Liquid continuous catalyst regeneration

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

Description The process consists of a reactor section, continuous catalyst regeneration (CCR) section and product-recovery section. Stacked radial-flow reactors (1) facilitate catalyst transfer to and from the CCR catalyst regeneration section (2). A charge heater and interheaters (3) achieve optimum conversion and selectivity for the endothermic reaction. Reactor effluent is separated into liquid and vapor products (4). The liquid product is sent to a stripper column (5) to remove light saturates from the C6 aromatic product. Vapor from the separator is compressed and sent to a gas recovery unit (6). The compressed vapor is then separated into a 95% pure hydrogen coproduct, a fuel-gas stream containing light byproducts and a recycled stream of unconverted LPG. 

I. G. Farben also produced butene by butane dehydrogenation. A moving catalyst bed system was used in a tubular reactor. The total catalyst charge was 1.5 tonnes with a residence time of 4 h in the tubes. Yields of 85% at 20-25% conversion were obtained at a liquid space velocity of 2 h and 620°-650°C operating temperature. This was an impressive result for a new reactor design that has now been developed as the continuous catalyst regeneration process and is widely used in refineries. 

Solid acid catalysts such as mixed oxides (chalcides) have been used extensively for many years in the petroleum industry and organic synthesis. Their main advantage compared with liquid acid catalysts is the ease of separation from the reaction mixture, which allows continuous operation, as well as regeneration and reutilization of the catalyst. Furthermore, the heterogeneous solid catalysts can lead to high selectivity or specific activity. Due to the heterogeneity of solid superacids, accurate acidity measurements are difficult to carry out and to interpret. Up until now, the most useful way to estimate the acidity of a solid catalyst is to test its catalytic activity in well-known acid-catalyzed reactions. 

The CCR Meta-4 process features are a hard, highly active and robust catalyst, low catalyst inventory, low operating temperature and pressure, outstanding yields, liquid-phase operation, and continuous operation and catalyst regeneration. 

Fixed bed and liquid riser type reactors are found in the majority of the proposed commercial solid acid alkylation processes, as will be detailed hereinafter. Nevertheless, other reactor configurations have been proposed for alkylation processes employing solid catalysts. For instance, a spouted bed reactor is constituted by a gas flow propelled riser, an annular downcomer where part of the solid and liquid are recycled to the reactor inlet and a hydrocyclon in which the solid catalyst is collected to be regenerated in continuous at a neighboring unit. Recently, a spouted bed reactor equipped with a fluidized-bed catalyst regenerator has been designed to be used in solid alkylation processes, employing a Pt/S0x(Zr-Ti)02... 

The best solution appears to be the use of an almost insoluble liquid catalyst held within the pores of a suitable inert support. Supported liquid catalysts are well known and can be used with a continuous catalytic regeneration system similar to that developed for catalytic reforming processes. Haldor Topsoe has successfully tested trifluoromethane sulfonic acid in this way since 1993 with a variety of olefin feeds. " No formal regeneration was necessary apart from periodic removal of some catalyst for reimpregnation and the recovery of dissolved acid from the alkylate. Both catalyst and support are, therefore, recirculated. The small quantity of polymeric by-products formed (acid soluble oil) appears to be less tlm that formed in the sulfuric acid process, but slightly more than in the HF process. 

In a typical fluid catalytic cracker, catalyst particles are continuously circulated from one portion of the operation to another. Figure 9 shows a schematic flow diagram of a typical unit W. Hot gas oil feed (500 -700°F) is mixed with 1250 F catalyst at the base of the riser in which the oil and catalyst residence times (from a few seconds to 1 min.) and the ratio of catalyst to the amount of oil is controlled to obtain the desired level of conversion for the product slate demand. The products are then removed from the separator while the catalyst drops back into the stripper. In the stripper adsorbed liquid hydrocarbons are steam stripped from the catalyst particles before the catalyst particles are transferred to the regenerator. 

Cracking of n-heptane was carried out on catalysts USY-1 and U1F-25 in a continuous flow, fixed bed reactor (15), at 450 aC and atmospheric pressure. In all experiments, 0.223 g of zeolite catalyst, and 8.625 g of n-heptane were used. With each catalyst the reaction was performed at 75, 150 and 375 seconds of time on stream. The catalyst was regenerated "in situ" after each experiment by passing flow of air at 5209C during 4 hours, and liquids were analyzed by GC by means of a Porapak-Q silica and a S-30 columns respectively. 

The slurry tank, when well mixed, can be considered a continuous-stirred tank reactor for both the gas phase and the liquid phase. When the solid is retained in the reaction vessel, it behaves in a batch mode however, catalyst can be removed and regenerated easily in a slurry tank, so activity can be maintained. 

A number of industrial reactors involve contact between a fluid (either a gas or a liquid) and solids. In these reactors, the fluid phase contacts the solid catalyst which may be either stationary (in a fixed bed) or in motion (particles in a fluidized bed, moving bed, or a slurry). The solids may be a catalyst or a reactant (product). Catalyst and reactor selection and design largely depend upon issues related to heat transfer, pressure drop and contacting of the phases. In many cases, continuous regeneration or periodic replacement of deteriorated or deactivated catalyst may be needed. 

Furthermore, CMRs present the advantage of avoiding the separation step of the catalyst from the liquid phase, which is often a critical step in classical slurry reactors. CMRs are also able to operate in a continuous mode, and regeneration procedures for the catalyst are easier. 

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