OSDA-free synthesis of FeZSM-22 zeolite from natural minerals for n-octane hydroisomerization

A seed-directed approach to synthesizing Fe ZSM-22 zeolite without organic structure directing agent(OSDA)was developed by using Fe-rich diatomite as all aluminum and iron sources.The Fe ZSM-22zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions.Characterizations show that Fe ZSM-22 zeolite synthesized with OSDA-free owns high crystallinity,obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio.Significantly,when used for n-octane hydroisomerization reaction,its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C_(8)isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals,respectively.This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance.

Effect of preparation method on the bimetallic NiCu/SAPO-11 catalysts for the hydroisomerization of n-octane

The bimetallic NiCu/SAPO-11 catalysts were prepared by co-impregnation, sequential impregnation, coprecipitation, and mechanical mixing methods. Powder X-ray diffraction, nitrogen adsorption-desorption,temperature-programmed desorption of ammonia, transmission electron microscopy, temperatureprogrammed reduction of hydrogen, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the catalysts. The catalytic performance of the catalysts was assessed by the hydroisomerization of n-octane. Results indicated that the conversion of n-octane and selectivity to n-octane isomers were related to the preparation methods of the catalysts. The catalysts with Ni-Cu alloy effectively restrained the hydrogenolysis reaction that decreases the selectivity of isomerization. The catalyst prepared by the mechanical mixing of NiO and CuO hardly formed Ni-Cu alloy, showing obvious hydrogenolysis and low selectivity to n-octane isomers. The unbalance between the metal and acid sites resulted in the low conversion of n-octane and selectivity to n-octane isomers. Among all the catalysts,the catalyst prepared by the co-impregnation method exhibited high catalytic activity and selectivity to n-octane isomers.

Effect of silicon precursor on silicon incorporation in SAPO-11 and their catalytic performance for hydroisomerization of n-octane on Pt-based catalysts

SAPO-11 molecular sieves were synthesized using silica sol, hydrophilic fumed silica, and tetraethyl orthosilicate（TEOS） as silicon precursors. Their physicochemical properties were characterized using XRD,SEM, nitrogen adsorption-desorption, Py-IR, NH;-TPD, EDS, and;Al,;P,;Si MAS NMR techniques. The catalytic performance was assessed in the hydroisomerization of n-octane. The results showed that the silicon precursors influenced the physicochemical properties and catalytic performance of SAPO-11. SAPO-11 synthesized using hydrophilic fumed silica as silicon precursor showed higher silicon distribution and had more medium acid sites. SAPO-11 synthesized using TEOS as silicon precursor had more silicon content, but more silicon islands formed in its framework. The depolymerization of silicon precursors might affect the silicon content and distribution in SAPO-11. In the hydroisomerization of n-octane, the catalytic activity strongly depended on the number of medium acid sites instead of the number of total acid sites.SAPO-11 synthesized using hydrophilic fumed silica as silicon precursor exhibited higher catalytic activity than the other samples because it has more medium acid sites.

Isomerization of n-octane on NiW/HSAPO-11 Catalyst

The catalyst NiW/HSAPO-11 was prepared by impregnating Ni and W onto HSAPO-11 zeolite with two different methods. The isomerization and aromatization properties were investigated with an microreactor using n-octane as a feedstock. NiW/HSAPO-11 shows a high hydroconversion activity of n-octane, and the optimum operating parameters for the catalyst to produce high octane number products were: 400℃, 2.0MPa, VH2:Vn-octane= 400:1, liquid hourly space velocity LHSV=1.0h-1. Under the optimum reaction condition, the conversion efficiency, C5 liquid + product selectivity, isomerization and aromatization product selectivity were 69.80%, 56.95%, 79.73% and 1.29% respectively. The catalyst (S1) impregnated with Ni and W after the HSAPO-11 zeolite was combined with Al2O3 matrix, performed better than the catalyst (S2) impregnated with Ni and W before combining with the Al2O3 matrix.

Catalytic performance of Pt/HY-β in n-octane hydroisomerization

A bifunctional catalyst Pt/HY-β was prepared from a bimicroporous composite zeolite Y-β. Characterization results showed that the specific surface area, pore volume, and acid amount of the catalyst Pt/HY-β all decreased compared to the original zeolite. The catalytic performance of this catalyst in n-octane hydroisomerization was investigated in a fixed bed stainless steel tubular reactor. The results showed that at a hydrogen/n-octane volume ratio of 1000, pressure of 0.6 MPa, temperature of 230 ℃ and LHSV of 3 h^-1, the conversion of n-octane, yield of liquid, hydrocracking rate and yield of iso-octane were 52.32%, 88.66%, 12.60%, 39.51%, respectively.

Quantitative determination of n-heptane and n-octane using terahertz time-domain spectroscopy with chemometrics methods

This paper introduces the terahertz time- domain spectroscopy （THz-TDS） used for the quantitative detection of n-heptane volume ratios in 41 n-heptane and n-octane mixtures with the concentration range of 0-100% at the intervals of 2.5%. Among 41 samples, 33 were used for calibration and the remaining 8 tbr validation. Models of chemometrics methods, including partial least squares （PLS） and back propagation-artificial neural network （BP-ANN）, were built between the THz- TDS and the n-heptane percentage. To evaluate the quality of the built models, we calculated the correlation coefficient （R） and root-mean-square errors （RMSE） of calibration and validation models. R and RMSE of two methods were close to 1 and 0 within acceptable levels, respectively, demonstrating that the combination of THz- TDS and chemometrics methods is a potential and promising tool for further quantitative detection of n- alkanes.

Precipitation of Heavy Organics (Asphaltenes) from Crude Oil Residue Using Binary Mixtures of n-Alkanes

Two solvent mixtures: n-pentane/n-hexane and n-heptane/n-octane at ten different percentage ratios were used to dissolve 2.5 g of vacuum distilled Anthan crude oil residue (500°C). The crude oil/n-alkane mixture in different conical flasks was stoppered, shaked mechanically and allowed to stand overnight. The resultant solution was subsequently filtered using a vacuum pump to afford the different weights of the residue (asphaltenes). The result of the weights of asphaltenes obtained at the different ratios of solvent mixtures showed that the highest amount of precipitate was obtained at 100% n-pentane solvent. Also there was a sharp increase in the amount of asphaltenes precipitated when the percentage ratio of n-pentane to n-hexane precipitant was 40:60 and when the ratio of n-heptane to n-octane precipitant was 30:70. A good understanding of the contribution of the different n-alkane solvents in the precipitation of asphaltenes is very necessary to flow assurance of crude oils in terms of solid precipitation.