Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

2020 ◽  
Vol 23 ◽  
Author(s):  
Sajjad Rimaz ◽  
Reza Katal
Keyword(s):  
Particle Size ◽  
Synthesis Method ◽  
Catalytic Performance ◽  
Hard Template ◽  
Structure Directing Agent ◽  
Positive Role ◽  
Methanol To Olefin ◽  
Dg Method ◽  
Synthesis Procedure

: In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure which drastically improves catalytic performance.

Synthesis and Modification of SAPO-34 Nanoparticles by Incorporation of Metal Ions Using Rapid High Temperature Method

2013 ◽  
Vol 829 ◽  
pp. 627-631 ◽  
Author(s):  
Mohammad Hasan Dadjoo ◽  
Rouein Halladj ◽  
Sima Askari ◽  
Shadi Jalili
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
High Temperature ◽  
Synthesis Method ◽  
Diffusion Path ◽  
Methanol Conversion ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Strength Distribution ◽  
Synthesis Time

Considering studies done on the result of methanol conversion over SAP-34 molecular sieve, it is understood that increase of selectivity is ascribed to the increase of acidity in acid sites which is a result of incorporation of metal in crystal structure and decrease of crystal size. In this study, metal incorporation in the SAPO-34 structure leaded to increase of acid sites concentration but did not affect the acid strength distribution. The catalytic performance of the SAPO-34 nanoparticles in the MTO reaction varied according to their crystallite size. Decreasing particle size results in larger increase of external surface area and shorter diffusion path, both cause reduction in mass and heat transfer resistances in catalysis and sorption. In this work a rapid high-temperature synthesis method was developed to synthesis uniform nanoparticles of SAPO 34 zeolite with high crystallinity and metal was successfully incorporated in crystal structure. In order to investigate the effects of temperature and synthesis time on purity and crystallinity of the synthesized samples, the crystallization temperature was increased from 350 to 550 K while the synthesis time was decreased from 24 h to 45 min. The samples were characterized by XRD, BET and SEM analysis techniques. It was found that by using high temperature and short synthesis time the particle size decreased and the metal was properly incorporated into the crystal structure.

On the Performance of Metal Supported Catalysts Prepared by Microemulsion: Sol Gel and Precipitation of the Support Precursor

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Gustavo Pérez ◽  
J. Luis Suaste ◽  
César Barrales ◽  
J. Antonio De los Reyes ◽  
Juan Pérez-Sea ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Sol Gel ◽  
Synthesis Method ◽  
Active Phase ◽  
Catalytic Performance ◽  
Ammonium Bromide ◽  
Microemulsion Method ◽  
Structure Sensitive ◽  
Cetyltrimethyl Ammonium

Ni/SiO2, NiMo/Al2O3 and CoMo/Al2O3 were prepared by microemulsion method. Precipitation and sol-gel of the support precursor allowed the synthesis of catalysts with differences in textural, structural and catalytic properties. The main difference between the precipitation and sol-gel microemulsion routes is the role of surfactant (Cetyltrimethyl Ammonium Bromide) in each synthesis method. The aggregation mechanism of support is modified by the synthesis route. There are differences in the catalytic performance of Ni/SiO2 microemulsion catalysts by the precipitation or sol-gel of support precursor. The hydrogenation of benzene, a low structure-sensitive reaction, showed that the precipitation 9%Ni/SiO2 microemulsion catalyst is more active than the sol-gel 9%Ni/SiO2 microemulsion catalyst. On other hand, these catalysts showed opposite result in the hydrogenation of C=C double bond of crotonaldehyde molecule. These results are indicative of the effects of nanostructured support and nanostructured active-phase in the hydrogenation activity. NiMo/Al2O3 and CoMo/Al2O3 catalysts prepared by sol-gel-microemulsion method were used in the hydrodesulphurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene. The HDS activity was improved as a function of metal content and it motivates the study of NiMo and CoMo microemulsion catalysts with higher contents of metals to enhance the HDS of 4,6-dimethyldibenzothiophene.

Role of Synthesis Method and Particle Size of Nanostructured TiO2 on Its Photoactivity

2002 ◽  
Vol 212 (2) ◽  
pp. 145-156 ◽  
Author(s):  
Catherine B. Almquist ◽  
Pratim Biswas
Keyword(s):  
Particle Size ◽  
Synthesis Method ◽  
Nanostructured Tio2

Are Three Items Sufficient to Measure Sense of Coherence?

2018 ◽  
Vol 34 (4) ◽  
pp. 229-237 ◽  
Author(s):  
Francesca Chiesi ◽  
Andrea Bonacchi ◽  
Caterina Primi ◽  
Alessandro Toccafondi ◽  
Guido Miccinesi
Keyword(s):  
Sense Of Coherence ◽  
Convergent Validity ◽  
Clinical Sample ◽  
Clinical Samples ◽  
Depression Symptoms ◽  
Time Saving ◽  
Positive Role ◽  
Patients With Cancer ◽  
Measure Sense

Abstract. The present study aimed at evaluating if the three-item sense of coherence (SOC) scale developed by Lundberg and Nystrom Peck (1995) can be effectively used for research purpose in both nonclinical and clinical samples. To provide evidence that it represents adequately the measured construct we tested its validity in a nonclinical (N = 658) and clinical sample (N = 764 patients with cancer). Results obtained in the nonclinical sample attested a positive relation of SOC – as measured by the three-item SOC scale – with Antonovsky’s 13-item and 29-item SOC scales (convergent validity), and with dispositional optimism, sense of mastery, anxiety, and depression symptoms (concurrent validity). Results obtained in the clinical sample confirmed the criterion validity of the scale attesting the positive role of SOC – as measured by the three-item SOC scale – on the person’s capacity to respond to illness and treatment. The current study provides evidence that the three-item SOC scale is a valid, low-loading, and time-saving instrument for research purposes on large sample.

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

Sign in / Sign up

Export Citation Format

Share Document