Oligomerisation Diluent Solvent Boiling Point Selection
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Solution Overview
Problem
The recovery of diluent solvents in hydrocarbon oligomerization processes is energy-intensive, and existing solvents like propane have boiling points close to ethylene, making separation difficult and increasing energy consumption.
Innovation Solution
A process using organic liquid diluents with boiling points below 1-hexene but above −20°C, such as isobutane and isopentane, is employed, allowing for efficient solubility of ethylene and reducing energy requirements through evaporative cooling and single-stage absorption refrigeration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional diluent solvents like propane are used, then ethylene solubility is achieved, but separation becomes difficult due to close boiling points, increasing energy consumption
Solution Approach 1:
The patent changes the boiling point parameter of the diluent solvent from close to ethylene (propane at -42°C) to significantly higher than ethylene but below 1-hexene (e.g., isobutane at -11.7°C, isopentane at 27°C, neopentane at 9.5°C). This parameter change enables effective separation of ethylene from the diluent solvent through distillation while maintaining good ethylene solubility in the liquid phase, thereby reducing energy consumption for solvent recovery.
2Manufacturing precision
If diluent solvent concentration is increased to reduce secondary incorporation, then selectivity improves, but solvent recovery becomes more energy intensive
Solution Approach 1:
The patent optimizes the diluent solvent concentration in the liquid phase to a specific range (30-80 mass%) that simultaneously achieves high selectivity for co-monomer products and facilitates energy-efficient solvent recovery. The selected solvents with optimized boiling points enable effective separation at these concentrations, resolving the contradiction between maintaining high selectivity and minimizing energy consumption for recovery.
3Quantity of substance
If solvents with boiling points close to ethylene are used, then ethylene solubility is maintained, but separation difficulty increases and refrigeration costs rise
Solution Approach 1:
The patent selects diluent solvents whose boiling points are significantly higher than ethylene (-103.7°C) but below 1-hexene (63°C), creating a clear boiling point gap that simplifies separation. Examples include isobutane (-11.7°C), isopentane (27°C), and neopentane (9.5°C). This parameter change maintains adequate ethylene solubility in the liquid phase while dramatically improving ease of separation through distillation or evaporation, thereby reducing refrigeration and separation costs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces energy consumption by enabling efficient ethylene solubility, lowering secondary product formation, and simplifying solvent recovery, thereby decreasing refrigeration costs and improving process efficiency.
Implementation Method 1
said organic liquid diluent solvent having a normal boiling point below the normal boiling point of 1-hexene but above −20° C.
Implementation Method 2
lowering secondary product formation, and simplifying solvent recovery, thereby decreasing refrigeration costs and improving process efficiency
Data Source
AI summary
A process (10) for oligomerising a hydrocarbon to form at least one co-monomer product (22) includes feeding a hydrocarbon reactant and organic liquid diluent solvent (32) into an oligomerisation reactor (12). The organic liquid diluent solvent has a normal boiling point below the normal boiling point of 1-hexene but above −20° C., or the organic diluent solvent is in the form of a solvent admixture with at least 70% by mass of the solvent admixture constituting organic diluent solvents having a normal boiling point below the normal boiling point of 1-hexene but above −20° C. The oligomerisation reactor (12) holds at least one co-monomer product formed in the oligomerisation reactor admixed with a catalyst system (25) introduced into the oligomerisation reactor (12). The catalyst system (25) includes a catalyst dissolved in at least one catalyst solvent. At least a portion of the hydrocarbon reactant is oligomerised in the reactor (12) to form co-monomer product and polymeric by-product as part of a liquid product, which is withdrawn. When there is only one catalyst solvent and only one organic liquid diluent solvent, the catalyst solvent and the organic liquid diluent solvent are not the same solvent. When there is more than one catalyst solvent or more than one organic liquid diluent solvent, at least one of the catalyst solvents is not also used as organic liquid diluent solvent or at least one of the organic liquid diluent solvents is not also used at the catalyst solvent. The mass ratio of all organic liquid diluent solvent introduced into the oligomerisation reactor to all catalyst solvent introduced into the oligomerisation reactor over a selected time period is between 15:1 and 4500:1.