105-05-5Relevant articles and documents
Phosphate modified ZSM-5 for the shape-selective synthesis of para-diethylbenzene: Role of crystal size and acidity
Hodala, Janardhan L.,Halgeri, Anand B.,Shanbhag, Ganapati V.
, p. 8 - 16 (2014)
Pore engineered ZSM-5 zeolite in extrudate form was prepared and used as shape-selective catalyst for vapor phase ethylation of ethylbenzene to selectively form para-diethylbenzene. The physico-chemical properties of the catalyst were established by XRD, N2 sorption, FTIR, FESEM, NH 3-TPD and 31P MAS NMR. Alkylation of ethylbenzene with ethanol was carried out in a continuous, down-flow, tubular reactor, at atmospheric pressure and H2 as a carrier gas in vapor phase. Effect of silica to alumina ratio (SAR), crystal size, acidity of phosphate modified ZSM-5, stepwise phosphate modification and reaction conditions were studied in detail. ZSM-5 with SAR 187 was found to contain optimum acidity for phosphate modification to achieve good conversion and high selectivity for p-diethylbenzene. Under optimized reaction conditions, viz. temperature = 380 °C, ethylbenzene:ethanol mole ratio = 4:1, WHSV = 3 h-1, H 2/reactants = 2, 5PZSM-5 W catalyst gave 22.8% of ethylbenzene conversion with ～98% selectivity for para-diethylbenzene.
Shape Selectivity of ZSM-5 Type Zeolite for Alkylation of Ethylbenzene with Ethanol
Kim, Jong-Ho,Namba, Seitaro,Yashima, Tatsuaki
, p. 1051 - 1056 (1988)
The alkylation of ethylbenzene with ethanol on ZSM-5 zeolites was studied at 673 K.The primary product in this alkylation on HZSM-5 catalyst was only p-diethylbenzene because of the transition-state selectivity.Therefore, the isomerization of p-diethylbenzene has to be restrained for the selective formation of p-diethylbenzene.The modified HZSM-5 catalysts with oxide of magnesium, phosphorus or boron showed much higher para-selectivity than the parent HZSM-5.The modification reduced not only the effective pore dimension of HZSM-5 but also the amount of strong acid sites.We claim that the absence of strong acid sites is necessary rather than the narrowness of pores for the suppression of the isomerization of p-diethylbenzene produced as a primary product.
para-Selectivity of a Highly Siliceous ZSM-5 Zeolite Modified with Arsenic(III)
Kim, Jong-Ho,Yamagishi, Kouji,Namba, Seitaro,Yashima, Tatsuaki
, p. 1793 - 1794 (1990)
A highly siliceous ZSM-5 zeolite treated with AsCl3 vapour at 673 K exhibited a high para-selectivity (94.1percent) for the alkylation of ethylbenzene with ethanol.
Addition of arenes to ethylene and propene catalyzed by ruthenium
Lail, Marty,Arrowood, Benjamin N.,Gunnoe, T. Brent
, p. 7506 - 7507 (2003)
TpRuII(CO)(Me)(NCMe) (Tp = hydridotris(pyrazolyl)borate) serves as a catalyst precursor for the conversion of benzene and ethylene or propene to alkylaromatic products. The reaction proceeds via the formation of the active catalyst TpRu(CO)(Ph)(NCMe) and is mildly selective for linear propylbenzene over isopropylbenzene. Copyright
The influence of the external acidity of H-ZSM-5 on its shape selective properties in the disproportionation of ethylbenzene
Melson, Sabine,Schueth, Ferdi
, p. 46 - 53 (1997)
The shape selectivity of H-ZSM-5 in the disproportionation of ethylbenzene was investigated, using a set of samples with the same Si/Al ratio, but different particle sizes in the range from 0.1 to 80 μm. The number of external acid sites of each sample was measured gravimetrically by the adsorption of 2,6-dimethylpyridine. The data were correlated with the results of catalytic experiments. Conversion and product distribution are strongly dependent on the external acidity which in turn correlates well with the particle size. An estimate for the diffusion coefficient could be obtained by fitting the effectiveness factor for the different particle sizes.
Effects of Dry-air Calcination on the Physico-chemical and Catalytic Properties of HZSM-5 Zeolite
Rudham, Robert,Winstanley, Alastair W.
, p. 3191 - 3200 (1994)
A series of HZSM-5 zeolites has been prepared by dry-air calcination, in the range 833 to 1163 K, of samples from a single preparation of NH4ZSM-5 containing 5.5 framework AlT atoms per unit cell.A similar series of HZSM-5 zeolites has been prepared from NH4ZSM-5 that had been bound with colloidal silica (Ludox) prior to dry-air calcination.The zeolites were characterised using mid-IR spectroscopy, 27Al magic-angle-spinning nuclear magnetic resonance (27Al MAS NMR) and temperature-programmed desorption (TPD) of NH3.It was shown that the zeolites are highly crystalline and that extensive structural dealumination does not occur at calcination temperatures below ca. 1000 K.Framework aluminium contents determined by 27Al MAS NMR are considered to be a better measure of acid-site concentration that those given by TPD of NH3.The activity of HZSM-5 zeolites as catalysts for ethylbenzene conversion at 573 K, to ethene, benzene and diethylbenzene, was only slightly suppressed by binding with silica.Reaction is believed to proceed by a dealkylation-alkylation mechanism; a maximum in activity for unbound HZSM-5 at AlT = 2.8 suggests synergic interaction between framework and non-framework aluminium atoms.The conversion of propane at 808 K, to mainly methane, ethene and propene, showed an activity pattern closely similar to that of ethylbenzene.
Metal-free catalysis of sustainable Friedel-Crafts reactions: Direct activation of benzene by carbon nitrides to avoid the use of metal chlorides and halogenated compounds
Goettmann, Frederic,Fischer, Anna,Antonietti, Markus,Thomas, Arne
, p. 4530 - 4532 (2006)
The use of mesoporous graphitic C3N4 for the activation of benzene permitted to perform more sustainable Friedel-Crafts reactions by allowing to directly use carboxylic acids, alcohols and even quaternary ammoniums or urea as electrophiles. The Royal Society of Chemistry 2006.
Highly selective synthesis of para-diethylbenzene by alkylation of ethylbenzene with diethyl carbonate over boron oxide modified HZSM-5
Xue, Bing,Zhang, Gen,Liu, Na,Xu, Jie,Shen, Qingming,Li, Yongxin
, p. 384 - 391 (2014)
A series of B2O3/HZSM-5 catalysts were prepared by impregnation of HZSM-5 zeolites with triethyl borate, trimethyl borate and boric acid. The selective synthesis of para-diethylbenzene by alkylation of ethylbenzene with diethyl carbonate was carried out over the B2O3/HZSM-5 catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N2 adsorption-desorption, Fourier-transform infrared spectroscopy with pyridine adsorption and NH3 temperature programmed desorption. The characterization results indicated that the 15% B2O3/HZSM-5 catalyst prepared by using triethyl borate as the precursor exhibited an outstanding shape-selectivity along with a high catalytic activity in alkylation of ethylbenzene with diethyl carbonate. This might be ascribed to the large molecular size of triethyl borate, which would lead to the formation of B2O3 on the external surface of HZSM-5 zeolite and preserve the acid sites in the micropores of HZSM-5 zeolite. By contrast, the B2O3/HZSM-5 catalysts prepared by using trimethyl borate or boric acid led to the severe reduction in catalytic activity, which was attributed to the decrease in the amount of the total acid sites caused by the blockage of the partial pores of HZSM-5 zeolite.
The Thermal Cycloaddition of Dispirodeca-4,9-diene to Isolated Carbon-Carbon Multiple Bonds
Shibata, Tohru,Tsuji, Takashi,Nishida, Shinya
, p. 709 - 716 (1980)
The cycloadditions of dispirodeca-4,9-diene (1) to isolated carbon-carbon multiple bonds have proceeded in two different modes, giving dispirododeca-4,11-diene and tricyclo(6.4.0.03,6>dodeca-2,7-diene derivatives.Mono- and 1,2-disubstituted olefins and acetylenes gave the former adducts, whereas 1,1-disubstituted olefins gave the latter, as the major products.Evidence for the intermediacy of biradicals is provided.The observed difference in the mode of the cycloaddition is explained in terms of the stereoelectronic and/or steric effect in the transition state for the cyclization of the intermediate.The addition of 1 to tetracyanoethylene (TCNE) in wet acetone has proceeded via a zwitterionic intermediate(s), giving a 1:1:1 adduct of 1, TCNE, and water.
Effects of crystallinity of ZSM-5 zeolite on para-selective tert-butylation of ethylbenzene
Pushparaj, Hemalatha,Mani, Ganesh,Muthiahpillai, Palanichamy,Velayutham, Murugesan,Park, Yong-Ki,Choi, Won Choon,Jang, Hyun Tae
, p. 294 - 304 (2013)
Highly crystalline ZSM-5 zeolites are important for para-selective alkylation of alkyl aromatics, because they carry few external acid sites for isomerization of p-dialkyl products. Such zeolites (Si/Al = 25, 50, and 75) were synthesized in a fluoride medium between pH 4 and 6. Their crystallinities, crystal sizes, and surface areas were higher than those of a commercial ZSM-5 zeolite. Their para selectivities in alkylation were tested for vapor-phase tert-butylation of ethylbenzene between 200 and 400 °C. As expected, all the catalysts showed more than 90% para selectivity. At 300 °C, ethylbenzene conversion decreased in the order ZSM-5(25, commercial) > ZSM-5(25) > ZSM-5(50) > ZSM-5(75). The catalysts had weak, medium, and strong acid sites, but all the acid sites of ZSM-5(75) were weaker than those of ZSM-5(25) and ZSM-5(50). The high activity of commercial ZSM-5 was caused by its strong acid sites being stronger than those of the synthesized zeolites. Although the activity of the commercial catalyst was higher than those of the present catalysts, the selectivity for 4-t-butylethylbenzene (4-t-BEB) was low. The optimum feed ratio (ethylbenzene:t-butyl alcohol) was 2:1 and the feed rate was 1.65 h-1 for high ethylbenzene conversion and 4-t-BEB selectivity. Time-on-stream studies showed slow catalyst deactivation. Highly crystalline ZSM-5 zeolites are therefore better than a commercial zeolite for para-selective alkylation of alkyl aromatics. They do not require much post-modification for high para selectivity. A fluoride medium is therefore better than an alkaline medium for obtaining highly crystalline para-selective ZSM-5 zeolites.
