34362110-Chem-453-chapter-8 - Copy (2)

34362110-Chem-453-chapter-8 - Copy (2) - CHAPTER 8 CHAPTER...

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CHAPTER 8 CHAPTER 8 Chemicals Based on Chemicals Based on Propylene Propylene Professor Bassam El Ali Professor Bassam El Ali
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Dr. Bassam El Ali_CHEM 453 2 INTRODUCTION ± Propylene is a reactive compound that can react with many common reagents used with ethylene such as water, chlorine, and oxygen. ± However, structural differences between these two olefins result in different reactivities toward these reagents. ± For example, direct oxidation of propylene using oxygen does not produce propylene oxide as in the case of ethylene. Instead, an unsaturated aldehyde, acrolein is obtained. ± This could be attributed to the ease of oxidation of allylic hydrogens in propylene.
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Dr. Bassam El Ali_CHEM 453 3 INTRODUCTION ± Similar to the oxidation reaction, the direct catalyzed chlorination of propylene produces allyl chloride through substitution of allylic hydrogens by chlorine. Substitution of vinyl hydrogens in ethylene by chlorine does not occur under normal conditions. ± The current chemical demand for propylene is a little over one half that for ethylene. ± The propylene was used to produce polypropylene polymers and copolymers (about 46%), acrylonitrile for synthetic fibers (Ca 13%), propylene oxide (Ca 10%), cumene (Ca 8%) and oxo alcohols (Ca 7%).
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Dr. Bassam El Ali_CHEM 453 4 OXIDATION OF PROPYLENE ± The direct oxidation of propylene using air or oxygen produces acrolein . Acrolein may further be oxidized to acrylic acid, which is a monomer for polyacrylic resins. ± Ammoxidation of propylene is considered under oxidation reactions because a common allylic intermediate is formed in both the oxidation and ammoxidation of propylene to acrolein and to acrylonitrile, respectively. ± The use of peroxides for the oxidation of propylene produces propylene oxide. This compound is also obtained via a chlorohydrination of propylene followed by epoxidation.
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Dr. Bassam El Ali_CHEM 453 5 OXIDATION OF PROPYLENE ACROLEIN (CH ACROLEIN (CH 2 =CHCHO) =CHCHO) ± Acrolein (2-propenal) is an unsaturated aldehyde with a disagreeable odor. When pure, it is a colorless liquid that is highly reactive and polymerizes easily if not inhibited. ± The main route to produce acrolein is through the catalyzed air or oxygen oxidation of propylene. CH 2 =CHCH 3 + O 2 Æ CH 2 =CHCHO + H 2 O
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Dr. Bassam El Ali_CHEM 453 6 OXIDATION OF PROPYLENE ACROLEIN (CH ACROLEIN (CH 2 =CHCHO) =CHCHO) ± Transition metal oxides or their combinations with metal oxides from the lower row 5a elements were found to be effective catalysts for the oxidation of propene to acrolein. ± Examples of commercially used catalysts are supported CuO (used in the Shell process) and Bi 2 O 3 /MoO 3 (used in the Sohio process). ± In both processes, the reaction is carried out at temperature and pressure ranges of 300-360°C and 1-2 atm.
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Dr. Bassam El Ali_CHEM 453 7 OXIDATION OF PROPYLENE ACROLEIN (CH ACROLEIN (CH 2 =CHCHO) =CHCHO) ± In the Sohio process, a mixture of propylene, air, and steam is introduced to the reactor.
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34362110-Chem-453-chapter-8 - Copy (2) - CHAPTER 8 CHAPTER...

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