TO MAKE HYDROPYROLYSIS A MORE ENERGY-EFFICIENT PROCESS FOR COAL LIQUEFACTION BY DEVELOPING ACTIVE DISPERSED CATALYSTS WHICH WILL SIGNIFICANTLY IMPROVE OIL YIELD AND QUALITY WHEN USED IN LOW CONCENTRATIONS.
An attempt has been made, firstly, to develop effective dispersed catalysts for hydropyrolysis which can be used in low concentrations to improve significantly tar yield and quality and, secondly, to understand the reaction mechanisms involved and the influence of coal structure and catalyst on tar yields and composition. A wide range of dispersed molybdenum catalysts in the concentration range of 0.003% to 1.0% (molybdenum, daf coal) were investigated with the aim of achieving as low a loading as possible. Iron catalysts received less attention due to their lower activities in hydropyrolysis compared to direct liquefaction. The noble transition metals, palladium and, to a lesser extent, rhodium, were used to help probe the reaction mechanisms involved and to demonstrate the advantages of using ion exchange rather than impregnation for catalyst preparation. Hydrogenation tests were conducted on some of the most effective catalysts. A broad cross section of coals and some maceral concentrates were tested in the fixed bed hydropyrolysis apparatus to determine the effect of coal structure on conversions.
To further elucidate the role of the catalyst and the mechanisms involved, volatile release profiles were compared using online analysis, the extent of desulphurisation was investigated, and hydropyrolysis and batchwise hydrogenation oils were characterized, with the distributions of biomarker alkane compounds proving to be particularly sensitive to catalytic effects.
THIS IS A TWO YEAR CO-OPERATIVE PROJECT INVOLVING THE UNIVERSITIES OF STRATHCLYDE AND BRISTOL WITH A CONTRIBUTION FROM BERGBAU FORSCHUNG. THE POTENTIAL OF HYDROPYROLYSIS AS A ROUTE FOR COAL LIQUEFACTION HAS NOT BEEN FULLY REALISED BECAUSE OIL YIELDS ARE RELATIVELY LOW UNLESS EXTREMELY HIGH PRESSURES ARE USED. HOWEVER, DISPERSED SULPHIDED MOLYBDENUM (MO) AND OTHER TRANSITION METAL-BASED CATALYSTS ENABLE OIL YIELDS AS HIGH AS 60 % DAF COAL TO BE ACHIEVED FOR BITUMINOUS COALS. A NUMBER OF NOVEL DISPERSED CATALYSTS (MO, PD, NI, RH AND FE) PREPARED FROM AQUEOUS AND ORGANIC SOLUTIONS WITH METAL CONCENTRATIONS AS LOW AS 100 PPM (DAF COAL) WILL BE INVESTIGATED. FIXED-BED HYDROPYROLYSIS TESTS AT STRATHCLYDE WILL BE SUPPLEMENTED BY TESTS IN A HEATED GRID REACTOR AT BERGBAU FORSCHUNG. A SCHEMATIC OF THE TWO-STAGE FIXED-BED DISTILLATES AND A TYPICAL GC ANALYSIS OF SUCH A PRODUCT ARE SHOWN IN THE GENERATION OF SOLUBLE MATERIAL (I.E. TAR PRECURSORS) DURING THE EARLY STAGES OF HYDROPYROLYSIS, LOW-TEMPERATURE HYDROGENATION EXPERIMENTS WILL BE CONDUCTED AT BRISTOL. EXTENSIVE PRODUCT CHARACTERISATION AND THE USE OF DEUTERIUM GAS AND MACERAL CONCENTRATES WILL HELP TO ELUCIDATE THE BOND CLEAVAGE REACTIONS INVOLVED.