2,2,4-Trimethylpentane, supercritical

Figure 6. Molecular sieve loading as function of oil to molecular sieve ratio using 2,2,4-trimethylpentane supercritical solvent at 522-578 K and 1.34-11.68 MPa...

Figure 5 Free energies for attachment to solutes MeSt— methylst5rene. Sty—styrene, Bph— biphenyl, CO2, Pyr—pyrimidine, Tph— triphenylene, Dfb—p-difluorobenzene, Tol— toluene. But— 1,3-butadiene, Pyz—pyrazine in TMS, 2,2,4-trimethylpentane, and -hexane at 298 K and in supercritical ethane at 310 K. (From Refs. 90-99.)...

Figure 9 Rate constants for electron attachment to CO2 vs. the free energy of reaction in different fluids 0—2,2,4-trimethylpentane [126], —2,2-dimethylbutane [139], O— TMS [126], —supercritical ethane [99],...

In this study, C16-C32 wax distillate is separated into n-paraffin and denormal oil fractions by vapor phase contacting with type 5A molecular sieves. 2,2,4-Trimethylpentane (isooctane), 2,2-dimethylbutane, and 2-methylpentane are each used as the supercritical fluid. Recovery of n-paraffins from the molecular sieves is accomplished by contacting with nitrogen or ammonia gas. 

Volatility Amplification. The solubility of the components in C g-C32 paraffinic wax distillate in supercritical 2,2,4-trimethylpentane was measured at 566 K. This was done by adding increased amounts of the solvent to a fixed amount (341 g) of oil in the autoclave in the absence of molecular sieves and sampling and analyzing the vapor phase. The results are presented in Table 1. The pressures listed are those before and after sampling. 

Nine runs were made with 2,2,4-trimethylpentane as the supercritical solvent at varying solvent/oil ratio, molecular sieve/oil ratio, temperature, and pressure. The runs are listed in the order of increasing molecular sieve/oil ratio in Tables II and III. 

A test was made with 2,3-dimethylbutane as the supercritical solvent it has a lower critical temperature than 2,2,4-trimethyl-pentane. Operating at a temperature of 508-512 K, a pressure of 4.10-4.37 MPa, a molecular sieve/oil ratio of 6.39, and a solvent/ oil ratio of 21.3, the molecular sieve capacity attained is 5.73 g/100 g of molecular sieves (as compared to 3.2 g/100 g of molecular sieves with 2,2,4-trimethylpentane at 550 K). The n-paraffin content of the wax distillate was reduced by 88% to a level of 2 wt %, giving a pour point of 266 K. The yield of denormal oil was lower (63%) and the n-paraffin content of the desorbate was lower (44%) at this lower temperature level. This is probably due to increased capillary condensation. Conversely, operation at temperatures greater than 550 K should produce less capillary condensation and purer n-paraffin product. It would be interesting to try supercritical solvents with critical temperatures in the 600-670 K range. 

Figure 11. Molecular sieve selectivity for supercritical-fluid—molecular-sieve extraction (O) 2,2,4-trimethylpentane (9) 2,3-dimethylbutane...

Supercritical carbon dioxide can be used as a solvent in the BF3 — Et20-catalyzed alkylation of phenols. Under these conditions phenol reacts with 2-chloro-2,4, 4-trimethylpentane and poly(isobutylene)-Cl (PIB-Cl) to give the corresponding para-alkylated phenols (equations 24 and 25) °. 

Figure 4 shows the butene conversion over the silica-supported Nafion catalyst in both liquid and supercritical phases at 368 K, an OWHSV of 0.05 h and an I/O ratio of 10. The liquid phase was maintained at a pressure of 26 bar, while the supercritical phase was maintained at 95 bar, with a 2.4 fold molar excess of carbon dioxide ( 70% total mole fraction CO2). In both cases, a high steady butene conversion is observed. However, the alkylate selectivity continuously declines to zero after 45 hours on stream, at which point the catalyst is only active for butene oligomerization. At the supercritical condition, the acid sites responsible for alkylation are kept active, extending the production of the desired trimethylpentanes. Similar results comparing liquid and supercritical phase runs were also seen on unsupported Nafion . 

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