Hydroisomerization of n-Hexadecane Over Nickel-Modified SAPO-11 Molecular Sieve-Supported NiWS Catalysts: Effects of Modification Methods.

The complexation-excessive impregnation modification method, which was original in this study, and the ion-exchange method and the in situ modification method were used to synthesize Ni-modified SAPO-11 molecular sieves. With the Ni-modified SAPO-11 samples as support, the corresponding NiWS-supported catalysts for the hydroisomerization of n-hexadecane were prepared. The effects of Ni-modification on SAPO-11 characteristics and the active phase were studied. The structure, morphology, and acidity of SAPO-11, as well as the interaction between active metals and support, the morphology, dispersibility, and stacking number of the active phase, were all changed by Ni-modification methods. The complexation-excessive impregnation modification method deleted a portion of Al from SAPO-11 molecular sieves while simultaneously integrating Ni into the skeletal structure of the surface layer of SAPO-11 molecular sieves, considerably enhancing the acidity of SAPO-11 molecular sieves. Furthermore, during dealumination, ethylenediaminetetraacetic acid generated more mesoporous structures and increased the mesoporous volume of SAPO-11 molecular sieves. Because the complexation-excessive impregnation modification method increased the amount of Ni in the surface framework of the SAPO-11 molecular sieve, it has weakened the interaction between the active phase and the support, improved the properties of the active phase, and greatly improved the hydroisomerization performance of NiW/NiSAPO-11. The yield of i-hexadecane of NiW/NiSAPO-11 increased by 39.3% when compared to NiW/NiSAPO-11. It presented a realistic approach for increasing the acidity of SAPO-11, reducing the interaction between active metals and support, and improving the active phase stacking problem.

Synthesis of Nickel In Situ Modified SAPO-11 Molecular Sieves and Hydroisomerization Performance of Their NiWS Supported Catalysts.

SAPO-11 molecular sieves were modified with different Ni contents by the in situ modification method. The Ni-modified SAPO-11 molecular sieves were used as the supports to prepare the corresponding NiW-supported catalysts for the hydroisomerization of n-hexadecane. The Ni-modified SAPO-11 and the corresponding NiW-supported catalysts were characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, NH3-temperature-programmed desorption, pyridine adsorbed infrared, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that Ni in situ modification preserved the crystal structure of SAPO-11; increased the BET specific surface area, mesopore volume, and medium and strong Brønsted acid amount of SAPO-11; and increased the stacking number of the active phase of the catalysts. 3Ni-SAPO-11 possessed the largest BET specific surface area, mesopore volume, and medium and strong Brønsted acid amount. NiW/3Ni-SAPO-11 possessed the highest dispersion of the active phase and the highest sulfidation degree of the active metals. The results of the hydroisomerization of n-hexadecane showed that Ni in situ modification improved the catalytic activity and selectivity of the catalysts for the hydroisomerization of n-hexadecane to varying degrees. Especially, NiW/3Ni-SAPO-11 had the highest catalytic activity and isomer selectivity, and the maximum yield of isomeric hexadecane could reach 71.18%.

Citric Acid-Treated Zeolite Y (CY)/Zeolite Beta Composites as Supports for Vacuum Gas Oil Hydrocracking Catalysts: High Yield Production of Highly-Aromatic Heavy Naphtha and Low-BMCI Value Tail Oil.

Citric acid-treated zeolite Y (CY) and zeolite beta were mechanically mixed to obtain composite zeolites (CY-Beta) with various zeolite beta contents. The composite zeolites were used as the acid components of hydrocracking catalyst supports. The physical and chemical properties of the supports and catalysts were analyzed by N2 adsorption-desorption, XRD, SEM, and NH3-TPD. The mechanical mixing of CY and zeolite beta does not destroy the textual properties of the original zeolites. However, the acidity of the composite zeolite does not fit the linearly calculated value of the two zeolites because some of the acid sites are covered or reacted with other acid sites during the mixing process. In addition, weak acid sites favor the high yield of tail oil with low BMCI value. Compared with the CY-based and beta-based catalysts, the conversion and light oil yield of the CY-Beta-based catalyst was increased. The conversion, light oil yield, and petrochemical yield of the Ni-W/20CY-Beta(20)/ASA catalyst are 78.15, 65.0, and 83.7%, respectively. The BMCI value of the tail oil is 4.7, and the aromatic potential content (APC) of heavy naphtha (boiling point 65-177°C) is 42%. The 1,500 h pilot plant test of Ni-W/20CY-Beta(20)/ASA at 350°C, 7.0 MPa, 2.0 h-1 LHSV, and 800 H2/oil (v/v) shows that the activity remains stable during the 1,500 h evaluation. The heavy naphtha (APC about 41.0) yield of 41.2 illustrates that the catalyst has the ability to aromatize and cyclize the light fractions. The yield of diesel is about 25% with a cetane index (CI) of 59.2; the frozen point is lower than -45°C, and the cold filter plugging point is -35°C, demonstrating the isomerization performance for middle distillations. The yield of tail oil is 14.9% with a BMCI of 4.4, showing the high hydrogenation performance of the catalyst to transform the un-cracked tail oil to saturated hydrocarbon in order to reduce the BMCI value.

Characterization of phenolic compounds in coal tar by gas chromatography/negative-ion atmospheric pressure chemical ionization mass spectrometry.

RATIONALE: Phenolic compounds are commonly found in fossel fuels and bio-oils, and have a detrimental effect on the chemical stability of the fuels. A selective analytical method is needed to characterize the phenolic compounds in complex hydrocarbon mixtures. METHODS: Gas chromatography/atmospheric pressure chemical ionization mass spectrometry (GC/APCI-MS) was used to characterize the phenolic compounds in a low-temperature coal tar and its narrow distillate fractions. RESULTS: Negative-ion APCI selectively ionized phenolic compounds in the coal tar. The [M-H](-) and [M-H + O](-) ions were derived from monohydric phenols, while [M-H](-) , [M-2H](-) , and [M-2H + O](-) were from benzenediols. Monohydric phenolic compounds with 1-4 aromatic rings and some dihydric phenolic compounds were identified. The results from GC/APCI-MS were validated by those from negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICRMS). CONCLUSIONS: Negative-ion GC/APCI-MS was proposed and successfully used to characterize phenolic compounds in coal tar samples. This technique can potentially be used for the characterization of phenolic compounds in other complex hydrocarbon systems. Copyright © 2016 John Wiley & Sons, Ltd.