Hydrothermal synthesis of nanosized ZSM-22 and their use in the catalytic conversion of methanol

ZSM‐22 zeolite with different crystal lengths was prepared using a modified hydrothermal method. Rotation speed, Si/Al molar ratio and co‐solvent have important effects on the crystal size of ZSM‐22. The nanosized zeolite samples were characterized by X‐ray diffraction, X‐ray fluorescence, nitrogen adsorption, scanning electron microscopy, temperature‐programmed desorption of am‐monia and solid state nuclear magnetic resonance. The catalytic performance of nanosized ZSM‐22 was tested using the conversion of methanol. Compared to conventional ZSM‐22, the nanosized ZSM‐22 zeolite exhibited superior selectivity to ethylene and aromatics and lower selectivity to propylene. Stability against deactivation was clearly shown by the nanosized ZSM‐22 zeolite. A higher external surface area and smaller particle size make this nanosized ZSM‐22 zeolite attractive for catalytic applications.

STUDIES ON THE ALCOHOL CHAIN GROWTH AND INFLUENCE OF COBALT ADDITIVE

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Zn–Ca–Al mixed oxide as efficient catalyst for synthesis of propylene carbonate from urea and 1,2-propylene glycol

A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.

Kinetics of esterification of methanol and acetic acid with mineral homogeneous acid catalyst

In this work, esterification of acetic acid and methanol to synthesize methyl acetate in a batch stirred reactor is studied in the temperature range of 305.15–333.15 K. Sulfuric acid is used as the homogeneous catalyst with concentrations ranging from 0.0633 mol·L-1to 0.3268 mol·L-1. The feed molar ratio of acetic acid to methanol is varied from 1:1 to 1:4. The influences of temperature, catalyst concentration and reactant concentration on the reaction rate are investigated. A second order kinetic rate equation is used to correlate the experimental data. The forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot.The developed kinetic model is compared with the models in literature. The developed kinetic equation is useful for the simulation of reactive distillation column for the synthesis of methyl acetate.

Modeling of a Reverse Flow Reactor for Methanol Synthesis Modeling of a Reverse Flow Reactor for Methanol Synthesis

An accurate one-dimensional, heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall, and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented. Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation. Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained. The model was found to closely predict the reactor performance under a wide range of operating conditions, such as carbon oxide concentrations, volumetric flow rate, and cyclic period.

Synthesis of Biodiesel Using ZrO_2 Polycrystalline Ceramic Foam Catalyst in a Tubular Reactor

With the help of the ceramic foam research efforts and preparation techniques, the ZrO2 polycrystalline ceramic foam catalyst was synthesized, and its characteristics, including the crystal structure, the phase composition, the acid–base properties, and the microstructure, were analyzed by XRD, SEM, Py-IR, and BET techniques. The performance of the ZrO2 polycrystalline ceramic foam catalyst in a tubular reactor was investigated via biodiesel synthesis using S. wilsoniana oil and methanol. The effects of reaction conditions(i.e., reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil) on transesterification efficiency were investigated, and the reaction conditions were optimized using RSM. The optimum reaction temperature, reaction pressure, and volume ratio of methanol to S. wilsoniana oil were determined to be 290 ℃, 10 MPa, and 4:1, respectively. Under this condition, the FAME content in the product oil reached 98.38%. The performance of the ZrO2 polycrystalline ceramic foam catalyst synthesized in this work for biodiesel synthesis from S. wilsoniana oil with a moisture content of 7.1% and an acid value of 130.697 mg KOH/g was examined, and the FAME content in the product oil was found to be 93% and 97.67%, respectively. The FAME content in the product oil exceeded 97% after five consecutive cycles(12 h per cycle of use) of the catalyst. The proposed catalyst represents a new type of solid catalyst with excellent acid resistance, water resistance, esterification efficiency, and catalytic stability.

Silicoaluminophosphate molecular sieve DNL-6: Synthesis with a novel template, N,N'-dimethylethylenediamine, and its catalytic application

DNL-6, a silicoaluminophosphate（SAPO） molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent（SDA）, N,N＇-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6 s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning（MAS） nuclear magnetic resonance（13 C, 29 Si, 27 Al, 31 P, and 27 Al multiple-quantum（MQ）） was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals（about 4.4 SDAs per α-cage）, which was the reason for the formation of DNL-6 with an ultrahigh Si content（36.4% Si per mole）. Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.

Dynamic Kinetics of Methanol Synthesis over a Commercial Copper-Based Catalyst

Adsorption, surface reaction and process dynamics on the surface of a commercial copper-based catalyst for methanol synthesis from CO/CO2/H2 were systematically studied by means of temperature programmed desorption (TPD), temperature programmed surface reaction (TPSR), in-situ Fourier transform-inferred spec-troscopy(FTIR) and stimulus-response techniques. As a part of results, an elementary step sequence was suggested and a group of ordinary differential equations (ODEs) for describing transient conversations relevant to all species on the catalyst surface and in the gas phase in a micro-fixed-bed reactor was derived. The values of the parameters referred to dynamic kinetics were estimated by fitting the solution of the ODEs with the transient response data obtained by the stimulus-response technique with a FTIR analyzer as an on-line detector.