Change search
Link to record
Permanent link

Direct link
BETA
Rownaghi, Ali
Publications (10 of 15) Show all publications
Zhou, M., Rownaghi, A. & Hedlund, J. (2013). Synthesis of mesoporous ZSM-5 zeolite crystals by conventional hydrothermal treatment (ed.). Paper presented at . RSC Advances, 3(36), 15596-15599
Open this publication in new window or tab >>Synthesis of mesoporous ZSM-5 zeolite crystals by conventional hydrothermal treatment
2013 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, no 36, p. 15596-15599Article in journal (Refereed) Published
Abstract [en]

Well-defined ZSM-5 crystals with tablet habit, uniform size, controllable silica/alumina ratio, and high mesoporosity were prepared using conventional hydrothermal treatment under stirring. The key to obtaining high mesoporosity of the crystals was to stir a synthesis mixture containing a relatively high concentration of alumina

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-9072 (URN)10.1039/c3ra42199f (DOI)000323271700011 ()2-s2.0-84882716865 (Scopus ID)7a2bc238-4bce-4036-bd69-63a6210175e8 (Local ID)7a2bc238-4bce-4036-bd69-63a6210175e8 (Archive number)7a2bc238-4bce-4036-bd69-63a6210175e8 (OAI)
Note
Validerad; 2013; 20130903 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Häggström, C., Öhrman, O., Rownaghi, A., Hedlund, J. & Gebart, R. (2012). Catalytic methanol synthesis via black liquor gasification (ed.). Fuel processing technology, 94(1), 10-15
Open this publication in new window or tab >>Catalytic methanol synthesis via black liquor gasification
Show others...
2012 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 94, no 1, p. 10-15Article in journal (Refereed) Published
Abstract [en]

Biofuel production from gasified black liquor is an interesting route to decrease green house gas emissions. The only pressurised black liquor gasifier currently in pilot operation is located in Sweden. In this work, synthesis gas was taken online directly from this gasifier, purified from hydrocarbons and sulphur compounds and for the first time catalytically converted to methanol in a bench scale equipment. Methanol was successfully synthesised during 45 h in total and the space time yield of methanol produced at 25 bar pressure was 0.16–0.19 g methanol/(g catalyst h). The spent catalyst exposed to gas from the gasifier was slightly enriched in calcium and sodium at the inlet of the reactor and in boron and nickel at the outlet of the reactor. Calcium, sodium and boron likely stem from black liquor whereas nickel probably originates from the stainless steel in the equipment. A slight deactivation, reduced surface area and mesoporosity of the catalyst exposed to gas from the gasifier were observed but it was not possible to reveal the origin of the deactivation. In addition to water, the produced methanol contained traces of hydrocarbons up to C4, ethanol and dimethyl ether.

National Category
Chemical Process Engineering Energy Engineering
Research subject
Chemical Technology; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-4219 (URN)10.1016/j.fuproc.2011.09.019 (DOI)000300740100002 ()2-s2.0-80755176260 (Scopus ID)222cc047-e892-4afd-9efc-9f87f2d002f2 (Local ID)222cc047-e892-4afd-9efc-9f87f2d002f2 (Archive number)222cc047-e892-4afd-9efc-9f87f2d002f2 (OAI)
Note

Validerad; 2012; 20111114 (ysko)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A., Rezaei, F., Stante, M. & Hedlund, J. (2012). Selective dehydration of methanol to dimethyl ether on ZSM-5 nanocrystals (ed.). Paper presented at . Applied Catalysis B: Environmental, 119-120(7), 56-61
Open this publication in new window or tab >>Selective dehydration of methanol to dimethyl ether on ZSM-5 nanocrystals
2012 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 119-120, no 7, p. 56-61Article in journal (Refereed) Published
Abstract [en]

The effects of crystal size and mesoporosity on the performance of various synthesized ZSM-5 zeolites in catalytic dehydration of methanol to dimethyl ether (DME) reaction have been investigated. The reactions were carried out in a continuous flow fixed-bed reactor at temperatures between 180 to 320 °C and 1.1 bar. It was found that methanol conversion enhances by decreasing crystal size and increasing the reaction temperature. Uniform nanocrystal catalysts showed highest activity and stability for methanol dehydration to dimethyl ether in the temperature range studied. On the other hand, both the activity and selectivity of large crystals were low. The high activity and DME yield for the nanocrystals is due to smaller mass transport resistance for the Nano-ZSM-5 sample, due to the small crystal size. Furthermore, it was found that the selective dehydration of methanol to dimethyl ether on ZSM-5 catalyst is based on the product selectivity inside the pore channels; in other words, the selectivity to dimethyl ether should be 100% if there is no acid site on the external surface. From this evidence, it is concluded that in methanol dehydration to DME, the reaction activity is related to the crystal size, whereas the DME selectivity is determined by the uniformity of Al distribution, which determines acidity of external surface and low mass transport resistance of small crystal size. Therefore, a decrease in the number of acid sites on the external surface and reduction in crystal size are key ways to enhance catalytic selectivity and activity, respectively.

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-14798 (URN)10.1016/j.apcatb.2012.02.017 (DOI)000304691700007 ()2-s2.0-84858717846 (Scopus ID)e3817f55-4037-41ac-9f61-7b3a280d9fc2 (Local ID)e3817f55-4037-41ac-9f61-7b3a280d9fc2 (Archive number)e3817f55-4037-41ac-9f61-7b3a280d9fc2 (OAI)
Note
Validerad; 2012; 20120228 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A., Rezaei, F. & Hedlund, J. (2012). Selective formation of light olefin by n-hexane cracking over HZSM-5: influence of crystal size and acid sites of nano- and micrometer-sized crystals (ed.). Paper presented at . Chemical Engineering Journal, 191, 528-533
Open this publication in new window or tab >>Selective formation of light olefin by n-hexane cracking over HZSM-5: influence of crystal size and acid sites of nano- and micrometer-sized crystals
2012 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 191, p. 528-533Article in journal (Refereed) Published
Abstract [en]

A series of HZSM-5 catalysts with different characteristics (size, texture, surface acid site density) was prepared by hydrothermal method and their performances were investigated in catalytic cracking of n-hexane (as a model compound of light naphtha) at 370 and 470 ˚C. Uniform nano-sized HZSM-5 (ca.∼ 0.1 μm) was found to be a very attractive catalyst, showing a selective formation of propylene and light olefin (about 83% at WHSV = 3 h−1) and a high resistance to the deactivation. Under similar conditions micro-size HZSM-5 (ca.∼ 2.0 μm) produced higher amount of other hydrocarbons i.e., C5+) and coke. This is because nano-size crystals have a larger external surface area, which offers a higher number of pore entrances and enhances the reaction occurring inside the pore channels compared with large miro-size crystals. In addition, it is found that the selectivity to light olefin increases by decreasing the number of acid sites on the external surface. This leads to the conclusion that in n-hexane cracking to light olefin, the activity and selectivity are related to the crystal size and the ratio of surface acid sites to total acid sites. As shown, reducing crystal size and decreasing acid sites on the external surface are remarkable ways to enhance catalytic activity and selectivity, respectively.

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-14268 (URN)10.1016/j.cej.2012.03.023 (DOI)000304793300060 ()2-s2.0-84860597860 (Scopus ID)d9f37f68-c79e-43a7-9251-3c56be6523be (Local ID)d9f37f68-c79e-43a7-9251-3c56be6523be (Archive number)d9f37f68-c79e-43a7-9251-3c56be6523be (OAI)
Note
Validerad; 2012; 20120403 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A., Rezaei, F. & Hedlund, J. (2012). Uniform mesoporous ZSM-5 single crystals catalyst with high resistance to coke formation for methanol deoxygenation (ed.). Paper presented at . Microporous and Mesoporous Materials, 151, 26-33
Open this publication in new window or tab >>Uniform mesoporous ZSM-5 single crystals catalyst with high resistance to coke formation for methanol deoxygenation
2012 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 151, p. 26-33Article in journal (Refereed) Published
Abstract [en]

In this study, an efficient procedure for controllable synthesis of uniform mesoporous ZSM-5 single crystals with various crystal architectures and high mesoporosity was developed. Compared with conventional ZSM-5 catalyst, mesoporous ZSM-5 single crystals synthesized by this method exhibited significantly higher external surface area and larger mesopore volume than conventional one. The catalytic performance of mesoporous zeolites were evaluated in the conversion of methanol to hydrocarbons using a fixed-bed reactor operating at 370 °C, atmospheric pressure and weight hourly space velocities (WHSV) of 0.16 to 6.58 h−1. By controlling the ZSM-5 synthesis procedure, the activity and stability of the ZSM-5 catalyst in the conversion of methanol to gasoline-range hydrocarbons can be favorably tuned. We also found that mesoporosity plays a crucial role in catalyst stability. Good correlation was observed between catalyst lifetime and mesoporosity. While the catalyst activity is related to the acid site density, the catalyst stability (deactivation rate) correlates with the measured surface ratio of BET and external surface area (SBET/SMeso). The novel ZSM-5 catalyst exhibited improved stability due to the faster removal of products with shorter diffusion path-length and lower coke formation. The obtained results indicated that the novel mesoporous ZSM-5 catalyst containing relatively large pores (mostly mesopores) enhances reaction yield towards gasoline-range hydrocarbons. It is therefore concluded that the relatively slow deactivation rate (coke formation) of novel mesoporous ZSM-5 single crystals catalyst makes this zeolite the preferred catalyst for the conversion of methanol to gasoline-range hydrocarbons at mild conditions.

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-3703 (URN)10.1016/j.micromeso.2011.11.020 (DOI)000300747000003 ()2-s2.0-84155163161 (Scopus ID)188eb80a-6958-4d3d-b546-f4fddaeaa54f (Local ID)188eb80a-6958-4d3d-b546-f4fddaeaa54f (Archive number)188eb80a-6958-4d3d-b546-f4fddaeaa54f (OAI)
Note
Validerad; 2012; 20111124 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A. & Hedlund, J. (2011). Methanol to gasoline-range hydrocarbons: influence of nanocrystal size and mesoporosity on catalytic performance and product distribution of ZSM-5 (ed.). Paper presented at . Industrial & Engineering Chemistry Research, 50(21), 11872-11878
Open this publication in new window or tab >>Methanol to gasoline-range hydrocarbons: influence of nanocrystal size and mesoporosity on catalytic performance and product distribution of ZSM-5
2011 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 50, no 21, p. 11872-11878Article in journal (Refereed) Published
Abstract [en]

Improvement of synthesis methods for ZSM-5 zeolite, as a heteregeneous catalyst, is essential for a wide variety of different reactions in the chemical industry. Decreasing zeolite crystal size and introducing mesoporosity into the zeolite structure can improve its performance in catalytic reaction through decreasing the micropore diffusion path length and increasing the external surface area. In this study, three different ZSM-5 zeolites (Nano-ZSM-5, Meso-ZSM-5, and Con-ZSM-5) were prepared by a single-templating procedure, and the reaction of methanol to gasoline-range hydrocarbons was evaluated over synthesized ZSM-5 crystals in a fixed bed continuous flow reactor. Good correlation was observed between catalytic performance, product distribution, mesoporosity, and crystal size of ZSM-5 zeolites. Both nanocrystal and mesoporous ZSM-5 zeolites showed long-term catalytic stability compared with the conventional one. In contrast to conventional ZSM-5 catalyst, the nanocrystal and mesoporous ZSM-5 catalysts showed high selectivities for light olefins and alkyl aromatics, respectively, in the conversion of methanol to gasoline. These results dearly indicate that both crystal size and mesoporosity significantly influence the ZSM-5 lifetime and product distribution

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-14171 (URN)10.1021/ie201549j (DOI)000296128300012 ()2-s2.0-80055036287 (Scopus ID)d8639e95-d690-4305-b015-36178d4c35b8 (Local ID)d8639e95-d690-4305-b015-36178d4c35b8 (Archive number)d8639e95-d690-4305-b015-36178d4c35b8 (OAI)
Note
Validerad; 2011; 20111110 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A., Häggström, C., Öhrman, O. & Hedlund, J. (2011). Yield of dimethyl ether and gasoline as a function of size of ZSM-5 crystals (ed.). In: (Ed.), (Ed.), 2010 AIChE annual meeting conference proceedings: Salt Palace Convention Center, Salt Lake City, UT, November 7 - 12, 2010. Paper presented at AIChE annual meeting : 07/11/2010 - 12/11/2010. New York: American Institute of Chemical Engineers
Open this publication in new window or tab >>Yield of dimethyl ether and gasoline as a function of size of ZSM-5 crystals
2011 (English)In: 2010 AIChE annual meeting conference proceedings: Salt Palace Convention Center, Salt Lake City, UT, November 7 - 12, 2010, New York: American Institute of Chemical Engineers, 2011Conference paper, Published paper (Refereed)
Abstract [en]

In this work we have studied different acidic zeolitic solid catalysts ZSM-5 with different crystal size, measuring their physical-chemical properties and correlating this with the activity, selectivity at different process condition during the conversion of methanol to dimethyl ether (DME) and gasoline boiling range hydrocarbons. The catalytic properties of these catalysts depended mainly on the crystal size and surface properties. Methanol feed in the DME and gasoline process is derived from black liquor-based syngas. The methanol to DME and gasoline process involves the conversion of black liquor syngas to crude methanol and methanol to DME and gasoline

Place, publisher, year, edition, pages
New York: American Institute of Chemical Engineers, 2011
Series
P / AIChE, American Institute of Chemical Engineers ; 264
National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-38684 (URN)d23a27a1-5226-471b-afeb-16a3039e0f4b (Local ID)978-0-8169-1065-6 (ISBN)d23a27a1-5226-471b-afeb-16a3039e0f4b (Archive number)d23a27a1-5226-471b-afeb-16a3039e0f4b (OAI)
Conference
AIChE annual meeting : 07/11/2010 - 12/11/2010
Note
Validerad; 2011; Bibliografisk uppgift: CD-ROM; 20110218 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-04-03Bibliographically approved
Rownaghi, A., Rezaei, F. & Hedlund, J. (2011). Yield of gasoline-range hydrocarbons as a function of uniform ZSM-5 crystal size (ed.). Paper presented at . Catalysis communications, 14(1), 37-41
Open this publication in new window or tab >>Yield of gasoline-range hydrocarbons as a function of uniform ZSM-5 crystal size
2011 (English)In: Catalysis communications, ISSN 1566-7367, E-ISSN 1873-3905, Vol. 14, no 1, p. 37-41Article in journal (Refereed) Published
Abstract [en]

Uniform ZSM-5 nanocrystals were synthesized by a single-templating procedure. The samples were then characterized by a variety of physical techniques such as XRD, SEM, BET, ICP and TPD. The dehydration of methanol over synthesized ZSM-5 zeolite was studied in a fixed-bed continuous flow reactor at 370 °C and WHSV of 2.6 gg−1 h under ambient pressure. The effect of crystal size of zeolite catalysts on product distribution in methanol dehydration reaction was investigated. Good correlation was observed between catalytic performance, product distribution and size of ZSM-5 crystals. It was found that the decrease in crystal size significantly influences light olefins (ethylene and propylene) and paraffins (C1–C4) selectivity in methanol dehydration reaction. Furthermore, nanocrystal ZSM-5 showed long-term catalytic stability compared with conventional ZSM-5 provided that the reaction activity is strongly dependent on the crystal size in methanol dehydration process. The results indicated that crystal size significantly affects the catalyst lifetime and hydrocarbon distributions in product stream. Based on the obtained results, it is concluded that the use of uniform ZSM-5 nanocrystals improves the yield of propylene and alkyl aromatics in methanol conversion reaction at mild conditions.

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-5750 (URN)10.1016/j.catcom.2011.07.015 (DOI)000296213700008 ()2-s2.0-79961101837 (Scopus ID)3eea8146-e0c0-44b3-abba-0ea1703add9f (Local ID)3eea8146-e0c0-44b3-abba-0ea1703add9f (Archive number)3eea8146-e0c0-44b3-abba-0ea1703add9f (OAI)
Note
Validerad; 2011; 20110808 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A., Taufiq-Yap, Y. H. & Rezaei, F. (2010). Innovative process for the synthesis of vanadyl pyrophosphate as a highly selective catalyst for n-butane oxidation (ed.). Paper presented at . Chemical Engineering Journal, 165(1), 328-335
Open this publication in new window or tab >>Innovative process for the synthesis of vanadyl pyrophosphate as a highly selective catalyst for n-butane oxidation
2010 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 165, no 1, p. 328-335Article in journal (Refereed) Published
Abstract [en]

Vanadyl pyrophosphate (VPO) catalysts are used for the selective oxidation of light alkanes, which are based on vanadyl hydrogen phosphate hemihydrate (VOHPO40.5H2O) as the precursor. Catalyst precursor with well-defined crystal size has been successfully synthesized for the first time, using a simple one-step high-pressure autoclave that was surfactant-free and water-free method with significantly lower temperature and shorter reaction time. VOHPO40.5H2O was prepared from V2O5 using an isobutanol, 1-pentanol, 1-heptanol and 1-dectanol as both solvent and reducing agent at elevated temperatures (100, 120, and 150°C). This new method significantly reduced the preparation time and lowered production temperature (50%) of catalyst precursor (VOHPO40.5H2O) when compared to conventional hydrothermal synthesis methods. VOHPO40.5H2O can be obtained at temperature far below 150°C. It was found that the presence of 1-heptanol and 1-decanol in the reaction mixtures is crucial for obtaining a well-defined crystal size of precursor phase and solely generated impurity, [VO(H2PO4)2]. Our findings show that both the phase composition and morphology of vanadium phosphate can be influenced by the use of different reducing agent and temperature during the preparation process. This new methodology produces catalysts with a much higher surface area (ca. 23m2g-1) compared with those materials prepared by slow hydrothermal synthesis (ca. 9.5m2g-1). Finally, the yield of maleic anhydride was significantly increased from 21.3% for conventional catalyst to 37.9% for the new solvothermal catalyst.

National Category
Chemical Process Engineering
Research subject
Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-5977 (URN)10.1016/j.cej.2010.09.043 (DOI)000285278900040 ()2-s2.0-78149497895 (Scopus ID)42c25530-d221-11df-a707-000ea68e967b (Local ID)42c25530-d221-11df-a707-000ea68e967b (Archive number)42c25530-d221-11df-a707-000ea68e967b (OAI)
Note
Validerad; 2010; 20101007 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Rownaghi, A. & Taufiq-Yap, Y. H. (2010). Novel synthesis techniques for preparation of ultrahigh-crystalline vanadyl pyrophosphate as a highly selective catalyst for n-butane oxidation (ed.). Paper presented at . Industrial & Engineering Chemistry Research, 49(5), 2135-2143
Open this publication in new window or tab >>Novel synthesis techniques for preparation of ultrahigh-crystalline vanadyl pyrophosphate as a highly selective catalyst for n-butane oxidation
2010 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 49, no 5, p. 2135-2143Article in journal (Refereed) Published
Abstract [en]

The vanadyl hydrogen phosphate hemihydrate (VOHPO40.5H2O), with well-defined crystal size, has been successfully synthesized for the first time, using a simple one-step solvothermal process that was free of surfactants and water and had a short reaction time and low temperature. The synthesis was performed via the reaction of V2O5 and H3PO4 with an aliphatic alcohol (1-propanol or 1-butanol) at high temperatures (373, 393, and 423 K) in a high-pressure autoclave. The mixture of reactions directly gave the VOHPO40.5H2O, which is a valuable commercial catalyst precursor for the selective oxidation of n-butane to maleic anhydride. The catalyst precursors were dried by microwave irradiation. The reaction conditions (by varying the reducing agent and reaction temperature) were used further for optimization of the crystallite size, surface area, morphology, and activity of the nanostructure of vanadium phosphate oxide [(VO)2P2O7] catalyst. This new method significantly reduced the preparation time and lowered the production temperature (50%) of catalyst precursor (VOHPO40.5H2O), when compared to conventional hydrothermal synthesis methods. The as-prepared (VO)2P2O7 catalyst under various conditions exhibited remarkably different physical and chemical properties, indicating the potential of the suggested method in tuning the crystalline structure and surface area of (VO)2P2O7 to improve its catalytic performance. It was found that the length of the carbon chain in an alcohol and reaction temperature in the solvothermal condition had a great impact on the chemical and physical properties of resulting catalysts. Interestingly, there was no trace of VO(H2PO4)2, which is an impurity noted to be readily formed under solvothermal preparation conditions. The precursors and catalysts were characterized using a combination of powder X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, scanning electron microscopy (SEM), and temperature-programmed reduction in hydrogen (H2-TPR). A correlation between the surface area of the catalyst and the activity was observed. Finally, the yield of maleic anhydride was significantly increased from 21% for conventional catalyst to 38% for the new solvothermal catalyst.

Identifiers
urn:nbn:se:ltu:diva-4081 (URN)10.1021/ie902011a (DOI)1f23e060-3b33-11df-a0f4-000ea68e967b (Local ID)1f23e060-3b33-11df-a0f4-000ea68e967b (Archive number)1f23e060-3b33-11df-a0f4-000ea68e967b (OAI)
Note
Upprättat; 2010; 20100329 (alirow)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Organisations

Search in DiVA

Show all publications