Characterization and catalytic activity for ethylene dimerization of nickel sulfate supported on zirconia

A series of catalysts, NiSO₄/ZrO₂, for ethylene dimerization were prepared by the impregnation method using aqueous solutions of nickel sulfate. The results obtained from X-ray diffraction and DSC indicate that the addition of NiSO₄ shifted the transition of ZrO₂ from amorphous to tetragonal phase toward higher temperatures due to the interaction between NiSO₄ and ZrO₂. Nickel sulfate supported on zirconia was found to be very active even at room temperature. The high catalytic activity of NiSO₄/ZrO₂ was closely correlated with the increase of acidity and acid strength due to the addition of NiSO₄. The active sites responsible for ethylene dimerization may consist of low-valent nickel, Ni⁺ and an acid.     

Catalytic cracking of rapeseed oil to high octane gasoline and olefins

Rapeseed is the most important energy crop in Europe. The basic idea of the presented work was to add vegetable oils to the standard FCC-feed in order to meet requirements on the increasing demand for climate-friendly produced fuels. The experimental test program was conducted in a fully continuously operated FCC pilot plant with internal CFB-design at Vienna University of Technology. Rapeseed oil was added in steps of 20 m% to the conventional feedstock, up to 100 m% addition. The influence on the process was observed. The obtained product spectrum at 550 °C was slightly modified in relation to standard feed VGO. The gasoline yield stayed roughly constant while the crack-gas yield decreased at higher ratios of rapeseed oil. Due to the oxygen content of rapeseed oil the additional lumps water and CO₂ are formed. Using pure rapeseed oil as feedstock for FCC leads to a total fuel yield on total feed of approximately 65 m% (23 m% gaseous hydrocarbons plus 42 m% gasoline). The gasoline achieved is oxygen free at high octane numbers of approximately RON 100 and MON 86.     

Selective propylene dimerization to 2,3-dimethylbutenes by homogeneous catalysts prepared by oxidative addition of α-nitroketones to nickel(0) complexes in the presence of phosphine ligands and organoaluminium co-catalysts

Novel nickel catalysts, prepared in situ by oxidative addition of α-nitroketones to nickel(0) complexes, in the presence of a phophine ancillary ligand and activated by organoaluminium co-catalysts were investigated in propylene oligomerization with the aim to selectively obtain 2,3-dimethylbutenes (DMB). In particular, the effect of the nature of the α-nitroketonate ligand as well as of the basicity and bulkiness of the phosphine on catalyst performances were studied. Finally, the influence of the type of organoaluminium co-catalyst and reaction temperature were examined.In particular, when the Ni(cod)₂/tricyclohexylphosphine (PCy₃)/α-nitroacetophenone (naph)/methylalumoxane (MAO) catalytic system was employed, the highest up to now reported regioselectivity within C₆ cut (>90%) was achieved. Moreover, the use of balanced mixtures of MAO and Et₂AlCl allowed to optimize the catalyst performances up to an overall yield to DMB of almost 70%, a significant productivity being also achieved (TOF=4500 h⁻¹).     

On the activity, longevity and recyclability of Mn(II) and Co(II) substituted AlPO-18 catalysts for the conversion of methanol to light olefins

The influence of the degree of substitution of the cobalt and manganese ions into AlPO-18 structure was investigated for the conversion of methanol to light olefins (MTO) at 350 °C. The results show that the activity for methanol conversion increases with transition metal content up to 2 at.% for conversion of methanol after 2 h on stream. These catalysts show good stability for this reaction after regeneration suggesting that there is no leaching of the active metal centres.     

轻烃低温芳构化制取高辛烷值汽油

考察了反应温度、空速和高径比条件对轻烃在分子筛催化剂上低温芳构化制取高辛烷值汽油性能的影响。结果表明,反应温度和空速对催化剂的催化性能有明显影响,提高反应温度有利于提高芳烃收率,增加进料空速,催化剂芳构化性能下降,芳烃二次反应也减少。在450 ℃、1.0 h^-1和高径比为6.0的条件下,此轻烃在ZSM-5催化剂作用下,可得到高辛烷值汽油,其初馏点为49 ℃,干点为203 ℃,烯烃质量分数为13.42%,芳烃质量分数为84.24%,辛烷值为101,可作汽油调和组分,也可直接作汽油使用。     

Two-step ammoniation of by-product fluosilicic acid to produce high quality amorphous silica

A two-step ammoniation was applied to neutralize the fluosilicic acid generated in the production of superphosphate fertilizer, and to recover high-quality amorphous silica in the second step. A fluosilicic acid solution at 12.6% or 25.3 wt% H2SiF6 was reacted with aqueous ammonia, precipitating silica and subsequently leaving NH₄F behind in the filtrate. Based on a fixed total of 7.2 moles of ammonia per mole of H₂SiF₆ (120% stoichiometry), ammonia at a molar ratio of ammonia to H₂SiF₆ of 2 to 6 was charged in the first step and the balance of 5.2-1.2 in the second step in four combination sets of ammonia addition. At a combination of 3 and 4.2 molar ratios in the respective first and second steps, amorphous silica of 99.7% purity was readily produced in the second step while a majority of the impurities were precipitated in the first step. The two-step ammoniation was near completion despite a non-equilibrium reaction. However, rapid ammoniation favored the crystallization of ammonium fluosilicate. A sharp pH change occurred between 1.5 and 2.5 NH₃/H₂SiF₆ molar ratios, indicating the rapid disappearance of SiF ₆ ²⁻ ion from the solution.