Xu Chunming

Effects of Light Rare Earth on Acidity and Catalytic Performance of HZSM-5 Zeolite for Catalytic Cracking of Butane to Light Olefins

Abstract The effects of rare earth (RE) on the structure, acidity, and catalytic performance of HZSM-5 zeolite were investigated. A series of RE/HZSM-5 catalysts, containing 7.54% RE (RE = La, Ce, Pr, Nd, Sm, Eu or Gd), were prepared by the impregnation of the ZSM-5 type zeolites (Si/Al =64:1) with the corresponding RE nitrate aqueous solutions. The catalysts were characterized by means of FT-IR, UV-Vis, NH 3 -TPD, and IR spectroscopy of adsorbed pyridine. The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor. The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins, especially to propylene, thus increasing the total yield of olefins in the catalytic cracking of butane. Among the RE-modified HZSM-5 samples, Ce/HZSM-5 gave the highest yield of total olefins, and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600°C. The presence of rare earth metal on the HZSM-5 sample, not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type, that is, the ratio of L/B (Lewis acid/Bronsted acid), but also altered the basic properties of it, which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.

Engineering metal–organic frameworks immobilize gold catalysts for highly efficient one-pot synthesis of propargylamines

Engineering metal–organic frameworks (MOF) for heterogeneous catalysts have been of extreme interest since they could bridge the gap between homogeneous and heterogeneous catalysis. We have designed and synthesized gold functionalized IRMOF-3 catalysts by post-covalent modification (PM) and one-pot (OP) synthesis methods. The gold functionalized IRMOF-3 catalysts provide an efficient, economic, and novel route for the one-pot synthesis of structurally divergent propargylamines via three component coupling of alkyne, amine, and aldehyde (A3) without any additives or an inert atmosphere. The catalysts were characterized in depth to understand their structure–property relationship. It was shown that the 4.6%Au/IRMOF-3 catalyst, prepared by the PM method, contains a fraction of cationic gold (Au3+/Au0 = 0.2), which shows much higher catalytic activity than that of 3.2% or 0.6%Au/IRMOF-3 prepared by OP method, although the former exhibits much lower crystallinity than the latter two catalysts. Notably, the catalytic activity of the Au/IRMOF-3 catalysts could be significantly enhanced at a moderate reaction temperature (150 °C). All the Au/IRMOF-3 catalysts can be easily recycled and used repetitively at least 5 times, especially the catalysts prepared by the OP method, which showed no drop in activity for the successive 5 uses. These features render the catalysts particularly attractive in the practice of propargylamines synthesis in an environmentally friendly manner.

Catalysis by metal–organic frameworks: proline and gold functionalized MOFs for the aldol and three-component coupling reactions

Translation of homogeneous catalysis into heterogeneous catalysis is a promising solution to green and sustainable development in the chemical industry. Recent research has shown that metal–organic frameworks (MOFs) could bridge the gap between homogeneous and heterogeneous catalysis. We successfully prepared for the first time a novel homochiral Zn-containing MOF referred to as CUP-1 based on the mixed linkers of 2-aminoterephthalic acid and L-lactic acid in a one-pot synthesis. The free NH2 group in the homochiral framework of CUP-1, similar to the well known achiral IRMOF-3, is potentially available for undergoing a variety of organic transformations, as demonstrated by choosing the auxiliary chiral L-proline and nano gold to functionalize MOFs with postsynthetic modification and one-pot synthesis strategies. IRMOF-3, CUP-1 and their functionalized samples were in-depth characterized by X-ray diffraction, N2 adsorption–desorption, optical and transmission electron microscopy, infrared spectroscopy, solid state nuclear magnetic resonance, thermogravimetric and differential thermal analysis, and temperature-programmed reduction. L-Proline functionalized IRMOF-3 shows fair to excellent enantioselectivity (up to 98%) in asymmetrical aldol reactions of aldehydes and acetone with higher turnover numbers and catalytic stabilities than the homogeneous counterpart. The gold functionalized CUP-1 catalysts are found to be highly active, stable and reusable for the three-component coupling reactions of aldehydes, alkynes and amines. This work provides general methods to functionalize MOFs with the active ligand and metal nanoparticles for fabrication of highly efficient MOF-based heterogeneous catalysts.

CeO2-supported vanadium oxide catalysts for soot oxidation: the roles of molecular structure and nanometer effect

The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis, and the nanometer CeO2- supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings (atomic ratios: 100V/Ce=0.1, 1, 4, 10, and 20) were prepared by an incipient-wetness impregnation method. Spectroscopic techniques (XRD, FT-IR, Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts. The results showed that the structures of CeO2-supported vanadium oxide catalysts depended on the vanadium loading. Isolated mono-vanadate species were present on the surface of catalysts at low V loading, and poly-vanadate species existed at medium V loading, but CeVO4 crystallites were formed at high V loading (V10 and V20). The catalytic performances of these catalysts for diesel soot oxidation were investigated with temperature-programmed oxidation reaction (TPO). For soot oxidation, the poly-vanadate species were mainly active sites in ordinary CeO2-supported vanadyl catalysts, but nanometer CeO2 was mainly active components in nanometer CeO2-supported vanadium oxide catalysts. Due to the nanometer effect and the good contact between the catalyst and the soot, nanometer CeO2 exhibited a very high catalytic activity for soot combustion.

Separation and characterization of petroleum asphaltene fractions by ESI FT-ICR MS and UV-vis spectrometer

Using heptane, toluene, and tetrahydrofuran (THF) as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both asphaltene and its fractions were analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The application of UV-vis spectrometer in characterizing asphaltene composition and measuring asphaltene concentration was discussed. About 11.9 wt% asphaltene components adsorbed permanently on silica gel in the extrography column after excessive elution with various solvents. In negative FT-ICR MS, the mass spectra show that acidic and neutral nitrogen-containing compounds such as N1 and N1S1 mainly existe in the first three less polar fractions, while oxygen-containing compounds such as O2, O2S, O2S2, O3, and O4 show high relative abundance in more polar fractions. These results suggest oxygen-containing compounds have stronger adsorption ability with silica gel. It was observed that the double bond equivalence (DBE) distribution of N1 class species in the fractions shifted to higher values while the carbon number shifted to smaller numbers as polarity of fractions increased. This indicates that acidic and neutral N1 compounds with longer carbon chain and less aromaticity have less polarity compared with those with shorter carbon chain and stronger aromaticity. UV-vis absorbance indicats that fractions containing the most aromatic and most polar asphaltene have better absorbance at long wavelength, while the fractions that consist of least aromatic and least polar asphatlenes show high absorbance at short wavelength.

Thermal transformation of acid compounds in high TAN crude oil

The Liaohe crude oil with high total acid number (TAN) was subjected to thermal reaction at 300 °C to 500 °C. Reaction products were collected and analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) to determine acid compounds in the crude oil. The double-bond equivalence (DBE) versus carbon number was used to characterize the oxygenated components in the feed and reaction products. The O2 class which mainly corresponds to naphthenic acids decarboxylated at 350–400 °C, resulting in a sharply decrease in TAN. Phenols (O1 class) are more thermally stable than carboxylic acids. Carboxylic acids were also thermally cracked into smaller molecular size acids, evidenced by the presence of acetic acid, propanoic acid, and butyric acid in the liquid product. These small acid species are strong acids likely responsible for corrosion problems in refineries.

Effects of experimental conditions on the molecular composition of maltenes and asphaltenes derived from oilsands bitumen: Characterized by negative-ion ESI FT-ICR MS

A vacuum topped Canadian oilsands bitumen (VTB) was subjected to solvent precipitation and subsequently characterized by elemental analysis, gel permeation chromatograph (GPC), 1H-NMR spectroscopy and negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Effects of experimental conditions such as solvent types (n-C5, n-C6, and n-C7), solvent purity, and solvent washing time on asphaltenes yields, bulk composition, and molecular composition of detectable heteroatom compounds in ESI source were determined. Elemental nitrogen and sulfur were enriched in asphaltenes while elemental oxygen had comparable content in maltenes and asphaltenes. Molecular composition of asphaltenes varies with separation conditions. The N1 and O1 species identified by ESI FT-ICR MS were enriched in maltenes. The O2 species exhibited two different double bond equivalents (DBE) distributions and solubility in normal paraffin solvents, indicating two types of molecular structures. Multi oxygen atom containing compounds mainly detected in asphaltenes. Compound class distributions are similar for maltenes derived from n-C5, n-C6, and n-C7, as well as for asphaltenes. The cyclic paraffin impurities in normal paraffin solvents had a significant influence on asphaltenes yields and heteroatom molecular composition. A portion of neutral N1 species and acidic O2 species adsorbed on asphaltenes could be dissolved by increasing washing time. Cautions should be exercised when interpreting the properties and composition of asphaltenes obtained with different experimental conditions.

Synthesis of LaxK1–xCoO3 nanorod and their catalytic performances for CO oxidation

Abstract A series of LaxK1–xCoO3 nanorod oxides with perovskite structure were synthesized by sol-gel method using polyvinyl alcohol (PVA) as additive. These perovskite-type complex oxide catalysts were characterized by the techniques of X-ray diffraction (XRD), infrared (IR), Brumauer-Emmett-Teller (BET) and scanning electron microscopy (SEM). And the results showed that nanorods of La1–xKxCoO3 perovskite-type complex oxides were fabricated by sol-gel method when the mass concentration of PVA was 4% and the calcined temperature kept at 700 °C for 4 h. The catalytic results of CO oxidation showed that the LaxK1–xCoO3 catalysts had high activity. LaCoO3 nanorods exposed more {110} plane than LaCoO3 nanoparticles, which was beneficial to the catalytic oxidation of CO. LaCoO3 nanorods had the best catalytic performance for the oxidation of CO. At 200 °C, the CO conversion could reach 100%.

Properties, compositions and structure characteristics of Kazakhstan and Russian Vacuum Residua

Kazakhstan vacuum residue (KAZVR) and Russia vacuum residue (RUSVR) were respectively cut into a number of narrow cuts and non-extractable end-cut by supercritical fluid extraction and fractionation (SFEF). The properties distribution and SARA compositions of the fractions were analyzed, structure parameters and structure configurations were determined by means of the modified BL method based on 13C-NMR and 1H-NMR data. The results show uneven enriching of contaminants in heavier fractions and much complex structure for end-cuts and removing end-cuts from residua will greatly favor further upgrading. The results would help detailed understanding of KAZVR and RUSVR and their processing adaptability.

Multilayer membranes based on ceramic materials —Sol-gel synthesis, characterization and membrane performance

In nearly all chemical and petrochemical systems, separation of products generally accounts from more than 50% of the capital cost and the greatest part of the energy consumption. It is generally believed that membrane systems can offer benefits in both reducing the energy consumption of the separation stages and lowering the capital expenditure (CAPEX). Microporous ceramic membranes have the potential to overcome the limitation in polymer membranes operation, which has been the subject of a large amount of research worldwide in the last two decades. And most of the research has aimed at the production of the asymmetric multilayered membrane based on amorphous oxides by sol-gel techniques. The paper is to give an overview of publications on ceramic membranes, including less common materials of titania, zirconia, which can be used for pervaporation in corrosive media. Commercially available microporous membranes based on these membrane materials and the membrane economics are also summarized.