Cu/ZnO/Al2O3 (CZA) catalysts were prepared by two-step precipitation method with the assistance of the surfactant, tetraethylammonium hydroxide (TEAH) or polyethylene glycol (PEG), and evaluated in methanol synthesis from syngas. Effects of input amount of the surfactant and accelerated thermally induced deactivation (ATD) on the activity of the catalyst were investigated under the reaction conditions of 230 °C, 5 MPa, gas hourly space velocity (GHSV) of 10,000 h−1 and the syngas composition of CO/CO2/H2/N2 (volume ratio) = 15:5:70:10. Among the catalysts investigated, 2T-CZA catalyst, prepared with addition of 2 wt.% TEAH in the course of the coprecipitation of Cu2+ and Zn2+, exhibited better catalytic performance due to its smaller crystallite size of Cu and higher Cu surface area, over which methanol space-time yield (STY) was 1.26 times as heavy as that over blank CZA catalyst, prepared without any surfactant's assistance, and 1.25 times as that over commercially famous CX catalyst for methanol synthesis from syngas in China. Meanwhile, 2T-CZA catalyst showed satisfactory thermal stability, in which methanol STY decreased by only 5.2% because of growing up of crystallite size of Cu and decrease in the number of surface Cu atoms after the ATD test to be conducted in situ at 350 °C for 20 h in syngas.Graphical abstractCatalytic performance over different CZA catalysts before and after the accelerated thermally induced deactivation (ATD) test under the reaction conditions of 230 °C, 5 MPa, GHSV of 10,000 h −1, 1 mL catalyst and syngas composition of CO:CO2:H2:N2 (volume ratio) = 15:5:70:10.Highlights► Cu/ZnO/Al2O3 (CZA) catalyst was prepared by two-step precipitation method. ► The 2T-CZA catalyst showed better catalytic performance. ► Cu0 is main active site in methanol synthesis from syngas over CZA catalyst. ► Smaller crystallite size of Cu and higher Cu specific surface area are favorable. ► The slight drop of catalytic activity is due to the decrease in surface Cu atoms.

A sensitive and reliable method was developed for the determination of volatile components emitted from cut tobacco processing using thermal desorption (TD) followed by gas chromatography–mass spectrometry (GC–MS). In the work, to obtain the optimal sorbent, three commercial sorbents were compared in terms of adsorption efficiency. The carbotrap 349 was found to have the best performance. The desorption conditions were also studied. Validation of the TD-GC–MS method showed good sensibility, linearity and precision. Limits of detection ranges were from 0.20 to 3.6 ng. Calibration curves were obtained by plotting peak area versus concentration and the correlation coefficients relating to linearity were at least 0.9984. The analysis was reproducible, with relative standard deviation (n=8) within 6.5%. The target compound breakthrough examination showed no significant losses when about 1500 ng standards were prepared. In order to evaluate the performance of the analytical method in the volatile constituents of cut tobacco, samples were taken in industrial areas of cut tobacco processing. Recoveries ranged from 85.1% to 110% for all the compounds and good precision had been reached (RSD<13.3). The results proved that TD-GC–MS was a simple, rapid and accurate method for the analysis of volatile compounds emitted from cut tobacco drying step.Highlights► The sampling device is newly developed and introduced in tobacco industry. ► Three tubes filled with different sorbent materials are compared. ► Most adequate instrumental conditions for thermal desorption are studied. ► Safe sampling volume and breakthrough data are verified. ► The method is fit for the analysis of emissions during the cut tobacco drying process.

A mathematical model of a multi-bed adiabatic reactor for the Methanol-to-Olefin (MTO) process is established based on a lumping kinetic equation with SAPO-34 catalyst. Influences of different process conditions are investigated. Temperature plays a more important role in governing simulation results than other factors do. The decrease of methanol conversion resulting from catalyst deactivation could be reflected by changing the model parameter.

Hierarchical core/shell structures with mordenite (MOR) core and continuous ZSM-5 (MFI) shell were successfully fabricated by a novel two-step procedure. The mordenite core crystals were ca. 90% enwrapped by polycrystalline ZSM-5 shells. It was achieved by pre-treatment of mordenite cores in organic amine solution and secondary growth of ZSM-5 shell on the modified mordenite crystals. The final products were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), N2 adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods to determine the morphologies and structural properties of the core/shell nanostructures. Pre-treatment step was a determining strategy during the synthesis. The growth kinetics of the polycrystalline ZSM-5 shell was further investigated by analysis of the products obtained with different secondary crystallization time. Tiny particles appeared on the mordenite surfaces in the early stage and developed into continuous polycrystalline ZSM-5 films finally, which underwent the so-called “from point to surface” growth process. On the basis of systematic investigation into the formed structures and growth process, a plausible formation mechanism for these particular core/shell composites was proposed. The flexible nature of current approach would allow the synthesis of other couples of core/shell zeolite overgrowth despite the structural or chemical incompatibilities.

Cu/SiO2 catalysts prepared by a convenient and efficient method using the urea hydrolysis deposition-precipitation (UHDP) technique have been proposed focusing on the effect of copper loading. The texture, structure and composition are systematically characterized by ICP, FT-IR, N2-physisorption, N2O chemisorption, TPR, XRD and XPS. The formation of copper phyllosilicate is observed in Cu/SiO2 catalyst by adopting UHDP method, and the amount of copper phyllosilicate is related to copper loading. It is found the structure properties and catalytic performance is profoundly affected by the amount of copper phyllosilicate. The excellent catalytic activity is attributed to the synergetic effect between Cu0 and Cu+. DMO conversion and EG selectivity are determined by the amount of Cu0 and Cu+, respectively. The proper copper loading (30 wt%) provides with the highest ratio of Cu+/Cu0, giving rise to the highest EG yield of 95% under the reaction conditions of p = 2.0 MPa, T = 473 K, H2/DMO = 80 and LHSV = 1.0 h−1.

The intrinsic reaction kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts was studied in the quartz pipe-reactor under ordinary pressure with the temperature ranging from 913.15 to 973.15 K and the space velocity from 700 to 2100 ml/(g·h). The Langmuir-Hinshelwood model was chosen to describe the intrinsic kinetics while Levenberg-Marquardt method was selected to determine the parameters in the kinetic model. Statistical test and residual error distribution diagrams showed that experimental data were in good agreement with calculated data, and Langmuir-Hinshelwood model was suitable for the description of the intrinsic kinetics of methane aromatization under the reaction conditions discussed in this article.

AbstractA three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows: diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger (ϕ 38×2 mm), and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.

Thermax 700 thermo gravimetric analysis (TGA) instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins (MTO) process with SAPO-34 catalyst. By the use of a special sample basket, the TGA instrument can be viewed as a plug flow fixed-bed reactor, while the weight change of SAPO-34 during reaction can be recorded online. Kinetic data are acquired in the temperature range of 648.2-748.2 K and space velocities of 7.08–35.91 h−1 (WHSV). Catalyst activity is expressed with average coke content, and selectivity for different products is related as a function of coke content and temperature. Methane is also introduced into the lumping kinetic model, and power exponent function with first-order reaction is adopted for model deduction. Exponential function is tested to give the best fit for catalyst activity and product selectivity with the highest correlation coefficient. The nicely agreed results between experimental and calculated data suggest that the overall kinetic model would be meaningful in both product distribution prediction and reactor simulation.