Industrial Chemistry - Reaction Order Calculations

Industrial Chemistry - Calculations of Reaction Order

• Reminder: All reactions are reversible in this chapter; use the reversible symbol (⇌) in chemical equations.
• Table: A table shows experiment data, including initial concentrations of reactants A and B, and their corresponding initial reaction rates.

Industrial Chemistry - Rate Constant

• Units: The rate of reaction has units of mol dm⁻³ s⁻¹, and the rate constant's unit balances the reaction equation's units to result in mol dm⁻³ s⁻¹.
• Zeroth Order: mol dm⁻³ s⁻¹
• First Order: s⁻¹
• Second Order: dm³ mol⁻¹ s⁻¹
• Third Order: dm⁶ mol⁻² s⁻¹

Industrial Chemistry - Graph of log(rate) vs. log(concentration)

• Equation: Rate = k[A]^x[B]^y
• log (rate) = n log [A] + log k
• Slope: Order of reaction
• Y-intercept: log(rate constant)
• Graph Result: BOTH order of reaction & rate constant from the graph.

Industrial Chemistry - Activation Energy

• Definition: The minimum energy required for a chemical reaction to occur.
• Effective Collisions: Reactant particles must collide with the correct orientation and energy above the activation energy.
• Formula: k = Ae^−Ea/RT, log k₁/k₂ = Ea/(2.3R)[(1/T₁) − (1/T₂)]
• Gas Constant(R): 8.314 J K⁻¹ mol⁻¹
• Important note: Temperatures in the Arrhenius equation are in Kelvin (K). Convert Celsius to Kelvin by adding 273. Also, the calculation result's unit will be J mol⁻¹ which must be converted to kJ mol⁻¹.

Industrial Chemistry - Energy Profile

• Activated Complex/Transition State: Exists at the maximum energy point, containing partially broken and partially formed bonds; highly unstable and cannot be isolated.
• Intermediate: Mixture of chemicals between reaction steps, formed between the peaks in the energy profile graph; can be isolated.
• Rate Determining Step: The reaction step with the highest activation energy (Ea); typically the first peak in the energy profile.
• Catalyst Effect: A catalyst lowers the activation energy, resulting in a lower peak on the energy profile graph.

Industrial Chemistry - Maxwell-Boltzmann Distribution Curve

• Area Under Curve: Total number of particles remains the same regardless of temperature.
• Kinetic Energy Increase: Increased temperature leads to more particles with kinetic energy greater than the activation energy and increased reaction rate.
• Catalyst Effect: With a catalyst, activation energy decreases and more molecules can exceed this energy threshold, further increasing reaction rate.

Industrial Chemistry - Catalyst

• Definition: Provides an alternative reaction pathway with lower activation energy.
• Unchanged: Remains chemically unchanged throughout the reaction.
• Specificity: Catalysts are often specific to a particular reaction.
• Effect on Equilibrium: Catalysts affect the rate of both the forward and backward reactions equally, therefore catalysts do not change the equilibrium constant or position.
• Homogeneous/Heterogeneous: Homogeneous catalysts share the same physical state as reactants, Heterogeneous catalysts have different physical states.

Industrial Chemistry - Haber Process

• Equation: N₂ + 3H₂ ⇌ 2NH₃
• Conditions: 450°C and 200 atm with finely divided iron as a catalyst.
• Use: Production of ammonia for fertilizer.

Industrial Chemistry - Steam Reforming of Methane

• Equation: CH₄ + H₂O ⇌ CO + 3H₂
• Conditions: 700-1000°C and 30 atm; endothermic.
• Use: Produces syngas (a mixture of CO and H₂); further H₂ can be produced from CO.
• Note: Reaction requires heat, but preheating the reactants is used in order to save energy.

Industrial Chemistry - Production of Methanol

• Equation: CO + 2H₂ ⇌ CH₃OH
• Conditions: 250°C, 50-100 atm, with Cu-ZnO-Al₂O₃ catalyst.
• Use: Produces methanol, which can be used to make formaldehyde and acetic acid.

Industrial Chemistry - Production of Nitric Acid

• Equations: 4NH₃ + 5O₂ ⇌ 4NO + 6H₂O, 2NO + O₂ ⇌ 2NO₂, 4NO₂ + 2H₂O + O₂⇌ 4HNO₃.
• Conditions: 900°C, 8 atm, platinum alloy catalyst.
• Use: Producing nitric acid; key in producing fertilizers.

Industrial Chemistry - Reichstein Process (Vitamin C Production)

• Equation: Glucose → Sorbitol → Sorbose → KGA → Vitamin C
• Note: Natural vitamin C production cannot keep up with demand, therefore the chemical process is necessary to meet supply.

Industrial Chemistry - Electrolysis of Brine

• Two Processes:
  • Flowing Mercury Cell (Uses Hg): Uses Hg as cathode, with a Na/Hg intermediate produced; the use of Hg is harmful and energy intensive.
  • Membrane Cell: Uses a membrane to separate the chlorine and the sodium hydroxide products. This cell is better in terms of safety and energy efficiency.

Industrial Chemistry - Conditions for Optimum Reaction Yields

• Pressure: Higher pressures favor reactions with fewer moles of gas on the product side.
• Temperature: Endothermic reactions favor higher temps; exothermic reactions favor lower temps.
• Catalyst: Accelerates reaction rates without changing equilibrium, thus not affecting yield.
• Reactants: Continuously adding reactants shifts equilibrium towards product formation.
• Product Removal: Continuously removing products shifts equilibrium towards product.

Industrial Chemistry - Principles of Green Chemistry

• Atom Economy: Percentage of reactant atoms converted into desired product.
• Less Steps: Fewer steps minimize waste.
• Less Toxic Chemicals: Use less harmful/toxic chemicals.
• Energy Efficiency: Use catalysts for energy efficiency; renewable resources, etc.
• Renewable Materials: Use renewable materials whenever possible.

Industrial Chemistry - Manufacture of Ethanoic Acid

• Fermentation: Relatively low-energy process using sugar and yeast. Yield is also low.
• Monsanto Process: High-pressure high-temperature process using a rhodium catalyst; high yield; there are also side reactions. A CATIVA process is more efficient, resulting in less waste.