Carbon Supported Alkaline Catalysts for Guerbet Coupling of Bioethanol

Bioethanol valorization to butanol by continuous heterogeneous catalytic self-alkylation provides an option for the fuel industry. Dimerization of ethanol (E) was studied over activated carbon supported metal loaded and metal-free alkaline catalysts using a flow-through tube microreactor, applying WHSVE of 0.20-2.0 gE/h gcat. , 21 bar total pressure and 275-400°C reaction temperature. Activated carbon (AC) was impregnated with various alkaline salts as the catalysts of the aldol reaction. Different basicity of the investigated catalysts resulted in differing catalytic activities. Butanol was the product of highest yield. Longer chain primary aliphatic alcohols, having even number of carbon atoms were also obtained with yield decreasing significantly with increasing chain length

Csekély makropórusos diffúziós ellenállással rendelkező zeolit adszorbensek és katalizátorok előállítása tágpórusú természetes hordozók felhasználásával = Preparation of supported zeolite bodies of low macroporous diffusional resistance in natural macrocavities

Egyes növényi szervek 700 oC-n nitrogén áramban történő elszenesítésével olyan egységes makropórus rendszerű hordozók állnak rendelkezésünkre, amelyek zeolit adszorbensek és katalizátorok új, hatékony formáinak megjelenését teszik lehetővé. A 0.7 cm élhosszúságú faszén kockákban 20-30-micro m átmérőjű és 1-3-micro m falvastagságú párhuzamos csatornák helyezkednek el. E csatornák belső felületének hidrofób jellege salétromsavas oxidatív kezeléssel csökkenthető. Ezt követően e kapillárisokat a szintézis géllel feltöltve hidrotermális körülmények között hajtjuk végre a zeolit kristályok képzését. A faszén felületén, oxidatív úton, a funkciós csoportok számát megnövelve valamint kedvező szintézis körülményeket alkalmazva, minden az ipari gyakorlatban fontosabb szerepet játszó zeolit típus esetében, olyan nanokristályok hozhatóak létre, amelyekből teljesen összefüggő zeolit rétegeket, kérget tudtunk kialakítani a faszenek makropórusrendszerének belső felületén. A zeolit réteg minőségét, tisztaságát, vastagságát, sűrűségét és az azt alkotó kristályok alakját és méretét a szintézis körülményei, és az azt megelőzően a gélben a kristály gócok képződését megszabó öregítés illetve beoltás határozta meg. A faszénben lévő kapillárisok falainak összefüggő zeolit kéreggel való bevonása során a csatornák belseje szabad maradt az anyagszállítás számára, így olyan, a zeolit/szén kompozit anyagok jöttek létre, amelyek gyors adszorbensek és katalizátorok létrehozását teszik lehetővé. | Biotemplating with carbonized wood is a novel way of zeolite adsorbent and catalyst production, with uniform, hierarchically ordered macro and micropore structure having low diffusional resistances against mass transport of adsorptives, reactants and products around the zeolite crystallites. Wood cubes of 1-cm size edges were carbonized at 700 oC in nitrogen flow. The obtained charcoal cubes contain parallel channels of 20-30-micro m diameter separated by about 1-3-micro m thick carbon walls. The hydrophobic character of the channel walls was effectively reduced using oxidative treatment with nitric acid. Following saturation with zeolite synthesis solution the carbon cubes were exposed to hydrothermal conditions. Small zeolite crystallites of all important types used in the industry can be obtained forming a continuous layer on the inner surface of the carbon honeycomb channels by increasing the concentration of polar functional groups on the surface of the virtually unimodal macroporous carbon honeycomb and by selecting the right conditions of zeolite synthesis. The morphology, purity, thickness and density of the zeolite layer was controlled by varying the synthesis conditions, ageing and seeding the synthesis gel. The microcrystals fully cover the surface of the macropores in the charcoal and leave the channels open for rapid mass transport forming advantageous zeolite/carbon composite for the purpose of applications as fast adsorbents and catalysts

Non-precious Metal Catalysts for Acetic Acid Reduction

Acetic acid (AA) hydroconversion was studied over various monometallic (Fe, Co, Ni, Cu, Zn, Pt) and bimetallic (doped with In as second, guest metal) catalysts loaded on a highly mesoporous, fumed silica support. The transformations were investigated in a fixed bed, flow-through reactor in temperature range of 240-380°C using hydrogen flow at 21bar total pressure. The catalyst precursors were activated in H2 flow at 21bar and 450°C as routine pre-treatment. Catalytic performances of the studied metal catalysts have nothing in common. Activities and the yields of main products contrast strikingly. Diversity of catalytic behaviour reflects the complexity of the surface reaction network. Contrary to the highly ethanol selective Co or Cu forms, over Ni catalyst mainly methane was produced. Indium doping can completely eliminate the hydrodecarbonylation activity and turn to the consecutive reduction route resulting in high ethanol yield. Metallic phases of different peculiarities can offer promising contacts for upgrading various oxygenates obtainable from biomass degradation

Indium an efficient co-catalyst in novel Cu or Ni catalysts for selective reduction of biomass derived fatty acids to alcohols, in Indium: Properties, Technological Applications and Health Issues

Supported copper or especially nickel catalysts are very important for hydrogenation of various organic compounds in the practice. Activity, selectivity and stability can be greatly improved using co-catalysts: e.g. chromium compounds with Cu (Adkins catalyst for fatty alcohol production) or molybdenum compounds with Ni (for hydrodesulfurization [HDS], hydrodeoxygenation [HDO], hydrodenitrogenation [HDN], etc. catalysts in petroleum refining. Recently, we discovered novel highly efficient bimetallic supported catalysts which were exceedingly active and selective in the hydrodeoxygenation (HDO) of octanoic acid to octanol at moderate pressure and temperature in addition very effective in reduction of acetic acid to ethanol. The catalysts contained indium as co-catalyst and a metal of high hydrogenation activity, such as, copper or nickel, on various support. A significant synergism can be observed when indium with another metal of hydrogenation activity is applied. Appearance of Cu2In or Ni2In phases, intermetallic compounds on the surface of metal particles results in significant increase of desired hydrogenation activity, i.e., in stepwise hydrogenation of carboxylic acids stopped at alcohol formation and in inhibiting hydrogenations when hydrodecarbonylation of carboxylic acids (loss of one carbon atom) and hydrogenolysis of hydrocarbon products (loss of further carbon atoms) proceed. Moreover, in presence of mobile indium atoms or of indium containing nano clusters mono- or bimolecular alcohol dehydration capability of the support is selectively poisoned. In order to have more information about the role of indium, experiments are carried out using quite different hydrogenation metals, Cu and Ni. Hydrogenation experiments are carried out with long chain fatty acid like octanoic acid for production of octyl alcohol and short chain acetic acid (produced in large amounts from biomass) for production of ethyl alcohol, ethyl acetate or acetaldehyde. The main question is how the co-catalyst second metal of moderate hydrogenation activity as gallium, cadmium, tin, but first of all indium, modify the activity of the supported hydrogenation metal and the surface properties of the support

Cu and Cu2In nanoparticles supported on amorphised zeolites for the selective reduction of biomass derived carboxylic acids to alcohols

Octanoic acid (OA) was used as reactant with medium chain length to model the aliphatic carboxylic acids which can be produced by catalytic, thermochemical or biological degradation of biomass. A flow through reactor was applied at 21 bar total pressure (in general at 20 bar hydrogen and 1 bar octanoic acid partial pressures) and 330-380 °C. Cu A-, X- and Y-zeolite based catalysts were pretreated in hydrogen flow at 450 °C. During reduction/dehydration A- and X-zeolite structures collapsed and aluminosilicate supported copper catalysts were formed, which contain copper nanoparticles in high dispersion. The catalyst samples were modified by In2O3 co-catalyst. Fatty acid conversion activity of amorphized zeolite supported Cu catalysts and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Appearance of metallic indium can effectively rein in the step by step catalytic reduction at alkanol formation previous to dehydration of alcohols to alkenes and ethers