Refinery reaction temperature

At low temperatures, the activity of acid catalysts in transesterification is normally fairly low and to obtain a sufficient reaction rate it is necessary to increase the reaction temperature to >170 °C. Therefore, sulfonic acid resins can be used in esterification reactions where they perform well at temperatures <120 °C and particularly in the pretreatment of acidic oils. Under these reaction conditions, acidic resins are stable. Poly(styrenesulfonic add), for example, has been used in the esterification of a by-product of a vegetable oil refinery with a 38.1 wt% acidity at 90-120 ° C and 3-6 atm. It was not deactivated after the first batch and maintained a steady catalytic performance in the next seven batches [22]. 

Figure 5.3 shows light olefin yields of DCC process in four refineries with different feedstocks at reaction temperatures of 545-565°C. The propylene yield can reach 23 wt% with paraffinic feed, and about 18-19 wt% with intermediate-based feed. The propylene/ethylene ratio is about 3.5-6.2, much higher than that of steam cracking. The DCC operation can be modified to further increase the yield of propylene. For example, recycling a part of DCC cracked naphtha to the reactor resulted in a propylene yield increment of 3.5 wt % in Jinan Refinery [16]. 

Several furnaces are found in a number of oil refinery units. They are mainly used for preheating the feed to a reaction temperature before the feed enters a reactor or a distillation column. Furnace tubes are usually designed for a limited service life of 10 years [1]. However, some damage to the tubes is unavoidable during this time, regardless of proper material selection and the correct operation conditions. 

The hydrocarbon gas feedstock and Hquid sulfur are separately preheated in an externally fired tubular heater. When the gas reaches 480—650°C, it joins the vaporized sulfur. A special venturi nozzle can be used for mixing the two streams (81). The mixed stream flows through a radiantly-heated pipe cod, where some reaction takes place, before entering an adiabatic catalytic reactor. In the adiabatic reactor, the reaction goes to over 90% completion at a temperature of 580—635°C and a pressure of approximately 250—500 kPa (2.5—5.0 atm). Heater tubes are constmcted from high alloy stainless steel and reportedly must be replaced every 2—3 years (79,82—84). Furnaces are generally fired with natural gas or refinery gas, and heat transfer to the tube coil occurs primarily by radiation with no direct contact of the flames on the tubes. Design of the furnace is critical to achieve uniform heat around the tubes to avoid rapid corrosion at "hot spots."... 

Acidic micro- and mesoporous materials, and in particular USY type zeolites, are widely used in petroleum refinery and petrochemical industry. Dealumination treatment of Y type zeolites referred to as ultrastabilisation is carried out to tune acidity, porosity and stability of these materials [1]. Dealumination by high temperature treatment in presence of steam creates a secondary mesoporous network inside individual zeolite crystals. In view of catalytic applications, it is essential to characterize those mesopores and to distinguish mesopores connected to the external surface of the zeolite crystal from mesopores present as cavities accessible via micropores only [2]. Externally accessible mesopores increase catalytic effectiveness by lifting diffusion limitation and facilitating desorption of reaction products [3], The aim of this paper is to characterize those mesopores by means of catalytic test reaction and liquid phase breakthrough experiments. 

In the above process, finely divided iron oxide combined with sodium oxide and silica or alumina is used as the catalyst. The reaction is favored (as per Le Chatelier s principle) by high pressure and low temperature. However, a temperature of 500 to 550°C is employed to enhance the reaction rate and prevent catalyst deactivation. Although at 200°C and 250 atm the equihbrium may yield up to 90% ammonia, the product yield is too slow. The sources of hydrogen in commercial processes include natural gas, refinery gas, water gas, coal gas, water (electrolysis) and fuel oil, and the nitrogen source is liquefied air. 

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