A process for producing magnesia can include contacting CO.sub.2-containing emissions with a magnesium-containing material to produce magnesium carbonate; subjecting the magnesium carbonate to calcination to produce a CO.sub.2 by-product and magnesia; and recycling at least a portion of the CO.sub.2 by-product for contacting the magnesium-containing material to produce the magnesium carbonate. The magnesium-containing material can include mining residues, such as phyllosilicate or chrysotile mining residue, and the magnesium carbonate produced can include precipitated nesquehonite that is subjected to calcination to produce the magnesia.

An integrated catalyst can be used in an olefin disproportionation reaction. The integrated catalyst contains a plurality of different integrated active phases. The relative positions among different active phases remain substantially unchanged during the olefin disproportionation reaction. The effective distance between respective bisecting planes of two adjacent different active phases is 0.5-5 mm, preferably 1-3 mm.

Described is the use of a mineral comprising a metal carbonate fraction and a fuel fraction, such as oil shale or coal shale, in a calcination process. The disclosed process can advantageously result in carbon dioxide being removed from the atmosphere. Further, in the process, heat energy generated during calcination can be used to separate oxygen from air, so that the oxygen can be fed back into the system. Alternatively or in addition, heat energy may also be used to compress the gaseous carbon dioxide generated from the calcination process.

Described is the use of a mineral comprising a metal carbonate fraction and a fuel fraction, such as oil shale or coal shale, in a calcination process. The disclosed process can advantageously result in carbon dioxide being removed from the atmosphere. Further, in the process, heat energy generated during calcination can be used to separate oxygen from air, so that the oxygen can be fed back into the system. Alternatively or in addition, heat energy may also be used to compress the gaseous carbon dioxide generated from the calcination process.

The mixed powder is a mixed powder for an annealing separator containing MgO as a main agent, wherein the mixed powder contains Al and B, an Al content contained in the entire mixed powder is 0.0007 mass % or more and 0.050 mass % or less, a B content contained in the entire mixed powder is 0.005 mass % or more and 0.040 mass % or less, the B contains tri-coordinated boron, an average particle size of the mixed powder is 0.08 m or more and 9.0 m or less, and a formula (1) below is satisfied.

[00001]$\begin{array}{cc}0.06\left[\mathrm{Al}\right]/\left[{\mathrm{BO}}_3\right]<5.& \mathrm{Formula}\left(1\right)\end{array}$

In the formula (1), [Al] is an Al content (mass %) in the mixed powder, and [BO.sub.3] is a content (mass %) of the tri-coordinated boron in the mixed powder.

The mixed powder is a mixed powder for an annealing separator containing MgO as a main agent, wherein the mixed powder contains Al and B, an Al content contained in the entire mixed powder is 0.0007 mass % or more and 0.050 mass % or less, a B content contained in the entire mixed powder is 0.005 mass % or more and 0.040 mass % or less, the B contains tri-coordinated boron, an average particle size of the mixed powder is 0.08 m or more and 9.0 m or less, and a formula (1) below is satisfied.

[00001]$\begin{array}{cc}0.06\left[\mathrm{Al}\right]/\left[{\mathrm{BO}}_3\right]<5.& \mathrm{Formula}\left(1\right)\end{array}$

In the formula (1), [Al] is an Al content (mass %) in the mixed powder, and [BO.sub.3] is a content (mass %) of the tri-coordinated boron in the mixed powder.