Two low-rank coals with high sulfur contents (Gediz subbituminous coal:  7.6 wt % S:dry basis. Cayirhan lignite:  5.7 wt% S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions ...

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Direct Liquefaction of High-Sulfur Coals: Effects of the Catalyst, the Solvent, and the Mineral Matter

A vast majority of refineries uses alumina supported Co/Ni–Mo/W catalysts in their hydrotreating units. As several Ni compounds are classified as carcinogens category 1A or 1B and some soluble Co compounds are classified as carcinogens category 1B and toxic to reproduction category 1B, catalyst manufacturers are required to look for suitable substitutes with a less severe hazard profile under the existing workplace legislation. There is extensive literature on alternatives to using Co and Ni in hydrotreating catalysts. Several compositions were reported to have high activities in various hydrotreating reactions. However, in reality, the options are limited as many alternative compositions are either very expensive, are not available in sufficient amounts for commercial use, or are known to be toxic. Most noble metal compositions proposed in the literature are several orders of magnitude more expensive than normal hydrotreating catalysts. Other compositions that are acceptable from the cost point of view do not show sufficient activity. This is illustrated by a series of ultra-low sulfur diesel (ULSD) and VGO FCC-pretreat tests. These tests use alumina supported single transition metals as well as combinations of first row transition metals with Mo or W. All catalysts tested have much lower activities than the commercial catalysts. The consequences of using such low active catalysts in existing refinery units are also discussed. To achieve the same product quality and cycle length a catalyst with half the activity of a reference catalyst requires a 50% reduction in space velocity, which is infeasible for virtually every refinery. The refiner can either significantly increase reactor temperature or invest in additional reactors. Either way, the additional refining costs will increase the fuel price paid by the consumer at the pump and have a major negative impact on the competitiveness of many European refineries.

Economic and technical impacts of replacing Co and Ni promotion in hydrotreating catalysts

Catalytic hydrocracking of 4-(1-naphthylmethyl)bibenzyl (NMBB) predominantly yielded naphthalene and 4-methylbibenzyl. Various iron compounds were examined as catalyst precursors. Sulfur addition to most catalyst precursors led to substantially higher catalyst activity and higher conversion. NMBB was also treated with sulfur in the absence of iron compounds, in concentrations of 1.2-3.4 wt %, corresponding to the conditions present in reactions with added iron compounds. Increasing sulfur concentrations led to higher NMBB conversions. Furthermore, sulfur had a permanent effect on the reactor walls. A black sulfide layer formed on the surface which could not be removed mechanically. The supposed noncatalytic reactions done in the same reactor but after experiments with added sulfur showed higher conversions than comparable experiments done in new reactors. This wall catalytic effect can be reduced by treating the sulfided reactors with hydrochloric acid. The results of this work demonstrate the significant effect of sulfur addition and sulfur-induced residual wall effects on carbon-carbon bond cleavage and hydrogenation of aromatics.

Hydrotreatment of 4-(1-naphthylmethyl)bibenzyl in the presence of iron catalysts and sulfur

Sulfiding behavior of iron based coal liquefaction catalyst

First-stage direct liquefaction of a subbituminous coal with oil-soluble metal naphthenates as dispersed catalyst precursors

Results are presented from a study of the preparation and characterization of Wyodak subbituminous coal impregnated with iron and iron-molybdenum salts by the incipient wetness (IW) technique. X-ray photoelectron spectroscopy (XPS) was used to examine the surface composition and chemistry of coals impregnated with 0.7-2.0 wt% Fe and 500-1000 ppmw Mo. Various salts were used in preparing the impregnated coals including ferric nitrate, ferric sulfate, ferrous sulfate, and ammonium molybdate. The surface concentration of Fe increased as the amount of added Fe increased, with higher concentrations being observed for the nitrateimpregnated coals. The anions of the impregnating salts were readily removed from the samples that were treated with ammonium hydroxide solution

Hengfei Ni

Papers

Surface characterization and liquefaction of iron- and molybdenum-impregnated subbituminous coal

Catalyst performance in resid containing recycle solvents