Abstract: Emissions of pollutants from diesel engines are reduced by a combination of mechanical devices and fuel additives. In one series of embodiments, diesel emissions of NO.sub.x and particulates are reduced, simultaneously with gaseous hydrocarbons and carbon monoxide, by the combined use of exhaust gas recirculation or engine timing modification, with a particulate trap and a platinum group metal catalyst composition. In another embodiment, a multi-metal catalyst composition, comprising a combination of a platinum metal catalyst composition and at least one auxiliary catalyst metal composition, especially cerium or copper, is employed to provide catalyst metal to the exhaust system including a diesel trap to lower the balance point of the particulate trap (the temperature at which the rate of trap loading equals the rate of regeneration) while also lowering the emissions of carbon monoxide and unburned hydrocarbons. Data for platinum, copper and cerium catalysts establishes effective amounts.

Abstract: The invention presented involves a method for reducing emissions from or increasing the utilizable energy of fuel for powering diesel, gasoline or gasohol internal combustion engines, the method comprising admixing with the fuel an additive which comprises a fuel-soluble, nonionic, organometallic platinum group metal coordination composition which is a) resistant to breakdown under ambient temperatures; b) does not contain a disadvantageous amount of phosphorus, arsenic, antimony or halides; and c) has a partition ratio sufficient to maintain preferential solubility in the fuel.

Abstract: The tendency of aqueous solutions of urea and other NH-containing compositions to force instability of hardness factors has been found to be detrimental to processes and apparatus employing them. The reliability of these processes and apparatus is improved by the inclusion of hardness-suppressing compositions, which preferably include both a water-soluble polymer and a phosphonate. In particular, agricultural and NO.sub.x -reducing applications are improved, especially for solutions containing urea hydrolysis products and the salts of them.

Abstract: The tendency of aqueous solutions of urea and other NH-containing compositions to force instability of hardness factors has been found to be detrimental to processes and apparatus employing them. The reliability of these processes and apparatus is improved by the inclusion of hardness-suppressing compositions, which preferably include both a water-soluble polymer and a phosphonate. In particular, agricultural and NO.sub.x -reducing applications are improved, especially for solutions containing urea hydrolysis products and the salts of them.

Abstract: The invention presented relates to a method for reducing the emission of nitrogen oxides from a diesel engine without significant loss of fuel efficiency and without significant increases in carbon monoxide and hydrocarbon emissions. The method involves preparing a diesel engine such that the injection timing thereof is set at a point sufficient to obtain reductions in the nitrogen oxides emissions from the engine; and firing the diesel engine with a diesel fuel having admixed therein an additive which comprises a fuel soluble organometallic platinum group metal coordination composition.

Abstract: The invention presented involves a method for regenerating, replacing or treating the catalyst in a hydroprocessing reactor, the method comprising admixing with the feedstock, recycle stream or hydrogen stream of the reactor an additive which comprises a nonionic, organometallic platinum group metal coordination composition which is a) resistant to breakdown under ambient temperatures; b) capable of breakdown at temperatures existing in the vicinity of the catalyst; and c) does not contain a disadvantageous amount of phosphorus, arsenic, sulfur, antimony or halides.

Abstract: The invention presented is a process for reducing the nitrogen oxides concentration in the effluent from the combustion of a carbonaceous fuel. The inventive process comprises introducing into the effluent an oxygenated treatment agent which includes an oxygenated hydrocarbon under conditions effective to oxidize nitric oxide in the effluent to nitrogen dioxide and to produce ammonia; and contacting the effluent with an aqueous absorbing solution having a component capable of causing nitrogen dioxide to be absorbed into the solution.

Abstract: The invention presented is a method for catalyzing fuel for powering internal combustion engines. The method comprises admixing with fuel an additive composition comprising at least one fuel-soluble platinum group metal compound in an amount effective to supply from 0.01 to 1.0 parts per million of platinum group metal per part of fuel.