Applied Petrochemical Research (v.5, #2)
A comparative study of different fluorine-containing compounds in the preparation of novel alumina binders with rich Brönsted acid sites by Peng Bai; Rui Feng; Songtao Liu; Peng Zhang; Zifeng Yan; Zhengguo Tan; Zhongdong Zhang; Xionghou Gao (81-87).
Alumina is commonly used as a catalyst binder together with aluminum sol in modern fluid catalytic cracking (FCC) catalysts. The surface acidity properties of alumina strongly affect the catalytic performance of FCC catalysts. Lewis acid sites tend to produce coke because of their dehydrogenation activity, while Brönsted ones produce less coke. Thus, it is beneficial to convert the surface Lewis acid sites into Brönsted type. Fluorine-containing modifiers have been demonstrated to be effective to generate Brönsted acid sites on alumina surface. However, different types of fluorine-containing compounds may have different modification effects. In this work, three fluorine-containing compounds, ammonium fluoroborate (NH4BF4), ammonium fluorosilicate [(NH4)2SiF6], and ammonium fluoride (NH4F), were tested and compared in the modification of alumina surface acidity. Results show that NH4BF4 and (NH4)2SiF6 perform equally well in the generation of Brönsted acid sites, while NH4BF4 is more effective in the reduction of Lewis acid sites. In comparison, NH4F is not so effective in the generation of Brönsted acid sites as the other two compounds.
Keywords: Alumina; Modification; Brönsted acid; Lewis acid; Fluorine
Slurry-phase hydrocracking of heavy oil and model reactant: effect of dispersed Mo catalyst by Hui Du; Ming Li; Dong Liu; Yuyang Ren; Yajing Duan (89-98).
Thermal hydrocracking and catalytic hydrocracking of heavy oil and model reactant have been carried out to investigate the effect of dispersed Mo catalyst on slurry-phase hydrocracking. The XRD and XPS patterns suggested that the major existence form of dispersed Mo catalyst in slurry-phase hydrocracking was MoS2. Experimental data revealed that the conversion of feedstock oils and model reactant increased with the presence of catalyst, while the yields of light products (gas, naphtha) and heavy products (vacuum residue, coke) decreased, the yields of diesel and vacuum gas oil increased in the meantime. Besides, the yields of aromatic hydrocarbon and naphthenic hydrocarbon in naphtha fraction decreased. Effect parameters R G (the ratio of i-C4H10 yield to n-C4H10 yield) and isoparaffin/n-paraffin ratio were proposed to study the reaction mechanism of slurry-phase hydrocracking, the smaller effect parameters showed that there was no carbonium ion mechanism in slurry-phase hydrocracking, which still followed the free radical mechanism, and that the isomerization ratio of products decreased with the presence of Mo catalyst.
Keywords: Slurry phase; Hydrocracking; Heavy oil; MoS2 ; Free radical mechanism; Molybdenum naphthenate
Synthesis of pyridine and methylpyridines over zeolite catalysts by Nellya Gennadievna Grigor’eva; Nadezhda Alexandrovna Filippova; Marina Ivanovna Tselyutina; Boris Ivanovich Kutepov (99-104).
The synthesis of pyridines has been performed by a multi-component reaction of ethanol, formaldehyde, and ammonia in the presence of H-Beta, H-ZSM-12, and H-ZSM-5 zeolite catalysts. The maximum activity in the reaction is revealed by H-Beta zeolite; the conversion of ethanol induced by it reached 70% (400 °C, 2 h−1). The main products of the reaction in the presence of H-Beta and H-ZSM-5 zeolites are pyridine and picolines; on H-ZSM-12 picolines and lutidines. Thus, the results of the studying the effect of reaction parameters are showed that the yield of lutidine and heavy products increases with the increase of the temperature (from 200 to 400 °C) and the decrease of the weight hourly space velocity (from 10 to 2 h−1).
Keywords: Pyridine; Picolines; Lutidines; Zeolites; Multi-component reaction
Ruthenium diphosphine complexes as an efficient hydroamination catalyst by Bahareh Tamaddoni Jahromi; Ali Nemati Kharat; Mostafa M. Amini; Hamidreza Khavasi (105-112).
Ruthenium-catalyzed hydroamination of alkenes and alkynes with substituted anilines in the presence of various phosphine ligands have been investigated and catalyst activity and selectivity is improved. Ruthenium(II) complexes of diphenylphosphinomethane, diphenylphosphinoethane, diphenylphosphinopropane, diphenylphosphinobutane and diphenylphosphinopentane showed 50–90 % conversion under mild conditions. The effect of diphosphine ligands, substituent groups on anilines and reaction condition on the selectivity of hydroamination reaction were studied and the possible reaction mechanism was discussed. The reaction products were monitored by GC–MS and a mechanism for the hydroamination of alkenes and alkynes by ruthenium diphosphine complexes was proposed and discussed. The structures of two new complexes, C49H58Cl4P2Ru2 and C35H36Cl2P2Ru, as hydroamination catalysts were determined by X-ray crystallography.
Keywords: Ruthenium complexes; Diphosphine ligands; Hydroamination; Homogeneous catalyst
Environmentally benign process for benzylation of toluene to mono-benzylated toluene over highly active and stable hierarchical zeolite catalyst by Kakasaheb Y. Nandiwale; Pratika Thakur; Vijay V. Bokade (113-119).
The liquid-phase benzylation of toluene with a benzylating agent like benzyl chloride (BC) is an important process for the production of mono-benzylated toluene (MBT), which is an industrially important compound used in pharmaceutical intermediates, fragrances, monomers for polycarbonate resins, heat-transfer fluids, aromatic solvents and fine chemicals. Selective synthesis of MBT by benzylation of toluene with BC over hierarchical micro-mesoporous-H-ZSM-5 (modified zeolite) catalyst was systematically studied for the first time. Hierarchical micro-mesoporous composites of H-ZSM-5 were obtained by treating parent H-ZSM-5 with different alkali (aq. NaOH) concentration. The synthesized catalysts were characterized by powder X-ray diffraction (XRD), BET surface area, TPAD, etc. The 100 % BC conversion with 100 % MBT selectivity was obtained over Hier-HZ-578 (Hierarchical H-ZSM-5) at lower molar ratio (toluene:BC) of 4:1 than 10:1 molar ratio reported, so far. The invented catalyst was also observed to be reusable for six catalytic cycles (one fresh and five recycles). The detailed optimization of process parameters such as molar ratio, catalyst loading and reaction time and temperature is also discussed.
Keywords: Toluene; Benzyl chloride; Benzylation; Mono-benzylated toluene; Hier-HZ-578
Alkylation of benzene with ethanol over modified HZSM-5 zeolite catalysts by Abdi Nemera Emana; Shri Chand (121-134).
Alkylation of benzene with ethanol was analysed using unmodified as well as modified shape selective HZSM-5 (Si/Al = 31) zeolite catalysts. The reaction was carried out in a continuous fixed bed flow reactor in the temperature range of 300–500 °C at atmospheric pressure to investigate the activity of various catalysts for the selectivity and yield of ethylbenzene (the desired product). The alkylation of benzene with ethanol (2:1 by volume) produces ethyl benzene as primary product and others like diethylbenzene, triethylbenzene and xylene mixtures as secondary products. The modification of HZSM-5 was done by impregnation using boron and magnesium. The modification caused changes in the surface area, acidity and pore volume of zeolite sample. The physiochemical properties of catalysts were characterised by XRD, TEM, BET, TGA, FTIR, NH3-TPD and SEM. The feed and products were analysed by gas chromatography. The conversion of benzene was found to be better in bi metallic (B and Mg) modified HZSM-5 followed by unmodified HZSM-5. The modified catalysts gave better selectivity (72.8 %) and yield (38.1 %) of ethylbenzene.
Keywords: Alkylation; HZSM-5; Bimetallic; Benzene; Ethanol; Ethylbenzene
Thermodynamic analysis of synthesis of cyclopentanol from cyclopentene and comparison with experimental data by Benzhen Yao; Zhiqing Wang; Tiancun Xiao; Fahai Cao; Peter P. Edwards; Wangjing Ma (135-142).
Cyclopentanol is a very important chemical intermediate, which has been widely used in the chemical industry, and could be prepared from cyclopentene by two steps: an initial addition-esterification reaction of cyclopentene with acetic acid and the subsequent transesterification reaction with methanol. However, so far, no direct theoretical or experimental work has been reported on this process. In this work, we have carried out the thermodynamic calculation of the indirect process and also validated the thermodynamic prediction through experimental work. The liquid heat capacities of cyclopentanol and cyclopentyl acetate were estimated using the Ruzicka–Domalski group contribution method, the standard enthalpy of formation and standard entropy of gaseous cyclopentyl acetate by the Yoneda group contribution method, the standard vaporization enthalpy of cyclopentyl acetate by the Ducros group contribution method. The enthalpy changes, free energy changes, equilibrium constant and equilibrium conversion of the addition-esterification and transesterification reactions were calculated according to the principles of chemical thermodynamics in the temperature range from 273.15 to 373.15 K. The results showed that both the addition-esterification reaction and transesterification reaction were exothermic, the free energy changes increased with a rise on temperature, which indicated that low temperature was favorable for the reactions in the temperature range from 273.15 to 373.15 K. The optimal addition-esterification reaction conditions were a temperature range from 333.15 to 353.15 K, molar ratios of acetic acid to cyclopentene in the range from 2:1 to 3:1. For the transesterification reaction, the ideal temperature ranges from 323.15 to 343.15 K, with a molar ratio of methanol to cyclopentyl acetate in the range from 3:1 to 4:1. These thermodynamic calculation results for the addition-esterification reaction of cyclopentene and acetic acid experiments results are in good agreement with the experimental results.
Keywords: Cyclopentene; Acetic acid; Methanol; Cyclopentanol; Cyclopentyl acetate; Group contribution method; Thermodynamic analysis
Mixed aluminoxanes: efficient cocatalysts for bisphosphineamine/Cr(III) catalyzed ethylene tetramerization toward 1-octene by Tao Wang; Xianglu Gao; Pengfei Shi; Haixiang Pei; Tao Jiang (143-149).
In this study, we examined catalyst systems comprising chromium(III) chloride tetrahydrofuran, diphenylphosphinoamine (PNP) ligand, and a mixed activator of methylaluminoxane (MAO) and alkylaluminum for the selective tetramerization of ethylene. By comparing the catalytic activities and the selectivities toward 1-hexene and 1-octene, we investigated the effects of various mixed aluminoxane systems on the ethylene tetramerization process. MAO/trimethylaluminum, MAO/triethylaluminum, and MAO/triisobutylaluminum were all effective cocatalysts for the PNP/Cr(III) ethylene tetramerization system, providing high catalytic activities and high selectivities. When using MAO/diethylaluminumchloride as the cocatalyst, PNP/Cr(III) exhibited an impressive switch in selectivity: from ethylene tetramerization to ethylene trimerization.
Keywords: Methylaluminoxane; Mixed aluminoxane; Ethylene tetramerization; Cocatalyst