Abstract: Tertiary alkylphosphorodichloridites, characterized by the formula: ##STR1## where R.sup.1, R.sup.2 and R.sup.3 may be alkyl having from about 1 to about 4 carbon atoms, aryl having from about 6 to about 8 carbon atoms, or aralkyl having from about 7 to about 10 carbon atoms, however, at least one of R.sup.1, R.sup.2 and R.sup.3 must be alkyl, as new compounds, and synthesis thereof by reacting, at temperatures of 0.degree. C. or less, a tertiary alcohol, a tertiary amine scavenger, and phosphorus trichloride, the PCl.sub.3 being employed in amounts in excess of the stoichiometric amount needed to react with the alcohol are provided. Both chlorides of the tertiary alkylphosphorodichloridites so produced may be replaced by RX.sup.- groups from alcohols (ROH), thiols (RSH), or amines (RR.sup.6 NH) in order that tri-substituted phosphite compounds of the formula: ##STR2## are produced. Disubstituted phosphorus acids of the formula: ##STR3## may be produced by heating the trisubstituted phosphite compounds.

Abstract: A process is provided for the desulfurization of residual oil by(a) separating the residual oil into a first and a second fraction;(b) reacting the first fraction with hydrogen over a hydrodesulfurization catalyst in a first reaction zone at hydrodesulfurization conditions such that a liquid effluent of lower sulfur content than the residual oil is obtained;(c) combining the hydrodesulfurization liquid effluent with the second residual oil fraction; and(d) reacting the resultant mixture over a hydrogenation/dehydrogenation catalyst in a second reaction zone at hydrogen transfer conditions.This process provides for desulfurization of residual oils at lower hydrogen consumptions than conventional processes.