مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Dehydration of ethanol over heteropoly acid
catalysts in the gas phase
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رابط إلى البحث:
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here
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تاريخ النشر:
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27/09/2014
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موجز عن البحث:
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Dehydration of ethanol was studied at a gas–solid
interface over a wide range of solid Brønsted acid catalysts based on
Keggin-type heteropoly acids (HPAs) in a continuous flow fixed-bed reactor in
the temperature range of 90–220 °C focussing on the formation of diethyl
ether (DEE). The catalysts included H3PW12O40 (HPW) and H4SiW12O40 (HSiW)
supported on SiO2, TiO2, Nb2O5 and ZrO2 with sub-monolayer HPA coverage, as
well as bulk acidic Cs salts of HPW (Cs2.5H0.5PW12O40 and Cs2.25H0.75PW12O40)
and the corresponding core–shell materials with the same total composition
(15%HPW/Cs3PW12O40 and 25%HPW/Cs3PW12O40, respectively) comprising HPW
supported on the neutral salt Cs3PW12O40. The ethanol-to-DEE reaction was
found to be zero order in ethanol in the range of 1.5–10 kPa ethanol
partial pressure. The acid strength of catalysts was characterised by ammonia
adsorption microcalorimetry. A fairly good correlation between the catalyst
activity (turnover frequency) and the catalyst acid strength (initial enthalpy
of ammonia adsorption) was established, which demonstrates that Brønsted acid
sites play important role in ethanol-to-DEE dehydration over HPA catalysts.
The acid strength and the catalytic activity of core–shell catalysts
HPW/Cs3PW12O40 did not exceed those of the corresponding bulk Cs salts of HPW
with the same total composition, which contradicts the literature claims of
the superiority of the core–shell HPA catalysts.
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البحث (2):
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عنوان البحث:
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Dehydration of Methanol to Dimethyl Ether over
Heteropoly Acid Catalysts: The Relationship between Reaction Rate and
Catalyst Acid Strength
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تاريخ النشر:
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30/10/2015
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موجز عن البحث:
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Dehydration of methanol to dimethyl ether (DME) was
studied at a gas/solid interface over a wide range of bulk and supported
Brønsted acid catalysts based on tungsten Keggin heteropoly acids (HPA) and
compared with the reaction over HZSM-5 zeolites (Si/Al = 10–120). Turnover
rates for these catalysts were measured under zero-order reaction conditions.
The HPA catalysts were demonstrated to have much higher catalytic activities
than the HZSM-5 zeolites. A good correlation between the turnover rates and
catalyst acid strengths, represented by the initial enthalpies of ammonia
adsorption, was established. This correlation holds for the HPA and HZSM-5
catalysts studied, which indicates that the methanol-to-DME dehydration with
both HPA and HZSM-5 catalysts occurs via the same (or similar) mechanism and
the turnover rate of methanol dehydration for both catalysts is primarily
determined by the strength of catalyst acid sites, regardless of the catalyst
pore geometry.
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البحث (3):
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عنوان البحث:
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Deoxygenation of Ethers and Esters over Bifunctional
Pt–Heteropoly Acid Catalyst in the Gas Phase
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رابط إلى البحث:
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here
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تاريخ النشر:
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12/02/2016
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موجز عن البحث:
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Deoxygenation and decomposition of ethers and
esters, including anisole, diisopropyl ether (DPE), and ethyl propanoate
(EP), was investigated using bifunctional metal-acid catalysis at a gas-solid
interface in the presence and absence of hydrogen. The bifunctional catalysts
studied comprised Pt, Ru, Ni and Cu as the metal components and Cs2.5H0.5PW12O40
(CsPW), an acidic Cs salt of Keggin-type heteropoly acid (HPA) H3PW12O40, as
the acid component, with the main focus on Pt–CsPW catalyst. It was found
that bifunctional metal-acid catalysis in the presence of H2 is more
efficient for ether and ester deoxygenation than the corresponding
monofunctional metal and acid catalysis and that metal- and acid-catalyzed
pathways play a different role in these reactions. With Pt-CsPW,
hydrodeoxygenation of anisole, a model for the deoxygenation of lignin,
occurred with 100% yield of cyclohexane under very mild conditions (60-100 oC
and 1 bar H2). This catalyst had the highest activity in anisole
deoxygenation for a gas-phase catalyst system reported so far. The catalyst
activity decreased in the order of metals: Pt >> Ru > Ni > Cu.
For HPAcatalyzed DPE and EP decomposition, relationships between the turnover
reaction rate (turnover frequency) and the HPA acid strength were found,
which can be used to predict the activity of acid catalysts in these reactions.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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8th
Saudi Students’ Conference
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تاريخ الإنعقاد:
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31/01/2015
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مكان
الإنعقاد:
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London, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Dehydration of ethanol over heteropoly
acid catalysts in the gas phase
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ملخص المشاركة:
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Dehydration of ethanol was studied at a gas-solid
interface over a wide range of solid Brønsted acid catalysts based on
Keggin-type heteropoly acids (HPAs) in a continuous flow fixed-bed reactor in
the temperature range of 90-220 oC focussing on the formation of diethyl
ether (DEE). The catalysts included H3PW12O40 (HPW) and H4SiW12O40 (HSiW)
supported on SiO2, TiO2, Nb2O5 and ZrO2 with sub-monolayer HPA coverage, as
well as bulk acidic Cs salts of HPW (Cs2.5H0.5PW12O40 and Cs2.25H0.75PW12O40)
and the corresponding core-shell materials with the same total composition
(15%HPW/Cs3PW12O40and25%HPW/Cs3PW12O40, respectively) comprising HPW
supported on the neutral salt Cs3PW12O40. The ethanol-to-DEE reaction was
found to be zero order in ethanol in the range of 1.5-10 kPa ethanol partial
pressure. The acid strength of catalysts was characterised by ammonia
adsorption microcalorimetry. A fairly good correlation between the catalyst
activity (turnover frequency) and the catalyst acid strength (initial
enthalpy of ammonia adsorption) was established, which demonstrates that
Brønsted acid sites play important role in ethanol-to-DEE dehydration over
HPA catalysts. The acid strength and the catalytic activity of core-shell
catalysts HPW/Cs3PW12O40 did not exceed those of the corresponding bulk Cs
salts of HPW with the same total composition, which contradicts the
literature claims of the superiority of the core-shell HPA catalysts.
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المؤتمر (2):
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عنوان المؤتمر:
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Designing New Heterogeneous Catalysts:
Faraday Discussion
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تاريخ الإنعقاد:
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06/04/2016
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مكان
الإنعقاد:
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London, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Dehydration of alcohols over heteropoly
acid catalysts in the gas phase
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ملخص المشاركة:
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Dehydration of methanol and ethanol has attracted
much interest in the context of sustainable development to produce fuels from
non-petroleum feedstock.1 Here we report the dehydration of MeOH and EtOH at
a gas-solid interface over a wide range of solid acid catalysts based on
Keggin-type heteropoly acids (HPAs), focussing on the formation of dimethyl
(DME) and diethyl (DEE) ethers (eq. 1 and 2). These are expected to play
important role in the energy sector as clean fuel alternatives.2-4
2 CH3OH → (CH3)2O + H2O (1)
2 CH3CH2OH → (CH3CH2)2O + H2O (2)
DME and DEE are the thermodynamically favored
products and predominantly form at lower temperatures, whereas increasing
reaction temperature leads to the formation of hydrocarbons at the expense of
ethers. The HPA catalysts showed good performance stability without evidence
of deactivation and exhibit significantly higher activity than zeolite HZSM-5
due to the stronger acidity of HPA.
The formation of DME and DEE may be represented by
two different pathways termed the associative pathway and the dissociative
pathway. Both are thought to involve alcohol adsorption on Brønsted acid
sites. Under the conditions studied, the dehydration of alcohols was zero
order in alcohol, i.e., catalyst active sites were saturated with alcohol. A
fairly good correlation between the catalyst activity (TOF) and the catalyst
acid strength (NH3 adsorption enthalpy measured by microcalorimetry) was
established (Fig. 1), which demonstrates that Brønsted acid sites indeed play
important role in these reactions over HPA catalysts.
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