摘要:
An improved process is described for the synthesis of hydroxylated aromatic compounds by means of the oxidation of an aromatic substrate with hydrogen, peroxide in an organic solvent, in the presence of synthetic zeolites, wherein the improvement consists in the fact that the organic solvent is selected from compounds having general formula (I) ##STR1## wherein: R.sub.1, R.sub.2, R.sub.3 and R.sub.4, the same or different, represent a hydrogen atom or an alkyl group with from 1 to 4 carbon atoms or from compounds having general formula (II) ##STR2## wherein R and R', the same or different, represent an alkyl radical with from 1 to 4 carbon atoms.
摘要:
Process for preparing porous spherical silica particles substantially consisting in emulsifying an acidic silica sol in a dispersing media, gelifying the microdrops of the sol in the emulsified state and submitting the resulting gel to thermal treatment in the presence of the emulsifier liquid and of sol gelation base.
摘要:
Process for the preparation of manufactured products based on vinylaromatic polymers with a predominantly syndiotactic structure which comprises:a) compressing the polymer in powder form in a mould at a pressure ranging from 0.1 to 500 MPa;b) sintering, under pressure, the compact powder at a temperature ranging from the glass transition temperature (Tg) of the polymer to the melting temperature (Tm);c) cooling the manufactured product to room temperature.
摘要:
Catalytic component for the copolymerization of ethylene with alpha-olefins having general formula (I): ##STR1## wherein: A is a cyclopentadienyl derivative having general formula (II) ##STR2## B is selected from: 1) any of the cyclopentadienyl derivatives A defined above2) a monofunctional cyclopentadienyl radical (F) selected from cyclopentadienyl, indenyl, fluorenyl and the relative alkyl, aryl, trialkylsilyl substituted derivatives;Q, a bridge between A and B, is a bifunctional radical.
摘要:
The preparation of objects, in particular optical components and/or devices, is described using, as precursors of optical materials, amorphous monolithic aerogels for high-precision mechanical machining.
摘要:
Process for the production of expandable particles of styrene polymers, having improved processability characteristics, which comprises:i) producing expandable particles of styrene polymers containing from 2 to 20% of an expanding agent incorporated;ii) covering these particles with an antistatic agent in a quantity of less than 1% by weight;iii) vigorously frictioning the particles in a mixing apparatus in order to heat their surface, in a short time, by simple mechanical friction;iv) discharging the particles thus treated from the mixing apparatus.
摘要:
A description follows of catalysts of the metallocene type which can be used in the (co)polymerization of alpha-olefins, particularly in the preparation of elastomeric copolymers of ethylene.
摘要:
Process for the preparation of caprolactam by the catalytic rearrangement of cyclohexanone oxime in which a vapour phase oxime is contacting a catalyst selected from an essentially amorphous, micro-mesoporous silica-alumina having a molar ratio SiO.sub.2 /Al.sub.2 O.sub.3 of 30 to 5000, a surface area of at least 500 m.sup.2 /g and a total pore volume of 0.3 to 1.3 ml/g.
摘要翻译:通过环己酮肟的催化重排制备己内酰胺的方法,其中气相肟与选自摩尔比SiO 2 / Al 2 O 3的基本上无定形的微介孔二氧化硅 - 氧化铝的催化剂接触,催化剂肟的表面积 至少为500m 2 / g,总孔体积为0.3〜1.3ml / g。
摘要:
A process is described for the preparation of polycarbonate polyether polyols characterized in that dimethylcarbonate (DMC) and one or more polyether diols are reacted at a ratio DMC/polyether diols of between 0.5 and 1.35, at a temperature of between 130.degree. and 175.degree. C. and in the presence of a catalyst consisting of an oxide, a carbonate or an alcoholate of a metal of the first or second group or a salt or organometallic compound of a metal belonging to the third or fourth or fifth group at a concentration of between 0.0001 and 0.01%.
摘要:
Process for the preparation of crystalline vinylaromatic polymers with a high degree of syndiotacticity which comprises polymerizing vinylaromatic monomers in the presence of a catalytic system essentially consisting of: a) a complex of titanium selected from those having the general formula: (CpR.sub.1 R.sub.2 R.sub.3 R.sub.4 R.sub.5)TiX.sub.3 (I) wherein the groups R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 represent a hydrogen atom or C.sub.1 -C.sub.10 alkyl groups; X represents a hydrogen atom, a halogen such as chlorine, a C.sub.1 -C.sub.10 alkyl or oxyalkyl radical or a C.sub.6 -C.sub.12 oxyaryl radical; b) an alkylaluminoxane; and c) an organic derivative of tin; characterized in that the alkylaluminoxane is methylaluminoxane (MAO) treated at 20.degree.-80.degree. C. under vacuum for 1-100 hours and the organic derivative of tin is tin tetraphenyl.