Answer to Question #236041 in Chemical Engineering for Vijay

Question #236041

benzothiophene could be converted to ethylbenzene by a hydrodesulfurization reaction. Before you commit the time and money to design a reactor for this reaction, you may want to attempt to verify that the production of ethylbenzene is economically feasible. In other words, are the products worth more than the reactants and energy required to make them? If you discover the answer is no, you may have saved thousands of dollars in design fees.

(a) Reactor (Plug Flow, Mixed Flow, Packed Bed, Fluidized Bed, etc.) (b) Adiabatic vs. Isothermal reactor operation 

(c) Reactor temperatures and pressures

(d) Feed ratio of hydrogen to benzothiophene 

(e) Effluent conditions and compositions 

(f) Weight of catalyst required 

(g) Material of construction for the reactor (Hint: Is the material susceptible to accelerated corrosion due to the presence of sulfur or hydrogen?) 

(h) Reactor shape and dimensions 

(i) Reactor wall thickness  

Expert's answer

(a) A membrane reactor is really just a plug-flow reactor that contains an additional cylinder of some porous material within it, kind of like the tube within the shell of a shell-and-tube heat exchanger.

(b) The word ‘isothermal’  means constant temperature. An isothermal process is a process occurring at a constant temperature.

The word ‘adiabatic’ means isolated from surroundings. Adiabatic process means a process that neither allows the heat to transfer inside nor let the heat out of the system.

For example, a reaction that takes place in a Dewar Flask is adiabatic. 

In this article, we will discuss adiabatic and isothermal, distinguish between isothermal and adiabatic processes, isobaric isochoric isothermal and adiabatic processes, and understand the process of isothermal adiabatic in detail.

(c)The reactor is rapidly heated directly using an electric current and is capable of rapidly delivering temperatures and pressures up to 400 °C and 200 bar, respectively. ... Reaction temperatures were between 300 and 400 °C with excellent conversions and good to excellent isolated product yields

(d)The HDS of dibenzothiophene on the nitrided catalysts at 573 K with time on stream is shown in Fig. 1. The HDS rate for the LTN catalyst was 126 μmolg- 1 h- 1 at 0.5 h after the start of a run, decreased to 90 μmolg- 1 h- 1 after 4 h, and reached 86 μmolg- 1 h- 1 after 8 h (almost the same rate at 14 h). The HDS rate of the MTN and HTN catalysts also decreased. The major product was biphenyl together with cyclohexylbenzene and small amounts of tetrahydrodibenzothiophene. The rates of dibenzothiophene HDS on the nitrided and sulfided Mo/Al2O3 catalysts at 573 K are shown in Table 1. The LTN catalyst was 1.5 times more active than the MTN catalyst and 1.2 times than the sulfided catalyst (LTS).

(e)Industrial effluent, such as dyes, surfactants, minerals, and certain metals, from industrial processing poses a serious threat to aquatic biota and ecosystems. Depending on the amount and composition of effluents, textile waste is the most damaging contaminant among all the industrial wastes (Vandevivere et al., 1998). 

(f)Centrifugation is doesn’t matter for w/v expression, it is agglomeration of solid particles from free dispersion of impurities. Moreover, it is not important that we have to mention as mol % of catalyst (on unsupported catalyst), in the description of optimization part we can just mentioned it as 20 mg of catalyst has been used. If you represent in percent, then it is no need to represent as % mol, because the unit of g is cancelled out (see this"(20.75 X 103 g)\/ (107.86 g)" . Therefore wt % of catalyst (not mol %) representation is to better for report.

(g) The microelectronic industry applies materials with good electrical and corrosion resistance properties for the manufacturing of the microelectronic devices. Silver and copper are materials with this characteristics used for that purpose. Some of their main applications are as high thermal conductive die attach paste that had silver flakes as conductive filler material, silver plated over copper frames, Sn-Ag and Sn-Cu alloys for solder paste used in Surface Mount Technology (SMT) process, conductive internal copper layers in printed circuit boards, copper wire bonding, and more.

(h) A previously developed one-dimensional reactor model was employed to understand the effects of pellet size and geometry on the performance of a wall-cooled multitubular fixed-bed Fischer–Tropsch reactor for producing hydrocarbons from synthesis gas. The effects of pellet size/shape on catalyst effectiveness, bed void fraction, and overall heat transfer coefficient were studied through a comprehensive parametric study of a reactor with cobalt catalyst. The relative impact of each of these parameters on the overall required amount of catalyst was also determined. The simulations show that the amount of catalyst required to achieve a specified conversion increases with pellet size and shape in the order: trilobes < hollow cylinders < cylinders < spheres. The pressure drop per unit length can be significantly reduced and the catalyst effectiveness increased by using advanced extrudates, i.e., trilobes or hollow cylinders.

(i) thick wall pressure vessels is determined by the ratio between the mean radius of the vessel and the thickness of the wall. If this ratio is greater than 10, the vessel is considered a thin wall pressure vessel. If the ratio is less than 10, the vessel is considered a thick wall pressure vessel.

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