Chemical Engineering Production Process

Production Process

• The production process involves three main steps: preparation of porous silica gel, addition of aluminum salt, and dehydration at temperatures exceeding 400 °C.
• The preparation stage creates spherical particles of silica hydrogel with silanol groups on the surface.
• Aluminum salts, specifically Al(OH)3·3H2O, react with silanol groups to impart a negative charge on Al3+, balanced by hydrated cations on the silica surface.
• Dehydration converts Brønsted acidic sites to Lewis acidic sites, enhancing catalytic activity.
• Catalysts derived from this process exhibit low thermal stability and are prone to sintering, especially in steam environments during stripping and regeneration.

Zeolite Catalysts

• Zeolites are natural crystalline catalysts made of sodium alumino-silicates with a porous 3D structure.
• Synthesized by mixing Na2SiO3 and NaAlO2 under specific pH conditions, zeolite crystallization is promoted through heating of the precipitate.
• The size of zeolite cavities can be altered by varying the R group of quaternary ammonium salts included during the synthesis.
• Zeolite catalysts show high selectivity for C5-C10 gasolines and are more active in hydrogen transfer than in hydrocarbon chain cleavage.
• Hydrocarbon cleavage halts at higher molecular weights due to the transformation of hydride ions to carbocations and subsequent olefin hydrogenation.
• Issues with zeolite catalysts include coke formation and potential reversible catalyst inhibition.

Effects of Compounds on Catalysts

• Sulfur increases SO2 emissions during catalyst regeneration, which can be managed through amine washing or the Claus process.
• Nitrogen can generate ammonia, which neutralizes acidic catalyst sites, while oxygen and arsenic can poison Pt catalysts.
• Organometallic compounds convert to heavy metals that can deactivate catalysts, with vanadium specifically causing sintering.
• Sodium and potassium irreversibly neutralize zeolites' acidic sites.

Hydrotreating

• A high-pressure hydrotreating process (5-20 atm) using Co-Mo, Ni-Mo, or Ni-W catalysts is effective for removing sulfur and other heteroatoms before cracking processes.
• This method helps desulfurize gasoils for diesel fuels and fuel oil, minimizing catalyst deactivation during catalytic cracking.
• Hydrotreating serves to reduce coke formation from olefins and ammonia while also removing oxygen, nitrogen, and arsenic to protect Pt catalysts.

Hydrocracking

• Hydrocracking involves severe hydroprocessing to remove heteroatoms and saturate carbon-carbon bonds.
• It results in higher yields of fuel products compared to mild hydrotreating.
• The conversion rate in hydrocracking is notably higher than in mild processes, making products more suitable for diesel rather than gasoline.

Petroleum Products

• The petrochemical industry transforms low-value raw materials into high-value products, often with a higher H/C ratio.
• Residue conversion processes address the treatment of heavy crude oils, recovering valuable products and reducing waste.
• Heavy residue is characterized as high molecular weight, carbon-rich, and low-value, leading to the recovery of fuel gas and LPG and the production of petroleum coke, which can be used as fuel in power plants.

Fluidized Bed Coking

• The fluidized bed coking process integrates a coke reactor with a furnace-burner unit, using steam to maintain coke motion and facilitate cracking at high temperatures (500-550 °C).
• The process generates various product yields, with more gasoil and less gasoline compared to delayed coking.
• A portion of produced coke is collected while combustion gases are removed for carbonaceous particle separation.

Flexicoking

• Flexicoking includes a gasifier to enhance flexibility, converting around 90% of feed into liquids and gases and allowing excess coke to be gasified for energy or chemical production.

Asphaltenes Extraction

• Asphaltenes, the heaviest petroleum components, contain impurities and are solid at room temperature.
• Removing asphaltenes increases gasoil yield during cracking processes and allows for their use as fuels in cement production and asphalt manufacturing.
• The deasphalting process involves solvent recovery of non-asphaltene materials from both atmospheric and vacuum residues.

Explore the three main steps involved in the production process of porous silica gel. This quiz covers the preparation, addition of aluminum salt, and dehydration processes that lead to the formation of silica hydrogel particles with silanol groups. Test your knowledge on this essential chemical engineering topic.