Zdeněk Vít

Effect of phosphorus on the surface state of alumina-supported nickelmolybdenum catalysts for hydrodesulphurization

Abstract The influence of concentration and method of phosphorus introduction in the alumina-supported nickel—molybdenum catalysts on the surface properties and catalytic activity in thiophene hydrodesulphurization (HDS) have been investigated. As a result of a strong interaction between phosphorus and support aluminium phosphates are formed. Molybdenum compounds, among them iso- and heteropoly compounds, are formed on the surface of Al 2 O 3 irrespective of the presence of phosphorus. The promoting effect of phosphorus is expressed in optimization of the phase composition of the catalyst and a decrease in coke formation. A 1 wt.-% ensures the optimum composition of the polymolybdate surface structures and their homogeneous distribution.

Comparison of carbon- and alumina-supported Mo, CoMo and NiMo catalysts in parallel hydrodenitrogenation and hydrodesulphurization

Abstract The effect of support (alumina, active carbon) and promoter (Co, Ni) on activity and selectivity of Mo catalysts was compared in parallel hydrodenitrogenation-hydrodesulphurization (HDNHDS) of pyridine and thiophene at 320 °C and 2 MPa of hydrogen pressure. Two commercial CoMo/alumina and NiMo/alumina catalysts were included for comparison. The undesirable formation of piperidine was much lower on carbon-supported and unpromoted Mo catalyst than on alumina-supported and Co- or Ni-promoted Mo catalyst. Irrespective of the type of support, the presence of Co or Ni accelerated mainly the HDS reaction; the unpromoted Mo catalysts had therefore better HDN/HDS selectivity than the CoMo and NiMo catalysts.

Comparison of carbon and alumina supported nickel—molybdenum sulphide catalysts in parallel hydrodenitrogenation and hydrodesulphurisation

Abstract The catalytic properties of Ni—Mo/C and Ni—Mo/Al 2 O 3 sulphide catalysts were compared in the hydrodesulphurisation of thiophene and in parallel hydrodesulphurisation of thiophene and hydrodenitrogenation of pyridine. The carbon support used was based on carbon black. The special features of carbon-supported catalysts are their high resistance during the hydrodesulphurisation activity to poisoning by pyridine, high hydrodenitrogenation activity and high hydrodesulphurisation/hydrodenitrogenation selectivity.

Carbon supported Ni-Mo catalyst: high hydrodenitrogenation activity and low inhibition of hydrodesulphurization by hydrodenitrogenation

Abstract Four active carbon supported Ni-Mo sulphide catalysts and alumina supported Ni-Mo catalyst Shell 324 were tested in concurrent hydrodesulphurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine at 2 MPa and 280 °C. The various Ni-Mo/C catalysts differed in the pretreatment of the support which was extracted by various solvents before impregnation. The data were also compared with previous results on the same catalysts in HDS of thiophene in the absence of pyridine. The HDN activity of the Ni-Mo/C catalysts was three to five times higher than that of the reference Shell catalyst. The inhibition of HDS by HDN was much lower on the Ni-Mo/C than on the Ni-Mo/alumina samples. Consequently, HDS activity of the Ni-Mo/C catalysts in the presence of pyridine was very high, the best catalyst being 14 times more active than the alumina supported sample.

DETERMINATION OF THE SURFACE HYDROXY GROUPS ON ALUMINA AND SILICA-ALUMINA CATALYSTS BY DIMETHYLZINC

The earlier proposed pulse flow method for the determination of surface OH groups based on the reaction of gaseous dimethylzinc tetrahydrofuranate with active hydrogen was applied to alumina and silica-alumina catalysts. The concentrations of OH groups found by this method are in a good agreement with the published data, obtained by deuterium exchange and gravimetry.AbstractМетод пульсирующей, струи, ранее предложенный для определения поверхностных групп OH, основанный на реакции газового тетрагидрофураната диметилцинка с активным водородом, был применен для катализаторов окиси алюминиь и окиси кремния-окиси алюминия. Концентрации групп OH, найденные этим методом, находятся в хорошем согласии с литературнымн данными, полученными с помощыо дейного обмена и гравиме трией.

Determination of basic sites on the surface of metal oxide catalysts by desorption of benzoic acid

A method has been developed for the determination of the concentration of basic sites on white and deeply colored solid porous materials, which is based on the displacement of adsorbed benzoic acid by acetic acid. The determination is rapid and gives results comparable with those obrained by the titration with benzoic acid using thymolphthalein as indicator.AbstractБыл разработан метод определения конщентрации основных центров на белых и глубоко окрашенных твердых пористых материалах. Метод основан на замещении адсорбированной бензойной кислоты уксусной кислотой. Определение является быстрым и дает результаты, подовные резупьтатам, полученным титрованием бензоиной киспоты, используя тимолфталеин в качестве индикатоа.

Determination of hydroxy and sulfhydryl groups on the surface of sulfided hydrorefining catalysts

Previously proposed methods for the determination of surface hydroxy groups of oxides, based on the reaction of dimethylzinc tetrahydrofuranate with active hydrogen atoms, and for the determination of surface sulfhydryl groups of sulfides, based on the reaction with silver ions, were applied to simultaneous determination of OH and SH groups present on the surface of a sulfided hydrorefining CoMo/Al2O3 catalyst.AbstractРанее предложенные методы определения поверхностных гидроксильных групп окислов, основанные на взаимодействии метилового цинка тетрагидрофураната с активными атомами водорода, и поверхностных сульфгидрильных групп сульфидов, основанные на взаимодействии с ионами серебра, были использованы для одновременного определения групп OH и SH, присутствующих на поверхности сульфидированных катализаторов гидрорафинирования-CoMo/Al2O3.

DETERMINATION OF THE SURFACE ACIDITY OF SOLID CATALYSTS

A novel method has been developed for determining the surface acidity of white, as well as deeply colored porous solids. The method, which was tested on Al2O3, SiO2−MgO−Al2O3 and Fe2O3 catalysts, is based on the adsorption of pyridine or benzylamine on acidic sites and subsequent displacement of the adsorbed bases by n-butylamine. A linear correlation was found between the concentration of acidic sites on Al2O3 and Fe2O3 catalysts and their activity in the dehydration oftert-butyl alcohol.AbstractПредлагается новый метод определения поверхностной кинлотности белых, а также темных порошков. Метод, проверенный на катализаторах Al2O3, SiO2−MgO−Al2O3 и Fe2O3, был основан на адсорбции пиридина или бензиламина на кислотных центрах и соответствующем замещении адсорбированных оснований на н-бутиламин. Была установлена линейная зависимость между концентрацией кислотных центров катализаторов Al2O3 и Fe2O3 и их активностью в дегидратации тр-бутилового спирта.

Comparison of the acid strength of solid catalysts

The catalytic activity of some solid acidic catalysts was tested in the depolymerization of paraldehyde. It was found that the activities of sulfonated ion exchange resin and mounted phosphotungstic acid strongly exceed the activity of silica-alumina and other oxide catalysts. By means of Brönsted relationship, the differences in HO of the surfaces were estimated.AbstractКаталитическую активность некоторых твердых кислых катализаторов тестировали в деполимеризации паральдегида. Найдено, что активность сульфонированных ионо-обменных смол и нанесенных фосфовольфрамовых кислот значительно превышает активность силика-алюминиевых и других окисных катализаторов. С помошью уравнения Брёнстэда определили разницы в HO поверхности.

Determination of acid sites on carbon surface

Pyridine chemisorbed on acid sites of active carbon was displaced by n-butylamine and the displaced amount was measured spectrophotometrically. This amount, supposed to be proportional to the surface concentration of carboxy groups, depends on the chemical pretreatment of active carbon.AbstractПиридин, хемосорбированный на кислых центрах активного угля, был измерен спектрофотометрически. Это количество, которое должно быть пропорционально концентрации карбоксильных групп на поверхности, зависит от предварительной химической обработки активного угля.