مجال التميز | بحثي ودراسي |
البحوث المنشورة |
|
البحث (1): | |
عنوان البحث: | Dehydration of methanol and ethanol over silica-supported heteropoly acids in the gas phase: surface-type versus bulk-type catalysis mechanism |
رابط إلى البحث: | https://www.sciencedirect.com/science/article/pii/S0926860X20301423 |
تاريخ النشر: | 06/05/2020 |
موجز عن البحث: | Dehydration of MeOH to dimethyl ether and EtOH to diethyl ether and ethene was studied at the gas-solid interface in the presence of bulk and SiO2-supported Keggin heteropoly acids (HPAs) H3PW12O40 (PW) and H4SiW12O40 (SiW) as catalysts. The catalysts were prepared by HPA impregnation from water and MeOH. Their acid strength, texture and structural integrity was characterised using NH3 adsorption calorimetry, BET, XRD and DRIFT spectroscopy. The strength of acid sites in HPA/SiO2 catalysts increased monotonously with HPA loading. In the dehydration of MeOH and EtOH, the turnover reaction rate for PW catalysts was higher than for SiW catalysts in agreement with their acid strength. HPA catalysts prepared from water and MeOH had a very close acid strength and showed similar activities in alcohol dehydration. The steady-state catalyst activity was found to correlate with the density of catalyst proton surface sites rather than with the HPA loading. This indicates that alcohol dehydration occurred via a mechanism of surface-type HPA catalysis at the gas-solid interface rather than a bulk-type (pseudo-homogeneous) catalysis. |
البحث (2): | |
عنوان البحث: | Diethyl Ether Conversion to Ethene and Ethanol Catalyzed by Heteropoly Acids |
رابط إلى البحث: | https://doi.org/10.1021/acsomega.1c00958 |
تاريخ النشر: | 23/03/2021 |
موجز عن البحث: | The conversion of diethyl ether (DEE) to ethene and ethanol was studied at a gas–solid interface over bulk and supported Brønsted solid acid catalysts based on tungsten Keggin heteropoly acids (HPAs) at 130–250 °C and ambient pressure. The yield of ethene increased with increasing reaction temperature and reached 98% at 220–250 °C (WHSV = 2.2 h–1). The most active HPA catalysts were silica-supported H3PW12O40 and H4SiW12O40 and the bulk heteropoly salt Cs2.5H0.5PW12O40. The HPA catalysts outperformed zeolites HZSM-5 and USY reported elsewhere. A correlation between catalyst activity and catalyst acid strength was established, which indicates that Brønsted acid sites play an important role in DEE elimination over HPA catalysts. The results point to the reaction occurring through the consecutive reaction pathway: DEE → C2H4 + EtOH followed by EtOH → C2H4 + H2O, where ethene is both a primary product of DEE elimination and a secondary product via dehydration of the primary product EtOH. Evidence is provided that DEE elimination over bulk HPA and high-loaded HPA/SiO2 catalysts proceeds via the surface-type mechanism.. |
المؤتمرات العلمية |
|
المؤتمر (1): | |
عنوان المؤتمر: | 7th UK Catalysis Conference 2021 (UKCC2021) |
تاريخ الإنعقاد: | 06/01/2021 |
مكان الإنعقاد: | United kingdom |
طبيعة المشاركة: | poster |
عنوان المشاركة: | Cracking of diethyl ether over heteropoly acids: The Relationship between Catalyst Acid Strength and Reaction Rate |
ملخص المشاركة: | The diethyl ether (DEE) conversion to ethene and ethanol was studied at a gas–solid interface over bulk and supported Brønsted solid acid catalysts based on tungsten Keggin heteropoly acids (HPAs) at 130–250 °C and ambient pressure. The yield of ethene increased with increasing reaction temperature and reached 98% at 220–250 °C (WHSV = 2.2 h–1). The most active HPA catalysts were silica-supported H3PW12O40 and H4SiW12O40 and the bulk heteropoly salt Cs2.5H0.5PW12O40. The HPA catalysts outperformed zeolites HZSM-5 and USY reported elsewhere. A correlation between catalyst activity and catalyst acid strength was established, which indicates that Brønsted acid sites play an important role in DEE elimination over HPA catalysts. The results point to the reaction occurring through the consecutive reaction pathway: DEE → C2H4 + EtOH followed by EtOH → C2H4 + H2O, where ethene is both a primary product of DEE elimination and a secondary product via dehydration of the primary product EtOH. Evidence is provided that DEE elimination over bulk HPA and high-loaded HPA/SiO2 catalysts proceeds via the surface-type mechanism. |
المؤتمر (2): | |
عنوان المؤتمر: | Heterogeneous Catalysts for Sustainable Industry at the Royal Society of Chemistry |
تاريخ الإنعقاد: | 25/11/2019 |
مكان الإنعقاد: |
Royal Society of Chemistry, Burlington House |
طبيعة المشاركة: | poster |
عنوان المشاركة: | Dehydration of ethanol to ethylene over heteropoly acid catalysts in the gas phase |
ملخص المشاركة: | The dehydration of ethanol has long been of interest to produce ethene and diethyl ether (DEE) from non-petroleum renewable feedstock. Ethene is the feedstock for about 30% of all petrochemicals, and DEE is a valuable chemical and a green fuel alternative. The current method of producing ethylene is the steam cracking of fuels, however with the current rise in global emissions of greenhouse gases, attention has turned to new, renewable methods of producing ethylene. HPAs have been found to exhibit higher catalytic activities in these reactions than oxide and zeolite catalysts, in agreement with the relative acid strength of these catalysts. Solid Keggin-type heteropoly acids Hn{XW12O40}n- (HPA) have very strong Brønsted acid sites, stronger that those in zeolites and metal oxides. Alharbi et al. showed that HPAs exhibit a higher catalytic activity than HZSM-5 in dehydration of ethanol to DEE and ethene at low temperatures, with reaction turnover rate for both catalysts determined by the strength of catalyst acid sites. There is also a side product formation of diethyl either (DEE). The mechanism of DEE formation may be represented by two different pathways termed associative and dissociative pathway. This research aims to investigate the catalytic activity of bulk and silica-supported HPA catalysts in the dehydration of ethanol to ethene and diethyl ether (DEE) in the gas phase, whilst optimising the conditions for ethylene formation over DEE formation.
The HPA catalysts included bulk H3PW12O40 (HPW) and H4SiW12O40 (HSiW), as well as HPW and HSiW supported on SiO2 at 10-60 wt% loading, prepared by wet impregnation method. Silica was chosen as the support due to its large surface area and weak interaction with HPA. The catalysts were characterized by several techniques such as BET, XRD, FTIR, ICP, and NH3 adsorption microcalorimetry. Dehydration of ethanol was studied in a continuous flow fixed-bed reactor with on-line GC analysis described previously in the temperature range of 100- 200oC at 1.5-13.6 kPa ethanol partial pressure using N2 as a carrier gas. It was found that ethanol conversion increased with increasing the HPA loading, passing a flat maximum between 25- 60% HPA loading. This can be explained by increasing the strength of catalyst active sites and decreasing the surface area, which cause the opposite effect on ethanol conversion. HSiW catalysts exhibited higher activity than HPW catalysts probably due to the larger number of proton sites in HSiW compared to HPW. Conversion varies across different ethanol partial pressures also were obtained. Alcohol dehydration follows the Langmuir kinetics with reaction order in alcohol between 0 and 1. Because of this the conversion decreases with increasing the partial pressure of ethanol. Under the conditions studied, we observed stable catalyst performance at a high ethanol partial pressure of 13kPa. |
المرفقات
- https://uksacb.org/wp-content/uploads/1-s2.0-S0926860X20301423-main-1.pdf
- https://uksacb.org/wp-content/uploads/acsomega.1c00958.pdf
- https://uksacb.org/wp-content/uploads/IMG-20190630-WA0010.jpg
- https://uksacb.org/wp-content/uploads/UKCC-Attendance-certificate_Rawan-2.pdf
- https://uksacb.org/wp-content/uploads/شهادة-مؤتمر-شهر-نوفمبر-2019-1.pdf