Surface Acidity of H-Beta and Its Catalytic Activity for Alkylation of Benzene with Propylene

The acidity of H-beta zeolites with SiO₂/Al₂O₃ ratios ranging from 20 to 350 was characterized by NH₃-TPD profiles and FTIR spectra of adsorbed pyridine. As SiO₂/Al₂O₃ ratios of the H-beta zeolites increased, NH₃-TPD acidic amount of the samples is decreased. The IR bands of the adsorbed pyridine on the zeolites are also decreased with the increased SiO₂/Al₂O₃ ratios. The batch reaction of propylene and benzene was carried out in liquid phase at 423 K over H-beta zeolites. The selectivity to isopropylbenzene was high. The catalytic activity of H-beta zeolites is in direct proportion to the acidic amount of the zeolites in general. H-beta zeolite of SiO₂/Al₂O₃=27, which contains the highest amount of Brønsted acid sites as indicated by FTIR spectra of adsorbed pyridine, is the most reactive catalyst in the alkylation reaction. In continuous liquid-phase reactions, high propylene conversion and isopropylbenzene selectivity can be achieved at 413–453 K with benzene to propylene mole ratio from 4 to 8. The catalytic activity and selectivity of the H-beta zeolite do not change after 1100 h of reaction.     

Benzoylation of anisole over borate zirconia solid acid catalyst

B₂O₃/ZrO₂ solid catalyst containing 30 mol% boron oxide prepared by wet impregnation method and calcined at 500 °C showed efficient catalytic activity in liquid phase benzoylation of anisole with benzoyl chloride (BOC) in nitrobenzene solvent at 150 °C. B₂O₃/ZrO₂ catalyst under study has shown comparable performance with conventional homogeneous AlCl₃ catalyst as well as heterogeneous catalysts such as zeolite H-beta and sulphated zirconia with maximum conversion and selectivity to the corresponding 4-methoxy benzophenone (4-MBP). The effect of various experimental parameters such as temperature, nature of solvent, reaction time and the effect of various benzoylating agents has been discussed. The conversion of anisole to 4-MBP increases significantly with increasing reaction time and temperature. The maximum conversion of about 91% with yield of acylated product >96% and selectivity for 4-MBP >94% was observed after 22 h. 2-MBP was found to be <4%. The phenyl benzoate (3%) formed by the O-benzoylation of anisole was found to be a major side product. The catalyst was recycled three times without any appreciable decrease in the anisole conversion showing its stability.     

光稳定剂二苯甲酮合成新工艺研究

以苯甲酰氯、三氯化苄和苯为原料合成二苯甲酮,分别研究了反应温度、反应时间、原料配比、催化剂用量、溶剂的用量等条件对合成反应的影响,确定了最佳工艺条件。该方法合成二苯甲酮的最适宜的工艺条件是:反应温度120℃、反应时间12 h、n(苯甲酰氯)∶n(苯)=1∶1.7,n(苯甲酰氯)∶n(三氯化苄)=7.35∶1,催化剂用量为4.25 g(相对于0.588 mol苯甲酰氯),二苯甲酮的收率可达到94.54%以上,产品纯度二苯甲酮99.5%。     

High activity of iron containing metal-organic-framework in acylation of p-xylene with benzoyl chloride

Catalytic behavior of metal-organic-frameworks (MOFs) Cu₃(BTC)₂, MIL-100(Fe) and MIL-100(Cr) was investigated in p-xylene acylation with benzoyl chloride and compared with the behavior of large pore zeolites Beta and USY. It has been clearly shown that MIL-100(Fe) exhibit much higher conversion of benzoyl chloride with excellent selectivity in p-xylene acylation. The performance of MIL-100(Fe) catalyst was favorable with those of other conventional heterogeneous catalysts like zeolites. Conversion of benzoyl chloride equal to 100% was achieved over MIL-100(Fe) with 20-30 min under optimized reaction conditions. It is assumed that unsaturated Lewis acid sites associated with the presence of Fe exhibit optimum acid strength for catalyzing this acylation reaction.     

On the use of infrared spectroscopy in the study of carbon dioxide decomposition on copper containing methanol synthesis catalysts

A novel and convenient procedure for the catalytic acylation of a series of aromatic compounds such as benzene, toluene, xylenes (o-, m-, p-), mesitylene, isopropylbenzene and N,N-dimethylaniline to the corresponding ketones using medium- and large-pore zeolites as catalyst and acetic acid or acetyl chloride as acylating agent at different reaction temperatures in a tubular reactor is demonstrated for the first time. The H-ZSM5 and H-beta zeolite catalysts exhibited the higher turnover rates (TOF× 10^-3 s^-1 mol^-1 Al) for the acetic acid or acetyl chloride conversion to the products. In some cases, nearly total conversion of acylating agent with very high selectivity to the para product is achieved. It is found that the reactivity of the aromatic compounds increases with the increase of -CH₃ groups in the benzene ring. Mechanistically, it is assumed that an active species (CH₃CO⁺) is generated catalytically from the acylating agent by an acidic zeolite which attacks the aromatic ring and produces corresponding aromatic ketones.     

Acylation of Benzene over Clay and Mesoporous Si-MCM-41 Supported InCl3, GaCl3 and ZnCl2 Catalysts

Liquid phase acylation of benzene by acyl chloride (e.g., benzoyl chloride, butyryl chloride or phenyl acetyl chloride) over InCl₃, GaCl₃ and ZnCl₂ supported on commercial clays (viz. montmorillonite-K10, montmorillonite-KSF and kaolin) or high silica mesoporous MCM-41 at 80°C has been investigated. The Mont.-K10 and Si-MCM-41 supported InCl₃ and GaCl₃ catalysts showed high activity in the acyation of benzene by benzoyl chloride even in the presence of moisture in the reaction mixture. The redox function of the supported InCl₃, GaCl₃ or ZnCl₂ catalysts seems to play a very important role in the acylation process.     

三氯化铁低压催化合成二苯酮工艺改进

以三氯化铁为催化剂（催化剂B）,用苯和苯甲酰氯合成二苯酮;以三氧化二铁为助催化剂,可降低反应温度、压力,缩短反应时间,提高产率;考察催化剂B用量、苯甲酰氯加入方式、压力及溶剂用量对反应的影响,表明最优工艺条件为：m（催化剂B）：m（FeCl3）=4：1,苯甲酰氯一次性加入,迅速排气,维持系统压力0．4MPa,反应时间7．5h,二苯酮收率97％。     

加压下FeCl_3催化Friedel-Crafts酰化反应合成二苯甲酮

研究了在加压和催化量 Fe Cl3存在的条件下 ,苯甲酰氯和苯发生 Friedel- Crafts酰化反应合成二苯甲酮的工艺。 3 1 5 .2 g苯、1 43 .4g苯甲酰氯和 14.4g Fe Cl3混合于 2 L的高压釜中 ,在压力为 1 .6× 1 0 6～ 1 .8× 1 0 6Pa、温度为 1 80～ 2 0 0°C的条件下反应 8h,经纯化处理得到二甲苯酮 1 49.3 g,收率为 82 .1 %,纯度为 99.8%( GC分析 )     

Modified Beta Zeolite as Catalyst for Fries Rearrangement Reaction

Modified beta zeolites were applied as catalysts for the Fries rearrangement reaction. The properties of the modified zeolites were characterized by NH₃-TPD, n-hexane and 1,2,4-trimethylbenzene adsorption. Modification with SiO₂ did not block the pores of the beta zeolite but reduced the number of acid sites on the surface. However, when the beta zeolite was modified with Ce₂O₃, the number of acid sites determined by NH₃-TPD increased, which indicated that new acid sites are created by the interaction of cerium oxide and zeolite. Modified beta zeolites and H-beta were applied as catalysts for the Fries rearrangement of phenol acetate. Reaction over H-beta has low selectivity and the catalyst is easily deactivated. SiO₂ modification of the catalyst increases the selectivity of the reaction but decreases the conversion. Ce₂O₃-modified beta zeolites show higher catalytic activity and rearrangement selectivity in the reaction than other catalysts. The stability of the catalyst is also improved after Ce₂O₃ modification. About 70% selectivity and 60-80% conversion can be achieved over 16 wt% Ce₂O₃-modified beta zeolite.     

Friedel–Crafts type benzylation and benzoylation of aromatic compounds over Hβ zeolite modified by oxides or chlorides of gallium and indium

Liquid phase benzylation (by benzyl chloride) and benzoylation (by benzoyl chloride) of benzene and other aromatic compounds over different Ga- and In-modified Hβ zeolite catalysts at 80 °C have been investigated. An impregnation of the zeolite by oxides or chlorides of Ga and In makes the zeolite highly active in the benzylation process but it results in a decrease in the acidity, particularly the strong acid sites (measured in terms of the ammonia chemisorbed at 250 °C) of the zeolite. Both the redox function, created due to the modification of the Hβ zeolite by Ga or In, and the zeolitic acidity seem to play important role in the benzylation or benzoylation process. Among the different Ga- and In-modified Hβ zeolite catalysts, the In₂O₃/Hβ showed highest activity for the benzene benzylation. This catalyst also showed high activity for both the benzylation and benzoylation of other aromatic compounds, even in the presence of moisture in the reaction mixture; in case of the benzoylation, the moisture has beneficial effect. The In₂O₃/Hβ catalyst can be reused in the benzylation for several times. Kinetics of benzene benzylation (using excess of benzene) over the different Ga- and In-modified Hβ zeolite catalysts has also been investigated. A plausible mechanism for the activation of both the reactants (aromatic substrate and benzyl or benzoyl chloride, forming corresponding carbocation) over the catalyst and also for the reaction between the carbocation and the activated and/or non-activated aromatic substrate is proposed.     

Regioselective nitration of o-xylene to 4-nitro-o-xylene using nitric acid over solid acid catalysts

The regioselective nitration of o-xylene to 4-nitro-o-xylene (4-NOX) has been studied in the liquid and vapor phase over zeolites H-beta, H-ZSM-5 and silica supported molybdenum oxide (MoO₃/SiO₂) catalysts. Zeolite H-beta showed the maximum conversion of 28% and 63% selectivity for 4-NOX in liquid phase nitration at 70 °C with 70% HNO₃. The conversion increased to 65% when the reaction was carried out in vapor phase at 150 °C using dilute 30% HNO₃. The formation of α-methylphenyl nitromethane by alkyl nitration in liquid phase was decreased in vapor phase reaction. The formation of oxidation products was also decreased in vapor phase reaction with minor amounts of dinitro and ipso-products. The influence of experimental parameters such as temperature, nitric acid concentration and WHSV on conversion and selectivity has been investigated. The use of dilute nitric acid and the selective formation of 4-NOX using dilute HNO₃ makes this process environmental friendly with a potential for commercialization.     

H-beta分子筛催化苯与甲醇烷基化反应性能

采用两种促进剂协同作用改性制得了H-beta分子筛催化剂,通过XRD、BET及Py-IR对催化剂结构、比表面积及酸性变化进行表征,并将催化剂用于苯与甲醇烷基化测试其催化性能。结果表明,在反应压力为常压、反应温度400℃、空速2 h-1和苯与甲醇物质的量比为1∶1的最优条件下,苯转化率达到42. 5%、甲苯选择性为74. 6%,甲苯和二甲苯总选择性达到了94. 5%。基于结构及性能的研究,探讨了催化烷基化反应机理。     

Effect of Support Materials on the Selective Methanation of CO over Ru Catalysts

Selective methanation of CO in the reformate gas (CO/CO₂/H₂/H₂O = 0.175/17.9/70.9/11.1) proceeded over Ru catalysts supported on metal oxides and zeolites. CO was selectively methanated at wide temperature ranges (200–275 °C) over Ru/γ-Al₂O₃, Ru/TiO₂ Ru/H-Y and Ru/H-beta catalysts. Higher Ru contents in Ru/γ-Al₂O₃ improved the selective CO methanation rate.     

Mesoporous beta zeolite obtained by desilication

Zeolite beta crystals (Si/Al = 35) synthesized in fluoride medium were treated in aqueous 0.2 M NaOH solution for mesopore formation by selective extraction of framework silicon. A 16 parallel-batch reactor was used to study the influence of the treatment time and temperature on the physico-chemical properties of the zeolites, which were characterized by ICP-OES, XRD, N₂ adsorption at 77 K, SEM, TEM, DRIFTS, and in situ ATR-IR. Alkaline treatment of H-beta within the optimal window of Si/Al ratios identified for other zeolite families leads to extensive silicon extraction at mild treatment conditions. This originates substantial mesoporosity and presumably improved transport, but negatively impacts on the microporous and acidic properties of the resulting sample. Consequently, the alkaline-treated beta zeolites show lower catalytic activity in the acid-catalyzed liquid-phase benzene alkylation than the purely microporous parent material. The relatively low stability of framework aluminum in BEA, compared to MFI and MOR, is detrimental for the controlled mesopore formation by Si dissolution, since aluminum cannot optimally exert its pore-directing role.     

Effect of Phosphate Modification on the Brønsted Acidity and Methanol‐to‐Olefin Conversion Activity of Zeolite ZSM‐5

Phosphate‐modified ZSM‐5 zeolites were studied by standard characterization techniques and solid‐state nuclear magnetic resonance spectroscopy, and in the methanol‐to‐olefin (MTO) conversion. Considering the physicochemical properties of the ZSM‐5 zeolites, the most important effects of the phosphate modification are a deposition of polyphosphates in the pore system and a decrease of the acid site density, but not of the acid site strength. The significant increase in the selectivity to C₂ – C₄ alkenes and the decrease of C₅₊ formation in the MTO reaction for a phosphate coverage of about 5 wt % are explained by extra‐framework phosphate species near the crossing intersections of the ZSM‐5 pore system, which hinder the formation of large intermediates and reaction products.     

Anionic living polymerization of macromonomers: Preparation of a particle-like purging reagent and characterization of poly(macromonomer)s

A cross-linked polystyrene particle (Merrifield resin, R-C₆H₅) was reacted with benzoyl chloride in nitrobenzene to produce R-C₆H₄-COC₆H₅ having a benzophenone group, and the R-C₆H₅-COC₆H₅ was reacted with a sodium mirror in THF under 10⁻⁵ mmHg to produce R-C₆H₅-CO⁻C₆H₅Na⁺ containing a benzophenone sodium as a particle-like purging reagent (PPBNa). (4-vinylbenzyl)Polystyrene macromonomers (PSM4: M_n=4.6₂×10³, M_w/M_n=1.0₃ and PSM7: M_n=7.1₀×10³, M_w/M_n=1.0₂) were dried under 10⁻⁶ mmHg for more than 72 h, purified by a special procedure using the PPBNa, and then were living anionically polymerized by sec-BuLi in benzene or n-BuLi in tetrahydrofuran to produce the corresponding poly(PSM)_n star polymers. The resultant star polymers were characterized by gel permeation chromatography equipped with low-angle laser light-scattering (GPC-LALLS), membrane osmometry (OSM), and light-scattering (LS). Anionic living polymerization of the PSM macromonomers was confirmed by the fact that the molecular weight of the poly(PSM)_n increased and by the fact that the initiation efficiency was constant despite an increase in the polymer yields. Some solution properties and specific dimensions characteristic to the poly(PSM)_n star polymers are discussed by comparing the GPC-LALLS, OSM, and LS results for those polymers with the results for linear polystyrenes.     

Benzylation of benzene to diphenylmethane using zeolite catalysts

The catalytic liquid phase benzylation of benzene to diphenylmethane (DPM) with benzyl chloride (BC) is investigated over a number of zeolite catalysts at 358 K and under atmospheric pressure. Conventional homogeneous Lewis acid catalyst, AlCl₃, is also included for comparison. Zeolite H-β is found to be more selective but less active compared to HY and H-ZSM-5 zeolites in the benzylation of benzene. The conversion of BC, rate of BC conversion and selectivity to DPM over H-β after 6 h of reaction time are 33.3 wt%, 4.7 × 10⁻³ mmol g⁻¹ h⁻¹ and 89.1 wt%, respectively. For comparison, the conversion of BC, rate of BC conversion and selectivity to DPM over AlCl₃, under identical reaction condition, are found to be 100 wt%, 170 × 10⁻³ mmol g⁻¹ h⁻¹ and 58 wt%, respectively. Higher amounts of consecutive products are obtained over AlCl₃ due to its non shape selectivity. The acidity of the zeolite catalysts is measured by temperature programmed desorption method. The effect of the duration of the run, SiO₂/Al₂O₃ ratio of H-β, catalyst concentration, reaction temperature and benzene to BC molar ratio on the catalyst performance is also investigated in order to optimize the conversion of BC and selectivity for DPM. The conversion of BC using H-β is increased with the increase in the reaction time, catalyst concentration, reaction temperature and molar ratios whereas it decreases with the increase in SiO₂/Al₂O₃ molar ratio of H-β. H-β is recycled two times and a slight decrease in BC conversion is observed after each cycle, which is related to the minor dealumination of the zeolite catalyst by HCl, which is produced during the reaction as by product. The formation of DPM is explained by an electrophilic attack of the benzyl cation (C₆H₅CH₂⁺) on the benzene ring, which is produced by the polarization of BC over acidic sites of the zeolite catalysts.     

TiO2/modified natural clay semiconductor as a potential electrode for natural dye-sensitized solar cell

TiO₂/modified natural bentonite clay semiconductor, as a potential electrode of dye-sensitized solar cell, having a Ti:Si molar ratio of 85:15 was, for the first time, compared with pure TiO₂ (commercial P25) electrode in terms of solar cell efficiency and characteristics. 4-Chloro-2,5-difluorobenzoic acid and 4-(chloromethyl)benzoyl chloride were added to the electrodes to increase light harvesting ability of natural dyes extracted from red cabbage, rosella, and blue pea. The results showed that the TiO₂/clay semiconductor provided a higher surface area but a slightly lower efficiency than the pure TiO₂. The best natural sensitizer was found to be the dye extracted from red cabbage. Besides, the 4-(chloromethyl)benzoyl chloride provided a higher short circuit current for the TiO₂/clay semiconductor.     

Liquid-phase acetylation of tetralin with acetyl chloride over zeolites: inhibition of the reaction by the products

HY and H-beta zeolites are efficient catalysts in the acetylation reaction of tetralin with acetyl chloride. Their activity depends largely on the experimental conditions and is restricted by the strong adsorption of organic species, either acetic acid or acetyltetralin formed in the reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of graft copolymerization of 2-hydroxyethyl methacrylate on the properties of polyester fibers and fabric

Graft copolymerization of hydroxyethyl methacrylate (HEMA) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (BP) as initiator was carried out in water and in water/organic solvent as a reaction medium. The effect of initiator concentration, reaction time, temperature, and reaction medium as well as addition of FeSO₄ to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing BP concentration up to 0.016 mol/L and then decreased upon further increase in initiator concentration. Increasing the monomer (HEMA) concentration up to 0.48 mol/L improves significantly the graft yield. Raising the polymerization temperature up to 85°C causes a significant increase in grafting yield; further increase in temperature leads to decrease in graft yield. Incorporation of Fe⁺² ions in the polymerization system decrease the graft yield. The same situation is encountered when water/solvent mixture is used as reaction medium. Solvent employed were methanol, toluene, and benzene.