Chapter 6 -_comparison_ht_hc
- 1. Hydrotreating Properties Hydrocracking 10% - 20% Conversion > 50% To improve the quality of final product by removing all the impurities such as sulfur, nitrogen, grease, and others Purpose To crack large molecules into small molecules by heating and the help of catalyst and hydrogen • ruthenium disulfide, RuS2. molybdenum disulfide, MoS2 (hydrodesulfurization) • Ni-Mo-S/Al2O3 or Co-Mo-S/Al2O3 (hydrodesulfurization) Catalyst Uses • Al2O3 (thermal cracking) • Co/Mo (Hydrogenation) Hydrodesulfurization and hydrodenitrogenation Type • Isomas, Unicracking, Ultracracking, DOFining Temperature: 315.56oC- 398.89oC(600oF- 750oF) Pressure: 5515.8 kPa- 20,684.27 kPa(800psi- 3,000psi) Operating Condition Temperature: 260oC- 425oC (500oF- 797oF) Pressure: 35 bar – 200 bar(3500kPa- 20000kPa) • (Hydrodesulfurization) C2H5SH+H2C2H6+H2S • (Hydrodenitrogenation) C5H5N + 5H2 C5H12 + NH3 Reaction Involved • (Thermal cracking) C7H16 C3H8 +C4H8 • (Hydrogenation) C4H8 + H2 C4H10 + Heat
- 2. Hydrotreating versus Hydrocracking Hydrotreating Criterias Hydrocracking Sulphur, metals and nitrogen removal and increasing *cetane number (reaction with hydrogen) Purpose of reaction Breaking of long hydrocarbon chains to shorter ones 10% to 20% Conversion rate More than 50% Temperature: 350°C – 390 °C Pressure: 60 bar – 90 bar Operating conditions Temperature: 350°C – 420 °C Pressure: 85 bar – 200 bar Cobalt and Nickel Molybdenum Catalyst used Platinum, palladium, tungsten Suitable for further processing (reforming, catalytic cracking) Products specification Suitable for diesel than gasoline De-oxidation of Phenol: C6H5OH + H2 C6H6 + H2O Example of reaction Cracking of n-Heptane: n-Heptane Toluene + 4 H2 * Cetane number - measurement of the combustion quality of diesel fuel during compression ignition
- 3. Hydrocracking Hydrotreating Catalyst use Dual function catalyst: Mixture of silica alumina with a small uniformly distributed amount of rare earths contained within the crystal lattice. Molybdenum oxides on alumina, nickel oxide, nickel thiomolybdate, tungsten and nickel sulfides, and vanadium oxide. Feedstock • Straight run vacuum gas oil • Coker heavy gas oil • De-asphalted oil • Hydro treated effluent • Naphtha • Olefins • Liquid distillate containing sulfur compounds Hydrogen consumption High consumption of hydrogen in hydro-desulfurization and hydro- denitrogenation Minimal in hydrotreating, even during aromatic saturation Product • Jet fuel • Diesel • Kerosene • Saturated olefins • Light naphtha • Kerosene • Low sulfur fuel oil Reactor Configuration • Effluent beds • Expanded circulating bed • Down-flow fixed bed