Abstract: Two or more parallel waveguide lasers of different effective length are coupled together by their evanescent waves such that the composite structure functions as a single cavity having a longitudinal mode with resonances related to the resonances of the separate cavities. A very strong selection of the composite operating frequency, and suppression of most or all of the other longitudinal modes, with frequency tuning of the composite structure (both continuously and by mode hopping), can be accomplished by varying the relative currents supplied to each laser. Upon holding one cavity at one current level for a selected operating point and shifting the other, bistable operation can be achieved.

Abstract: A novel process, and the articles of manufacture, or compositions, formed thereby, wherein a Group II-A metal, or compound thereof, can be ion-exchanged onto coal, and thereafter a Group I metal physically admixed or otherwise incorporated therewith, so that the composition can be pyrolyzed, and gasified, to form a high-BTU, intermediate-BTU or synthesis fuel gas. Suitably, the Group II metal, or alkaline earth metal, can be directly ion-exchanged onto a low rank coal, without necessity of any pretreatment, by contact with a basic solution of a Group II-A metal compound since, of course, low rank coals contain natural ion-exchange sites.

Abstract: Carbonaceous solids are contacted in the presence of water with potassium sulfate and a calcium compound selected from the group consisting of calcium oxide, calcium hydroxide, and calcium carbonate thereby producing treated carbonaceous solids which are then gasified. The calcium compound apparently activates the relatively noncatalytic potassium sulfate thereby producing a substantial catalytic effect on the gasification reactions.

Abstract: In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles primarily in the form of water-soluble alkali metal sulphites and bisulphites by treating the particles with a solution of sulfurous acid. During the treating process the water-insoluble alkali metal compounds in the alkali metal residues are converted into water-soluble alkali metal sulphites and bisulphites, which have been found to be catalytically active.

Abstract: A carbonaceous feed material, a potassium compound having a relatively poor catalytic activity as compared to that of potassium carbonate, and a sodium or lithium salt are introduced into a gasification reactor. The carbonaceous material is then gasified in the presence of the added potassium and sodium or lithium constituents. The added sodium or lithium salt apparently activates the relatively noncatalytic potassium compound thereby producing a substantial catalytic effect on the gasification reactions. In general, activation of the noncatalytic potassium compound will take place when the sodium or lithium compound introduced into the reactor is either a salt of a weak acid or a salt of a strong acid that is converted to a sodium or lithium salt of a weak acid in the reactor at gasification conditions.

Abstract: A process wherein Group I-A or Group II-A metals, or both, can be ion-exchanged onto coal, especially a high rank coal, notably a subbituminous or bituminous coal, to produce a highly reactive carbonaceous feed for use in gasification reactions, especially to produce high-BTU fuel gases, but also intermediate-BTU or synthesis gas. The coal is treated by contact with an alkaline solution of an admixture of compounds, inclusive of a soluble alkali metal salt and an excess of an alkaline earth metal hydroxide, each of which interacts one with the other to form an alkali metal hydroxide, and an insoluble alkaline earth metal salt precipitate. The coal is treated in a single step by contact with the solution within which both the Group I-A and II-A metal compounds are dispersed, or dissolved.

Abstract: Coal is liquefied by treatment with a hydrogen-donor solvent and gaseous hydrogen, a heavy bottoms product boiling primarily in excess of about 1000.degree. F. is recovered, and this bottoms product is then pyrolyzed with fresh coal to produce surprisingly high yields of liquid product. The coke formed during the pyrolysis step may be gasified to generate hydrogen for use in the liquefaction operation and additional gas which can be employed as a fuel or upgraded for other uses.

Abstract: Heavy bottoms produced by the liquefaction of coal or similar carbonaceous solids are converted into more valuable products by adding an alkaline earth metal compound to the bottoms in a concentration sufficient to give, following pyrolysis of the bottoms, an alkaline earth metal-to-carbon atomic ratio of from about 0.005:1 to about 0.1:1; pyrolyzing the bottoms at a temperature of from about 900.degree. to about 1600.degree. F. to produce gases, hydrocarbon liquids and coke or char containing added alkaline earth metal constituents; and thereafter gasifying the char with steam.

Abstract: A method for the preparation of and pretreatment of coal, which coal will not cake when subjected to standard coal conversion processes, which method comprises the steps of electrophilically aromatically substituting the coal yielding alkylated or acylated products thereby.

Abstract: Flue gas is desulfurized by absorbing it onto a selective absorbent-catalytic material. The absorbed SO.sub.2 is recovered by contacting it in a desorption cycle with a reducing desorption gas. In one embodiment, multiple absorbent beds are employed and alternate absorption-desorption cycles are used in each of the multiple beds with the flue gas and the desorption gas used alternately. The sulfur oxide is recovered in concentrated form in the desorption gas stream and is then utilized as feed in a conventional sulfuric acid plant yielding concentrated sulfuric acid.