Prof. Moti Herskowitz

Prof. Moti Herskowitz Profile

Professor


Department : Department of Chemical Engineering
Room : 403 (גג)
59 - בנין הנדסת חומרים והנדסת כימיה ע"ש פוסטר
Phone : 972-8-6472767
972-8-6472768
972-8-6461482
Email : herskow@bgumail.bgu.ac.il
Office Hours :  

Education

  • 1971-75 B.Sc. in Chemical Engineering, summa cum laude, BGU, Israel
  • 1975-76 M.Sc. in Chemical Engineering, University of California, Davis, USA
  • 1976-78 Ph.D. in Chemical Engineering, University of California, Davis, USA

Research Interests

  • advanced materials, applied heterogeneous catalysis, multiphase and fixed-bed reactors

Research Projects

  • High loading TiO2 and ZrO2 nanocrystals ensembles inside the mesopores of SBA-15: preparation, texture and stability
  • High-Performance Solid Mn-Ce Nano-Catalyst for Low Temperature Wet Oxidation of Organic Pollutants in Industrial Wastewater
  • Kinetic Experiments and Modeling of Complex deNOx System: Decane SCR of NOx in Gas Phase and over Iron MFI Type Zeolite Catalyst
  • Modeling and simulation of a smart catalytic converter for a lean burn engine
  • Evaluation of metal oxide phase assembling mode inside the nanotubular pores of mesostructured silica

Research Abstract

  • Alumina foam coated with nanostructured chromia aerogel -
  • efficient catalytic material for complete combustion of chlorinated VOC
  • The ?-Al2O3 ceramic foam fabricated into cylindrical pellets (D16 mm; L20 mm) with pore density 50 PPI, pore diameter 0.5 mm, surface area of 0.1 m2/g, solid density of 3.89 g/cm3 and bulk density 0.2 g/cm3 was coated with chromia aerogel having surface area of 630 m2/g and consisting of 1-2 nm CrOOH nanocrystals. The sol-gel derived CrOOH powder was dispersed in aqueous slurry of boehmite (AlOOH) at Cr/Al atomic ratio of 1, and this composite slurry was used for rotary (40 rpm) coating of the ceramic foam heated to 360-370 K. After calcination in air at 593 K, the surface of the ceramic foam was uniformly coated with a mechanically stable porous CrOOH-Al2O3 layer with a bimodal pore size distribution of 0.5÷1.0 and 3÷7 nm with equal pore volumes at every range. The layer thickness was varied in range of 15-80 µm corresponding to CrOOH loading of 4.5÷21.5 wt% with the total surface area of 42 – 100 m2/g.
  • The chromia-loaded foams were packed in a tubular SS reactor in a way excluding bypass of reaction mixture flow. The pressure drop on a one cylindrical pellet after coating the parent foam with a layer corresponding to 21.5 wt% CrOOH only increased from 6 to 8 mm H2O at the air flow of 15 Nl/min. At the same air flow the pressure drop on the equivalent volume of a packed bed consisting on 21 wt.% CrOOH (0.3 mm pellets) mixed with quartz particles of 0.3 mm reached 1500 mm H2O.
  • The conversion of 2-chloropropane (2-CP) as halogenated VOC was studied at 450-550 K, GHSV = 60000 h-1 and 2-CP concentration in air 1000 ppmv. The highest activity in 2-CP combustion was measured with the ceramic foam containing 7.7 wt.% CrOOH. Complete conversion of 2-CP to CO2/H2O/HCl with this catalyst was achieved at 550 K. At lower temperatures of 500 K, 90.1% conversion was measured and 34.9% at 450 K with high CO2 selectivity of 92.4 and 88.2%, respectively. Further increasing the thickness of coated CrOOH layer to the values corresponding to chromia loadings up to 21.5 wt% did not improve the catalysts performance due to diffusion limitations of the reaction rate inside the layer. This is the first example of complete catalytic combustion of 2-CP at low temperatures of ? 550 K. At these conditions the regular most active VOC combustion catalysts like V-W-Ti-O, Mn-Al-O, Mn-W-Al-O, Al-Si-O and others provide only dehydrochlorination of 2-CP to HCl and propylene.
  • High loading TiO2 and ZrO2 nanocrystals ensembles inside the mesopores of SBA-15: preparation, texture and stability
  • TiO2 (30-80 wt%) and ZrO2 (48-75 wt%) were inserted inside the pores of SBA-15 mesostructured silica host by chemical solution decomposition (CSD) or internal hydrolysis (IH) of the corresponding alkoxides. Both methods yielded composites with 85-94% TiO2 crystallinity (anatase). In case of ZrO2, CSD yielded >95% crystallinity (tetragonal phase), while IH gave an amorphous ZrOx-phase that does not crystallize up to 1073 K. The guest Ti(Zr)-oxide phases did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of TiO2/SBA-15 and ZrO2/SBA-15 (CSD) composites up to 1073 K did not change the nanocrystals structure and slightly increased the domain size derived from XRD data from 5.0-8.5 to 6-10 nm for TiO2 (IH and CSD) and from 4.5 to 6.5 nm for ZrO2 (CSD). After the same treatment the crystals domain size of bulk reference TiO2 increased to > 100 nm with full conversion to rutile polymorph and of reference bulk ZrO2 – to 20-25 nm with partial conversion to monoclinic modification. Thorough characterization of the texture, structure, location and dispersion by HRTEM, SAXS, EDS, SEM, XRD, N2-adsorption methods allowed evaluation of the assembling mode of TiO2 and ZrO2 inside SBA-15 nanotubes: amorphous layer, ensemble of small 4-5 nm crystals (TiO2-IH and ZrO2-CSD) or single large 8.5 nm crystals (TiO2-CSD).
  • High-Performance Solid Mn-Ce Nano-Catalyst for Low Temperature Wet Oxidation of Organic Pollutants in Industrial Wastewater
  • Manganese – Cerium oxide catalysts were reported as most efficient in catalytic wet oxidation (CWO) of organic pollutants in industrial wastewater. CWO of pollutants to nontoxic and biodegradable products requires relatively high temperature (>150?C) and pressure (>10 bar). Complete oxidation to carbon dioxide and water is normally achieved at significantly higher temperatures. Structure and texture of catalysts affect significantly their performance, as recently reported for the manganese-cerium oxide. A new method for preparation of novel nano-casted catalysts has just been presented using ordered mesoporous silica (OMS) such as MCM-48 and SBA-15. Furthermore, nano-wires of manganese oxide and cerium oxide were also prepared separately inside SBA-15. However, the oxides surface area was similar or lower than that prepared by simple precipitation.
  • A method applying a sol-gel procedure inside SBA-15 to prepare 1-3 nm biphasic CeO2-Mn2O3 nano-casted composites is reported in this note. The contact surface between the two Ce- and Mn-oxide phases, over a range of Ce/Mn ratios, was controlled by co-gelation of Mn- and Ce-hydroxides inside nano-tubular pores of meso-structured SBA-15. Thus, a homogeneous amorphous monolayer was formed, followed by the removal of the silica matrix after crystallization of the oxide phases at >950 K. The nano-casted material retained the integrity and shape of the parent silica matrix. The packing mode of the nano-crystal oxides, and consequently the inter-phase contact surface that determines the efficiency of the catalytic redox cycle, was controlled by the final drying conditions, yielding surface area of 50-350 m2/g.
  • Several catalysts prepared by this method were characterized by HR-TEM, XRD and BET. They were tested in CWO of 2,4,6-trichlorophenol (TCP) solution (100 ppm), using a trickle-bed reactor at 80 to 140?C, 10 bar of oxygen and 3 min residence time. TCP conversion ranged from 84% at 80?C to 100% at 120?C with a catalyst containing Ce/Mn=0.55 atomic ratio. Surprisingly, based on TOC measurements, all TCP converted was transformed to CO2. Such high combustion activity has never been reported. The catalyst was stable for more than 200h. Mn/Ce catalyst prepared by standard method did not display combustion activity.
  • Kinetic Experiments and Modeling of Complex deNOx System: Decane SCR of NOx in Gas Phase and over Iron MFI Type Zeolite Catalyst
  • The reduction of NOx in the gas phase (in NO-NO2-decane-water-O2 mixture) and over Fe-MFI type zeolite catalyst was extensively studied under wide range of temperatures, gas-space velocities and concentrations. Fe-MFI zeolite (Si/Al 12.5 and Fe/Al 0.31) was prepared by solid-state ion exchange. The decane-SCR-NO and -NO2 were carried out with a reaction mixture consisting of 1000 ppm NOx, 300 ppm C10H22, 6.0 % O2, 0 or 12.0 % H2O at GHSV values 15,000-60,000 h-1 and temperatures 150-450°C. Under the experimentally investigated reaction conditions, there was no N2 formation in the bulk gas phase. Water vapor had little effect on the N2 yield in decane-SCR-NOx. The kinetic description of the homogeneous system included reactions between NO2 and decane with formation of NO, CO and CO2 and a pseudo-compound "C3H6O1.8" lumping all oxygenated, olefinic and paraffinic hydrocarbon products. The heterogeneous system accounts for two distinct functions of the Fe-loaded zeolite catalyst: NO oxidation and SCR of NO2 with decane and C3H6O1.8 yielding N2, NO, CO and CO2. This kinetic description yielded a good fit of experimental data. The rates of heterogeneous reactions were higher than the rates of homogeneous reactions by 1-3 orders of magnitude. Among catalytic reactions, the NO formation out of NO2 was the fastest reaction, which is the main reason for the relatively low nitrogen yield (<40%). The NO oxidation function of the Fe-MFI catalyst is insufficient, while high oxidation rate is critical for improved N2 formation.
  • Modeling and simulation of a smart catalytic converter for a lean burn engine
  • An increased concern about automotive pollutions in the last 30 years has led to very stringent emission standards and introduction of aftertreatment systems. The common aftertreatment system is the three way catalyst (TWC) which simultaneously converts all three pollutants (hydrocarbons (HC), CO and NOx) to water, carbon dioxide and nitrogen. However, reduction of NOx emission on diesel engine with TWC is not possible since consumption of the reductant component (CO and HC) by surplus oxygen. Therefore, more sophisticated systems are required for diesel and lean burn engines.
  • The smart catalytic converter, proposed by Daimler Chrysler, consists of 4 units: Oxidation, NOx storage, on-board reluctant production and selective catalytic reduction (SCR) unit. The system functions in dual-mode operation – lean-burn or rich-burn modes. In the lean operation CO, HC and NO are oxidized to CO2, H2O and NO2 in oxidation unit. In the next stage, part of NOx is adsorbed on storage material, while other continues to SCR unit and is reduced to N2. For short period of rich mode, NOx is desorbed from storage unit and enables regeneration of the adsorbent. Then, NOx react with hydrogen (that emits from engine at rich mode) to form a reductant which is stored in SCR unit. This system is significantly different than other potential aftertreatment technologies and relies on intrinsic dynamic operation and synchronization of all units. It renders the unit integration and precise scheduling necessary to achieve the desired performance. Thus, one of the critical stages in development of this converter is construction of the model that simulates the system. None of the models developed for other aftertreatment technologies required the degree of sophistication needed in this system. In this research, platform capable to simulate the dynamic behavior of several connected units in the aftertreatment system is designed to perform comparison of different materials performance, analysis of data, control development, system design and optimization.
  • Evaluation of metal oxide phase assembling mode inside the nanotubular pores of mesostructured silica
  • The assembling mode of transition metal oxides and metallic guest phases (GP) embedded in nanotubular pores of ordered mesostructured silicas (OMS) hosts was evaluated based on N2 adsorption-desorption data. The corresponding isotherms were measured for sample sets of composite materials MoO3/Al-MCM-41, WO3/SBA-15, TiO2/SBA-15, ZrO2/SBA-15, NiO/SBA-15 and Nio/SBA-15 with GP loadings in the range of 20-80 wt.%. The materials were also characterized by XRD, HRTEM and local/total EDS. It was shown that a combination of composite surface area values normalized per gram of OMS with pore size distribution (PSD) derived from the adsorption or desorption branch of the isotherm distinguishes the ensemble of small nanoparticles with a size of less than an OMS mesopore diameter and single nanoparticles of a size comparable with OMS mesopore diameter. It also discerns amorphous layer at the surface of OMS pore walls from the ensemble of amorphous nanoparticles. At high GP loadings the PSD derived from the adsorption branch of the N2-adsorption isotherm more reliably reflects the filling of OMS mesopores with crystalline or amorphous guest nanoparticles.

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