Reaction Kinetics, Mechanisms and Catalysis (v.81, #2)
Production of light alkenes with low CO2 emission from gas phase oxidative cracking (GOC) of hexane
by Xuebin Liu; Wenzhao Li; Hengyong Xu; Yanxin Chen (pp. 203-209).
Compared with non-oxidative pyrolysis of hexane, the rupture of C-C bonds of hexane in the GOC process becomes rather easy due to the change of thermodynamics and kinetics of the reaction with introduction of oxygen. CO predominates in the COx produced, and the ratio CO/CO2 can be as high as 16. The GOC process could be operated in an autothermic way, which would minimize energy consumption of the whole process and greatly decrease the CO2 emission. GOC seems to be an environmentally benign and promising alternative route for light alkenes production using heavy feedstock.
Keywords: carbon monoxide; hexane; light alkenes; Gas phase oxidative cracking
Processing effects of nanometric rare earth-doped tin oxides on the synthesis of methyl vinyl ketone
by Adeilton Pereira Maciel; Neftalí Lenin Villarreal Carreño; Poty Rodrigues de Lucena; Edson Roberto Leite; Elson Longo; Humberto Vieira Fajardo; Antoninho Valentini; Luiz Fernando Dias Probst (pp. 211-217).
Nanoparticle catalysts based on SnO2 were processed by two different methods, víz.the polymeric precursor and high-energy mechanical milling. The sample morphology and catalytic performance in the aldol condensation between methanol and acetone were modified by the processing and rare earth doping.
Keywords: rare-earth; aldol condensation; Nanostructured tin oxide
Catalytic properties of LnSrCoO4 (Ln = La, Sm) in the oxidation of CO and C3H8
by Xiaomao Yang; Laitao Luo; Hua Zhong (pp. 219-227).
Perovskite-like LnSrCoO4(Ln=La, Sm) mixed oxides of K2NiF4 structure were synthesized by the polyglycol gel method and used successfully for CO and C3H8 oxidation for the first time. The structure was characterized by means of XRD, TEM, BET, O2-TPD and CO2-TPD, respectively. An oxidation mechanism over LnSrCoO4is proposed.
Keywords: LnSrCoO4; C3H8 oxidation; perovskite-like; CO oxidation
Liquid-phase Friedel-Crafts benzoylation of benzene using CuxMn(1-x)Fe2O4 spinel catalysts
by Kanat Nishamol; Koyakitty Shamsudeen Rehna; Sankaran Sugunan (pp. 229-234).
The liquid-phase Friedel-Crafts acylation of benzene using benzoyl chloride as benzoylating agent was carried out over a CuxMn(1-x)Fe2O4(x = 0, 0.2, 0.4, 0.6, 0.8 and 1) type system. The catalytic activity has been correlated with surface acidity.
Keywords: Spinels; benzene; benzoylation
Synthesis of bisphenol A catalyzed by Et3NHCl-AlCl3 ionic liquids
by Li-Juan Jia; Chun-Yan Hua; Li-Yi Dai; Yong-Kui Shan (pp. 235-240).
Ionic liquids consisting of triethylamine hydrochloride and anhydrous aluminium chloride (Et3NHCl-AlCl3) were found to work well as Lewis acid catalysts in the synthesis of bisphenol A by condensation of phenol with acetone. Under the optimum conditions (a molar ratio of 8:1 of phenol to acetone, 10.7 mmol Et3NHCL-AlCl3, N = 0.6 per 10 mmol acetone, 0.2 mmol mercaptan per 10 mmol acetone, 60oC for 4 h in 25 mL toluene) the selectivity and the yield can reach 94.70 and 85.05% respectively.
Keywords: synthesis; Et3NHCl-AlCl3 ionic liquids; catalysis; bisphenol A
Catalytic wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene
by Berkant Kayan; A.Murat Gizir; Ferruh Erdogdu (pp. 241-249).
The rates of wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene in the presence of excess oxygen and at different temperatures and oxygen pressures was investigated. Oxidation experiments were carried out at temperatures between 180 and 225oC and oxygen partial pressures of 1,0-3,0 MPa, in a 280 mL glass vessel-inserted stainless steel reactor. Copper sulfate (CuSO4 .5H2O) was used as a catalyst, and the effect of catalyst loading was studied by varying the concentration: 0.75, 2.5 and 25 mg/L as Cu2+. Addition of Cu2+ ions in the reaction media accelerated 2-nitrotoluidine oxidation nearly ten times even if it exists in trace amount in the reaction medium (0.75 ppm Cu2+). Unfortunately copper did not show catalytic effect for the oxidation of 2,4-dinitrotoluene.
Keywords: Catalytic wet air oxidation; 4-dinitrotoluene; 2-nitrotoluidine; 2
Oxidative dehydrogenation of propane over Mo/g-Al2O3. effect of precursor
by Florencia C. Calaza; Manuel F. Gomez; Luis A. Arrua; Osmar A. Ferretti; María C. Abello (pp. 259-264).
Alumina supported molybdenum oxide was prepared using ammonium heptamolybdate and molybdenum acetate as different precursors. The catalysts were characterized by BET, AAS, SEM-EDAX, XRD, TPR and surface acidity measurements. The characterization results and the catalytic behavior in oxydehydrogenation of propane were similar irrespective of precursor.
Keywords: Oxidative dehydrogenation of propane; Mo-?Al2O3 catalyst
Two-stage catalytic system of Sn/Al2O3 and Pt/Al2O3for NO reduction by propene in lean conditions
by Junhua Li; Jiming Hao; Lixin Fu (pp. 265-272).
The Pt/Al2O3, Sn/Al2O3catalysts were prepared by the single sol-gel method. The two-stage Sn/Al2O3and Pt/Al2O3catalyst in series for NO reduction with propene were investigated. The coexistance of water vapor enhanced the activity at medium temperature of 300-400oC, and the NO conversion was above 50% at 225 to 500oC even in the presence of water vapor and SO2.
Keywords: two-stage; Pt/Al2O3; NO reduction; Sn/Al2O3
Rearrangement of 2-methyl-2,3-epoxypentane: a kinetic study
by Kurti Kurtev; Darina Kehayova; Magdalena Mitkova; Atanas Tomov (pp. 273-280).
The kinetics of the rearrangement of 2-methyl-2,3-epoxypentane over ZnCl2/pumice stone is reported. 2-Methyl-3-pentanone and 2,2-dimethylbutanal are formed in parallel reactions. The reaction scheme and kinetic equations best fitting the experimental data are given.
Keywords: 3-epoxypentane; ZnCl2/pumice stone; kinetics; 2-Methyl-2; epoxides rearrangement
Reactions of chlorobenzene and bromobenzene with methyl acrylate using a conventional supported palladium catalyst
by Fengyu Zhao; Masahiko Arai (pp. 281-289).
Reactions of bromobenzene and chlorobenzene with methyl acrylate were carried out in N-methylpyrrolidone (NMP) over a conventional Pd/C catalyst under Heck coupling conditions indicating both heterogeneous and homogeneous character. Benzene and biphenyl are produced in addition to the Heck coupling product of methyl cinnamate. It is proposed that the formation of methyl cinnamate and biphenyl proceed homogeneously with dissolved palladium species, while the formation of benzene takes place heterogeneously on the surface of supported palladium particles or free colloidal particles formed during the reaction.
Keywords: product distribution; Supported palladium catalyst; chlorobenzene; bromobenzene
Study on deactivation and regeneration of Pd/Al2O3 catalyst in hydrogen peroxide production by the anthraquinone process
by Qingfa Wang; Li Wang; Yaquan Wang; Fei He; Zhenhua Li; Zhentao Mi (pp. 297-304).
Deactivated palladium catalysts in the hydrogenation of anthraquinione were regenerated with ethanol, nitric acid, hydrogen peroxide, boiling water and steam, respectively. The deactivated and regenerated catalysts were characterized by XPS, ICP, TG, FTIR, TPD, XRD, etc., and studied in the hydrogenation of anthraquinone. The results showed that the main cause of catalyst deactivation is the coverage of the active component by deposits. The treatments by hydrogen peroxide and boiling water can effectively regenerate the deactivated catalysts.
Keywords: Anthraquinone route; palladium catalyst; regeneration; deactivation
Dehydrogenation of 2-propanol with suspended noble metal catalysts: activity enhancement by the addition of sodium hydoxide
by Yuji Ukisu; Tatsuo Miyadera (pp. 305-311).
Catalytic dehydrogenation of 2-propanol was carried out in the presence of suspended Rh/C, Ru/C, Pd/C, Pt/C or Pt/Al2O3 under boiling and refluxing conditions. Adding NaOH to the 2-propanol enhanced the H2 evolution rate by a factor of 1.06-52.9, depending on the catalyst. The activity enhancements observed with KOH, Mg(OH)2, Ca(OH)2 and NaHCO3 were lower than those with NaOH.
Keywords: Dehydrogenation; noble metal catalyst; 2-propanol; alkaline compound
Thermal stability of wüstite structure modified with calcium cations
by Xiaonian Li; Yaqing Cen; Huazhang Liu; Yusheng Xu; Guanglie Lv (pp. 313-320).
Wüstite modified with calcium cations was prepared by high temperature fusion. Mössbauer spectroscopy and X-ray diffraction were employed to identify wüstite phases before and after thermal treatment at elevated temperatures in vacuum with a base pressure of 1.33 Pa for 60 h. Experimental results demonstrated that the location of calcium cations inside the wüstite structure could prevent disproportionation into magnetite and α-iron.
Keywords: Wüstite; structure stability; calcium cations; modification
One-step preparation of manganese-, iron-, and aluminum-promoted sulfated zirconias for reaction of butane to isobutane
by Makoto Hino; Kazushi. Arata (pp. 321-326).
Highly active superacids of Mn-, Fe-, and Al-sulfated ZrO2's for the isomerization of butane to isobutane were obtained by exposing zirconia gel to aqueous solutions of 0.05 M MnSO4, 0.25 M FeSO4, and 0.5 M Al2(SO4)3 followed by calcining in air at 700, 600, and 675°C, respectively. The catalysts were much more active than the superacid of sulfated zirconia, the temperature difference to show the same conversion (20%) between the catalysts and sulfated zirconia being 85, 77, and 85°C for the Mn-, Fe-, and Al-catalysts, respectively.
Keywords: impregnation; metal sulfate; Al-sulfated zirconia; Mn-; Fe-; butane
Homologation of ethylene without metathesis on silica supported ruthenium catalyst
by Takashi Suzuki (pp. 327-331).
A 1:1 mixture of 12C2-C2H4 (H2C=CH2) and 13C2-C2H4 (H2 13C=13CH2) was contacted on Ru/SiO2at 200oC. Propylene (homologation) was observed without 13C1-C2H4 formation (metathesis reaction). This might at least be corroborating evidence for discrimination of active sites in regard with the homologation and the metathesis.
Keywords: disproportionation; Homologation; metathesis; chain elongation; fischer tropsch synthesis
Diphenylmethane transformations over boron trifluoride modified alumina and silica-alumina
by Piotr Winiarek; Juan Carlos Q. Colmenares; Elżbieta Fedoryńska (pp. 333-339).
Transformations of diphenylmethane were investigated in a flow system in the presence of alumina and silica-alumina modified with boron trifluoride at atmospheric pressure and elevated temperatures. Hydrogen transfer reaction was observed on addition of tetralin to the substrate stream.
Keywords: hydrogen transfer reaction; Diphenylmethane transformations
Vanadia impregnated iron-pillared montmorillonite for aniline methylation
by Rahna Koyakutty Shamsudeen; Kanat Nisha; Sankaran Sugunan (pp. 341-348).
Vanadia impregnated iron-pillared montmorillonites with different weight percentages of vanadia have been prepared. Subsequent characterization by XRD, FT-IR, surface area and pore volume measurements was carried out. Acidity was determined by three independent techniques namely thermogravimetric desorption of 2,6-dimethylpyridine, spectrophotometric monitoring of adsorption of perylene and temperature-programmed desorption of ammonia. Conversion of cumene in the vapor phase has been performed as a test reaction of acidity. Aniline methylation was carried out to check the catalytic efficiency of the solids.
Keywords: Cumene cracking; aniline methylation; pillared montmorillonite
Effect of potassium on alumina supported chromium oxide catalysts for methylene chloride oxidation
by Lee-Dong Hwang; Hyoung-Sik Kim; Byung-Hwan Kim; Min Kang; Jin-Won Park (pp. 349-355).
Alumina supported chromium oxide catalysts added potassium were prepared and tested for methylene chloride oxidation. They were investigated by XRD, BET, XPS, chemisorption. Chromium oxide catalyst added potassium of 1 wt.% has a large beneficial effect on activity.
Keywords: CVOCs; potassium; Chromium oxide catalyst; methylene chloride oxidation
Chemiluminescence in the reaction of ozone with 1,3-dioxans in aqueous solutions
by A.A. Gusmanov; N.A. Agapitova; Yu.S. Zimin; I.M. Borisov (pp. 357-364).
Chemiluminescence in the visible part of spectrum is found to assist the oxidation of substituted 1,3-dioxans by ozone in aqueous media. The kinetics of the chemiluminescence decay was studied in the temperature interval 323-353 K, and the activation parameters of this process were determined. A kinetic scheme is proposed to explain the results.
Keywords: 1; 3-Dioxans; chemiluminescence; oxidation; ozone; kinetics
Catalytic effect of CO2 on peroxynitrite decomposition in the presence of cyanide complexes
by Ernesto Martínez; Antonio E. Mucientes; Francisco J. Poblete; Ana Rodríguez (pp. 365-371).
The catalytic effect of CO2 on the kinetics and yields of peroxynitrite decomposition in the presence of cyanide complexes was investigated as a function of pH, substrate, bicarbonate and nitrite concentration.
Keywords: peroxynitrite; Stopped-flow; CO2-catalysis; cyanide complexes
Mössbauer studies of the phase composition and microstructure of the La1-xCaxFeO3-y system as related to the reactivity of surface and bulk oxygen
by L.A. Isupova; I.S. Yakovleva; I.I. Gainutdinov; Yu.T. Pavlyukhin; V.A. Sadykov (pp. 373-382).
The phase composition and microstructure of samples of the La1-xCaxFeO3-y system prepared via a ceramic route were characterized by Mössbauer spectroscopy. In all cases, iron was found in the 3+ state. The ordering of anion vacancies in the samples with the composition in the range of 0.8 > x ≥ 0.4, which corresponds to a microheterogeneous solid solution, generates new distorted octahedral and fivefold/tetrahedral sites revealed by two typical sextets. The disordering of this solid solution and small (10-100 Å) sizes of domains with a perovskite, braunmillerite or Grenier phase structure caused the appearance of a superparamagnetic doublet, which grows with the Ca content up to x = 0.8 but disappears in the sample of pure braunmillerite. The appearance of Fe cations in a distorted coordination correlates with the increased activity of the samples with a microheterogeneous structure in the CO catalytic oxidation and with their reducibility by H2.
Keywords: Calcium-doped lanthanum ferrite; Mössbauer spectroscopy
Kinetics of oxidative dehydrogenation of isobutyraldehyde over Cs2HPMo12O40 catalyst
by Pavel Čičmanec; Jan Bouchal; Josef Tichý (pp. 383-391).
The kinetics of oxidative gas-phase dehydrogenation of isobutyraldehyde over Cs2HPMo12O40 catalyst has been studied in a flow-through integral reactor at 523 K at atmospheric pressure. The catalytic reaction has been found to be accompanied by oxidation of isobutyraldehyde outside the catalyst bed. The rate of formation of methacrolein is satisfactorily described by the rate equation derived on presumption of change in the mean activation energy. The rate of the reaction in the homogeneous phase was described by empirical pseudo-first order equation.
Keywords: oxidative dehydrogenation; Isobutyraldehyde; methacrolein; Cs2HPMo12O40
Reactivity of surface and bulk oxygen in La1-xCaxFeO3-y system with respect to methane oxidation
by V.A. Sadykov; L.A. Isupova; I.S. Yakovleva; G.M. Alikina; A.I. Lukashevich; S. Neophytides (pp. 393-398).
The reactivity and mobility of the surface and lattice oxygen in a La1-xCaxFeO3-y system prepared via a ceramic route were studied by using CH4-TPR. While the middle-temperature (400-700oC) oxygen lattice mobility reaches maximum for samples with disordered anion vacancies, the high-temperature lattice oxygen flux appears to be controlled by a rapid transfer along disordered domain walls. In the high-temperature range, a high selectivity to syngas of methane oxidation by the lattice oxygen was achieved both for pure lanthanum ferrite and for samples with a microdomain structure.
Keywords: methane combustion; selective oxidation into syngas; CH4-TPR; mobility and reactivity of the lattice oxygen
Book Review: Encyplopedia of Pharmaceutical Technology
by James Swarbrick; James J. Boylan (pp. 399-400).
James Swarbrick:Pharmaceutech, Inc., Pinehurst, North Carolina and aaiPharma Inc., Wilmington, North Carolina, U.S.A.; James J. Boylan: Pharmaceutical Consultant, Gurnee, Illinois, U.S.A.;