mohammadhassan peyrovi

With the aim of eliminating toluene as volatile organic compound, a collection of Pt-(Sn/Re)-HZSM-5/HMS catalysts with different weight percent of Sn/Re have been synthesized. Also, the catalytic performances of the prepared catalysts were compared to obtain the best activity and CO2 and CO selectivity versus various catalyst weight percent, temperature (200-500 °C) and time on stream (1-65 h). The results show that incorporation of Sn and Re into Pt-HZSM-5/HMS structure promotes catalyst activity in which the high amount of 99.8% conversion obtained with PRSZH at T=500 °C. Increasing temperature has an adverse effect on CO selectivity in all catalysts. The best CO2 selectivity (100%) was observed at 500 ○C and Pt(0.3 wt%)‐Sn(0.3 wt%))-HZSM-5/HMS. The proper kinetics study leads to suitable decisions about catalytic performance. Employing two models, it was possible to provide good information about the kinetic behavior of the prepared catalysts. Although both modeling methods exhibit outstanding performances, however, kinetics data reveal that Mars-van Krevelen model has better performances compared to the Power law model.

The BET method is known to be the conventional method for surface area measurements. Surface area determination is the result of the application of the linearized form of the BET equation to determine the volume of the adsorbed gas in the monolayer. An adsorbed molecule occupies an area that is inaccessible to other molecules on the surface. Taking this into account, we have reported a correction factor k´ as the ratio of Van der Waals constant (b) and the molar volume of the liquid (ν ̅), which corrects the monolayer volume of the adsorbed gas obtained from the BET model. As the size of the molecule increases, the obtained correction factor will be higher.

A co-impregnation method was applied to the Ni/Zr-HMS/HZSM-5 catalyst (with various amounts of zirconium) during the hydrogenation of benzene. The physicochemical properties of the prepared nickel catalyst were characterized using X - ray diffraction, X - ray fluorescence, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, temperature-programmed desorption of ammonia, H2 chemisorption, N2 adsorption - desorption, and thermogravimetric analysis. The catalytic performance was assessed on a fixed-bed reactor (reaction temperature between 130 °C and 190 °C). The results indicated that the nickel catalyst with Si/Zr = 35 exhibited better catalytic performance and stability than others, so providing a better selectivity in long-term performance.

Ni/Al-HMS/HZSM-5 catalysts with varying amounts of Si/Al ratios were prepared via the impregnation method and evaluated for the hydrogenation of benzene at 130−190 °C. To study the catalyst characterization, various methods were used as X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, temperature-programmed desorption of ammonia, H2 chemisorption, N2 adsorption-desorption, and thermogravimetric analysis. The effect of reaction temperature and residence time on catalytic performance was considered and kinetic of this reaction was investigated under different pressures. The results demonstrated that the composite catalysts have high benzene conversion (~80%), medium to low toluene and xylene conversion (16–80%), moderate benzene selectivity (~50%) in the mild reaction condition, and good catalytic stability against the coke deposition.

Nickel catalysts were prepared with different methods and used for hydrogenation of benzene in the refinery platformate. The catalysts were evaluated in a continuous fixed-bed reactor at atmospheric pressure and temperature range of 473-423 K. The physicochemical properties of catalysts were identified by XRD, XRF, FESEM, EDS-map, H2 adsorption and nitrogen adsorption/desorption methods. The effect of hydrogen to benzene ratio and space velocity on catalysts activity were studied. The percentage of nickel particles dispersion is dependent to the method of preparation, the amount of loaded nickel and the interaction between the support and nickel. The catalysts produced by the sedimentation and sol-gel method, 4-6 times more than toluene hydrogenated benzene in the platformate. The highest benzene conversion at 448 K temperature was obtained by catalyst prepared by sedimentation. This catalyst has a better performance in the hydrogenation of benzene due to the greater dispersion and homogeneity of nickel particles.

Pt/Zr(x)-HMS/HZSM-5 catalysts with various Si/Zr ratios (as x) were used for investigation of the kinetics of n-heptane reforming process under 350 - 450 oC reaction temperature, 35 to 80 ml min-1 flowing rate of hydrogen and 2 to 5 ml h-1 flowing rate of n-heptane. In the present work, two kinetics (power law and Langmuir - Hinshelwood) models were selected and examined to describe the kinetics of the n-heptane reforming process over the used catalysts. The results show that the Langmuir - Hinshelwood model provides a better fit with the experimental data and allows to determine the kinetics parameters. Among the synthesized catalysts, Pt/Zr(35)-HMS/HZSM-5 (with Si/Zr = 35) has the best performance for this process. Because this catalyst in contrast to others, based on the apparent activation energies, has a fast formation of aromatic and isomeric products, and low rate on the production of by-products, such as cracking and hydrogenolysis products.

Reaction behaviors and kinetics of catalytic oxidation of toluene with different feed flows over Pt/Zr(x)-HMS catalysts with Si/Zr ratio equal to 5, 10, 20 and 35 were investigated over a wide temperature range (200 – 500 oC). Results show that Pt/Zr(x)-HMS performs more easily toluene oxidation. The kinetic data were fitted by the Power-law and Mars–van Krevelen kinetic models. The fitting results show that the Mars–van Krevelen model (R2 > 0.99) is more suitable for predicting the conversion of toluene than the Power law model (R2 = 0.53), and the Mars–van Krevelen model can accurately express the reaction rate of this process.