Search Results

You are looking at 61 - 70 of 90 items for :

  • Refine by Access: All Content x
Clear All

Abstract  

β-MCM41 composite molecular sieves were hydrothermally synthesized using NaOH treated β zeolite as precursors, and Pt/β-MCM41 bifunctional catalysts were prepared by impregnation. Hβ, desilicated Hβ by NaOH treatment (Dβ), and the physical mixture of Hβ and MCM41 (β+MCM41) were also used as control supports for bifunctional catalysts. All the catalysts were characterized by ICP, XRD, BET, nitrogen adsorption–desorption isotherm and NH3-TPD, and evaluated in the hydroisomerization of n-heptane using an atmospheric fixed bed flow reactor. Dβ, β+MCM41, or β-MCM41 supported Pt catalysts showed higher selectivity to isoheptanes than the counterpart Pt/Hβ did due to the presence of mesopores in addition to the zeolite micropores. Moreover, Pt/β-MCM41 was demonstrated to be a much more selective catalyst among them because the connection between mesopores and micropores accelerated the diffusion of larger molecules of isoheptanes. Under optimal conditions, Pt/β-MCM41 provided a very high selectivity to isomerization of 96.5%, coupled with a considerable high conversion of n-heptane of 56.0%.

Restricted access

Abstract  

We have investigated the interaction of water with Na+-ion exchanged zeolites of different structures (LTA, FAU, ERI, MOR and MFI) by means of temperature-programmed desorption (TPD). The non-isothermal desorption of water shows, depending on the zeolite type, differently structured desorption profiles. In every case the profiles have, however, two main ranges. Using a regularization method, desorption energy distribution functions have been calculated. The desorption energy distributions between 42–60 kJ mol−1, which can be attributed to a non-specific interaction of water, show two clearly distinguished energy ranges. The water desorption behaviour of this range correlates with the electronegativity of the zeolites and the average charge of the lattice oxygen atoms calculated by means of the electronegativity equalization method (EEM). The part of the desorption energy distributions in the range of 60–90 kJ mol−1, reflecting interactions of water with Na+ cations, shows two more or less pronounced maxima. In agreement with vibrational spectroscopic studies in the far infrared region, it may be concluded that all samples under study possess at least two different cation sites.

Restricted access

according to the BET equation. The basicity of the samples was measured by CO 2 temperature-programmed desorption (CO 2 -TPD) on Quantachrome CHEMBET-3000. 0.200 g sample was pre-treated at 550 °C for 1 h in dry He flow (50 ml/min), and cooled

Restricted access

) applying the same temperature program. Thus, carbon yield could be calculated as a balance between residual masses determined after TG analyses in argon and in air. The temperature programmed desorption (TPD) measurements were carried out with use of

Open access

aromatization of the intermediates [ 2 ]. A lot of work on NH 3 -TPD, XPS, FTIR, ESR, NMR and EXAFS [ 15 – 19 ] done by several groups showed that impregnated Mo species are mainly located on the external zeolite surface. After calcination, part of Mo species

Restricted access

/customer-demand-leads-the-way-to-digitalized-banking-in-asia-pacific/ , accessed 25 / 07 / 2019 . Touchpoint Dashboard ( 2014 ): A Guide to Customer Journey Mapping . http://www.touchpointdashboard.com/wp-content/uploads/2014/03/TPD-Mapping-Guide-2014.pdf

Open access

FID detector. Catalyst characterization The surface area and acidity characteristics of H-beta were obtained, respectively, by N 2 adsorption and temperature programmed desorption (TPD) of NH 3 . The catalyst

Restricted access

-programmed desorption of ammonia (NH 3 –TPD) experiments. About 100 mg of sample was used in each measurement. The samples were pretreated at 500 °C for 1 h under argon stream (20 mL min −1 ). After that, the sample was cooled down to 100 °C, and pulse NH 3 (99

Restricted access

The catalyst alkalinity was measured on a quartz microreactor (TP-5080, Tianjin-Xianquan, China) through a temperature-programmed desorption of carbon dioxide (CO 2 -TPD) experiment. About 50 mg of sample was used in each measurement. The samples were

Restricted access

CO 2 conversion with time on stream. The promotional effect of CeO 2 –ZrO 2 was verified by measuring the changes of nickel crystallite size, reducibility and the extent of CO 2 activation with the help of TPR, H 2 -chemisorption, CO 2 -TPD and XRD

Restricted access