Acrylonitrile Lab Report

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Production of Acrylonitrile using Ammoxidation of Propylene

Almost 90% of world production of acrylonitrile (AN) was produced by ammoxidation of propylene process also known as SOHIO process (Standard oil of OHIO). The main chemical reaction and the side reaction occurred in ammoxidation process happen as listed below:
Main Chemical reaction:
C_3 H_6+ 〖NH〗_3+ 〖3⁄2 O〗_2 → C_3 H_3 N+ 〖3H〗_2 O
Propylene+Ammonia+Oxygen →Acrylonitrile+Water (1)

Side Reaction:
C_3 H_6+ 〖NH〗_3+ 〖9/4 O〗_2 → C_2 H_3 N+ 〖3H〗_2 O+ 〖1/2 CO〗_2+1/2 CO
Propylene+Ammonia+Oxygen→Acetonitrile+Water+Carbon dioxide+Carbon monoxide
C_2 H_3 N+ 〖3/2 O〗_2 → HCN+ H_2 O+ 〖CO〗_2
Acetonitrile+Oxygen →Hydrogen Cyanide+Water+Carbon dioxide
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This is highly exothermic reaction with the present of multi component catalyst such as molybdenum, bismuth and iron supported by silica. These catalysts can achieve high selectivity and weak activity that deactivate the process slowly. The drawback using these catalysts is the product is easily poisoned by sulfur compound in the reactant gas. Because of the highly exothermic reaction, it can achieve until 670 to 750 kJ/mol of heat reaction. The superficial velocity of reactant gas inserted into the reactor is very fast by the range of 0.4 to 0.7 m/s and it only taken few seconds of contact time from 5 to 20s in the reactor. Ratio for the gas feed into the fluidized bed reactor by the composition of C3H6: NH3: O2 is 1: 1-1.2: 10-12. The reactor are fed with slightly excess of ammonia of stoichiometry proportion to get the reaction closer to completion and fastening the process of catalyst regeneration. Ammoxidation of propylene give higher conversion till 98% and the selectivity above than 80%. Byproduct produces from this reaction by weight percentage (% wt) base on acrylonitrile are acetonitrile 2-4 % and hydrogen cyanide 14 to 18 %. This byproduct can be market for any other purposed and there are still demands in the chemical industry. The reaction product will be absorb in vapor phase and turn in aqueous phase before being transfer to the distillation column. Most of the acrylonitrile and hydrogen cyanide will be distilled from acetonitrile and water in the first stage of distillation process. While hydrogen cyanide will be remove in the next phase of distillation. To get the purity of 99.8 % the third stage of distillation is required to remove the heavy impurities in the bottom and gained acrylonitrile as a distillate

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