Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction. [Quarterly] technical progress report, April--June 1993

Abstract

In this quarter, progress has been made in the following two aspects: (1) effects of drying and mild oxidation on conversion and product distribution during non-catalytic and catalytic liquefaction of a Montana subbituminous coal (DECS-9); and (2) effects of solvent and catalyst on conversion and structural changes of a Texas subbituminous coal (DECS-1). Influence of drying and mild oxidation on catalytic and non-catalytic liquefaction (at 350C for 30 min with 6.9 MPa (cold) H{sub 2} was studied using Wyodak subbituminous coal. For non-catalytic runs, fresh raw coal gave higher conversion and higher oil yield than both the vacuum- and air-dried coals, regardless of the solvent. Compared to the vacuum-dried coal, the coal dried in air in 100C for 2 h gave a better conversion in the presence of either a hydrogen donor tetralin or a non-donor 1-methylnaphthalene (1-MN) solvent. Catalytic runs were performed using in-situ generated molybdenum sulfide catalyst from ammonium tetrathiomolybdate (ATTM) precursor impregnated on either raw coal or predried coal samples. The solvent-free runs using ATTM loaded on the raw coal gave higher conversion and higher oil yield than loading ATTM on vacuum- or air-dried coal. In the presence of either tetralin or 1-MN, however, the runs usingmore » ATTM loaded on air-dried coal afford better conversions and oil yields as compared to the runs using vacuum-dried coal. Upon drying coal in air at 150C for 20 h, the conversion significantly decreased to a lower value than that of the vacuum-dried coal in the non-catalytic runs, and the same trend was observed in the runs of the dried coals loaded with ATTM. Physical, chemical, and surface chemical aspects of effects of drying and oxidation and the role of water are also discussed in the report.« less