A method of etching a semiconductor substrate is described, the method comprising the steps of applying a paste containing an etchant to the substrate, and carrying out a thermal processing step to etch a part or a layer of the substrate where the paste has been applied. The etchant paste is preferably a caustic etching paste. The etchant paste may be applied selectively to a major surface of the substrate to form a pattern of applied paste. For example, the paste may be applied by a printing method, such as screen-printing. The method may be used to produce solar cells.

Semiconductor etching paste and the use thereof for localized etching of semiconductor substrates

A metal-working oil composition comprises as essential components thereof (a) one or more lube-oil components selected from the group consisting of oils, fats, mineral oils and fatty acid esters; and (b) one or more compounds selected from the group consisting of acidic phosphoric acid salts of aliphatic, alicyclic and aromatic amines each of which has 4 to 22 carbon atoms and quaternary ammonium salts formed from aliphatic or aromatic amines, each of which has 4 to 22 carbon atoms, and acidic phosphoric acids; and (c) a non-ionic surfactant. Incorporation of a specific amine compound together with a non-ionic surfactant permits, owing to the protective colloidal function of the compounds, stable dispersion of the lube-oil component as large droplets in water and hence the resulting dispersion enjoys good circulation stability and withstands severe machining conditions.

Metal-working oil composition

A method and apparatus for continuously and rapidly hydrating a polymer-based fracturing fluid. The invention is based upon the efficient application of high shear energy in order to increase the rate of hydration of the polymer. The invention includes the timing of the application of shear energy, the amount of shear energy applied and the manner in which it is applied. Specifically, the high shear energy is preferably not applied until at least 45 seconds after the mixing of a polymer slurry with a base liquid. Preferably, at least 2 hydraulic horsepower/barrel/minute of shear energy is applied to the mixture. Additionally, the mixture is recycled to maximize the benefits of application of high shear energy.

Method and apparatus for rapid and continuous hydration of polymer-based fracturing fluids

A hydrogen sorbent composition comprising a lanthanum pentanickel sorbent and a thermoplastic elastomer binder is disclosed. Also disclosed is the use of the composition in storing hydrogen and in the purification of hydrogen-containing streams.

Hydrogen sorbent composition and its use

Acrylic acid or methacrylic acid is purified by (a) subjecting a mixture comprising the acrylic acid or methacrylic acid to a sharply defined separation process essentially in the absence of an organic solvent, with the composition of the phase in which the acrylic acid or methacrylic acid accumulates remaining essentially constant when the composition of the other phases participating in the mass transfer changes, then taking off this phase and (b) subjecting at least a part of the remaining phase from stage(a) to a less sharply defined separation process and (c) feeding one of the phases formed in stage (b) to the sharply defined separation process in stage (a). In addition, the invention provides a process for preparing acrylic acid or methacrylic acid which includes the abovementioned purification process.

Purification of acrylic acid and methacrylic acid

A process is disclosed for converting polyacrylamide gel into dilute aqueous solutions suitable for use in secondary oil recovery. Polyacrylamide gel is initially converted into a slurry of small gel particles in water from which forms a homogeneous solution concentrate which is then readily diluted to give the final drive fluid without any significant polymer degradation. The process may additionally be adapted to the drilling site or to other on site operations requiring polyacrylamide solutions such as water treating, mining or paper making.

Preparation of aqueous polyacrylamide solutions for enhanced oil recovery

To separate aqueous and organic components of a mixture of isobutyric acid, water and methacrylic acid, the mixture is initially separated by salting out by means of a water soluble electrolyte e.g. sodium sulfate, which causes separation of aqueous and organic phases. Residuals in each phase are distilled off as a low-boiling mixed distillate resembling an azeotropic mixture which is returned for repeated separation by salting-out. Organics are further separated by fractional distillation.

Separation of components from a reaction product mixture of water isobutyric acid and methacrylic acid by phase separation and distillations

There is provided a process for preparing ethylene glycol by adding about 1 mole of water, from about 0.350 to 0.490 mole of oxygen and an aqueous solution of a catalytic iodine-containing compound selected from the group consisting of iodine, hydrogen iodide, ethylene diiodide and iodoethanol to a first reaction zone, introducing about 1 mole of ethylene and about 0.010 to 0.150 mole of oxygen to a second reaction zone, the amount of oxygen in both zones being equal to about 0.5 mole, withdrawing ethylene from the second reaction from overheads and introducing the same into the said first reaction zone, withdrawing from the first reaction zone a mixture of relatively high boiling organic iodides, iodine and ethylene glycol, introducing the latter mixture into said second reaction zone while maintaining said reaction zones at temperatures ranging from between 75*C. and 175*C. and pressures ranging from between 50 psi and 1,000 psi in each of said reaction zones, withdrawing a mixture of low boiling iodides and ethylene glycol as bottoms from the second reaction zone, subjecting the latter to distillation at a temperature of from 50*C. to 190*C. and under subatmospheric pressure ranging from about 1 mm. Hg. to about 700 mm. Hg., withdrawing as an overhead low boiling iodine compounds which are recycled to the first reaction zone, and recovering as bottoms an ethylene glycol product of markedly improved purity substantially devoid of iodinecontaining catalyst.

Manufacture of glycols

Preparation of extruded catalysts and catalyst supports containing polyacrylamide

1,269,765. Hydrocarbon reforming catalysts. ENGELHARD MINERALS & CHEMICALS CORP. 20 March, 1970 [21 March, 1969], No. 13707/70. Heading B1E. [Also in Division C5] A hydrocarbon reforming catalyst comprising rhenium and a Group VIII noble metal, for example platinum, supported on calcined alumina is prepared by a process which comprises (i) forming an aqueous slurry of hydrated alumina, the slurry having dissolved therein a water-soluble compound of rhenium and a water-soluble compound of a Group VIII noble metal, (ii) optionally treating the slurry with a water-soluble ionic sulphiding agent, for example hydrogen sulphide or ammonium sulphide, in order to convert the Group VIII noble metal compound to the corresponding metal sulphide, (iii) drying the slurry at a temperature insufficient to cause substantial release of water of hydration from the hydrated alumina, for example at a temperature not greater than 500‹F, (iv) forming the dried slurry into particles, for example by tabletting or extruding, and (v) calcining the particles, for example at a temperature of from 600 to 1200‹F. The slurry may contain from 5 to 16 weight per cent of hydrated alumina calculated as Al 2 O 3 ; from 50 to 95 weight per cent of the alumina content of the slurry may be alumina trihydrate selected from bayerite, gibbsite and nordstrandite (randomite), the balance of the alumina content being alumina monohydrate (boehmite) and/or amorphous hydrous alumina. The slurry preferably contains the rhenium compound and the Group VIII noble metal compound in amounts to provide that from 0.1 to 2 weight per cent of the catalyst is rhenium, calculated as metal, and from 0.1 to 1 weight per cent of the catalyst is Group VIII noble metal, calculated as metal; it is preferred that the catalyst contains rhenium and Group VIII noble metal in a molar ratio of between 1:5 and 5:1. The slurry may be dried by drum drying, flash drying, spray drying or tunnel drying; the particles may be calcined in an inert atmosphere, for example nitrogen, an oxidizing atmosphere, for example dry air, or a reducing atmosphere, for example an atmosphere containing hydrogen. The catalyst also may comprise acidic support material, for example selected from silica-alumina and crystalline aluminosilicate (the latter having a silica to alumina molar ratio of at least 2.0; containing uniform pores having a size of between 6 and 15 Angstroms and optionally having been cation exchanged with ions selected from hydrogen, ammonium and rare earth metal ions), in an amount constituting up to 85 weight per cent of the catalyst, and/or halogen, for example fluorine and/or chlorine, which may be incorporated by treating the calcined particles with gaseous hydrogen chloride or with an aqueous solution containing hydrogen chloride or ammonium chloride. As exemplified, catalyst is prepared from a slurry comprising perrhenic acid (Example 1) or ammonium perrhenate (Example2), chloroplatinic acid and alumina having a dry solids composition of 38 weight per cent bayerite, 18 weight per cent gibbsite, 29 weight per cent nordstrandite, 13 weight per cent boehmite and 2 weight per cent amorphous hydrous alumina, the slurry optionally being sulphided by having added thereto an aqueous solution of hydrogen sulphide. Reference is made to Specification 1,269,764.

John M Witheford

Papers

Preparation of aqueous polyacrylamide solutions for enhanced oil recovery

Separation of components from a reaction product mixture of water isobutyric acid and methacrylic acid by phase separation and distillations

Manufacture of glycols

Preparation of extruded catalysts and catalyst supports containing polyacrylamide

Hydrocarbon reforming catalyst