquid-phase process which used what was described as siliceous zeolitic catalysts. Hydrogen was not required in the process. Reactor pressure was 4.5 MPa and WHSV of 0.68 kg oil/h kg catalyst. The initial reactor temperature was 127°C and was raised as the catalyst deactivated to maintain toluene conversion. The catalyst was regenerated after the temperature reached about 315°C. Regeneration consisted of conventional controlled burning of the coke deposit. The catalyst life was reported to be at least 1.5 yr. 

The experiments were carried out in a small flow type fixed bed reactor which has been described in a recent publication (9) along with the methods of analysis by capillary gas-liquid chromatography. Results are reported that were gained with all pure n-alkanes ranging from n-hexane to n-dodecane. Feed hydrocarbons were delivered from Fluka, Buchs, Switzerland (purum). Purity exceeded 99. 5 wt. -% in any case. The Pt/Ca-Y-zeolite catalyst (0. 5 wt. -% Pt, SK 200, Union Carbide, Linde Division volume of catalyst bed 2 cm3 particle size 0. 2 - 0. 3 mm) was calcined in a dried stream of Ng and activated in a dried stream of at atmospheric pressure prior to use. The mass of dry catalyst was 1.0 g. The total pressure and molar ratio hydrogen n-alkane were kept constant at 39 bar and 17 1, respectively, whereas the reaction temperatures and space velocities were varied. 

The thermal and catalytic conversion of different hydrocarbon fractions, often with hydrotreating and other reaction steps, is characterized by a broad variety of feeds and products (Table 1, entry 4). New processes starting from natural gas are currently under development these are mainly based on the conversion of methane into synthesis gas, further into methanol, and finally into higher hydrocarbons. These processes are mainly employed in the petrochemical industry and will not be described in detail here. Several new processes are under development and the formation of BTX aromatics from C3/C4 hydrocarbons employing modified zeolite catalysts is a promising example [10],... 

The key to the process was the development by Mobil of a size-selective zeolite catalyst, whose geometry and pore dimensions have been tailored so that it selectively produces hydrocarbon molecules within a desired size range. This is a highly exothermic reaction and the major problem in any plant design is the reactor system to effect the necessary heat removal. A plant completed in 1985 in New Zealand uses about 4 million m3/day of natural gas as the feedstock to produce the methanol by the ICI procedure described above. In 1990 the plant produced about 16,000 bbl/day of gasoline, which is somewhat above its design output. 

In literature in this field, a large number of zeolite catalysts (FAU, MOR, ZSM-5, BEA, etc.) have been described as active catalysts in the acylation of aromatics.[2] One of the solid acid catalysts that gives very high activities and selectivities is the... 

In US Patent 5,569,785 an attrition-resistant zeolite catalyst is described that can be used for the production of methylamines in fluidized bed reactors. The technology claims to provide improved temperature control because of better heat transfer and more efficient solids handling in the fluidized bed. The process also offers more precise temperature control to maintain the activity of the catalyst and eliminate the formation of hot spots that lead to catalyst deactivation. 

Impregnation and ion-exchange methods for preparation of supported catalysts are discussed in detail in Section 2.2.1.1. Only ion exchange in the solid state as a novel method to prepare zeolite catalysts is described here. 

The production of LAB involves the liquid-phase alkylation of benzene with linear monoolefins or alkyl chlorides. Liquid HF is used as catalyst for linear monoolefins. And the A1C13 is used as the catalyst for alkyl chlorides. Nowadays, acidic zeolite catalyst is used for olefin alkylation which generates less waste and reduces manufacture cost. The alkylate is then sulfonated to produce linear alkylbenzene sulfonate for biodegradable detergents. The manufacture of detergents is described in detail in Chapter 27. 

A typical ethanolamine flowsheet is shown in Fig. 22.25.117 Nippon Shokubai has developed technology that uses a zeolite catalyst that suppresses the formation of TEA and produces more MEA and DEA.120 Another process flowsheet is described in Reference 121 along with detailed process conditions. 

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