Fischer-Tropsch Fuel Cold Flow via Substituted Ethylene Polymer Additive
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Solution Overview
Problem
Fischer-Tropsch derived fuels, with high levels of n-paraffin species, are difficult to treat with conventional middle distillate flow improvers, rendering them unresponsive and challenging to achieve acceptable cold flow properties, especially in cold climates.
Innovation Solution
A fuel composition comprising a Fischer-Tropsch derived middle distillate fuel with a middle distillate flow improver, where the Fischer-Tropsch derived fuel constitutes over 80% of the mixture, and the MDFI is a substituted ethylene polymer with specific acetate to 2-ethylhexanoate ratios and degree of branching, effectively improving cold flow properties to -25 °C or lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional middle distillate flow improvers are used in Fischer-Tropsch derived fuels, then the fuel composition is simple, but the cold flow properties are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular structure parameters of the MDFI additive, specifically the acetate to 2-ethylhexanoate ratio (1:8), the mole percentages (2% acetate, 16% 2-ethylhexanoate), and the degree of branching (4.9 methyl branches per 100 methylene groups). These parameter optimizations enable the additive to effectively modify the cold flow properties of Fischer-Tropsch fuels, achieving CFPP below -25°C while maintaining a simple binary fuel composition.
2Reliability
If the treat rate of MDFI is increased to improve cold flow properties, then the cold filter plugging point decreases, but the amount of additive required increases
Solution Approach 1:
The patent achieves low treat rates (125-4000 mg/kg) by optimizing the molecular parameters of the MDFI additive. The specific structure with controlled branching degree and ester group ratios maximizes the additive's effectiveness in modifying paraffin crystal formation, thereby reducing the quantity needed to achieve the target CFPP below -25°C.
3Stability of the object's composition
If Fischer-Tropsch derived fuels with high n-paraffin content are used, then the fuel has high paraffinic components, but the n-paraffins separate as solids at low temperatures forming gel-like networks
Solution Approach 1:
The MDFI additive acts as an intermediary substance that interacts with n-paraffin molecules during the fuel's operation. The additive's specific molecular structure (substituted ethylene polymer with acetate and 2-ethylhexanoate groups) allows it to modify the crystallization behavior of n-paraffins, preventing them from forming gel-like networks and maintaining flowability at low temperatures while preserving the high paraffinic composition.
Solution Approach 2:
The patent modifies the physical-chemical parameters of the fuel system by introducing an additive with specific molecular characteristics. The controlled degree of branching (4.9 per 100 methylene groups) and ester group composition change how n-paraffins organize at low temperatures, preventing harmful gel network formation while maintaining the desirable high paraffinic content for combustion performance.
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AI summary
The present invention relates to a fuel composition comprising a Fischer-Tropsch derived middle distillate fuel and a middle distillate flow improver, the remainder of the composition being another fuel component or mixture of fuel components, the other fuel component being selected from a petroleum derived middle distillate fuel, hydrogenated vegetable oil, fatty acid methyl esters, and other Fischer Tropsch products such as light F-T base oil; wherein the amount of the Fischer-Tropsch derived middle distillate fuel is more than 80% v/v of the total composition; the maximum weight content in the carbon number distribution of the n-paraffins in the Fischer-Tropsch derived middle distillate fuel is below C16 and the weight ratio of iso to normal paraffins in the Fischer- Tropsch derived middle distillate fuel is 3.5:1 or higher; and wherein the middle distillate flow improver is a substituted ethylene polymer, being a single long alkyl chain substituted with acetate ester groups and 2- ethylhexanoate ester groups and further carrying some methyl branches, wherein the average ratio of acetate to 2-ethylhexanoate is 1:8, the mole percentage of acetate is 2 % and 2-ethylhexanoate 16 %, and the average number of methyl branches per 100 methylene groups is 4.9. The compositions of the invention are useful as fit- for-purpose fuels in climates requiring low temperature flow to around -25 °C or lower, e.g. for the northern European and Arctic climates.