A highly shape-selective catalyst with a relatively long lifetime for methanol aromatization (MTA reaction) was prepared through finely adjusting the pore-opening size and the acidic properties of HZSM-5, depending on the combination of liquid silica deposition with polysiloxane and Zn & Mg loading. XRD, 27Al MAS NMR, TEM, BET, NH3-TPD, Py-IR, TG, GC-MS and probe-molecule reactions were used to reveal the relationship between the modification methods and the catalytic performance. The results showed that silica deposition significantly enhanced the p-xylene (p-X) selectivity in xylene isomers and restrained the formation of larger C9+ aromatic molecules, owing to the narrowing of the pore-openings and the elimination of external acid sites. Further Zn-loading effectively improved the MTA activity of Si-HZSM-5 due to the promotion of the internal Zn-Lewis acid sites with increased density to the dehydrogenation of the intermediates in this reaction. However, the Zn–Si-HZSM-5 catalyst showed poor catalytic stability, which is mainly attributed to the micropore blockage (invalidation of internal acid sites) caused by coke deposition over the strong acid sites inside the channels, which showed strong diffusion-restriction on aromatic molecules at their openings. Fortunately, 1.5% Mg modification selectively reduced the density of the strong acid sites in the channels of Zn–Si-HZSM-5, effectively improving its catalytic stability as the reduction of acidic strength suppressed polyaromatic (coke components) formation at the channel intersections. Moreover, MgO also slightly enhanced the porous shape-selectivity together with the Zn species. As a result, more than 98.9% para-selectivity of xylene and 20.1–21.2% p-X yield were obtained in the 12 h MTA reaction over the highly shape-selective Mg–Zn–Si-HZSM-5 catalyst.

A new transfer hydrogenation of 2-nitrotoluene with methanol to 2-methylaniline was successfully implemented. The transfer hydrogenation of 2-nitrotoluene with methanol showed much faster rate than its hydrogenation with hydrogen over X zeolites. Based on the reaction results over different modified X zeolites and activated carbon, a radical mechanism was proposed.

A promising fluorinated NiO/Al2O3 catalyst for synthesizing trifluoroethylene through the catalytic dehydrofluorination of CF3CFH2 was prepared, and the relationship between the Lewis acid sites and activity was investigated. 20.1% conversion of CF3CFH2 was observed, and the selectivity to trifluoroethylene was observed to be 99% at 430 °C after 100 h.

A variety of the modified X zeolites were used to catalyse the oxidative dehydrogenation of ethylbenzene to styrene with CO2 for the first time. The results showed that X zeolites modified by alkali metal cation exchange, such as KX and CsX, exhibited high catalytic activity and selectivity with a good stability. The reaction temperature 818 K over the modified X zeolites is much less than 923 K over the current metallic oxide catalyst. Moreover, the co-catalysis between acid sites and base sites over the modified X zeolite was indispensable in this reaction, and the basicity of the catalyst greatly determined the selectivity of styrene. The participation of CO2 in the co-catalysis process improves the conversion of ethylbenzene and the selectivity of styrene.

Hierarchical ZSM-5 nanosheets with intracrystal mesopores and honeycomb morphology have been synthesised by seed-inducing via a hydrothermal route in the presence of hexadecyl trimethyl ammonium bromide (CTAB) as the second template.

A variety of cesium supported catalysts with amorphous SiO2 as a carrier were prepared by vacuum impregnation and ultrasonic impregnation methods, which were used for the synthesis of methyl acrylate by aldol condensation of methyl acetate and formaldehyde. The as-prepared catalysts were characterized by XRD, N2 adsorption–desorption, NH3-TPD, CO2-TPD, XPS, ICP and TG. The results indicated that the bifunctional Cs–La–Sb/SiO2 showed a high conversion of methyl acetate as well as a high yield of methyl acrylate, which was attributed to the weak acid–base sites and the formation of basic Cs–O–Si species with the addition of antimony and lanthanum, respectively. Furthermore, Cs–La–Sb/SiO2-(V) prepared by vacuum impregnation showed a high initial catalytic activity, but its activity sharply decreased due to the loss of active species. Comparatively, Cs–La–Sb/SiO2-(U) prepared by ultrasonic impregnation showed a good stability owing to the cavitation effect of ultrasonic waves. The conversion of methyl acetate and yield of methyl acrylate remained above 20% and 9.0% (based on methyl acetate) for 100 h without obvious deactivation. Moreover, carbon deposition was the main factor for the deactivation of Cs–La–Sb/SiO2-(U), and the coked catalyst could be regenerated by calcination in air.

Two typical shape-selective HZSM-5 catalysts were prepared by silica deposition and La2O3 loading, respectively. They were characterized by means of XRD, BET, NH3-TPD and Py-IR and were tested by alkylation of toluene with methanol. The deactivation mechanism of these catalysts in the alkylation was studied in detail by using TG, BET, NH3-TPD, Py-IR, and soluble coke extraction/GC-MS. The results indicated that the invalidation of internal acid sites deactivated both catalysts which have different deactivation processes. Concretely, the fast deactivation of SiO2-HZSM-5 is due to the microporous blockage caused by soluble coke, which is composed of multi-methylbenzenes, polyaromatics and large olefins. Whereas, the invalidation of the internal acid sites on La2O3-HZSM-5 results from the accumulation of multi-methylbenzenes, naphthalenes, and large aliphatic compounds inside ZSM-5 channels and the subsequent micropore blocking by insoluble coke.

The aromatization of methanol over parent HZSM-5 and the modified NiO-HZSM-5 in a fixed-bed reactor was investigated under CO2 and N2 flow. The as-prepared catalysts were characterized by H2-TPR, XRD, BET, NH3-TPD, CO2-TPD and probe-molecule reaction. Compared with parent HZSM-5 in CO2 or N2 flow and with NiO-HZSM-5 in N2 flow, NiO-HZSM-5 showed greatly improved aromatization activity and BTX (benzene, toluene and xylene) yield in CO2 atmosphere. This is attributed to the cooperation of acid sites with the activated CO2 (over NiO species), which not only can effectively promote dehydrogenation of alkanes to form olefin intermediates, but also can accelerate dehydrogenation in the conversion of olefin intermediates to aromatics. In particular, an optimized NiO-HZSM-5 with 2.0 wt% NiO loading showed 50.1% total aromatic yield and 35.5% BTX yield in CO2 atmosphere. It also showed high catalytic stability resulting from the restriction of coking due to its acidity, carbonaceous elimination by the activated CO2-reacting deposited coke, and the suppressed reduction of highly active NiO species by activated CO2.

The external surface of HZSM-5 zeolite was passivated by liquid siliceous deposition and by acidic sites poisoning with lepidine, respectively. Then methanol-to-hydrocarbons (MTH) reaction was investigated over the above as-prepared catalysts and the dissoluble coke on these used catalysts was analyzed by GC-MS, to study the role of the external surface of HZSM-5 in the catalytic reaction. Comparison with the experimental results based on parent ZSM-5 showed that the product distribution of MTH reaction was obviously influenced by the external surface. Evidences were listed as follows: (1) the final product on parent HZSM-5 showed higher aromatic selectivity, lower olefin selectivity, lower ratio of C2/C3+ aliphatics and higher ratio of C3/C4+ aliphatics than the reaction mixture produced by the sole catalysis of acidic sites in HZSM-5 channel; (2) a little of pentamethylbenzene and hexamethylbenzene in the product on parent HZSM-5, was produced via multi-methylation of methylbenzene on the external surface. The above conclusion may also be suitable for MTH reaction over other zeolites with 10-ring channel.In the conversion of methanol to hydrocarbons over HZSM-5, the product distribution is obviously influenced by the external surface of this zeolite.Download full-size image

Biodegradation parameters and kinetic characteristics for pre-treating waste strains of Klebsiella pneumoniae were studied in laboratory scale with an insulated reactor by an innovative technique, autothermal thermophilic aerobic digestion (ATAD). Based on an Arrhenius-type equation, an empirical model was developed to correlate the removal of total suspended solid (TSS) with the initial TSS concentration, influent reaction temperature, aeration rate and stirring rate. The reaction temperatures of the ATAD system could be raised from the ambient temperatures of 25 °C to a maximum temperature of 65 °C. The exponentials for the initial TSS concentration, aeration rate and stirring rate were 1.579, −0.8175 and −0.6549, respectively, and the apparent activation energy was 6.8774 kJ·mol−1. The correlation coefficient for the pre-exponential factor was 0.9223. The TSS removal efficiency predicted by the model was validated with an actual test, showing a maximum relative deviation of 10.79%. The new model has a good practicability.

•Novel and facile fluorinating agent CF3SO3H is used to fluorinate sulfonic polystyrene resin.•The prepared CF3SO2-resin exhibits high stability and acid strength.•The prepared CF3SO2-resin performs well as solid catalyst in the Friedel–Crafts reaction and esterification.A novel fluorination method derived from CF3SO3H was employed to the polystyrene sulfonic acid resin, to enhance its acid strength and stability. The as-prepared CF3SO2-resin was characterized by FT-IR, XPS, 31P MAS NMR, and chemical titration, and its catalytic performance was tested. It was found that CF3SO2-resin exhibited higher selectivity to benzyltoluene in the Friedel–Crafts alkylation of toluene with benzyl alcohol, excellent catalytic activity with 96% conversion and a good recyclability over seven times in esterification of 1, 6-hexanedioic acid with 2-ethylhexanol.A mild and facile synthesis of fluorinated sulfonated polystyrene chloridized resin from CF3SO3H has been reported to enhance the stability and acid strength of parent resin.Download high-res image (202KB)Download full-size image

A highly shape-selective catalyst with a relatively long lifetime for methanol aromatization (MTA reaction) was prepared through finely adjusting the pore-opening size and the acidic properties of HZSM-5, depending on the combination of liquid silica deposition with polysiloxane and Zn & Mg loading. XRD, 27Al MAS NMR, TEM, BET, NH3-TPD, Py-IR, TG, GC-MS and probe-molecule reactions were used to reveal the relationship between the modification methods and the catalytic performance. The results showed that silica deposition significantly enhanced the p-xylene (p-X) selectivity in xylene isomers and restrained the formation of larger C9+ aromatic molecules, owing to the narrowing of the pore-openings and the elimination of external acid sites. Further Zn-loading effectively improved the MTA activity of Si-HZSM-5 due to the promotion of the internal Zn-Lewis acid sites with increased density to the dehydrogenation of the intermediates in this reaction. However, the Zn–Si-HZSM-5 catalyst showed poor catalytic stability, which is mainly attributed to the micropore blockage (invalidation of internal acid sites) caused by coke deposition over the strong acid sites inside the channels, which showed strong diffusion-restriction on aromatic molecules at their openings. Fortunately, 1.5% Mg modification selectively reduced the density of the strong acid sites in the channels of Zn–Si-HZSM-5, effectively improving its catalytic stability as the reduction of acidic strength suppressed polyaromatic (coke components) formation at the channel intersections. Moreover, MgO also slightly enhanced the porous shape-selectivity together with the Zn species. As a result, more than 98.9% para-selectivity of xylene and 20.1–21.2% p-X yield were obtained in the 12 h MTA reaction over the highly shape-selective Mg–Zn–Si-HZSM-5 catalyst.

A promising fluorinated NiO/Al2O3 catalyst for synthesizing trifluoroethylene through the catalytic dehydrofluorination of CF3CFH2 was prepared, and the relationship between the Lewis acid sites and activity was investigated. 20.1% conversion of CF3CFH2 was observed, and the selectivity to trifluoroethylene was observed to be 99% at 430 °C after 100 h.

Two typical shape-selective HZSM-5 catalysts were prepared by silica deposition and La2O3 loading, respectively. They were characterized by means of XRD, BET, NH3-TPD and Py-IR and were tested by alkylation of toluene with methanol. The deactivation mechanism of these catalysts in the alkylation was studied in detail by using TG, BET, NH3-TPD, Py-IR, and soluble coke extraction/GC-MS. The results indicated that the invalidation of internal acid sites deactivated both catalysts which have different deactivation processes. Concretely, the fast deactivation of SiO2-HZSM-5 is due to the microporous blockage caused by soluble coke, which is composed of multi-methylbenzenes, polyaromatics and large olefins. Whereas, the invalidation of the internal acid sites on La2O3-HZSM-5 results from the accumulation of multi-methylbenzenes, naphthalenes, and large aliphatic compounds inside ZSM-5 channels and the subsequent micropore blocking by insoluble coke.